Blazing and grazing: influences of fire and bison on tallgrass prairie stream water quality - Larson, D.M.; Grudzinski, B.P.; W. K. Dodds; Daniels, M.D.; Skibbe, A.M.; Anthony Joern (Freshwater Science, 2013)
Fire and grazers (such as Bison bison) were historically among the most important agents for maintaining and managing tallgrass prairie, but we know little about their influences on water-quality dynamics in streams. We analyzed 2 y of data on total suspended solids (TSS), total N (TN), and total P (TP) (3 samples per week per stream during flow) in 3 prairie streams with fire and bison grazing treatments at Konza Prairie Biological Station, Kansas (USA), to assess whether fire and bison increase the concentrations of these water-quality variables. We quantified the spatial and temporal locations of bison (∼0.21 animal units/ha) with Global Positioning System collars and documented bison trails, paw patches, wallows, and naturally exposed sediment patches within riparian buffers. Three weeks post-fire, TN and TP decreased (t-test, p < 0.001), but TSS did not change. Bison spent <6% of their time within 10 m of the streams, increased the amount of exposed sediment in the riparian areas, and avoided wooded mainstem branches of stream (χ2 test, p < 0.001). Temporal trends suggest that low discharge or increased bison density in the stream may increase TSS and TP during the summer months. Our results indicate a weak connection between TSS and nutrients with bison access to streams over our 2-y study and indicate that low TSS and nutrients characterize tallgrass prairie streams with fire and moderate bison densities relative to surrounding land uses.
Keywords: Bison bison; Bos bison; burning; Grasslands; grazers; prescribed fire; streams; tallgrass prairie; total nitrogen; total phosphorus; total suspended solids

Community and ecosystem changes in tallgrass prairie restorations: the effects of population source and diversity - Klopf, R.P. (Southern Illinois University, 2013)
The overall objective of this study was to quantify the effects of dominant grass propagule source (i.e., cultivar vs. non-cultivar) and seeded diversity of propagules on community structure and ecosystem function during prairie restoration. Two field experiments, and two chronosequences were used to investigate this main objective. The two field experiments were established at the same latitude separated by 620 km (corresponding to a precipitation gradient from eastern Kansas to western Illinois), and consisted of a split plot design, with dominant grass source as the whole-plot factor (2 levels) and seeded dominance of grasses as the subplot factor (5 levels). Percent cover of each species in each treatment combination was quantified during the first five years of restoration. Total plant species richness and diversity were not adversely affected by cultivars in Kansas or Illinois. The effect of the dominant grass population source on the cover of focal grasses, planted species, and volunteer species were contingent upon location. By the fifth year of restoration, diversity and richness were greatest, and cover of volunteer species was lowest in the low grass dominance (i.e., high diversity) treatment. ANPP, as well as total, microbial, and mineralizable pools of C and N were measured to quantify ecosystem function in these two field experiments. Changes in ecosystem function in Kansas and Illinois were primarily driven by time and regional abiotic differences, not propagule source or seeded diversity. The effect of plant species diversity on ecosystem function was further investigated at a landscape scale by developing and sampling two chronosequences of high (HDC; n=20) and low diversity (LDC; n=15) prairies spanning over two decades of restoration in northwestern Illinois. In general most metrics of ecosystem function in both chronosequences moved towards levels measured in remnant prairies. While the constituent prairies of the HDC had higher species richness, diversity, and more rapidly increasing root biomass than the fields of the LDC, recovery of other important ecosystem functions including aboveground net primary productivity, total, microbial, and mineralizable soil C, and soil aggregate mean weighted diameter were achieved equally well with either high or low diversity prairie plantings.

Comparing surface and mid-tropospheric CO2 concentrations from central U.S. grasslands - Cochran, F.V.; N. Brunsell; Mechem, D.B. (entropy, 2013)
Comparisons of eddy covariance (EC) tower measurements of CO2 concentration with mid-tropospheric observations from the Atmospheric Infrared Sounder (AIRS) allow for evaluation of the rising global signal of this greenhouse gas in relation to surface carbon dynamics. Using an information theory approach combining relative entropy and wavelet multi-resolution analysis, this study has explored correlations and divergences between mid-tropospheric and surface CO2 concentrations in grasslands of northeastern Kansas. Results show that surface CO2 measurements at the Kansas Field Station (KFS) and the Konza Prairie Biological Stations 1B (KZU) and 4B (K4B) with different land-cover types correlate well with mid-tropospheric CO2 in this region at the 512-day timescale between 2007 and 2010. Relative entropy further reveals that AIRS observations are indicative of surface CO2 concentrations for all land-cover types on monthly (32-day) and longer timescales. AIRS observations are also similar to CO2 concentrations at shorter timescales at sites KFS and K4B experiencing woody encroachment, though these results require further investigation. Differences in species composition and microclimate add to the variability of surface concentrations compared with mid-tropospheric observations.
Keywords: Atmospheric Infrared Sounder; Eddy covariance; information theory; Konza Prairie; relative entropy; wavelets

Coordinated distributed experiments: an emerging tool for testing global hypotheses in ecology and environmental science - Fraser, L.H.; Henry, H.A.; Carlyle, C.N.; White, S.R.; Beierkuhnlein, C.; Cahill, J.F.; Casper, B.B.; Cleland, E.E.; Scott. L. Collins; Dukes, J.S.; Alan K. Knapp; Lind, E.; et al. (Frontiers in Ecology and the Environment, 2013)
There is a growing realization among scientists and policy makers that an increased understanding of today's environmental issues requires international collaboration and data synthesis. Meta-analyses have served this role in ecology for more than a decade, but the different experimental methodologies researchers use can limit the strength of the meta-analytic approach. Considering the global nature of many environmental issues, a new collaborative approach, which we call coordinated distributed experiments (CDEs), is needed that will control for both spatial and temporal scale, and that encompasses large geographic ranges. Ecological CDEs, involving standardized, controlled protocols, have the potential to advance our understanding of general principles in ecology and environmental science.

Correlations between genetic and species diversity: effects of resource quantity and heterogeneity - M.L. Avolio; M.D. Smith (Journal of Vegetation Science, 2013)
Questions It is hypothesized that species and genetic diversity are correlated because niche differentiation among species and genotypes is either affected by the same processes (positive) or each level restricts the amount of diversity in the other (negative). Although many studies have observed both positive and negative relationships, others have found no correlation between the two diversity measures. Are measures of species (richness, diversity and evenness) and genetic diversity correlated, and how does resource (soil moisture, light, nitrogen and phosphorus) quantities and heterogeneity affect both levels of diversity? Location Intact tallgrass prairie at Konza Prairie Biological Station, northeast Kansas, US. Methods We investigate the correlation between plant species and genetic diversity in a long-term precipitation manipulation experiment – the Rainfall Manipulation Plots (RaMPs) – located in intact tallgrass prairie as well as adjacent non-manipulated prairie. The RaMPs experiment has been imposing ambient and more variable precipitation regimes (a 50% increase in timing between rainfall events without changing total rainfall amount) during the growing season since 1998, resulting in reduced mean soil moisture and increased soil moisture variability. Thus, the RaMPs and non-manipulated prairie plots capture a range of soil moisture amounts and variability. Genetic diversity (measured as genotype richness and genomic dissimilarity among individuals) was quantified for the dominant grass species, Andropogon gerardii, which has large impacts on plant community structure and ecosystem function. Results We found species and genetic diversity were not significantly correlated. Genotypic richness was negatively related to soil moisture variability, but measures of species diversity were not. In the non-manipulated plots only, we found generally negative relationships between resource quantity (light and nitrogen) and community diversity, and positive relationships between resource heterogeneity (CV of light) and community diversity. Conclusions Our results suggest that a lack of a positive or negative relationship between species and genetic diversity could be due to these two levels of diversity responding differently to the identity, quantity and heterogeneity of resources.
Keywords: Andropogon gerardii; C4 grass; dominant species; grassland; Resource heterogeneity; Resource quantity; Species genetic diversity correlation

Dietary selection and nutritional regulation in a common mixed-feeding insect herbivore - Jonas, J.L.; Anthony Joern (Experimentalis et Applicata Entomologia, 2013)
The geometric framework provides a way for understanding the multi-dimensional nutritional relationships between consumers and their food. We use this approach to further our understanding of the feeding and nutritional ecology of a ubiquitous mixed-feeding insect herbivore that consumes a variety of host plants spanning a wide range of nutritional composition. Our overall objective was to examine feeding decisions, resulting performance, and post-ingestive consequences in a common mixed-feeding insect herbivore, Melanoplus bivittatus (Say) (Orthoptera: Acrididae), when presented with paired diets differing in protein:carbohydrate (p:c) ratio. Intake p:c of M. bivittatus differed among all but two treatments and in many cases was farther than expected from the previously identified p:c intake target for this species. Despite this variability in intake of protein and carbohydrate, we found few effects of the diet treatments on performance or post-ingestive processing. However, our results suggest that when feeding on high-quality diets, nutrients consumed in excess may be stored rather than excreted.
Keywords: acrididae; carbohydrate; geometric framework; homeostasis; Melanoplus bivittatus; nutritional ecology; Orthoptera; protein

Dissolved black carbon in grassland streams: is there an effect of recent fire history? - Ding, Y.; Yamashita, Y.; W. K. Dodds; Jaffe, R. (Chemosphere, 2013)
While the existence of black carbon as part of dissolved organic matter (DOM) has been confirmed, quantitative determinations of dissolved black carbon (DBC) in freshwater ecosystem and information on factors controlling its concentration are scarce. In this study, stream surface water samples from a series of watersheds subject to different burn frequencies in Konza Prairie (Kansas, USA) were collected in order to determine if recent fire history has a noticeable effect on DBC concentration. The DBC levels detected ranged from 0.04 to 0.11 mg L−1, accounting for ca. 3.32 ± 0.51% of dissolved organic carbon (DOC). No correlation was found between DBC concentration and neither fire frequency nor time since last burn. We suggest that limited DBC flux is related to high burning efficiency, possibly greater export during periods of high discharge and/or the continuous export of DBC over long time scales. A linear correlation between DOC and DBC concentrations was observed, suggesting the export mechanisms determining DOC and DBC concentrations are likely coupled. The potential influence of fire history was less than the influence of other factors controlling the DOC and DBC dynamics in this ecosystem. Assuming similar conditions and processes apply in grasslands elsewhere, extrapolation to a global scale would suggest a global grasslands flux of DBC on the order of 0.14 Mt carbon year−1.
Keywords: BPCA; Dissolved black carbon; Dissolved organic carbon; Fire frequency; Grassland streams; Konza Prairie

Drivers of grassland community structure and ecosystem function: the role of biotic factors in determining the ecosystem response to alterations in resource availability - Kimberly J. La Pierre (Yale University, 2013)

Ecological mechanisms underlying arthropod species diversity in grasslands - Anthony Joern; Laws, A. (Annual Review of Entomology, 2013)
Arthropods are an important component of grassland systems, contributing significantly to biodiversity and ecosystem structure and function. Climate, fire, and grazing by large herbivores are important drivers in grasslands worldwide. Arthropod responses to these drivers are highly variable and clear patterns are difficult to find, but responses are largely indirect with respect to changes in resources, species interactions, habitat structure, and habitat heterogeneity resulting from interactions among fire, grazing, and climate. Here, we review these ecological mechanisms influencing grassland arthropod diversity. We summarize hypotheses describing species diversity at local and regional scales and then discuss specific factors that may affect arthropod diversity in grassland systems. These factors include direct and indirect effects of grazing, fire, and climate, species interactions, above- and belowground interactions, and landscape-level effects.

Ecological responses to climate extremes in a mesic grassland - Hoover, D.L. (Colorado State University, 2013)
Climate change threatens ecosystems through altered climate means and by increasing the frequency and intensity of extreme climatic events. Such events may have greater impacts on ecosystems than shifting means alone because they can push organisms beyond critical thresholds. Thus, there is an urgent need to assess the response of ecosystems to climate extremes as well as elucidate the mechanisms underlying the observed responses. My dissertation examined the ecological impacts of two years of experimentally imposed climate extremes (heat waves and drought) followed by a recovery year, on a mesic tallgrass prairie grassland ecosystem. The broad objectives of this research were (1) to assess the resistance and resilience of this ecosystem to the individual and combined effects of heat waves and drought, and (2) to identify the ecological mechanisms driving the responses and (3) to evaluate the sensitivities of key carbon cycling process to heat waves and drought. I measured a range of biotic responses to these treatments including: ecophysiology, community dynamics, primary production, and soil respiration in order to gain a comprehensive understanding how this ecosystem responds to such extremes. During the first year of the experiment, I examined the ecophysiological and productivity responses of the dominant C4 grasses to a growing season-long drought and a midsummer, two-week heat wave. Although differential sensitivities were apparent, the independent effects of drought dominated the ecological responses for both species, with only minor direct effects of heat were observed. However, the heat wave treatments had indirect effects via enhanced soil drying, making it difficult to separate the effects of the heat wave and precipitation treatments on biotic responses. Therefore in the second year of the experiment, I controlled for heat-induced water losses during the heat wave and examined the independent effects of heat on net photosynthesis in both grass species under contrasting soil moisture regimes. Under low soil moisture, heat had no effect on net photosynthesis, while increasing temperatures moderately reduced photosynthesis under high soil moisture. Next I examined the resistance and resilience in ecosystem function (aboveground primary production) of this tallgrass prairie to the two years of extreme treatments and for one subsequent recovery year. I observed high resistance to heat but not drought, as aboveground production dropped below historic levels during the second year of the drought. Despite this extreme ecological response, productivity fully recovered in just one year post-drought due to rapid demographic compensation by the dominant grass offsetting the loss of the dominant forb. Finally, I examined the response of soil respiration to heat and drought across the three years of the experiment. As with aboveground net primary production, soil respiration was more sensitive to drought than heat, but it was less sensitive overall to drought than production. There are three main conclusions from my dissertation research. First, this tallgrass prairie ecosystem has low resistance but high resilience to extreme short-term drought, which may be an important characteristic for long-term stability in ecosystems with histories of drought. Secondly, the two most abundant species governed both community and ecosystem-level dynamics across this three-year experiment, providing evidence for the central role of dominant species during these short-term events. Finally, my results suggest that three key carbon cycling processes in this mesic grassland - photosynthesis, plant productivity and soil respiration - are all significantly more sensitive to the independent effects of an extreme drought than heat waves and there were little to no combined effects of heat waves and drought. Overall, these results suggest that in a future with more frequent and extreme heat waves and drought, this mesic grassland will be most vulnerable to water stress, either directly through precipitation deficits or indirectly through warming-induced drying, while the direct ecological effects of midsummer heat waves will be minor.

Ecosystem characteristics of remnant, headwater tallgrass prairie streams - Larson, D.M.; W. K. Dodds; Jackson, K.E.; M.R. Whiles; Winders, K.R. (Journal of Environmental Quality, 2013)
North America has lost >95% of its native tallgrass prairie due to land conversion, making prairie streams one of the most endangered ecosystems. Research on the basic ecosystem characteristics of the remaining natural prairie streams will inform conservation and management. We examined the structure and function of headwater streams draining tallgrass prairie tracts at Osage Prairie in Missouri and the Konza Prairie Biological Station in Kansas and compared those values with literature values for streams draining agricultural watersheds in the region. We quantified physicochemical and biological characteristics for 2 yr. Streams at Osage and Konza were characterized by low nutrients and low suspended sediments (substantially lower than impacted sites in the region), slight heterotrophic status, and high temporal variability. Suspended sediments and nutrient concentrations were generally low in all prairie streams, but storms increased concentrations of both by 3- to 12-fold. Spring prescribed burns were followed by a slight increase in chlorophyll a and decreased nutrients, potentially due to greater light availability. Benthic macroinvertebrate communities at Osage showed seasonal patterns that were probably linked to variable hydrology. We found nine amphibian species using the Osage streams as habitat or breeding sites, but little usage at Konza was probably due to dry conditions and low discharge. Our study indicates that two remnant tallgrass prairie streams along a longitudinal gradient are fairly similar in terms of physicochemical features and have good water quality relative to agricultural watersheds but can differ considerably in macroinvertebrate and amphibian abundance.

Effects of sexual dimorphism and landscape composition on the trophic behavior of Greater Prairie-Chickens - Blanco-Fontao, B.; Sandercock, B.K.; Obeso, J.R.; McNew, L.B.; Quevedo, M. (PLoS ONE, 2013)
Partitioning of ecological niche is expected in lekking species that show marked sexual size dimorphism as a consequence of sex-specific ecological constraints. However, niche partitioning is uncertain in species with moderate sexual dimorphism. In addition, the ecological niche of a species may also be affected by landscape composition; particularly, agricultural fragmentation may greatly influence the trophic behavior of herbivores. We studied trophic niche variation in Greater Prairie-Chickens (Tympanuchus cupido), a grouse species that shows moderate sex-dimorphism. Greater Prairie-Chickens are native to tallgrass prairies of North America, although populations persist in less natural mosaics of cropland and native habitats. We used stable isotope analysis of carbon and nitrogen in blood, claws and feathers to assess seasonal differences in trophic niche breadth and individual specialization between male and female Greater Prairie-Chickens, and between birds living in continuous and fragmented landscapes. We found that females showed broader niches and higher individual specialization than males, especially in winter and autumn. However, differences between females and males were smaller in spring when birds converge at leks, suggesting that females and males may exhibit similar feeding behaviors during the lekking period. In addition, we found that birds living in native prairies showed greater annual trophic variability than conspecifics in agricultural mosaic landscapes. Native habitats may provide greater dietary diversity, resulting in greater diversity of feeding strategies.
Keywords: Blood; diet; Ecological niches; Ecosystems; Feathers; habitats; Mating behavior; Stable isotopes

Environmental and genetic variation in leaf anatomy among populations of Andropogon gerardii (Poaceae) along a precipitation gradient - Olsen, J.T.; Caudle, K.L.; Johnson, L.C.; S.G. Baer; Maricle, B. (American Journal of Botany, 2013)
• Premise of the study: Phenotypes of two Andropogon gerardii subspecies, big bluestem and sand bluestem, vary throughout the prairie ecosystem of North America. This study sought to determine the role of genetics and environment in driving adaptive variation of leaf structure in big bluestem and sand bluestem. • Methods: Four populations of big bluestem and one population of sand bluestem were planted in common gardens at four sites across a precipitation gradient from western Kansas to southern Illinois. Internal leaf structure and trichome density of A. gerardii were examined by light microscopy to separate genetic and environmentally controlled traits. Leaf thickness, midrib thickness, bulliform cells, interveinal distance, vein size, and trichome density were quantified. • Key results: At all planting sites, sand bluestem and the xeric population of A. gerardii had thicker leaves and fewer bulliform cells compared with mesic populations. Environment and genetic source population were both influential for leaf anatomy. Leaves from plants grown in mesic sites (Carbondale, Illinois and Manhattan, Kansas) had thicker midribs, larger veins, fewer trichomes, and a greater proportion of bulliform cells compared to plants grown in drier sites (Colby and Hays, Kansas). • Conclusions: Water availability has driven adaptive variation in leaf structure in populations of A. gerardii, particularly between sand bluestem and big bluestem. Genetically based differences in leaves of A. gerardii indicate adaptive variation and evolutionary forces differentiating sand bluestem from big bluestem. Environmental responses of A. gerardii leaves suggest an ability to adjust to drought, even in populations adapted to mesic home environments.
Keywords: adaptive variatio; big bluestem; bulliform cells; drought adaptation; ecotypes; Kranz anatomy; leaf structure; n Andropogon gerardii; population; sand bluestem

Environmental impacts of wind power development on the population biology of Greater Prairie-Chickens. U.S. Department of Energy, Final Project Report for Award DOE/EE0000526 (technical report) - Sandercock, B.K.; Wisely, S.M.; McNew, L.B.; Gregory, A.J.; Winder, V.L.; Hunt, L.M. (Final Project Report for Award DOE/EE0000526, 2013)

EO-1 Hyperion reflectance time series at calibration and validation sites: stability and sensitivity to seasonal dynamics - Campbell, P.P.K.; Middleton, E.M.; Thome, K.J.; Kokaly, R.F.; Huemmrich, K.F.; Lagomasino, D.; Novick, K.A.; N. Brunsell (IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2013)
This study evaluated Earth Observing 1 (EO-1) Hyperion reflectance time series at established calibration sites to assess the instrument stability and suitability for monitoring vegetation functional parameters. Our analysis using three pseudo-invariant calibration sites in North America indicated that the reflectance time series are devoid of apparent spectral trends and their stability consistently is within 2.5-5 percent throughout most of the spectral range spanning the 12+ year data record. Using three vegetated sites instrumented with eddy covariance towers, the Hyperion reflectance time series were evaluated for their ability to determine important variables of ecosystem function. A number of narrowband and derivative vegetation indices (VI) closely described the seasonal profiles in vegetation function and ecosystem carbon exchange (e.g., net and gross ecosystem productivity) in three very different ecosystems, including a hardwood forest and tallgrass prairie in North America, and a Miombo woodland in Africa. Our results demonstrate the potential for scaling the carbon flux tower measurements to local and regional landscape levels. The VIs with stronger relationships to the CO2 parameters were derived using continuous reflectance spectra and included wavelengths associated with chlorophyll content and/or chlorophyll fluorescence. Since these indices cannot be calculated from broadband multispectral instrument data, the opportunity to exploit these spectrometer-based VIs in the future will depend on the launch of satellites such as EnMAP and HyspIRI. This study highlights the practical utility of space-borne spectrometers for characterization of the spectral stability and uniformity of the calibration sites in support of sensor cross-comparisons, and demonstrates the potential of narrowband VIs to track and spatially extend ecosystem functional status as well as carbon processes measured at flux towers.
Keywords: calibration; geophysical techniques; remote sensing; vegetation

Estimating aboveground net primary productivity of the tallgrass prairie ecosystem of the Central Great Plains using AVHRR NDVI - An, N.; Price, K.P.; John M. Blair (International Journal of Remote Sensing, 2013)
Above-ground net primary productivity (ANPP) is indicative of an ecosystem's ability to capture solar energy and convert it to organic carbon (or biomass), which may be used by consumers or decomposers, or stored in the form of living and nonliving organic matter. Annual and interannual variation in ANPP is often linked to climate dynamics and anthropogenic influences, such as fertilization, irrigation, above-ground biomass harvest, and so on. The Central Great Plains grasslands occupy over 1.5 million km2 and are a primary resource for livestock production in North America. The tallgrass prairies are the most productive grasslands in this region, and the Flint Hills of North America represent the largest contiguous area of unploughed tallgrass prairie (1.6 million ha). Measurements of ANPP are of critical importance to the proper management and understanding of climatic and anthropogenic influences on tallgrass prairie. Yet, accurate, detailed, and systematic measurements of ANPP over large geographic regions do not exist for this ecosystem. For these reasons, this study was conducted to investigate the use of the normalized difference vegetation index (NDVI) to model ANPP of the tallgrass prairie. Many studies have established a positive relationship between the NDVI and ANPP, but the strength of this relationship is influenced by vegetation types and can vary significantly from year to year depending on land use and climatic conditions. The goal of this study was to develop a robust model using the Advanced Very High Resolution Radiometer (AVHRR) biweekly NDVI values to predict tallgrass ANPP. This study was conducted using ANPP measurements from a watershed within the Konza Prairie Biological Station (KPBS) as the primary study area, with additional measurements from the Rannells Flint Hills Prairie Preserve (RFHPP) and biennial ANPP measurements by Kansas State University (KSU) students from tallgrass areas near Manhattan, Kansas. Data from the primary study site covered the period of 1989–2005. The optimal period for estimating ANPP using AVHRR NDVI composite data sets was found to be late July. The Tallgrass ANPP Model (TAM) explained 54% (coefficient of determination, R 2 = 0.54, p < 0.001) of the year-to-year variation in ANPP. The creation of 1.0 km × 1.0 km resolution ANPP maps for a four-county (∼7000 ha) area for years 1989–2007 showed considerable variation in annual and interannual ANPP spatial patterns, suggesting complex interactions among factors influencing ANPP spatially and temporally.

Evidence of physiological decoupling from grassland ecosystem drivers by an encroaching woody shrub - Jesse B. Nippert; Ocheltree, T.W.; Orozco, G.L.; Z. Ratajczak; Ling, B.; Skibbe, A.M. (PLoS ONE, 2013)
Shrub encroachment of grasslands is a transformative ecological process by which native woody species increase in cover and frequency and replace the herbaceous community. Mechanisms of encroachment are typically assessed using temporal data or experimental manipulations, with few large spatial assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra-annual variability in leaf δ13C in Cornus drummondii across a grassland landscape with varying fire frequency, presence of large grazers and topographic variability. This assessment of changes in individual shrub physiology is the largest spatial and temporal assessment recorded to date. Despite a doubling of annual rainfall (in 2008 versus 2011), leaf δ13C was statistically similar among and within years from 2008-11 (range of −28 to −27‰). A topography*grazing interaction was present, with higher leaf δ13C in locations that typically have more bare soil and higher sensible heat in the growing season (upland topographic positions and grazed grasslands). Leaf δ13C from slopes varied among grazing contrasts, with upland and slope leaf δ13C more similar in ungrazed locations, while slopes and lowlands were more similar in grazed locations. In 2011, canopy greenness (normalized difference vegetation index – NDVI) was assessed at the centroid of individual shrubs using high-resolution hyperspectral imagery. Canopy greenness was highest mid-summer, likely reflecting temporal periods when C assimilation rates were highest. Similar to patterns seen in leaf δ13C, NDVI was highest in locations that typically experience lowest sensible heat (lowlands and ungrazed). The ability of Cornus drummondii to decouple leaf physiological responses from climate variability and fire frequency is a likely contributor to the increase in cover and frequency of this shrub species in mesic grassland and may be generalizable to other grasslands undergoing woody encroachment.
Keywords: Ecosystems; Grasslands; Grazing; Leaves; Plant physiology; Seasons; Shrubs; Water resources

The exaggerated begging behaviour of an obligate avian brood parasite is shared with a nonparasitic close relative - Rivers, J.W.; M.A. Blundell; Loughin, T.M.; Peer, B.D.; Rothstein, S.I. (Animal Behaviour, 2013)
Offspring signalling models predict that the begging displays of obligate brood parasites are more intense than nonparasitic species because parasitic young are never reared by their genetic parents and often compete against unrelated host young during development. The brown-headed cowbird, Molothrus ater, has been described as having exaggerated begging relative to nonparasitic species, but an effective test of this idea is lacking because previous studies have not controlled for evolutionary history while simultaneously standardizing rearing conditions. We quantified the begging intensity of cowbirds and the closely related, nonparasitic red-winged blackbird, Agelaius phoeniceus, when both species experienced identical rearing conditions in two distinct nest environments: reared alone by a small cowbird host, or reared with two host young by a moderate-sized cowbird host. Against theoretical predictions, we found that in both nest environments four components of the cowbird begging display were similar to (or less intense than) blackbird begging displays (i.e. latency to beg, begging score, call rate and call amplitude) when nestlings were tested across a gradient of short-term need. Our results provide the first experimental evidence that a closely related, yet nonparasitic, species shares an exaggerated begging display with a brood-parasitic species when reared under conditions typically experienced by parasitic offspring. We discuss three nonexclusive explanations for our findings: (1) relatedness among cowbird nestmates reduced cowbird begging intensity (kin selection hypothesis), (2) reduced body condition of blackbirds elevated their begging intensity (body condition hypothesis) and (3) intense competition in blackbird nest environments led to increased blackbird begging intensity (competitive environment hypothesis).
Keywords: Agelaius phoeniceus; begging; brood parasitism; brown-headed cowbird; Molothrus ater; offspring signalling; red-winged blackbird

Fungal community responses to discrete precipitation pulses under altered rainfall intervals - A. Jumpponen; Lydia H. Zeglin; David, M.; Prestat, E.; Brown, S.; Dvornik, J.; Lothamer, K.; Hettich, R.; Jansson, J.; C. W. Rice; Tringe, S.; Myrold, D.D. (2013)

Genetic diversity of a dominant C4 grass is altered with increased precipitation variability - M.L. Avolio; Beaulieu, J.; M.D. Smith (Oecologia, 2013)
Climate change has the potential to alter the genetic diversity of plant populations with consequences for community dynamics and ecosystem processes. Recent research focused on changes in climatic means has found evidence of decreased precipitation amounts reducing genetic diversity. However, increased variability in climatic regimes is also predicted with climate change, but the effects of this aspect of climate change on genetic diversity have yet to be investigated. After 10 years of experimentally increased intra-annual variability in growing season precipitation regimes, we report that the number of genotypes of the dominant C4 grass, Andropogon gerardii Vitman, has been significantly reduced in native tallgrass prairie compared with unmanipulated prairie. However, individuals showed a different pattern of genomic similarity with increased precipitation variability resulting in greater genome dissimilarity among individuals when compared to unmanipulated prairie. Further, we found that genomic dissimilarity was positively correlated with aboveground productivity in this system. The increased genomic dissimilarity among individuals in the altered treatment alongside evidence for a positive correlation of genomic dissimilarity with phenotypic variation suggests ecological sorting of genotypes may be occurring via niche differentiation. Overall, we found effects of more variable precipitation regimes on population-level genetic diversity were complex, emphasizing the need to look beyond genotype numbers for understanding the impacts of climate change on genetic diversity. Recognition that future climate change may alter aspects of genetic diversity in different ways suggests possible mechanisms by which plant populations may be able to retain a diversity of traits in the face of declining biodiversity.
Keywords: AFLP; Andropogon gerardii; Dice dissimilarity; dominant species; Genotypic structure

Genetic variation and mating success in managed American plains bison - Ungerer, M.C.; Weitekamp, C.A.; Anthony Joern; Towne, G.; J. M. Briggs (Journal of Heredity, 2013)
The American plains bison (Bison bison) was pushed to the brink of extinction in the late 1800s but has since rebounded. Less than 5% of animals currently exist in conservation herds that are critical for maintaining genetic variability. Here, we use 25 microsatellite loci to assess genetic diversity and patterns of mating success over a 3-year period in a managed conservation herd at Konza Prairie Biological Station, Kansas (total number of individuals genotyped = 587). Heterozygosity was comparable to and allelic diversity higher than that in 11 other wild and managed herds for which similar estimates are available. Parentage analyses revealed that males within the oldest age classes (5–7 years) sired >90% of calves over the study period, consistent with a polygynous breeding system. Asymmetries in siring success also were observed within age classes, with the same males enjoying high siring success over multiple seasons. Empirical results of paternity will facilitate future modeling and empirical efforts to determine how demographic factors, population size, and variation in siring success interact to determine the retention (or loss) of genetic diversity in natural and managed herds, thus allowing informed recommendations for management practices and conservation efforts of this symbolic North American species.

Genotypic diversity of a dominant C4 grass across a long-term fire frequency gradient - Chang, C.C.; M.D. Smith (Journal of Plant Ecology, 2013)
Aims and Methods Diversity-disturbance research has focused on community diversity, but disturbance frequency could impact diversity within species as well, with important consequences for community diversity and ecosystem function. We examined patterns of genetic diversity of a dominant grass species, Andropogon gerardii, in native North American tallgrass prairie sites located in eastern Kansas that have been subjected to a gradient of fire frequency treatments (burned every 1, 2, 4 or 20 years) since the 1970s. In addition, we were able to assess the relationships between genetic diversity of A. gerardii, species diversity and productivity across this range of fire frequencies. Important Findings We found no significant relationships between genetic diversity of A. gerardii at the local scale (1 m2 plot level) and disturbance frequency (burned 2 to 32 times over a 38-year period). However, at the site level (i.e. across all plots sampled within a site, ~100 m2) there were differences in genotype richness and composition, as well as genomic dissimilarity among individuals of A. gerardii. Genotype richness was greatest for the site burned at an intermediate (4-year) frequency and lowest for the infrequently (20-year) burned site. In addition, genotypes found in the frequently burned sites were more similar from each other than expected by random chance than those found in the infrequently burned sites. Genotype composition of A. gerardii was not significantly different between the frequently burned sites (annual vs. 2 year) but did differ between frequently burned and infrequently burned sites (1 and 2 year vs. 4 and 20 year, etc.). Together, these results suggest site-level ecological sorting of genotypes in intact prairie across a broad gradient of disturbance frequencies, likely driven by alterations in environmental conditions. Frequent fire promotes the abundance of dominant grass species, reduces plant community diversity and impacts ecosystem processes such as productivity. Our study suggests that genetic diversity within dominant grass species also may be affected by disturbance frequency, which could have important implications for how species are able to respond to disturbance.
Keywords: Andropogon gerardii; disturbance frequency; genetic relatedness; genetic-species diversity relationship; genotype richness; intermediate disturbance hypothesis; productivity; tallgrass prairie

Global diversity of drought tolerance and grassland climate-change resilience - Craine, J.M.; Ocheltree, T.W.; Jesse B. Nippert; Towne, E.G.; Skibbe, A.M.; Kembel, S.W.; Fargione, J.E. (Nature Climate Change, 2013)
Drought reduces plant productivity, induces widespread plant mortality and limits the geographic distribution of plant species1, 2, 3, 4, 5, 6, 7. As climates warm and precipitation patterns shift in the future8, 9, understanding the distribution of the diversity of plant drought tolerance is central to predicting future ecosystem function and resilience to climate change10, 11, 12. These questions are especially pressing for the world’s 11,000 grass species13, which dominate a large fraction of the terrestrial biosphere14, yet are poorly characterized with respect to responses to drought. Here, we show that physiological drought tolerance, which varied tenfold among 426 grass species, is well distributed both climatically and phylogenetically, suggesting most native grasslands are likely to contain a high diversity of drought tolerance. Consequently, local species may help maintain ecosystem functioning in response to changing drought regimes without requiring long-distance migrations of grass species. Furthermore, physiologically drought-tolerant species had higher rates of water and carbon dioxide exchange than intolerant species, indicating that severe droughts may generate legacies for ecosystem functioning. In all, our findings suggest that diverse grasslands throughout the globe have the potential to be resilient to drought in the face of climate change through the local expansion of drought-tolerant species.
Keywords: Climate-change ecology; Drought; Grassland ecology

Grass fires - an unlikely process to explain the magnetic properties of prairie soils - Roman, S.A.; Johnson, W.C.; Geiss, C.E. (Geophysical Journal International, 2013)
It has been proposed that grass fires affect the magnetic properties of soils by combining generally reducing soil conditions with elevated temperatures. To explore this supposition, we analysed surface and subsurface samples from loessic soils and compared their differences in magnetic properties as a function of fire intensity. Fire intensity was established based on types of burnt vegetation, which ranged from low-intensity fires in short-grass areas to high-intensity fires in tall-grass and forested areas. We measured low-field magnetic susceptibility (χ), a common proxy for the abundance of magnetic minerals, frequency-dependent susceptibility (χFD), a proxy for the presence of ultrafine-grained superparamagnetic minerals, and susceptibility of anhysteretic remanent magnetization (χARM), a magnetic parameter highly dependent on the presence of fine, single-domain magnetic particles. Although intense fires led to an increase in frequency-dependent susceptibility and low-field magnetic susceptibility, moderately intense fires did not produce significant changes in magnetic properties. Observed magnetic changes are limited to sites that were very heavily burnt in forest areas. Grass fires are therefore an unlikely mechanism to explain a measurable component of the magnetic enhancement in prairie soils.
Keywords: Environmental magnetism; North America; Rock and mineral magnetism

Grassland invasion by non-native grass species: ecological issues of multiple species at multiple trophic levels - Greer, M.J. (Oklahoma State University, 2013)
Invasion of native grasslands by non-native grasses is of great economic and ecologic concern. Non-native grasses have potential to alter ecosystem functions, habitat quality, disturbance regimes, and feedback loops. These alterations can have bottom-up or top-down effects that may negatively influence grasslands at multiple trophic levels. I conducted three integrated studies to assess non-native grass invasion: 1) on the competitive interactions between native vs. non-native grass species with community-level implications; 2) possible utilization of allelopathic biochemicals as an invasion mechanism; and 3) possible alterations in the small mammal communities with implications for ecosystem-level function. My first study indicated that both invasive and native species varied in mycorrhizal dependency along a continuum from obligately to facultatively dependent. Native species biomass production was consistently reduced when planted into 'away' soil, as compared to 'home' soil. Increased biomass production of native grasses was consistently observed following additions of native prairie soil to steam-pasteurized soil from the invaded sites, indicating invasive feedbacks may occur through alterations in biotic communities. My second study indicated that Bothriochloa spp. may gain a competitive advantage through the use of allelopathic biochemicals. However, it is unclear if these allelopathic effects directly hinder competitors, or indirectly hinder competitors through alterations of soil microbial communities. Determination of allelopathic biochemicals was not definitive. Data from my third study indicate that invasion of B. ischaemum into the native grasslands lowered all abundance metrics for deer mice (Peromyscus maniculatus), while increasing all abundance metrics for hispid cotton rats (Sigmodon hispidus), as compared to native grassland controls. Species-specific models show cotton rats select vegetation that supplies aerial predator avoidance and deer mice select habitat that increases foraging efficency. Alterations in these small mammal communities may have profound effects on ecosystem functioning. Our research indicates non-native grass invasion alters native communities on multiple trophic levels. I propose management practices for restoration may be most successful if determined on a species-specific and site-specific basis, as different species appear to use different mechanisms for successful invasion into native prairies.

Grassland restoration in a changing world: consequences of practices and variable environments - Carter, D.L. (Kansas State University, 2013)
The feasibility of restoration, which traditionally targets historical conditions, is questionable in the context of global change. To address this, my dissertation investigated (Chapter 2) the patterns of restoration establishment along a chronosequence of restored prairies with respect to nearby remnant prairies, (Chapters 3-4) responses of plant communities in restorations initiated using different methods (levels of species richness and sowing density) to drought, which is projected to increase in frequency, and (Chapters 5-6) the effects of propagule source and variation (mixing among sources) on restoration establishment and the generality of restoration outcomes across variable environments using reciprocal common gardens of multi-species restoration seedings. Chapter 2, published in Restoration Ecology, showed that restoration led to the recovery of desirable characteristics within several years, but restorations utilizing primarily fall-collected seeds likely diminished the representation of early phenology species, so biodiversity may be further enhanced by including early phenology species in seeding mixes. Chapters 3 and 4, published respectively in Ecological Applications and Applied Vegetation Science, examined the establishment of native plant communities after seeding and their responses to experimentally imposed drought. Both high seed mixture richness and high density seeding resulted in greater establishment of native, seeded species compared to low richness and low density treatments, and exotic species were less prevalent in high richness and high density treatments. However, we found little evidence of differential drought resistance, recovery, and resilience among treatments. This result coupled with increases in exotic species following drought suggest that other forms of active management may be needed to produce restored plant communities that are robust to climate change. Chapter 5 (published in Ecosphere) and Chapter 6 found that seed source affects individual species establishment, community structure, and productivity. However, there was no consistent advantage for any source, including local sources, across sites or species. This suggests that source effects on single species or effects observed at single locations should not be broadly generalized. Together, this dissertation shows that restoration can recover many characteristics of native prairies and that manipulation of seeding practices (seed mixture richness, seeding density, seed source) influence grassland establishment in terms of productivity, community structure, invasion, and the abundance and survival of individual species.
Keywords: chronosequence; Climate change; common garden; local adaptation; tallgrass

Grazing and drought in tallgrass prairie: the role of belowground bud banks in vegetation dynamics - VanderWeide, B.L. (Kansas State University, 2013)
Grazing and drought are instrumental in the development and maintenance of perennial grasslands. In this research I tested the belowground bud bank contribution to tallgrass prairie resistance and resilience when perturbed by grazing and drought. First, I tested the bud bank role in vegetation response to and recovery from severe drought (Chapter 2). I compared above- and belowground responses of experimentally droughted plots to ambient controls and irrigated plots during two years of severe drought and two years of recovery. I found that although aboveground net primary productivity declined 30-60% during drought, bud bank density and demography were insensitive to drought. These results suggest that grassland resistance and resilience when perturbed by drought may be mediated by stability of belowground bud banks. Second, I investigated vegetation and soil nutrient legacies following release from long-term grazing (Chapter 3). I documented a relatively rapid shift in aboveground vegetation within four years of grazer exclusion, with productivity, stem density, and diversity becoming relatively more similar to ungrazed than grazed prairie. The density and composition of the belowground bud bank and soil seed bank shifted more slowly, remaining more similar to grazed than ungrazed prairie. Responses of soil nutrients to removal of grazers varied, and in some cases was affected by recent fire history. These results demonstrate the contribution of belowground propagules to the maintenance of a diverse plant community both during grazing and after grazers are removed. Finally, I examined short-term vegetation responses to both drought and grazing (Chapter 4). Despite extreme drought and simulated grazing that reduced productivity and increased mortality of individual stems, the dominant C4 grasses maintained a stable bud bank. Aboveground net primary productivity and bud bank density of sedges and forbs, however, were reduced by both drought and grazing. This differential response of species to extreme drought and grazing led to shifts in community composition and species diversity over one growing season. Across drought and grazing treatments, live rhizome biomass was highly correlated with bud bank density and may be a useful, more easily measured index of bud bank density.
Keywords: Bud bank; Grazing; Drought; Resistance and resilience; Seed bank; tallgrass prairie

Habitat associations of stream fishes in a rare and declining ecosystem - Martin, E.; Whitney, J.E.; K. B. Gido (American Midland Naturalist, 2013)
Describing fish habitat associations and their relevance to conservation remains a central challenge in stream fish ecology. Unfortunately, there are limited opportunities to investigate these associations in unaltered systems and identify critical habitats used by native fishes. Investigation of fish habitat associations in tallgrass prairie is especially vital, owing to their widespread destruction. Our study aim was to identify habitat factors associated with the distribution and density of fishes in two protected tallgrass prairie stream watersheds in eastern Kansas: Kings Creek on the Konza Prairie Biological Station (KPBS) and Fox Creek on the Tallgrass Prairie National Preserve (TPNP). We sampled fishes and measured eight habitat variables at three sites on KPBS (2006–2011) and four sites on TPNP (2008–2011). Multiple regression suggested that species richness was positively associated with pool area (partial r  =  0.70) and discharge (partial r  =  0.50) in Fox Creek (df  =  15, Adj. R2  =  0.60, P < 0.001). In Kings Creek, species richness was only associated with pool area (df  =  17, R2  =  0.44, P < 0.001). Redundancy analyses showed common prairie fish species exhibit ontogenetic habitat associations, partitioning adults in deep and juveniles in shallow pools. Strong species area relationships in these minimally altered systems indicates large volume habitats have greater species richness, suggesting water diversions or extractions that reduce habitat are likely to cause declines in native biodiversity.

High-throughput amplicon sequencing of rRNA genes requires a copy number correction to accurately reflect the effects of management practices on soil nematode community structure - Darby, D.J.; Todd, T.C.; Herman, M.A. (Molecular Ecology, 2013)
Nematodes are abundant consumers in grassland soils, but more sensitive and specific methods of enumeration are needed to improve our understanding of how different nematode species affect, and are affected by, ecosystem processes. High-throughput amplicon sequencing is used to enumerate microbial and invertebrate communities at a high level of taxonomic resolution, but the method requires validation against traditional specimen-based morphological identifications. To investigate the consistency between these approaches, we enumerated nematodes from a 25-year field experiment using both morphological and molecular identification techniques in order to determine the long-term effects of annual burning and nitrogen enrichment on soil nematode communities. Family-level frequencies based on amplicon sequencing were not initially consistent with specimen-based counts, but correction for differences in rRNA gene copy number using a genetic algorithm improved quantitative accuracy. Multivariate analysis of corrected sequence-based abundances of nematode families was consistent with, but not identical to, analysis of specimen-based counts. In both cases, herbivores, fungivores and predator/omnivores generally were more abundant in burned than nonburned plots, while bacterivores generally were more abundant in nonburned or nitrogen-enriched plots. Discriminate analysis of sequence-based abundances identified putative indicator species representing each trophic group. We conclude that high-throughput amplicon sequencing can be a valuable method for characterizing nematode communities at high taxonomic resolution as long as rRNA gene copy number variation is accounted for and accurate sequence databases are available.

Identifying the water sources consumed by bison: implications for large mammalian grazers worldwide - Jesse B. Nippert; Culbertson, T.S.F.; Orozco, G.L.; Ocheltree, T.W.; Helliker, B.R. (Ecosphere, 2013)
The sources of drinking water consumed by grazers vary over time and may be highly selective, similar to choices in diet. Water sources consumed by large grazers in natural populations are not typically measured directly. Instead, consumption is inferred based on animal proximity to water sources. Here, we analysed the stable isotopic signature of water (δ18O and δD) extracted from fecal samples from a herd of bison in mesic grassland as a direct estimation of the water sources consumed over time. Bison at this site have their choice of a range of habitats and drinking water sources. Potential source-water samples measured had a large range of isotopic signatures, allowing the isotopic composition of water from bison fecal samples to be proportionally estimated based on varying sources. Results indicate bison have low reliance on multiple streams on site; rather, the majority of water consumed was from rainfall-fed sources (puddles and wallows) and from forage. Our research suggests that source-water analysis from fecal samples is a robust technique when samples from large grazers can be collected soon after production. These results have implications for analyses of the foraging patterns and landscape utilization by this and other large grazers, because hotter and drier future conditions are likely to reduce the frequency and amount of rainfall-fed puddles available for consumption in many grassland systems worldwide.

The importance of timing of precipitation for grassland productivity - Craine, J.M. (Plant Ecology, 2013)
Future climate change is likely to involve changes in the amount and intensity of precipitation, but also its timing during the year. To better understand how the timing of precipitation impacts plant productivity, a 27-year dataset on grass productivity for a mesic North American grassland was analyzed. Along with other climate parameters, the ability of the average date precipitation fell during different climate periods to explain grass productivity was tested. Across the 27 years, grass productivity was greater in years with more precipitation between April 15 and August 2. After accounting for differences in the total amount of precipitation during this time period, in years when precipitation between May 9 and August 27 fell later, measured grass productivity was less. Variation among years in precipitation timing was of similar importance as temperatures during critical climate periods and about 40 % of the importance of the total amount of precipitation. In all, although the mechanisms generating these responses are uncertain, precipitation timing within a growing season has substantial effects on productivity.
Keywords: critical climate period; Grasslands; Konza Prairie; Precipitation; Primary productivity; Timing

Influence of macroconsumers, stream position, and nutrient gradients on invertebrate assemblage development following flooding in intermittent prairie streams - Bertrand, K.N.; M.R. Whiles; K. B. Gido; Murdock, J.N. (Hydrobiologia, 2013)
Climate change in the US Great Plains is expected to result in less frequent but more severe floods. This will affect hydrologic cycles, stream organisms, and ultimately ecosystem structure and function. We examined factors influencing invertebrate assemblages following flooding in 3 reaches (20 pools) of Kings Creek, an intermittent prairie stream on the Konza Prairie Biological Station, using replicated macroconsumer enclosures (fishless, dace, shiners, ambient). Invertebrate densities and biomass increased rapidly following scouring, including rapid colonizing taxa and relatively long-lived taxa, but macroconsumers had no significant effects. Rather, distance, which was negatively correlated with the concentration of dissolved inorganic nitrogen, from the downstream confluence with a larger stream significantly influenced assemblage structure, with higher richness and greater nutrient concentrations closer to the confluence. Results support previous findings that recovery patterns following flooding in this grassland stream are strongly influenced by proximity to refuges. Furthermore, physical rather than biological factors appear more influential in structuring invertebrate assemblages in these frequently disturbed systems. Predicted increases in the intensity and duration of hydrologic disturbances will increase direct impacts on stream communities, relative to indirect effects through potential changes in macroconsumer communities. Human activities that alter refuges may further impede recovery following hydrologic disturbances.
Keywords: disturbance; Flood; Invertebrate; Macroconsumer Gradients; Prairie stream

The influence of moisture availability on terrestrial ecosystems: Effects on soil animal communities along a regional/global-scale climate gradient - Sylvain, Z.L. (Colorado State University, 2013)
Earth's climate is being altered at an alarming rate, and the consequences of these changes on the planet's ecosystems are unclear. In addition to increased warming due to rising CO2 concentrations, alterations to precipitation patterns will influence soil moisture availability in terrestrial ecosystems and this will have important consequences for plant growth and the ability of soil systems to perform functions such as decomposition and nutrient cycling. The effects on soil systems are especially poorly understood, partly due to the many interactions between environmental conditions and the numerous species found within soil ecosystems, ranging from microbial organisms such as bacteria, archaea and fungi to soil animals including mites and nematodes. With chapter 2, I provide an overview of the role of soil biodiversity and the implications climate and land-use changes may have for ecosystems as a consequence of their effects on soil biodiversity. I then examine the current state of understanding for the influence of soil moisture availability on plant and soil communities of temperate ecosystems in chapter 3, and highlight challenges for future research such as the inclusion of diversity metrics and soil animal community responses in climate change experiments as well as studies that operate at scales larger than single sites in order to better capture the dynamics of ecosystem changes. My research focused on one aspect of climate change, the alteration of soil moisture availability within ecosystems due to changes in precipitation regimes, and whether it affected soil organisms, particularly soil mites and nematodes (Chapter 4 of this dissertation). These two groups were selected because of their high abundances and diversity within soil ecosystems, their dependence upon soil water availability as a consequence of life history traits and their contributions to decomposition and nutrient cycling processes. To examine the effects of changing moisture availability on communities of mites and nematodes I analyzed soil samples along a large scale regional/global climate gradient made up of four long-term ecological research (LTER) sites including Konza Prairie LTER (KNZ), Kansas, Shortgrass Steppe LTER (SGS), Colorado, Jornada Basin LTER (JRN), New Mexico and McMurdo Dry Valleys LTER (MCM), Antarctica. I established elevation transects across hill slopes to obtain landscape-scale gradients of soil moisture availability within each of these ecosystems and sampled existing experimental manipulations of moisture availability from 2009-2011. Mites and nematodes were sorted to trophic groups to determine their ecological role and how changes to their abundances may affect ecosystems. Mite and nematode abundances responded strongly to changes in moisture availability. Across the large-scale climate gradient of all four sites, a positive non-linear response was found with particularly large increases in animal abundances corresponding to incremental moisture increases at the lower limits of moisture availability. Within each of the ecosystems, however, the responses of soil animal trophic group abundances to moisture availability were very similar and were largely negative. In chapter 5 of this dissertation, I further explore the effects of soil moisture and top-down or bottom-up community dynamics on mite and nematode abundances. To do this, I constructed a structural equation model examining the direct and indirect effects of soil moisture availability and trophic interactions on soil animal trophic group abundances. Results of this model suggest that soil moisture strongly controls populations of these organisms. Additionally, predatory mite and nematode trophic groups have top-down controls on lower trophic groups, although these interactions do not appear to be due to predation and instead suggest the influence of additional, unmeasured environmental factors acting indirectly on lower-level soil animal trophic groups. With this dissertation, I demonstrate that changes to soil moisture regimes can have important effects on soil animal communities. A review of the literature (Chapter 3 of this dissertation) showed altered soil moisture availability had the clearest effects on plants, with effects on soil organisms being more idiosyncratic, likely as a result of stronger indirect than direct effects. Experimental evidence along a regional/global climate gradient of two desert and two grassland sites (Chapter 4 of this dissertation) show that increases to moisture availability have strong positive effects on mite and nematode communities, especially at low levels of moisture availability across this large, multi-site scale. At smaller scales (within individual ecosystems) this response becomes weaker and results in declines to animal groups at most sites. These results suggest that as precipitation regimes are altered as a consequence of climate change, the resultant alterations to soil moisture availability may have important feedbacks to terrestrial ecosystems. Observed changes to trophic group structuring in response to changes in moisture availability (Chapters 4 and 5 of this dissertation) show that food webs may be restructured due to future changes in moisture availability, leading to increases to root herbivory and increasing the amount of energy flowing through bacterial rather than fungal decomposition pathways. These changes to food webs can result in alterations to nutrient cycling pathways and shifts in carbon allocation within plant communities, which will further influence ecosystem dynamics.

Influences of patch-burn grazing and riparian protection on the ecological integrity of tallgrass prairie headwater streams - Jackson, K.E. (Southern Illinois University, 2013)
Conversion to agriculture, land fragmentation, and removal of native grazers have made tallgrass prairies and the streams that drain them one of the most imperiled systems on earth. Patch-burn grazing (PBG), an increasingly common management practice on remaining prairie parcels, has been shown to benefit cattle and grassland birds. However, potential influences of this practice on streams are unknown. To address this, we sampled stream macroinvertebrates and benthic organic matter two years before and three years during PBG on two watersheds with riparian fencing (fenced), two grazed watersheds without riparian fencing (unfenced), and two ungrazed (control) watersheds. Very fine benthic organic matter increased 51% in unfenced watersheds after implementation of PBG, accompanied by a threefold increase in fine organic sediments in the same watersheds. Contribution of fine inorganic sediments to total substrata increased 28% in unfenced watersheds during PBG, while fine inorganic sediments decreased in both the control (18%) and fenced (16%) watersheds. Increases in the contribution of Chironomidae to total macroinvertebrate abundance (18% before, 49% during PBG) and biomass (10% before, 19% during PBG) were evident in unfenced streams. In contrast, abundance of sensitive EPT taxa decreased an order of magnitude from 7,635 to 687 individuals m-2 in unfenced streams, but did not change in fenced and control streams. Increases in tolerant taxa and fine organic and inorganic sediments, along with reductions in metrics of biotic integrity, suggest PBG adversely impacts prairie streams. However, the absence of negative responses in fenced watersheds indicates that riparian fencing can mitigate these impacts by serving as a buffer to prevent excess sedimentation. In order to properly manage remaining tallgrass prairie parcels, it is important to consider both the aquatic and terrestrial components of these systems, as they are tightly linked. Results from this study provide a basis for management and policy decisions regarding remaining grassland watersheds.

Intra-specific responses of a dominant C4 grass to altered precipitation patterns - M.L. Avolio; M.D. Smith (Plant Ecology, 2013)
The mechanisms by which global change alters the genotypic structure of populations by selection remain unclear. Key to this understanding is elucidating genotype–phenotype relationships under different environmental conditions as genotypes could differ in their plasticity or in their tolerance to changing environmental conditions. We have previously observed selection of certain genotypes of the dominant C4 grass Andropogon gerardii L. within the on-going Rainfall Manipulation Plots (RaMPs) experiment at Konza Prairie Biological Station in Kansas. The RaMPs experiment has been experimentally imposing ambient and more variable (altered) precipitation patterns since 1998. Here, we studied phenotypic differences among six genotypes to gain insight into what drove the pattern of selection previously observed and assess potential genotype × environmental interactions. In 2008 and 2009 we sampled individuals of genotypes in the RaMPs and within unmanipulated reference plots located adjacent to the RaMPs experiment. For each individual, we measured both leaf-level (specific leaf area, stomatal conductance) and whole-plant growth (height, biomass) traits. We consistently detected differences among genotypes in the reference plots. Additionally, when focusing on two genotypes found in the altered and ambient RaMPs we observed no genotype × environment interactions. Overall, we found in an intact population of A. gerardii there exists phenotypic variability among genotypes, but no genotype × environment interactions. Thus our results demonstrate that differences in plasticity of genotypes do no explain the pattern of selection we observed.

Invertebrates, ecosystem services and climate change - Prather, C.M.; Pelini, S.; Laws, A.; Rivest, E.; Woltz, M.; Bloch, C.P.; Del Toro, I.; Ho, Chuan-Kai.; Kominoski, J.; Newbold, T.A.S.; Parsons, S.; Anthony Joern (Biological Reviews, 2013)
The sustainability of ecosystem services depends on a firm understanding of both how organisms provide these services to humans and how these organisms will be altered with a changing climate. Unquestionably a dominant feature of most ecosystems, invertebrates affect many ecosystem services and are also highly responsive to climate change. However, there is still a basic lack of understanding of the direct and indirect paths by which invertebrates influence ecosystem services, as well as how climate change will affect those ecosystem services by altering invertebrate populations. This indicates a lack of communication and collaboration among scientists researching ecosystem services and climate change effects on invertebrates, and land managers and researchers from other disciplines, which becomes obvious when systematically reviewing the literature relevant to invertebrates, ecosystem services, and climate change. To address this issue, we review how invertebrates respond to climate change. We then review how invertebrates both positively and negatively influence ecosystem services. Lastly, we provide some critical future directions for research needs, and suggest ways in which managers, scientists and other researchers may collaborate to tackle the complex issue of sustaining invertebrate-mediated services under a changing climate.
Keywords: Biodiversity; bioindicator species; Climate change; ecosystem engineers; ecosystem services; insects; invertebrates; sustainability

Life history traits associated with body size covary along a latitudinal gradient in a generalist grasshopper - Parsons, S.; Anthony Joern (Oecologia, 2013)
Animal body size often varies systematically along latitudinal gradients, where individuals are either larger or smaller with varying season length. This study examines ecotypic responses by the generalist grasshopper Melanoplus femurrubrum (Orthoptera: Acrididae) in body size and covarying, physiologically based life history traits along a latitudinal gradient with respect to seasonality and energetics. The latitudinal compensation hypothesis predicts that smaller body size occurs in colder sites when populations must compensate for time constraints due to short seasons. Shorter season length requires faster developmental and growth rates to complete life cycles in one season. Using a common garden experimental design under laboratory conditions, we examined how grasshopper body size, consumption, developmental time, growth rate and metabolism varied among populations collected along an extended latitudinal gradient. When reared at the same temperature in the lab, individuals from northern populations were smaller, developed more rapidly, and showed higher growth rates, as expected for adaptations to shorter and generally cooler growing seasons. Temperature-dependent, whole organism metabolic rate scaled positively with body size and was lower at northern sites, but mass-specific standard metabolic rate did not differ among sites. Total food consumption varied positively with body size, but northern populations exhibited a higher mass-specific consumption rate. Overall, compensatory life history responses corresponded with key predictions of the latitudinal compensation hypothesis in response to season length.
Keywords: acrididae; Development time; Growth rate; Latitudinal compensation hypothesis; Melanoplus femurrubrum

Life-history constraints in grassland plant species: a growth-defence trade-off is the norm - Lind, E.M.; E.T. Borer; Seabloom, E.; P. Adler; J.D. Bakker; D.M. Blumenthal; Crawley, M.; Davies, K.; Firn, J.; Gruner, D.S.; Harpole, W.S.; Hautier, Y.; et al. (Ecology Letters, 2013)
Plant growth can be limited by resource acquisition and defence against consumers, leading to contrasting trade-off possibilities. The competition-defence hypothesis posits a trade-off between competitive ability and defence against enemies (e.g. herbivores and pathogens). The growth-defence hypothesis suggests that strong competitors for nutrients are also defended against enemies, at a cost to growth rate. We tested these hypotheses using observations of 706 plant populations of over 500 species before and following identical fertilisation and fencing treatments at 39 grassland sites worldwide. Strong positive covariance in species responses to both treatments provided support for a growth-defence trade-off: populations that increased with the removal of nutrient limitation (poor competitors) also increased following removal of consumers. This result held globally across 4 years within plant life-history groups and within the majority of individual sites. Thus, a growth-defence trade-off appears to be the norm, and mechanisms maintaining grassland biodiversity may operate within this constraint.

Limited effects of dominant species population source on community composition during community assembly - D.J. Gibson; S.G. Baer; Klopf, R.P.; Reed, L.K.; Wodika, B.R.; Willand, J.E. (Journal of Vegetation Science, 2013)
Question To what extent do dominant species population sources and subordinate species pools affect diversity and composition of an assembling grassland community? Location Illinois, USA. Methods Percentage cover of all species were recorded annually in 36 1-m2 quadrats assigned to a factorial combination of dominant species population source (functionally distinct cultivar or non-cultivar seed source) and designed species pool (three levels varying in species identity, but with equal functional group representation and richness) during the first 4 yr of community assembly in an experimental grassland restoration. Results Univariate and multivariate analyses showed that individual species abundance, life form and community composition differed significantly among designed species pools, but were not strongly affected by population source of the dominant species (cultivar or non-cultivar). There were fewer C4 species in cultivar plots but only in one of three designed species pools during one of 4 yr of community assembly. The number of legume and forb species was higher in cultivar plots, but also only in one of the 4 yr of study. Other changes in species richness and abundance were solely related to successional change. Conclusions Non-dominant species introduced to restore plant communities strongly affects plant community composition, and composition can show fidelity to designed species pools. Only marginal or temporary effects of dominant species seed source were observed in the assembling plant community. Thus, we found no strong evidence that the source of dominant species, in this case cultivars compared to local ecotypes, has consequences for community assembly in the early stages of restoration (1–4 yr). The absence of a strong dominant species source effect may be exacerbated by the assembly of diverse plant communities, resulting in a stronger effect of subordinate species seed mixture in restoration.
Keywords: Community assembly; dominant species; Extended phenotype; grassland; restoration; Seed pool; tallgrass prairie

Linking abundances of the dung fungus Sporormiella to the density of bison: implications for assessing grazing by megaherbivores in paleorecords - Gill, J.L.; McLauchlan, K.K.; Skibbe, A.M.; Goring, S.; Zirbel, C.R.; Williams, J.W. (Journal of Ecology, 2013)
Megaherbivores likely had important influences on past vegetation dynamics, just as they do in modern ecosystems. The exact nature of megaherbivores' role can be studied using a relatively new suite of palaeoecological techniques, including the quantification of fossil spores from Sporormiella and other coprophilous fungi as indicators of megafaunal biomass in sediment records. However, a quantitative linkage of spore abundance with megaherbivore biomass or grazing intensity has been lacking. Konza Prairie Biological Station (Kansas, USA), located in the midcontinent of North America, contains native tallgrass prairie grazed by a herd of bison (Bison bison) in a 1000-ha enclosure, providing an excellent opportunity to test the effects of megaherbivores on grassland community composition and their potential signature in the palynological record. We collected pollen and spores during 2009 and 2010 from a network of 28 modified Tauber traps. The precise locations of the bison herd were recorded using GPS collars; we calculated bison grazing intensity (kg m−2 year−1) to high spatial precision within concentric circles around each trap (radii from 25 to 500 m). Both relative (per cent) and absolute (concentration) abundances of Sporormiella were significantly higher in traps inside the enclosure and were positively correlated with bison grazing intensity. The cut-off for distinguishing between bison-grazed and ungrazed traps was determined to be 2.8% Sporormiella of the total pollen and spore sum, consistent with previous palaeoecological reconstructions. The relationship between Sporormiella abundances and available grazing area around each trap was strongest at short radii (25–100 m), suggesting that spores do not disperse far from their source. Sporormiella should thus be considered a local-scale indicator of megaherbivore presence. Traps in the grazed area had significantly higher percentages of Ambrosia and lower percentages of Poaceae pollen than traps from ungrazed areas. This suggests that the pollen record has the potential to detect the ecological effects of bison grazing on grassland community composition. Synthesis. This study refines the use of Sporormiella as a proxy for local megaherbivore presence, especially in grassland systems. Multiproxy Sporormiella and pollen analyses may help elucidate the past drivers of grassland dynamics, including the possible role of bison in mediating grass–forb interactions during the variable moisture regimes of the last 12,000 years.

Long-term climate sensitivity of grazer performance: a cross-site study - Craine, J.M. (PLOS ONE, 2013)
Climate change will affect grasslands in a number of ways, but the consequences of a warmer, drier world for grazers is uncertain. Predicting future grazer performance is complex since climate change affects both the quantity and quality of forage through a combination of processes that occur over a range of time scales. To better predict the consequences of climate change for grazer performance, a dataset was compiled of over a quarter million bison weights distributed across 22 US herds that span a large range of climates. Patterns of bison body mass among sites, age classes, and sexes were analyzed with respect to differences in geographic patterns of climate and interannual variation in climate. While short-term effects of climate variability are likely to depend on the magnitude and timing of precipitation during the year, grazers will be negatively affected by sustained hotter, drier conditions most likely associated with reductions in forage quality. Short-term, little effect of high temperatures on bison performance is observed, which suggests that the long-term effects of higher temperatures are likely to accrue over time as nitrogen availability in grasslands is reduced and forage quality declines. If relationships observed for bison are general for cattle, the economic consequences of higher temperatures due to decreased weight gain in US cattle could be on the order of US$1B per 1°C increase in temperature. Long-term monitoring of forage quality as well as native and domesticated grazer performance is recommended to better understand climate change effects on grazers.
Keywords: Animal performance; bison; Cattle; Climate change; Grasses; Grasslands; Meteorology; Weight gain

Long-term nitrogen amendment alters the diversity and assemblage of soil bacterial communities in tallgrass prairie - Coolon, J.D.; Jones, K.L.; Todd, T.C.; John M. Blair; Herman, M.A. (PLoS ONE, 2013)
Anthropogenic changes are altering the environmental conditions and the biota of ecosystems worldwide. In many temperate grasslands, such as North American tallgrass prairie, these changes include alteration in historically important disturbance regimes (e.g., frequency of fires) and enhanced availability of potentially limiting nutrients, particularly nitrogen. Such anthropogenically-driven changes in the environment are known to elicit substantial changes in plant and consumer communities aboveground, but much less is known about their effects on soil microbial communities. Due to the high diversity of soil microbes and methodological challenges associated with assessing microbial community composition, relatively few studies have addressed specific taxonomic changes underlying microbial community-level responses to different fire regimes or nutrient amendments in tallgrass prairie. We used deep sequencing of the V3 region of the 16S rRNA gene to explore the effects of contrasting fire regimes and nutrient enrichment on soil bacterial communities in a long-term (20 yrs) experiment in native tallgrass prairie in the eastern Central Plains. We focused on responses to nutrient amendments coupled with two extreme fire regimes (annual prescribed spring burning and complete fire exclusion). The dominant bacterial phyla identified were Proteobacteria, Verrucomicrobia, Bacteriodetes, Acidobacteria, Firmicutes, and Actinobacteria and made up 80% of all taxa quantified. Chronic nitrogen enrichment significantly impacted bacterial community diversity and community structure varied according to nitrogen treatment, but not phosphorus enrichment or fire regime. We also found significant responses of individual bacterial groups including Nitrospira and Gammaproteobacteria to long-term nitrogen enrichment. Our results show that soil nitrogen enrichment can significantly alter bacterial community diversity, structure, and individual taxa abundance, which have important implications for both managed and natural grassland ecosystems.
Keywords: Bacteria; Biodiversity; Ecosystem functioning; Grasslands; Microbial ecosystems; Plant communities; Ribosomal RNA; Sequence analysis

Macroinvertebrate responses to removal of riparian woody vegetation along tallgrass prairie streams - Vandermyde, J.M. (Southern Illinois University, 2013)
Woody vegetation encroachment has become a major threat to tallgrass prairie streams mainly because of fire suppression. This process converts prairie streams from open to closed canopy systems. The effects of these riparian changes are poorly understood, but the relative importance of basal resources presumably shifts from primarily autochthonous to allochthonous with increasing canopy cover, potentially altering macroinvertebrate functional structure and production. To assess the effects of woody vegetation encroachment on stream ecosystem structure and function, riparian trees were removed from two headwater stream reaches on the Konza Prairie Biological Station (KPBS) in eastern Kansas. Experimental stream reaches were compared to streams with naturally open and closed canopies before and after the manipulation. Benthic organic matter and macroinvertebrates were collected monthly from each reach for one year before and one year after woody vegetation removal. Total community production in canopy removal reaches ranged from 8.9-10.2 g AFDM m-2 y-1 before riparian removal, and this increased significantly to 13.4-14.5 g AFDM m-2 y-1 after riparian removal. Scraper production in canopy removal reaches was 2.8-3.9 g AFDM m-2 y-1 before riparian removal, and increased significantly to 6.0-8.7 g AFDM m-2 y-1 after riparian removal, presumably due to enhanced food availability. Total community production in naturally open reaches ranged from 7.6-12.6 g AFDM m-2 y-1 before riparian removal and decreased to 6.5-9.8 g AFDM m-2 y-1 after riparian removal. Riparian forest removal altered macroinvertebrate production and functional structure, but higher macroinvertebrate production in canopy removal reaches compared to naturally open reaches suggested natural conditions were not restored one year after riparian removal. However, macroinvertebrate communities in naturally open and canopy removal reaches became more similar after riparian removal. Functional structure, based on production, in naturally open and canopy removal reaches after riparian removal was dominated by scrapers (45-60% of total production), with similar proportions of collector-gatherers (12-26%) and predators (15-25%). Collector-filterers and shredders contributed < 9% of total production in naturally open and canopy removal reaches after riparian removal. Results demonstrate that woody vegetation encroachment and riparian forest removal significantly influence tallgrass prairie stream structure and function. Information from this study can help inform and guide management, restoration, and conservation of remaining tallgrass prairie streams.

Mechanisms of selection: Phenotypic differences among genotypes explain patterns of selection in a dominant species - M.L. Avolio; M.D. Smith (Ecology, 2013)
Predicted changes in precipitation means and variability are expected to alter genotype composition of plant populations; however, it remains unclear whether selection will be for trait differences among genotypes or phenotypic plasticity. This is especially true for more variable precipitation patterns that simultaneously alter soil moisture means and variability. In a previous study we found that a decade of more variable growing-season precipitation patterns changed the genotypic composition of a dominant C4 grass population (Andropogon gerardii) in native tallgrass prairie located in northeastern Kansas. Here, we assessed potential mechanisms underlying the changes observed in population structure of this species by studying how changes in both the size and variability of watering events affected ecophysiological, growth, biomass-allocation, and fitness traits of five common genotypes of A. gerardii in a greenhouse experiment. Three of these genotypes had greater abundances or were only present in field plots receiving 10 years of greater intra-annual variability in growing-season precipitation patterns. In a fully factorial experiment, we subjected the five genotypes to three water amounts (average for Kansan study site, a 40% decrease, and a 60% increase) and two watering frequency treatments (every 5 or 10 days) to produce differences in soil moisture amount and variability, respectively. We found genotype × water amount interactions for traits related to leaf-level physiology and biomass allocation; in many cases genotypes that performed better under low soil moisture conditions were outperformed by other genotypes under high soil moisture conditions. For the three genotypes that had greater abundance in field plots that received more variable precipitation patterns, we found evidence that genotypes differed in their allocation to above- vs. belowground biomass, demonstrating phenotypic trait divergence. Our results suggest that a genetically diverse population can have enough trait variation among genotypes for adaptation to occur, and thus, for dominant species, microevolution may be an important aspect of adaptation to changing environmental conditions.

Patterns of diversity and adaptation in Glomeromycota from three prairie grasslands - Ji, B.; Gehring, C.A.; G.T. Wilson; Miller, R.M.; Flores-Renteria, L.; Johnson, N.C. (Molecular Ecology, 2013)
Arbuscular mycorrhizal (AM) fungi are widespread root symbionts that often improve the fitness of their plant hosts. We tested whether local adaptation in mycorrhizal symbioses would shape the community structure of these root symbionts in a way that maximizes their symbiotic functioning. We grew a native prairie grass (Andropogon gerardii) with all possible combinations of soils and AM fungal inocula from three different prairies that varied in soil characteristics and disturbance history (two native prairie remnants and one recently restored). We identified the AM fungi colonizing A. gerardii roots using PCR amplification and cloning of the small subunit rRNA gene. We observed 13 operational taxonomic units (OTUs) belonging to six genera in three families. Taxonomic richness was higher in the restored than the native prairies with one member of the Gigaspora dominating the roots of plants grown with inocula from native prairies. Inoculum source and the soil environment influenced the composition of AM fungi that colonized plant roots. Correspondingly, host plants and AM fungi responded significantly to the soil–inoculum combinations such that home fungi often had the highest fitness and provided the greatest benefit to A. gerardii. Similar patterns were observed within the soil–inoculum combinations originating from two native prairies, where five sequence types of a single Gigaspora OTU were virtually the only root colonizers. Our results indicate that indigenous assemblages of AM fungi were adapted to the local soil environment and that this process occurred both at a community scale and at the scale of fungal sequence types within a dominant OTU.

Phenologies of North American Grasslands and Grasses - Henebry, G.M. (Phenology: An Integrative Environmental Science, 2e, 2013)
Inquiry into the phenologies of grasslands and grasses in North America has progressed substantially in the past decade. Four themes of the recent phenological research are surveyed: (1) the role of exotic and invasive species in affecting grasslands phenology; (2) the role of water and belowground dynamics on phenologies; (3) how experimental manipulations of grasslands have affected constitutive phenologies; and (4) advances in the remote sensing of grasslands. The phyllochron concept used in ontogenetic studies of grass species is discussed in light of grasslands phenology and its link between daylength and thermal time

Physiological and growth responses of switchgrass (Panicum virgatum L.) in native stands under passive air temperature manipulation - Hartman, J.C.; Jesse B. Nippert (Global Change Biology-Bioenergy, 2013)
In the central Great Plains of North America, climate change predictions include increases in mean annual temperature of 1.5–5.5 °C by 2100. Ecosystem responses to increased temperatures are likely to be regulated by dominant plant species, such as the potential biofuel species Panicum virgatum (switchgrass) in the tallgrass prairie. To describe the potential physiological and whole-plant responses of this species to future changes in air temperatures, we used louvered open-sided chambers (louvered OSC; 1 × 1 m, adjustable height) to passively alter canopy temperature in native stands of P. virgatum growing in tallgrass prairie at varying topographic positions (upland/lowland). The altered temperature treatment decreased daily mean temperatures by 1 °C and maximum temperatures by 4 °C in May and June, lowered daytime stomatal conductance and transpiration, decreased tiller density, increased specific leaf area, and delayed flowering. Among topographic contrasts, aboveground biomass, flowering tiller density, and tiller weight were greater in lowland sites compared to upland sites, with no temperature treatment interactions. Differences in biomass production responded more to topography than the altered temperature treatment, as soil water status varied considerably between topographic positions. These results indicate that while water availability as a function of topography was a strong driver of plant biomass, many leaf-level physiological processes were responsive to the small decreases in daily mean and maximum temperature, irrespective of landscape position. The varying responses of leaf-level gas exchange and whole-plant growth of P. virgatum in native stands to altered air temperature or topographic position illustrate that accurately forecasting yields for P. virgatum in mixed communities will require greater integration of physiological responses to simulated climate change (increased temperature) and resource availability over natural environmental gradients (soil moisture).

Population origin and genome size do not impact Panicum virgatum (switchgrass) responses to variable precipitation - O’Keefe, K.; Tomeo, N.; Jesse B. Nippert; Springer, C.J. (Ecosphere, 2013)
Population-level adaptation to broad-scale regional climates or within-population variation in genome size of the genetically and phenotypically diverse C4 grass, Panicum virgatum (switchgrass), may influence the responses of this species to future precipitation variability associated with climate change. Therefore, we investigated P. virgatum responses to water variability between natural populations collected across a latitudinal gradient and among individuals spanning a range of genomes sizes within these populations. P. virgatum plants from natural populations originating from Kansas, Oklahoma, and Texas, U.S.A, received frequent, small precipitation events (“ambient”) or infrequent, large precipitation events (“altered”) to simulate contrasting rainfall variability expected for this region. We measured leaf-level physiology, aboveground biomass and genome size for each individual. Gas exchange rates and aboveground biomass varied significantly by population origin but did not differ by genome size. Altered precipitation treatments reduced leaf-level physiological rates; however this result did not vary by population or genome size. Our results suggest that trait variation in P. virgatum is primarily attributed to population-level adaptation across a latitudinal gradient, not genome size, and that neither population-level adaptation nor genome size may be important predictors of P. virgatum responses to future climatic conditions.

Positive association between social and extra-pair mating in a polygynous songbird, the dickcissel (Spiza americana) - Sousa, Bridget F.; Westneat, David F. (Behavioral Ecology and Sociobiology, 2013)
In polygynous species, males appear to gain additional offspring by pairing with multiple females simultaneously. However, this may not be true if some females copulate outside of the social pair bond. Polygynous males could experience lower paternity because of trade-offs among gaining multiple social mates, guarding fertility with these mates, and pursuing extra-pair matings. Alternatively, polygynous males could simultaneously gain extra social mates and have high paternity, either because of female preferences or because of male competitive attributes. We tested four predictions stemming from these hypotheses in a facultatively polygynous songbird, the dickcissel (Spiza americana). Unlike most previous studies, we found that males with higher social mating success (harem size) also tended to have higher within-pair paternity and that the number of extra-pair young a male sired increased significantly with his social mating success. Females that paired with mated males were not more likely to produce extra-pair young. In contrast, extra-pair paternity was significantly lower in the nests of females whose nesting activity overlapped that of another female on the same territory. This pattern of mating was robust to differences in breeding density. Indeed, breeding density had no effect on either extra-pair mating or on the association between polygyny and paternity. Finally, nest survival increased with harem size. This result, combined with the positive association between polygyny and paternity, contributed to significantly higher realized reproductive success by polygynous male dickcissels.
Keywords: density; Extra-pair paternity; Female choice; Mating patterns; Polygyny; Trade offs

Precipitation timing and grazer performance in a tallgrass prairie - Craine, J.M.; Towne, E.G.; Tolleson, D.; Jesse B. Nippert (Oikos, 2013)
Changes in precipitation amount and variability have the potential to alter the structure and function of grasslands, but we know little about how changes in the timing of precipitation might affect grasslands. Here, we analyze long-term records from a tallgrass prairie to show that shifts in the timing of precipitation during the growing season have little effect on primary productivity or grass reproduction, but can greatly affect grazer performance. While greater late-season precipitation increases the weight gain of adult and young bison, greater mid-season precipitation decreases their weight gain. In addition, calving rates are lower after years with greater mid-season precipitation and higher after years with greater late-season precipitation. As well-timed drought can actually increase grazer weight gain and reproduction, it will be necessary to generate predictions of within-season distribution of precipitation to successfully forecast future grazer performance.

Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness? - Seabloom, E.W.; E.T. Borer; Buckley, Y.; Cleland, E.E.; Davies, K.; Firn, J.; Harpole, W.S.; Hautier, Y.; Lind, E.; MacDougall, A.; Orrock, J.L.; Prober, S.M.; et al. (Global Change Biology, 2013)
Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species' relative abundance will more rapidly advance our understanding of invasions.

Regional-climate and local-microbial controls on ecosystem processes during grassland restoration - Mendola, M.M. (Southern Illinois University, 2013)
Root productivity likely has consequences for the composition, activity, and recovery of soil microbial populations and the belowground processes mediated by these organisms. In tallgrass prairie, ecotypic variation potentially exists in response to a strong precipitation gradient across the Great Plains. Thus, ecotypic variation within a species may differentially affect belowground net primary productivity (BNPP), the associated soil microbial community, and may scale up to affect ecosystem processes. The goals of this study were to elucidate: (1) whether ecotype, environment, or an ecotype by environment interaction regulate BNPP of a dominant species (Andropogon gerardii) collected from and reciprocally planted in common gardens across a precipitation gradient, and (2) whether variation in BNPP scales to affect microbial biomass and ecosystem processes. I quantified root biomass, BNPP (using root ingrowth bags), soil microbial biomass, and nutrient mineralization rates in root-ingrowth cores below six population sources of A. gerardii (2 Illinois, 2 eastern Kansas, and 2 central Kansas) established in southern Illinois, eastern Kansas, and central Kansas. An ecotype effect was found on above and belowground net primary productivity, but these findings did not translate to soil response variables. Microbial populations themselves may affect the productivity and composition of prairie species. In a second study, soil ecological knowledge (SEK) was tested by applying a native prairie soil slurry amendment to restoration plots to determine efficacy of this method as a restoration practice. The goals of this two year study were to elucidate: (1) whether a slurry amendment of prairie soil would increase above and belowground productivity and belowground ecosystem processes in a prairie restoration, and (2) to evaluate whether differences in plant diversity will scale to affect belowground productivity and ecosystem processes. I quantified aboveground net primary productivity (ANPP) and species composition, as well as root biomass, belowground net primary productivity (BNPP), soil microbial biomass, and nutrient mineralization rates in root-ingrowth cores installed in treated and control plots. A treatment effect was noted on root biomass and total PLFA biomass; however, there was no treatment effect on cover, ANPP, or soil microbial processes. Though the soil microbial community did represent native prairie soil, there was poor establishment of prairie plant species. These factors may be due to the limited time available for data collection and the lack of precipitation in the second growing season. Longer studies may be necessary to fully examine the effects of soil slurry amendments as restoration tools.

Responses to long-term fertilization and burning: impacts on nutrient dynamics and microbial composition in a tallgrass prairie - Carson, M. (Kansas State University, 2013)
Anthropogenic activities impact ecosystems in numerous direct and indirect ways, affecting the cycling of carbon (C) and nitrogen (N) on local, regional and global scales. North America tallgrass prairie is an ecosystem profoundly altered by anthropogenic activities, with most native prairie converted to alternate land uses or heavily impacted by other environmental changes. While aboveground responses to anthropogenic drivers have received much attention, the responses of belowground biota, ecological processes, and nutrient allocation to land management and environmental change are poorly documented, especially over long timeframes. This research builds upon a long-term experiment (the Belowground Plot Experiment) initiated in 1986 at Konza Prairie Biological Station (Manhattan, KS). I utilized a subset of treatments to address the effects of annual burning vs. fire suppression and/or chronic N additions on soil C and N dynamics and microbial communities in tallgrass prairie. I measured a suite of soil variables related to C and N cycling during the 2012 growing season, including total soil C and N, microbial biomass C and N, in situ net N mineralization, potential N mineralization, in situ CO2 efflux, and potentially mineralizable soil C. I also assessed changes in microbial community composition using microbial phospholipid fatty acids (PLFA) profiles. Annual burning significantly (p≤0.05) increased the soil C:N ratio and in situ CO2 efflux, while decreasing potential ammonification and nitrification rates. Annual burning also increased total PLFA mass and relative abundance of fungi. Chronic N addition (100 kg N ha-1 year-1) significantly reduced the soil C:N ratio, while increasing total soil N and potential nitrification and ammonification rates. Chronic N addition reduced potential C mineralization, microbial biomass C and N, and altered microbial community composition by increasing abundance of bacterial PLFAs and reducing fungal PLFAs. Sampling date also significantly affected many variables. These results indicate that different fire regimes and chronic N enrichment over decades affects soil C and N pools and transformations, as well as microbial biomass and composition. In total, this study highlights the importance of long-term ecological research and identifies likely changes in tallgrass prairie nutrient dynamics and soil microbial communities under increased N and frequent burning.
Keywords: Biogeochemistry; Carbon; Nitrogen; Soil ecology; tallgrass prairie

Restoration Ecology - S.G. Baer (Oxford Bibliographies in Ecology, 2013)

Seed source has variable effects on species, communities, and ecosystem properties in grassland restorations - Carter, D.L.; John M. Blair (Ecosphere, 2013)
Research to date regarding the relative advantages of local versus non-local sources of plantmaterial for restoration has produced equivocal results. This research has typically focused on theperformance of individual species at individual locations and without addressing higher order communityand ecosystem properties. We investigated the effects of seed source (local, non-local, and mixed-sourcetreatments) on species, community, and ecosystem properties under a range of environmental conditionsusing reciprocal common gardens at locations in three states (Nebraska, Kansas, and Oklahoma). In orderto mimic the restoration of grassland vegetation under realistic conditions where multiple species interactwith one another during establishment, we seeded twelve species together between December, 2009 andJanuary, 2010, and assessed responses in 2010, 2011, and 2012. Both common garden location and seedsource affected the establishment of individual species (measured as species-specific biomass), butresponses were not consistent among species. No seed source had a consistent advantage across all sites oracross all species. In a few cases, the local source was most productive for a particular species at onelocation, but no species showed a consistent local advantage across locations or years. Rather, in two out ofthree species that exhibited a local advantage at one location, the same source was also the most productiveat a non-local site. Community structure and species richness differed among locations in all years, butsource did not significantly affect seeded species richness, and source only affected community structure in2011. Despite source effects on individual species and community structure, seed source had no significanteffects on the combined productivity of seeded species. These results do not support the targeted use oflocal sources when the establishment of sown species and primary productivity are restoration objectives.Using mixed-source species mixtures may increase chances of restoration success, given the idiosyncrasy ofindividual species’ responses among locations and potential site-specific environmental changes likely tooccur in the future.
Keywords: common garden; community structure; dispersal; genetic diversity; local adaptation; managed relocationplant; productivity; provenance; restoration; seed transfer zone; tallgrass

Sensitivity of grassland plant community composition to spatial vs. temporal variation in precipitation - Cleland, E.E.; Scott. L. Collins; Dickson, T.L.; Farrer, E.C.; Gross, K.L.; Gherardi, L.A.; Hallett, L.M.; Hobbs, R.J.; Hsu, J.S.; K.N. Suding; Turnbull, L. (Ecology, 2013)
Climate gradients shape spatial variation in the richness and composition of plant communities. Given future predicted changes in climate means and variability, and likely regional variation in the magnitudes of these changes, it is important to determine how temporal variation in climate influences temporal variation in plant community structure. Here, we evaluated how species richness, turnover, and composition of grassland plant communities responded to interannual variation in precipitation by synthesizing long-term data from grasslands across the United States. We found that mean annual precipitation (MAP) was a positive predictor of species richness across sites, but a positive temporal relationship between annual precipitation and richness was only evident within two sites with low MAP. We also found higher average rates of species turnover in dry sites that in turn had a high proportion of annual species, although interannual rates of species turnover were surprisingly high across all locations. Annual species were less abundant than perennial species at nearly all sites, and our analysis showed that the probability of a species being lost or gained from one year to the next increased with decreasing species abundance. Bray-Curtis dissimilarity from one year to the next, a measure of species composition change that is influenced mainly by abundant species, was insensitive to precipitation at all sites. These results suggest that the richness and turnover patterns we observed were driven primarily by rare species, which comprise the majority of the local species pools at these grassland sites. These findings are consistent with the idea that short-lived and less abundant species are more sensitive to interannual climate variability than longer-lived and more abundant species. We conclude that, among grassland ecosystems, xeric grasslands are likely to exhibit the greatest responsiveness of community composition (richness and turnover) to predicted future increases in interannual precipitation variability. Over the long term, species composition may shift to reflect spatial patterns of mean precipitation; however, perennial-dominated systems will be buffered against rising interannual variation, while systems that have a large number of rare, annual species will show the greatest temporal variability in species composition in response to rising interannual variability in precipitation.

Small-scale patch structure in North American and South African grasslands responds differently to grazing and fire - Koerner, S.E.; Scott. L. Collins (Landscape Ecology, 2013)
Fire and grazing significantly impact small-scale patch structure and dynamics in savanna grasslands. We assessed small-scale grass-forb associations in long-term fire and grazing experiments in North America (NA) and Southern Africa (SA). Transects of 128 0.25 m2 contiguous quadrats were sampled in areas with different combinations of grazing (ungrazed, single grazer, or multiple grazers) and fire frequency (unburned or annually burned). We predicted that (1) the patch structure of each of the dominant grasses in NA and SA would respond similarly to fire and grazing, and (2) that forb richness would be correlated to grass patch structure. Semi-variance analysis was used to determine patch structure of dominant grasses and forb cover. Community structure responded similarly in NA and SA to fire, grazing, and fire-grazing interactions. Species richness, diversity, and community heterogeneity were significantly higher in unburned-grazed sites. Grazing significantly increased forb cover and decreased cover of the dominant grasses, and the effects of fire on community structure depended on the grazing regime. Contrary to our prediction, we found that small-scale patch structure of the dominant grass species in NA and SA responded differently to grazing and fire. We found strong grass patch structure in unburned-ungrazed grasslands in both sites; however, grazing and fire reduced patch structure in NA but not SA, and in no instance did grass patch structure influence forb community structure. We conclude that fire and grazing have larger impacts on small-scale patch structure in NA than they do in SA even though overall community structure responded similarly on both continents.
Keywords: Dominance-diversity; Grass-forb interaction; heterogeneity; Konza Prairie; Kruger National Park; Semi-variance

Spatial connectedness of plant species: potential links for apparent competition via plant diseases - Cox, C.M.; Bockus, W.W.; Holt, R.D.; Fang, L.; Garrett, K.A. (Plant Pathology, 2013)
This study evaluated the reactions of seven common C4 grasses of the tallgrass prairie of the USA Great Plains to the economically important wheat pathogens Pyrenophora tritici-repentis and Gaeumannomyces graminis var. tritici (Ggt) isolated from wheat. The P. tritici-repentis isolates (race 1) were pathogenic on all grasses tested, but symptom severity was markedly low. Three of the grass species inoculated with Ggt were highly susceptible, while four species exhibited no symptoms. Because measures of connectedness can provide a proxy for population processes, connectedness was evaluated within and among the seven grass species in representative tallgrass prairie environments for all potential pathogen-sharing patterns. Andropogon gerardii was ubiquitous, so all plant species were well connected to it. Andropogon scoparius (= Schizachyrium scoparium), Sorghastrum nutans and Panicum virgatum were fairly common but specialized to particular environments. Bouteloua curtipendula was uncommon but occurred in all environments, while Buchloë dactyloides and Bouteloua gracilis were uncommon and only occurred in upland sites. Co-occurrence of plant species was generally not reciprocal in that, for many species pairs, species A rarely occurred without potential exposure to inoculum from species B, while species B commonly occurred without species A. The three grass species susceptible to Ggt may act as sources of inoculum for each other within tallgrass prairie, with the potential to influence fitness, and tallgrass prairie and commercial wheat ecosystems in the Great Plains also have the potential to share both pathogens.
Keywords: agriculture–wildlands interface; biofuel crops; graph theory; networks; pathogen spill-over; switchgrass

Spatial heterogeneity in habitat selection: nest site selection by Greater Prairie-Chickens - McNew, L.B.; Gregory, A.J.; Sandercock, B.K. (Journal of Wildlife Management, 2013)
Ecological relationships of animals and their environments are known to vary spatially and temporally across scales. However, common approaches for evaluating resource selection by animals assume that the processes of habitat selection are stationary across space. The assumption that habitat selection is spatially homogeneous may lead to biased inference and ineffective management. We present the first application of geographically weighted logistic regression to habitat selection by a wildlife species. As a case study, we examined nest site selection by greater prairie-chickens at 3 sites with different ecological conditions in Kansas to assess whether the relative importance of habitat features varied across space. We found that 1) nest sites were associated with habitat conditions at multiple spatial scales, 2) habitat associations across spatial scales were correlated, and 3) the influence of habitat conditions on nest site selection was spatially explicit. Post hoc analyses revealed that much of the spatial variability in habitat selection processes was explained at a regional scale. Moreover, habitat features at local spatial scales were more strongly associated with nest site selection in unfragmented grasslands managed intensively for cattle production than they were in fragmented grasslands within a matrix of farmland. Female prairie-chickens exhibited spatial variability in nest site selection at multiple spatial scales, suggesting plasticity in habitat selection behavior. Our results highlight the importance of accounting for spatial heterogeneity when evaluating the ecological effects of habitat components. © 2013 The Wildlife Society.
Keywords: geographically weighted regression (GWR); greater prairie-chicken; Habitat selection; nest site selection; resource selection function (RSF); Tympanuchus cupido

Temperature dependant shifts in phenology contribute to the success of exotic species with climate change - Wolkovich, E.M.; Davies, T.J.; Schaefer, H.; Cleland, E.E.; Cook, B.I.; Travers, S.E.; Willis, C.G.; Davis, C.C. (American Journal of Botany, 2013)
• Premise of the study: The study of how phenology may contribute to the assembly of plant communities has a long history in ecology. Climate change has brought renewed interest in this area, with many studies examining how phenology may contribute to the success of exotic species. In particular, there is increasing evidence that exotic species occupy unique phenological niches and track climate change more closely than native species. • Methods: Here, we use long-term records of species’ first flowering dates from five northern hemisphere temperate sites (Chinnor, UK and in the United States, Concord, Massachusetts; Fargo, North Dakota; Konza Prairie, Kansas; and Washington, D.C.) to examine whether invaders have distinct phenologies. Using a broad phylogenetic framework, we tested for differences between exotic and native species in mean annual flowering time, phenological changes in response to temperature and precipitation, and longer-term shifts in first flowering dates during recent pronounced climate change (“flowering time shifts”). • Key results: Across North American sites, exotic species have shifted flowering with climate change while native species, on average, have not. In the three mesic systems, exotic species exhibited higher tracking of interannual variation in temperature, such that flowering advances more with warming, than native species. Across the two grassland systems, however, exotic species differed from native species primarily in responses to precipitation and soil moisture, not temperature. • Conclusions: Our findings provide cross-site support for the role of phenology and climate change in explaining species’ invasions. Further, they support recent evidence that exotic species may be important drivers of extended growing seasons observed with climate change in North America.
Keywords: flowering time; introduced species; invasion biology; non-native species; North American prairies; plant phenology; temperate grasslands

Temporal dynamics of plant community regeneration sources during tallgrass prairie restoration - Willand, J.E.; S.G. Baer; D.J. Gibson; Klopf, R.P. (Plant Ecology, 2013)
Ecological restoration aims to augment and steer the composition and contribution of propagules for community regeneration in degraded environments. We quantified patterns in the abundance, richness, and diversity of seed and bud banks across an 11-year chronosequence of restored prairies and in prairie remnants to elucidate the degree to which the germinable seed bank, emerged seedlings, belowground buds, and emerged ramets were related to community regeneration. There were no directional patterns in the abundance, richness, or diversity of the germinable seed bank across the chronosequence. Emerged seedling abundance of sown species decreased during restoration. Richness and diversity of all emerged seedlings and non-sown emerged seedling species decreased across the chronosequence. Conversely, abundance and richness of belowground buds increased with restoration age and belowground bud diversity of sown species increased across the chronosequence. Numbers of emerged ramets also increased across the chronosequence and was driven primarily by the number of graminoid ramets. There were no temporal changes in abundance and richness of sown and non-sown emerged ramets, but diversity of sown emerged ramets increased across the chronosequence. This study demonstrates that after initial seeding, plant community structure in restored prairies increasingly reflects the composition of the bud bank.
Keywords: chronosequence; Community assembly; diversity; Propagules; Species richness

Variance in mating success does not produce strong sexual selection in a polygynous songbird - Sousa, B. F.; Westneat, D. F. (Behavioral Ecology, 2013)
The sexually dimorphic ornaments and songs of birds are generally thought to be the result of sexual selection. For some time, variation in dimorphism among taxa was attributed to differences in social mating patterns. However, extrapair mating provides an alternative mechanism for sexual selection in both monogamous and polygynous birds. In monogamous systems, extrapair mating typically increases variance in mating success and hence sexual selection. However, it is less clear how extrapair mating influences sexual selection in polygynous species. We measured sexual selection acting on 6 sexually dimorphic male traits in a polygynous songbird, the dickcissel (Spiza americana). We also examined patterns of association between social and extrapair mating success, between male traits and reproductive success within each mating context, and the contribution of each type of mating to overall reproductive success. Despite high variance in both mating success and male traits, we found no evidence for current sexual selection in dickcissels. Indeed, variance among males in dimorphic traits did not significantly contribute to male success in any mating context. These results add to an array of studies uncovering relatively weak sexual selection in polygynous species. It is possible that, in contrast to monogamous systems, extrapair paternity weakens sexual selection in polygynous systems. In addition, natural selection arising from high predation and interspecific brood parasitism, stochastic processes, or annual variation in selective pressures may also weaken sexual selection in this species.

Variation in root system traits among African semi-arid savanna grasses: implications for drought tolerance - D.C. Hartnett; Ott, J.P.; G.T. Wilson; Setshogo, M. (Austral Ecology, 2013)
In arid to semi-arid grasslands and savannas, plant growth, population dynamics, and productivity are consistently and strongly limited by soil water and nutrient availability. Adaptive traits of the root systems of grasses in these ecosystems are crucial to their ability to cope with strong water and/or nutrient limitation and the increasing drought stress associated with ecosystem degradation or projected climate change. We studied 18 grass species in semi-arid savanna of the Kalahari region of Botswana to quantify interspecific variation in three important root system traits including root system architecture, rhizosheath thickness and mycorrhizal colonization. Drought-tolerant species and shorter-lived species showed greater rhizosheath thickness and fine root development but lower mycorrhizal colonization compared to later successional climax grasses and those characteristic of wetter sites. In addition, there was a significant positive correlation between root fibrousness index and rhizosheath thickness among species and a weak negative correlation between root fibrousness index and mycorrhizal colonization. These patterns suggest that an extensive fine root system and rhizosheath development may be important complementary traits of grasses coping with drought conditions, the former aiding in the acquisition of water by the grass plant and the latter aiding in water uptake and retention, and reducing water loss in the rhizosphere. Within species, both rhizosheath development and mycorrhizal colonization were significantly greater in a wet year than in a year with below-average precipitation. The observed patterns suggest that the primary benefit of rhizosheath development in African savanna grasses is improved drought tolerance and that it is a plastic trait that can be adjusted annually to changing environmental conditions. The functioning of mycorrhizal symbiosis is likely to be relatively more important in infertile savannas where nutrient limitation is higher relative to water limitation.
Keywords: grass; mycorrhiza; rhizosheath; root architecture; savanna

Woody vegetation removal stimulates riparian and benthic denitrification in tallgrass prairie - Reisinger, A.J.; John M. Blair; C. W. Rice; W. K. Dodds (Ecosystems, 2013)
Expansion of woody vegetation into areas that were historically grass-dominated is a significant contemporary threat to grasslands, including native tallgrass prairie ecosystems of the Midwestern United States. In tallgrass prairie, much of this woody expansion is concentrated in riparian zones with potential impacts on biogeochemical processes there. Although the effects of woody riparian vegetation on denitrification in both riparian soils and streams have been well studied in naturally wooded ecosystems, less is known about the impacts of woody vegetation encroachment in ecosystems that were historically dominated by herbaceous vegetation. Here, we analyze the effect of afforestation and subsequent woody plant removal on riparian and benthic denitrification. Denitrification rates in riparian soil and selected benthic compartments were measured seasonally in naturally grass-dominated riparian zones, woody encroached riparian zones, and riparian zones with woody vegetation removed in two separate watersheds. Riparian soil denitrification was highly seasonal, with the greatest rates in early spring. Benthic denitrification also exhibited high temporal variability, but no seasonality. Soil denitrification rates were greatest in riparian zones where woody vegetation was removed. Additionally, concentrations of nitrate, carbon, and soil moisture (indicative of potential anoxia) were greatest in wood removal soils. Differences in the presence and abundance of benthic compartments reflected riparian vegetation, and may have indirectly affected denitrification in streams. Riparian soil denitrification increased with soil water content and NO3 −. Management of tallgrass prairies that includes removal of woody vegetation encroaching on riparian areas may alter biogeochemical cycling by increasing nitrogen removed via denitrification while the restored riparian zones return to a natural grass-dominated state.
Keywords: denitrification; nitrogen removal; prairie streams; riparian vegetation; tallgrass prairie; woody encroachment

Applying soil ecological knowledge to restore ecosystem services - S.G. Baer; Heneghan, L.; Eviner, V. (Soil Ecology and Ecosystem Services, 2012)
Ecological restoration is human-facilitated improvement of a degraded environment. This chapter synthesizes the relevance of soil ecological knowledge to restoration along a continuum of ecosystem degradation and in the context of novel ecosystems. At one end of the continuum, mining can result in severe soil degradation and contamination with metals. Restoration of mined sites often focuses on decontamination, and success can be affected by soil heterogeneity, organic matter content, and refugia for soil biota that possess biodegradation pathways. Former agricultural sites can exhibit a wide range of soil and ecosystem legacies, with restoration goals ranging from simply reducing erosion with perennial plants to establishing a suite of historic ecosystem attributes and services through the re-introduction of many species. Although recovery of soil structure and function can coincide with plant establishment, knowledge of soil processes and plant–soil feedbacks have been applied to promote resource heterogeneity and plant diversity, and to reduce non-native species in restored agricultural systems. Even in relatively undisturbed sites with high legacy of native plants and soil, invasions of undesirable species may occur. Restoration of invaded systems may necessitate knowledge of how invaders impact resource availability and capture, as well as potentially complex multi-trophic interactions and feedbacks with soil. Last, restoration of novel ecosystems with new and self-sustaining assemblages of plant species in no-analog environments may require sophisticated consideration of biogeochemistry, plant population and community dynamics, and soil ecology to reintroduce and sustain native species long extirpated from local environments.
Keywords: agriculture; Invasive species; mining; novel ecosystem; plant–soil feedback; restoration; soil ecological knowledge

Arbuscular Mycorrhizae and Grassland Ecosystems - Miller, R.M.; G.T. Wilson; Johnson, N.C. (Biocomplexity of Plant-Fungal Interactions, 2012)

Bud bank demography: Density of native grass meristems as a predictor of rangeland invasibility - West, R. (Oklahoma State University, 2012)

Changes in stomatal conductance along grass blades reflect changes in leaf structure - Ocheltree, T.W.; Jesse B. Nippert; Prasad, P.V.V. (Plant Cell and Environment, 2012)
Identifying the consequences of grass blade morphology (long, narrow leaves) on the heterogeneity of gas exchange is fundamental to an understanding of the physiology of this growth form. We examined acropetal changes in anatomy, hydraulic conductivity and rates of gas exchange in five grass species (including C3 and C4 functional types). Both stomatal conductance and photosynthesis increased along all grass blades despite constant light availability. Hydraulic efficiency within the xylem remained constant along the leaf, but structural changes outside the xylem changed in concert with stomatal conductance. Stomatal density and stomatal pore index remained constant along grass blades but interveinal distance decreased acropetally resulting in a decreased path length for water movement from vascular bundle to stomate. The increase in stomatal conductance was correlated with the decreased path length through the leaf mesophyll. A strong correlation between the distance from vascular bundles to stomatal pores and stomatal conductance has been identified across species; our results suggest this relationship also exists within individual leaves.

Characterizing prevalence and ecological impact of non-native terrestrial isopods (Isopoda, Oniscidea) in tallgrass prairie - Singer, C.L.; Bello, N.M.; Snyder, B.A. (Crustaceana, 2012)
Isopods are terrestrial crustaceans whose role and impact in the tallgrass prairie ecosystem remains little explored despite being rather prevalent non-native inhabitants. To better understand this role, we conducted two related studies. The first was a rapid survey of isopods in experimental treatments at Konza Prairie LTER site to investigate the diversity and relative abundance of isopod species present. Of the four species known in Kansas thus far, all non-native, Armadillidium vulgare (Latreille, 1804) was the most abundantly found, accounting for 93% of individuals found. Armadillidium nasatum Budde-Lund, 1885, Cylisticus convexus (De Geer, 1778) and Porcellionides pruinosus (Brandt, 1833) were also found and we report the first record of Porcellio laevis Latreille, 1804 in the State of Kansas. Survey results showed no evidence for a relationship between isopod abundance and fire frequency or grazing treatment. The second experiment was a food preference study to explore granivory in non-native isopods and characterize their seed predator behavior on native plants. Individual isopods were placed in Petri dishes with food options including leaf litter and seeds from one of 15 species; dishes were then incubated for 6-12 days and preference was assessed based on pre- and post-trial weights of the feed and individual isopod. Isopods showed a significant preference for leaves compared to seeds in nine of the 15 seed species evaluated; no evidence for leaf-vs.-seed preference was apparent in the remaining six seed species. However, in all cases, isopods did consume some amount of seeds even when leaf litter was present. Taken together, the relatively low abundance of non-native terrestrial isopods and their lack of apparent preference for native plant seeds suggest that isopods are unlikely to pose considerable threat to tallgrass prairie ecosystems. More extensive research, including a preference study with greater representation of seed species and a quantitative survey throughout the year, would be needed to further characterize the ecological role of isopods in the tallgrass prairie.

Climate change alters growing season flux dynamics in mesic grasslands - Petrie, M.D.; N. Brunsell; Jesse B. Nippert (Theoretical and Applied Climatology, 2012)
Changing climate could affect the functioning of grassland ecosystems through variation in climate forcings and by altering the interactions of forcings with ecological processes. Both the short and long-term effects of changing forcings and ecosystem interactions are a critical part of future impacts to ecosystem ecology and hydrology. To explore these interactions and identify possible characteristics of climate change impacts to mesic grasslands, we employ a low-dimensional modeling framework to assess the IPCC A1B scenario projections for the Central Plains of the United States; forcings include increased precipitation variability, increased potential evaporation, and earlier growing season onset. These forcings are also evaluated by simulations of vegetation photosynthetic capacity to explore the seasonal characteristics of the vegetation carbon assimilation response for species at the Konza Prairie in North Central Kansas, USA. The climate change simulations show decreases in mean annual soil moisture and and carbon assimilation and increased variation in water and carbon fluxes during the growing season. Simulations of the vegetation response show increased variation at the species-level instead of at a larger class scale, with important heterogeneity in how individual species respond to climate forcings. Understanding the drivers and relationships behind these ecosystem responses is important for understanding the likely scale of climate change impacts and for exploring the mechanisms shaping growing season dynamics in grassland ecosystems.
Keywords: ecohydrology; Konza Prairie; Low-dimensional modeling; Nonlinear interactions; Soil moisture feedback

Comment on "Global Resilience of Tropical Forest and Savanna to Critical Transitions" - Z. Ratajczak; Jesse B. Nippert (Science, 2012)
Hirota et al. (Reports, 14 October 2011, p. 232) used spatial data to show that grasslands, savannas, and forests represent opposing stable states. Reanalyzing their data and drawing from temporal studies, we argue that spatial analyses underestimate the bistability of grasslands and savannas due to limitations of substituting space for time. We propose that temporal and spatial data are needed to predict critical transitions between grasslands and savannas.

Community stability does not preclude ecosystem sensitivity to chronic resource alteration - Alan K. Knapp; J. M. Briggs; M.D. Smith (Functional Ecology, 2012)

Community traitscape of foliar nitrogen isotopes reveals N availabiity patterns in a tallgrass prairie - Craine, J.M.; Towne, E.G.; Ocheltree, T.W.; Jesse B. Nippert (Plant and Soil, 2012)
Background and aims Nutrients are important determinants of community assembly, yet the roles they play in structuring plant communities are still poorly understood. One inferential approach to understanding how environmental factors structure plant communities is examining the distribution of key functional traits among species of a community—a community traitscape. Methods To better understand how nitrogen (N) and water availability structure grasslands, we measured N concentrations and isotope ratios for 366 herbaceous species in a mesic N-limited temperate grassland, Konza Prairie. We also compared foliar N concentrations and N isotopes between Konza species and a global dataset. Results Species that had either high foliar N concentrations or high δ15NL were not necessarily more or less abundant on the landscape nor more or less likely to be found in uplands, grazed areas, or burned areas. Apparently there are unique hot spots of high N availability at Konza and the typical non-Fabaceae Konza species occupies sites with greater N availability than found globally. Conclusions Although nascent, the Konza traitscapes suggest that plant diversity in nutrient-limited communities might be strongly dependent on high-nutrient availability sites that enable high-fertility species to persist in a matrix of low nutrient availability.
Keywords: Community assembly; disturbance; Grasslands; Isotopes; Konza Prairie; Resource limitation

Comparison of eggshell porosity and estimated gas flux between the brown-headed cowbird and two common hosts - Jaeckle, W.B.; Kiefer, M.; Childs, B.; Harper, R.G.; Rivers, J.W.; Peer, B.D. (Journal of Avian Biology, 2012)
The brown-headed cowbird Molothrus ater is a brood-parasite that lays eggs in nests of a wide range of host species, including the closely-related red-winged blackbird Agelaius phoeniceus and the dickcissel Spiza americana. Although cowbird eggs have accelerated development and hatch sooner than similar-sized host eggs, this development takes place within a thickened eggshell that could impede gas flux to the developing embryo. We tested the hypothesis that the accelerated development of the cowbird embryo relative to hosts is enabled by an increase in eggshell porosity that allows increased fluxes of respiratory gases to and from the developing embryo. We found cowbird eggshell thickness was significantly greater than the eggshells of these two common hosts. Although the number of pores per egg was similar among all three species, the total pore area per egg in cowbirds was significantly greater than that of either host, despite having a smaller eggshell surface area than the red-winged blackbird. Cowbird egg pore area was 1.9×larger than that of the red-winged blackbird. Cowbird eggshells had a significantly greater gas flux than those of the red-winged blackbird and the dickcissel. When conductance was normalized to published values of egg mass, cowbird eggs had a higher mass-specific conductance than red-winged blackbird or dickcissel eggs. These results are consistent with the hypothesis that the rapid development of brown-headed cowbird embryos is facilitated by increased eggshell porosity, and that changes in eggshell porosity represent an adaptation that enables cowbird eggs to hatch earlier than equivalently-sized host eggs.

Contrasting bud bank dynamics of two co-occurring grasses in tallgrass prairie: implications for grassland dynamics - Ott, J.P.; D.C. Hartnett (Plant Ecology, 2012)
Because most shoot recruitment in perennial grasses occurs from belowground axillary buds, bud dynamics determine plant population dynamics and meristem limitation to population growth. Therefore, grassland vegetation responses to environmental change or disturbance may be influenced by interspecific differences in bud banks and the patterns and environmental controls of bud development and demography. We examined bud bank dynamics in Andropogon gerardii and Dichanthelium oligosanthes in tallgrass prairie by enumerating and classifying buds throughout 15 months to determine whether grass buds live for multiple years and accumulate; whether bud natality, dormancy and outgrowth are synchronous or variable; and whether bud bank dynamics differ between these co-occurring species. Andropogon gerardii (a C4 species) maintained a larger dormant bud bank, showed synchrony in bud development and transition to tiller, and its buds lived for multiple years. Thus, multiple previous years’ bud cohorts contributed to recruitment. By contrast, D. oligosanthes (a C3 species) maintained a smaller dormant bud bank, had asynchronous bud development with active buds present year-round, and its buds lived for 1 year. Buds played different roles in the dynamics of each species, allowing A. gerardii to over-winter and recruit new spring tillers and D. oligosanthes to survive and recruit new tillers following summer dormancy. These differences in bud bank age structure, phenology, and dynamics between these species suggest greater demographic buffering and time-lag effects in A. gerardii populations. Interspecific differences in bud bank structure and dynamics may explain and help predict grassland responses to environmental change.
Keywords: Meristem; Photosynthetic pathway; Plant demography; Plant population dynamics; Tiller recruitment; Vegetative reproduction

Controls on bud activation and tiller initiation in C3 and C4 tallgrass prairie grasses: the role of light and nitrogen - Williamson, M.; G.T. Wilson; D.C. Hartnett (Botany, 2012)
Population dynamics of perennial grasses in tallgrass prairie ecosystems are strongly influenced by vegetative outgrowth from their belowground bud banks. We examined the role of light and nitrogen in regulating tiller initiation and tested an integrated model of controls on bud dormancy and activation in several C3 and C4 grasses. In addition, we assessed the interaction of nitrogen and light quantity and red – far red spectral composition on tiller initiation. Belowground perennating organs of three C3 and three C4 species were grown under full light or dark conditions, amended with one of four nitrogen concentrations (0 to 350 ppm N). Dormant buds were also subjected to full light under different spectral compositions or to continuous darkness. Our results among C3 grasses support the integrated model as light and nitrogen played important and interacting roles in the regulation of bud banks. However, differences in responses among C4 grasses and a lack of light × nitrogen interactions suggest that an alternative model may be necessary for this functional group. Our results provide predictions of responses to nitrogen enrichment or light imitations in prairie ecosystems due to interacting disturbances such as reduction in fire frequencies, alterations in grazing intensities, or climate change.
Keywords: bud banks; C3 grasses; C4 grasses; perennial grasses; Tiller recruitment; Vegetative reproduction

Controls on Soil Organic Carbon Stocks and Turnover Among North American Ecosystems - Frank, Douglas A.; Pontes, Alyssa W.; McFarlane, Karis J. (Ecosystems, 2012)

Coping with herbivory at the juvenile stage: Responses to defoliation and browsing in the African savanna tree Colophospermum mopane - D.C. Hartnett; Ott, J.P.; Sebes, K.; Ditlhogo, M. (Journal of Tropical Ecology, 2012)
Responses of plants to herbivory are dependent on the type of damage and the ontogenetic stage of the plant. We compared the effects of stem pruning and defoliation on seedlings of Colophospermum mopane, an ecologically important tree species widely distributed in southern Africa. The growth of 160 greenhouse-grown juveniles were measured for 6-mo after germination and then 6-mo after treatments including 50% defoliation, 100% defoliation, 50% stem pruning and controls. Pruning resulted in 30% reductions in total leaf area, height and biomass. Partial defoliation resulted in 30% reductions in total leaf area and plant biomass. However, complete defoliation resulted in a 30% increase in biomass production, a doubling in leaf and lateral branch number, a 45% reduction in leaf size, and no change in total leaf area. Thus, completely defoliated seedlings showed greater performance than those that were only partially defoliated, indicating that C. mopane has become adapted to the chronic and severe defoliation inflicted by Imbrasia belina caterpillars. Comparison of our results with other studies indicates that C. mopane seedlings are less herbivory-tolerant than adults and that pruning has more negative effects than defoliation. Thus, seedling browsers may constrain recruitment in C. mopane, influencing its population dynamics and abundance.
Keywords: Botswana; browsing; defoliation; Herbivory; Plant–herbivore interactions; savanna; seedlings; tree recruitment

Demography of Greater Prairie-Chickens: regional variation in vital rates, sensitivity values, and population dynamics - McNew, L.B.; Gregory, A.J.; Wisely, S.M.; Sandercock, B.K. (Journal of Wildlife Management, 2012)
Intensification of rangeland management has coincided with population declines among obligate grassland species in the largest remaining tallgrass prairie in North America, although causes of declines remain unknown. We modeled population dynamics and conducted sensitivity analyses from demographic data collected for an obligate grassland bird that is an indicator species for tallgrass prairie, the greater prairie-chicken (Tympanuchus cupido), during a 4-year study in east-central Kansas, USA. We examined components of reproductive effort and success, juvenile survival, and annual adult female survival for 3 populations of prairie-chickens across an ecological gradient of human landscape alteration and land use. We observed regional differences in reproductive performance, survivorship, and population dynamics. All 3 populations of prairie-chickens were projected to decline steeply given observed vital rates, but rates of decline differed across a gradient of landscape alteration, with the greatest declines in fragmented landscapes. Elasticity values, variance-scaled sensitivities, and contribution values from a random-effects life-table response experiment all showed that the finite rate of population change was more sensitive to changes in adult survival than other demographic parameters in our declining populations. The rate of population change was also sensitive to nest survival at the most fragmented and least intensively grazed study site; suggesting that patterns of landscape fragmentation and land use may be affecting the relative influences of underlying vital rates on rates of population growth. Our model results indicate that 1) populations of prairie-chickens in eastern Kansas are unlikely to be viable without gains from immigration, 2) rates of population decline vary among areas under different land management practices, 3) human land-use patterns may affect the relative influences of vital rates on population trajectories, and 4) anthropogenic effects on population demography may influence the regional life-history strategies of a short-lived game bird. © 2012 The Wildlife Society.
Keywords: contributions; elasticity; land use and land cover change (LULCC); Leslie matrix; life-table response experiment (LTRE); population viability; prospective analysis; variance-scaled sensitivities

Dimensions of diversity and their direct and indirect effects on tallgrass prairie ecosystem functioning - Chang, C.C. (Yale University, 2012)
Understanding the role of biological diversity to ecosystem function in ecological communities is particularly important now in the face of unprecedented, human-driven global change. Anthropogenic impacts such as climate change, nitrogen deposition, and land-use changes that modify natural disturbance regimes and promote the introduction of invasive species are all altering environmental conditions in such a way as to impact both diversity and ecosystem functioning. Diversity can be described in several ways and until recently, most research has focused on the relationship between the number and diversity of species and ecosystem function. Recently however, there has been a growing focus on the importance of genetic diversity within a dominant species and its impact on community and ecosystem processes. In this dissertation, I examine the relationship between community and population diversity, evaluate how diversity at both levels is maintained under varying environmental conditions, and test the relative effects of population and community level diversity on ecosystem function. First, I utilized a long-term experimental burn manipulation to examine the impact of fire frequency on genetic diversity of the dominant species and assessed the relationship between genetic diversity of the dominant species, species diversity, and productivity across the entire fire gradient. Genetic diversity of the dominant species was highest in a four year burn cycle and lowest in an annual and two year burn cycle. However, there was not a significant relationship between genetic and species diversity or between genetic diversity of the dominant species and productivity across the disturbance Gradient. In the second and third study, I explored in further detail the relationship between genetic diversity of the dominant species, species diversity, and evaluate the direct and indirect effects of both levels of diversity on productivity and invasion resistance. Contrary to expectations, genetic diversity of the dominant species did not have a direct effect on invasion resistance or productivity. Rather the effects of diversity at both the community and population level are primarily indirect via traits. Genetic differences between naturally co-occurring genotypes of the perennial dominant grass species were more subtle, and thus also highlighted the necessity of conducting studies in intact communities with naturally co-occurring individuals. Finally, to tease apart the possible mechanisms for how diversity within the population is maintained and subsequently impacts community and ecosystem processes, I conducted a pairwise competition experiment with the four most common genotypes of the dominant species and manipulated light, water, and nitrogen resources. Phenotypic differences between genotypes resulted in different competitive successes depending on resource conditions. Some genotypes were able to take advantage of increased water or nitrogen resources under low and high light conditions, providing evidence for niche complementarity. There was evidence that some genotypes were more antagonistic under low versus high resource conditions while other genotypes were more synergistic. This differential success in resource acquisition, biomass accumulation, and subsequent competitive ability translated to variation in vegetative reproductive success, which has implications for the population dynamics of this perennial, primarily asexually reproductive, dominant C4 grass. Together the results from these four studies suggest that the roles of population and community level diversity are complex in intact, natural tallgrass prairie where diversity effects on ecosystem function may be primarily indirect via traits.

Dissolved organic matter in headwater streams: compositional variability across climatic regions of North America - Jaffé, R.; Yamashita, Y.; Maie, N.; Cooper, W.T.; Dittmar, T.; W. K. Dodds; Jones, J.B.; Myoshi, T.; Ortiz-Zayas, J.R.; Podgorski, D.C.; Watanabe, A. (Geochimica et Cosmochimica Acta, 2012)
Dissolved organic matter (DOM) represents the largest organic matter pool in freshwater systems, but much of it remains molecularly uncharacterized. Although freshwater systems cover only a small area of the earth’s surface, inland waters are an important component of the global carbon cycle. The traditional idea that rivers are simply conduits for refractory carbon delivery to coastal areas is inconsistent with carbon flux estimates, and streams have been shown to serve as reactors for DOM cycling. The overall quality of DOM, and its associated reactivity, can be related to its chemical composition and molecular structure. However, the variability of DOM composition in freshwater ecosystems, particularly in headwater streams, is poorly characterized. Detailed molecular studies of DOM from small streams across climatic regions, which could provide critical information regarding carbon dynamics on a more global scale, have not been performed. To address these issues, this study applies a multi-method analytical approach in an attempt to assess molecular characteristics of DOM and ultrafiltered DOM (UDOM) in headwater streams from different climatic regions in North America. In general terms the chemical and molecular characteristics of UDOM from six different biomes were determined in unsurpassed detail to feature some clear general similarities but also specific differences. While the degree of similarity is remarkable, and suggests similar source strengths, such as soil-derived organic matter and/or similar diagenetic degradation processes for DOM from vastly different environments, each sample was clearly unique in its overall composition, featuring some distinct molecular patterns for at least one or more of the analytical determinations. Molecular and compositional differences of DOM from headwater streams should result from variations in DOM sources and localized environmental conditions, and consequently feature different photo- and bio-reactivity and associated re-mineralization potentials during fluvial transport. Such knowledge could assist in predicting the consequences of global change and its relationship to global carbon cycling.

Drought-mediated stem and belowground bud dynamics in restored grasslands - Carter, D.L.; Vanderweide, B.; John M. Blair (Applied Vegetation Science, 2012)
Question Does the below-ground bud bank mediate response to drought in restored grasslands? Location Platte River Valley region of south-central Nebraska, USA. Methods We imposed severe drought for one growing season using rainfall manipulation structures and measured the response of above- and below-ground plant communities (ramet and below-ground bud densities) with respect to non-drought controls during the drought year and a recovery year. Results Drought reduced below-ground bud bank density and above-ground stem density. However, bud bank density recovered, and bud production was higher on previously droughted subplots relative to controls in the year following drought. The response of below-ground bud and above-ground stem density to drought differed according to functional identity (C3 grass, C4 grass, and forb), with forbs least resistant to, but having the greatest recovery from, drought. Conclusions While overall density in restored grasslands was resilient, drought effects on below-ground bud banks may have longer-term impacts on plant community structure. Reduced density above- or below-ground during the growing season following drought may allow for the persistence of species relatively more reliant on recruitment from seed banks in favourable micro-sites.
Keywords: Below-ground; Climate change; Community; forb; grass; Lag; Meristem; plant; prairie; Rainfall manipulation

Ecology of mating patterns and sexual selection in dickcissels breeding in managed prairie - Sousa, B.F. (University of Kentucky, 2012)
Males of many species have elaborate phenotypes that are absent in females and that are thought to be the result of sexual selection. Sexual selection requires: (i) variance in male mating success, (ii) variation in male phenotype, and (iii) covariation between male mating success and male phenotype. Environmental conditions influence these factors, and management practices that alter environmental conditions have the potential to shape mating patterns and sexual selection. I investigated the hypothesis that the frequency of fire, used to manage tallgrass prairie, affects the mating patterns and process of sexual selection in the organisms breeding in managed prairies. I studied dickcissels (Spiza americana), a small songbird resident in tallgrass prairie. I first examined mating patterns and sexual selection in dickcissels independent of burning regime. I found variation among males in the number of mates attracted, in the number of offspring sired with each mate, and the offspring sired with the mates of other males. I found a positive association between social mates and siring success, but no evidence for an effect of breeding density or synchronous nesting on mating success. Male dimorphic traits, size, song, and plumage, showed between-individual variation but selection gradients were weak and often fluctuated between the years of study. I next examined patterns of mating success in plots burned on a variable schedule. I found little evidence that burning influenced either the mean or the variance in social mating success, paternity, or male phenotype. Burning regime also had no influence on sexual selection gradients with the single exception of selection on tarsus length. Temporal variation was more important for patterns of mating success and sexual selection gradients on male traits than was burning regime. The demography of dickcissels in the breeding season suggests, however, that habitat management on a larger scale may be more influential. My findings extend our understanding of sexual selection in birds and the effects of management on the factors required for sexual selection and the magnitude of selection.

Ecotypic responses of switchgrass to altered precipitation - Hartman, J.C.; Jesse B. Nippert; Springer, C.J. (Functional Plant Biology, 2012)
Anthropogenic climate change is projected to alter precipitation patterns, resulting in novel environments for plants. The responses of dominant plant species (e.g. Panicum virgatum L. (switchgrass)) to climate changes can drive broader ecosystem processes such as primary productivity. Using a rainfall mesocosm facility, three ecotypes of P. virgatum (collected from Kansas, Oklahoma and Texas, USA) were subjected to three precipitation regimes (average, –25%, +25%) to determine the physiological and growth responses to altered precipitation in a common garden setting. Results showed mean maximum photosynthetic rates, stomatal conductance, transpiration, midday water potential and dark-adapted chlorophyll fluorescence were lowest in the Kansas ecotypes. Increased precipitation treatments raised the mean midday water potentials and lowered water-use efficiency. Aboveground biomass responded positively to changes in precipitation, but flowering initiation was later and rates were lower for Texas ecotypes. In general, ecotype origin was a better predictor of differences in physiological responses and flowering, whereas the precipitation treatments had greater control over biomass production. Depending on the growth variable measured, these results show responses for P. virgatum are under varying ecotypic or environmental control with few interactions, suggesting that future predictions to climate change need not inherently consider localised adaptations in this economically important and widely distributed species.

The effect of experimental warming and precipitation change on proteolytic enzyme activity: positive feedbacks to nitrogen availability are not universal - Brozostek, E.R.; John M. Blair; Dukes, J.S.; Frey, S.D.; Hobbie, S.E.; Melillo, J.M.; Mitchell, R.J.; Pendall, E.S.; P.B. Reich; Shaver, G.R.; Stefanskii, A.; Tjoelker, M.G.; et al. (Global Change Biology, 2012)
Nitrogen regulates the Earth's climate system by constraining the terrestrial sink for atmospheric CO2. Proteolytic enzymes are a principal driver of the within-system cycle of soil nitrogen, yet there is little to no understanding of their response to climate change. Here, we use a single methodology to investigate potential proteolytic enzyme activity in soils from 16 global change experiments. We show that regardless of geographical location or experimental manipulation (i.e., temperature, precipitation, or both), all sites plotted along a single line relating the response ratio of potential proteolytic activity to soil moisture deficit, the difference between precipitation and evapotranspiration. In particular, warming and reductions in precipitation stimulated potential proteolytic activity in mesic sites – temperate and boreal forests, arctic tundra – whereas these manipulations suppressed potential activity in dry grasslands. This study provides a foundation for a simple representation of the impacts of climate change on a central component of the nitrogen cycle.

The effect of precipitation events on inorganic carbon in soil and shallow groundwater, Konza Prairie LTER Site, NE Kansas, USA - Tsypin, M.; G. L. Macpherson (Applied Geochemistry, 2012)
Monthly sampling for 1 year at the Konza Prairie LTER (Long-Term Ecological Research) Site in northeastern Kansas shows a connection between the annual cycles of CO2 in soil air and shallow groundwater DIC (dissolved inorganic C). Soil air CO2 reached 6–7% in July to mid-August, when moisture was not limiting to soil respiration. Following the annual maximum there was a sequential decrease in CO2 in three soil horizons to less than 0.5% because of moisture deficiency in the late summer and temperature decline in the fall and winter. Groundwater pCO2 reached its maximum of 5% in October; the lag-time of 2–3 months may correspond to the travel time of soil-generated CO2 to the water table. The time-variable CO2 caused an annual carbonate-mineral saturation cycle, intensifying limestone dissolution and DIC production when CO2 was high. The C flux depended on respiration and rainfall regimes, and had two main pathways. Transport of soil CO2 in the dissolved form with diffuse flow of recharge water was the most effective during the growing season so long as soil moisture was present. Downward movement of gaseous CO2 and equilibration with groundwater at the water table was favorable in July to August. Storm rainfall events recharged the aquifer within a few hours through preferential flow and stream–groundwater interaction, resulting in dilution of groundwater rather than forcing entrapped CO2 downward. Calculated C flux from the unsaturated zone to the unconfined aquifer in the monitoring period was 0.26 ± 0.03 M/m2/a of C, which is less than 1% of the CO2 that is released by soil to the atmosphere via efflux. However, meteoric precipitation was only 72% of average annual precipitation during the study period, so this study represents dry-condition flux. In addition, increased respiration rates due to warming of the atmosphere have the potential to cause a higher C flux to the saturated zone, intensifying weathering and groundwater acidification, so that further study is suggested.

Effects of fire, grazing and topographic variation on vegetation structure in tallgrass prairie - Scott. L. Collins; Calabrese, L.B. (Journal of Vegetation Science, 2012)
Questions How do fire and grazing by bison affect the composition and structure of tallgrass prairie plant communities and their temporal stability? Are these responses modulated by topographic location? Location Konza Prairie Biological Station, Kansas, USA. Methods Plant community composition was monitored in permanent plots in native grassland sites receiving different long-term prescribed burning and bison grazing regimes across a topographic gradient (lowlands, slopes, uplands) following 20 yr of variable burning treatments and 13 yr of grazing by bison. A combination of multivariate analyses was used to determine how community structure, life forms and individual species responded to the accumulated effects of long-term fire and grazing by native bison in upland, slope and lowland soils. Results Species diversity was maximized in sites that were infrequently burned and grazed by bison with the strongest response on infrequently burned slope sites, while diversity was lowest on frequently burned ungrazed sites and on frequently burned slope sites. In general, grass cover was highest in infrequently burned ungrazed sites and lowest on frequently burned grazed sites, while forb richness was highest in infrequently burned and grazed sites. Community response to fire and grazing differed across the topographic gradient. In general, frequent burning favoured C4 grasses, which reduced the abundance of C3 forbs, especially in lowland sites. Responses of dominant grasses and forbs to fire and grazing varied depending on topographic position. Community stability was positively correlated with species richness. Conclusions Overall, we found that fire and grazing are the main determinants of plant community composition and structure in this grassland system, but that topography mediates these effects. A combination of bison grazing and periodic fire is necessary to maximize diversity and community stability across this native grassland landscape.
Keywords: disturbance; fire; grassland; Grazing; Plant community structure; Species diversity

Effects of foundation species genotypic diversity on subordinate species richness in an assembling community - D.J. Gibson; Alstadt, A.J.; S.G. Baer; Geisler, M. (Oikos, 2012)
Foundation (dominant or matrix) species play a key role in structuring plant communities, influencing processes from population to ecosystem scales. However, the effects of genotypic diversity of foundation species on these processes have not been thoroughly assessed in the context of assembling plant communities. We modified the classical filter model of community assembly to include genotypic diversity as part of the biotic filter. We hypothesized that the proportion of fit genotypes (i.e. competitively superior and dominant) affects niche space availability for subordinate species to establish with consequence for species diversity. To test this hypothesis, we used an individual-based simulation model where a foundation species of varying genotypic diversity (number of genotypes and variability among genotypes) competes for space with subordinate species on a spatially heterogeneous lattice. Our model addresses a real and practical problem in restoration ecology: choosing the level of genetic diversity of re-introduced foundation and subordinate species. Genotypic diversity of foundation species significantly affected equilibrium community diversity, measured as species richness, either positively or negatively, depending upon environmental heterogeneity. Increases in genotypic diversity gave the foundation species a wider niche breadth. Under conditions of high environmental heterogeneity, this wider niche breadth decreased niche space for other species, lowering species richness with increased genotypic diversity until the genotypes of the foundation species saturated the landscape. With a low level of environmental heterogeneity, increasing genotypic diversity caused the foundation species niche breadth to be overdispersed, resulting in a weak positive relationship with species richness. Under these conditions, some genotypes are maladapted to the environment lowering fitness of the foundation species. These effects of genotypic diversity were secondary to the larger effects of overall foundation species fitness and environmental heterogeneity. The novel aspect of incorporating genotype diversity in combination with environmental heterogeneity in community assembly models include predictions of either positive or negative relationships between species diversity and genotypic diversity depending on environmental heterogeneity, and the conditions under which these factors are potentially relevant. Mechanistically, differential niche availability is imposed by the foundation species.

Effects of rangeland management on the site occupancy dynamics of prairie-chickens in a protected prairie preserve - McNew, L.B.; Prebyl, T.J.; Sandercock, B.K. (Journal of Wildlife Management, 2012)
We investigated the site occupancy dynamics of greater prairie-chickens at Konza Prairie Biological Station, a protected site in northeastern Kansas that is managed for ecological research. We surveyed the site during mid-Mar to mid-May, 1981–2008, and recorded detections of birds in a grid of 6.3 ha survey plots (n = 187 plots). We used multiseason occupancy models to estimate the probabilities of occupancy (ψ) and detection (p), and tested whether land cover in woody vegetation, and land use with prescribed fire or grazing management influenced the dynamic processes of site colonization and local extinction. Probability of detection per site was consistently <1 and varied among years (p = 0.12–0.82). Site occupancy of prairie-chickens declined 40% over the study period from a high of ψ = 0.19 ± 0.02 SE in 1981 to a low of 0.11 ± 0.03 in 2008, despite protection from disturbance at leks and losses to harvest. We found that different sets of environmental factors impacted the probabilities of colonization and local extinction. Probability of colonization for an unoccupied site was negatively associated with the proportion of site occupied by woodland cover (β = −1.25), and was lower for grazed sites (β = −0.62). In contrast, probability of local extinction was affected by a weak interaction between grazing and average frequency of prescribed fire (β = −1.01), but model-averaged slope coefficients were not statistically different than 0. To conserve prairie-chickens, we recommend prairies be managed with combinations of prescribed fire and grazing that maintain a heterogeneous mosaic of prairie habitats, while preventing woody encroachment. To assess biotic responses to land management practices, field sampling should be based on occupancy models or similar techniques that account for imperfect detection. © 2011 The Wildlife Society.
Keywords: colonization; detection probabilities; greater prairie-chicken; Kansas; Konza Prairie Biological Station; local extinction; occupancy modeling; Tympanuchus cupido

The expansion of woody riparian vegetation, and subsequent stream restoration, influences the metabolism of prairie streams - Riley, A.J.; W. K. Dodds (Freshwater Biology, 2012)
1. Tallgrass prairies and their streams are highly endangered ecosystems, and many remaining streams are threatened by the encroachment of woody riparian vegetation. An increase in riparian vegetation converts the naturally open-canopy prairie streams to closed-canopy systems. The effects of a change in canopy cover on stream metabolism are unknown. 2. Our goal was to determine the effects of canopy cover on prairie stream metabolism during a 4-year period in Kings Creek, KS, U.S.A. Metabolic rates from forested reaches were compared to rates in naturally open-canopy reaches and restoration reaches, the latter having closed canopies in 2006 and 2007 and open canopies in 2008 and 2009. Whole-stream metabolism was estimated using the two-station diurnal method. Chlorophyll a concentrations and mass of filamentous algae were measured after riparian removal to assess potential differences in algal biomass between reaches with open or closed canopies. 3. Metabolic rates were spatially and temporally variable even though the sites were on very similar streams or adjacent to each other within streams. Before riparian vegetation removal, whole-stream community respiration (CR) and net ecosystem production were greater with greater canopy cover. In the vegetation removal reaches, gross primary production was slightly greater after removal. 4. Chlorophyll a concentrations were marginally significantly greater in open (naturally open and removal reaches) than in closed canopy and differed significantly between seasons. Filamentous algal biomass was greater in open than in closed-canopy reaches. 5. Overall, the restoration allowed recovery of some features of open-canopy prairie streams. Woody expansion apparently increases CR and moves prairie stream metabolism towards a more net heterotrophic state. An increase in canopy cover decreases benthic chlorophyll, decreases dominance of filamentous algae and potentially alters resources available to the stream food web. The results of this study provide insights for land managers and conservationists interested in preserving prairie streams in their native open-canopy state

Flowering phenology as a functional trait in a tallgrass prairie - Craine, J.M.; Wolkovich, E.M.; Towne, E.G.; Kembel, S.W. (New Phytologist, 2012)
•The timing of flowering is a critical component of the ecology of plants and has the potential to structure plant communities. Yet, we know little about how the timing of flowering relates to other functional traits, species abundance, and average environmental conditions. •Here, we assessed first flowering dates (FFDs) in a North American tallgrass prairie (Konza Prairie) for 431 herbaceous species and compared them with a series of other functional traits, environmental metrics, and species abundance across ecological contrasts. •The pattern of FFDs among the species of the Konza grassland was shaped by local climate, can be linked to resource use by species, and patterns of species abundance across the landscape. Peak FFD for the community occurred when soils were typically both warm and wet, while relatively few species began flowering when soils tended to be the driest. Compared with late-flowering species, species that flowered early had lower leaf tissue density and were more abundant on uplands than lowlands. •Flowering phenology can contribute to the structuring of grassland communities, but was largely independent of most functional traits. Therefore, selection for flowering phenology may be independent of general resource strategies.

Genetic diversity of Andropogon gerardii: Impacts of altered precipitation patterns on a dominant species - M.L. Avolio (Yale University, 2012)
Global change is expected to shift climatic regimes and cause whole communities of organisms to experience novel environments. Key aspects of forecast climate change are alterations in both the amount of precipitation and the variability of precipitation regimes. The ability of a population to adapt will depend on the genetic diversity of the population, and the traits of the genotypes present in the population. Here, I assess the response a dominant C4 tallgrass population to novel environmental conditions resulting from forecast climate change by studying whether more variable precipitation patterns affect the genetic diversity of Andropogon gerardii. I then investigate the potential mechanisms driving the observed response. Ultimately, the way in which population genetic diversity is affected by more variable precipitation patterns will shed insight into how this important species will adapt to future climate change. First, I developed the tools to study the genetic diversity of A. gerardii at the plant neighborhood scale, the scale at which individuals compete for resources. I designed amplified fragment length polymorphism primers for A. gerardii and determined the appropriate scale at which to sample individuals to accurately capture genetic diversity. I also examined how genetic diversity is measured in ecological studies by comparing genotype-based measures and genome-based measures of diversity. Ultimately, I argue that genome-based measures should be included in future studies alongside genotypic-based measures because they capture a greater spectrum of genetic differences among individuals. Next, using what I established for studying genetic diversity, I examined how a decade of altered precipitation patterns affected the genetic diversity of A. gerardii. To do this I worked within the Rainfall Manipulation Plots (RaMPs) experiment at Konza Prairie Biological Station in Kansas, which experimentally imposes ambient and more variable precipitation patterns. After ten years of experimentally increased intra-annual variability in growing season precipitation regimes, I report that the number of genotypes of the dominant C4 grass, Andropogon gerardii Vitman, has been significantly reduced in native tallgrass prairie compared with unmanipulated prairie. However, individuals showed a different pattern of genomic similarity with increased precipitation variability – there was greater genome dissimilarity among individuals when compared to unmanipulated prairie. In my next two chapters, I aim to understand the mechanism that drove the observed shift in genetic diversity. First, I studied phenotypic differences among six common genotypes of Andropogon gerardii across three different environmental conditions to study genotype × environmental interactions. I consistently detected differences among the focal genotypes for all traits measured across environmental treatments, however, I observed no genotype × year interactions, and phenotypic differences among genotypes were diminished within environmental conditions. To assess potential mechanisms underlying the changes observed in population structure of this species, I continued to study five of the same genotypes, three of which had greater abundances or were only present in plots receiving more variable rainfall patterns. In a greenhouse study, I investigated how both changes in the size and variability of watering events affected ecophysiological, growth, biomass allocation and fitness traits. I found genotype × water amount interactions for traits related to leaf level physiology and biomass allocation; genotypes that performed better under low soil moisture conditions were outperformed by other genotypes under high soil moisture conditions. For the three genotypes that had greater abundance in plots that received a decade of altered rainfall regimes, I found evidence of phenotypic trait divergence as well as greater plasticity for ecophysiological traits. Lastly, I investigated correlations between species and genetic diversity in tallgrass prairie across an experimental manipulation of soil moisture. I found species and genetic diversity were not correlated, and that genotypic richness was negatively related to soil moisture variability, but measures of species diversity were not related to soil moisture. My results suggest that a lack relationship between species and genetic diversity at the populations scale could be because species and genetic diversity are responding differently to environmental resources. Ultimately, my dissertation is an in-depth examination of how environmental conditions affect the genetic diversity of a dominant species. I found that for genetically diverse species, such as dominant species, microevolution might be an important aspect of adaptation to novel environmental conditions experienced with climate change.

Growth and survival during drought: The link between hydraulic architecture and drought tolerance in grasses - Ocheltree, T.W. (Kansas State University, 2012)
The pathway for the movement of water through plants, from the soil matrix to the atmosphere, constitutes the hydraulic architecture of a plant. The linkage between the hydraulic architecture of woody plants and drought tolerance has received considerable attention, but much less work has been done on grasses. I investigated the linkage between the hydraulic architecture of grasses to physiological patterns of water use across a range of species and conditions. The rate of stomatal conductance (g[subscript]s) and photosynthesis (A) increased acropetally along the leaves of 5 grass species, which is a unique feature of this growth form. The internal structure of leaves also changed acropetally in order to minimize the pressure gradient across the mesophyll that would otherwise occur as a result of increasing g[subscript]s. The resistance to water movement through the mesophyll represented 80-90% of leaf resistance in six genotypes of Sorghum bicolor L. (Moench). This resistance was most important in controlling g[subscript]s and A when water was readily available, but as soil-moisture decreased it was the efficient transport of water through the xylem that was most important in maintaining plant function. I also investigated the relationship between hydraulic architecture and stomatal responses of grasses to increasing Vapor Pressure Deficit (D). Grasses with a larger proportion of their hydraulic resistance within the xylem were less sensitive to increasing D and plants with high root conductance maintained higher rates of gas exchange D increased. Finally, I investigated the tolerance of grasses to extreme drought events to test if there was a trade-off between drought tolerance and growth in grasses. Plants with drought tolerant leaf traits typically sacrificed the ability to move water efficiently through their leaves. Having drought tolerant leaves did not limit the plants ability to have high rates of gas exchange, and, in fact, the most drought tolerant plants had the high rates of g[subscript]s when expressed on a mass basis. Leaf-level drought tolerance did contribute to species’ occurrence, as the drought intolerant species I studied are not commonly found in low precipitation systems. The results presented here highlight the importance of studying the hydraulic architecture of plants to provide a better understanding of what controls plant function across a range of environmental conditions.
Keywords: Drought Tolerance; Grass Anatomy; Grass Physiology; Plant Hydraulic Architecture; Stomatal Conductance

High levels of relatedness between Brown-headed Cowbird (Molothrus ater) nestmates in a heavily parasitized host community - Rivers, J.W.; Young, S.; Gonzalez, E.G.; Horton, B.; Lock, J.; Fleisher, R.C. (The Auk, 2012)
Multiple parasitism of host nests by generalist brood parasites reflects the decisions of laying females and may influence the development and behavior of parasitic young. We used microsatellite and mtDNA control-region haplotype data to examine the relatedness of Brown-headed Cowbird (Molothrus ater) offspring in multiply parasitized nests sampled from a heavily parasitized host community in northeastern Kansas. We also examined how host nest availability influenced the degree of multiple parasitism, and used community-wide parasitism data to explore whether female cowbirds were constrained in their laying decisions. Relatedness estimates for all suitable pairwise comparisons (n = 94 from 41 multiply parasitized nests) found that the mean likelihood than an individual cowbird in a multiply parasitized nest shared its nest with a full sibling was 40.4% (95% confidence interval: 28.4–52.4%), indicating that many cowbird offspring were reared with full siblings. Extensive community-wide parasitism data revealed that most cowbird offspring shared the nest with ≥1 other conspecific. Additionally, we found that the proportion of available host nests increased steeply at the start of the breeding season and remained high for most of the breeding season, but that the degree of multiple parasitism was unrelated to the number of new nests. We found evidence that laying decisions of female cowbirds were constrained, which suggests that heavy parasitism levels were due to a high degree of competition for host nests. This intense competition for host nests, in turn, results in cowbird offspring often competing with conspecifics in our population, including full siblings, for host parental care.
Keywords: brown-headed cowbird; generalist brood parasite; kinship; laying pattern; Molothrus ater; nestmate relatedness

High richness and dense seeding enhance grassland restoration establishment, but have little effect on drought response - Carter, D.L.; John M. Blair (Ecological Applications, 2012)
Restorations commonly utilize seed addition to formerly arable lands where the development of native plant communities is severely dispersal limited. However, variation in seed addition practices may profoundly affect restoration outcomes. Theory and observations predict that species-rich seed mixtures and seeding at high densities should enhance native plant community establishment, minimize exotic species cover, and may promote resistance and resilience to, and recovery from, environmental perturbations. We studied the post-seeding establishment of native plant communities in large grassland restoration plots, which were sown at two densities crossed with two levels of species richness on formerly arable land in Nebraska, USA, and their responses to drought. To evaluate drought resistance, recovery, and resilience of restored plant communities, we erected rainfall manipulation structures and tracked the response of seeded species cover and total plant biomass during experimental drought relative to controls and in the post-drought growing season. High seed richness and high-density seeding treatments resulted in greater richness and cover of native, seeded species per 0.5 m2 compared to low-richness and low-density treatments. Cover differences in response to seed mixture richness were driven by native forbs. Richness and cover of exotic species were lowest in high-richness and high-density treatments. We found little evidence of differential drought resistance, recovery, and resilience among seeding treatments. Increases in exotic species across years were restricted to drought subplots, and were not affected by seeding treatments. Grassland restoration was generally enhanced and exotic cover reduced both by the use of high-richness seed mixtures and high-density seeding. Given the lack of restoration treatment effects on the resistance, recovery, or resilience of seeded species exposed to drought, and the increases in exotic species following drought, other forms of active management may be needed to produce restored plant communities that are robust to climate change.

Higher-order bud production increases tillering capacity in the perennial caespitose grass Scribner's Panicum (Dichanthelium oligosanthes) - Ott, J.P.; D.C. Hartnett (Botany, 2012)
The persistence and dynamics of perennial grass populations strongly depend on tiller recruitment from the bud bank. Because of the structural organization of grasses as populations of phytomers, bud production and tillering are constrained by morphology. An infrequent trait observed in only a few caespitose grasses is the branching of buds to produce higher-order buds prior to tiller development. We studied bud bank dynamics in Dichanthelium oligosanthes (Schult.) Gould a C3 perennial caespitose grass widely distributed in the eastern Great Plains. A hierarchy of bud development occurred in D. oligosanthes, with primary buds branching to produce secondary, tertiary, and quaternary buds. This higher-order bud production increased the overwintering propagule supply for spring recruitment by 4.5 times, and more than half of successful tiller recruits originated as higher-order buds. The temporal patterns of higher-order bud production and development suggest that growing season length may be an important factor determining the extent of higher-order bud production and subsequent year tiller natality in D. oligosanthes. Higher-order bud production likely has important consequences for the population dynamics of grasses. It may increase bud bank densities and tillering capacity, buffer population dynamics, and increase intraclonal tiller densities and resource consolidation in caespitose grasses.
Keywords: Bud bank; bunchgrass; Dichanthelium oligosanthes; tillering

Hispid pocket mice in tallgrass prairie: abundance, seasonal activity, habitat association, and individual attributes - Kaufman, G.A.; Kaufman, D.M. (Western North American Naturalist, 2012)
Hispid pocket mice (Chaetodipus hispidus) are found from the grasslands of the Great Plains to the deserts of the southwestern United States, but the natural history and ecology of this species have not been described in native tallgrass prairie at the eastern edge of its range. We initiated an ongoing long-term study of small mammals on Konza Prairie Biological Station, Kansas (a Long-Term Ecological Research [LTER] site), in autumn 1981. Our sampling scheme for 14 LTER sites was a 20-station trapline; small mammals were sampled in autumn and spring for 30 years and in summer for a shorter period. We combined data for these sites with those from shorter studies on Konza Prairie that used traplines and trapping grids. We recorded only 96 hispid pocket mice over the 30 years of study (>300,000 trap-nights overall). Pocket mice were more likely to be captured in autumn and summer than in spring. The earliest annual capture was on 20 March and the latest on 7 December; males emerged from torpor in spring before females, whereas females entered torpor later in autumn. Precipitation (January—September) had a tight limiting effect on maximal number of individuals that were present in autumn. Pocket mice were more common on slope prairie than on upland or lowland prairie, but burning and grazing had no effect. Their spatiotemporal distribution showed a slightly “anti-nested” pattern with only weakly preferred sites and no focal years that might indicate favorable conditions. Collectively, our data suggested the presence of 3 age classes when individual body masses (no differences between males and females) were plotted against capture date. Finally, our study illustrates the importance of long-term data sets, especially in the study of uncommon to rare species.

Incorporating clonal growth form clarifies the role of plant height in response to nitrogen addition - Gough, L.; Gross, K.L.; Cleland, E.E.; Clark, C.M.; Scott. L. Collins; Fargione, J.E.; Pennings, S.C.; K.N. Suding (Oecologia, 2012)
Nutrient addition to grasslands consistently causes species richness declines and productivity increases. Competition, particularly for light, is often assumed to produce this result. Using a long-term dataset from North American herbaceous plant communities, we tested whether height and clonal growth form together predict responses to fertilization because neither trait alone predicted species loss in a previous analysis. Species with a tall-runner growth form commonly increased in relative abundance in response to added nitrogen, while short species and those with a tall-clumped clonal growth form often decreased. The ability to increase in size via vegetative spread across space, while simultaneously occupying the canopy, conferred competitive advantage, although typically only the abundance of a single species within each height-clonal growth form significantly responded to fertilization in each experiment. Classifying species on the basis of two traits (height and clonal growth form) increases our ability to predict species responses to fertilization compared to either trait alone in predominantly herbaceous plant communities.
Keywords: Clonal growth; Competition; grassland; Nitrogen addition; productivity

Influences of local adaptation and genome size on Panicum virgatum (switchgrass) responses to variable precipitation timing - O'Keefe, K. (St. Joseph's University, 2012)

Insect herbivore outbreaks views through a physiological framework: insights from Orthoptera - Behmer, S.T.; Anthony Joern (Insect Outbreaks Revisited, 2012)
Insect herbivore outbreaks, particularly orthopteran outbreaks, have plagued humans throughout recorded history. The Egyptian locust swarm described in the Old Testament is perhaps the most famous orthopteran outbreak story. Two species, the African desert locust (Schistocerca gregaria Forskål) and the migratory locust (Locusta migratoria (Linnaeus)), still outbreak regularly throughout large expanses of Africa and the Middle East. The most likely villain in the biblical swarm was the African desert locust, based on the broad array of the food plants described in the story. In contrast to the desert locust, the migratory locust is a specialist that feeds only on grasses. However, despite its restricted diet, the migratory locust has a larger geographic range, extending from all of northern and central Africa across to eastern China. It too has greatly impacted human society throughout historical time, especially in China. Parenthetically, the Chinese character for locust is composed of two parts, insect (虫) and emperor (皇); this character combination indicates the power of locusts – it was an insect capable of threatening an emperor’s supremacy. In China’s 5000-year history, 842 locust plagues have been recorded, with the earliest ones being described in the Book of Songs (770–476 BCE). How locust outbreaks endangered regimes and changed the destiny of China is also described in two other important ancient Chinese books – Zizhi Tongjian (which covers Chinese history from 403 BCE to 959 CE, including 16 dynasties) and Ch’ien Han Shu (which covers Chinese history from 206 BCE to 25 CE). Although the recorded histories of Australia and the Americas are more recent, orthopteran outbreaks have a long history on these continents as well. The first recorded outbreak of the Australian plague locust (Chortoicetes terminifera (Walker)) was in 1844, followed by outbreaks from the 1870s onward (including multiple outbreaks in the early 2000s, most of which were controlled by the Australian Plague Locust Commission (Hunter 2004)). In the United States, massive outbreaks of the Rocky Mountain locust (Melanoplus spretus (Walsh)) were recorded in the 1870s. The largest of the swarms covered a “swath equal to the combined areas of Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island and Vermont” (Riley et al. 1880), and nearly derailed westward expansion. Charles Valentine Riley, now considered one of the founding fathers of entomology in the United States, was appointed by the US government to investigate these outbreaks. His work led him to request further federal assistance, which the government provided in the form of the US Entomological Commission; this agency quickly morphed into the US Department of Agriculture that still operates today. The last known Rocky Mountain locust swarm occurred in the very early 1900s; why it disappeared remains a mystery, although some interesting hypotheses have been proposed (Lockwood 2005). The Mormon cricket (Anabrus simplex (Haldeman)) is another orthopteran species renowned for its outbreaks. Populations of Mormon crickets usually occur at low densities throughout most of their range in western North America, but population explosions that exceed more than 1 million individuals, marching in roving bands at densities of more than 100 individuals/m2 , are not uncommon. In 1848 a Mormon cricket outbreak nearly thwarted the settlement of Salt Lake City, Utah, by Mormon pioneers. Although the story is controversial, Mormon folklore recounts the miracle of the gulls. Legend claims that legions of seagulls, sent by God, appeared on June 9, 1848. These seagulls saved the settler’s crops by eating all the crickets. South America and Central America also have orthopterans that show outbreak dynamics, the most notable being Schistocerca cancellata (Serville) and Schistocerca piceifrons (Walker), respectively. Given the devastation and immense suffering inflicted on humans by orthopteran outbreaks, it is pressing to understand the causal factors that contribute to their outbreaks. With the exception of Mormon crickets (see Sword 2005), the orthopterans described above exhibit phase polyphenism – defined by Hardie and Lees (1985, 473) as “occurrence of two or more distinct phenotypes which can be induced in individuals of the same genotype by extrinsic factors.” The African desert locust and African migratory locust are easily two of the best-known species to practice phase polyphenism. However, many orthopterans that do not exhibit phase polyphenism can also undergo outbreaks, as has been the case for many grasshopper species in the western United States (Branson et al. 2006). In this chapter we concentrate primarily on orthopterans, but our aim is to understand factors that contribute to insect herbivore outbreaks more generally. We also discuss other types of insects, particularly lepidopterans, to make our points. Because insect outbreaks cannot happen without an initial increase in population size, we begin by focusing on individuals while considering factors, especially nutritional ones, that contribute to increased performance. We next explore how behavior and performance (e.g., survival, growth, and reproduction) of individual insect herbivores change as population densities increase. Shifting gears, we then discuss how ecological paradigms, particularly the “plant stress hypothesis,” have influenced how we view insect herbivore outbreaks. We conclude the chapter by calling for an integrative approach that translates individual responses into group-level phenomena, couched within the contexts of their communities and ecosystems.

Interspecific variation in bud banks and flowering effort among semi-arid African savanna grasses - Dalgleish, H.J.; Ott, J.P.; Setshogo, M.; Muzilla, M.; D.C. Hartnett (South African Journal of Botany, 2012)
Population viability and productivity of grasses in southern African savannas are dependent upon both successful seed production and tiller recruitment from the belowground bud bank. Relative recruitment rates from buds versus seeds influence population dynamics, genetic diversity, and patterns of vegetation productivity. We assessed patterns in bud bank size and flowering effort in fourteen semi-arid savanna grass species in the Kalahari region of Botswana. There was high inter-specific variability and between-year variability in flowering effort (percentage of tillers flowering). Bud production (number of buds per tiller) exhibited high inter-specific variability, but was more consistent between-years than flowering effort. Relative allocation to flowering versus bud production varied with life history, with longer-lived perennial grasses showing higher bud production and lower flowering effort relative to shorter-lived grasses. Several species showed higher bud production and lower flowering effort in a wet year compared to a dry year, and grass species that are regularly grazed maintained significantly larger bud banks than non-grazed species. These differential demographic responses among co-occurring species suggest that environmental change in semi-arid savannas may alter the composition, relative abundances and diversity of grasses, and that the maintenance of a belowground bud bank is an important factor influencing their resiliency, their capacity to recover from grazing and/or drought, and their persistence and sustainability under changing environmental conditions. Meristem-limitation in species that maintain few viable buds may constrain their population viability under changing conditions in semi-arid savannas.
Keywords: Bud bank; Meristem; Poaceae; Reproductive allocation; Vegetative reproduction

Invasion of an intact plant community: the role of population vs. community level diversity - Chang, C.C.; M.D. Smith (Oecologia, 2012)
To improve the understanding of how native plant diversity influences invasion, we examined how population and community diversity may directly and indirectly be related to invasion in a natural field setting. Due to the large impact of the dominant C4 grass species (Andropogon gerardii) on invasion resistance of tallgrass prairie, we hypothesized that genetic diversity and associated traits within a population of this species would be more strongly related to invasion than diversity or traits of the rest of the community. We added seeds of the exotic invasive C4 grass, A. bladhii, to 1-m2 plots in intact tallgrass prairie that varied in genetic diversity of A. gerardii and plant community diversity, but not species richness. We assessed relationships among genetic diversity and traits of A. gerardii, community diversity, community aggregated traits, resource availability, and early season establishment and late-season persistence of the invader using structural equation modeling (SEM). SEM models suggested that community diversity likely enhanced invasion indirectly through increasing community aggregated specific leaf area as a consequence of more favorable microclimatic conditions for seedling establishment. In contrast, neither population nor community diversity was directly or indirectly related to late season survival of invasive seedlings. Our research suggests that while much of diversity–invasion research has separately focused on the direct effects of genetic and species diversity, when taken together, we find that the role of both levels of diversity on invasion resistance may be more complex, whereby effects of diversity may be primarily indirect via traits and vary depending on the stage of invasion.
Keywords: Andropogon bladhii; dominant species; genetic diversity; grassland; tallgrass prairie

The invasive Lespedeza cuneata attracts more insect pollinators than native congeners in tallgrass prairie with variable impacts - Woods, T.M.; Jonas, J.L.; Ferguson, C.J. (Biological Invasions, 2012)
Invasive plant species can potentially exert competitive or facilitative effects on insect pollination services of native species. Factors that influence these effects include the degree of shared pollinator species, synchronous flowering phenology, similar flower morphology and color, relatedness of invasive and natives, and showiness and densities of flowers. We investigated such plant-pollinator dynamics by comparing the invasive Lespedeza cuneata and three native congeners, all sympatric with synchronous flowering, using in situ populations over 2 years during peak floral displays. Insect visitation rates of the invasive were significantly higher per plant in both years than on the native species. The invasive exerted a competitive effect on visitation of the two native species with fewer shared pollinators, and a facilitative effect on visitation of the native species with the highest degree of shared insect visitors. Positive correlations were found between floral density and visitation rate per plant in all the native species. Although no such correlation was found for the invasive, floral density in L. cuneata was at least twenty times higher than in the native species and likely saturated the response of the pollinator community. Analyses of insect visitor taxonomic data indicated the insect communities visiting each of the Lespedeza species were generally similar though with species-specific differences. The main exception was that the common honeybee, Apis mellifera, was a primary visitor to the invasive plant species, yet was never observed on the native Lespedeza species.
Keywords: Apis mellifera; Competition; Facilitation; Invasive; Lespedeza; Pollination

Invasive warm-season grasses reduce mycorrhizal root colonization and biomass production of native prairie grasses - G.T. Wilson; Hickman, K.R.; Williamson, M.M. (Mycorrhiza, 2012)
Soil organisms play important roles in regulating ecosystem-level processes and the association of arbuscular mycorrhizal (AM) fungi with a plant species can be a central force shaping plant species’ ecology. Understanding how mycorrhizal associations are affected by plant invasions may be a critical aspect of the conservation and restoration of native ecosystems. We examined the competitive ability of old world bluestem, a non-native grass (Caucasian bluestem [Bothriochloa bladhii]), and the influence of B. bladhii competition on AM root colonization of native warm-season prairie grasses (Andropogon gerardii or Schizachyrium scoparium), using a substitutive design greenhouse competition experiment. Competition by the non-native resulted in significantly reduced biomass production and AM colonization of the native grasses. To assess plant–soil feedbacks of B. bladhii and Bothriochloa ischaemum, we conducted a second greenhouse study which examined soil alterations indirectly by assessing biomass production and AM colonization of native warm-season grasses planted into soil collected beneath Bothriochloa spp. This study was conducted using soil from four replicate prairie sites throughout Kansas and Oklahoma, USA. Our results indicate that a major mechanism in plant growth suppression following invasion by Bothriochloa spp. is the alteration in soil microbial communities. Plant growth was tightly correlated with AM root colonization demonstrating that mycorrhizae play an important role in the invasion of these systems by Bothriochloa spp. and indicating that the restoration of native AM fungal communities may be a fundamental consideration for the successful establishment of native grasses into invaded sites.
Keywords: Arbuscular mycorrhizas; Big bluestemm; Bothriochloa bladhii; Bothriochloa ischaemum; Little bluestem; Old world bluestems; plant–soil feedback; tallgrass prairie; Warm-season grasses

An iPhone application of Konza Prairie LTER - Nukala, L.A. (Kansas State University, 2012)

Long-term ecological research in a human-dominated world - Robertson, G.P.; Scott. L. Collins; D.R. Foster; Brokaw, N.; Ducklow, H.W.; Gragson, T.L.; Gries, C.; Hamilton, S.K.; McGuire, A.D.; Moore, J.C.; Stanley, E.H.; Waide, R.B.; et al. (BioScience, 2012)
The US Long Term Ecological Research (LTER) Network enters its fourth decade with a distinguished record of achievement in ecological science. The value of long-term observations and experiments has never been more important for testing ecological theory and for addressing today's most difficult environmental challenges. The network's potential for tackling emergent continent-scale questions such as cryosphere loss and landscape change is becoming increasingly apparent on the basis of a capacity to combine long-term observations and experimental results with new observatory-based measurements, to study socioecological systems, to advance the use of environmental cyberinfrastructure, to promote environmental science literacy, and to engage with decisionmakers in framing major directions for research. The long-term context of network science, from understanding the past to forecasting the future, provides a valuable perspective for helping to solve many of the crucial environmental problems facing society today.
Keywords: coupled natural–human systems; cyberinfrastructure; environmental education; environmental observatories; socioecological systems

Long-term trends in ecological systems: a basis for understanding responses to global change. USDA Agriculture Research Service Publication, Technical Bulletin 1931. Washington, D.C - Peters, D.P.C.; Laney, C.M.; Lugo, A.E.; Scott. L. Collins; Driscoll, C.T.; Groffman, P.M.; Grove, J.M.; Alan K. Knapp; Kratz, T.K.; Ohman, M.D.; Waide, R.B.; Yao, J. (2012)
Peters, D.P.C., C.M. Laney, A.E. Lugo, et al. 2013. Long-Term Trends in Ecological Systems: A Basis for Understanding Responses to Global Change. U.S. Department of Agriculture, Technical Bulletin Number 1931. The EcoTrends Editorial Committee sorted through vast amounts of historical and ongoing data from 50 ecological sites in the continental United States including Alaska, several islands, and Antarctica to present in a logical format the variables commonly collected. This report presents a subset of data and variables from these sites and illustrates through detailed examples the value of comparing longterm data from different ecosystem types. This work provides cross-site comparisons of ecological responses to global change drivers, as well as longterm trends in global change drivers and responses at site and continental scales. Site descriptions and detailed data also are provided in the appendix section.
Keywords: atmospheric chemistry; Climate change; cross-site comparisons; disturbance; ecological response; ecology; ecosystem; EcoTrends; experimental forests; global change; human demography; human population growth; Long Term Ecological Research (LTER); long-term datasets; Precipitation; rangeland; rangeland research stations; surface water chemistry

Maternal allocation and offspring characteristics in Bison - Hamel, S.; Craine, J.M.; Towne, E.G. (Ecological Applications, 2012)
Parental allocation strategies are of profound interest in life history because they directly impact offspring fitness and therefore are highly valuable for understanding population dynamics and informing management decisions. Yet, numerous questions about reproductive allocation patterns for wild populations of large mammals remain unanswered because of the challenges for measuring allocation in the wild. Using a nine-year longitudinal data set on life-history traits of mother–calf bison pairs, we identified sources of variation in relative maternal allocation (calf mass ratio on mother mass) and assessed the occurrence of reproductive costs associated with differential maternal allocation. We found that heavy mothers provided a lower allocation but still produced heavier calves than light mothers. Older females produced lighter calves and tended to decrease allocation as they aged, supporting the occurrence of reproductive senescence. Mothers that had produced a calf the previous year produced lighter calves and allocated less than mothers that did not lactate the previous year, revealing reproductive costs. However, greater maternal allocation did not reduce the probability of breeding in successive years, and the amount of allocation provided by a mother was positively correlated among the offspring she produced, illustrating individual heterogeneity. Although life-history studies are usually classified as either supporting costs of reproduction or individual quality, our study demonstrates that these contrasting evolutionary forces can shape variation within a single trait. Our work illustrates that many processes can coevolve within a population, emphasizing the need to integrate multiple concepts to better understand the evolution of life-history traits. With regard to management of bison herds, if the goal of culling programs is to select for animals with the best performance, this research suggests that managers should account for the condition and previous reproductive status of mothers when taking culling decisions on juvenile bison.

Measuring genetic diversity in ecological studies - M.L. Avolio; Beaulieu, J.; Lo, E.; M.D. Smith (Plant Ecology, 2012)
There is an increasing interest in how genetic diversity may correlate with and influence community and ecosystem properties. Genetic diversity can be defined in multiple ways, and currently lacking in ecology is a consensus on how to measure genetic diversity. Here, we examine two broad classes of genetic diversity: genotype-based and genome-based measures. Genotype-based measures, such as genotypic richness, are more commonly used in ecological studies, and often it is assumed that as genotypic diversity increases, genomic diversity (the number of genetic polymorphisms and/or genomic dissimilarity among individuals) also increases. However, this assumption is rarely assessed. We tested this assumption by investigating correlations between genotype- and genome-based measures of diversity using two plant population genetic datasets: one observational with data collected at Konza Prairie, KS, and the other based on simulated populations with five levels of genotypic richness, a typical design of genetic diversity experiments. We found conflicting results for both datasets; we found a mismatch between genotypic and genomic diversity measures for the field data, but not the simulated data. Last, we tested the consequences of this mismatch and found that correlations between genetic diversity and community/ecosystem properties depended on metric used. Ultimately, we argue that genome-based measures should be included in future studies alongside genotypic-based measures because they capture a greater spectrum of genetic differences among individuals.
Keywords: Community diversity; Ecosystem function; Genome diversity; Phenotype; SGDC

Mechanisms driving woody encroachment in the tallgrass prairie: an analysis of fire behavior and physiological integration - Killian, P.D. (Kansas State University, 2012)
Woody encroachment has altered the vegetative structure of grasslands worldwide and represents a potentially irreversible shift in grassland dynamics and biodiversity. Clonal woody species appear to be one of the greatest contributors to the shift from graminoid to woody dominance in the tallgrass prairie. Part of the high success rate of clonal species may be attributed to an ability to circumvent recruitment filters through the integration of environmental heterogeneity and acropetal translocation of resources from mother to daughter ramets. The clonal shrub Cornus drummondii persists in a tension zone of the graminoid-dominated tallgrass prairie, where the dominance structure is primarily maintained through the direct and indirect effects of fire. The competitive displacement of native herbaceous vegetation associated with the establishment and expansion of C. drummondii causes a major alteration in the fuel dynamics responsible for the propagation and sustainment of fire, potentially contributing to biofeedback mechanisms that facilitate shrub expansion. The goal of this research was to quantify fire behavior parameters (temperature, intensity, rate of spread, and heat flux) in relation to C. drummondii invasions and to test physiological integration as a mechanism driving encroachment, using manipulation experiments at the Konza Prairie Biological Station. We observed a significant decrease in fireline intensity associated with the encroachment of C. drummondii, which was amplified by the effects of stem density and shrub island area. This alteration in fire behavior also led to reduced heat flux at stems within shrub islands, reducing the likelihood of tissue necrosis and top-kill. With additional fuel, temperatures and fire intensities were higher, similar to open grasslands. In severing rhizomes, and effectively severing the integration of clonal ramets, we observed a higher risk of mortality of daughter ramets. These rhizome severed ramets were more water stressed, had lower photosynthetic rates, and lower woody and foliar biomass production. These results indicate that C. drummondii significantly alters fire behavior, releasing ramets from the fire trap of successive top-killing, while the integration of intraclonal ramets allows daughter ramets to survive mid-summer drought and increases the likelihood of successful establishment and further clonal reproduction.
Keywords: Cornus drummondii; Fire behavior; Physiological integration; woody encroachment

Multiple factors limit use of local sites by Elliot's short-tailed shrews (Blarina hylophaga) in tallgrass prairie - Kaufman, G.A.; Matlack, R.S.; D.W. Kaufman; Higgins, J.J. (Canadian Journal of Zoology, 2012)
Spatial variation in abundance has been attributed to habitat heterogeneity and patchiness. Our goal in this research was to understand what factors were associated with spatial patterns of habitat use by Elliot’s short-tailed shrews (Blarina hylophaga Elliot, 1899) in tallgrass prairie. Our modeling efforts were based on 20 years (1981–2000) of presence–absence data for shrews at each of 20 stations (local site) along 14 permanent traplines on Konza Prairie Biological Station, Kansas, USA. A logistic model accurately predicted the presence of short-tailed shrews at a local site. Probability of shrew occurrence decreased as amount of precipitation decreased, slope steepness increased, grazing increased, or burned area within 500 m of a local site increased. However, when amount of precipitation was low, area burned was high, or grazing occurred, shrews were uncommon and responded little to the other variables. Numbers of shrews were negatively related only to numbers of deer mice (Peromyscus maniculatus (Wagner, 1845)), a mouse that selects burned and grazed habitats that shrews avoid. Our observations suggest that multiple environmental factors limit use of local sites, whereas competition with other species does not. Our results can inform decisions related to conservation of biodiversity given management practices in this endangered ecosystem.

A mycorrhizal community is unresponsive to simulated future precipitation variability - Tomeo, N.J. (St. Joseph's University, 2012)

Past, present, and future roles of long-term experiments in the LTER Network - Alan K. Knapp; M.D. Smith; Hobbie, S.E.; Scott. L. Collins; Fahey, T.J.; Hansen, G.J.A.; Landis, D.A.; Kimberly J. La Pierre; Melillo, J.M.; Seastedt, T.R.; Shaver, G.R.; Webster, J.R. (Bioscience, 2012)
The US National Science Foundation–funded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have (a) provided unique insights into ecological patterns and processes, although such insight often became apparent only after many years of study; (b) influenced management and policy decisions; and (c) evolved into research platforms supporting studies and involving investigators who were not part of the original design. Furthermore, this suite of long-term experiments addresses, at the site level, all of the US National Research Council's Grand Challenges in Environmental Sciences. Despite these contributions, we argue that the scale and scope of global environmental change requires a more-coordinated multisite approach to long-term experiments. Ideally, such an approach would include a network of spatially extensive multifactor experiments, designed in collaboration with ecological modelers that would build on and extend the unique context provided by the LTER Network.
Keywords: Climate change; global change; long-term research; LTER Network; multifactor experiments

Phylogenetics of Morus (Moraceae) inferred from ITS and trnL-trnF sequence data - Nepal, M.P.; Ferguson, C.J. (Systematic Botany, 2012)
Morus (Tribe Moreae, Moraceae) consists of ca. 13 species of trees distributed in Asia, Africa, Europe, and North, Central, and South America. The broad geographical distribution of the genus, overlapping ranges of many taxa, and documented hybridization between some species present interesting questions of taxonomy, phylogeny, and biogeography. Phylogenetic data for Morus also contribute to higher level taxonomic work in the family. We used sequence data from ITS of the nrDNA and the chloroplast trnL-trnF intergenic spacer to study phylogenetic relationships of Morus. Phylogenies based on separate data sets were not statistically incongruent, and the combined tree reveals that Morus, as currently circumscribed, is non-monophyletic. Subgenus Morus (sensu Leroy) is resolved as a clade and consists of two well-supported clades: one of Asian taxa and one of North American taxa. Sampled members of the genus Trophis (two, including the type) form a clade sister to subgenus Morus. Morus mesozygia (Africa; subgenus Afromorus) and M. insignis (Neotropics; subgenus Gomphomorus), which have not been included to date in other phylogenetic studies of the family, are placed outside the subgenus Morus-Trophis clade. This work is an important step in elucidating relationships of Morus and along with other recent phylogenetic studies in Moraceae, underscores the need for further work within Tribe Moreae to clarify natural generic relationships.
Keywords: ITS; Moraceae; Moreae; Morus; phylogeny; trnL-trnF

Plant and soil responses to high and low diversity grassland restoration practices - E.M. Bach; S.G. Baer; Six, J. (Environmental Management, 2012)
The USDA’s Conservation Reserve Program (CRP) has predominantly used only a few species of dominant prairie grasses (CP2 practice) to reduce soil erosion, but recently has offered a higher diversity planting practice (CP25) to increase grassland habitat quality. We quantified plant community composition in CP25 and CP2 plantings restored for 4 or 8 years and compared belowground properties and processes among restorations and continuously cultivated soils in southeastern Nebraska, USA. Relative to cultivated soils, restoration increased soil microbial biomass (P = 0.033), specifically fungi (P < 0.001), and restored soils exhibited higher rates of carbon (C) mineralization (P = 0.010). High and low diversity plantings had equally diverse plant communities; however, CP25 plantings had greater frequency of cool-season (C3) grasses (P = 0.007). Older (8 year) high diversity restorations contained lower microbial biomass (P = 0.026), arbuscular mycorrhizal fungi (AMF) biomass (P = 0.003), and C mineralization rates (P = 0.028) relative to 8 year low diversity restorations; older plantings had greater root biomass than 4 year plantings in all restorations (P = 0.001). Low diversity 8 year plantings contained wider root C:N ratios, and higher soil microbial biomass, microbial community richness, AMF biomass, and C mineralization rate relative to 4 year restorations (P < 0.050). Net N mineralization and nitrification rates were lower in 8 year than 4 year high diversity plantings (P = 0.005). We attributed changes in soil C and N pools and fluxes to increased AMF associated with C4 grasses in low diversity plantings. Thus, reduced recovery of AMF in high diversity plantings restricted restoration of belowground microbial diversity and microbially-mediated soil processes over time.
Keywords: Conservation reserve program; Nitrogen mineralization; Phospholipid fatty acids; Soil microbial community; tallgrass prairie

Predator-prey interactions in a grassland food chain vary with temperature and food quality - Laws, A.; Anthony Joern (Oikos, 2012)
Because species interactions are often context-dependent, abiotic factors such as temperature and biotic factors such as food quality may alter species interactions with potential consequences to ecosystem structure and function. For example, altered predator–prey interactions may influence the dynamics of trophic cascades, affecting net primary production. In a three-year field experiment, we manipulated a plant–grasshopper–spider food chain in mesic tallgrass prairie to investigate the effects of temperature and food quality on grasshopper performance, and to understand the direct and indirect tritrophic interactions that contribute to trophic cascades. Because spiders are active at cooler temperatures than grasshoppers in our system, we hypothesized that predator effects would be strongest in cooled treatments, and weakest in warmed treatments. Grasshopper spider interactions were highly context-dependent and varied significantly with food quality, temperature treatment and year. Spiders most often reduced grasshopper survival in the cooled and ambient temperature treatments, but had little to no effect on grasshopper survival in the warmed treatments, as hypothesized. In some years, plants compensated for grasshopper herbivory and trophic cascades were not observed despite significant effects of predators on grasshopper survival. However, in the year they were observed, trophic cascades only occurred in cooled treatments where predator effects on grasshoppers were strongest. Predicting ecosystem responses to climate change will require an understanding of how temperature influences species interactions. Our results demonstrate that changes in daily temperature regimes can alter predator–prey interactions among arthropods with consequences for ecosystem processes such as primary production and the relative importance of top–down and bottom–up processes.

Predicting plant responses to mycorrhizae: integrating evolutionary history and plant traits - Reinhart, K.O.; G.T. Wilson; Rinella, M.J. (Ecology Letters, 2012)
We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.

Recovery of native plant community characteristics on a chronosequence of restored prairies seeded into pastures in West-Central Iowa - Carter, D.L.; John M. Blair (Restoration Ecology, 2012)
Restored grasslands comprise an ever-increasing proportion of grasslands in North America and elsewhere. However, floristic studies of restored grasslands indicate that our ability to restore plant communities is limited. Our goal was to assess the effectiveness of restoration seeding for recovery of key plant community components on former exotic, cool-season pastures using a chronosequence of six restoration sites and three nearby remnant tallgrass prairie sites in West-Central Iowa. We assessed trends in Simpson's diversity and evenness, richness and abundance of selected native and exotic plant guilds, and mean coefficient of conservatism (mean C). Simpson's diversity and evenness and perennial invasive species abundance all declined with restoration site age. As a group, restoration sites had greater richness of native C3 species with late phenology, but lower richness and abundance of species with early phenology relative to remnant sites. Total native richness, total native abundance (cover), mean C, and abundance of late phenology C3 plants were similar between restoration and remnant sites. Observed declines in diversity and evenness with restoration age reflect increases in C4 grass abundance rather than absolute decreases in the abundance of perennial C3 species. In contrast to other studies, restoration seeding appears to have led to successful establishment of tallgrass prairie species that were likely to be included in seeding mixtures. While several floristic measures indicate convergence of restoration and remnant sites, biodiversity may be further enhanced by including early phenology species in seeding mixes in proportion to their abundance on remnant prairies.
Keywords: grassland; Invasive; mean C; phenology; succession; tallgrass

Response of regional sources of tallgrass prairie species to variation in climate and soil microbial communities - Goad, R.K. (Kansas State University, 2012)
Restoration of resilient plant communities in response to environmental degradation is a critical task, and a changing climate necessitates the introduction of plant communities adapted to anticipated future conditions. Ecotypes of dominant species can affect associated organisms as well as ecosystem function. The extent of ecotypic variation in dominant tallgrass prairie species and the consequences of this variation for ecosystem functioning were studied by manipulating two potential drivers of plant community dynamics: climate and the soil microbial community. Climate was manipulated indirectly through the use of reciprocal restorations across a rainfall gradient where regional sources of dominant grasses Andropogon gerardii and Sorghastrum nutans were seeded with 8 other native species that occur in tallgrass prairie. Four dominant grass sources (originating from central Kansas [CKS], eastern Kansas [EKS], southern Illinois [SIL], or a mixture of these) were reciprocally planted within four sites that occurred across a precipitation gradient in western KS (Colby, KS), CKS (Hays, KS), EKS (Manhattan, KS) and SIL (Carbondale, IL). The three grass sources and mixture of sources were sown into plots according to a randomized complete block design at each sites (n=16, 4 plots / block at each site). Aboveground net primary productivity (ANPP) was measured at the end of the 2010 and 2011 growing season at each site. In 2010, total ANPP declined from western to eastern Kansas, but increased across the geographic gradient in 2011. The dominant grasses did not comprise the majority of community ANPP in WKS, CKS or SIL in either year but did contribute most to total ANPP at the EKS site in 2011. In 2010, volunteer forbs comprised the largest proportion of ANPP in WKS, whereas and in both years planted forbs comprised the largest proportion of ANPP in SIL. Ecotypic variation in ANPP of A. gerardii was not evident, but Sorghastrum nutans ANPP exhibited a site by source effect in 2010 that did not suggest a home site advantage. Variation in the competitive environment at each site may have masked ecotypic variation during community assembly. Further, ANPP responses suggest that grasslands in early stages of establishment may respond more stochastically to climatic variation than established grasslands. Longer term studies will clarify whether ecotypes of dominant prairie grasses affect ecosystem function or community trajectories differently during restoration. Ecotypes of dominant species may support different soil microflora, potentially resulting in plant-soil feedback. A second experiment tested for local adaptation of prairie plant assemblages to their soil microbial community. Native plant assemblages from Kansas and Illinois were tested for local adaptation to their `home' soil by reciprocally crossing soil and plant source in a greenhouse experiment. Seeds and soil were obtained from two remnant prairies, one in eastern Kansas and one in central Illinois, with similar species composition but differing climate. Seeds of four species (Andropogon gerardii, Elymus canadensis, Lespedeza capitata, Oligoneuron rigidum) common to both locations were collected, germinated, and transferred to pots to create 4-species assemblages from each region. Non-prairie (NP) soil from the edge of an Illinois agricultural field was also included as an inoculum treatment to increase relevance to restoration. Kansas and Illinois plant assemblages were subjected to a fully factorial combination of soil inocula [with associated microbial communities] (3 sources: KS, IL, NP) and soil sterilization treatment (sterilized or live). Plants were harvested after 20 weeks and soil was analyzed for microbial composition using phospholipid fatty acid (PLFA) markers. Soil sources had different nutrient concentrations and sterilization resulted in a flush of NH4+, which complicated detection of soil microbial effects. However, plant sources did exhibit variation in productivity responses to soil sources, with Kansas plants more responsive to live soil sources than Illinois plants. Despite confounding variation in soil fertility, soil inoculation was successful at manipulating soil microbial communities, and plant sources responded differently to soil sources. Consideration of feedback between soil and plants may be a missing link in steering restoration trajectories.

The role of precipitation variability on the ecohydrology of grasslands - Petrie, M.D.; N. Brunsell (Ecohydrology, 2012)
Precipitation event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating landscape heterogeneity. Ecosystems respond to precipitation and other driving variables at different spatial and temporal scales, which complicates understanding of the relationships that govern ecosystem conditions. To better characterize the ecosystem response, we present a low-dimensional framework for simulating the influence of precipitation event timing and magnitude on grassland ecosystems, with particular focus on characterizing the temporal sensitivity of water and carbon fluxes to climate forcings and the feedback of water and carbon on soil moisture availability. Results show variation in daily through seasonal sensitivity of ecosystem water and carbon fluxes and identifies the way these sensitivities change at daily to annual timescales to shape long-term ecosystem states. This provides for a better understanding of the nonlinearities inherent to ecosystem interactions during the growing season and provides assessment of the extent that precipitation variance has on grassland functioning and heterogeneity. Copyright © 2011 John Wiley & Sons, Ltd.

The roles of shifting and filtering in generating community-level flowering phenology - Craine, J.M.; Wolkovich, E.M.; Towne, E.G. (Ecography, 2012)
Plant phenologies are key components of community assembly and ecosystem function, yet we know little about how phenological patterns differ among ecosystems. Community-level phenological patterns may be driven by the filtering of species into communities based on their phenology or by intraspecific responses to local conditions that shift when species flower. To understand the relative roles of filtering and shifting on community-level phenological patterns we compared patterns of first flowering dates (FFD) for herbaceous species at Konza Prairie, KS, USA with those from the colder Fargo, ND, USA area and from Chinnor, England, which has a less continental climate. Comparing patterns of FFD supports that Konza's flowering patterns are potentially influenced both by filtering species that flower early in the growing season and by phenological shifting. Konza species flowering dates were earlier in the spring and later in the fall compared to Fargo, but were not shifted compared to Chinnor, which had a unique suite of early-flowering species. In all, comparing flowering phenology among three sites reveals that intraspecific responses to climate can generate phenological shifts that compress or stretch community-level phenological patterns, while novel niches in phenological space can also alter community-level patterns. Community flowering patterns related to climate suggest that climatic warming has the potential to further distribute flowering of the Konza flora over a longer period, but also could further open it to introductions of non-native species that have evolved to flower early in the season.

Root characteristics of C-4 grasses limit reliance on deep soil water in tallgrass prairie - Jesse B. Nippert; Wieme, R.A.; Ocheltree, T.W.; Craine, J.M. (Plant and Soil, 2012)
Background C4 grass species in the mesic tallgrass prairie of central North America can exhibit both high root production and deep rooting in the soil profile (>2 m). Differences in root growth and the types of roots produced vary according to local environmental gradients and management practices. The production of deep roots in tallgrass prairie has been historically presumed as a mechanism for water uptake when surface soils are dry. Methods We examined changes in root biomass, total root length, root width, and theoretical hydraulic conductivity using roots collected from deep soil cores in upland and lowland topographic positions in grazed and ungrazed watersheds of the Konza Prairie Biological Station in north-eastern Kansas, USA. Results Root biomass, total root length, and theoretical hydraulic conductivity were highest in roots found in the top 20 cm of the soil profile, and then declined exponentially with increasing soil depth. Compared to grazed areas, ungrazed locations had more root biomass and total root length of roots in the most superficial soil layers. No differences in rooting profiles were present among topographic contrasts. Theoretical hydraulic conductivity of axial root xylem did not vary by topographic position or grazing contrasts, and declines in conductivity by depth were driven by changes in the number of vessels per stele, rather than changes in vessel size. Conclusions Irrespective of differences by grazing treatment or topographic position, significant reductions in root biomass, total root length, and theoretical hydraulic conductivity of grass roots at soil depths greater than 1 m suggest deep roots in this grassland have limited functional significance for water uptake.
Keywords: Andropogon gerardii; C4 grass; Mesic grassland; Root biomass; Theoretical hydraulic conductivity; Total root length

Seed source affects establishment and survival for three grassland species sown into reciprocal common gardens - Carter, D.L.; John M. Blair (Ecosphere, 2012)
The source of plant material can affect the successful establishment and subsequent survival of plant species in restoration. Sometimes a local advantage is assumed or advocated, but research to date is equivocal on the relative success of local versus non-local plant sources in restoration. Global change, which is altering environmental conditions broadly and within local sites, raises additional questions regarding whether local sources will consistently perform best in the future. We investigated the effects of seed source (local vs. non-local) on the performance of three grassland species across variable environments using reciprocal common gardens in three states (Nebraska, Kansas, and Oklahoma). In order to mimic the restoration of grassland vegetation from seed under realistic conditions where species interact with one-another during establishment, we focused on three species (Elymus canadensis, Oligoneuron rigidum, and Sorghastrum nutans) that were seeded together into communities with nine additional grassland species, simultaneously and identically manipulating source for all species. Both common garden site and seed source affected initial (first year) establishment in terms of density and survival, but responses differed among seed sources and were not consistent among species. No seed source, including local, had a consistent advantage. Effects of seed source on initial density, in addition to survival, suggest that experiments utilizing transplants might miss important effects of seed source on establishment and that the relative performance of different sources within a single site or that of any one species across sites cannot be easily generalized.

Sensitivity of mean annual primary production to precipitation - Hsu, J.S.; Powell, J.; P. Adler (Global Change Biology, 2012)
In many terrestrial ecosystems, variation in aboveground net primary production (ANPP) is positively correlated with variation in interannual precipitation. Global climate change will alter both the mean and the variance of annual precipitation, but the relative impact of these changes in precipitation on mean ANPP remains uncertain. At any given site, the slope of the precipitation-ANPP relationship determines the sensitivity of mean ANPP to changes in mean precipitation, whereas the curvature of the precipitation-ANPP relationship determines the sensitivity of ANPP to changes in precipitation variability. We used 58 existing long-term data sets to characterize precipitation-ANPP relationships in terrestrial ecosystems and to quantify the sensitivity of mean ANPP to the mean and variance of annual precipitation. We found that most study sites have a nonlinear, saturating relationship between precipitation and ANPP, but these nonlinearities were not strong. As a result of these weak nonlinearities, ANPP was nearly 40 times more sensitive to precipitation mean than variance. A 1% increase in mean precipitation caused a −0.2% to 1.8% change in mean ANPP, with a 0.64% increase on average. Sensitivities to precipitation mean peaked at sites with a mean annual precipitation near 500 mm. Changes in species composition and increased intra-annual precipitation variability could lead to larger ANPP responses to altered precipitation regimes than predicted by our analysis.

Septate endophyte colonization and host responses of grasses and forbs native to a tallgrass prairie - Mandyam, K.G.; Fox, C.; A. Jumpponen (Mycorrhiza, 2012)
Native tallgrass prairies support distinct dark septate endophyte (DSE) communities exemplified by Periconia macrospinosa and Microdochium sp. that were recently identified as common root symbionts in this system. Since these DSE fungi were repeatedly isolated from grasses and forbs, we aimed to test their abilities to colonize different hosts. One Microdochium and three Periconia strains were screened for colonization and growth responses using five native grasses and six forbs in an in vitro system. Previously published data for an additional grass (Andropogon gerardii) were included and reanalyzed. Presence of indicative inter- and intracellular structures (melanized hyphae, microsclerotia, and chlamydospores) demonstrated that all plant species were colonized by the DSE isolates albeit to varying degrees. Microscopic observations suggested that, compared to forbs, grasses were colonized to a greater degree in vitro. Host biomass responses varied among the host species. In broad comparisons, more grass species than forbs tended to respond positively to colonization, whereas more forb species tended to be non-responsive. Based on the suspected differences in the levels of colonization, we predicted that tallgrass prairie grasses would support greater DSE colonization than forbs in the field. A survey of field-collected roots from 15 native species supported this hypothesis. Our study supports the “broad host range” of DSE fungi, although the differences in the rates of colonization in the laboratory and in the field suggest a greater compatibility between grasses and DSE fungi. Furthermore, host responses to DSE range from mutualism to parasitism, suggesting a genotype-level interplay between the fungi and their hosts that determines the outcome of this symbiosis.
Keywords: Dark septate endophytes (DSE); Mutualism–parasitism continuum; Mycorrhizal dependency

Several grassland soil nematodes species are insensitive to RNA-mediated interference - Wheeler, D.; Darby, B.J.; Todd, T.C.; Herman, M.A. (Journal of Nematology, 2012)
Phenotypic analysis of defects caused by RNA mediated interference (RNAi) in Caenorhabditis elegans has proven to be a powerful tool for determining gene function. In this study we investigated the effectiveness of RNAi in four non-model grassland soil nematodes, Oscheius sp FVV-2., Rhabditis sp, Mesorhabditis sp., and Acrobeloides sp. In contrast to reference experiments performed using C. elegans and Caenorhabditis briggsae, feeding bacteria expressing dsRNA and injecting dsRNA into the gonad did not produce the expected RNAi knockdown phenotypes in any of the grassland nematodes. Quantitative reverse-transcribed PCR (qRT-PCR) assays did not detect a statistically significant reduction in the mRNA levels of endogenous genes targeted by RNAi in Oscheius sp., and Mesorhabditis sp. From these studies we conclude that due to low effectiveness and inconsistent reproducibility, RNAi knockdown phenotypes in non-Caenorhabditis nematodes should be interpreted cautiously.

Stability of tallgrass prairie during a 19-year increase in growing season precipitation - Scott. L. Collins; Koerner, S.E.; Plaut, J.A.; Okie, J.G.; Brese, D.; Calabrese, L.B.; Carvajal, A.; Evanse, R.J.; Nonaka, E. (Functional Ecology, 2012)

Surprises and insights from long-term aquatic datasets and experiments - W. K. Dodds; Robinson, C.T.; Gaiser, E.E.; Hansen, G.J.A.; Powell, H.; Smith, J.M.; Morse, N.B.; Johnson, S.L.; Gregory, S.V.; Bell, T.; Kratz, T.K.; W.H. McDowell (BioScience, 2012)
Long-term research on freshwater ecosystems provides insights that can be difficult to obtain from other approaches. Widespread monitoring of ecologically relevant water-quality parameters spanning decades can facilitate important tests of ecological principles. Unique long-term data sets and analytical tools are increasingly available, allowing for powerful and synthetic analyses across sites. Long-term measurements or experiments in aquatic systems can catch rare events, changes in highly variable systems, time-lagged responses, cumulative effects of stressors, and biotic responses that encompass multiple generations. Data are available from formal networks, local to international agencies, private organizations, various institutions, and paleontological and historic records; brief literature surveys suggest much existing data are not synthesized. Ecological sciences will benefit from careful maintenance and analyses of existing long-term programs, and subsequent insights can aid in the design of effective future long-term experimental and observational efforts. Long-term research on freshwaters is particularly important because of their value to humanity.
Keywords: data; freshwater; lakes; long term; streams

Temporal scales of tropospheric CO2, precipitation, and ecosystem responses in the central Great Plains - Cochran, F.V.; N. Brunsell (Remote Sensing of Environment, 2012)
Natural and anthropogenic sources of CO2 around the globe contribute to mid-tropospheric concentrations, yet it remains unknown how measurements of mid-tropospheric CO2 relate to regional ecosystem dynamics. NASA Atmospheric Infrared Sounder (AIRS) measurements of CO2 concentrations in the mid-troposphere from 2002 to 2010 were examined in relation to precipitation and vegetation phenology across the US Great Plains. Wavelet multi-resolution analysis and the information theory metric of relative entropy were applied to assess regional relationships between mid-tropospheric CO2, Normalized Difference Vegetation Index (NDVI), and precipitation (PPT). Results show that AIRS observations of mid-tropospheric CO2 exchange greater amounts of information with regional PPT and NDVI at seasonal, annual, and longer time scales compared to shorter time scales. PPT and NDVI contribute to mid-tropospheric CO2 at the 18-month time scale, while spatial patterns seen at this time scale for PPT and mid-tropospheric CO2 are reflective of the influence of PPT on NDVI at the annual scale. Identification of these dominant temporal scales may facilitate utilization of AIRS CO2 for monitoring regional source/sink dynamics related to climate and land-use/cover change.
Keywords: Atmospheric Infrared Sounder; Land–atmosphere interactions; relative entropy; wavelets

A test of two mechanisms proposed to optimize grassland aboveground primary productivity in response to grazing - Alan K. Knapp; D.L. Hoover; John M. Blair; Buis, G.; Burkepile, D.E.; Chamberlain, A.J.; Scott. L. Collins; Fynn, R.W.S.; Kirkman, K.P.; M.D. Smith; Blake, D.; Govender , N.; et al. (Journal of Plant Ecology, 2012)
Aims Mesic grasslands have a long evolutionary history of grazing by large herbivores and as a consequence, grassland species have numerous adaptations allowing them to respond favourably to grazing. Although empirical evidence has been equivocal, theory predicts that such adaptations combined with alterations in resources can lead to grazing-induced overcompensation in aboveground net primary production (ANPP; grazed ANPP > ungrazed ANPP) under certain conditions. We tested two specific predictions from theory. First, overcompensation is more likely to occur in annually burned grasslands because limiting nutrients that would be lost with frequent fires are recycled through grazers and stimulate ANPP. Second, overcompensation of biomass lost to grazers is more likely to occur in unburned sites where grazing has the greatest effect on increasing light availability through alterations in canopy structure. Methods We tested these nutrient versus light-based predictions in grazed grasslands that had been annually burned or protected from fire for >20 years. We assessed responses in ANPP to grazing by large ungulates using both permanent and moveable grazing exclosures (252 exclosures from which biomass was harvested from 3192 quadrats) in a 2-year study. Study sites were located at the Konza Prairie Biological Station (KPBS) in North America and at Kruger National Park (KNP) in South Africa. At KPBS, sites were grazed by North American bison whereas in KNP sites were grazed either by a diverse suite of herbivores (e.g. blue wildebeest, Burchell’s zebra, African buffalo) or by a single large ungulate (African buffalo). Important Findings We found no evidence for overcompensation in either burned or unburned sites, regardless of grazer type. Thus, there was no support for either mechanism leading to overcompensation. Instead, complete compensation of total biomass lost to grazers was the most common response characterizing grazing–ANPP relationships with, in some cases, undercompensation of grass ANPP being offset by increased ANPP of forbs likely due to competitive release. The capability of these very different grass-dominated systems to maintain ANPP while being grazed has important implications for energy flow, ecosystem function and the trophic dynamics of grasslands.
Keywords: aboveground net primary production; fire; forbs; herbivores; savanna

The timing of climate variability and grassland productivity - Craine, J.M.; Jesse B. Nippert; Elmore, A.J.; Skibbe, A.M.; Hutchinson, S.L.; N. Brunsell (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Changes in precipitation amount and variability have the potential to alter the structure and function of grasslands, but we know little about how changes in the timing of precipitation might affect grasslands. Here, we analyze long-term records from a tallgrass prairie to show that shifts in the timing of precipitation during the growing season have little effect on primary productivity or grass reproduction, but can greatly affect grazer performance. While greater late-season precipitation increases the weight gain of adult and young bison, greater mid-season precipitation decreases their weight gain. In addition, calving rates are lower after years with greater mid-season precipitation and higher after years with greater late-season precipitation. As well-timed drought can actually increase grazer weight gain and reproduction, it will be necessary to generate predictions of within-season distribution of precipitation to successfully forecast future grazer performance.

Tracking C and N flows through microbial biomass with increased soil moisture variability - Tiemann, L.K.; Billings, S.A. (Soil Biology & Biochemistry, 2012)
Changes in soil moisture with cycles of soil wetting and drying are associated with shifts in osmotic potentials that can induce physiological stress for microbial communities. These instances of soil moisture stress can be of sufficient magnitude to alter flows of C and N at an ecosystem scale. In this study we manipulated the duration and severity of soil moisture stress and disturbance in grassland soils from four sites along a precipitation gradient. After subjecting soils to a two-month long incubation under two different wetting-drying regimes, one of high and one of low stress and disturbance, we moistened soils with 13C- and 15N-labeled glycine solution to trace C and N though the soil and its microbial communities as they dried. Contrary to our predictions, we found evidence for preferential use of N-free osmolytes with increased soil moisture stress in soils from the mesic end of the precipitation gradient. Soils from the western, semi-arid end of the gradient were less sensitive to soil moisture stress and did not differ in N demand under high and low stress. Specific respiration rates were higher in all soils under greater soil moisture stress immediately after re-wetting, then returned to levels equal to or below rates in soils under low soil moisture stress regimes. Nitrification outpaced denitrification processes in soils under the highest levels of soil moisture stress. These results suggest increases in both soil CO2 release and N losses as stress induced by greater soil moisture variability increases in relatively mesic grassland systems, a predicted consequence of climate change in this region.
Keywords: Carbon use efficiency; Climate change; grassland; Precipitation regime; Soil carbon; Soil moisture variability; Soil nitrogen

Variable effects of dipteran parasitoids and management treatment on grasshopper fecundity in a tallgrass prairie - Laws, A.; Anthony Joern (Bulletin of Entomological Research, 2012)
Grasshoppers host a number of parasitoids, but little is known about their impact on grasshopper life history attributes or how those impacts may vary with land use. Here, we report on a three-year survey of nine grasshopper species in a tallgrass prairie managed with fire and bison grazing treatments. We measured parasitoid prevalence and the impact of parasitoid infection on grasshopper fecundity to determine if grasshopper-parasitoid interactions varied with management treatment. Adult female grasshoppers were collected every three weeks from eight watersheds managed with different prescribed burning and grazing treatments. Grasshopper fecundity with and without parasitoids was estimated through dissections of reproductive tracts. Dipteran parasitoids from two families (Nemestrinidae and Tachinidae) were observed infecting grasshoppers. We found significant effects of grazing treatment, but not burn interval, on grasshopper-parasitoid interactions. Parasitoids were three times more abundant in watersheds with bison grazing than in ungrazed watersheds, and the relative abundance of nemestrinid and tachinid flies varied with grazing treatment. Parasitoid prevalence varied among grasshopper species from <0.01% infected (Mermiria bivittata) to 17% infected (Hypochlora alba). Parasitoid infection reduced individual grasshopper fecundity, with stronger effects on current reproduction than on past reproduction. Furthermore, current fecundity in parasitized grasshoppers was lower in grazed watersheds compared to ungrazed watersheds. Nemestrinid parasitoids generally had stronger impacts on grasshopper fecundity than tachinid parasitoids, the effects of which were more variable.
Keywords: grassland; Grazing; host-parasitoid interactions; Konza Prairie Biological Station; Orthoptera; reproduction

Woody encroachment decreases diversity across North American grasslands and savannas - Z. Ratajczak; Jesse B. Nippert; Scott. L. Collins (Ecology, 2012)
Woody encroachment is a widespread and acute phenomenon affecting grasslands and savannas worldwide. We performed a meta-analysis of 29 studies from 13 different grassland/savanna communities in North America to determine the consequences of woody encroachment on plant species richness. In all 13 communities, species richness declined with woody plant encroachment (average decline = 45%). Species richness declined more in communities with higher precipitation (r2 = 0.81) and where encroachment was associated with a greater change in annual net primary productivity (ANPP; r2 = 0.69). Based on the strong positive correlation between precipitation and ANPP following encroachment (r2 = 0.87), we hypothesize that these relationships occur because water-limited woody plants experience a greater physiological and demographic release as precipitation increases. The observed relationship between species richness and ANPP provides support for the theoretical expectation that a trade-off occurs between richness and productivity in herbaceous communities. We conclude that woody plant encroachment leads to significant declines in species richness in North American grassland/savanna communities.

Zen of the Plains: discovering space, place, and self - Olstad, T.A. (Kansas State University, 2012)
With their windswept ridges and wind-rent skies, prairies and plains have often been denigrated as nothing but nothing—empty, meaningless, valueless space. Mountains and forests, oceans and deserts have been praised and protected while vast expanses of undulating grasslands have been plowed under, grazed over, used, abused, maligned. Once the largest ecosystem on the North American continent, wild prairies now persist mainly in overlooked or unwanted fragments. In part, it’s a matter of psychology; some people see plains as visually unpleasing (too big, too boring) or physically alienating (too dry, too exposed). It’s also part economics; prairies seem more productive, more valuable as anything but tangles of grass and sage. But at heart, it’s a matter of sociocultural and individual biases; people seeking bucolic or sublime landscapes find “empty,” treeless skyscapes flat and dull, forgettable. Scientific, social, and especially aesthetic appreciation for plains requires a different perspective—a pause in place—an exploration of the horizon as well as an examination of the minutiae, few people have strived to understand and appreciate undifferentiated, untrammeled space. This research seeks to change that by example, using conscientious, systematic reflection on first-hand experience to explore questions fundamental to phenomenology and geography—how do people experience the world? How do we shape places and how do places shape us?—in the context of plains landscapes. Written and illustrated from the perspective of a newcomer, a scholar, a National Park Service ranger, a walker, a watcher, a person wholly and unabashedly in love with wild places, the creative non-fiction narratives, photoessays, and hand-drawn maps address themes of landscape aesthetics, sense of place, and place-identity by tracing the natural, cultural, and managerial histories of and personal relationships with Arizona’s Petrified Forest National Park, South Dakota’s Badlands National Park, Kansas’s Konza Prairie Long-Term Ecological Research Station, and Wyoming’s Fossil Butte National Monument. Prosaic and photographic meditations on wildness and wilderness, travel and tourism, preservation and conservation, days and seasons, expectations and acceptance, even dreams and reality intertwine to evoke and illuminate the inspiring aesthetic of spacious places—Zen of the plains.
Keywords: Environmental history -- Great Plains; Landscape perception; National park service; Nature writing; prairie; Sense of place

Abundance and spatiotemporal distribution of the non-native house mouse in native tallgrass prairie - D.W. Kaufman; Kaufman, D.M.; Kaufman, G.A. (Transactions of the Kansas Academy of Science, 2011)
We have sampled small mammals on the Konza Prairie Biological Station, in eastern Kansas, from autumn 1981 through the present. One part of this effort has involved sampling rodents and shrews on 14 permanent traplines (20 stations, 15-m interstation intervals and 4 consecutive nights) situated in native tallgrass prairie during each of 29 autumns and 29 springs as well as 6 summers. In these permanent sites, house mice (Mus musculus) were extremely uncommon as illustrated by average abundances of 0.023 mice/100 trap nights (TN) in autumn, 0.022 mice/100 TN in summer and 0.000 mice/100 TN in spring. Precipitation in summer influenced autumn use of tallgrass prairie by house mice; captures only occurred in autumn when precipitation was ≥300 mm in the previous summer. House mice were slightly more likely (though not significantly) to be captured in lowland than upland or hill slope prairie. The distribution of occurrence was not influenced by fire (burned or unburned) or grazing history (grazed or ungrazed). Over our total trapping efforts on Konza Prairie (sampling on the permanent traplines plus other traplines and grids), we captured only 36 house mice or about 0.01 individual/100 TN. Overall, more males (64%) than females were captured; males, on average, were larger (14.0 g) than females (10.5 g) in body size; females typically were non-reproductive (only one of 13 was pregnant) and individuals typically were trapped only once. Captures were distributed broadly in both space and time and lacked predictability (i.e., exhibited an “anti-nested” distribution of captures). These and other patterns suggest that most house mice were transients in the tallgrass prairie. Distribution and abundance of house mice also imply that this introduced species is extremely uncommon and likely will never be invasive in native tallgrass prairie.
Keywords: abundance; anti-nested distribution; body size; introduced species; Konza Prairie; limestone outcrops; Mus musculus; planted brome fields; reproduction; woodland habitats

Abundance of introduced species at home predicts abundance away in herbaceous communities - Firn, J.; Joslin L. Moore; MacDougall, A.S.; E.T. Borer; Seabloom, E.W.; HilleRisLambers, J.; Harpole, W.S.; Cleland, E.E.; C.S. Brown; Knops, J.M.H.; Prober, S.M.; Pyke, D.A.; et al. (Ecology Letters, 2011)

Analysis of ribosomal RNA indicates seasonal fungal community dynamics in Andropogon gerardii roots - A. Jumpponen (Mycorrhiza, 2011)
Use of the reverse-transcribed small subunit of the ribosomal RNA (rRNA) was tested for exploring seasonal dynamics of fungal communities associated with the roots of the dominant tallgrass prairie grass, Andropogon gerardii. Ribosomal RNA was extracted, reverse-transcribed, and PCR-amplified in four sampling events in May, July, September, and November. Analyses of cloned PCR amplicons indicated that the A. gerardii rhizospheres host phylogenetically diverse fungal communities and that these communities are seasonally dynamic. Operational taxonomic units with Basic Local Alignment Search Tool affinities within the order Helotiales were dominant in the rhizosphere in May. These putative saprobes were largely replaced by arbuscular mycorrhizal fungi with likely affinities within Glomerales suggesting that the fungal communities are not only compositionally but also functionally dynamic. These data suggest replacement of functional guilds comprised of saprobic fungi by mutualistic fungi in the course of a growing season.
Keywords: Rhizosphere; Ribosomal RNA; Seasonal dynamics; tallgrass prairie

Assessing fine-scale genotypic structure of a dominant species in native grasslands - M.L. Avolio; Chang, C.C.; M.D. Smith (The American Midland Naturalist, 2011)
Genotypic diversity of dominant species has been shown to have important consequences for community and ecosystem processes at a fine spatial scale. We examined the fine-scale (i.e., plant neighborhood scale, <1 m2) genotypic structure of Andropogon gerardii, a dominant species in the tallgrass prairie, which is a productive and endangered grassland ecosystem, employing the commonly used amplified fragment length polymorphism (AFLP) technique. In this paper we used two methods to assess the fine-scale genetic spatial structure of a dominant perennial grass, (1) we determined how many tillers to sample in a 1 m2 area and (2) we developed AFLP markers that would differentiate between genotypes. By determining appropriate sampling and molecular techniques, our findings can be applied to questions addressing how genetic diversity of dominant species affect ecosystem processes in the tallgrass prairie.

Bud production and dynamics of flowering and vegetative tillers of the perennial grass Andropogon gerardii (Poaceae): the role of developmental constraints - Ott, J.P.; D.C. Hartnett (American Journal of Botany, 2011)
•Premise of the Study: Perennial grasses maintain aboveground tiller populations through vegetative reproduction via belowground buds and sexual reproduction via seed. The maintenance of a bud bank has important demographic consequences for perennial grasses. A tradeoff between these reproductive modes would be expected for a plant with limited resource availability. However, the ontogeny of the tiller could affect its ability to allocate between these two modes of reproduction. •Methods: Vegetative bud production and dynamics and tiller production were examined biweekly through an annual cycle on vegetative and flowering tillers of Andropogon gerardii. •Key Results: Andropogon gerardii maintains a large reserve of dormant buds. Although vegetative and flowering tillers had similar bud phenology, flowering tillers produced larger numbers of buds of larger size, and transitioned a larger proportion of their buds to tiller, than did vegetative tillers. Therefore, a negative consequence of sexual reproduction on vegetative reproduction was not evident at the tiller level. A size threshold for floral induction likely exists that results in flowering tillers having more buds per tiller than vegetative tillers. The increased bud outgrowth of flowering tillers could be a result of their larger bud size or weaker apical dominance as compared to vegetative tillers. •Conclusions: Plant development can place significant constraints on tradeoffs between the reproductive modes in perennial grasses and could affect their plasticity in plant reproductive allocation. Differences in developmental phenology and bud production between flowering and vegetative tillers may influence grass responses to environmental changes such as altered precipitation regimes or resource availability.
Keywords: allocation; axillary bud; Bud bank; Meristem; ontogeny; perennial grass; Tiller recruitment; tradeoff; Vegetative reproduction

Changes in variability of soil moisture alter microbial community C and N resource use - Tiemann, L.K.; Billings, S.A. (Soil Biology and Biochemistry, 2011)
Grassland ecosystems contain ~12% of global soil organic carbon (C) stocks and are located in regions where global climate change will likely alter the timing and size of precipitation events, increasing soil moisture variability. In response to increased soil moisture variability and other forms of stress, microorganisms can induce ecosystem-scale alterations in C and N cycling processes through alterations in their function. We explored the influence of physiological stress on microbial communities by manipulating moisture variability in soils from four grassland sites in the Great Plains, representing a precipitation gradient of 485-1003 mm y-1. Keeping water totals constant, we manipulated the frequency and size of water additions and dry down periods in these soils by applying water in two different, two-week long wetting-drying cycles in a 72-day laboratory incubation. To assess the effects of the treatments on microbial community function, we measured C mineralization, N dynamics, extracellular enzyme activities (EEA) and a proxy for substrate use efficiency. In soils from all four sites undergoing a long interval (LI) treatment for which added water was applied once at the beginning of each two-week cycle, 1.4-2.0 times more C was mineralized compared to soils undergoing a short interval (SI) treatment, for which four wetting events were evenly distributed over each two-week cycle. A proxy for carbon use efficiency (CUE) suggests declines in this parameter with the greater soil moisture stress imposed in LI soils from all four different native soil moisture regimes. A decline in CUE in LI soils may have been related to an increased effort by microbes to obtain N-rich organic substrates for use as protection against osmotic shock, consistent with EEA data. These results contrast with similar in situ studies of response to increased soil moisture variability and may indicate divergent autotrophic vs. heterotrophic responses to increased moisture variability. Increases in microbial N demand and decreases in microbial CUE with increased moisture variability observed in this study, regardless of the soils' site of origin, imply that these systems may experience enhanced heterotrophic CO2 release and declines in plant-available N with climate change. This has particularly important implications for C budgets in these grasslands when coupled with the declines in net primary productivity reported in other studies as a result of increases in precipitation variability across the region.

Complexity in climate change impacts: An analytical framework for effects mediated by plant disease - Garrett, K.A.; Forbes, G.A.; Savary, S.; Skelsey, P.; Sparks, A.H.; Valdivia, C.; van Bruggen, A.H.C.; Willocquet, L.; Djurle, A.; Duveiller, E.; Eckersten, H.; Pande, S.; et al. (Plant Pathology, 2011)
The impacts of climate change on ecosystem services are complex in the sense that effective prediction requires consideration of a wide range of factors. Useful analysis of climate-change impacts on crops and native plant systems will often require consideration of the wide array of other biota that interact with plants, including plant diseases, animal herbivores, and weeds. We present a framework for analysis of complexity in climate-change effects mediated by plant disease. This framework can support evaluation of the level of model complexity likely to be required for analysing climate-change impacts mediated by disease. Our analysis incorporates consideration of the following set of questions for a particular host, pathogen, host–pathogen combination, or geographic region. 1. Are multiple biological interactions important? 2. Are there environmental thresholds for population responses? 3. Are there indirect effects of global change factors on disease development? 4. Are spatial components of epidemic processes affected by climate? 5. Are there feedback loops for management? 6. Are networks for intervention technologies slower than epidemic networks? 7. Are there effects of plant disease on multiple ecosystem services? 8. Are there feedback loops from plant disease to climate change? Evaluation of these questions will help in gauging system complexity, as illustrated for fusarium head blight and potato late blight. In practice, it may be necessary to expand models to include more components, identify those components that are the most important, and synthesize such models to include the optimal level of complexity for planning and research prioritization.
Keywords: cereal head blight; disease risk; ecosystem services; fusarium graminearum; phytophthora infestans; potato late blight

Cross-stream comparison of substrate-specific denitrification potential - Findlay, S.E.G.; Mulholland, P.J.; Hamilton, S.; Tank, J.; Bernot, M.; Burgin, A.J.; Crenshaw, C.; W. K. Dodds; Grimm, N.; W.H. McDowell; Potter, J.; Sobota, D. (Biogeochemistry, 2011)
Headwater streams have a demonstrated ability to denitrify a portion of their nitrate (NO3 −) load but there has not been an extensive consideration of where in a stream this process is occurring and how various habitats contribute to total denitrification capability. As part of the Lotic Intersite Nitrogen Experiment II (LINX II) we measured denitrification potential in 65 streams spanning eight regions of the US and draining three land-use types. In each stream, potential denitrification rates were measured in common substrate types found across many streams as well as locations unique to particular streams. Overall, habitats from streams draining urban and agricultural land-uses showed higher potential rates of denitrification than reference streams draining native vegetation. This difference among streams was probably driven by higher ambient nitrate concentrations found in urban or agricultural streams. Within streams, sandy habitats and accumulations of fine benthic organic matter contributed more than half of the total denitrification capacity (mg N removed m−2 h−1). A particular rate of potential denitrification per unit area could be achieved either by high activity per unit organic matter or lower activities associated with larger standing stocks of organic matter. We found that both small patches with high rates (hot spots) or more widespread but less active areas (cool matrix) contributed significantly to whole stream denitrification capacity. Denitrification estimated from scaled-up denitrification enzyme assay (DEA) potentials were not always dramatically higher than in situ rates of denitrification measured as 15N gas generation following 24-h 15N–NO3 tracer additions. In general, headwater streams draining varying land-use types have significant potential to remove nitrate via denitrification and some appear to be functioning near their maximal capacity.
Keywords: Comparative; Comparison of potential with realized denitrification; DEA; denitrification; stream; Substrate-specific

Demography of female Greater Prairie-Chickens in unfragmented grasslands in Kansas - Augustine, J.K.; Sandercock, B.K. (Avian Conservation and Ecology-Ecologie et Conservation des Oiseaux, 2011)
Populations of Greater Prairie-Chickens (Tympanuchus cupido) have been declining because of loss and fragmentation of tallgrass prairie habitats, and management plans require contemporary demographic data. Our objectives were to determine whether maternal nutrition or predation were determinants of nesting success and female survival. We captured and radio-marked 43 females at four leks in natural, unfragmented prairie during a 4-year study. Reproductive potential was high because females laid large clutches (10.9 ± 0.3 eggs, n = 24), renested following clutch loss (22.2%, n = 27 females), and had high egg viability (88.6 ± 5.0% of eggs hatched; n = 7 nests), but reproductive traits were not correlated with female morphometrics (mass, or tarsus and keel lengths). Daily survival rate of nests was low (0.928, n = 34 nests) resulting in a predicted nest success rate of 7.4% for a 35-day exposure period. We used known fate models to estimate weekly survival from telemetry data for 40 females. Weekly survival was 0.970 and the extrapolated survival rate for the 6-month breeding season was 45.7%. Using time-since-marking Cormack-Jolly-Seber models for live encounter data to control for transience, annual apparent survival was 0.277 ± 0.081 SE for 55 marked females after initial capture, and 0.424 ± 0.139 during subsequent intervals. Survival of females was 1.6 to 2.0 times higher during the nonbreeding season than the breeding season, presumably because females are susceptible to predation during incubation and brood-rearing. Predation of nests and females may be the main demographic factors limiting population viability because predation, and not maternal nutrition, accounted for unexpectedly low nesting success and breeding season survival of Greater Prairie-Chickens in natural habitats. Future research should investigate rangeland practices that increase residual nesting cover or reduce predator impacts.

Design and effectiveness of a novel trap for capturing nesting songbirds - Sousa, B.F.; Stewart, S.L.M. (Journal of Field Ornithology, 2011)
Capturing songbirds at their nests can be challenging and time consuming. Although traps designed for capturing songbirds at their nests have been described in the literature, few are effective for capturing species with open-cup nests. We describe a cylindrical trap designed to capture songbirds at nests up to 2 m above ground in grasses, forbs, shrubs, and small saplings. The nest trap is constructed using a rigid hoop, two pieces of mist net, three stakes, and twist ties. We used this trap to capture female Dickcissels (Spiza americana) and female Indigo Buntings (Passerina cyanea) at their nests, with success rates of 85% (N= 196) and 60–73% (N= 16), respectively. Trapping success was comparable to that using other passerine nest trap designs. Nest abandonment after trapping attempts was rare and similar to that reported in previous studies. Our nest trap is lightweight, easy to make, versatile enough to use in a variety of grassland and shrub habitats, and easily carried and deployed in the field.

Differential responses to defoliation frequency in Little Bluestem (Schizachyrium scoparium) in tallgrass prairie: Implications for herbivory tolerance and avoidance - N’Guessan, M.; D.C. Hartnett (Plant Ecology, 2011)
Plant responses to herbivory are complex. In grasses, relative growth rate (RGR), seed, and vegetative reproduction, resource allocation, and architecture vary differentially and often nonlinearly with grazing intensity. High grazing tolerance may be achieved through compensatory photosynthesis and leaf growth, or through demographic mechanisms such as activation of a belowground dormant bud bank. This study assessed the relationship between grazing frequency and responses of Schizachyrium scoparium (little bluestem) in a tallgrass prairie, and examined the roles of tiller growth, reproduction, and bud (meristem) populations in its persistence under grazing. Genets were subjected to varying simulated grazing frequencies for a period of 2 years. Strong differential responses were observed among plant traits. RGR, biomass, and flowering showed strong nonlinear reductions in response to increasing clipping frequency, with no evidence of threshold effects. However, meristem density was unaffected, and plants maintained a large bud bank across all clipping treatments. Tiller natality decreased initially, but increased with >4 clippings, suggesting that declines in tiller RGR are partially offset by increasing tiller natality, and that variation in genet size is driven more by demography than by variation in individual tiller growth. Increased grazing frequency also resulted in differential activation of buds at different positions (emerging within vs. outside the subtending leaf sheath), explaining the shift to a more prostrate growth form observed in many caespitose grasses under persistent grazing. Thus, although this grass species lacks the capacity for compensatory foliage re-growth, the maintenance of a large dormant bud bank and the differential activation of buds in different positions contribute to its grazing tolerance and avoidance, respectively, and its long-term persistence in grazed grasslands.
Keywords: bud banks; Compensation; demography; Grasses; Grazing; Herbivory

Direct and indirect effects of central stoneroller (Campostoma anomalum) on mesocosm recovery following a flood: can macroconsumers affect denitrification? - Reisinger, A.J.; Presuma, D.L.; K. B. Gido; W. K. Dodds (Journal of the North American Benthological Society, 2011)
Anthropogenic N loadings and perturbations of macroconsumer communities impair ecological and economic services provided by streams. Organisms are adapted to natural disturbances, such as flooding and desiccation, but how anthropogenic and natural disturbances interact is poorly understood. We used large outdoor mesocosms to study the effect of Campostoma anomalum, a common prairie headwater-stream minnow, and NH4+ additions (to simulate fish excretion) on the recovery of ecosystem structure and function following a flood, highlighting the potential for Campostoma (and other macroconsumers) to affect denitrification. Campostoma and NH4+ treatments differentially affected particulate organic matter size and filamentous algal structure. Ecosystem structure responded differently to mesocosm treatment over time, a result suggesting that grazers or NH4+-N availability may be especially important during early recovery periods. The presence of Campostoma did not influence denitrification, but NH4+ additions altered the response of denitrifiers to nutrient and energy amendments, and denitrification rates decreased following the recovery of mesocosms. Temporal changes in denitrification probably were caused by increasing hyporheic dissolved O2 concentrations, which led to potentially fewer anoxic microsites for production of denitrification enzymes. Our study shows that grazers affect the recovery of ecosystem structure, but denitrification in the context of these prairie-stream mesocosms appears to be unaffected by Campostoma.
Keywords: Campostoma; denitrification; Ecosystem function; Flood; grazer; mesocosm; prairie streams; recovery

Dissolved inorganic carbon in soil and shallow groundwater, Konza Prairie LTER Site, NE Kansas, USA - Tsypin, Mikhail (University of Kansas, 2011)
Sources and seasonal trends of dissolved inorganic carbon (DIC) in a shallow limestone aquifer were studied for 1 year at the Konza Prairie LTER (Long-Term Ecological Research) Site in northeastern Kansas, from spring 2010 to spring 2011. Annual cycles of soil air CO2, groundwater DIC, and isotope characteristics showed a strong dependency on weather conditions and soil respiration. Soil air CO2 reached its annual maximum in the middle of the growing season, when moisture was not limiting to soil respiration. Following the maximum, the CO2 decreased because of moisture deficiency in the late summer and temperature decline in the fall and winter. The decrease began first in the shallowest part of the soil and last in the deepest part. Groundwater CO2 reached its annual maximum in October; this lag-time between the soil and groundwater CO2 maxima of 2-3 months may correspond to the travel time of soil-generated CO2 to the water table. The time-variable CO2 caused an annual carbonate-mineral saturation cycle, intensifying limestone dissolution, thus soil CO2 and carbonate minerals are the two main sources of DIC in soil and groundwater. The stable carbon isotope composition of soil air CO2 and DIC exhibited primarily C4 plant signature and were similar to that of soil organic matter, suggesting that both root and bacterial respiration are sources of CO2. DIC was enriched in 7-10 per mil PDB relative to the CO2 source due to isotope fractionation in a system open to soil CO2; the enrichment was smallest under highest pCO2. For this reason, d13CDIC was out of phase with DIC, the lightest in the late growing season. The carbon flux from the unsaturated zone to the unconfined aquifer during the year was variable depending on respiration and precipitation regimes, and had two main pathways. Transport of soil CO2 in the dissolved form with diffuse flow of recharge water was the most effective during the entire growing season. Downward movement of gaseous CO2 and equilibration with groundwater at the water table was possible in July to August. Storm rainfall events rapidly recharged the aquifer through preferential flow and stream-groundwater interaction. Rather than forcing soil gases downward because of water-saturated pores, the main effect of these events was dilution of groundwater. The calculated flux was about 0.3 M/m2/yr of C, which is less than 1% of the CO2 that is released by soil to the atmosphere via efflux. However, the climate prediction of increased respiration rates, temperature, and frequency of extreme rainfall events has the potential to cause higher carbon flux to the saturated zone, intensifying weathering and groundwater acidification.

Dynamic influences of nutrients and grazing fish on periphyton during recovery from flood - Murdock, J.N.; W. K. Dodds; K. B. Gido; M.R. Whiles (Journal of the North American Benthological Society, 2011)

The effect of environmental harshness on neurogenesis: a large-scale comparison - Chancellor, L.V.; Roth, T.C.; LaDage, L.D.; Pravosudov, V.V. (Developmental Neurobiology, 2011)
Harsh environmental conditions may produce strong selection pressure on traits, such as memory, that may enhance fitness. Enhanced memory may be crucial for survival in animals that use memory to find food and, thus, particularly important in environments where food sources may be unpredictable. For example, animals that cache and later retrieve their food may exhibit enhanced spatial memory in harsh environments compared with those in mild environments. One way that selection may enhance memory is via the hippocampus, a brain region involved in spatial memory. In a previous study, we established a positive relationship between environmental severity and hippocampal morphology in food-caching black-capped chickadees (Poecile atricapillus). Here, we expanded upon this previous work to investigate the relationship between environmental harshness and neurogenesis, a process that may support hippocampal cytoarchitecture. We report a significant and positive relationship between the degree of environmental harshness across several populations over a large geographic area and (1) the total number of immature hippocampal neurons, (2) the number of immature neurons relative to the hippocampal volume, and (3) the number of immature neurons relative to the total number of hippocampal neurons. Our results suggest that hippocampal neurogenesis may play an important role in environments where increased reliance on memory for cache recovery is critical. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 71: 246–252, 2011.
Keywords: black-capped chickadee; food hoarding; hippocampus; latitudinal gradient; neuron; spatial memory

Effects of riparian woody vegetation encroachment on prairie stream structure and function with emphasis on whole-stream metabolism - Riley, A.J. (Kansas State University, 2011)
Much of the North American tallgrass prairie ecosystem has been converted to cropland or urbanized. One threat to the remaining prairie ecosystems, and the streams within, is woody vegetation encroachment. Stream productivity, measured as metabolism, is a fundamental process comprised of gross primary production (GPP) and (CR) community respiration. Understanding GPP and CR is important because these processes are vital to ecosystem function and can be impacted by a change in canopy cover. First, I investigated improvements in existing methods for estimating whole-stream metabolism as estimated from diel patterns of oxygen (O2). I compared measured and modeled O2 and aeration (a physical parameter required for measurement of metabolism) rates to determine if direct measurement of aeration is necessary and the importance of temperature correction of metabolism. Modeling was moderately successful in determining aeration rates, and temperature correction of GPP and CR substantially improved model fits. Second, effects of woody vegetation encroachment on prairie stream function were investigated. Stream metabolism was measured for four years in duplicate reaches with varying canopy cover (closed canopy, naturally open canopy, and vegetation removal reaches). The removal reaches had closed canopy for the first two years and open canopy for the last two years. Canopy cover increased CR rates and had minimal effects on GPP. Third, the same experiment was used to determine the effects of woody vegetation encroachment on prairie stream ecosystem structure and food web interactions. Chlorophyll a and filamentous algal biomass were greater in naturally open and vegetation removal reaches, although the effects were stronger on filamentous algal biomass. As canopy cover decreased, the filamentous algal biomass to chlorophyll ratio increased, indicating a shift in algal community structure. Stable isotope analysis indicated some shift in pathways of nitrogen and carbon flux into the food web related to degree of canopy cover, but overlap in the signature of food sources made distinct food sources difficult to identify. The data indicate that riparian encroachment can influence ecosystem structure and function in prairie streams and restoration to remove woody riparian cover may restore some ecosystem features of naturally open canopy streams.
Keywords: canopy; metabolism; streams

Explaining temporal variation in above-ground productivity in a mesic grassland: the role of climate and flowering - Kimberly J. La Pierre; Yuan, S.H.; Chang, C.C.; M.L. Avolio; Hallett, L.M.; Schreck, T.; M.D. Smith (Journal of Ecology, 2011)
1. Annual above-ground net primary productivity (ANPP) in mesic grasslands is known to be highly temporally variable. While yearly precipitation or average yearly temperature can explain some of this temporal variability, much of the variation in ANPP remains unexplained. 2. Here we address the heretofore unexplained variation in 25 years of productivity data from a mesic grassland at Konza Prairie (north-eastern Kansas) by examining the effects of precipitation and temperature during periods relevant to the phenology and growth cycle of the dominant C4 grasses and the flowering stalk production of these species. We assessed both the direct effects and indirect effects via flowering of phenologically relevant climate periods on ANPP using structural equation modelling (SEM). 3. We found ANPP to be strongly positively influenced by flowering stalk production of the dominant C4 grasses, precipitation during periods relevant to vegetative growth (15 April–14 July) and flowering stalk elongation (15 July–14 August) of the dominant grasses, and fire. In addition, flowering stalk production was negatively influenced by high temperatures during the flowering stalk elongation period, which therefore resulted in a negative indirect effect on ANPP. We found little evidence for the effects of the previous year’s total annual precipitation or mean annual temperature on ANPP. 4. By including flowering stalk production and separating climate variables into phenologically relevant periods we were able to increase the percentage of observed variance in ANPP explained by six models, relating to different topographic positions and burn regimes, from an average of 22% to 48%, with the best model explaining 61% of variation in ANPP. 5.Synthesis. The link between climatic periods relevant to the phenology and growth of dominant C4 grasses, flowering stalk production of these grasses and ANPP shown here improves our ability to predict productivity in mesic grasslands, an ecologically and economically important ecosystem.

Fire resistance of tree species explains gallery forest community composition - Vanderweide, B.; D.C. Hartnett (Forest Ecology and Management, 2011)
Fire, climatic variability, and grazing by large herbivores have historically limited woody vegetation in the tallgrass prairie region of North America to gallery forests in protected areas along rivers and streams. Fire, in particular, has been a strong selective pressure against woody vegetation. Consequently, we expect that dominant tree species in these forests have developed mechanisms for tolerating periodic surface fires. Susceptibility of trees to fire damage depends in part on key properties of bark which influence heat transfer to the vascular cambium, including thickness, density, and moisture content. An historical (1983) survey of Konza Prairie Biological Station in northeast Kansas, USA indicated that gallery forests were co-dominated by Quercus macrocarpa and Quercus muehlenbergii, while Celtis occidentalis occurred as an important sub-dominant species. Populus deltoides, Gleditsia triacanthos, and Juniperus virginiana were relatively uncommon. To test the hypothesis that historically dominant gallery forest tree species are more resistant to fire damage than uncommon species, fire was applied to the bark of 10 individuals of each of these six species under conditions mimicking surface fires (400 °C for 120 s). Maximum temperature at the vascular cambium, bark thickness, bark moisture content, and bark density were measured. Trees were considered fire-resistant if the vascular cambium temperature remained below the thermal cell death threshold, 60 °C, throughout the treatment. Using logistic regression, bark thickness was found to be a significant predictor of lethal cambium temperatures (P = 0.002), while neither bark density nor moisture content were significantly related to lethal cambium temperature (P = 0.279 and P = 0.131, respectively). Across species, a minimum bark thickness of approximately 8.6 mm was necessary to maintain the vascular cambium temperature below 60 °C. Trees that produce thick bark quickly in juvenile size classes (P. deltoides, Q. macrocarpa, and Q. muehlenbergii) experienced lower temperatures at the vascular cambium than those which do not develop thick bark with increasing diameter (C. occidentalis, G. triacanthos, and J. virginiana). Ranking these tree species by either the DBH or age needed to develop the minimum protective bark thickness largely agreed with ranking based on historical relative importance. As fire frequency and intensity decrease in remnant tallgrass prairie of North America as a result of habitat fragmentation, fire suppression, and changing land management, fire-sensitive species may increase in relative importance in gallery forests because of increased juvenile survival.
Keywords: Bark; Fire resistance; Forest composition; gallery forest; Konza Prairie

From precipitation to groundwater baseflow in a native prairie ecosystem: a regional study of the Konza LTER in the Flint Hills of Kansas, USA - Steward, D.R.; Yang, X.; Lauwo, S.Y.; Staggenborg, S.A.; G. L. Macpherson; Welch, S.M. (Hydrology and Earth System Sciences, 2011)
Methods are developed to study hydrologic interactions across the surficial/groundwater interface in a native prairie ecosystem. Surficial ecohydrologic processes are simulated with the USDA's EPIC model using daily climate data from the Kansas Weather Data Library, vegetation and soil data from the USDA, and current land-use management practices. Results show that mean annual precipitation (from 1985–2005) is partitioned into 13% runoff regionally and 14% locally over the Konza LTER, lateral flow through soil is 1% regionally and 2% locally, groundwater recharge is 11% regionally and 9% locally, and evapotranspiration accounts for the remaining 75%. The spatial distribution of recharge was used in a regional Modflow groundwater model that was calibrated to existing groundwater observations and field measurements gathered for this study, giving a hydraulic conductivity in the Flint Hills region of 1–2 m day−1 with a local zone (identified here) of 0.05–0.1 m day−1. The resistance was set to fixed representative values during model calibration of hydraulic conductivity, and simple log-log relations correlate the enhanced recharge beneath ephemeral upland streams and baseflow in perennial lowland streams to the unknown resistance of the streambeds. Enhanced recharge due to stream transmission loss (the difference between terrestrial runoff and streamflow) represents a small fraction of streamflow in the ephemeral upland and the resistance of this streambed is 100 000 day. Long-term baseflow in the local Kings Creek watershed (2% of the groundwater recharge over the watershed) is met when the resistance of the lowland streambed is 1000 day. The coupled framework developed here to study surficial ecohydrological processes using EPIC and groundwater hydrogeological processes using Modflow provides a baseline hydrologic assessment and a computational platform for future investigations to examine the impacts of climate change, vegetative cover, soils, and management practices on hydrologic forcings.

Functional consequences of climate-change induced plant species loss in a tallgrass prairie - Craine, J.M.; Jesse B. Nippert; Towne, E.G.; Tucker, S.; Kembel, S.W.; Skibbe, A.M.; McLauchlan, K.K. (Oecologia, 2011)
Future climate change is likely to reduce the floristic diversity of grasslands. Yet the potential consequences of climate-induced plant species losses for the functioning of these ecosystems are poorly understood. We investigated how climate change might alter the functional composition of grasslands for Konza Prairie, a diverse tallgrass prairie in central North America. With species-specific climate envelopes, we show that a reduction in mean annual precipitation would preferentially remove species that are more abundant in the more productive lowland positions at Konza. As such, decreases in precipitation could reduce productivity not only by reducing water availability but by also removing species that inhabit the most productive areas and respond the most to climate variability. In support of this prediction, data on species abundance at Konza over 16 years show that species that are more abundant in lowlands than uplands are preferentially reduced in years with low precipitation. Climate change is likely to also preferentially remove species from particular functional groups and clades. For example, warming is forecast to preferentially remove perennials over annuals as well as Cyperaceae species. Despite these predictions, climate change is unlikely to unilaterally alter the functional composition of the tallgrass prairie flora, as many functional traits such as physiological drought tolerance and maximum photosynthetic rates showed little relationship with climate envelope parameters. In all, although climatic drying would indirectly alter grassland productivity through species loss patterns, the insurance afforded by biodiversity to ecosystem function is likely to be sustained in the face of climate change.
Keywords: biogeography; Climate change; Functional traits; Grasslands; Konza Prairie

A generalist grasshopper species (Melanoplus femurrubrum) is adapted to variable environments along a latitudinal gradient - Parsons, S. (Kansas State University, 2011)
Temperature and food quality vary across broad latitudinal gradients, greatly affecting performance by insect herbivores. The contribution of each varies latitudinally so that geographically distinct populations are challenged by differences in nutritional needs and energetic demands. While there has been extensive work studying diet selectivity and nutritional ecology of insect herbivores, few studies have focused on how insect herbivores adapt across such vast environmental gradients. The generalist-feeding grasshopper, Melanoplus femurrubrum (DeGreer), has a broad geographic range that extends across much of North America, making this species ideal for comparative investigations of intrinsic performance responses to extensive but predictable patterns of environmental variation. I compared responses by six populations collected from populations located from Texas to North Dakota (USA) using a common garden experimental design to investigate clinal responses in grasshopper performance. I examined responses in: (1) body size, (2) thermoregulation and adaptive coloration, (3) developmental and growth rates, (4) metabolic rates, (5) total consumption and rates, (6) diet ratio selection, and (7) digestive processing efficiencies across the latitudinal gradient. Grasshopper body size followed the Converse Bergmann’s Rule with decreasing body size as latitude increased. Temperature influenced all other responses, but responses to diet were not always significant or directional. Latitudinal trends for development and growth rates were observed but mass-specific metabolic rates were similar for all populations. Total consumption was body size dependent but independent of diet type. Mass-specific consumption varied but no single directional trend was detected. There was a shift in carbohydrate-biased diet preference at low latitude toward protein-biased diet ratios at higher latitudes, suggesting adaptations to different energetic demands by these populations. However, post-ingestive (digestive) efficiencies demonstrated variable responses with northern populations observing highest efficiencies for some indices but not all. Overall, this research documents phenotypic plasticity to environmental variability to some degree for digestive efficiencies, but ecotypic responses in body size and diet preference among M. femurrubrum populations were observed.
Keywords: body size; latitudinal gradient; Melanoplus femurrubrum; nutritional ecology; Performance; Temperature

Genetic parentage and local population structure in the socially monogamous Upland Sandpiper - Casey, A.E.; Sandercock, B.K.; Wisely, S.M. (Condor, 2011)
For a single lineage of birds, the diversity of mating systems and parental care among shorebirds (Charadrii) is high, which has made them an important group for investigations of the evolution of social mating systems. From 2003 to 2007, we studied a population of the Upland Sandpiper (Bartramia longicauda) at Konza Prairie Biological Station in northeastern Kansas. Our objectives were to determine the genetic mating system of this socially monogamous shorebird and to determine whether spatial patterns of philopatry and nest placement might affect opportunities for extra-pair mating. We used six microsatellite markers to estimate rates of extra-pair paternity in 58 family groups (107 parents, 184 offspring). We found that 30% of broods contained extra-pair offspring, representing 15% of chicks, the highest rate of extra-pair paternity ever reported in a socially monogamous shorebird. High rates of extra-pair paternity were not due to the degree of relatedness between partners in mated pairs, and they did not result in greater diversity among broods with extra-pair young. We used a spatial genetic-autocorrelation analysis and found evidence for relatedness among females nesting <1 km apart. The Upland Sandpiper might have a high rate of extra-pair paternity because related females nest synchronously and in close proximity, but the probability of extra-pair young was not related to nest density or distance to nearest nest. Female-biased natal philopatry is unusual among birds but is consistent with the mate-defense mating system of the Upland Sandpiper.
Keywords: Bartramia longicauda; dispersal; Extra-pair paternity; genetic structure; mating systems; natal philopatry; shorebirds; Upland Sandpiper

Genomic and resistance gene homolog diversity of the dominant tallgrass prairie species across the U.S. Great Plains precipitation gradient - Rouse, M.N.; Saleh, A.A.; Seck, A.; Keeler, K.H.; Travers, S.E.; Hulbert, S.H.; Garrett, K.A. (PLoS ONE, 2011)
Background Environmental variables such as moisture availability are often important in determining species prevalence and intraspecific diversity. The population genetic structure of dominant plant species in response to a cline of these variables has rarely been addressed. We evaluated the spatial genetic structure and diversity of Andropogon gerardii populations across the U.S. Great Plains precipitation gradient, ranging from approximately 48 cm/year to 105 cm/year. Methodology/Principal Findings Genomic diversity was evaluated with AFLP markers and diversity of a disease resistance gene homolog was evaluated by PCR-amplification and digestion with restriction enzymes. We determined the degree of spatial genetic structure using Mantel tests. Genomic and resistance gene homolog diversity were evaluated across prairies using Shannon's index and by averaging haplotype dissimilarity. Trends in diversity across prairies were determined using linear regression of diversity on average precipitation for each prairie. We identified significant spatial genetic structure, with genomic similarity decreasing as a function of distance between samples. However, our data indicated that genome-wide diversity did not vary consistently across the precipitation gradient. In contrast, we found that disease resistance gene homolog diversity was positively correlated with precipitation. Significance Prairie remnants differ in the genetic resources they maintain. Selection and evolution in this disease resistance homolog is environmentally dependent. Overall, we found that, though this environmental gradient may not predict genomic diversity, individual traits such as disease resistance genes may vary significantly.
Keywords: Amplified fragment length polymorphism; Cloning; Hexaploidy; Maize; Plant genomics; Plant pathology; Ploidy; Population genetics

Grasshopper fecundity responses to grazing and fire in a tallgrass prairie - Laws, A.; Anthony Joern (Environmental Entomology, 2011)
Grasshopper abundance and diversity vary with management practices such as fire and grazing. Understanding how grasshopper life history traits such as fecundity respond to management practices is key to predicting grasshopper population dynamics in heterogeneous environments. Landscape-level experimental fire and bison grazing treatments at the Konza Prairie Biological Station (Manhattan, KS) provide an opportunity to examine how management affects grasshopper fecundity. Here we report on grasshopper fecundity for nine common species at Konza Prairie. From 2007 to 2009, adult female grasshoppers were collected every 3 wk from eight watersheds that varied in fire and grazing treatments. Fecundity was measured by examining female reproductive tracts, which contain a record of past and current reproductive activity. Body size was a poor predictor of fecundity for all species. Despite large differences in vegetation structure and composition with management regime (grazing and fire interval), we observed little effect of management on grasshopper fecundity. Habitat characteristics (grasshopper density, vegetation biomass, and vegetation quality; measured in 2008 and 2009) were better predictors of past fecundity than current fecundity, with species-specific responses. Fecundity increased throughout the summer, indicating that grasshoppers were able to acquire sufficient nutritional resources for egg production in the early fall when vegetation quality is generally low. Because fecundity did not vary across management treatments, population stage structure may be more important for determining population level reproduction than management regime at Konza Prairie.
Keywords: Konza Prairie Biological Station; life-history; management; Orthoptera; reproduction

Hierarchical modeling of lek habitats of Greater Prairie-Chickens - Gregory, A.J.; McNew, L.B.; Prebyl, T.J.; Sandercock, B.K.; Wisely, S.M. (Studies in Avian Biology, 2011)

Historical processes and landscape context influence genetic structure in peripheral populations of the collared lizard (Crotaphytus collaris) - Blevins, E.; Wisely, S.M.; With, K.A. (Landscape Ecology, 2011)
Populations at the periphery of a species’ range often show reduced genetic variability within populations and increased genetic divergence among populations compared to those at the core, but the mechanisms that give rise to this core-periphery pattern in genetic structure can be multifaceted. Peripheral population characteristics may be a product of historical processes, such as founder effects or population expansion, or due to the contemporary influence of landscape context on gene flow. We sampled collared lizards (Crotaphytus collaris) at four locations within the northern Flint Hills of Kansas, which is at the northern periphery of their range, to determine the genetic variability and extent of genetic divergence among populations for ten microsatellite loci (n = 229). We found low genetic variability (average allelic richness = 3.37 ± 0.23 SE; average heterozygosity = 0.54 ± 0.05 SE) and moderate population divergence (average FST = 0.08 ± 0.01 SE) among our sample sites relative to estimates reported in the literature at the core of the species’ range in Texas. We also identified differences in dispersal rates among sampling locations. Gene flow within the Flint Hills was thus greater than for other peripheral populations of collared lizards, such as the Missouri glade system where most of the mesic grasslands have been converted to forest since the last glacial retreat, which appears to have greatly impeded gene flow among populations. Our findings signify the importance of considering landscape context when evaluating core-peripheral trends in genetic diversity and population structure.
Keywords: Collared lizard; Flint Hills; Microsatellites; tallgrass prairie

Human-mediated selection on life-history traits of Greater Prairie-Chickens - McNew, L.B.; Gregory, A.J.; Wisely, S.M.; Sandercock, B.K. (Studies in Avian Biology, 2011)

Infiltration controls in a tallgrass prairie at a hillslope scale - Auvenshine, S.D. (Kansas State University, 2011)
Infiltration capacity influences the ability of a soil to absorb and transmit water through macropores and micropores of the soil structure. Infiltration is primarily influenced by the soil type, which is dependent on a number of factors including parent material, climate, biological activity, and topography. Spatial controls of land use, land cover, soil texture, slope position, slope gradient and slope aspect are a few of the variables influencing infiltration capacity within a uniform soil type. The goals of the thesis are to (1) quantify the spatial distribution of soil hydraulic properties at the surface of a hillslope using one measurement method - the automated mini-disk tension infiltrometer - and several analysis methods, (2) determine the dependence of depth on soil hydraulic properties using two measurement methods, and (3) compare the results of the investigation with information from the soil survey and soil investigations. First, automated mini-disk infiltrometers were used to determine soil hydraulic properties at ten sites along a hillslope in Konza Prairie Natural Research Area. Several analysis methods were used to extract hydraulic conductivity and sorptivity values from the infiltration data. Next, large intact soil cores were extracted from three selected sites at the same hillslope and analyzed at six depths using a large disk infiltrometer. Finally, the six segments of the large soil cores were analyzed using the same methods as the field measurements with the mini-disk infiltrometers. The results of the field investigation at the ten sites show a variability of soil hydraulic properties over an assumed homogeneous landscape. The values of hydraulic conductivity and sorptivity are dependent on the method of analysis. An empirically based approach produced more realistic values than a physically based approach. The results of the laboratory investigation of the three extracted soil cores also show a dependence of method of analysis and measurement. In addition, the results show a complex relationship among landscape position, depth, and soil structure. Finally, while soil surveys and soil descriptions can provide detailed information on soil properties, an infiltration investigation at a detailed spatial scale provides quantitative values for soil hydraulic properties.
Keywords: Hydraulic conductivity; Hydrology; Infiltration; Konza Prairie

The influence of behavioral and landscape ecology on Greater Prairie-Chicken (Tympanuchus cupido) genetic structure and evolution - Gregory, A.J. (Kansas State University, 2011)

An integrated conceptual framework for long-term social-ecological research - Scott. L. Collins; Carpenter, S.R.; Swinton, S.M.; Orenstein, D.E.; Childers, D.L.; Gragson, T.L.; Grimm, N.B.; Grove, J.M.; Harlan, S.L.; Kaye, J.P.; Alan K. Knapp; Kofinas, G.P.; et al. (Frontiers in Ecology and the Environment, 2011)
The global reach of human activities affects all natural ecosystems, so that the environment is best viewed as a social–ecological system. Consequently, a more integrative approach to environmental science, one that bridges the biophysical and social domains, is sorely needed. Although models and frameworks for social–ecological systems exist, few are explicitly designed to guide a long-term interdisciplinary research program. Here, we present an iterative framework, “Press–Pulse Dynamics” (PPD), that integrates the biophysical and social sciences through an understanding of how human behaviors affect “press” and “pulse” dynamics and ecosystem processes. Such dynamics and processes, in turn, influence ecosystem services –thereby altering human behaviors and initiating feedbacks that impact the original dynamics and processes. We believe that research guided by the PPD framework will lead to a more thorough understanding of social–ecological systems and generate the knowledge needed to address pervasive environmental problems.

Interannual variability of pollen productivity and transport in mid-North America from 1997 to 2009 - McLauchlan, K.K.; Barnes, C.S.; Craine, J.M. (Aerobiologia, 2011)
Understanding the causes of interannual variability in atmospheric pollen concentration is an important but elusive goal for public health and environmental change. We analyzed long-term daily records of pollen counts from urban Kansas City, Missouri, USA collected from 1997 to 2009 for three pollen groups: Ambrosia, Poaceae, and a third group which is mostly composed of arboreal pollen types. The annual pollen index varied from 8,368 to 80,822 over the thirteen-year period. Although Ambrosia pollen is often thought to be associated with droughts and disturbance, years with high Ambrosia pollen were associated with high summer precipitation to the south of Kansas City. Years with high Poaceae pollen were associated with high spring precipitation to the south of the city. In support of the southern influence to Kansas City pollen, Ambrosia and Poaceae pollen mostly arrived on southern winds. In contrast to the other two pollen groups, the arboreal pollen was most associated with growing season precipitation to the east of Kansas City, although it was still highest on days with southern winds. Based on the correlations with climate, the severity of an upcoming allergy season may be predicted with early-season precipitation data, while short-term severity can be forecast from local weather patterns.
Keywords: climate; grass; Great Plains; Pollen; Ragweed

Intraspecific Variation in Ecophysiology of Three Dominant Prairie Grasses Used in Restoration: Cultivar Versus Non‐Cultivar Population Sources - Lambert, A.M.; S.G. Baer; D.J. Gibson (Restoration Ecology, 2011)
Dominant species play crucial roles in determining plant community structure and ecosystem function. Cultivars of the dominant prairie grasses are widely used in prairie restoration and are selected for characters such as high biomass production, increased reproductive output, and stress tolerance. Genetic differences exist between cultivar and non-cultivar population sources of dominant tallgrass prairie species, which may have implications for plant performance in prairie restoration. We measured net photosynthesis (Anet), stomatal conductance (gs), and water use efficiency (WUE) in cultivar and non-cultivar dominant tallgrass prairie species Andropogon gerardii Vitman, Sorghastrum nutans (L.) Nash, and Schizachyrium scoparium (Michx.) Nash in both a greenhouse experiment and an experimental tallgrass prairie restoration. We found indicators of enhanced physiological performance (higher Anet, gs, and/or WUE) in cultivar population sources of all three dominant grass species relative to non-cultivars. For A. gerardii, cultivars exhibited higher Anet and WUE than non-cultivars. For S. nutans, cultivars exhibited higher gs, whereas non-cultivars showed higher WUE. Lastly, cultivars of S. scoparium showed higher WUE than non-cultivar population sources. Our results show that population selection of dominant species in restoration can have consequences for plant performance, which may have implications for competitive interactions that affect community structure (i.e. diversity) and ecosystem function (i.e. aboveground net primary production) during the reassembly of prairie systems.
Keywords: Andropogon gerardii; Ecophysiology; photosynthesis; restoration; Schizachyrium scoparium; Sorghastrum nutans; tallgrass prairie

Land fragmentation under rapid urbanization: A cross-site analysis of Southwestern cities - York, A.M.; Shrestha, M.; Boone, C.G.; Zhang, S.; J. A. Harrington; Prebyl, T.J.; Swann, A.; Agar, M.; Antolin, M.F.; Nolen, B.; Wright, J.B.; Skaggs, R. (Urban Ecosystems, 2011)
Explosive population growth and increasing demand for rural homes and lifestyles fueled exurbanization and urbanization in the western USA over the past decades. Using National Land Cover Data we analyzed land fragmentation trends from 1992 to 2001 in five southwestern cities associated with Long Term Ecological Research (LTER) sites. We observed two general fragmentation trends: expansion of the urbanized area leading to fragmentation in the exurban and peri-urban regions and decreased fragmentation associated with infill in the previously developed urban areas. We identified three fragmentation patterns, riparian, polycentric, and monocentric, that reflect the recent western experience with growth and urbanization. From the literature and local expert opinion, we identified five relevant drivers – water provisioning, population dynamics, transportation, topography, and institutions – that shape land use decision-making and fragmentation in the southwest. In order to assess the relative importance of each driver on urbanization, we linked historical site-specific driver information obtained through literature reviews and archival analyses to the observed fragmentation patterns. Our work highlights the importance of understanding land use decision-making drivers in concert and throughout time, as historic decisions leave legacies on landscapes that continue to affect land form and function, a process often forgotten in a region and era of blinding change.
Keywords: Exurbanization; Land fragmentation; The US Southwest; Urban ecology

Landscape context matters: local habitat and landscape effects on the abundance and patch occupancy of collared lizards in managed grasslands - Blevins, E.; With, K.A. (Landscape Ecology, 2011)
The distribution and abundance of a species may be simultaneously influenced by both local-scale habitat features and the broader patch and landscape contexts in which these populations occur. Different factors may influence patch occupancy (presence–absence) versus local abundance (number of individuals within patches), and at different scales, and thus ideally both occupancy and abundance should be investigated, especially in studies that seek to understand the consequences of land management on species persistence. Our study evaluated the relative influences of variables associated with the local habitat patch, hillside (patch context), and landscape context on patch occupancy and abundance of the collared lizard (Crotaphytus collaris) within tallgrass prairie managed under different fire and grazing regimes in the northern Flint Hills of Kansas, USA. Using a multi-model information-theoretic approach that accounted for detection bias, we found that collared lizard abundance and occupancy was influenced by factors measured at both the local habitat and landscape scales. At a local scale, collared lizard abundance was greatest on large rock ledges that had lots of crevices, high vegetation complexity, and were located higher up on the hillslope. At the landscape scale, collared lizard abundance and occupancy were both higher in watersheds that were burned frequently (1–2 year intervals). Interestingly, grazing only had a significant effect on occupancy and abundance within less frequently burned (4-year burn interval) watersheds. Our results suggest that, in addition to the obvious habitat needs of this species (availability of suitable rock habitat), land-management practices have the potential to influence collared lizard presence and abundance in the grasslands of the Flint Hills. Thus, mapping the availability of suitable habitat is unlikely to be sufficient for evaluating species distributions and persistence in such cases without consideration of landscape management and disturbance history.
Keywords: Crotaphytus collaris; fire; Flint Hills; Grazing; Habitat suitability; Land management; tallgrass prairie

Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: case studies from the central and southern Great Plains - Cordova, C.E.; Johnson, W.C.; Mandel, R.D.; Palmer, M.W. (Catena, 2011)
This study investigates stable carbon isotopes (δ13C), opal phytolith assemblages, burnt phytoliths, microscopic charcoal and Sporormiella spores from modern soils and paleosols in Kansas and Oklahoma. Grass and dicot phytoliths in combination with δ13C are used as proxies for reconstructing the structure of grasslands and woodlands. Burnt grass phytoliths and microscopic charcoal are evaluated as proxies for reconstructing paleofire incidence. Concentrations of the fungal spore Sporormiella are used as a proxy for assessing large herbivore activity. These proxies were tested on various modern grassland communities of the central and southern Great Plains, including areas with bison, cattle, and small herbivores, and areas under different fire frequencies. Opal phytolith assemblages and δ13C values show that before cal 11 ka, C3 grasses and woody plants predominated in areas that today are dominated by C4 grasses. The origin of the shortgrass prairie dates back to about cal 10 ka. The origin of the tallgrass prairie, however, is not clear as phytolith data show variable assemblages throughout the Holocene (mixed-grass, tallgrass, and tallgrass–woodland mosaic). Different proxies (burnt phytoliths vs. charcoal) reveal different fire frequencies, but it is apparent that microfossil evidence for fire incidence is closely related to the abundance of woody plants in the landscape. Before cal 12 ka, soils show somewhat elevated concentration of Sporormiella, but lower concentrations than the modern high-density bison and cattle grazing areas. Throughout the Holocene, Sporormiella frequencies are low, which suggests lower large ungulate densities and perhaps high mobility.
Keywords: Charcoal; Great Plains; Opal phytoliths; Paleosols; Sporormiella; Stable carbon isotopes

The least shrew on Konza Prairie Biological Station, Kansas - Kaufman, G.A.; D.W. Kaufman (Transactions of the Kansas Academy of Science, 2011)
We report specific locations and attributes of least shrews (Cryptotis parva) captured over a 29-year period on the Konza Prairie Biological Station, Kansas. We used large, nonfolding Sherman live traps to survey small mammals in native tallgrass prairie habitats (by traplines and grids), woodland habitats (by traplines and grids) and planted brome fields (traplines only). Eighty-seven least shrews were captured over the 29 years of surveys (ca. 350,000 trap nights). Almost all captures (98%) occurred in prairie habitat; 80% of all captures occurred on a prairie grid during a 5-year period. Least shrews on prairie traplines were captured in a variety of topographic positions (upland, hillside slope and lowland) and in burned and unburned prairie, but not in prairie grazed by bison. We captured individuals that ranged in body size from 2.5–8.0 g. The mean body mass of all captured least shrews was 4.7 g (excluding pregnant females) and, when only adults were included (excluding pregnant females), it was 5.1g. We noted 13 pregnancies among 12 females; the earliest pregnancy was recorded in mid-April and latest in mid-October. Most pregnancies (ca. 70%) were recorded in two months, July and September. Lactating females that were not pregnant were larger in size (5.5 g) than non-reproductive females (4.4 g). Response of least shrews to live traps was not neophobic; and, in fact, about 30% of the shrews were captured on day 1 of a 4-day trapping period on prairie sites. Our data add information about attributes of least shrews living in natural habitats, such as the tallgrass prairie, and support two previous studies, which suggested that least shrews are rare on Konza Prairie.
Keywords: abundance; body size; Cryptotis parva; fire; Grazing; planted brome fields; reproduction; tallgrass prairie; trap response; woodland habitat

Linking plant growth responses across topographic gradients in tallgrass prairie - Jesse B. Nippert; Ocheltree, T.W.; Skibbe, A.M.; Kangas, L.C.; J.M. Ham; Shonkwiler-Arnold, K.B.; N. Brunsell (Oecologia, 2011)
Aboveground biomass in grasslands varies according to landscape gradients in resource availability and seasonal patterns of growth. Using a transect spanning a topographic gradient in annually burned ungrazed tallgrass prairie, we measured changes in the height of four abundant C4 grass species, LAI, biomass, and cumulative carbon flux using two closely located eddy flux towers. We hypothesized that seasonal patterns of plant growth would be similar across the gradient, but the magnitude of growth and biomass accumulation would vary by topographic position, reflecting spatial differences in microclimate, slope, elevation, and soil depth. Thus, identifying and measuring local growth responses according to topographic variability should significantly improve landscape predictions of aboveground biomass. For most of the growth variables measured, classifying topography into four positions best captured the inherent spatial variability. Biomass produced, seasonal LAI and species height increased from the upland and break positions to the slope and lowland. Similarly, cumulative carbon flux in 2008 was greater in lowland versus upland tower locations (difference of 64 g m−2 by DOY 272). Differences in growth by topographic position reflected increased production of flowering culms by Andropogon gerardii and Sorghastrum nutans in lowland. Varying growth responses by these species may be a significant driver of biomass and carbon flux differences by topographic position, at least for wet years. Using a digital elevation model to classify the watershed into topographic positions, we performed a geographically weighted regression to predict landscape biomass. The minimum and maximum predictions of aboveground biomass for this watershed had a large range (86–393 t per 40.4 ha), illustrating the drastic spatial variability in growth within this annually-burned grassland.
Keywords: ANPP; Eddy covariance; Flux footprint; LAI; Mesic grassland; topography

Long-term effects of climate change on grassland soil systems: A reciprocal transplant approach - Rostkowski, S.C. Jr. (Kansas State University, 2011)
Climate change predictions for the Great Plains region of North America include increased temperatures, changes to annual precipitation, and reduced growing season precipitation, which will likely alter grassland soil systems. To date, few studies have examined belowground community responses to predicted climate change scenarios, with fewer assessing long-term changes. My research focused on the impacts of long-term changes in precipitation and associated soil water content on belowground grassland systems (belowground plant biomass, soil carbon (C) and nitrogen (N) pools, microbial biomass C and N, and invertebrate communities) using recently collected samples from a long-term (16-yr) reciprocal core transplant between Konza Prairie Biological Station (MAP = 850 mm) and Kansas State Agricultural Research Center at Hays (MAP = 580 mm), with the Hays site having a long-term average annual precipitation amount that is ~30% less than the Konza site. Results from the experiment indicate that either increases or decreases in annual precipitation can have profound effects on belowground grassland systems. Belowground plant biomass, microbial biomass, and potential C mineralization rates were greater at the wetter Konza site regardless of soil origin. Total C stored in soils incubated at Konza was significantly greater as well, likely due to greater root inputs. The effects of precipitation were most apparent in the surface soil layers (0-20 cm), while soil origin impacted soil properties to a greater extent with increasing depth. This contrasted with results for the soil mesofauna, where total microarthropods responded negatively and nematodes responded positively to increased annual precipitation. Results of this study indicate important changes in soil C and N pools, belowground plant biomass, and soil mesofauna within grassland systems subject to changing precipitation regimes, and suggest more mesic prairie systems are more sensitive to changes in soil water availability than those in more arid grassland systems.
Keywords: Climate change; Grasslands; Microarthropods; Nematodes; Roots; Soil carbon

Multi-scale burned area mapping in tallgrass prairie using in situ spectrometry and satellite imagery - Mohler, R. (Kansas State University, 2011)
Prescribed burning in tallgrass prairie affects a wide range of human and natural systems. Consequently, managing this biome based on sound science, and with the concerns of all stakeholders taken into account, requires a method for mapping burned areas. In order to devise such a method, many different spectral ranges and spectral indices were tested for their ability to differentiate burned from unburned areas at both the field and satellite scales. Those bands and/or indices that performed well, as well as two different classification techniques and two different satellite-based sensors, were tested in order to come up with the best combination of band/index, classification technique, and sensor for mapping burned areas in tallgrass prairie. The ideal method used both the red and near-infrared spectral regions, used imagery at a spatial resolution of at least 250 m, used satellite imagery with daily temporal resolution, and used pixel-based classification techniques rather than object-based techniques. Using this method, burned area maps were generated for the Flint Hills for every year from 2000-2010, creating a fire history of the region during that time period. These maps were compared to active fire and burned area products, and these products were found to underestimate burned areas in tallgrass prairie.
Keywords: Burn mapping; Satellite imagery; tallgrass prairie

Mycorrhizal suppression alters plant productivity and forb establishment in a grass-dominated prairie restoration - McCain, K.N.S.; G.T. Wilson; John M. Blair (Plant Ecology, 2011)
A fundamental goal of restoration is the re-establishment of plant diversity representative of native vegetation. However, many prairie restorations or Conservation Reserve Program sites have been seeded with warm-season grasses, leading to grass-dominated, low-diversity restorations not representative of native grasslands. These dominant grasses are strongly mycotrophic, while many subordinate forb species appear to be less dependent on mycorrhizal symbiosis. Therefore, manipulating arbuscular mycorrhizal fungi (AMF) may be useful in promoting establishment and growth of forb species in grass-dominated prairie restorations. To assess the potential role of mycorrhizae in affecting the productivity and community composition of restored tallgrass prairie, we conducted a 4-year field experiment on an 8-year-old grassland restoration at the Konza Prairie in northeastern Kansas, USA. At the initiation of our study, seeds of 12 forb species varying in degree of mycorrhizal dependence were added to established grass-dominated plots. Replicate plots were treated bi-weekly with a soil drench of fungicide (Topsin-M®) over four growing seasons and compared to non-treated control plots to assess the role of AMF in affecting plant species composition, productivity, leaf tissue quality, and diversity in restored tallgrass prairie. Topsin applications successfully reduced mycorrhizal colonization of grass roots to approximately 60–80% relative to roots in control plots. Four years of mycorrhizal suppression reduced productivity of the dominant grasses and increased plant species richness and diversity. These results highlight the importance of mycorrhizae as mediators of plant productivity and community dynamics in restored tallgrass prairie and indicate that temporarily suppressing AMF decreases productivity of the dominant C4 grasses and allows for establishment of seeded forb species
Keywords: Arbuscular mycorrhizal fungi; forbs; Fungicide; Grassland restoration; Warm-season grass

Nitrous oxide emission from denitrification in stream and river networks - Beaulieu, J.K.; Tank, J.L.; Hamilton, S.K.; Wollheim, W.M.; Hall, R.O.; Mulholland, P.J.; Peterson, B.J.; L.R. Ashkenas; Cooper, L.W.; Dahm, C.N.; W. K. Dodds; Grimm, N.B.; et al. (Proceedings of the National Academy of Sciences of the United States of America, 2011)
Nitrous oxide (N2O) is a potent greenhouse gas that contributes to climate change and stratospheric ozone destruction. Anthropogenic nitrogen (N) loading to river networks is a potentially important source of N2O via microbial denitrification that converts N to N2O and dinitrogen (N2). The fraction of denitrified N that escapes as N2O rather than N2 (i.e., the N2O yield) is an important determinant of how much N2O is produced by river networks, but little is known about the N2O yield in flowing waters. Here, we present the results of whole-stream 15N-tracer additions conducted in 72 headwater streams draining multiple land-use types across the United States. We found that stream denitrification produces N2O at rates that increase with stream water nitrate (NO3−) concentrations, but that <1% of denitrified N is converted to N2O. Unlike some previous studies, we found no relationship between the N2O yield and stream water NO3−. We suggest that increased stream NO3− loading stimulates denitrification and concomitant N2O production, but does not increase the N2O yield. In our study, most streams were sources of N2O to the atmosphere and the highest emission rates were observed in streams draining urban basins. Using a global river network model, we estimate that microbial N transformations (e.g., denitrification and nitrification) convert at least 0.68 Tg·y−1 of anthropogenic N inputs to N2O in river networks, equivalent to 10% of the global anthropogenic N2O emission rate. This estimate of stream and river N2O emissions is three times greater than estimated by the Intergovernmental Panel on Climate Change. Humans have more than doubled the availability of fixed nitrogen (N) in the biosphere, particularly through the production of N fertilizers and the cultivation of N-fixing crops (1). Increasing N availability is producing unintended environmental consequences including enhanced emissions of nitrous oxide (N2O), a potent greenhouse gas (2) and an important cause of stratospheric ozone destruction (3). The Intergovernmental Panel on Climate Change (IPCC) estimates that the microbial conversion of agriculturally derived N to N2O in soils and aquatic ecosystems is the largest source of anthropogenic N2O to the atmosphere (2). The production of N2O in agricultural soils has been the focus of intense investigation (i.e., >1,000 published studies) and is a relatively well constrained component of the N2O budget (4). However, emissions of anthropogenic N2O from streams, rivers, and estuaries have received much less attention and remain a major source of uncertainty in the global anthropogenic N2O budget. Microbial denitrification is a large source of N2O emissions in terrestrial and aquatic ecosystems. Most microbial denitrification is a form of anaerobic respiration in which nitrate (NO3−, the dominant form of inorganic N) is converted to dinitrogen (N2) and N2O gases (5). The proportion of denitrified NO3− that is converted to N2O rather than N2 (hereafter referred to as the N2O yield and expressed as the mole ratio) partially controls how much N2O is produced via denitrification (6), but few studies provide information on the N2O yield in streams and rivers because of the difficulty of measuring N2 and N2O production in these systems. Here we report rates of N2 and N2O production via denitrification measured using whole-stream 15NO3−-tracer experiments in 72 headwater streams draining different land-use types across the United States. This project, known as the second Lotic Intersite Nitrogen eXperiment (LINX II), provides unique whole-system measurements of the N2O yield in streams. Although N2O emission rates have been reported for streams and rivers (7, 8), the N2O yield has been studied mostly in lentic freshwater and marine ecosystems, where it generally ranges between 0.1 and 1.0%, although yields as high as 6% have been observed (9). These N2O yields are low compared with observations in soils (0–100%) (10), which may be a result of the relatively lower oxygen (O2) availability in the sediments of lakes and estuaries. However, dissolved O2 in headwater streams is commonly near atmospheric equilibrium and benthic algal biofilms can produce O2 at the sediment–water interface, resulting in strong redox gradients more akin to those in partially wetted soils. Thus, streams may have variable and often high N2O yields, similar to those in soils (11). The N2O yield in headwater streams is of particular interest because much of the NO3− input to rivers is derived from groundwater upwelling into headwater streams. Furthermore, headwater streams compose the majority of stream length within a drainage network and have high ratios of bioreactive benthic surface area to water volume (12).

Normalization and centering of array-based heterologous genome hybridization based on divergent control probes - Darby, B.J.; Jones, K.L.; Wheeler, D.; Herman, M.A. (BMC Bioinformatics, 2011)
Background Hybridization of heterologous (non-specific) nucleic acids onto arrays designed for model-organisms has been proposed as a viable genomic resource for estimating sequence variation and gene expression in non-model organisms. However, conventional methods of normalization that assume equivalent distributions (such as quantile normalization) are inappropriate when applied to non-specific (heterologous) hybridization. We propose an algorithm for normalizing and centering intensity data from heterologous hybridization that makes no prior assumptions of distribution, reduces the false appearance of homology, and provides a way for researchers to confirm whether heterologous hybridization is suitable. Results Data are normalized by adjusting for Gibbs free energy binding, and centered by adjusting for the median of a common set of control probes assumed to be equivalently dissimilar for all species. This procedure was compared to existing approaches and found to be as successful as Loess normalization at detecting sequence variations (deletions) and even more successful than quantile normalization at reducing the accumulation of false positive probe matches between two related nematode species, Caenorhabditis elegans and C. briggsae. Despite the improvements, we still found that probe fluorescence intensity was too poorly correlated with sequence similarity to result in reliable detection of matching probe sequence. Conclusions Cross-species hybridizations can be a way to adapt genome-enabled tools for closely related non-model organisms, but data must be appropriately normalized and centered in a way that accommodates hybridization of nucleic acids with diverged sequence. For short, 25-mer probes, hybridization intensity alone may be insufficiently correlated with sequence similarity to allow reliable inference of homology at the probe level.

Nutrient loading and grazing by the minnow Phoxinus erythrogaster shift periphyton abundance and stoichiometry in mesocosms - Kohler, T.J.; Murdock, J.N.; K. B. Gido; W. K. Dodds (Freshwater Biology, 2011)
1. Anthropogenic activities in prairie streams are increasing nutrient inputs and altering stream communities. Understanding the role of large consumers such as fish in regulating periphyton structure and nutritional content is necessary to predict how changing diversity will interact with nutrient enrichment to regulate stream nutrient processing and retention. 2. We characterised the importance of grazing fish on stream nutrient storage and cycling following a simulated flood under different nutrient regimes by crossing six nutrient concentrations with six densities of a grazing minnow (southern redbelly dace, Phoxinus erythrogaster) in large outdoor mesocosms. We measured the biomass and stoichiometry of overstory and understory periphyton layers, the stoichiometry of fish tissue and excretion, and compared fish diet composition with available algal assemblages in pools and riffles to evaluate whether fish were selectively foraging within or among habitats. 3. Model selection indicated nutrient loading and fish density were important to algal composition and periphyton carbon (C): nitrogen (N). Nutrient loading increased algal biomass, favoured diatom growth over green algae and decreased periphyton C : N. Increasing grazer density did not affect biomass and reduced the C : N of overstory, but not understory periphyton. Algal composition of dace diet was correlated with available algae, but there were proportionately more diatoms present in dace guts. We found no correlation between fish egestion/excretion nutrient ratios and nutrient loading or fish density despite varying N content of periphyton. 4. Large grazers and nutrient availability can have a spatially distinct influence at a microhabitat scale on the nutrient status of primary producers in streams.

Observation of porcupine in Geary County, Kansas - D.W. Kaufman; Kaufman, G.A. (Transactions of the Kansas Academy of Science, 2011)

Patterns of macroinvertebrate production, trophic structure, and energy flow along a tallgrass prairie stream continuum - Whiting, D.P.; M.R. Whiles; Stone, M.L. (Limnology and Oceanography, 2011)
We estimated benthic organic matter standing stocks, macroinvertebrate production, food-web structure, and stream metabolism along a longitudinal continuum of Kings Creek at Konza Prairie Biological Station in Kansas. Benthic macroinvertebrates were sampled for 1 yr from three stream reaches (grass, shrub, gallery forest). Total habitat-weighted production ranged from 9.1 g to 31.9 g ash-free dry weight m−2 yr−1 with the grass headwaters accounting for the highest production. Functional group contributions to production were similar along the continuum, with collector–gatherers (40–56% of total) and predators (23–38%) dominating all reaches. Detrital pathways appeared to account for most energy flow in all reaches, and all reaches were net heterotrophic on all dates when metabolism was measured, except for the grass headwater reach in spring. Predators were well-represented and consumed 65–107% of total macroinvertebrate production, whereas scrapers (11–15%), shredders (2–4%), and filterers (< 1%) consumed relatively small percentages of available resources. Dominance of predators suggested top-down controls are important in this system. However, changes in energy flow through other groups reflected longitudinal variation in resource availability. This prairie stream continuum conforms to some predictions of conceptual stream continua models, but biotic interactions, which are often not considered, may override some predicted responses to changes in the physical template.

Patterns of trait convergence and divergence among native and exotic species in herbaceous plant communities are not modified by nitrogen enrichment - Cleland, E.E.; Clark, C.M.; Scott. L. Collins; Fargione, J.E.; Gough, L.; Gross, K.L.; Pennings, S.C.; K.N. Suding (Journal of Ecology, 2011)

Physiological drought tolerance and the structuring of tallgrass assemblages - Tucker, S.S.; Craine, J.M.; Jesse B. Nippert (Ecosphere, 2011)
Drought is a defining characteristic of many grasslands worldwide. Yet we have little understanding of how drought structures grassland communities and the degree to which physiological drought tolerance advantages plants in grasslands. We characterized physiological drought tolerance (Ψcrit) for a large number of species in a mesic grassland community (Konza Prairie, KS, USA). We then examined the relationships between Ψcrit and a number of other key functional traits, and tested whether physiological tolerance of drought underlay success across a number of ecological contrasts—topographic position, burn frequency, and grazing—with 17 years of abundance data. Physiological drought tolerance of Konza species covered almost the full range known to plants globally. Consistently, physiologically drought-tolerant species had thin roots, while associations with other traits were inconsistent across functional groups. In this mesic grassland, physiological drought tolerance appears to increase the abundance of plants in xeric uplands, but does not in the mesic lowlands. Physiological drought tolerance did not alter species responses to changes in burning or grazing. In contrast to Ψcrit, species with high root tissue density were more abundant in uplands and lowlands than species with low root tissue density largely irrespective of grazing or burning regimes. In all, drought appears to have a limited role in structuring the Konza plant community. As such, more severe or frequent droughts in the region would likely restructure the Konza plant community in ways that are currently not observable.

Population genetic structure and landscape connectivity of the Eastern Yellowbelly Racer (Coluber constrictor flaviventris) in the contiguous tallgrass prairie of northeastern Kansas, USA - Klug, P.E.; Wisely, S.M.; With, K.A. (Landscape Ecology, 2011)
The tallgrass prairie of North America has undergone widespread habitat loss and fragmentation (<4% remains). The Flint Hills region of Kansas and Oklahoma is the largest tallgrass prairie remaining and therefore provides an opportunity to study the population genetic structure of grassland species in a relatively contiguous landscape and set a baseline for evaluating changes when the habitat is fragmented. We adopted a landscape genetics approach to identify how landscape structure affected dispersal, population genetic structure, and landscape connectivity of the Eastern Yellowbelly Racer (Coluber constrictor flaviventris) across a 13,500-km2 landscape in northeastern Kansas, USA. The racer population had high allelic diversity, high heterozygosity, and was maintaining migration-drift equilibrium. Autocorrelation between genetic and geographic distance revealed that racers exhibited restricted dispersal within 3 km, and isolation-by-distance. Significant isolation-by-distance occurred at broad regional scales (>100 km), but because of sufficient gene flow between locations, we were unable to define discrete subpopulations using Bayesian clustering analyses. Resistance distance, which considers the permeability of habitats, did not explain significant variation in genetic distance beyond Euclidean distance alone, suggesting that racers are not currently influenced by landscape composition. In northeastern Kansas, racers appear to be an abundant and continuously distributed snake that perceives the landscape as well connected with no cover type currently impeding snake dispersal or gene flow.
Keywords: Autocorrelation; conservation; dispersal; Fragmentation; Gene flow; grassland; Isolation-by-distance; Landscape genetics; Microsatellites; Snake

Positive feedbacks amplify rates of woody encroachment in mesic tallgrass prairie - Z. Ratajczak; Jesse B. Nippert; Hartman, J.C.; Ocheltree, T.W. (Ecosphere, 2011)
Over the last century, many grasslands worldwide have transitioned from a graminoid to a tree/shrub-dominated state in a short period of time, a phenomenon referred to as woody encroachment. Positive feedbacks and bi-stability are thought to be important drivers of woody encroachment, but there is little empirical evidence to suggest that positive feedbacks accelerate the woody encroachment of mesic grasslands. In mesic tallgrass prairie, shrub establishment does not directly facilitate seedling establishment. Yet, shrub establishment may facilitate the clonal spread of existing shrubs into nearby patches, because clonal reproduction might circumvent barriers that typically limit woody seedlings. Our results show that when Cornus drummondii (the predominate encroacher of mesic tallgrass prairie) extends rhizomatous stems into open grasslands, these stems use the same deep soil water sources as mature stems—thereby avoiding competition with grasses and gaining access to a reliable water source. In addition, herbaceous fuel concentrations are lower at the shrub/grass interface than in open grasslands, reducing the potential impacts of subsequent grassland fires. We propose that the release from resource and fire limitation results in a positive feedback loop as clonal stems are able to extend into surrounding patches, circumvent demographic barriers, mature, and spread by developing their own clonal stems. Long-term data on site (26 years) corroborates this interpretation: the size of deep-rooted clonal shrub species has increased 16-fold and their cover has increased from 0 to 27%, whereas the cover of shallow-rooted species (both clonal and non-clonal) has only increased marginally. Together, these results suggest that (1) positive feedbacks can facilitate mesic woody encroachment and (2) bi-stability exists in mesic tallgrass prairie.

Potential ecological impacts of switchgrass (Panicum virgatum L.) biofuel cultivation in the Central Great Plains, USA - Hartman, J.C.; Jesse B. Nippert; Orozco, R.A.; Springer, C.J. (Biomass and Bioenergy, 2011)
Switchgrass (Panicum virgatum L.) is a broadly adapted warm-season grass species native to most of the central and eastern United States. Switchgrass has been identified as a potential biofuel species because it is a native species that requires minimal management, and has a large potential to sequester carbon underground. Since the 1990’s, switchgrass has been bred to produce cultivars with increased biomass and feedstock quality. This review addresses potential ecological consequences of widespread switchgrass cultivation for biofuel production in the central United States. Specifically, this review address the ecological implications of changing use of marginal and CRP land, impacts on wildlife, potentials for disease and invasions, and changes in soil quality through reductions in erosion, decomposition rates, and carbon sequestrations. A central theme of the review is the utility of maintaining landscape heterogeneity during switchgrass biofuel production. This includes implementing harvest rotations, no till farming, and mixed species composition. If negative ecological consequences of switchgrass cultivation are minimized, biofuel production using this species has economical and environmental benefits.
Keywords: Carbon sequestration; Crop rotation; CRP land; Landscape heterogeneity; Marginal land; SOC

Productivity is a poor predictor of plant species richness - P. Adler; Seabloom, E.W.; E.T. Borer; Hillebrand, H.; Hautier, Y.; Hector, A.; Harpole, W.S.; O'Halloran, L.R.; Grace, J.B.; Anderson, T.M.; J.D. Bakker; L.A. Biederman; et al. (Science, 2011)
For more than 30 years, the relationship between net primary productivity and species richness has generated intense debate in ecology about the processes regulating local diversity. The original view, which is still widely accepted, holds that the relationship is hump-shaped, with richness first rising and then declining with increasing productivity. Although recent meta-analyses questioned the generality of hump-shaped patterns, these syntheses have been criticized for failing to account for methodological differences among studies. We addressed such concerns by conducting standardized sampling in 48 herbaceous-dominated plant communities on five continents. We found no clear relationship between productivity and fine-scale (meters−2) richness within sites, within regions, or across the globe. Ecologists should focus on fresh, mechanistic approaches to understanding the multivariate links between productivity and richness.

Regional and interspecific variation in Sr, Ca, and Sr/Ca ratios in avian eggshells from the USA - Mora, M.A.; Brattin, B.; Baxter, C.; Rivers, J.W. (Ecotoxicology, 2011)
To examine regional variation in strontium (Sr), which at high concentrations may reduce eggshell quality, increase egg breakage and reproductive failure, we analyzed Sr, and calcium (Ca) concentrations and Sr/Ca ratios in eggshells from 20 avian species from California, Texas, Idaho, Kansas, and Michigan. In addition, we included data previously reported from Arizona to expand the regional comparisons and to better establish patterns of Sr, and Sr/Ca ratios in bird species across the United States. We found Sr concentrations varied significantly among regions, among species, and among foraging guilds; this variability is strongly influenced by the Sr/Ca ratios in surface water from locations close to the region where the eggshells were collected. Sr concentrations and Sr/Ca ratios were significantly higher in bird eggshells from the Volta wildlife region in the San Joaquin Valley, California and in various locales from Arizona. Sr concentrations and Sr/Ca ratios in bird eggshells from other locations in the USA were lower than those detected in these two regions. Among foraging guilds, invertivores had the highest Sr concentrations and Sr/Ca ratios and carnivores had the lowest. In general, the Sr/Ca ratio increased strongly with increasing Sr concentrations (R2 = 0.99, P < 0.0001). There was a significant correlation (R2 = 0.58, P < 0.0001) between Sr/Ca ratios in water and the average Sr/Ca ratios in eggshells suggesting that these values could be determined from Sr/Ca ratios in water. Eggshell thickness was poorly correlated with Sr (R2 = 0.03) but had a significant and positive correlation with Ca and was more properly correlated by a quadratic equation (R2 = 0.50, Thickness = 2.13 − 0.02Ca − 3.07 * 10−5Ca2). Our study provides further evidence that Sr accumulates significantly in the avian eggshell, in some regions at concentrations which could be of concern for potential negative effects on reproduction. We suggest that when assessing the effects of metals on avian reproduction in regions with high Sr deposits in rock and soil, Sr concentrations in the eggshell also should be measured to evaluate additional effects on thickness and reproduction.
Keywords: Avian eggshell; Calcium (Ca); Sr/Ca ratios; Strontium (Sr)

Relative effects of precipitation variability and warming on tallgrass prairie ecosystem function - Fay, P.A.; John M. Blair; M.D. Smith; Jesse B. Nippert; Carlisle, J.D.; Alan K. Knapp (Biogeosciences, 2011)
Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenarios predict increasing precipitation variability and temperature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual) rainfall variability, and warming. We present results from an experiment applying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ~50–200% interannual variability in plant growth and aboveground net primary productivity (ANPP), leaf carbon assimilation (ACO2), and soil CO2 efflux (JCO2) despite only ~40% variation in mean volumetric soil water content (0–15 cm, Θ15). Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Differences between years in Θ15 explained the greatest portion (14–52%) of the variation in these processes. Experimentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture variation and reduced Θ15 by 15%, causing most ecosystem processes to decrease 8–40% in some or all years with increased rainfall variability compared to ambient rainfall timing, suggesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, particularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter JCO2, and reduced summer JCO2 and forb ANPP, suggesting that the effects of warming differed in cooler versus warmer parts of the year. We conclude that (1) major ecosystem processes in this grassland may be substantially altered by predicted changes in interannual climate variability, intra-annual rainfall variability, and temperature, (2) interannual climate variation was a larger source of variation in ecosystem function than intra-annual rainfall variability and warming, and (3) effects of increased growing season rainfall variability and warming were small, but ecologically important. The relative effects of these climate drivers are likely to vary for different ecosystem processes and in wetter or drier ecosystems.

Reproductive biology of a southern population of Greater Prairie-Chickens - McNew, L.B.; Gregory, A.J.; Wisely, S.M.; Sandercock, B.K. (Studies in Avian Biology, 2011)

Responses of switchgrass (Panicum virgatum L.) to precipitation amount and temperature - Hartman, J.C. (Kansas State University, 2011)
Anthropogenic climate change is likely to alter the function and composition of ecosystems worldwide through increased precipitation variability and temperatures. To predict ecosystem responses, a greater understanding of the physiological and growth responses of plants is required. Dominant species drive ecosystem responses, and it is essential to understand how they respond to understand potential ecosystem changes. Dominant species, such as switchgrass (Panicum virgatum L.), posses large genotypic and phenotypic variability, which will impact the degree of responses to projected climate changes. I studied the physiological and growth responses of switchgrass, a common perennial warm-season C4 grass that is native to the tallgrass prairie, to alterations in precipitation amount and temperature. The first experiment I conducted focused on the responses of three ecotypes of P. virgatum to three precipitation regimes (average, 25% below, 25% above). I concluded that the physiological responses of photosynthesis, stomatal conductance, transpiration, dark-adapted fluorescence, and mid-day water potential in P. virgatum were explained by ecotypic differences. Robust responses to altered precipitation were seen in the water use efficiency, mid-day water potential, and aboveground biomass. Ecotypic differences were also seen in several aboveground biomass variables, and most strikingly in flowering times and rates. There were few interactions between ecotype and precipitation, suggesting precipitation is a strong driver of biomass production, whereas adaption of ecotypes to their local environment affects physiological processes. A second experiment studied the response of local populations of P. virgatum to nocturnal warming. Results showed significant differences in daytime E, daytime gs, and flowering phenology between treatments. Differences in aboveground biomass were between topographic positions. I concluded that water availability, based on topographic position, is a strong driver of P. virgatum aboveground biomass production, but nocturnal warming has the potential to impact flowering phenology, physiological responses, and exacerbate plant water stress. I also reviewed the literature on the ecological effects of implementing switchgrass cultivation for biofuel. From the literature review, I concluded that large-scale switchgrass cultivation will have widespread ecological impacts. If landscape heterogeneity is maintained through harvest rotations, no till farming, and mixed species composition, ecosystem services can be maintained while providing economic value.
Keywords: Aboveground biomass; Biofuel; Climate change; Ecophysiology; grassland

Rhus glabra response to season and intensity of fire in tallgrass prairie - K.M. Hajny; D.C. Hartnett; G.T. Wilson (International Journal of Wildland Fire, 2011)
Altered fire regimes play a key role in shrub expansion in grasslands worldwide. We assessed how season and type or intensity of fire affected the growth and demography of Rhus glabra, a common woody invader in North American mesic grasslands. Fire during any season killed 99% of ramets but stimulated new ramet recruitment from belowground buds, resulting in a near-complete turnover of ramet populations. During the first 2 years following fire, populations on spring-burned sites had the greatest post-fire ramet densities and population growth rates, and winter- and spring-burned populations showed the highest resprouting rates. However, after 10 years, R. glabra cover on summer-burned sites was 3.5 times greater than on autumn- or winter-burned treatments. Thus, short-term post-fire responses may not be good predictors of long-term changes in abundance. Low-intensity spring backfires resulted in the highest ramet population growth rates, whereas high-intensity headfires in any season resulted in slower growth, and populations burned with low-intensity winter fires declined. In addition, season of fire influenced browsing pressure, suggesting that plant responses may be partially a result of indirect effects of fire on rates of herbivory. Overall, our results demonstrate that the application of frequent autumn or winter backfires is an effective management tool for limiting R. glabra expansion in grasslands, and that long-term data are critical for management decision-making, particularly in systems characterised by high interannual climate variability.
Keywords: shrub demography; shrub encroachment; smooth sumac

Root dynamics of cultivar and non‐cultivar population sources of two dominant grasses during initial establishment of tallgrass prairie - Klopf, R.P.; S.G. Baer (Restoration Ecology, 2011)
Dominance of warm-season grasses modulates tallgrass prairie ecosystem structure and function. Reintroduction of these grasses is a widespread practice to conserve soil and restore prairie ecosystems degraded from human land use changes. Seed sources for reintroduction of dominant prairie grass species include local (non-cultivar) and selected (cultivar) populations. The primary objective of this study was to quantify whether intraspecific variation in developing root systems exists between population sources (non-cultivar and cultivar) of two dominant grasses (Sorghastrum nutans and Schizachyrium scoparium) widely used in restoration. Non-cultivar and cultivar grass seedlings of both species were isolated in an experimental prairie restoration at the Konza Prairie Biological Station. We measured above- and belowground net primary production (ANPP and BNPP, respectively), root architecture, and root tissue quality, as well as soil moisture and plant available inorganic nitrogen (N) in soil associated with each species and source at the end of the first growing season. Cultivars had greater root length, surface area, and volume than non-cultivars. Available inorganic N and soil moisture were present in lower amounts in soil proximal to roots of cultivars than non-cultivars. Additionally, soil NO3–N was negatively correlated with root volume in S. nutans cultivars. While cultivars had greater BNPP than non-cultivars, this was not reflected aboveground root structure, as ANPP was similar between cultivars and non-cultivars. Intraspecific variation in belowground root structure and function exists between cultivar and non-cultivar sources of the dominant prairie grasses during initial reestablishment of tallgrass prairie. Population source selection should be considered in setting restoration goals and objectives.
Keywords: cultivar; dominant grasses; local ecotype; Roots; tallgrass prairie restoration

Soil microbial community carbon and nitrogen dynamics with altered precipitation regimes and substrate availability - Tiemann, L. (University of Kansas, 2011)
Understanding the nature and extent of the feedback between soil microorganisms and ecosystem processes is of great concern as we are faced with multiple elements of global environmental change. In this dissertation, I explore how anthropogenically induced environmental changes affect soil microorganisms' resource use, and how, in turn, changes in microbial resource use alters ecosystem processes. These explorations were conducted in grassland systems, which contain 12% of global soil carbon (C) stocks and can serve as large C sources or sinks depending on environmental conditions such as nitrogen (N) availability and precipitation regimes. Nitrogen availability in grasslands can control plant primary productivity as well as rates soil organic matter decomposition and the fate of soil organic C. In grassland systems undergoing N addition through fertilization, resource inputs to soils increase in both quality and quantity. In Chapter 1, I investigate the fate of enhanced biomass inputs due to N addition by determining the direct and indirect effects of N addition on the activity of the soil microbial decomposers. Through measurement of extracellular enzyme activities and isotopic analysis of the microbial biomass relative to substrate sources, I found enhanced mineralization of newly incorporated soil organic C with N addition. This increase in soil C break down was associated indirectly with N addition through increases in plant litter quality and not directly with increased soil N availability. These results suggest that increased biomass input resulting from N addition does not necessarily result in increased soil C accrual. Climate change in the Great Plains region will likely cause increases in drought severity and precipitation event size with little change in annual precipitation totals. Precipitation events, particularly those following periods of drought, can create large flushes of resources for microbial communities, but these same pulses also can cause high levels of physiological stress and disturbance. When faced with increased soil moisture stress and re-wetting disturbance, microorganisms must accumulate and release protective osmolytes. The acquisition and release of protective osmolytes, apparently of sufficient magnitude to influence ecosystem level N and C fluxes, makes understanding the mechanisms behind these fluxes critical for predicting not only microbial community responses to global change, but ecosystem responses as well. In Chapter 2, 3 and 4, I use soils from four locations across the Great Plains precipitation gradient in a combination of laboratory and in situ soil incubations to explore the effects of soil moisture stress on flows of C and N though the microbial biomass. In Chapter 2, I focus on links between soil moisture stress and resource use efficiency by manipulating the frequency and magnitude of soil wetting and drying cycles in laboratory soil incubations. As soil moisture stress was increased with longer drought intervals and larger water pulse events, I saw a decline in C use efficiency and a 360 - 4800% increase in net N mineralization in soils from four sites along the Great Plains precipitation gradient. In Chapter 3, I employed the use of stable isotopes at the end of a similar incubation, to trace the C and N during a soil wetting-drying cycle. In this study I found that increased levels of soil moisture stress shifted microbial preference from N-rich protective osmolytes to N-free osmolytes. I also found that soils from the mesic end of the precipitation gradient were more sensitive to changes in soil moisture stress than soils from the semi-arid end of the gradient and that nitrification appeared to be less sensitive than denitrification, leading to increased soil nitrate concentrations and a decoupling in the N cycle. Finally, in Chapter 4, I reciprocally transferred soils between four study sites along the precipitation gradient and allowed them to incubate in situ for 1.5 and 2.5 y. After collection I assessed nitrification and denitrification potentials and the abundance of functional genes associated with these processes. I compared effects of both the initial community composition and the change in environment on the process rates. I found that as soil moisture stress increased across the precipitation gradient, nitrification potential decreased and nitrification functional gene abundance increased. Depending on soil origin, denitrifiers were either sensitive, resistant or functionally redundant after 1.5 y of altered precipitation regimes. In contrast, after 2.5 y denitrifiers in soils of all origins exhibited declines in process rates and functional gene abundance with increased soil moisture stress. Overall, I found that microbial communities are sensitive to environmental change, and as these communities shift in structure and function C and N cycling in these grasslands is altered. In particular, the perturbations explored in this dissertation, N addition and climate change, may induce increased rates of C release and N loss from these grassland soils.

Soil moisture controls on temperature sensitivity of soil organic carbon decomposition for a mesic grassland - Craine, J.M.; Gelderman, T.M. (Soil Biology and Biochemistry, 2011)
We examined relationships between soil moisture and the temperature sensitivity of decomposition of labile soil organic carbon at a central North American grassland. For soils collected from shallow, xeric uplands, temperature sensitivity was greatest at intermediate soil moisture. For soils collected from the deeper, mesic lowlands, temperature sensitivity increased with increasing soil moisture. For example, lowland soils incubated at 75% WHC exhibited an apparent activation energy (Ea) that was 15 kJ mol−1 greater than soils incubated at 30% WHC, the equivalent of a Q10 of 2.8 vs. 2.3. Although further research is still needed to understand why moisture–temperature sensitivity relationships would differ between topographic positions, the magnitude of the soil moisture effect is large enough to alter soil C budgets and should be considered explicitly when predicting ecosystem responses to global change scenarios.
Keywords: grassland; Microbial respiration; soil moisture; Soil organic carbon; Temperature sensitivity; Warming

Soil texture affects soil microbial and structural recovery during grassland restoration - E.M. Bach; S.G. Baer; Meyer, C.K.; Six, J. (Soil Biology & Biochemistry, 2011)
Many biotic and abiotic factors influence recovery of soil communities following prolonged disturbance. We investigated the role of soil texture in the recovery of soil microbial community structure and changes in microbial stress, as indexed by phospholipid fatty acid (PLFA) profiles, using two chronosequences of grasslands restored from 0 to 19 years on silty clay loam and loamy fine sand soils in Nebraska, USA. All restorations were formerly cultivated fields seeded to native warm-season grasses through the USDA’s Conservation Reserve Program. Increases in many PLFA concentrations occurred across the silty clay loam chronosequence including total PLFA biomass, richness, fungi, arbuscular mycorrhizal fungi, Gram-positive bacteria, Gram-negative bacteria, and actinomycetes. Ratios of saturated:monounsaturated and iso:anteiso PLFAs decreased across the silty clay loam chronosequence indicating reduction in nutrient stress of the microbial community as grassland established. Multivariate analysis of entire PLFA profiles across the silty clay loam chronosequence showed recovery of microbial community structure on the trajectory toward native prairie. Conversely, no microbial groups exhibited a directional change across the loamy fine sand chronosequence. Changes in soil structure were also only observed across the silty clay loam chronosequence. Aggregate mean weighted diameter (MWD) exhibited an exponential rise to maximum resulting from an exponential rise to maximum in the proportion of large macroaggregates (>2000 μm) and exponential decay in microaggregates (<250 μm and >53 μm) and the silt and clay fraction (<53 μm). Across both chronosequences, MWD was highly correlated with total PLFA biomass and the biomass of many microbial groups. Strong correlations between many PLFA groups and the MWD of aggregates underscore the interdependence between the recovery of soil microbial communities and soil structure that may explain more variation than time for some soils (i.e., loamy fine sand). This study demonstrates that soil microbial responses to grassland restoration are modulated by soil texture with implications for estimating the true capacity of restoration efforts to rehabilitate ecosystem functions.
Keywords: Aggregates; Conservation Reserve Program (CRP); Microbial biomass; Phospholipid fatty acids; Soil microbial communities; tallgrass prairie

Spatial ecology of eastern yellow-bellied Racer (Coluber constrictor flaviventris) and Great Plains rat snake (Pantherophis emoryi) in a contiguous tallgrass-prairie landscape - Klug, P. E.; Fill, J.; With, K.A. (Herpetologica, 2011)
The Flint Hills region of Kansas and Oklahoma encompasses the largest, contiguous tallgrass prairie in North America and is an important conservation area for many tallgrass-prairie species. We conducted a radiotelemetry study with the use of temperature-sensitive transmitters to characterize the spatial ecology of two species of snakes within a portion of this contiguous grassland. We monitored Eastern Yellow-Bellied Racers (Coluber constrictor flaviventris) from 2006 to 2008 and Great Plains Rat Snakes (Pantherophis emoryi) from 2007 to 2008 at the Konza Prairie Biological Station in the northern Flint Hills. Although racers (mean  =  67.3 ± 10.6 m, n  =  12) and rat snakes (mean  =  41.3 ± 4.7 m, n  =  12) differed in the distance moved per day, they did not differ significantly in home-range size. The minimum convex polygon (MCP) home range averaged 11.45 ha (SE  =  3.06, n  =  12) for racers and 15.06 ha (SE  =  2.48, n  =  12) for rat snakes. By analyzing the autocorrelation of locations (Mantel correlograms), we found that racers exhibited irregular movements, whereas rat snakes exhibited long periods of inactivity between directed movements. The body temperatures of racers were significantly greater in woody (30.7 ± 0.4°C) than in grassy habitats (29.8 ± 0.3°C). The body temperatures of rat snakes were significantly greater aboveground (26.9 ± 0.3°C) than underground (26.1 ± 0.2°C). Our study benefits the conservation of native snakes by elucidating space requirements and providing a baseline for comparisons between contiguous and fragmented landscapes.
Keywords: Autocorrelation; Body temperature; Coluber constrictor; Flint Hills; Home range; Movement; Pantherophis emoryi; Radiotelemetry; Snake; Space use

Species abundance distributions and richness estimations in fungal metagenomics – lessons learned from community ecology - Unterseher, M.; Dorman, C.F.; A. Jumpponen; Moora, M.; Öpik, M.; Tedersoo, L.; Schnittler, M. (Molecular Ecology, 2011)
Results of diversity and community ecology studies strongly depend on sampling depth. Completely surveyed communities follow log-normal distribution, whereas power law functions best describe incompletely censused communities. It is arguable whether the statistics behind those theories can be applied to voluminous next generation sequencing data in microbiology by treating individual DNA sequences as counts of molecular taxonomic units (MOTUs). This study addresses the suitability of species abundance models in three groups of plant-associated fungal communities – phyllosphere, ectomycorrhizal and arbuscular mycorrhizal fungi. We tested the impact of differential treatment of molecular singletons on observed and estimated species richness and species abundance distribution models. The arbuscular mycorrhizal community of 48 MOTUs was exhaustively sampled and followed log-normal distribution. The ectomycorrhizal (153 MOTUs) and phyllosphere (327 MOTUs) communities significantly differed from log-normal distribution. The fungal phyllosphere community in particular was clearly undersampled. This undersampling bias resulted in strong sensitivity to the exclusion of molecular singletons and other rare MOTUs that may represent technical artefacts. The analysis of abundant (core) and rare (satellite) MOTUs clearly identified two species abundance distributions in the phyllosphere data – a log-normal model for the core group and a log-series model for the satellite group. The prominent log-series distribution of satellite phyllosphere fungi highlighted the ecological significance of an infrequent fungal component in the phyllosphere community.

Testosterone mediates mating success in Greater Prairie-Chickens - Augustine, J.K.; Millspaugh, J.J.; Sandercock, B.K. (Studies in Avian Biology, 2011)

Thinking outside the channel: modeling nitrogen cycling in networked river ecosystems - Helton, A.M.; Poole, G.C.; Meyer, J.L.; Wollheim, W.M.; Peterson, B.J.; Mulholland, P.J.; Bernhardt, E.S.; Stanford, J.A.; Arango, C.P.; L.R. Ashkenas; Cooper, L.W.; W. K. Dodds; et al. (Frontiers in Ecology and the Environment, 2011)
Agricultural and urban development alters nitrogen and other biogeochemical cycles in rivers worldwide. Because such biogeochemical processes cannot be measured empirically across whole river networks, simulation models are critical tools for understanding river-network biogeochemistry. However, limitations inherent in current models restrict our ability to simulate biogeochemical dynamics among diverse river networks. We illustrate these limitations using a river-network model to scale up in situ measures of nitrogen cycling in eight catchments spanning various geophysical and land-use conditions. Our model results provide evidence that catchment characteristics typically excluded from models may control river-network biogeochemistry. Based on our findings, we identify important components of a revised strategy for simulating biogeochemical dynamics in river networks, including approaches to modeling terrestrial–aquatic linkages, hydrologic exchanges between the channel, floodplain/riparian complex, and subsurface waters, and interactions between coupled biogeochemical cycles.

Treated versus new traps: does chronic application of disinfectant to live traps reduce trappability of rodents? - Kaufman, G.A.; Kaufman, D.M.; D.W. Kaufman (Southwestern Naturalist, 2011)
We examined whether chronic exposure of traps to disinfectant reduced trappability of rodents as compared to new traps. We tested whether rodents initially chose between treated (disinfected) and new traps and if total number of captures differed between these treatments. Disinfectant did not reduce catchability of traps; rodents actually preferred treated traps. In initial pair-wise choice tests, rodents overall and the predominant North American deermouse, Peromyscus maniculatus, chose significantly more treated than new traps, although this difference disappeared as time of exposure of new traps in the environment increased. Total captures of small mammals and North American deermice did not differ between treated and new traps. Therefore, treated traps were never avoided; this has important implications in general, but especially for long-term studies where censuses are conducted using pre-disinfectant and post-disinfectant protocols.