Validating remotely sensed land surface fluxes in heterogeneous terrain with large aperture scintillometry - N. Brunsell; J.M. Ham; Arnold, K.A. (International Journal of Remote Sensing, 2011)
The Large Aperture Scintillometer (LAS) has emerged as one of the best tools for quantifying areal averaged fluxes over heterogeneous land surfaces. This is particularly useful as a validation of surface energy fluxes derived from satellite sources. We examine how changes in surface source area contributing to the scintillometer and eddy covariance measurements relate to satellite derived estimates of sensible heat flux. Field data were collected on the Konza Prairie in Northeastern Kansas, included data from two eddy covariance towers: one located on an upland, relatively flat homogeneous area, and the second located in a lowland area with generally higher biomass and moisture conditions. The large aperture scintillometer spanned both the upland and lowland areas and operated with a path length of approximately 1 km specifically to compare to Moderate Resolution Imaging Spectroradiometer (MODIS) derived estimates of surface fluxes. The upland station compares well with the LAS (correlation of 0.96), with the lowland station being slightly worse (correlation of 0.84). Data from the MODIS sensor was used to compute surface fluxes using the ‘triangle’ method which combines the remotely sensed data with a soil-vegetation-atmosphere-transfer scheme and a fully developed atmospheric boundary layer model. The relative contribution to the surface observations is estimated using a simple footprint model. As wind direction varies, the relative contribution of upland and lowland sources contributing to the LAS measurements varies while the MODIS pixel contribution remains relatively constant. With the footprint model, we were able to evaluate the relationship between the LAS observations and the remotely sensed estimates of the surface energy balance. The MODIS derived sensible heat flux values correspond better to the LAS measurements (percentage error: 0.04) when there was a larger footprint compared to a time with a smaller footprint (percentage error: −0.13). Results indicate that the larger the footprint, the better the agreement between satellite and surface observations.

Vegetation responses to an animal-generated disturbance (bison wallows) in tallgrass prairie - McMillan, B.R.; Pfeiffer, K.A.; D.W. Kaufman (American Midland Naturalist, 2011)
Bison (Bos bison) were a keystone species in the tallgrass prairie region of the Great Plains of North America. Cattle (Bos taurus) have been described as a functional equivalent to bison and have replaced bison in most of the grassland that remains intact. However, non-grazing behaviors influence grassland dynamics and are dissimilar between bison and cattle. Wallowing behavior (a non-grazing behavior by bison, but not cattle) creates disturbances (wallows) that were a common feature (may have numbered more than 100 million) of tallgrass prairie prior to extirpation of bison and conversion of most land to row-crop agriculture. We hypothesized that wallows are a unique disturbance that significantly influence both the structure and function of tallgrass prairie. We examined the response of plants to wallowing disturbances on Konza Prairie Biological Station, Kansas, where a herd of approximately 200 bison had year-round access to 1000 ha of native tallgrass prairie. We determined the influence of this disturbance type on aboveground net primary production (ANPP), plant species richness and diversity, and plant life form richness and diversity. The ANPP at the edge of wallowing disturbances was double the production in wallows and in adjacent prairie, which were not different from year to year. Plant species richness and diversity were significantly lower in wallows than at the edge of wallows and in adjacent prairie during all years of the study. However, composition of species were dissimilar among locations (e.g., 16% of all plant species samples were found only in the wallows); and, therefore, wallows increased the local and likely regional diversity of plant species. Likewise, wallowing disturbances increased local richness and diversity of plant life forms. It appears that these once common wallowing disturbances increase the diversity of tallgrass prairie beyond that of prairie that is grazed only (i.e., prairie with cattle).

Woody plant proliferation in North American drylands: A synthesis of impacts on ecosystem carbon balance - Barger, N.N.; S.R. Archer; Campbell, J.L.; C. Huang; Morton, J.A.; Alan K. Knapp (Journal of Geophysical Research, 2011)
[1] Changes in the magnitude and direction of ecosystem carbon (C) balance accompanying woody plant encroachment are among the largest contributors to the uncertainty in the North American C budget. In this synthesis we identify the important species contributing to woody encroachment, summarize our current knowledge of aboveground and belowground C storage change with woody encroachment, and evaluate the range of human and natural disturbance factors that alter the course of C gains and losses within ecosystems experiencing woody encroachment. Available data indicate that relative to the historic vegetation, aboveground net primary production (ANPP) decreases with woody plant encroachment in arid regions (mean annual precipitation (MAP) < 336 mm), but increases in semiarid and subhumid regions (on the order of 0.7 g C m−2 yr−1 per mm of MAP over 336 mm). Soil organic carbon response to woody plant encroachment ranged from losses of 6200 g C m−2 to gains of 2700 g C m−2 with an average accumulation of 385 g C m−2 across all studies and did not appear to be closely coupled to ANPP. Taken together, in the absence of disturbance, woody encroachment appears to result in a net ecosystem C gain across most species and ecoregions. However, disturbance associated with wildfire, land management practices, and drought may quickly and significantly offset these gains and should be explicitly factored into regional-scale C balance estimates. Our findings may be used to better constrain future estimates of woody plant encroachment influences on the North American C budget.

An analysis of greater prairie-chicken demography in Kansas: the effects of human land use on the population ecology of an obligate grassland species - McNew, L.B. (Kansas State University, 2010)

Brown-headed cowbird nestlings influence nestmate begging, but not parental feeding, in hosts of three distinct sizes - Rivers, J.W.; Loughin, T.M.; Rothstein, S.I. (Animal Behaviour, 2010)
Avian brood parasites typically depress the fitness of their hosts by reducing the number of host offspring produced, yet little is known about how parasitic nestlings influence the behaviour of host parents and host offspring. In this study, we used three hosts of the brown-headed cowbird, Molothrus ater, that varied in size (i.e. smaller, similar to and larger than cowbirds of a given age) to determine whether parasitic nestlings altered patterns of food provisioning by host parents and begging by host young under field conditions. Adult provisioning did not change in the presence of a cowbird but instead was influenced by feeding treatment and host size. In parasitized broods where nestlings differed in size (i.e. the small and large hosts), the larger nestling received the majority of food brought to the nest, regardless of whether it was the cowbird or host nestling. In contrast, similar-sized host nestlings received a similar amount of food in parasitized and unparasitized host broods. Relative to unparasitized broods, the presence of a cowbird led to increased begging intensity by the small host, had no clear effect on begging behaviour of the intermediate-sized host, and reduced begging intensity of the large host. Taken together, these results suggest the presence of a cowbird did not lead to changes in provisioning behaviour in parents, and the extent to which cowbirds influenced host begging behaviour depended on the size of the host.
Keywords: begging; brood parasitism; brown-headed cowbird; host–parasite interaction; Molothrus ater; offspring solicitation; parent feeding; provisioning behaviour

Bud bank density regulates invasion by exotic plants - Sprinkle, J.W. (Oklahoma State University, 2010)
Grasslands and savannas, which cover as much as 30-50% of the earth's ice-free land area, are affected by global environmental changes including biological invasions. To test the role of bud banks, an important feature of native prairie communities, in regulating invasion by exotic plants under three levels of simulated grazing (no clipping, 28 day clipping interval, and 14 day clipping interval) I conducted a greenhouse microcosm study. Using native rhizomes planted into native prairie soil, I established bud bank densities of 0, 30, 60, and 100% of mean tallgrass prairie bud bank density. Seeds of three exotic species were sown into each microcosm. The number of emerging and established exotic plants in each microcosm was counted every 14 days. I measured the aboveground biomass of each species at the end of the growing season (22 weeks). Assessments of exotic plant emergence, establishment, survivorship, reproduction, and biomass based on these measurements were compared using analysis of variance. The effects of the bud bank on exotic plant emergence, establishment, and survivorship were inconsistent and relatively weak. However, reproduction and biomass of exotic species were strongly influenced by bud bank density. In the absence of clipping, the biomass of exotic species was 675% higher at the lowest bud bank density than at the highest density. Furthermore, I found evidence for an invasibility threshold between 0-30% of mean field bud bank density in tallgrass prairie. These findings improve our understanding of plant invasion and suggest that restoring and maintaining bud banks should be a priority for land managers seeking to prevent and limit plant invasions.

Calibrating vegetation cover and pollen assemblages in the Flint Hills of Kansas, USA - Commerford, J.L. (Kansas State University, 2010)
The quantitative relationship between pollen assemblages in sediment and vegetation cover is largely unknown because many factors influence this relationship. This lack of quantitative relationship is particularly acute in grassland regions, where both past and future climate change have the potential to determine grassland composition and cover. The tool used to reconstruct past grassland cover is the relative abundance of distinct fossil pollen types preserved in sediment. However, the interpretation of grassland pollen assemblages as grassland vegetation types needs to be refined to improve these reconstructions. Using pollen found in the surface sediments from 24 artificially-constructed ponds in the Flint Hills ecoregion of Kansas, USA, I examined relationships between pollen and vegetation in the tallgrass prairie biome, which includes woody components. By comparing the pollen data to field-surveyed vegetation data and land cover classifications taken from Kansas Gap Analysis Program data, I correlated pollen and vegetation in this ecoregion. Pollen productivity estimates for Artemisia, Ambrosia, Asteraceae, Chenopodiaceae, Cornus, Fabaceae, Juniperus, Maclura, Poaceae, Populus, Quercus, and Salix were calculated via the Extended R-Value Model. Common pollen types identified in sediments are mostly herbaceous grassland plant species such as Poaceae, Artemisia, and Ambrosia, but woody plants such as Populus, Quercus, and Juniperus are also represented. PPEs have been calculated for four of these taxa in Europe, and values from the Flint Hills are higher. These are the first PPEs reported for eight of these taxa. This research will further advance quantitative vegetation reconstructions in the Great Plains of North America and refine interpretations of how climate change affects grasslands.
Keywords: grassland; Kansas- Flint Hills; Pollen; prairie vegetation

Climate change and cattle nutritional stress - Craine, J.M.; Elmore, A.J.; K.C. Olson; Tolleson, D. (Global Change Biology, 2010)
Owing to the complex interactions among climate, plants, cattle grazing, and land management practices, the impacts of climate change on cattle have been hard to predict. Predicting future grassland ecosystem functioning relies on understanding how changes in climate alter the quantity of forage produced, but also forage quality. Plant protein, which is a function of plant nitrogen concentrations, and digestible energy limit the performance of herbivores when in short supply; moreover, deficiencies can be expensive to mitigate. To better understand how changes in temperature and precipitation would affect forage protein and energy availability, we analyzed over 21 000 measurements of cattle fecal chemistry acquired over 14 years in the continental US. Our analysis of patterns in forage quality among ecologically defined regions revealed that increasing temperature and declining precipitation decreased dietary crude protein and digestible organic matter for regions with continental climates. Within regions, quality also declined with increased temperature; however, the effects of precipitation were mixed. Any future increases in precipitation would be unlikely to compensate for the declines in forage quality that accompany projected temperature increases. As a result, cattle are likely to experience greater nutritional stress in the future. If these geographic patterns hold as a proxy for future climates, agriculture will require increased supplemental feeds or the consequence will be a decrease in livestock growth.

Climate controls on grass culm production over a quarter century in a tallgrass prairie - Craine, J.M.; Towne, E.G.; Jesse B. Nippert (Ecology, 2010)
The flowering of grasses is a process critical to plant population dynamics and genetics, herbivore performance, and human health. To better understand the climate factors governing grass flowering, we analyzed the patterns of culm production over 25 years for three perennial tallgrass prairie species at Konza Prairie in Kansas, USA. The three species (Andropogon gerardii, Sorghastrum nutans, and Schizachyrium scoparium) all utilize the C4 photosynthetic pathway and were measured annually at the same locations for the past 25 years in an annually burned watershed. Culm production of all three species increased with higher growing-season soil moisture and precipitation but differed in their responses to water availability at different times during the growing season. Relative to Andropogon, Sorghastrum responded more to precipitation early in the growing season, and Schizachyrium responded more to precipitation late in the growing season. Flowering by each species also revealed a threshold relationship with late-season soil moisture at ~1 m depth, which likely is a proxy for season-long water balance. Although flowering can be influenced by conditions antecedent to the current growing season, neither soil moisture nor precipitation during the previous year influenced flowering over the 25-year period. Flowering culm production averaged 9% and 7% of total graminoid aboveground net primary production (ANPP) in the uplands and lowlands, respectively. Interannual variation in ANPP correlated only with Sorghastrum flowering, suggesting a predominant role of the species in ANPP responses to climate.

Climate forcings and the nonlinear dynamics of grassland ecosystems - Petrie, M. (University of Kansas, 2010)
The nonlinear interaction of climate forcings and ecosystem variables is instrumental in creating the temporal and spatial heterogeneity of grasslands. Ecosystem processes are a product of these interactions and vary in sensitivity to them across time. How forcings aggregate and shape ecosystem responses is an important aspect of grassland states and defines how they respond to changes in environmental conditions. Characterizing the relationship between climate drivers and ecosystem variables helps sharpen analysis of ecosystem flux dynamics during the growing season and identifies likely deviations from mean functioning. To address the question of how climate forcings and ecosystem variables interact to shape seasonal water and carbon dynamics in grasslands, this thesis is split into two analysis chapters. The first (Chapter 3) is a characterization of water and carbon flux responses to variable precipitation timing and magnitude. Particular focus is placed on temporal sensitivity to inputs, seasonality in water flux dynamics, and the linkage between precipitation, soil moisture, evapotranspiration, and potential evaporation. Chapter 4 extends International Panel on Climate Change (IPCC A1B) regional climate scenario projections for the Central Plains of the United States to assess mesic grassland responses. The specific focus is assessing the ecosystem response to increased precipitation variability, increased potential evaporation, and earlier growing season onset. Effects of these forcings are shaped by simulations of constant and seasonally-varying water-use efficiency to assess the role of vegetation on grassland carbon assimilation, and also to explore species-specific responses at the Konza Prairie in North Central Kansas, USA. Results from both chapters show variation in seasonal sensitivity of fluxes to precipitation, with varying relationships between drivers, variable conditions, and fluxes. This research provides for a better understanding of ecosystem processes and provides assessment of the magnitude and extent that forcing variation has on grassland function. Results from the second chapter show increased seasonal water and carbon flux variability and increased frequency of water stress conditions. Vegetation responses suggest climate change will impact species and habitat compositions through changing environmental conditions and partitioning of carbon assimilation periods. This illustrates potential effects to grassland functioning and growing season dynamics.

Community-level patterns of host use by the Brown-headed Cowbird (Molothrus ater), a generalist brood parasite - Rivers, J.W.; Jensen, W.E.; Kosciuch, K.L.; Rothstein, S.I. (Auk, 2010)
Quantifying community-level host use by generalist brood parasites is important because it provides a measure of the resources that parasites need for reproduction. During the 2002–2007 breeding seasons, we quantified host use by the Brown-headed Cowbird (Molothrus ater) at Konza Prairie Biological Station in northeast Kansas. Overall, 54.4% of nests (n = 2,621) of 22 passerine host species that typically accept parasitic eggs were parasitized, and parasitized nests contained an average of 1.9 ± 1.03 (SD) Brown-headed Cowbird eggs, nestlings, or both. Multiple parasitism was common on the study site in all years: 55.7% of parasitized nests (n = 1,425) received ≥2 Brown-headed Cowbird eggs. The Bell's Vireo (Vireo bellii; 70.5%) and the Dickcissel (Spiza americana; 69.6%) were parasitized at a significantly greater rate than the Red-winged Blackbird (Agelaius phoeniceus, 21.9%); collectively, these three species represented 85.8% of potential host nests found in all years. The host preference of Brown-headed Cowbirds did not appear to shift among the three species and instead they exhibited a consistent preference for Dickcissel nests over the course of the breeding season and among years. Both the rate and the intensity of parasitism on Dickcissels were significantly lower during the present study than in one conducted several decades earlier at the same site. Our results indicate that cowbirds in northeast Kansas differentially parasitize hosts, that most cowbird eggs are laid in the nests of a small number of host species, and that the Dickcissel appears to be preferred over other hosts.
Keywords: Agelaius phoeniceus; Bell's Vireo; brood parasitism; community-level parasitism; Dickcissel; host use; Molothrus ater; multiple parasitism; red-winged blackbird; Spiza americana; Vireo bellii

Comparative genome scan detects host-related divergent selection in the grasshopper Hesperotettix viridis - Apple, J.L.; Grace, T.; Anthony Joern; Amand, P.; Wisely, S.M. (Molecular Ecology, 2010)
In this study, we used a comparative genome scan to examine patterns of population differentiation with respect to host plant use in Hesperotettix viridis, a Nearctic oligophagous grasshopper locally specialized on various Asteraceae including Solidago, Gutierrezia, and Ericameria. We identified amplified fragment length polymorphism (AFLP) loci with significantly elevated FST (outlier loci) in multiple different-host and same-host comparisons of populations while controlling for geographic distance. By comparing the number and identities of outlier loci in different-host vs. same-host comparisons, we found evidence of host plant-related divergent selection for some population comparisons (Solidago- vs. Gutierrezia-feeders), while other comparisons (Ericameria- vs. Gutierrezia-feeders) failed to demonstrate a strong role for host association in population differentiation. In comparisons of Solidago- vs. Gutierrezia-feeding populations, a relatively high number of outlier loci observed repeatedly in different-host comparisons (35% of all outliers and 2.7% of all 625 AFLP loci) indicated a significant role for host-related selection in contributing to overall genomic differentiation in this grasshopper. Mitochondrial DNA sequence data revealed a star-shaped phylogeny with no host- or geography-related structure, low nucleotide diversity, and high haplotype diversity, suggesting a recent population expansion. mtDNA data do not suggest a long period of isolation in separate glacial refugia but are instead more compatible with a single glacial refugium and more recent divergence in host use. Our study adds to research documenting heterogeneity in differentiation across the genome as a consequence of divergent natural selection, a phenomenon that may occur as part of the process of ecological speciation.

Consumer return chronology alters recovery trajectory of stream ecosystem structure and function following drought - Murdock, J.M.; K. B. Gido; W. K. Dodds; Bertrand, K.N.; M.R. Whiles (Ecology, 2010)
Consumers are increasingly being recognized as important drivers of ecological succession, yet it is still hard to predict the nature and direction of consumer effects in nonequilibrium environments. We used stream consumer exclosures and large outdoor mesocosms to study the impact of macroconsumers (i.e., fish and crayfish) on recovery of intermittent prairie streams after drying. In the stream, macroconsumers altered system recovery trajectory by decreasing algal and macroinvertebrate biomass, primary productivity, and benthic nutrient uptake rates. However, macroconsumer influence was transient, and differences between exclosures and controls disappeared after 35 days. Introducing and removing macroconsumers after 28 days resulted mainly in changes to macroinvertebrates. In mesocosms, a dominant consumer (the grazing minnow Phoxinus erythrogaster) reduced macroinvertebrate biomass but had little effect on algal assemblage structure and ecosystem rates during recovery. The weak effect of P. erythrogaster in mesocosms, in contrast to the strong consumer effect in the natural stream, suggests that both timing and diversity of returning consumers are important to their overall influence on stream recovery patterns. Although we found that consumers significantly altered ecosystem structure and function in a system experiencing rapid changes in abiotic and biotic factors following disturbance, consumer effects diminished over time and trajectories converged to similar states with respect to primary producers, in spite of differences in consumer colonization history. Thus, consumer impacts can be substantial in recovering ecosystems and are likely to be dependent on the disturbance regime and diversity of the consumer community.

Contrasting ecosystem recovery on two soil textures: implications for carbon mitigation and grassland conservation - S.G. Baer; Meyer, C.K.; E.M. Bach; Klopf, R.P.; Six, J. (Ecosphere, 2010)
Understanding processes that promote or constrain ecosystem recovery from disturbance is needed to predict the restorative potential of degraded systems. We quantified a suite of ecosystem properties and processes across two chronosequences of restored grasslands on contrasting soil textures to test the hypothesis that restorations on silty clay loam soil would exhibit greater recovery of soil carbon (C) and nitrogen (N) pools and fluxes than on loamy fine sand because soil with higher clay content possesses a greater capacity to physico-chemically protect organic matter. Warm-season grass aboveground net primary productivity was similar between the two soil textures. Root biomass increased and root quality (as indexed by C:N ratio) decreased across both chronosequences. An asymptote in the accumulation of N in roots in the silty clay loam chronosequence resulted in wider C:N ratios of roots than in the loamy fine sand chronosequence. Total soil C (TC) and microbial biomass C (MBC) increased across the silty clay loam chronosequence at 21.2 and 5.7 g C·m−2·yr−1, respectively, and contained >6 times the amount of C in large macroaggregates and nearly 3 times the aggregate mean weighted diameter (MWD) relative to cultivated soil following 15 yrs of restoration. In contrast, there were no changes in TC, MBC, or MWD in the loamy fine sand chronosequence. Total and microbial biomass N increased at 2.0 and 0.27 g N·m−2·yr−1, respectively, across the silty clay loam chronosequence, and restored soil contained nearly 6 times large macroaggregate N than cultivated soil following 15 yrs of restoration. Potential net N mineralization rates declined with years of grass establishment in both soil textures, but overall rates were lower in the silty clay loam soil relative to the loamy fine sand, which was attributed to lower quality root systems, more improved soil structure, and larger microbial biomass. Thus, the potential for restored agricultural lands to mitigate CO2 emissions over the short term cannot be generalized across all soils. Lastly, the low restorative potential of cultivated loamy fine sand soil through grassland restoration within two decades (relevant to many conservation programs) underscores the need to prioritize preservation of remnant sand prairies.

Contrasting trait responses in plant communities to experimental and geographic variation in precipitation - Sandel, B.; Goldstein, L.J.; Kraft, N.J.; Okie, J.G.; Shuldman, M.I.; Ackerly, D.D.; Cleland, E.E.; K.N. Suding (New Phytologist, 2010)
•Patterns of precipitation are likely to change significantly in the coming century, with important but poorly understood consequences for plant communities. Experimental and correlative studies may provide insight into expected changes, but little research has addressed the degree of concordance between these approaches. •We synthesized results from four experimental water addition studies with a correlative analysis of community changes across a large natural precipitation gradient in the United States. We investigated whether community composition, summarized with plant functional traits, responded similarly to increasing precipitation among studies and sites. •In field experiments, increased precipitation favored species with small seed size, short leaf life span and high leaf nitrogen (N) concentration. However, with increasing precipitation along the natural gradient, community composition shifted towards species with higher mean seed mass, longer leaf life span and lower leaf N concentrations. •The differences in temporal and spatial scale of experimental manipulations and natural gradients may explain these contrasting results. Our results highlight the complexity of responses to climate change, and suggest that transient dynamics may not reflect long-term shifts in functional diversity and community composition. We propose a model of community change that incorporates these differences between short- and long-term responses to climate change.

Controls on bud activation and tiller initiation in tallgrass prairie: The effect of light and nitrogen - Williamson, M.M. (Oklahoma State University, 2010)
Chapter 1: Perennial grass populations in tallgrass prairie ecosystems are maintained primarily through vegetative outgrowth from their belowground bud banks. Resources in these ecosystems that have been found to limit plant productivity include nitrogen and light. I tested the Tomlinson and O'Connor (2004) theory, on the interactions of two environmental cues, nitrogen and light quantity, and the roles they have on bud outgrowth and tiller initiation in six perennial grass species in two functional groups (C 3 and C 4 photosynthetic pathways). I hypothesized that (1) an interaction between nitrogen and light availability regulated bud activation and tiller emergence in the two functional groups (C 3 species and C 4 species), (2) nitrogen would have the largest effect on the activation of buds, and (3) responses to the two environmental cues would differ between the two functional groups. Environmental growth chambers were used to conduct all studies, plants received one of three NH 4 NO 3 amendments or water (control), and were placed in a light treatment chamber or a dark (control) chamber. Strong interactions between nitrogen and light influenced bud outgrowth in the C c species, but not in the C 4 species. When I assessed the impacts of nitrogen as a key cue in tiller initiation in all six species, C 3 species responded favorably to N, while C 4 species did not. These results indicate that another abiotic environmental cue may be influencing the C 4 species. The results of this study suggest that environmental cues such as these that impact belowground bud bank dynamics in the tallgrass prairie have to potential to significantly impact grassland dynamics in response to current and future global changes. Chapter 2: Three species of C 3 grasses and three species of C 4 grasses were studied to test a proposed theory (Tomlinson and O'Connor 2004), to determine the role that light spectral quality (R:FR) and light quantity have on belowground bud outgrowth. I hypothesized that (1) R:FR will be an important cue in the regulation of bud bank dynamics, (2) reductions in light quantity due to litter accumulation will significantly reduce bud outgrowth, and (3) the response to the two factors will not be consistent across the two functional groups. Environmental growth chambers were used to conduct all study treatments. Plants were placed in chambers under one of three light treatments: light, reduced R:FR, or a full dark (control). To assess the effects of light availability under natural conditions, litter was used to reduce light availability in the C 4 species. Light spectral quality and quantity elicited species-specific responses in both of the functional groups. A suppression in bud outgrowth in response to R:FR reductions were observed in four of the six species. Alterations to light quantity due to litter accumulation did not reduce bud outgrowth, but a reduction in R:FR did, suggesting that light spectral quality is a more important regulator of bud dormancy and outgrowth than light intensity. Surprisingly, the response to light spectral quality and quantity were consistent across both functional groups. As we continue to seek answers to enhance rangeland quality, assessing how environmental cues are interacting may be a stronger predictor of how rangelands will respond to current and future global changes, than assessing the cues individually.

Data model for system conceptualization in groundwater studies - Yang, X.; Steward, D.R.; de Langeb, W.J.; Lauwoa, S.Y.; Chubb, R.M.; Bernard, E.A. (International Journal of Geographical Information Science, 2010)
Development of a conceptualization of a hydrogeologic system serves as the basis of groundwater modeling. While existing groundwater data models are designed to store groundwater system information, none is designed to capture its conceptual view. This study addresses this need by presenting a new object-oriented Conceptualization Groundwater Data Model that represents a groundwater system as a series of aquifer layers with defined aquifer properties and water boundary conditions. A case study is presented that develops the conceptual view of the groundwater system beneath Konza Prairie. This single conceptualization is used to support groundwater models across existing technologies of finite difference, finite element, and analytical element methods. While the models each employ different mathematics, data input files, and formats, all models are founded on the same conceptualization process that is represented using this new data model. The case study illustrates the data model's promise as an effective mechanism for groundwater system conceptualization and data storage, and utility for various groundwater computational models. This conceptualization of a groundwater data model suggests a new focus on incorporating system conceptualization into data model design.
Keywords: conceptualization; data model; groundwater; simulation

Development of soil microbial communities during tallgrass prairie restoration - Jangid, K.; Williams, M.A.; Franzluebbers, A.J.; John M. Blair; Coleman, D.C.; Whitman, W.B. (Soil Biology & Biochemistry, 2010)
Soil microbial communities were examined in a chronosequence of four different land-use treatments at the Konza Prairie Biological Station, Kansas. The time series comprised a conventionally tilled cropland (CTC) developed on former prairie soils, two restored grasslands that were initiated on former agricultural soils in 1998 (RG98) and 1978 (RG78), and an annually burned native tallgrass prairie (BNP), all on similar soil types. In addition, an unburned native tallgrass prairie (UNP) and another grassland restored in 2000 (RG00) on a different soil type were studied to examine the effect of long-term fire exclusion vs. annual burning in native prairie and the influence of soil type on soil microbial communities in restored grasslands. Both 16S rRNA gene clone libraries and phospholipid fatty acid analyses indicated that the structure and composition of bacterial communities in the CTC soil were significantly different from those in prairie soils. Within the time series, soil physicochemical characteristics changed monotonically. However, changes in the microbial communities were not monotonic, and a transitional bacterial community formed during restoration that differed from communities in either the highly disturbed cropland or the undisturbed original prairie. The microbial communities of RG98 and RG00 grasslands were also significantly different even though they were restored at approximately the same time and were managed similarly; a result attributable to the differences in soil type and associated soil chemistry such as pH and Ca. Burning and seasonal effects on soil microbial communities were small. Similarly, changing plot size from 300 m2 to 150 m2 in area caused small differences in the estimates of microbial community structure. In conclusion, microbial community structure and biochemical properties of soil from the tallgrass prairie were strongly impacted by cultivation, and the microbial community was not fully restored even after 30 years.
Keywords: 16S rRNA; Bacterial community; Cropland; PLFA; prairie; restoration

Dictyostelid cellular slime molds associated with grasslands of the central and western United States - Rollins, A.W.; Landolt, J.C.; Stephenson, S.L. (Mycologia, 2010)
Dictyostelid cellular slime molds (dictyostelids) associated with grassland ecosystems of the central and western United States were investigated at nine sites that included examples of the three major ecological types of grasslands (tall grass, mixed grass and short grass) generally recognized for the region. Samples of soil/humus collected from each site were examined with the Cavender method of isolating dictyostelids. For each of those six sites with well developed gallery forests present, an additional set of forest soil/humus samples was collected. A more intensive sampling effort was carried out at one site (Konza LTER) to assess the possible effects of burning and grazing on dictyostelid diversity and density. Twelve species of dictyostelids were recovered from grassland sites, whereas gallery forest sites yielded only nine species. Four cosmopolitan species (Dictyostelium giganteum, D. mucoroides, D. sphaerocephalum and Polysphondylium pallidum) were represented by the greatest densities of clones, with D. sphaerocephalum particularly common. The general pattern across all sites was that both species richness and density of dictyostelids decreased with decreasing precipitation. Samples collected from ungrazed grassland plots yielded higher numbers of both species and clones as compared to grazed plots, and the general pattern was for both values to increase as the interval between fires increased. For numbers of clones this correlation was statistically significant.
Keywords: biogeography ecology eumycetozoans grasslands

Disturbance mediated effects of stream fishes on ecosystem processes: concepts and results from highly variable prairie streams - K. B. Gido; Bertrand, K.N.; Murdock, J.N.; W. K. Dodds; M.R. Whiles (Advances in Stream Fish Community Ecology: Concepts, Approaches and Techniques, 2010)
Stream fishes can have strong top-down and bottom-up effects on ecosystem processes. However, the dynamic nature of streams constrains our ability to generalize these effects across systems with different disturbance regimes and species composition. To evaluate the role of fishes following disturbance, we used a series of field and mesocosm experiments that quantified the influence of grazers and water column minnows on primary productivity, periphyton structure, organic matter pools, and invertebrate communities following either scouring floods or drying of prairie streams. Results from individual experiments revealed highly significant effects of fishes, but the direction or magnitude of effects varied among experiments. Meta-analyses across experiments indicated that grazers consistently reduced the relative amount of fine benthic organic matter (FBOM) and chironomid abundance within 2 weeks after disturbances. However, effect sizes (log response ratios) were heterogeneous across experiments for algal biomass and algal filament lengths measured more than 4 weeks after a disturbance and potentially associated with system productivity and grazer densities. A similar analysis of 3–4 experiments using water column minnows only found a consistent trend of decreasing FBOM in fish treatments relative to controls when measured less than 2 weeks after disturbances and increase in gross primary productivity measured more than 4 weeks after disturbance. These results, along with those of others, were used to develop a conceptual framework for predicting the potential role of fishes in streams following disturbances (flood and drying). Both theoretical and empirical research shows that recovery of stream ecosystem processes will depend on the resilience of autotrophic and heterotrophic communities following disturbance. Fish effects may vary among functional groups but are generally predicted to be greatest during early stages of succession when algal and invertebrate communities are less complex and their biomass is low relative to fish biomass. Our analysis underscores the context dependency of consumer effects on ecosystem structure and function in nonequilibrium conditions and suggests that factors regulating fish densities and colonization of algal and invertebrate taxa need to be evaluated to predict the consequences of biodiversity loss in streams with variable or human-modified disturbance regimes.

Divergent host plant adaptation drives the evolution of reproductive isolation in the grasshopper Hesperotettix viridis (Orthoptera: Acrididae) - Grace, T.; Dowell, F.; Anthony Joern; Wisely, S.M.; Brown, S.J.; Maghirang, E. (Biological Journal of the Linnaean Society, 2010)
Early stages of lineage divergence in insect herbivores are often related to shifts in host plant use and divergence in mating capabilities, which may lead to sexual isolation of populations of herbivorous insects. We examined host preferences, degree of differentiation in mate choice, and divergence in cuticular morphology using near-infrared spectroscopy in the grasshopper Hesperotettix viridis aiming to understand lineage divergence. In Kansas (USA), H. viridis is an oligophagous species feeding on Gutierrezia and Solidago host species. To identify incipient mechanisms of lineage divergence and isolation, we compared host choice, mate choice, and phenotypic divergence among natural grasshopper populations in zones of contact with populations encountering only one of the host species. A significant host-based preference from the two host groups was detected in host-paired feeding preference studies. No-choice mate selection experiments revealed a preference for individuals collected from the same host species independent of geographic location, and little mating was observed between individuals collected from different host species. Female mate choice tests between males from the two host species resulted in 100% fidelity with respect to host use. Significant differentiation in colour and cuticular composition of individuals from different host plants was observed, which correlated positively with host choice and mate choice. No evidence for reinforcement in the zone of contact was detected, suggesting that divergent selection for host plant use promotes sexual isolation in this species.
Keywords: allopatry; ecological speciation; feeding preference; genetic divergence; host-associated divergence; mate choice; Microsatellites; near-infrared spectroscopy; reproductive isolation; secondary contact zones; sexual isolation; sympatry

Dominant grasses suppress local diversity in restored tallgrass prairie - McCain, K.N.S.; S.G. Baer; John M. Blair; G.T. Wilson (Restoration Ecology, 2010)
Warm-season (C4) grasses commonly dominate tallgrass prairie restorations, often at the expense of subordinate grasses and forbs that contribute most to diversity in this ecosystem. To assess whether the cover and abundance of dominant grass species constrain plant diversity, we removed 0, 50, or 100% of tillers of two dominant species (Andropogon gerardii or Panicum virgatum) in a 7-year-old prairie restoration. Removing 100% of the most abundant species, A. gerardii, significantly increased light availability, forb productivity, forb cover, species richness, species evenness, and species diversity. Removal of a less abundant but very common species, P. virgatum, did not significantly affect resource availability or the local plant community. We observed no effect of removal treatments on critical belowground resources, including inorganic soil N or soil moisture. Species richness was inversely correlated with total grass productivity and percent grass cover and positively correlated with light availability at the soil surface. These relationships suggest that differential species richness among removal treatments resulted from treatment induced differences in aboveground resources rather than the belowground resources. Selective removal of the dominant species A. gerardii provided an opportunity for seeded forb species to become established leading to an increase in species richness and diversity. Therefore, management practices that target reductions in cover or biomass of the dominant species may enhance diversity in established and grass-dominated mesic grassland restorations.
Keywords: Andropogon gerardii; Competition; diversity; mesic grassland restoration; Panicum virgatum; species removal

Ecosystem Processes of Prairie Streams and the Impact of Anthropogenic Alteration on Stream Ecological Integrity - Winders, K. (Kansas State University, 2010)
orth America has lost more than 95% of the original tallgrass prairie because of heavy land conversion, making prairie streams some of the most endangered habitats in North America. In order to effectively manage aquatic systems and improve biotic integrity of prairie streams research is needed that assesses the ecosystem characteristics of natural systems and evaluates the influence of anthropogenic alteration. We described the ecosystem characteristics of six ephemeral headwater streams draining tallgrass prairie within the Osage Plains of southwest Missouri. NO-3-N among all sites ranged from 1.56-91.36 μg L-1, NH+4-N ranged from 5.27-228.23 μg L-1, soluble reactive phosphorus ranged from below detection (1.0 μg L-1) to 41.22 μg L-1, TN ranged from 113.82-882.89 μg L-1, and TP ranged from 8.18-158.5 μg L-1during baseflow conditions. TN:TP molar ratios ranged from 22:1 to 53:1 indicating possible P was limiting relative to N in some streams. TSS during baseflow conditions ranged from 0.27-31.80 mg L-1. Autotrophic and heterotrophic comparisons of our study sites and reference sites classified our study streams as oligo-, meso-, and eu-autotrophic (N= 1, 4, and 1, respectively) and oligo-, meso-, and eu-heterotrophic (N= 4, 1, and 1, respectively). This study suggests that good water quality and moderate heterotrophic condition, with greater GPP resulting from an open canopy, are common conditions of tallgrass prairie streams. We also investigated interactions between land use/land cover, discharge rate, hydrologic alteration, and in-stream total suspended solids concentration in 23 Kansas- Missouri streams. Most streams had break points in the TSS loading rates at discharge rates exceeded <25% of days. Our estimates showed that 88% of the total annual TSS load occurred during the 11% of days with the greatest discharge rates. Buffered streams with greater percentages of grass and/or forest riparian areas had lower breakpoint values (indicating greater discharge rates were required to transport solid particles) and lower regression intercepts, which correlated to lesser TSS concentrations relative to unbuffered streams during high discharge days. In addition, grass buffered streams had smaller flood peaks and slower rise rates and forest buffered streams had less frequent floods, which lead to less total TSS transport.
Keywords: ecosystem; metabolism; nutrients; solids; stream

Exposure of nonbreeding migratory shorebirds to cholinesterase inhibiting contaminants in the Western Hemisphere - Strum, K.M.; Hooper, M.J.; Johnson, K.A.; Lanctot, R.B.; Zaccagnini, M.E.; Sandercock, B.K. (The Condor, 2010)
Migratory shorebirds frequently forage and roost in agricultural habitats, where they may be exposed to cholinesterase-inhibiting pesticides. Exposure to organophosphorus and carbamate compounds, common anti-cholinesterases, can cause sublethal effects, even death. To evaluate exposure of migratory shorebirds to organophosphorus and carbamates, we sampled birds stopping over during migration in North America and wintering in South America. We compared plasma Cholinesterase activities and body masses of individuals captured at sites with no known sources of organophosphorus or carbamates to those captured in agricultural areas where agrochemicals were recommended for control of crop pests. In South America, plasma acetylcholinesterase and butyrylcholinesterase activity in Buff-breasted Sandpipers was lower at agricultural sites than at reference sites, indicating exposure to organophosphorus and carbamates. Results of plasma Cholinesterase reactivation assays and foot-wash analyses were inconclusive. A meta-analysis of six species revealed no widespread effect of agricultural chemicals on Cholinesterase activity. However, four of six species were negative for acetylcholinesterase and one of six for butyrylcholinesterase, indicating negative effects of pesticides on Cholinesterase activity in a subset of shorebirds. Exposure to Cholinesterase inhibitors can decrease body mass, but comparisons between treatments and hemispheres suggest that agrochemicals did not affect migratory shorebirds' body mass. Our study, one of the first to estimate of shorebirds' exposure to cholinesterase-inhibiting pesticides, suggests that shorebirds are being exposed to cholinesterase-inhibiting pesticides at specific sites in the winter range but not at migratory stopover sites. Future research should examine potential behavioral effects of exposure and identify other potential sites and levels of exposure.
Keywords: Buff-breasted Sandpiper; carbamate; nonbreeding; organophosphate; population declines; sandpiper; Tryngites subruficollis; waders

Factors affecting denitrification in headwater prairie streams - Reisinger, A.J. (Kansas State University, 2010)
Human-induced stressors such as increased nitrogen (N) loadings, altered watershed land-use, and biodiversity losses are a few of the numerous threats to aquatic systems. Prairie streams experience natural disturbances, such as flooding and desiccation, which may alter responses to anthropogenic stressors. Denitrification, the dissimilatory reduction of NO3- to N gas (N2O or N2), is the only permanent form of N removal from terrestrial or aquatic ecosystems, and is important in mitigating N pollution to streams and downstream waters. Little is known about the relationships between denitrification and riparian prairie vegetation or large consumers. In the first chapter, I used outdoor mesocosms to determine the impact of a grazing minnow, Campostoma anomalum, on structural and functional responses of prairie streams to a simulated flood, focusing on denitrification. In terrestrial ecosystems, grazing can stimulate denitrification, but this has not been studied in streams. Ammonium (NH4+) enrichments, used to simulate fish excretion, alleviated N limitations on denitrification. Both fish and NH4+ affected algal biomass accrual, but only fish affected algal filament lengths and particulate organic matter. In a second experiment, I examined the impact of woody vegetation expansion, a primary threat to tallgrass prairie, on riparian and benthic denitrification. Expansion of woody vegetation in these grasslands is due primarily to altered fire regimes, which historically inhibited woody vegetation growth. To determine the effect of woody vegetation expansion on benthic and riparian denitrification, woody vegetation was removed from the riparian zone of a grazed and an ungrazed watershed. Both soil and benthic denitrification rates from this removal buffer were compared to rates in grassy or woody riparian zones. Riparian soil denitrification was highly seasonal, with greatest rates occurring during early spring, and rates being low throughout the remainder of the year. Benthic denitrification was also temporally variable but did not exhibit seasonal trends, suggesting benthic denitrification is driven by factors other than water temperature. Removal of woody vegetation stimulated soil and benthic denitrification rates over rates found in naturally vegetated riparian zones. Elevated N loadings will continue to affect aquatic ecosystems, and these effects may be exacerbated by biodiversity losses or changing riparian vegetation.
Keywords: Biodiversity; denitrification; Ecosystem recovery; nitrogen; prairie streams; woody encroachment

Fire and grazing impacts on silica production and storage in grass dominated ecosystems - Melzer, S.E.; Alan K. Knapp; Fynn, R.W.S.; Kirkman, K.P.; M.D. Smith; John M. Blair; Kelly, E.F. (Biogeochemistry, 2010)
Grassland ecosystems are an important terrestrial component of the global biogeochemical silicon cycle. Although the structure and ecological functioning of grasslands are strongly influenced by fire and grazing, the role of these key ecological drivers in the production and storage of silicon represents a significant knowledge gap, particularly since they are being altered worldwide by human activities. We evaluated the effects of fire and grazing on the range and variability of plant derived biogenic silica stored in plant biomass and soils by sampling plants and soils from long-term experimental plots with known fire and grazing histories. Overall, plants and soils from grazed sites in the South African ecosystems had up to 76 and 54% greater biogenic silica totals (kg ha−1), respectively, than grazed North American sites. In North American soils, the combination of grazing and annual fire resulted in the greatest abundance of biogenic silica, whereas South African soils had the highest biogenic silica content where grazed regardless of burn frequency. These results as well as those that show greater Si concentrations in grazed South African plants indicate that South African plants and soils responded somewhat differently to fire and grazing with respect to silicon cycling, which may be linked to differences in the evolutionary history and in the grazer diversity and grazing intensity of these ecosystems. We conclude that although fire and grazing (as interactive and/or independent factors) do not affect the concentration of Si taken up by plants, they do promote increased silicon storage in aboveground biomass and soil as a result of directly affecting other site factors such as aboveground net primary productivity. Therefore, as management practices, fire and grazing have important implications for assessing global change impacts on the terrestrial biogeochemical cycling of silicon.
Keywords: Biogenic silica; North American grasslands; Soil South African savannas; Terrestrial plants

Fire and grazing in a mesic tallgrass prairie: impacts on plant species and functional traits - Spasojevic, M.J.; Aicher, R.J.; Koch, G.R.; Marquardt, E.S.; Mirotchnick, N.; Troxler, T.G.; Scott. L. Collins (Ecology, 2010)
Fire is a globally distributed disturbance that impacts terrestrial ecosystems and has been proposed to be a global “herbivore.” Fire, like herbivory, is a top-down driver that converts organic materials into inorganic products, alters community structure, and acts as an evolutionary agent. Though grazing and fire may have some comparable effects in grasslands, they do not have similar impacts on species composition and community structure. However, the concept of fire as a global herbivore implies that fire and herbivory may have similar effects on plant functional traits. Using 22 years of data from a mesic, native tallgrass prairie with a long evolutionary history of fire and grazing, we tested if trait composition between grazed and burned grassland communities would converge, and if the degree of convergence depended on fire frequency. Additionally, we tested if eliminating fire from frequently burned grasslands would result in a state similar to unburned grasslands, and if adding fire into a previously unburned grassland would cause composition to become more similar to that of frequently burned grasslands. We found that grazing and burning once every four years showed the most convergence in traits, suggesting that these communities operate under similar deterministic assembly rules and that fire and herbivory are similar disturbances to grasslands at the trait-group level of organization. Three years after reversal of the fire treatment we found that fire reversal had different effects depending on treatment. The formerly unburned community that was then burned annually became more similar to the annually burned community in trait composition suggesting that function may be rapidly restored if fire is reintroduced. Conversely, after fire was removed from the annually burned community trait composition developed along a unique trajectory indicating hysteresis, or a time lag for structure and function to return following a change in this disturbance regime. We conclude that functional traits and species-based metrics should be considered when determining and evaluating goals for fire management in mesic grassland ecosystems.

Grasshoppers (Orthoptera: Acrididae) select vegetation patches in local-scale responses to foliar nitrogen but not phosphorus in native grassland - Loaiza, V.; Jonas, J.L.; Anthony Joern (Insect Science, 2010)
Key elements such as nitrogen (N) and phosphorus (P) are often limiting relative to the nutritional needs of herbivores that feed on them. While N often limits insect herbivores in natural terrestrial ecosystems, the effect of P is poorly studied in the field, even though compelling hypotheses from the ecological stoichiometry literature predict its importance. We evaluated small-scale spatial distributions of, and herbivory by, grasshoppers among neighboring plots that vary in foliar-N and -P in tallgrass prairie. Grasshopper densities were 67% greater in N-fertilized plots but detected no effect to grasshopper densities from P-fertilizer. Leaf damage to the dominant grass Andropogon gerardii was 32% greater in N-fertilized plots, but no response to foliar-P was detected. Herbivore damage to a common forb, goldenrod (Solidago missouriensis), was not strongly linked by fertilizer treatments, although there was increased leaf damage in N-fertilizer treatments when no P was applied (a significant N × P interaction). Under field conditions at local scales, we conclude that spatially heterogeneous distributions of grasshoppers are primarily affected by foliar-N in host plants with little evidence that P-levels contribute to the spatial patterns.
Keywords: Andropogon gerardii; ecological stoichiometry; insect herbivory; Konza Prairie; N-P fertilization experiment; Solidago missouriensis

High leaf tissue density grassland species consistently more abundant across topographic and disturbance contrasts in a North American tallgrass prairie - Craine, J.M.; Towne, E.G. (Plant and Soil, 2010)
Understanding the coupling between plant functional traits and abundance provides insight into the often hidden forces that structure plant communities. To better understand the coupling between leaf traits and abundance of grassland species in a mesic North American grassland, we measured specific leaf area (SLA) and its two components, tissue density and thickness for 125 grassland species. Plants with high tissue density were more abundant over a 17-year period across a range of environments: uplands, grazed and ungrazed watersheds, and frequently and infrequently burned watersheds. The consistent relationships between leaf tissue density and abundance across ecological contrasts imply that belowground resource availability constrains community composition independent of grazing and burning regimes. Leaf tissue density did not explain species abundance in lowlands, where belowground resources are the highest. Neither did it explain the differential abundance of species between grazing or fire frequency contrasts, suggesting that changes in burning or grazing select for species based on other traits. Relative to leaf tissue density, SLA was a poor predictor of abundance, reinforcing a long-observed—but often ignored—call that measurements of SLA need to be coupled with thickness measurements in order to effectively predict the performance of species. More generally, future research needs to investigate which belowground resources control community composition in the grassland and whether the importance of water or nutrients change with burning and grazing.
Keywords: burning; Functional traits; Grasslands; Grazing; Konza Prairie; topography

The impact of land cover change on water and carbon cycling in the US central plains grasslands - Buck, T. (University of Kansas, 2010)

Influence of landscape context on patterns of occupancy, abundance, and gene flow among collared lizards in the Flint Hills of Kansas - Blevins, E. (Kansas State University, 2010)
Organisms exist within complex landscapes, and landscape features may influence multiple aspects of a species’ distribution within the landscape, including patch occupancy, abundance within patches, and population genetic diversity at a local or regional scale. We took two approaches to identify the relative importance of landscape context for populations of the Eastern Collared Lizard (Crotaphytus collaris collaris) in the northern Flint Hills of Kansas. First, we conducted surveys at limestone outcrops in experimental watersheds managed under different burning and grazing practices. Habitat occupancy and lizard abundance were estimated by constructing models that incorporated aspects of the environment at multiple scales. Both abundance and occupancy were higher on rock ledges that had more crevices, greater complexity in vegetation, covered a larger area, and were more prominent than available habitat. Abundance and occupancy were also higher in watersheds that were burned frequently (1–2 year intervals), but grazing only had a significant effect in less frequently burned (four–year burn interval) watersheds. Our second approach was to measure genetic diversity and population genetic differentiation and relate these measures to differences in landscape context. We sampled collared lizard DNA at four locations (sample sites < 45 km apart) and analyzed trends in 10 polymorphic microsatellite loci. We found evidence for low genetic variability and moderate population differentiation among our sample sites relative to estimates reported in the literature at the core of the species’ range. Differences in migration rates and ancestry among sampling locations also appear to correspond to differences in landscape resistance based on land cover and rock availability. Thus, it appears that habitat management may influence the suitability of habitat patches at the local scale, and that differences in land cover and rock availability may influence the connectivity of populations at the landscape scale.
Keywords: Crotaphytus collaris; landscape context

Inter-regional comparison of land-use effects on stream metabolism - Bernot, M.J.; Sobota, D.J.; Hall, R.O.; Mulholland, P.J.; W. K. Dodds; Webster, J.R.; Tank, J.L.; L.R. Ashkenas; Cooper, L.W.; Dahm, C.N.; Gregory, S.V.; Grimm, N.B.; et al. (Freshwater Biology, 2010)
1. Rates of whole-system metabolism (production and respiration) are fundamental indicators of ecosystem structure and function. Although first-order, proximal controls are well understood, assessments of the interactions between proximal controls and distal controls, such as land use and geographic region, are lacking. Thus, the influence of land use on stream metabolism across geographic regions is unknown. Further, there is limited understanding of how land use may alter variability in ecosystem metabolism across regions. 2. Stream metabolism was measured in nine streams in each of eight regions (n = 72) across the United States and Puerto Rico. In each region, three streams were selected from a range of three land uses: agriculturally influenced, urban-influenced, and reference streams. Stream metabolism was estimated from diel changes in dissolved oxygen concentrations in each stream reach with correction for reaeration and groundwater input. 3. Gross primary production (GPP) was highest in regions with little riparian vegetation (sagebrush steppe in Wyoming, desert shrub in Arizona/New Mexico) and lowest in forested regions (North Carolina, Oregon). In contrast, ecosystem respiration (ER) varied both within and among regions. Reference streams had significantly lower rates of GPP than urban or agriculturally influenced streams. 4. GPP was positively correlated with photosynthetically active radiation and autotrophic biomass. Multiple regression models compared using Akaike’s information criterion (AIC) indicated GPP increased with water column ammonium and the fraction of the catchment in urban and reference land-use categories. Multiple regression models also identified velocity, temperature, nitrate, ammonium, dissolved organic carbon, GPP, coarse benthic organic matter, fine benthic organic matter and the fraction of all land-use categories in the catchment as regulators of ER. 5. Structural equation modelling indicated significant distal as well as proximal control pathways including a direct effect of land-use on GPP as well as SRP, DIN, and PAR effects on GPP; GPP effects on autotrophic biomass, organic matter, and ER; and organic matter effects on ER. 6. Overall, consideration of the data separated by land-use categories showed reduced inter-regional variability in rates of metabolism, indicating that the influence of agricultural and urban land use can obscure regional differences in stream metabolism.

Into Africa: Promoting international ecological research and training in the developing world - D.C. Hartnett (Bulletin of the Ecological Society of America, 2010)

Isolation and morphological and metabolic characterization of common endophytes in annually burned tallgrass prairie - Mandyam, K.G.; Loughlin, T.; A. Jumpponen (Mycologia, 2010)
Dark septate endophytes (DSE) are common and abundant root-colonizing fungi in the native tallgrass prairie. To characterize DSE fungi were isolated from roots of mixed tallgrass prairie plant communities. Isolates were grouped according to morphology, and the grouping was refined by ITS-RFLP and/or sequencing of the ITS region. Sporulating species of Periconia, Fusarium, Microdochium and Aspergillus were isolated along with many sterile fungi. Leek resynthesis was used to quickly screen for DSE fungi among the isolates. Periconia macrospinosa and Microdochium sp. formed typical DSE structures in the roots; Periconia produced melanized intracellular microsclerotia in host root cortex, whereas Microdochium produced abundant melanized inter- and intracellular chlamydospores. To further validate the results of the leek resynthesis growth responses of leek and a dominant prairie grass, Andropogon gerardii, were assessed in a laboratory resynthesis system. Leek growth mainly was unresponsive to the inoculation with Periconia or Microdochium, whereas Andropogon tended to respond positively. Select Periconia and Microdochium isolates were tested further for their enzymatic capabilities and for ability to use organic and inorganic nitrogen sources. These fungi tested positive for amylase, cellulase, polyphenol oxidases and gelatinase. Periconia isolates used both organic and inorganic nitrogen sources. Our study identified distinct endophytes in a tallgrass prairie ecosystem and indicated that these endophytes can use a variety of complex nutrient sources, suggesting facultative biotrophic and saprotrophic habits.
Keywords: Dark septate endophytes (DSE); enzymes; Microdochium; Periconia macrospinosa; sterile fungi

Learning capabilities enhanced in harsh environments: a common garden approach - Roth, T.C.; LaDage, L.D.; Pravosudov, V.V. (Proceedings of the Royal Society Biological Sciences, 2010)
Previous studies have suggested that the ability to inhabit harsh environments may be linked to advanced learning traits. However, it is not clear if individuals express such traits as a consequence of experiencing challenging environments or if these traits are inherited. To assess the influence of differential selection pressures on variation in aspects of cognition, we used a common garden approach to examine the response to novelty and problem-solving abilities of two populations of black-capped chickadees (Poecile atricapillus). These populations originated from the latitudinal extremes of the species's range, where we had previously demonstrated significant differences in memory and brain morphology in a multi-population study. We found that birds from the harsh northern population, where selection for cognitive abilities is expected to be high, significantly outperformed conspecifics from the mild southern population. Our results imply differences in cognitive abilities that may be inherited, as individuals from both populations were raised in and had experienced identical environmental conditions from 10 days of age. Although our data suggest an effect independent of experience, we cannot rule out maternal effects or experiences within the nest prior to day 10 with our design. Nevertheless, our results support the idea that environmental severity may be an important factor in shaping certain aspects of cognition.
Keywords: behaviour; cognition; evolution

The least weasel on Konza Prairie Biological Station, Kansas - D.W. Kaufman; Kaufman, G.A. (Transactions of the Kansas Academy of Science, 2010)

Linking snake habitat use to nest predation risk in grassland birds: the dangers of shrub cover - Klug, P.E.; Jackrel, S.L.; With, K.A. (Oecologia, 2010)
Extremes in rangeland management, varying from too-frequent fire and intensive grazing to the suppression of both, threaten rangeland ecosystems worldwide. Intensive fire and grazing denude and homogenize vegetation whereas their suppression increases woody cover. Although habitat loss is implicated in grassland bird declines, degradation through intensive management or neglect also decreases breeding habitat and may reduce nesting success through increased rates of nest predation. Snakes are important nest predators, but little is known about how habitat use in snakes relates to predation risk for grassland birds nesting within tallgrass prairie subjected to different grazing and fire frequencies. We evaluated nest survival in the context of habitat used by nesting songbirds and two bird-eating snakes, the eastern yellowbelly racer Coluber constrictor flaviventris and Great Plains ratsnake Pantherophis emoryi. Daily nest survival rates decreased with increasing shrub cover and decreasing vegetation height, which characterize grasslands that have been neglected or intensively managed, respectively. Discriminant function analysis revealed that snake habitats were characterized by higher shrub cover, whereas successful nests were more likely to occur in areas with tall grass and forbs but reduced shrub cover. Because snakes often use shrub habitat, birds nesting in areas with increased shrub cover may be at higher risk of nest predation by snakes in addition to other predators known to use shrub habitat (e.g., mid-sized carnivores and avian predators). Depredated nests also occurred outside the discriminant space of the snakes, indicating that other predators (e.g., ground squirrels Spermophilus spp. and bullsnakes Pituophis catenifer) may be important in areas with denuded cover. Targeted removal of shrubs may increase nest success by minimizing the activity of nest predators attracted to shrub cover.
Keywords: fire; Grazing; Nest success; Predator–prey relationships; tallgrass prairie

Long-term community dynamics of small landbirds with and without exposure to extensive disturbance from military training activities - Rivers, J.W.; Gipson, P.S.; Althoff, D.P.; Pontius, J.S. (Environmental Management, 2010)
Military training activities are known to impact individual species, yet our understanding of how such activities influence animal communities is limited. In this study, we used long-term data in a case study approach to examine the extent to which the local small landbird community differed between a site in northeast Kansas that experienced intensive disturbance from military training activities (Ft. Riley Military Installation) and a similar, nearby site that experienced minimal human disturbance (Konza Prairie Biological Station). In addition, we characterized how the regional pool of potential colonizers influenced local community dynamics using Breeding Bird Survey data. From 1991 to 2001, most species of small terrestrial landbirds (73%) recorded during breeding surveys were found at both sites and the mean annual richness at Ft. Riley (39.0 ± 2.86 [SD]) was very similar to that of Konza Prairie (39.4 ± 2.01). Richness was maintained at relatively constant levels despite compositional changes because colonizations compensated local extinctions at both sites. These dynamics were driven primarily by woodland species that exhibited stochastic losses and gains and were present at a low local and regional abundance. Our results suggest that military training activities may mimic natural disturbances for some species in this area because the small landbird community did not differ markedly between sites with and sites without extensive human disturbance. Although our results suggest that military training is not associated with large changes in the avian community, additional studies are needed to determine if this pattern is found in other ecological communities.
Keywords: Anthropogenic disturbance; Community dynamics; Grassland birds; Military training; Songbird conservation

Macroinvertebrate production, trophic structure, and energy flow along a tallgrass prairie stream continuum - Whiting, D.P. (Southern Illinois University, 2010)
Conceptual models of stream continua predict that energy flow and consumer functional structure change predictably with the physical attributes of a stream. To quantify these relationships in a prairie landscape, I estimated macroinvertebrate production, benthic organic matter standing stocks, and resource consumption and egestion by consumer groups along a longitudinal continuum of Kings Creek, a tallgrass prairie stream draining the Konza Prairie Biological Station in Eastern Kansas. I sampled benthic macroinvertebrates for 1 year from three stream reaches, each bordered by distinct riparian vegetation. Riparian vegetation along the continuum ranged from grassy headwaters to shrubby mid-reaches to lower reaches bordered by gallery forest. Total habitat-weighted production ranged from 31.9 g ash-free dry mass (AFDM) m-2 y-1 in the grassy headwater reach to 9.1 g AFDM m-2 y-1 in the shrubby reach to 17.0 g AFDM m-2 y-1 in the gallery forest. Functional group contributions to production generally were similar along the continuum, with collector-gatherers (40%-56% of total) and Predators (23%-38%) dominating all reaches. Quantitative food webs indicated detrital pathways dominated energy flow in all reaches, with collector-gatherers accounting for most energy flow through primary consumers. Predators were well represented and consumed 75% - 135% of total macroinvertebrate production whereas shredders (2-4%), scrapers (11-15%), and filterers (<1%) consumed a small percentage of their particular resources. High production and consumption estimates for macroinvertebrate predators suggest top-down controls are important in this system. Although functional structure was fairly similar among reaches, changes in energy flow through some groups reflected longitudinal changes in resource availability. Results indicate that this tallgrass prairie stream ecosystem is intermediate in the context of predictions of conceptual stream continua models, and biotic interactions may override some predicted responses to changes in the physical template.

Massively parallel 454-sequencing of fungal communities in Quercus spp. ectomycorrhizas indicates seasonal dynamics in urban and rural sites - A. Jumpponen; Jones, K.L.; Mattox, J.D.; Yeage, C. (Molecular Ecology, 2010)
We analysed two sites within and outside an urban development in a rural background to estimate the fungal richness, diversity and community composition in Quercus spp. ectomycorrhizas using massively parallel 454-sequencing in combination with DNA-tagging. Our analyses indicated that shallow sequencing (∼150 sequences) of a large number of samples (192 in total) provided data that allowed identification of seasonal trends within the fungal communities: putative root-associated antagonists and saprobes that were abundant early in the growing season were replaced by common ectomycorrhizal fungi in the course of the growing season. Ordination analyses identified a number of factors that were correlated with the observed communities including host species as well as soil organic matter, nutrient and heavy metal enrichment. Overall, our application of the high throughput 454 sequencing provided an expedient means for characterization of fungal communities.

The meadow jumping mouse on Konza Prairie Biological Station, Kansas - Kaufman, G.A.; D.W. Kaufman (Transactions of the Kansas Academy of Science, 2010)
We report specific locations, habitat associations and attributes of meadow jumping mice (Zapus hudsonius) captured over a 28-year period on the Konza Prairie Biological Station, Kansas. We used large 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). Fifteen meadow jumping mice were captured over the 28 years of surveys (a total of >300,000 trap nights). Nine males and six females were captured between late June and October; only a single male was scrotal and no females were visibly reproductively active. Furthermore, meadow jumping mice were from young adult-to-adult body size (13.5–21.0 g), except for a 9.5 g male trapped in mid-October. In terms of habitat association, more meadow jumping mice were captured in woodland habitats than in native prairie (standardized to trapping efforts in each habitat). No jumping mice were captured in brome fields. We conclude that overall the meadow jumping mouse is rare, but might be locally common in some years, on Konza Prairie, which lies near the southwestern edge of its current range distribution.
Keywords: abundance; limestone outcrops; planted brome fields; tallgrass prairie; woodland habitats; Zapus hudsonius

Microbial protein in soil: influence of extraction method and C amendment on extraction and recovery - Taylor, E.B.; Williams, M.A. (Microbial Ecology, 2010)
The capacity to study the content and resolve the dynamics of the proteome of diverse microbial communities would help to revolutionize the way microbiologists study the function and activity of microorganisms in soil. To better understand the limitations of a proteomic approach to studying soil microbial communities, we characterized extractable soil microbial proteins using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Two methods were utilized to extract proteins from microorganisms residing in a Quitman and Benfield soil: (1) direct extraction of bulk protein from soil and (2) separation of the microorganisms from soil using density gradient centrifugation and subsequent extraction (DGC–EXT) of microbial protein. In addition, glucose and toluene amendments to soil were used to stimulate the growth of a subset of the microbial community. A bacterial culture and bovine serum albumin (BSA) were added to the soil to qualitatively assess their recovery following extraction. Direct extraction and resolution of microbial proteins using SDS-PAGE generally resulted in smeared and unresolved banding patterns on gels. DGC–EXT of microbial protein from soil followed by separation using SDS-PAGE, however, did resolve six to 10 bands in the Benfield but not the Quitman soil. DGC–EXT of microbial protein, but not direct extraction following the addition of glucose and toluene, markedly increased the number of bands (~40) on the gels in both Benfield and Quitman soils. Low recoveries of added culture and BSA proteins using the direct extraction method suggest that proteins either bind to soil organic matter and mineral particles or that partial degradation takes place during extraction. Interestingly, DGC may have been preferentially selected for actively growing cells, as gauged by the 10–100× lower cy19:0/18:1ω7 ratio of the fatty acid methyl esters in the isolated community compared to that for the whole soil. DGC can be used to isolate soil communities and provide microbial protein that can be characterized using PAGE.

Mineralogy and morphological properties of buried polygenetic paleosols formed in late quaternary sediments on upland landscapes of the central plains, USA - Presley, D.R.; Hartley, P.E.; Ransom, M.D. (Geoderma, 2010)
East central Kansas is largely comprised of alternating, level beds of Permian shale and limestone of the Central Plains, USA. Polygenetic upland soils of east central Kansas have been formed though multiple and likely different sets of soil forming factors. Upland soils in this region have a complex genesis, often contain one or more paleosols, and form in multiple parent materials including loess, locally reworked loess or colluvium, and residuum. The depth to bedrock rarely exceeds 2 m. Upland hillslope soils commonly contain one or more paleosols, and can be observed on a variety of hillslope positions on the landscape. Generally, the lower paleosols are recognized by strongly expressed structure, thick continuous clay coatings on all faces of peds, and strong reddish color with either 7.5YR or 5YR hues. Soil textures of the paleosols often feel less clayey than the overlying horizons in field determinations. At first, this was attributed to a decrease in clay content, stickiness, and plasticity. However, subsequent laboratory characterization revealed that the clay content was usually highest in the lower paleosol horizons, and that the clay mineralogy of the modern soil was dominated by smectite, while the paleosols contained a mixed suite of minerals. Therefore, the perceived decrease in clay content was caused by a change in clay mineralogy, a feature that can be exploited in future field descriptions in order to more accurately distinguish between stratigraphic units in these thin, welded polygenetic soils. The age of the paleosols sampled in this study were typical for the late Quaternary-aged Severance formation, clustering in two age ranges, which were ≈ 19,000 to 20,000 and ≈ 22,500 to 27,700 uncalibrated 14C yr BP. The results from this study illustrate that although they might be thin, truncated, and welded, late Quaternary-aged loess-derived soils and paleosols occur in regular, predictable patterns on many upland hillslopes in the Bluestem Hills Major Land Resource Area, and this region should be included in future regional investigations of the Central Plains.
Keywords: Central Plains; Great Plains; Landscapes; Loess; Mineralogy; Paleosols; Quaternary

Morphological and physiological traits as indicators of drought tolerance in tallgrass prairie plants - Tucker, S. (Kansas State University, 2010)
The Konza Prairie in northern Kansas, USA contains over 550 vascular plant species; of which, few have been closely studied. These species are adapted to environmental stress as imposed by variable temperature, precipitation, fire, and grazing. Understanding which plant traits relate to drought responses will allow us to both predict drought tolerance and potential future shifts in plant community composition from changes in local climate. Morphological and physiological measurements were taken on 121 species of herbaceous tallgrass prairie plants grown from seed in a growth chamber. Gas exchange measurements including maximum photosynthetic rate, stomatal conductance to water vapor, and intercellular CO[subscript]2 concentration were measured. All plants were exposed to a drought treatment and were monitored daily until stomatal conductance was zero. At this point, critical leaf water potential (Ψ[subscript]crit), an indicator of physiological drought tolerance was assessed. Other measurements include root length, diameter, volume, and mass, leaf area, leaf tissue density, root tissue density, and root to shoot ratio. Traits were compared using pair-wise bivariate analysis and principal component analysis (PCA). A dichotomy was found between dry-adapted plants with thin, dense leaves and roots, high leaf angle, and highly negative Ψ[subscript]crit and hydrophiles which have the opposite profile. A second axis offers more separation based on high photosynthetic rate, high conductance rate, and leaf angle, but fails to provide a distinction between C[subscript]3 and C[subscript]4 species. When tested independently, grasses and forbs both showed drought tolerance strategies similar to the primary analysis. Matching up these axes with long term abundance data suggests that species with drought tolerance traits have increased abundance on Konza, especially in upland habitats. However, traits that relate to drought tolerance mirror relationships with nutrient stress, confounding separation of low water versus low nutrient strategies. My results not only illustrate the utility of morphological and physiological plant traits in classifying drought responses across a range of species, but as functional traits in predicting both drought tolerance in individual species and relative abundance across environmental gradients of water availability.
Keywords: Abundance; Konza; Drought Tolerance; Plant traits; tallgrass prairie

Multi-element fingerprinting and high throughput sequencing identify multiple elements that affect fungal communities in Quercus macrocarpa foliage - A. Jumpponen; Keating, K.; Gadbury, G.L.; Jones, K.L.; Mattox, J.D. (Plant Signaling and Behaviour, 2010)
Diverse fungal mutualists, pathogens and saprobes colonize plant leaves. These fungi face a complex environment, in which stochastic dispersal interplays with abiotic and biotic filters. However, identification of the specific factors that drive the community assembly seems unattainable. We mined two broad data sets and identified chemical elements, to which dominant molecular operational taxonomic units (OTUs) in the foliage of a native tree respond most extremely. While many associations could be identified, potential complicating issues emerged. Those were related to unevenly distributed OTU frequency data, a large number of potentially explanatory variables, and the disproportionate effects of outlier observations.

Nest site selection and nest thermal properties of common nighthawks on the tallgrass prairie of Kansas - Lohnes, R.G. (Cornell University, 2010)
My research uses a behavioral ecology approach to understand Common Nighthawk (Chordeiles minor) declines and to inform nest-site restoration efforts in urban and suburban landscapes. The objectives of this study were to determine if nighthawks are choosing to nest non-randomly with respect to the distribution of types of vegetation and substrates within a tallgrass prairie landscape on Konza Prairie in Kansas, and to establish the thermal properties of nest sites for biologically informed restoration efforts. These two objectives were designed to identify nest-site characteristics that could be used to design suitable nesting substrates in urban and suburban landscapes. In the summer of 2007, I investigated nest site selection. Common Nighthawks typically lay clutches of one to two eggs either directly on the ground or in a shallow scrape. Most nests that have been documented were on patches of rock, gravel, or bare ground, but I wanted to determine whether this was due to differences in detectability between open gravel patches and areas with more vegetation cover. In early May, prior to the breeding season, we identified 10 target watersheds on Konza Prairie Biological Field Station. I then surveyed 120 randomly-placed vegetation plots in those areas. The circular plots were 4 m in diameter and I recorded percent cover of 5 cover class types within each plot (forbs, grass, shrub, dead vegetation, and rock/gravel/bare ground). During the breeding season from mid-May to late July, I systematically searched for nests within the targeted watersheds. I found 27 nests in these areas. As soon as possible (zero to three days) after finding each nest, I surveyed the area directly around the location of the eggs or chicks, recording percent cover in the same manner as the vegetation plots (4m diameter circle with percent cover of 5 cover classes). Post-breeding season, in early to mid-August, I re-surveyed the same 120 vegetation plots. At the same time, I also re-sampled the vegetation at all the nest sites. When I compared the summer re-survey of the nest plots to the summer re-survey of the random vegetation plots using a Mann-Whitney "U" test, I found that the birds were selecting areas with bare ground and rock at a significantly greater frequency than they occur in the surrounding landscape. I also observed that they were avoiding shrubs. Overall, 96% of 27 nests occurred on bare ground and rock. In 2008, I used a trained dog to find nests; 100% of the nests discovered by the dog were on bare ground and rock (n=9), a percentage similar to the percent in my 2007 sample. To investigate the thermal properties of nest sites, from July 9 - July 29 of 2008, I placed iButton thermal data loggers at nests. The iButtons recorded the temperature, time, and date every five minutes. At each nest, I placed one iButton directly on the nesting substrate away from the eggs or chicks (on rock/bare ground), and I placed an additional iButton in the next nearest cover class (grass or forbs). At each nest, the iButtons were approximately .5m apart. I recorded the temperature at 6 nests for1660 hours at each. I found that within a single month, the nesting substrate can experience temperatures that range from 14.5 degree Centigrade to 60 degree Centigrade. When I compared the vegetation versus the nest site I found that the average daily temperature and the high daily temperatures were significantly cooler in the vegetation during the day. Based on behavioral observations, these cooler areas serve as refuges for the young nighthawks during the day. Based on these observations of nest-site characteristics I recommend that natural areas be managed to increase rock and gravel patches and that urban restoration efforts test patches that maximize the amount of shade available during the day.

Net carbon fluxes over burned and unburned native tallgrass prairie - D. Bremer; J.M. Ham (Rangeland Ecology & Management, 2010)
Prescribed burning of aboveground biomass in tallgrass prairie is common and may influence dynamics and magnitudes of carbon (C) movement between the surface and atmosphere. Carbon dioxide (CO2) fluxes were measured for 2 yr using conditional sampling systems on two adjacent watersheds in an ungrazed tallgrass prairie near Manhattan, Kansas. One watershed was burned annually (BA) and the other biennially (BB). Leaf and soil CO2 fluxes were measured in the source area. Net ecosystem exchange (NEE) of CO2 reached a maximum daily gain of 26.4 g CO2 · m−2 · d−1 (flux toward surface is positive) in July 1998 (year when both sites were burned and precipitation was above normal); gains were similar between sites in 1998. The maximum daily NEE loss of CO2 was −21.8 g CO2 · m−2 · d−1 from BA in September 1997 (year when only BA was burned and precipitation was below normal). When data were integrated over the two years, both sites were net sources of atmospheric CO2; NEE was −389 g C · m−2 · 2 yr−1 on BA and −195 g C · m−2 · 2 yr−1 on BB. Burning increased canopy size and photosynthesis, but the greater photosynthesis was offset by corresponding increases in respiration (from canopy and soil). Carbon losses from fire represented 6–10% of annual CO2 emissions (bulk came from soil and canopy respiration). Data suggest that annual burning promotes C loss compared to less-frequently burned tallgrass prairie where prairie is not grazed by ungulates. Greater precipitation in 1998 caused large increases in biomass and a more positive growing season NEE, indicating that C sequestration appears more likely when precipitation is high. Because C inputs (photosynthesis) and losses (canopy and soil respiration) were large, small measurement or modeling errors could confound attempts to determine if the ecosystems are long-term CO2 sources or sinks.
Keywords: conditional sampling; fire; grassland; Konza Prairie; Land management; net ecosystem exchange

Permanent genetic resources added to molecular ecology resources database - Glenn R. Almany (Molecular Ecology Resources, 2010)
This article documents the addition of 512 microsatellite marker loci and nine pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Alcippe morrisonia morrisonia, Bashania fangiana, Bashania fargesii, Chaetodon vagabundus, Colletes floralis, Coluber constrictor flaviventris, Coptotermes gestroi, Crotophaga major, Cyprinella lutrensis, Danaus plexippus, Fagus grandifolia, Falco tinnunculus, Fletcherimyia fletcheri, Hydrilla verticillata, Laterallus jamaicensis coturniculus, Leavenworthia alabamica, Marmosops incanus, Miichthys miiuy, Nasua nasua, Noturus exilis, Odontesthes bonariensis, Quadrula fragosa, Pinctada maxima, Pseudaletia separata, Pseudoperonospora cubensis, Podocarpus elatus, Portunus trituberculatus, Rhagoletis cerasi, Rhinella schneideri, Sarracenia alata, Skeletonema marinoi, Sminthurus viridis, Syngnathus abaster, Uroteuthis (Photololigo) chinensis, Verticillium dahliae, Wasmannia auropunctata, and Zygochlamys patagonica. These loci were cross‐tested on the following species: Chaetodon baronessa, Falco columbarius, Falco eleonorae, Falco naumanni, Falco peregrinus, Falco subbuteo, Didelphis aurita, Gracilinanus microtarsus, Marmosops paulensis, Monodelphis Americana, Odontesthes hatcheri, Podocarpus grayi, Podocarpus lawrencei, Podocarpus smithii, Portunus pelagicus, Syngnathus acus, Syngnathus typhle,Uroteuthis (Photololigo) edulis, Uroteuthis (Photololigo) duvauceli and Verticillium albo‐atrum. This article also documents the addition of nine sequencing primer pairs and sixteen allele specific primers or probes for Oncorhynchus mykiss and Oncorhynchus tshawytscha; these primers and assays were cross‐tested in both species.

Phosphorus biogeochemistry across a precipitation gradient in grasslands of central North America - Ippolito, J.A.; Blecker, S.W.; Freeman, C.L.; McCulley, R.L.; John M. Blair; Kelly, E.F. (Journal of Arid Environments, 2010)
Soil P transformations and distribution studies under water limited conditions that characterize many grasslands may provide further insight into the importance of abiotic and biotic P controls within grass-dominated ecosystems. We assessed transformations between P pools across four sites spanning the shortgrass steppe, mixed grass prairie, and tallgrass prairie along a 400-mm precipitation gradient across the central Great Plains. Pedon total elemental and constituent mass balance analyses reflected a pattern of increased chemical weathering from the more arid shortgrass steppe to the more mesic tallgrass prairie. Soil surface A horizon P accumulation was likely related to increased biocycling and biological mining. Soluble P, a small fraction of total P in surface A horizons, was greatest at the mixed grass sites. The distribution of secondary soil P fractions across the gradient suggested decreasing Ca-bound P and increasing amounts of occluded P with increasing precipitation. Surface A horizons contained evidence of Ca-bound P in the absence of CaCO3, while in subsurface horizons the Ca-bound P was associated with increasing CaCO3 content. Calcium-bound P, which dominates in water-limited systems, forms under different sets of soil chemical conditions in different climatic regimes, demonstrating the importance of carbonate regulation of P in semi-arid ecosystems.
Keywords: Grassland ecosystems; Phosphorus biogeochemistry; Sequential phosphorus extraction; Soil weathering

Plant nitrogen and phosphorus limitation in 98 North American grassland soils - Craine, J.M.; Jackson, R.D. (Plant and Soil, 2010)
The availability of nutrients is a critical determinant of ecological dynamics in grasslands, but the relationships between soil resource availability and nutrient limitation across ecosystems are not clear. To better understand how soil nutrient availability determines nutrient limitation in vegetation, we grew the same species of grass (Schizachyrium scoparium) in 98 North American grassland soils and fertilized them factorially with nitrogen (N) and phosphorus (P). On average adding N, P, and the two nutrients together increased biomass relative to unfertilized plants by 81%, 22%, and 131%, respectively. Plants grown on low-P soils were not primarily limited by P. Instead, these plants were colimited by N and P, while plants grown on high-P soils were primarily limited by N and only secondarily limited by P. Limitation was not predicted by total soil N. The preponderance of colimitation between N and P on low-P soils suggests that low P availability alters the N cycle to constrain supplies to plants such that N and P are made available in proportion to their demand by plants.
Keywords: Colimitation; Grasslands; nitrogen; Phosphorus; stoichiometry

Quantifying phenotypic variation between populations of Panicum virgatum along a latitudinal gradient within the Great Plains - Orozco, R.A. (St. Joseph's University, 2010)

Relatedness of Macrophomina phaseolina isolates from tallgrass prairie, maize, soybean, and sorghum - Saleh, A.A.; Ahmed, H.U.; Todd, T.C.; Travers, S.E.; Zeller, K.A.; Leslie, J.F.; Garrett, K.A. (Molecular Ecology, 2010)
Agricultural and wild ecosystems may interact through shared pathogens such as Macrophomina phaseolina, a generalist clonal fungus with more than 284 plant hosts that is likely to become more important under climate change scenarios of increased heat and drought stress. To evaluate the degree of subdivision in populations of M. phaseolina in Kansas agriculture and wildlands, we compared 143 isolates from maize fields adjacent to tallgrass prairie, nearby sorghum fields, widely dispersed soybean fields and isolates from eight plant species in tallgrass prairie. Isolate growth phenotypes were evaluated on a medium containing chlorate. Genetic characteristics were analysed based on amplified fragment length polymorphisms and the sequence of the rDNA-internal transcribed spacer (ITS) region. The average genetic similarity was 58% among isolates in the tallgrass prairie, 71% in the maize fields, 75% in the sorghum fields and 80% in the dispersed soybean fields. The isolates were divided into four clusters: one containing most of the isolates from maize and soybean, two others containing isolates from wild plants and sorghum, and a fourth containing a single isolate recovered from Solidago canadensis in the tallgrass prairie. Most of the sorghum isolates had the dense phenotype on media containing chlorate, while those from other hosts had either feathery or restricted phenotypes. These results suggest that the tallgrass prairie supports a more diverse population of M. phaseolina per area than do any of the crop species. Subpopulations show incomplete specialization by host. These results also suggest that inoculum produced in agriculture may influence tallgrass prairie communities, and conversely that different pathogen subpopulations in tallgrass prairie can interact there to generate ‘hybrids’ with novel genetic profiles and pathogenic capabilities.

Resource limitation is a driver of local adaptation in mycorrhizal symbioses - Johnson, N.C.; G.T. Wilson; M. Bowker; Wilson, J.A.; Miller, R.M. (Proceedings of the National Academy of Sciences of the United States of America, 2010)
Symbioses may be important mechanisms of plant adaptation to their environment. We conducted a reciprocal inoculation experiment to test the hypothesis that soil fertility is a key driver of local adaptation in arbuscular mycorrhizal (AM) symbioses. Ecotypes of Andropogon gerardii from phosphorus-limited and nitrogen-limited grasslands were grown with all possible “home and away” combinations of soils and AM fungal communities. Our results indicate that Andropogon ecotypes adapt to their local soil and indigenous AM fungal communities such that mycorrhizal exchange of the most limiting resource is maximized. Grasses grown in home soil and inoculated with home AM fungi produced more arbuscules (symbiotic exchange structures) in their roots than those grown in away combinations. Also, regardless of the host ecotype, AM fungi produced more extraradical hyphae in their home soil, and locally adapted AM fungi were, therefore, able to sequester more carbon compared with nonlocal fungi. Locally adapted mycorrhizal associations were more mutualistic in the two phosphorus-limited sites and less parasitic at the nitrogen-limited site compared with novel combinations of plants, fungi, and soils. To our knowledge, these findings provide the strongest evidence to date that resource availability generates evolved geographic structure in symbioses among plants and soil organisms. Thus, edaphic origin of AM fungi should be considered when managing for their benefits in agriculture, ecosystem restoration, and soil-carbon sequestration.
Keywords: coevolution; geographic mosaics; mutualism; parasitism

Retrospective analysis of fish community change during a half-century of landuse and streamflow changes - K. B. Gido; W. K. Dodds; Eberle, M.E. (Journal of the North American Benthological Society, 2010)
Ecological thresholds that lead to alternative community states can be exceeded through gradual perturbation or as a result of sudden disturbance. Many Great Plains streams have experienced dramatic changes in their hydrologic regime resulting from water and landuse changes that began as early as 1880. These changes, combined with the presence of many invasive species, have substantially altered the fish communities in this area. We quantified temporal changes in fish communities in 3 large river basins in relation to putative anthropogenic stressors, including increased sediment supply derived from row-crop agriculture (beginning in 1880), habitat fragmentation caused by reservoir construction (beginning in the 1950s), and reduced discharge caused by groundwater withdrawal (beginning in the 1960s). We hypothesized that these abiotic regime shifts, coupled with species invasions, would shift the system from a fish community dominated by lotic (flowing water) species to one dominated by lentic (still water) species. Further, we predicted that the timing and intensity of community change would vary across basins that experienced different types and levels of stressors. Restructuring of fish communities across the 3 river basins was driven primarily by similar increases in lentic species, with only a few declines in several large-river species. Current fish communities in these basins share <50% of the species recorded in historic collections, and these differences were driven by species extirpations and invasions. The greatest levels of community divergence over time occurred in western Kansas basins that experienced the most intense groundwater withdrawals and fragmentation by reservoirs. An alarming result from this analysis was the recent (after 1991) expansion of several invasive species in the Arkansas and lower Kansas River basins and the decline or extirpation of several native species where flow regimes are less heavily altered. Accelerating changes in the biota and habitat identified by our retrospective analysis highlight potential complications for restoring the habitat and native fish communities to a previous state.
Keywords: biotic homogenization; Hydrology; Invasive species; presence–absence data; retrospective analysis; streamflow modification

Road crossing designs and their impact on fish assemblages of Great Plains streams - Bouska, W.W.; Paukert, C.P. (Transactions of the American Fisheries Society, 2010)
A mark–recapture field study was conducted to determine fish passage at 5 concrete box culverts and 5 low-water crossings (concrete slabs vented by culverts) as well as 10 control sites (below a natural riffle) in Flint Hills streams of northeastern Kansas. Additionally, we tested the upstream passage of four fish species native to Great Plains streams (Topeka shiner Notropis topeka, green sunfish Lepomis cyanellus, red shiner Cyprinella lutrensis, and southern redbelly dace Phoxinus erythrogaster) through three simulated crossing designs (box culverts, round corrugated culverts, and natural rock riffles) at water velocities of 0.1 to 1.1 m/s in an experimental stream. The field study indicated that cyprinids were twice as likely to move upstream of box culverts than low-water crossings and 1.4 times as likely to move upstream of control reaches than any crossing type. The best models indicated that the proportion of cyprinids that moved upstream increased with decreased culvert slope and length, perching, and increased culvert width. Our controlled experiment indicated that fish can move through velocities up to 1.1 m/s in a 1.86-m simulated stream and that the proportion of fish that moved upstream did not differ among crossing designs for southern redbelly dace, green sunfish, or Topeka shiner; however, natural rock riffles had lower proportional movements (mean = 0.19) than the box (0.38) or corrugated culvert designs (0.43) for red shiners. Water velocity did not affect the proportional upstream movement of any species except that of Topeka shiners, which increased with water velocity. Crossing design alone may not determine fish passage, and water velocities up to 1.1 m/s may not affect the passage of many Great Plains fishes. Barriers to fish movement may be the result of other factors (e.g., perching, slope, and crossing length). The use of properly designed and installed crossings has promise in conserving Great Plains stream fishes.

Saturation of NO3- uptake in prairie streams as a function of acute and chronic N exposure - O'Brien, J.M.; W. K. Dodds (Journal of the North American Benthological Society, 2010)
We conducted a series of stepwise NO3− additions to investigate the response of NO3− uptake to short-term (acute) changes in N concentration in 3 prairie streams. Observed NO3− uptake rates increased with short-term elevations in NO3− concentration and were consistent with linear and Michaelis–Menten kinetics models. We compiled these data with uptake rates from additional published studies to calculate robust estimates of N uptake kinetics for prairie streams. Half-saturation coefficients based on compiled data were 6.7 µg/L for NH4+ and 67 µg/L for NO3−-N. This difference in half-saturation coefficients suggests that NH4+ is more efficiently assimilated than NO3−, indicating a preference for NH4+ as an N source. Similarly, ambient concentrations of NH4+ and NO3− were less than their respective half-saturation coefficients, and aerial uptake rates were generally <5% of the maximum, suggesting severe limitation of N uptake at ambient conditions. The observed pattern of uptake kinetics suggests that physiological constraints limit biotic N uptake in these low-N streams and contrasts with the pattern of uptake observed in streams with chronically elevated ambient NO3− concentrations.
Keywords: Biogeochemistry; Kings Creek; Konza Prairie; nitrate uptake

Seasonally dynamic fungal communities in Quercus macrocarpa phyllosphere differ among urban and nonurban environments - A. Jumpponen; Jones, K.L. (New Phytologist, 2010)
•The fungal richness, diversity and community composition in the Quercus macrocarpa phyllosphere were compared across a growing season in trees located in six stands within and outside a small urban center using 454-sequencing and DNA tagging. The approaches did not differentiate between endophytic and epiphytic fungal communities. •Fungi accumulated in the phyllosphere rapidly and communities were temporally dynamic, with more than a third of the analyzed operational taxonomic units (OTUs) and half of the BLAST-inferred genera showing distinct seasonal patterns. The seasonal patterns could be explained by fungal life cycles or environmental tolerances. •The communities were hyperdiverse and differed between the urban and nonurban stands, albeit not consistently across the growing season. Foliar macronutrients (nitrogen (N), potassium (K) and sulfur (S)), micronutrients (boron (B), manganese (Mn) and selenium (Se)) and trace elements (cadmium (Cd), lead (Pb) and zinc (Zn)) were enriched in the urban trees, probably as a result of anthropogenic activities. Because of correlations with the experimental layout, these chemical elements should not be considered as community drivers without further empirical studies. •We suggest that a combination of mechanisms leads to differences between urban and nonurban communities. Among those are stand isolation and size, nutrient and pollutant accumulation plus stand management, including fertilization and litter removal.

Shifting fungal endophyte communities colonize Bouteloua gracilis: effect of host tissue and geographical distribution - Herrera, J.; Khidir, H.H.; Eudy, D.M.; Porras-Alfaro, A.; Natvig, D.O.; Sinsabaugh, R.L. (Mycologia, 2010)
Communities of root-associated fungi (RAF) commonly have been studied under the auspices of arbuscular mycorrhizal fungi (AMF) or ectomycorrhizal fungi. However many studies now indicate that other groups of endophytic RAF, including dark septate endophytes (DSE) are more abundant in some plants and environments. The common forage grass, Bouteloua gracilis, was used as a model to examine whether RAF also colonize different organs within the same plant and to compare RAF communities from sites across North America, spanning the latitudinal range of B. gracilis (from Canada to Mexico). We compared the RAF communities of organs within individual plants at one site and within plant roots among six sites. With the possible exception of one group related to genus Paraphaeosphaeria there was little evidence that RAF colonized vertically beyond the crowns. Furthermore, although there was some variation in the constitution of rare members of the RAF communities, several taxonomically related groups dominated the RAF community at all sites. These dominant taxa included members in the Pleosporales (related to the DSE, Paraphaeosphaeria spp.), Agaricales (related to Moniliophthora spp., or Campanella spp.) and Hypocreales (related to Fusarium spp.). AMF were notable by their near absence. Similar phylotypes from the dominant groups clustered around adjacent sites so that similarity of the RAF communities was negatively correlated to site inter-distance and the RAF communities appeared to group by country. These results increase the possibility that at least some of these common and widely distributed core members of the RAF community form important, intimate and long lasting relationships with grasses.
Keywords: Bouteloua gracilis; dark septate endophytes; endophytic fungi; grassland fungi; Grasslands National Park; Janos; Konza Prairie; Llanos de Ojuelos; Sevilleta; Wind Cave National Park

Small mammals as winter prey of long-eared owls in Kansas - D.W. Kaufman; Kaufman, G.A.; Brillhart, D. (Transactions of the Kansas Academy of Science, 2010)

Thirteen decades of foliar isotopes indicate declining nitrogen availability in central North American grasslands - McLauchlan, K.K.; Ferguson, C.J.; Wilson, I.E.; Ocheltree, T.W.; Craine, J.M. (New Phytologist, 2010)
•Humans are increasing both the deposition of reactive nitrogen (N) and concentrations of atmospheric CO2 on Earth, but the combined effects on terrestrial ecosystems are not clear. In the absence of historical records, it is difficult to know if N availability is currently increasing or decreasing on regional scales. •To determine the nature and timing of past changes in grassland ecosystem dynamics, we measured the composition of stable carbon (C) and N isotopes in leaf tissue from 545 herbarium specimens of 24 vascular plant species collected in Kansas, USA from 1876 to 2008. We also parameterized a simple model of the terrestrial N cycle coupled with a stable isotope simulator to constrain processes consistent with observed patterns. •A prolonged decline in foliar N concentrations began in 1926, while a prolonged decline in foliar δ15N values began in 1940. Changes in the difference between foliar and atmospheric C isotopes reveal slightly increased photosynthetic water use efficiency since 1876. •The declines in foliar N concentrations and foliar δ15N suggest declining N availability in these grasslands during the 20th century despite decades of anthropogenic N deposition. Our results are consistent with progressive-nitrogen-limitation-type hypotheses where declines in N availability are driven by increased ecosystem N storage as a result of increased atmospheric CO2.

Thresholds, breakpoints, and nonlinearity in freshwaters as related to management - W. K. Dodds; Clements, W.H.; K. B. Gido; Hilderbrand, R.H.; King, R.S. (Journal of the North American Benthological Society, 2010)

Variation in gene expression of Andropogon gerardii in response to altered environmental conditions associated with climate change - Travers, S.E.; Tang, Z.; Caragea, D.; Garrett, K.A.; Hulbert, S.H.; Leach, J.E.; Bai, J.; Saleh, A.; Alan K. Knapp; Fay, P.A.; Jesse B. Nippert; Schnable, P.S.; et al. (Journal of Ecology, 2010)
1. If we are to understand the mechanisms underlying species responses to climate change in natural systems, studies are needed that focus on responses of non-model species under field conditions. We measured transcriptional profiles of individuals of Andropogon gerardii, a C4 grass native to North American grasslands, in a field experiment in which both temperature and precipitation were manipulated to simulate key aspects of forecasted climate change. 2. By using microarrays developed for a closely related model species, Zea mays, we were able to compare the relative influence of warming versus altered soil moisture availability on expression levels of over 7000 genes, identify responsive functional groups of genes and correlate changes in gene transcription with physiological responses. 3. We observed more statistically significant shifts in transcription levels of genes in response to thermal stress than in response to water stress. We also identified candidate genes that demonstrated transcription levels closely associated with physiological variables, in particular chlorophyll fluorescence. 4.Synthesis. These results suggest that an ecologically important species responds differently to different environmental aspects of forecast climate change. These translational changes have the potential to influence phenotypic characters and ultimately adaptive responses.

Vertical distribution of fungal communities in tallgrass prairie soil - A. Jumpponen; Jones, K.L.; John M. Blair (Mycologia, 2010)
We used 454 sequencing of the internal transcribed spacer region to characterize fungal communities in tallgrass prairie soils subdivided into strata 0–10, 10–20, 30–40 and 50–60 cm deep. The dataset included more than 14 000 fungal sequences distributed across Basidiomycota, Ascomycota, basal fungal lineages and Glomeromycota in order of decreasing frequency. As expected the community richness and diversity estimators tended to decrease with increasing depth. Although species richness was significantly reduced for samples from the deeper profiles, even the deepest stratum sampled contained richness of more than a third of that in the topmost stratum. More importantly, nonparametric multidimensional scaling (NMS) ordination analyses indicated that the fungal communities differed across vertical profiles, although only the topmost and deepest strata were significantly different when the NMS axis scores were compared by ANOVA. These results emphasize the importance of considering the fungal communities across the vertical strata because the deeper soil horizons might maintain a distinct community composition and thus contribute greatly to overall richness. The majority of operational taxonomic units (OTUs) declined in frequency with increasing depth, although a linear regression analysis indicated that some increased with increasing depth. The OTUs and BLAST-assigned taxa that showed increasing frequencies were mainly unculturable fungi, but some showed likely affinities to families Nectriaceae and Venturiaceae or to genus Pachnocybe. Although the ecological roles of the fungi in the deeper strata remain uncertain, we hypothesize that the fungi with preferences for deeper soil have adequate access to substrates and possess environmental tolerances that enable their persistence in those environments.
Keywords: 454 sequencing; pyrosequencing; soil depth; Soil fungi; tallgrass prairie

Widespread coupling between the rate and temperature sensitivity of organic matter decay - Craine, J.M.; Fierer, N.; McLauchlan, K.K. (Nature Geoscience, 2010)
Microbial breakdown of soil organic matter influences the potential for terrestrial ecosystems to sequester carbon, and the amount of carbon dioxide released to the atmosphere1, 2, 3, 4. Predicting the sensitivity of microbial decomposition to temperature change is therefore critical to predicting future atmospheric carbon dioxide concentrations and feedbacks to anthropogenic warming5. According to enzyme kinetics, the more biogeochemically recalcitrant the organic matter, the greater the temperature sensitivity of microbial respiration6, 7, 8. Here, we measured the temperature sensitivity of microbial respiration in soils from 28 sites in North America, ranging from Alaska to Puerto Rico, to test the generality of this principle. We show that the lower the rate of respiration at a reference temperature of 20 °C—and thus the more biogeochemically recalcitrant the organic matter—the greater the temperature sensitivity of soil respiration. We compiled our findings with those from other studies, encapsulating a range of environments, and show that this relationship holds across multiple scales and soil types. Although physico-chemical protection of soil organic matter and substrate availability will also influence the temperature sensitivity of decomposition, we suggest that biogeochemically recalcitrant organic matter will respond the most sensitively to anticipated warming.
Keywords: Biogeochemistry; Microbial ecology

Analysis of rhizosphere fungal communities using rRNA and rDNA - A. Jumpponen (Symbiotic Fungi, Soil Biology, 2009)
Microbial communities in soil and rhizosphere are diverse. Use of sequence data derived from environmental samples has become somewhat of a standard to explore the microbial diversity and community composition in soils. While the DNA encoding the ribosomal RNA genes can be easily PCR-amplified from many environmental samples, this DNA may carry a historical fingerprint, as naked DNA or as dormant, but inactive organisms. The use of ribosomal RNA may provide a tool to focus on the active organisms. This chapter describes kit-based methods to simultaneously extract DNA and RNA from environmental samples, and outlines a protocol for reverse-transcribing ribosomal RNA for PCR amplification of the produced cDNA. The fungal communities observed via sequencing the ribosomal RNA or the ribosomal RNA encoding DNA from Andropogon gerardii rhizosphere are compared, and the results briefly discussed.

Annual fire and mowing alter biomass, depth distribution, and C and N content of roots and soil in tallgrass prairie - Kitchen, D.J.; John M. Blair; Callaham, M.A. (Plant and Soil, 2009)
Management practices, such as fire and mowing, can affect the distribution and quality of roots and soil C and N in grasslands. We examined long-term (13 years) effects of annual fire and mowing on fine (<2 mm) roots and soil C and N content in a native tallgrass prairie at Konza Prairie Biological Station in northeastern Kansas, USA. Using 90 cm deep soil cores, we determined that fire and mowing independently and interactively influenced the quantity and depth distribution of fine root biomass, root C and N concentration, and soil C and N content. Annual burning increased total fine root biomass by 48% and total C storage in roots by 47% compared to unburned unmowed plots, and resulted in a deeper distribution of roots. There was a significant interaction of fire and mowing, whereby mowing reduced root biomass and root C storage by ~30% in annually burned plots, but did not affect total root biomass in unburned plots. Mowing also resulted in shallower distribution of roots regardless of fire treatment. Root N concentration was reduced by 15–25% in plots that were burned, mowed, or both. Mowing effects on soil C and N were restricted to surface soils (0–10 cm), where mowing reduced soil C concentrations by ~20% and N concentrations by 17% regardless of burning treatment. In contrast, burning alone did not significantly influence soil C and N concentrations. In general, root biomass, root C and N mass, and soil C and N concentrations declined with depth, and most responses to burning and mowing exhibited significant interactions with depth. Different long-term fire and mowing regimes can significantly alter belowground root biomass and C and N dynamics in grasslands, and in particular at depths in the profile that are not typically sampled.
Keywords: fire; grassland; Mowing; Root biomass depth distribution; Soil C and N; tallgrass prairie

Approaches to predicting broad-scale regime shifts using changing pattern-process relationships across scales - Peters, D.P.C.; B.T. Bestelmeyer; Alan K. Knapp; Herrick, J.E.; Monger, H.C.; Havstad, K.M. (Real World Ecology: Design and Analyses of Large-Scale and Long-Term Research, 2009)
Understanding and predicting the occurrence of alternative ecosystem states (i.e., regime shifts) at broad scales is a pressing challenge for ecologists given the scope and nature of global change. In many cases, regime shifts at broad-scales are affected by pattern-process relationships across a range of finer scales. However, experimental and analytical methods to examine state changes, such as from perennial grasslands to woodlands, have not been fully developed. We first define and describe the expansion of woody plants into perennial grasslands. Woody plant encroachment has well-documented consequences for local, regional, and global ecology, and takes several forms, from shrub invasion in arid/semiarid grasslands and arctic ecosystems to tree invasion in mesic and alpine grasslands. We then outline a multi-scale experimental approach to examining the key processes influencing woody plant encroachment from fine to broad scales, and describe the application of this approach to the Jornada Basin Agricultural Research Service-Long Term Ecological Research site as a case study. Several questions can be addressed with this approach, such as: how and under what conditions do dynamics and decisions made at fine scales influence dynamics at broader scales? How and under what conditions do broad-scale dynamics overwhelm fine-scale processes to influence landscape patterns? Finally, we discuss analytical techniques for predicting regime shifts and their associated thresholds.
Keywords: broad-scale regime; pattern-process

Beyond yield: plant disease in the context of ecosystem services - Cheatham, M.R.; Rouse, M.N.; Esker, P.D.; Ignacio, S.; Pradel, W.; Raymundo, R.; Sparks, A.H.; Forbes, G.A.; Gordon, T.R.; Garrett, K.A. (Phytopathology, 2009)
The ecosystem services concept provides a means to define successful disease management more broadly, beyond short-term crop yield evaluations. Plant disease can affect ecosystem services directly, such as through removal of plants providing services, or indirectly through the effects of disease management activities, including pesticide applications, tillage, and other methods of plant removal. Increased plant biodiversity may reduce disease risk if susceptible host tissue becomes less common, or may increase risk if additional plant species are important in completing pathogen life cycles. Arthropod and microbial biodiversity may play similar roles. Distant ecosystems may provide a disservice as the setting for the evolution of pathogens that later invade a focal ecosystem, where plants have not evolved defenses. Conversely, distant ecosystems may provide a service as sources of genetic resources of great value to agriculture, including disease resistance genes. Good policies are needed to support conservation and optimal use of genetic resources, protect ecosystems from exotic pathogens, and limit the homogeneity of agricultural systems. Research is needed to provide policy makers, farmers, and consumers with the information required for evaluating trade-offs in the pursuit of the full range of ecosystem services desired from managed and native ecosystems.
Keywords: biological control

Biotic and abiotic drivers of soil microbial community recovery and ecosystem change during grasslands restoration - E.M. Bach (Southern Illinois University, 2009)
Tallgrass prairies have some of the deepest and most fertile topsoil on earth. Widespread conversion of these grasslands to agriculture has decreased soil Carbon (C) storage by exacerbating erosion and disrupting aggregates that protect C from decomposition, coupled with lower plant C inputs. Thus, a primary goal of some grassland restorations is to improve soil structure and functioning. Conversion of cultivated systems to perennial grasslands often increases soil C, microbial biomass, and soil aggregate size and stability. A few studies have documented changes in soil microbial community structure after restoration. The objective of this work was two fold: 1) to explore the importance of soil texture and 2) determine plant diversity effects on recovery of soil biotic and abiotic properties. In the first study changes in soil microbial phospholipid fatty acid (PLFA) profiles and soil aggregates were examined in two 0-19 year chronosequences of restored grasslands in Nebraska on soils differing in texture, silty clay loam (SCL) and loamy fine sand (LFS), and compared them to native prairie. Soil was collected from the 0-10 cm soil depth at each site in May of 2007 and 2008. The SCL chronosequence exhibited increases in total PLFA biomass P<0.05, r2=0.29), PLFA richness (P<0.0001, r2=0.25), fungi (P<0.0001, r2=0.65), fungal:bacterial ratio (P<0.0001, r2=0.67), Gram (+) bacteria (P=0.02, r2=0.22), Gram (-) bacteria (P=0.05, r2=0.16), and actinomycetes (P=0.02, r2=0.23). Average soil aggregate diameter also increased (p=0.0002, r2=0.52). However, LFS sites showed no change across the chronosequence for any parameter. Total PLFA biomass (ANOVA, P<0.0001), richness (P<0.0001), and fungi (P=0.005) were greater on SCL restorations than LFS, but LFS had greater fungal:bacterial ratios (P=0.02). Soil microbial groups and soil aggregates were highly correlated, especially in the LFS choronosequence indicating that structural recovery is key to microbial community recovery. The second study investigated high diversity restorations with low diversity restorations on silty clay loam. In this study, high diversity and low diversity restorations in southeast Nebraska, aged 4 and 8 years were compared. The quantity of forbs seeded was too low and high diversity communities were a mixture of dominant C4 grasses (Andropogon gerardii Vitman, Schizachyrium scoparium (Michx.) Nash, Panicum virgatum L., Bouteloua curtipendula (Michx.) Torr. and Sorghastrum nutans (L.) Nash) and subdominant C3 grasses (Elymus canadensis L., Pascopyrum smithii (Rybd.) A. Löve, and Elymus virginicus L.). Eight year old plantings had greater root biomass, root C storage, root C:N ratio (P<0.05 for all), microbial biomass (low diversity only, PC<0.1, PN<0.05), PLFA richness (low diversity only, P<0.05), mycorrhizal fungi (P<0.05), and C mineralization (low diversity only, P<0.05) than 4 year old plantings. Low diversity plantings, which contained almost exclusively dominant C4 prairie grasses, had greater root C storage (P<0.1), mycorrhizal fungi (8 years only, P<0.1), and C mineralization (8 years only, P<0.05). Thus, C4 grasses and their associated arbuscular mycorrhizal fungi seem to drive recovery of soil C, soil respiration, and soil microbial communities over time. Overall, this work indicates that rates and success of belowground recovery are dependent on both abiotic and biotic factors in restoration. Restored plant communities affected soil recovery as dominant C4 grasses appeared to drive belowground recovery, but recovery depended on soil texture.

Bud bank morphology, dynamics, and production in perennial grasses - Ott, J.P. (Kansas State University, 2009)

Centimeter-scale stream substratum heterogeneity and metabolic rates - Wilson, K.C.; W. K. Dodds (Hydrobiologia, 2009)
Spatial heterogeneity of substrata in streams may influence dissolved oxygen (O2) transport and nutrient forms. We studied the relationship between scales of substratum heterogeneity and O2. Heterogeneous systems could have greater respiration rates as a result of increased interfacial surfaces in the biogeochemically active areas between oxic and anoxic zones. We used grids with twelve 7 × 3.5 cm cells; half the cells were filled with sand and the other half with gravel to quantify the effect of centimeter-scale heterogeneity on respiration. The sand and gravel cells were arranged within the grids to give low, medium, and high heterogeneity. Grids were incubated for 15–17 days in a prairie stream, and then whole grid respiration was analyzed in closed recirculating chambers. Depth to anoxia and substratum metabolism were calculated from O2 microelectrode profiles measured in each cell of the grid and compared with data from natural stream transects from agricultural, urban, and prairie land use types. Shannon–Weaver (H′) diversity and “probability of change” indices were also used to compare heterogeneity of the grids to the natural stream transects. No significant differences were found among grid heterogeneity levels for respiration rate, but the anoxic interface was deeper in the gravel of higher heterogeneity grids, probably due to greater transport rates of O2 in the coarse-grained substratum. The H′ and probability of change indices indicated that the grids had levels of heterogeneity within the range of real streams. Grid depth to anoxia and substratum metabolism rates were similar to those found in streams, though less variable. In streams, H′ and probability of change values showed a slight difference among land use types, with some urban and agricultural sites displaying very low heterogeneity.
Keywords: Dissolved oxygen; nutrients; O2 microelectrodes; stream; Substratum

Challenges and approaches to statistical design and inference in high dimensional investigations - Gadbury, G.L.; Garrett, K.A.; Allison, D.B. (Plant Systems Biology, Methods in Molecular Biology Series, 2009)
Advances in modern technologies have facilitated high-dimensional experiments (HDEs) that generate tremendous amounts of genomic, proteomic, and other “omic” data. HDEs involving whole-genome sequences and polymorphisms, expression levels of genes, protein abundance measurements, and combinations thereof have become a vanguard for new analytic approaches to the analysis of HDE data. Such situations demand creative approaches to the processes of statistical inference, estimation, prediction, classification, and study design. The novel and challenging biological questions asked from HDE data have resulted in many specialized analytic techniques being developed. This chapter discusses some of the unique statistical challenges facing investigators studying high-dimensional biology and describes some approaches being developed by statistical scientists. We have included some focus on the increasing interest in questions involving testing multiple propositions simultaneously, appropriate inferential indicators for the types of questions biologists are interested in, and the need for replication of results across independent studies, investigators, and settings. A key consideration inherent throughout is the challenge in providing methods that a statistician judges to be sound and a biologist finds informative.
Keywords: FDR; genomics; high-dimensional; microarray; multiple testing; statistics

Characterization of the water soluble soil organic pool following the rewetting of dry soil in a drought-prone tallgrass prairie - Williams, M.A.; Xia, K. (Soil Biology & Biochemistry, 2009)
To better understand the nature of the C flush that follows the rewetting of dry soil, we chemically characterized the water soluble pools following rewetting of soil dried to several different water potentials. To assess the impact that historical soil water status has on the size of the rewetting labile soluble pool, a laboratory water stress gradient was applied to soils that were collected from drought-prone and irrigated tallgrass prairie soils. In the laboratory, soils were either incubated at −33 kPa or dried steadily over a 0.6, 1, 2, or 3 day period to −1.5, −4, −15, and −45 MPa respectively. On the 4th day, samples were wetted back to −33 kPa and immediately assayed for soluble, microbial, or respiratory pools of carbon. After extraction, samples were also assayed using NMR, GC–MS, and LC–MS to assess carbohydrate, amino acid, osmolyte and sugar pools. The greater the degree of drying before rewetting was associated with greater concentrations of microbial, soluble and respiratory pools of carbon, increasing by 50, 400 and 250%, respectively, in the most water stressed compared to continuously moist soil. Compared to drought-prone soils, the amount of soluble C released as a result of rewetting was 30 to 50% greater in soils that were irrigated for 11 years. The pool of organics was not completely characterized and only small amounts of TBDMS and TMS derived compounds accounting for 2–4% of the soluble C pool were detected. In contrast, oligosaccharides constituted approximately 20–25% of the sample C. Our results suggest that the flush of C following wetting of a dry soil is not dominated by common microbial osmolytes (e.g. proline, glycine betaine, ectoine, glycerol, mannitol, trehalose). In light of this finding more research is needed to better understand the adaptations that microbial communities utilize to respond to the rewetting of dried soil.
Keywords: Compatible solutes; Drying-rewetting; GC–MS; Microbial response to water stress; NMR

CO2 distribution in groundwater and the impact of groundwater extraction on the global C cycle - G. L. Macpherson (Chemical Geology, 2009)
Growing population and wealth, agricultural expansion, changing land use, and mechanized irrigation increase the demand on water resources. Groundwater accounts for about 20% of global water use, with agriculture the largest consumer. Groundwater CO2 partial pressures are typically ∼ 10–100 times higher than atmospheric, so CO2 degassing is an unavoidable consequence of groundwater extraction. For regional studies, very good estimates of groundwater CO2 in clastic aquifers can be calculated for temperate-climate regions from: log10(pCO2)=log10(HCO−3)−pH+7.749 where the constant is the sum of the negative logarithm (base 10) of the Henry's Law constant for CO2 and first association constant for H2CO3 at 13 °C, and titration alkalinity can be substituted for activity of HCO3−. Groundwater CO2 is not uniformly distributed in groundwater, being most variable near the water table, lowest at intermediate depth, and highest in deep aquifers where non-potable water is typical. Geochemical speciation modeling is required to assess CO2 released when groundwater equilibrates with the atmosphere. A suite of potable water types were modeled for this purpose, with the result that current groundwater production is estimated to release ∼ 0.01 to 0.03 Pg C year− 1, similar to CO2 from volcanic emissions and ∼ 200 times less than other human-sourced CO2 emissions. Determination of dissolved CO2 depends on accuracy of pH measurements: CO2 released due to groundwater use may be underestimated if reported pH measurements do not represent in situ pH.
Keywords: Carbon dioxide; CO2; Global carbon cycle; groundwater; Groundwater extraction

Connectivity of the American agricultural landscape: Assessing the national risk of crop pest and disease spread - Margosian, M.L.; Garrett, K.A.; Hutchinson, J.M.S.; With, K.A. (Bioscience, 2009)
More than two-thirds of cropland in the United States is devoted to the production of just four crop species—maize, wheat, soybeans, and cotton—raising concerns that homogenization of the American agricultural landscape could facilitate widespread disease and pest outbreaks, compromising the national food supply. As a new component in national agricultural risk assessment, we employed a graph-theoretic approach to examine the connectivity of these crops across the United States. We used county crop acreage to evaluate the landscape resistance to transmission—the degree to which host availability limits spread in any given region—for pests or pathogens dependent on each crop. For organisms that can disperse under conditions of lower host availability, maize and soybean are highly connected at a national scale, compared with the more discrete regions of wheat and cotton production. Determining the scales at which connectivity becomes disrupted for organisms with different dispersal abilities may help target rapid-response regions and the development of strategic policies to enhance agricultural landscape heterogeneity.
Keywords: geographic information systems; graph theory; Invasive species; landscape connectivity; networks

Consequences of climate variability for the performance of bison in tallgrass prairie - Craine, J.M.; Towne, E.G.; Anthony Joern; Hamilton, R.G. (Global Change Biology, 2009)
Climate variability is a major structuring factor in grassland ecosystems, yet there is great uncertainty in how changes in precipitation affect grazing herbivores. We determined how interannual variation in the timing and magnitude of precipitation affected the weight gain of free-roaming bison in their first and second year. Bison weights were analyzed for 14 years for Konza Prairie, Kansas, and 12 years for Tallgrass Prairie Preserve, Oklahoma. Greater late-summer precipitation increased bison weight gain. For every 100 mm precipitation, weight gain increased 6.4–15.3 kg depending on age classes and site. In contrast, greater midsummer precipitation decreased weight gain. For every additional 100 mm precipitation, weight decreased 9.7–17.3 kg depending on age class and site. The decreased weight gain of bison with greater midsummer precipitation was associated with increased grass stem production during the period for each of three dominant grasses at Konza Prairie. Although greater stem production increases the quantity of aboveground biomass, it should decrease the overall nutritional quality of biomass to grazers, which would reduce weight gain. With offsetting effects of mid- and late-summer precipitation on weight gain, these results show that predicting the effects of climate change on grazers must incorporate both the timing and magnitude of changes in precipitation and their effects on both the quantity and quality of biomass.

Conservation of nitrogen increases with precipitation across a major grassland gradient in the Central Great Plains of North America - McCulley, R.L.; Burke, I.C.; Lauenroth, W.K. (Oecologia, 2009)
Regional analyses and biogeochemical models predict that ecosystem N pools and N cycling rates must increase from the semi-arid shortgrass steppe to the sub-humid tallgrass prairie of the Central Great Plains, yet few field data exist to evaluate these predictions. In this paper, we measured rates of net N mineralization, N in above- and belowground primary production, total soil organic matter N pools, soil inorganic N pools and capture in resin bags, decomposition rates, foliar 15N, and N use efficiency (NUE) across a precipitation gradient. We found that net N mineralization did not increase across the gradient, despite more N generally being found in plant production, suggesting higher N uptake, in the wetter areas. NUE of plants increased with precipitation, and δ15N foliar values and resin-captured N in soils decreased, all of which are consistent with the hypothesis that N cycling is tighter at the wet end of the gradient. Litter decomposition appeared to play a role in maintaining this regional N cycling trend: litter decomposed more slowly and released less N at the wet end of the gradient. These results suggest that immobilization of N within the plant–soil system increases from semi-arid shortgrass steppe to sub-humid tallgrass prairie. Despite the fact that N pools increase along a bio-climatic gradient from shortgrass steppe to mixed grass and tallgrass prairie, this element becomes relatively more limiting and is therefore more tightly conserved at the wettest end of the gradient. Similar to findings from forested systems, our results suggest that grassland N cycling becomes more open to N loss with increasing aridity.
Keywords: Grasslands; Net nitrogen mineralization; Nitrogen pools; Nitrogen use efficiency; Regional trends

Contingent productivity responses to more extreme rainfall regimes across a grassland biome - Heisler-White, J.L.; John M. Blair; Kelly, E.F.; Harmoney, K.; Alan K. Knapp (Global Change Biology, 2009)
Climate models predict, and empirical evidence confirms, that more extreme precipitation regimes are occurring in tandem with warmer atmospheric temperatures. These more extreme rainfall patterns are characterized by increased event size separated by longer within season drought periods and represent novel climatic conditions whose consequences for different ecosystem types are largely unknown. Here, we present results from an experiment in which more extreme rainfall patterns were imposed in three native grassland sites in the Central Plains Region of North America, USA. Along this 600 km precipitation–productivity gradient, there was strong sensitivity of temperate grasslands to more extreme growing season rainfall regimes, with responses of aboveground net primary productivity (ANPP) contingent on mean soil water levels for different grassland types. At the mesic end of the gradient (tallgrass prairie), longer dry intervals between events led to extended periods of below-average soil water content, increased plant water stress and reduced ANPP by 18%. The opposite response occurred at the dry end (semiarid steppe), where a shift to fewer, but larger, events increased periods of above-average soil water content, reduced seasonal plant water stress and resulted in a 30% increase in ANPP. At an intermediate mixed grass prairie site with high plant species richness, ANPP was most sensitive to more extreme rainfall regimes (70% increase). These results highlight the inherent complexity in predicting how terrestrial ecosystems will respond to forecast novel climate conditions as well as the difficulties in extending inferences from single site experiments across biomes. Even with no change in annual precipitation amount, ANPP responses in a relatively uniform physiographic region differed in both magnitude and direction in response to within season changes in rainfall event size/frequency.

Controls of aboveground net primary production in mesic savanna grasslands: An inter-hemispheric comparison - Buis, G.M.; John M. Blair; Burkepile, D.E.; Burns, C.E.; Chamberlain, A.J.; Chapman, P.; Scott. L. Collins; Fynn, R.W.S.; Govender, N.; Kirkman, K.; M.D. Smith; Alan K. Knapp (Ecosystems, 2009)
Patterns and controls of annual aboveground net primary productivity (ANPP) are fundamental metrics of ecosystem functioning. It is generally assumed, but rarely tested, that determinants of ANPP in one region within a biome will operate similarly throughout that biome, as long as physiognomy and climate are broadly consistent. We tested this assumption by quantifying ANPP responses to fire, grazing history, and nitrogen (N) addition in North American (NA) and South African (SA) savanna grasslands. We found that total ANPP responded in generally consistent ways to fire, grazing history, and N addition on both continents. Annual fire in both NA and SA consistently stimulated total ANPP (28–100%) relative to unburned treatments at sites with deep soils, and had no effect on ANPP in sites with shallow soils. Fire did not affect total ANPP in sites with a recent history of grazing, regardless of whether a single or a diverse suite of large herbivores was present. N addition interacted strongly and consistently with fire regime in both NA and SA. In annually burned sites that were not grazed, total ANPP was stimulated by N addition (29–39%), but there was no effect of N fertilization in the absence of fire. In contrast, responses in forb ANPP to fire and grazing were somewhat divergent across this biome. Annual fire in NA reduced forb ANPP, whereas grazing increased forb ANPP, but neither response was evident in SA. Thus, despite a consistent response in total ANPP, divergent responses in forb ANPP suggest that other aspects of community structure and ecosystem functioning differ in important ways between these mesic savanna grasslands.
Keywords: ANPP; fire; Grasslands; Grazing; nitrogen; Savannas

Controls of aboveground net primary production in mesic savanna grasslands: An inter-hemispheric comparison - Buis, G. (Colorado State University, 2009)
Patterns and controls of annual aboveground net primary productivity (ANPP) are fundamental metrics of ecosystem functioning. It is generally assumed, but rarely tested, that determinants of ANPP in one region within a biome will operate similarly throughout that biome, as long as physiognomy and climate are broadly consistent. We tested this assumption by quantifying ANPP responses to fire, grazing history, and nitrogen (N) addition in North American (NA) and South African (SA) savanna grasslands. We found that total ANPP responded in generally consistent ways to fire, grazing history, and N addition on both continents. Annual fire in both NA and SA consistently stimulated total ANPP (28–100%) relative to unburned treatments at sites with deep soils, and had no effect on ANPP in sites with shallow soils. Fire did not affect total ANPP in sites with a recent history of grazing, regardless of whether a single or a diverse suite of large herbivores was present. N addition interacted strongly and consistently with fire regime in both NA and SA. In annually burned sites that were not grazed, total ANPP was stimulated by N addition (29–39%), but there was no effect of N fertilization in the absence of fire. In contrast, responses in forb ANPP to fire and grazing were somewhat divergent across this biome. Annual fire in NA reduced forb ANPP, whereas grazing increased forb ANPP, but neither response was evident in SA. Thus, despite a consistent response in total ANPP, divergent responses in forb ANPP suggest that other aspects of community structure and ecosystem functioning differ in important ways between these mesic savanna grasslands.
Keywords: ANPP; fire; Grasslands; Grazing; nitrogen; Savannas

Cross-site comparison of herbivore impact on nitrogen availability in grasslands: the role of plant nitrogen concentration - E.S. Bakker; Knops, J.M.H.; Milchunas, D.G.; Ritchie, M.E.; Olff, H. (Oikos, 2009)
Herbivores may influence the nitrogen (N) recycling rates and consequently increase or decrease the productivity of grasslands. Plant N concentration emerged as a critical parameter to explain herbivore effects from several conceptual models, which predict that herbivores decrease soil N availability when plant N concentration is low whereas they increase it when plant N concentration is high (Hobbs 1996, Ritchie et al. 1998, Pastor et al. 2006). However, a broader cross-site comparison among published studies to test these predictions is hampered by the different methodologies used to measure soil N availability or a proxy thereof, and a lack of measurements of plant N concentration. Therefore it remains unclear whether these model predictions are generally valid across a range of grasslands. We tested whether there is a relationship between plant N concentration and herbivore impact on soil N availability (measured with resin bags) with a study of replicate 6–8 year old exclosures (with an unfenced control) of vertebrate herbivores (>1 kg) established at each of seven grassland sites in North America and Europe. Contrary to model predictions, we found a negative relationship between the effect of herbivores on resin bag soil N availability and plant N concentration. Our study confirms the importance of plant N concentration as a predictor of herbivore effect on soil N availability across grasslands, but contradicts the models. A possible explanation may be that the results represent a transient situation as the exclosures were relatively young whereas the models may refer to an equilibrium state. Simultaneous measurements of both plant N concentration and herbivore effect on soil N availability from more grassland sites, preferably with contrasting plant N concentrations and including exclosures of different ages, should resolve the contrast between model predictions and our field measurements.

Discrimination of chemical stimuli in conspecific fecal pellets by a visually adept iguanid lizard, Crotaphytus collaris - Wilgers, D.J.; Horne, E.A. (Journal of Ethology, 2009)
Iguanid lizards are known for visual acuity and a diminished vomeronasal organ, which has led to mixed conclusions on whether iguanids use chemical cues. The collared lizard, Crotaphytus collaris, is a territorial iguanid that lives in open rocky habitats. Fecal pellets placed prominently on open rocky perches may provide an ideal mechanism for intraspecific chemical signaling. In order to determine whether collared lizards can discriminate between chemical stimuli found in conspecific fecal pellets, we collected 24 males and 25 females to analyze sex-specific behavioral responses via tongue-flicks and a newly observed behavior for the species, gular pumps, to cotton swabs containing water, cologne, chemical stimuli from conspecific male and female fecal pellets, and the lizard’s own fecal pellet. Both sexes were able to discriminate chemical stimuli from water via at least one behavior. Male collared lizards exhibited greater rates of response (tongue-flick and gular pumps) toward male fecal pellets when compared to the negative water control. Our results also suggest individuals may be able to discriminate between fecal pellets, as indicated by generally greater (but non-significant) counts of male tongue-flick responses to male fecal pellets when compared to their own. Collared lizard chemical discrimination appears to utilize tongue-flick and gular pump behaviors, possibly associated with distinct chemosensory modes (vomerolfaction and olfaction). Based on this study, we suggest that chemical signals may play a greater role in intraspecific communication than previously thought in this highly visual lizard.
Keywords: Chemoreception; Gular pump; Olfaction; Tongue-flick; Vomerolfaction

Disturbance frequency and functional identity mediate ecosystem processes in prairie streams - Bertrand, K.N.; K. B. Gido; W. K. Dodds; Murdock, J.N.; M.R. Whiles (Oikos, 2009)
A major consequence of climate change will be the alteration of precipitation patterns and concomitant changes in the flood frequencies in streams. Species losses or introductions will accompany these changes, which necessitates understanding the interactions between altered disturbance regimes and consumer functional identity to predict dynamics of streams. We used experimental mesocosms and field enclosures to test the interactive effects of flood frequency and two fishes from distinct consumer groups (benthic grazers and water-column minnows) on recovery of stream ecosystem properties (algal form and biomass, invertebrate densities, metabolism and nutrient uptake rates). Our results generally suggest that periphyton communities under nutrient limitation are likely to recover more quickly when grazing and water-column minnows are present and these effects can diminish or reverse with time since the disturbance. We hypothesized that increased periphyton production and biomass was the result of increased nutrient turnover, but decreased light limitation and indirect effects on other trophic levels are alternative explanations. Recovery of stream ecosystem properties after a natural flood differed from mesocosms (e.g. lower algal biomass and no long algal filaments present) and species manipulations did not explain recovery of ecosystem properties; rather, ecosystem processes varied along a downstream gradient of increasing temperature and nutrient concentrations. Different results between field enclosures and experimental mesocosms are attributable to a number of factors including differences in algal and invertebrate communities in the natural stream and relatively short enclosure lengths (mean area=35.8 m2) compared with recirculating water in the experimental mesocosms. These differences may provide insight into conditions necessary to elicit a strong interaction between consumers and ecosystem properties.

Ecophysiological responses of two dominant grasses to altered temperature and precipitation regimes - Jesse B. Nippert; Fay, P.A.; Carlisle, J.D.; Alan K. Knapp; M.D. Smith (Acta Oecologia, 2009)
Ecosystem responses to climate change will largely be driven by responses of the dominant species. However, if co-dominant species have traits that lead them to differential responses, then predicting how ecosystem structure and function will be altered is more challenging. We assessed differences in response to climate change factors for the two dominant C4 grass species in tallgrass prairie, Andropogon gerardii and Sorghastrum nutans, by measuring changes in a suite of plant ecophysiological traits in response to experimentally elevated air temperatures and increased precipitation variability over two growing seasons. Maximum photosynthetic rates, stomatal conductance, water-use efficiency, chlorophyll fluorescence, and leaf water potential varied with leaf and canopy temperature as well as with volumetric soil water content (0–15 cm). Both species had similar responses to imposed changes in temperature and water availability, but when differences occurred, responses by A. gerardii were more closely linked with changes in air temperature whereas S. nutans was more sensitive to changes in water availability. Moreover, S. nutans was more responsive overall than A. gerardii to climate alterations. These results indicate both grass species are responsive to forecast changes in temperature and precipitation, but their differential sensitivity to temperature and water availability suggest that future population and community structure may vary based on the magnitude and scope of an altered climate.
Keywords: Andropogon gerardii; Climate variability; Leaf gas exchange; RaMPs; Sensitivity; Sorghastrum nutans

The effects of fire frequency and grazing on tallgrass prairie productivity and plant composition are mediated through bud bank demography - Dalgleish, H.J.; D.C. Hartnett (Plant Ecology, 2009)
Periodic fire, grazing, and a variable climate are considered the most important drivers of tallgrass prairie ecosystems, having large impacts on the component species and on ecosystem structure and function. We used long-term experiments at Konza Prairie Biological Station to explore the underlying demographic mechanisms responsible for tallgrass prairie responses to two key ecological drivers: fire and grazing. Our data indicate that belowground bud banks (populations of meristems associated with rhizomes or other perennating organs) mediate tallgrass prairie plant response. Fire and grazing altered rates of belowground bud natality, tiller emergence from the bud bank, and both short-term (fire cycle) and long-term (>15 year) changes in bud bank density. Annual burning increased grass bud banks by 25% and decreased forb bud banks by 125% compared to burning every 4 years. Grazing increased the rate of emergence from the grass bud bank resulting in increased grass stem densities while decreasing grass bud banks compared to ungrazed prairie. By contrast, grazing increased both bud and stem density of forbs in annually burned prairie but grazing had no effect on forb bud or stem density in the 4-year burn frequency treatment. Lastly, the size of the reserve grass bud bank is an excellent predictor of long-term ANPP in tallgrass prairie and also of short-term interannual variation in ANPP associated with fire cycles, supporting our hypothesis that ANPP is strongly regulated by belowground demographic processes. Meristem limitation due to management practices such as different fire frequencies or grazing regimes may constrain tallgrass prairie responses to interannual changes in resource availability. An important consequence is that grasslands with a large bud bank may be the most responsive to future climatic change or other global change phenomena such as nutrient enrichment, and may be most resistant to exotic species invasions.
Keywords: Bud bank; fire; Grazing; Konza Prairie LTER; Meristem; Vegetative reproduction

Estimating annual net primary productivity of the tallgrass prairie ecosystem of the Central Great Plains using AVHRR NDVI - An, N. (University of Kansas, 2009)
Aboveground Net Primary Productivity (ANPP) is indicative of an ecosystem's ability to capture solar energy and store it in the form of carbon (or biomass). Annual and interannual ecosystem variation in ANPP is often linked to climatic dynamics and anthropogenic influences. The 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 of the grasslands of the region and the Flint Hills of North America represent the largest contiguous area of unplowed tallgrass prairie (1.6 million ha) (Knapp and Seastead, 1998). 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 of this system do not exist. For these reasons, this study was conducted to investigate the use of the Normalized Difference Vegetation Index (NDVI) to model ANPP for 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 significantly vary from year-to-year depending on land use and climatic conditions. The goal of this study is 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 the Konza Prairie Biological Station as the primary study area with data also from the Rannells Flint Hills Prairie Preserve and other sites near Manhattan, Kansas. The dominant study period was 1989 to 2005. The optimal period for estimating ANPP using AVHRR NDVI composite datasets is prairie 30 (late July). The Tallgrass ANPP Model (TAM) explained 53% (r2 = 0.53, r = 0.73) of the year-to-year variation. Efforts to validate the TAM results were frustrated by considerable variations among existing remote sensing based ANPP model estimates and in situ clipplot measurements of peak season tallgrass production. These findings support the conclusion that ecosystem specific ANPP models are needed to improve global scale ANPP estimates. The creation of 1 km x 1 km resolution ANPP maps for a four county (~7,000 ha) for years 1989 - 2007 showed considerable variation in annual and interannual ANPP spatial patterns suggesting complex interactions among factors influencing ANPP spatially and temporally. The observed patterns on these maps would be lost using the much coarser resolution ground weather recording stations.

Estimating the stage of incubation for nests of Greater Prairie-chickens using egg flotation: a float curve for grousers - McNew, L.B.; Gregory, A.J.; Wisely, S.M.; Sandercock, B.K. (Grouse News, 2009)
Introduction Researchers often require accurate estimates of incubation stage for back-calculating the timing of nest initiation or predicting the date of hatching to capture young, to determine the durations of egg-laying, incubation and the construction of breeding phenologies, and to calculate nest productivity. Estimates of nest age are also critical for assessment of the influence of temporal variation in nest survival, and to model daily nest survival as a function of individual-or time-specific covariates (Dinsmore et al. 2002). For example, the timing of nest losses is often related to nest success and the probability of renesting (Schroeder 1997, Pitman et al. 2006, McNew et al. in press). Egg flotation is one of the most common methods employed for estimating stage of embryo development with egg flotation-development relationships documented for many species of birds (Hays & LeCroy 1971, Dunn et al. 1979, Fisher and Sengel 1991, Custer et al. 1992, Brua & Machin 2000, Liebezeit et al. 2007). To our knowledge, there are no published techniques to estimate stage of incubation for nests of grouse. Field biologists estimating stage of incubation for eggs of grouse nests have often used a modified version of an egg flotation technique developed for captive ring-neck pheasants Phasianus colchicus and gray partridges Perdix perdix (Westerskov 1950, Martin & Cooke 1987). It is unknown whether egg flotation can be used to accurately assess age of grouse nests under field conditions. As part of a larger study on the breeding ecology of greater prairie-chickens Tympanuchus cupido; (hereafter "prairie-chickens"), McNew et al. (in press) developed a regression model to accurately predict the stage of incubation for nests from egg flotation angles and egg buoyancy. Methods Prairie-chickens were captured with walk-in traps and drop-nets at leks during March–May of 2006–2008 at three study sites in eastern Kansas, USA (Schroeder & Braun 1991, Silvy et al. 1990). Females were fitted with radio transmitters and located via triangulation >4 times/week during the nesting period (April–July), and daily once it was determined from movement patterns that a female was nesting. Once a female had localized in an area for 3 successive days, we located and flushed the bird so that the eggs could be counted and the nest location recorded with a GPS unit. Females with nests were monitored daily from a distance of >100 m. Nest sites were revisited during incubation to assess clutch size and incubation stage. Figure 1. Estimating the float angle or height of a greater prairie-chicken egg. This egg is floating at ~90° and is not yet buoyant.

A framework for assessing ecosystem dynamics in response to chronic resource alterations induced by global change - M.D. Smith; Alan K. Knapp; Scott. L. Collins (Ecology, 2009)
In contrast to pulses in resource availability following disturbance events, many of the most pressing global changes, such as elevated atmospheric carbon dioxide concentrations and nitrogen deposition, lead to chronic and often cumulative alterations in available resources. Therefore, predicting ecological responses to these chronic resource alterations will require the modification of existing disturbance-based frameworks. Here, we present a conceptual framework for assessing the nature and pace of ecological change under chronic resource alterations. The “hierarchical-response framework” (HRF) links well-documented, ecological mechanisms of change to provide a theoretical basis for testing hypotheses to explain the dynamics and differential sensitivity of ecosystems to chronic resource alterations. The HRF is based on a temporal hierarchy of mechanisms and responses beginning with individual (physiological/metabolic) responses, followed by species reordering within communities, and finally species loss and immigration. Each mechanism is hypothesized to differ in the magnitude and rate of its effects on ecosystem structure and function, with this variation depending on ecosystem attributes, such as longevity of dominant species, rates of biogeochemical cycling, levels of biodiversity, and trophic complexity. Overall, the HRF predicts nonlinear changes in ecosystem dynamics, with the expectation that interactions with natural disturbances and other global-change drivers will further alter the nature and pace of change. The HRF is explicitly comparative to better understand differential sensitivities of ecosystems, and it can be used to guide the design of coordinated, cross-site experiments to enable more robust forecasts of contemporary and future ecosystem dynamics.

Grasses and Grassland Ecology - D.J. Gibson (Oxford University Press, 2009)

Groundwater CO2: Is it responding to atmospheric CO2? - G. L. Macpherson (2009)

Heteroduplex molecules cause sexing errors in a standard molecular protocol for avian sexing - Casey, A.E.; Jones, K.L.; Sandercock, B.K.; Wisely, S.M. (Molecular Ecology Resources, 2009)
Molecular methods are a necessary tool for sexing monomorphic birds. These molecular approaches are usually reliable, but sexing protocols should be evaluated carefully because biochemical interactions may lead to errors. We optimized laboratory protocols for genetic sexing of a monomorphic shorebird, the upland sandpiper (Bartramia longicauda), using two independent sets of primers, P2/P8 and 2550F/2718R, to amplify regions of the sex-linked CHD-Z and CHD-W genes. We discovered polymorphisms in the region of the CHD-Z intron amplified by the primers P2/P8 which caused four males to be misidentified as females (n = 90 mated pairs). We cloned and sequenced one CHD-W allele (370 bp) and three CHD-Z alleles in our population: Z° (335 bp), Z′ (331 bp) and Z″ (330 bp). Normal (Z°Z°) males showed one band in agarose gel analysis and were easily differentiated from females (Z°W), which showed two bands. However, males heterozygous for CHD-Z alleles (Z′Z″) unexpectedly showed two bands in a pattern similar to females. While the Z′ and Z″ fragments contained only short deletions, they annealed together during the polymerase chain reaction (PCR) process and formed heteroduplex molecules that were similar in size to the W fragment. Errors previously reported for molecular sex-assignment have usually been due to allelic dropout, causing females to be misidentified as males. Here, we report evidence that events in PCRs can lead to the opposite error, with males misidentified as females. We recommend use of multiple primer sets and large samples of known-sex birds for validation when designing protocols for molecular sex analysis.
Keywords: 2550F/2718R; Bartramia longicauda; CHD-Z; molecular sexing; P2/P8; Upland Sandpiper

High propagule production and reproductive fitness homeostasis contribute to the invasiveness of Lespedeza cuneata (Fabaceae) - Woods, T.M.; D.C. Hartnett; Ferguson, C.J. (Biological Invasions, 2009)
Comparative studies of congeneric native and exotic species have proved fruitful in understanding plant traits that foster invasion. Using this approach, we investigate the complex reproductive system of the invasive Lespedeza cuneata (Dum.-Cours.) G. Don in relation to three native congeners in the variable environment of the North American tallgrass prairie. Lespedeza species produce both chasmogamous (CH) and cleistogamous (CL) flowers, and propagate clonally via vegetative buds. Utilizing multiple natural populations over 2 years, we investigated reproductive modes of individuals from bagged and unbagged treatments of each species. We found that L. cuneata produced a mean of five times as many seeds and a significantly greater number of vegetative buds than any native studied, and over twenty times as many CH flowers. Insect visitation significantly affected seed set in CH flowers, though some autonomous CH selfing occurred in all species. The invasive relied relatively less on selfing than the natives and exhibited less variation in reproductive output from both modes of reproduction. We conclude that the diverse reproductive biology and wide regeneration niche of L. cuneata in relation to its native congeners confer a fitness homeostasis that facilitates the successful spread of this invasive under a wide range of conditions.
Keywords: Cleistogamy; Fitness homeostasis; Invasive; Lespedeza; Pollination; Propagule production; Regeneration niche; tallgrass prairie

Highly polymorphic microsatellites in the North American snakeweed grasshopper, Hesperotettix viridis - Grace, T.; Anthony Joern; Brown, S.J.; Apple, J.L.; Wisely, S.M. (Journal of Orthoptera Research, 2009)
Microsatellite markers are preferred for fine-scale population genetic studies requiring high resolution. The grasshopper Hesperotettix viridis (Thomas) is an oligophagous species that feeds on composites and often exhibits locally restricted diets. Divergence in host plant use in some localities is seen where co-occurring subpopulations select alternate plant species, as expected with the evolution of host shifts and associated lineage divergence. To characterize the host-associated divergence patterns among populations of H. viridis, we developed markers from two microsatellite-enriched genomic libraries. Here we report the characterization and optimization of seven polymorphic di- and tri-nucleotide microsatellite loci for this species. One hundred and six individuals from 5 populations were tested for polymorphism. The number of alleles varied from 4 to 38 in all the populations. Ho ranged from 0.339 to 0.790. Homozygote excess was observed across loci, perhaps due to inbreeding. This is the first report of microsatellite markers for the subfamily Melanoplinae.
Keywords: Hesperotettix viridis; host-associated divergence; local adaptation; microsatellite markers; snakeweed grasshopper

Hippocampal volumes and neuron numbers increase along a gradient of environmental harshness: a large-scale comparison - Roth, T.C.; Pravosudov, V.V. (Proceedings of the Royal Society B, 2009)
Environmental conditions may provide specific demands for memory, which in turn may affect specific brain regions responsible for memory function. For food-caching animals, in particular, spatial memory appears to be important because it may have a direct effect on fitness via the accuracy of cache retrieval. Animals living in more harsh environments should rely more on cached food, and thus theoretically should have better memory to support cache retrieval, which may be crucial for survival. Consequently, animals in harsh environments may benefit from more neurons within a larger hippocampus (Hp), a part of the brain involved in spatial memory. Here, we present the first large-scale test of the hypothesis that Hp structure is related to the severity of the environment within a single food-caching species (the black-capped chickadee, Poecile atricapillus) with a large range encompassing a great diversity of climatic conditions. Hp size in birds collected at five locations along a gradient of environmental harshness from Alaska to Kansas ranked perfectly with climatic severity. Birds from more harsh northern climates (defined by lower ambient temperature, shorter day length and more snow cover) had significantly larger Hp volumes and more Hp neurons (both relative to telencephalon volume) than those from more mild southern latitudes. Environmental pressures therefore seem capable of influencing specific brain regions independently, which may result in enhanced memory, and hence survival, in harsh climates.

Host associated genetic divergence and sexual isolation in the grasshopper Hesperotettix viridis (Orthoptera: Acrididae) - Grace, T. (Kansas State University, 2009)
Understanding evolutionary processes that structure genetic variation associated with lineage diversification and speciation is a central problem. Shifts in host plant use by insect herbivores and subsequent divergence in mating signals can lead to sexual isolation, especially when selection for specialization on different hosts restricts gene flow among populations. The grasshopper Hesperotettix viridis (Thomas) is an oligophagous grasshopper feeding on plants primarily in the host plant genera Gutierrezia and Solidago in Kansas. I used mitochondrial and microsatellite genetic markers to evaluate the diversification pattern and underlying evolutionary mechanisms of two putative host races of H. viridis. I also quantified host preferences, the degree of sexual isolation among putative host races and divergence in cuticular attributes to identify the nature and origins of initial barriers that isolated populations in the formative stages of divergence. mtDNA data revealed a star-shaped phylogeny, suggesting isolation in a single refugium ~110,000 years ago based on a molecular clock, followed by rapid population expansion. Microsatellite data reveal significant host-based genetic differentiation and structuring in H. viridis populations in Kansas, including a microsatellite locus under strong divergent selection. Neutral microsatellite loci did not reveal a differentiation pattern specific to host plant use. Significant host-based preferences by individuals that fed on two host plant groups were detected in host paired-feeding preference studies. No-choice mate selection experiments revealed preferences for individuals collected from the same host species independent of location with little mating observed between individuals from different host species. Significant differentiation in color and cuticular composition among different host plant races within the study area was also detected. Correlations between host choice, mate choice and phenotypic divergence were observed and this host associated divergence appears to have a genetic basis. Based on the results of this study, I conclude that divergent selection for host plant use underlies observed sexual isolation among populations in this species. Hesperotettix viridis populations in Kansas that fed on Solidago and Gutierrezia species represent two incipient host races, early stages of diversification that could lead to speciation in insect herbivores.
Keywords: Hesperotettix viridis; Host Associated Divergence; Microsatellites; Population genetics; sexual isolation; Speciation

Impacts of management legacies on litter decomposition in response to reduced precipitation in a tallgrass prairie - Reed, H.E.; John M. Blair; Wall, D.; Seastedt, T.R. (Applied Soil Ecology, 2009)
The response of ecosystem processes to current and future climatic events may be affected by historical disturbance regimes. Here, we address the interaction between reduced precipitation and the legacy effects of two contrasting long-term burn regimes in a tallgrass prairie (20 years of annual burning versus fire suppression). We examined rates of decomposition and the response of decomposition to reduced precipitation under rainout shelters in these two prairie types to assess potential interactions between legacy effects and reduced precipitation. To test the legacy effects of the different burn regimes, we placed experimental plots in each prairie type under a standardized management regime. In each plot, we ceased burning, mowed to maintain a standard canopy height, and maintained standard surface litter accumulation. We measured decay rates for surface litter, buried roots, and buried wooden dowels. While decomposition rates of substrates were reduced an average of approximately 29% under reduced precipitation, we found no significant main effects of burn history on decomposition on any of the substrates. However, in the recovery period following 2 years of an experimentally imposed drought, we did find an effect of burn history on decomposition and this effect varied for different substrates. Historical effects of management or natural disturbances on ecosystem processes may often be subtle or negated by compensatory responses, and in this study few legacy effects on decomposition rate were detected.
Keywords: burning; decomposition; Drought; Legacy effects; Management regime; tallgrass prairie

The influence of host ecology and land cover change on rabies virus epidemiology in the Flint Hills - Bowe, S.E. (Kansas State University, 2009)
As human populations increase world-wide, land use and land cover are altered to support the rapid anthropogenic expansion. These landscape alterations influence patterns of zoonotic infectious disease emergence and propagation. It is therefore becoming increasingly important to study emerging and re-emerging diseases to predict and manage for future epidemics. Studies of directly-transmitted infectious diseases should consider three components of disease epidemiology: characteristics of the pathogen, ecology of the host, and habitat configuration of the underlying landscape. I studied the influence of both the host ecology of the striped skunk (Mephitis mephitis) and the alteration of the underlying landscape on the epidemiology of rabies virus in the Flint Hills of Kansas. This tall-grass prairie is experiencing woody expansion due to anthropogenic disturbance, altering the landscape on which the rabies virus emerges and spreads. We first studied the behavioral and social ecology of the striped skunk using field and genetic methods. We concluded that 1) striped skunks reached high population densities in anthropogenically disturbed habitats, 2) these individuals were not closely related, and 3) contact rates could be influenced by temperature. Using habitat-specific skunk densities from this initial study, we created spatially-explicit contact networks of skunk populations across the Upper Kansas River Watershed and simulated the emergence and spread of rabies through the system. This modeling approach revealed a threshold of forest habitat beyond which striped skunks became increasingly connected and the rabies virus reached greater extents across the landscape. Based on these findings we recommend fire regimes and land cover alterations to reduce woody encroachment across the Flint Hills and to avoid future disease epidemics in the region.
Keywords: Epidemiological network modeling; Flint Hills; Mephitis mephitis; Rabies virus; woody encroachment

The influence of land use on stream biofilm nutrient limitation across eight North American ecoregions - Johnson, L.T.; Tank, J.L.; W. K. Dodds (Canadian Journal of Fisheries and Aquatic Sciences, 2009)
Nutrient diffusing substrata were used to determine the influence of inorganic nitrogen (N) and phosphorus (P) availability on community respiration (CR), gross primary production (GPP), and chlorophyll a (chl a) on inorganic and organic substrata. We incubated substrata in nine streams each in a total of eight ecoregions (n = 72 streams) located in a range of native vegetation, agriculture, and urban land-use types. On organic substrata, CR was nutrient-limited in 94% of reference streams but showed significant nutrient limitation in only 60% and 65% of agricultural and urban streams, respectively. The relative magnitude of nutrient limitation for CR on organic substrata decreased with increasing percent modified land use in the basin (agriculture + urban). On inorganic and organic substrata, GPP and chl a were rarely nutrient-limited across all ecoregions and land-use types, although the magnitude of nutrient limitation increased with increasing light availability. The effect of human land use on nutrient limitation of biofilm CR, GPP, and chl a was influenced by ecoregion, yet heterotrophic biofilms were consistently most sensitive to nutrient enrichment across ecoregions. Both heterotrophic and autotrophic biofilm constituents should be considered to fully understand stream ecosystem responses to nutrient enrichment.

Interactions between grassland birds and their snake predators: the potential for conservation conflicts in the tallgrass prairie - Klug, P.E. (Kansas State University, 2009)
The loss, fragmentation, and degradation of grasslands have resulted in widespread declines in grassland birds. Nest predation is the leading cause of avian reproductive failure; therefore minimizing nest predation can lessen the severity of bird declines. Snakes are important predators of bird nests, but little is known about how snakes may enhance predation risk. To address this issue, I studied the habitat use, movement behavior, population genetic structure, and connectivity of snakes in the grasslands of northeastern Kansas. I addressed the connectivity of eastern yellowbelly racer (Coluber constrictor flaviventris) populations by using a landscape genetics approach at a broad scale (13,500 km2). I also radio-tracked the yellowbelly racer and Great Plains ratsnake (Pantherophis emoryi) at Konza Prairie Biological Station to understand their spatial ecology while simultaneously evaluating nest survival in grassland birds. Individual racers had limited dispersal (<3 km), but substantial admixture occurred within 30 km and populations were in migration-drift equilibrium and had high allelic diversity; therefore, racers must be abundant and continuously distributed for gene flow to be fluid throughout the region. Racers may be more likely to encounter bird nests, as they had more frequent movements and traversed greater distances on average than ratsnakes, which exhibited long periods of inactivity between directed movements. As for grassland birds, nest survival rates decreased with increasing shrubs and decreasing vegetation height. Discriminant function analysis revealed that successful nests were likely to occur in tall vegetation but reduced shrub cover, whereas higher shrub cover characterized snake habitats. Because snakes often use shrubs, nests in areas of increased shrubs may be at higher risk of predation by snakes. Targeted removal of shrubs may increase nest success by minimizing the activity of predators attracted to shrubs. Although predator removal is often a strategy for protecting bird populations, it may not be feasible in this instance, especially since snakes are a native component of the grassland community. Efforts to reduce snake predation on grassland bird nests should therefore focus on managing habitat within grasslands (i.e., shrubs) that influence snake activity, as no natural or anthropogenic habitat barriers currently limit snake movement across the landscape.
Keywords: Coluber constrictor; Grassland birds; Nest predation; Pantherophis emoryi; Predator-prey relationships; tallgrass prairie

Landscape-level variation in temperature sensitivity of soil organic carbon decomposition - Craine, J.M.; Spurr, R.; McLauchlan, K.K.; Fierer, N. (Soil Biology & Biochemistry, 2009)
We examined landscape-level variation in temperature sensitivity of labile SOC across 71 sites at a central North American grassland. The observed range in activation energy of decomposition (Ea), an index of temperature sensitivity, was as great at the landscape scale as has been observed at the continental scale. Ea was lower for soils with more labile C, consistent with the ‘Carbon quality-temperature’ hypothesis. Soil pH explained 67% of the variation in Ea. Although there are strong environmental correlates with the Ea of SOC decomposition at landscape scales, the amount of variation within landscapes could confound regional- to global-scale predictions of the response of soil C to warming.
Keywords: grassland; Microbial respiration; Soil organic carbon; Temperature sensitivity; Warming

Laws, Theories, and Patterns in Ecology - W. K. Dodds (University of California Press, 2009)

Limiting temperatures for urediniospore germination are low in a systemic rust fungus of tallgrass prairie - Worapong, J.; Dendy, S.P.; Tang, Z.; Awl, D.J.; Garrett, K.A. (Mycologia, 2009)
Potential responses of plant disease phenology to climate change have been addressed primarily in agricultural systems. As a first step toward understanding the phenology of Uropyxis petalostemonis, a rust fungus commonly infecting the legume Dalea candida in USA tallgrass prairie, we evaluated the effects of temperature on urediniospore germination. While urediniospore germination for many rust fungi has been reported to decline only when temperatures are well above 25 C, in vitro germination of U petalostemonis dropped sharply at this temperature. Responses observed on water agar, potato dextrose agar and lima bean agar were similar, although lima bean agar supported a higher percentage germination overall. The low limiting temperatures suggest that most epidemically important new infections by U petalostemonis occur in spring. High summer temperatures in tallgrass prairie might push infection by this rust fungus species to earlier in the year and select for stronger systemic growth characteristics.
Keywords: Basidiomycetes; Dalea candida; Fabaceae; phenology; Uredinales; Uropyxis petalostemonis

Long-term patterns of mass loss during the decomposition of leaf and fine root litter: an intersite comparison - Harmon, M.E.; Silver, W.L.; Fasth, B.; Chen, H.; Burke, I.C.; Parton, W.J.; Hart, S.C.; Currie, W.S. (Global Change Biology, 2009)
Decomposition is a critical process in global carbon cycling. During decomposition, leaf and fine root litter may undergo a later, relatively slow phase; past long-term experiments indicate this phase occurs, but whether it is a general phenomenon has not been examined. Data from Long-term Intersite Decomposition Experiment Team, representing 27 sites and nine litter types (for a total of 234 cases) was used to test the frequency of this later, slow phase of decomposition. Litter mass remaining after up to 10 years of decomposition was fit to models that included (dual exponential and asymptotic) or excluded (single exponential) a slow phase. The resultant regression equations were evaluated for goodness of fit as well as biological realism. Regression analysis indicated that while the dual exponential and asymptotic models statistically and biologically fit more of the litter type–site combinations than the single exponential model, the latter was biologically reasonable for 27–65% of the cases depending on the test used. This implies that a slow phase is common, but not universal. Moreover, estimates of the decomposition rate of the slowly decomposing component averaged 0.139–0.221 year−1 (depending on method), higher than generally observed for mineral soil organic matter, but one-third of the faster phase of litter decomposition. Thus, this material may be slower than the earlier phases of litter decomposition, but not as slow as mineral soil organic matter. Comparison of the long-term integrated decomposition rate (which included all phases of decomposition) to that for the first year of decomposition indicated the former was on average 75% that of the latter, consistent with the presence of a slow phase of decomposition. These results indicate that the global store of litter estimated using short-term decomposition rates would be underestimated by at least one-third.

Massively parallel 454-sequencing of Quercus macrocarpa phyllosphere fungal communities indicates reduced richness and diversity in urban environments - A. Jumpponen; Jones, K.L. (New Phytologist, 2009)
• This study targeted the fungal communities in the phyllosphere of Quercus macrocarpa and compared the fungal species richness, diversity and community composition among trees located within and outside a small urban center using recently developed 454 sequencing and DNA tagging. • The results indicate that the fungal phyllosphere communities are extremely diverse and strongly dominated by ascomycetes, with Microsphaeropsis [two Operational Taxonomic Units (OTUs); 23.6%], Alternaria (six OTUs; 16.1%), Epicoccum (one OTU; 6.0%) and Erysiphe (two OTUs; 5.9%) as the most abundant genera. • Although the sequencing effort averaged 1000 reads per tree and detected nearly 700 distinct molecular OTUs at 95% internal transcribed spacer 1 similarity, the richness of the hyperdiverse phyllosphere communities could not be reliably estimated as nearly one-half of the molecular OTUs were singletons. • The fungal communities within and outside the urban center differed in richness and diversity, which were lower within the urban development. The two land-use types contained communities that were distinct and more than 10% of the molecular OTUs differed in their frequency.

Mysterious mycorrhizae? A field trip and classroom experiment to demystify the symbioses formed between plants and fungi - Johnson, N.C.; Chaudhary, V.B.; Hoeksema, J.D.; Moore, J.M.; Pringle, A.; Umbanhowar, J.A.; G.T. Wilson (American Biology Teacher, 2009)

Nitrate removal in stream ecosystems measured by 15N addition experiments: Total uptake - Hall, R.O. Jr.; Tank, J.L.; Sobota, D.J.; Mulholland, P.J.; O'Brien, J.M.; W. K. Dodds; Webster, J.R.; Valett, H.M.; Poole, G.C.; Peterson, B.J.; Meyer, J.L.; W.H. McDowell; et al. (Limnology and Oceanography, 2009)
We measured uptake length of 15NO3− in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO3− uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban-urban, and agricultural land uses. Study streams spanned a range of human land use to maximize variation in NO3− concentration, geomorphology, and metabolism. We tested a causal model predicting controls on NO3− uptake length using structural equation modeling. The model included concomitant measurements of ecosystem metabolism, hydraulic parameters, and nitrogen concentration. We compared this structural equation model to multiple regression models which included additional biotic, catchment, and riparian variables. The structural equation model explained 79% of the variation in log uptake length (SWtot). Uptake length increased with specific discharge (Q/w) and increasing NO3− concentrations, showing a loss in removal efficiency in streams with high NO3− concentration. Uptake lengths shortened with increasing gross primary production, suggesting autotrophic assimilation dominated NO3− removal. The fraction of catchment area as agriculture and suburban-urban land use weakly predicted NO3− uptake in bivariate regression, and did improve prediction in a set of multiple regression models. Adding land use to the structural equation model showed that land use indirectly affected NO3− uptake lengths via directly increasing both gross primary production and NO3− concentration. Gross primary production shortened SWtot, while increasing NO3− lengthened SWtot resulting in no net effect of land use on NO3− removal.

Nitrate removal in stream ecosystems measured by 15N addition experiments: Denitrification - Mulholland, P.J.; Hall, R.O.; Sobota, D.J.; W. K. Dodds; Findlay, S.E.G.; Grimm, N.B.; Hamilton, S.K.; W.H. McDowell; O'Brien, J.M.; Tank, J.L.; L.R. Ashkenas; Cooper, L.W.; et al. (Limnology and Oceanography, 2009)
We measured denitrification rates using a field 15NO3− tracer-addition approach in a large, cross-site study of nitrate uptake in reference, agricultural, and suburban-urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification (SWdenn) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land-use categories, likely because of the wide range of conditions within each region and land use. N2 production rates far exceeded N2O production rates in all streams. The fraction of total NO3− removal from water due to denitrification ranged from 0.5% to 100% among streams (median of 16%), and was related to NH4+ concentration and ecosystem respiration rate (ER). Multivariate approaches showed that the most important factors controlling SWden were specific discharge (discharge / width) and NO3− concentration (positive effects), and ER and transient storage zones (negative effects). The relationship between areal denitrification rate (Uden) and NO3− concentration indicated a partial saturation effect. A power function with an exponent of 0.5 described this relationship better than a Michaelis-Menten equation. Although Uden increased with increasing NO3− concentration, the efficiency of NO3− removal from water via denitrification declined, resulting in a smaller proportion of streamwater NO3− load removed over a given length of stream. Regional differences in stream denitrification rates were small relative to the proximate factors of NO3− concentration and ecosystem respiration rate, and land use was an important but indirect control on denitrification in streams, primarily via its effect on NO3− concentration.

Non-target and invasive species in rehabilitated production systems: Ecological impacts, management and future use - S.G. Baer; Engle, D.; Knops, J.M.H.; Langeland, K.A.; Maxwell, B.D.; Menalled, F.D.; Symstad, A. (Environmental Management, 2009)

Parent-absent begging in the Brown-headed Cowbird (Molothrus ater): the role of short-term need and nestmate size - Rivers, J.W. (Behavioral Ecology and Sociobiology, 2009)
Although it is well-established that nestlings of many altricial species beg when parents are away from the nest, we have a poor understanding of parent-absent begging in brood parasites, including the proximate factors that may influence begging frequency and intensity. In this study, I examined how parent-absent begging was influenced by competitive asymmetries between host and Brown-headed Cowbird (Molothrus ater) nestlings under disparate levels of short-term need. Food-deprived cowbird nestlings begged more frequently and for a greater proportion of parent-absent period than when food-supplemented, with similar patterns observed in hosts of different sizes. In contrast, three metrics of cowbird begging intensity varied relative to host size but not due to differences in short-term need. Cowbirds consistently begged more frequently and intensively than host nestlings for a given level of short-term need, providing evidence that cowbird begging displays are more frequent and intense than non-parasitic nestlings during both feeding visits and parent-absent periods. In sum, the frequency of begging by cowbirds was only influenced by short-term need, whereas begging intensity during parent-absent events was only influenced by the host against which cowbirds competed. This study demonstrates that host size and short-term need had differing influences on the frequency and intensity of parent-absent begging in cowbirds, although both factors are likely important in limiting the evolution of parent-absent begging in cowbirds. Because it appears to provide no immediate benefits yet may decrease fitness, parent-absent begging should be included in future theoretical models investigating the evolution of begging displays in nestling birds.
Keywords: begging; brown-headed cowbird; generalist brood parasite; Molothrus ater; Parent-absent begging

Plant pathogens as indicators of climate change - Garrett, K.A.; Nita, M.; De Wolf, E.D.; Gomez, L.; Sparks, A.H. (Climate and Global Change: Observed Impacts on Planet Earth, 2009)

Polymorphic microsatellite markers for the striped skunk, Mephitis mephitis, and other mephitids - Dragoo, J.W.; Coan, K.E.; Moore, K.A.; Henke, S.E.; Fleisher, R.C.; Wisely, S.M. (Molecular Ecology Resources, 2009)
We report 10 polymorphic microsatellite loci primers developed for striped skunks (Mephitis mephitis), a widespread mesocarnivore in North America. Numbers of alleles in these loci ranged from seven to 14 and the observed heterozygosity ranged from 0.76 to 1.0. These primers will be useful for studying population dynamics of skunks where rabies is endemic and will be useful to estimate genetic relatedness among females sharing winter dens. Most of these primers amplify across species within the Mephitidae.
Keywords: hog-nosed skunk; hooded skunk; Mephitis mephitis; microsatellite primers; spotted skunk; striped skunk

Soil aggregation and carbon sequestration are tightly correlated with the abundance of arbuscular mycorrhizal fungi: results from long-term field experiments - G.T. Wilson; C. W. Rice; Rillig, M.C.; Springer, A.; D.C. Hartnett (Ecology Letters, 2009)
We examined the role of arbuscular mycorrhizal fungi (AMF) in ecosystems using soil aggregate stability and C and N storage as representative ecosystem processes. We utilized a wide gradient in AMF abundance, obtained through long-term (17 and 6 years) large-scale field manipulations. Burning and N-fertilization increased soil AMF hyphae, glomalin-related soil protein (GRSP) pools and water-stable macroaggregates while fungicide applications reduced AMF hyphae, GRSP and water-stable macroaggregates. We found that AMF abundance was a surprisingly dominant factor explaining the vast majority of variability in soil aggregation. This experimental field study, involving long-term diverse management practices of native multispecies prairie communities, invariably showed a close positive correlation between AMF hyphal abundance and soil aggregation, and C and N sequestration. This highly significant linear correlation suggests there are serious consequences to the loss of AMF from ecosystems.

Spatial heterogeneity of denitrification genes in a highly homogenous urban stream - Knapp, C.W.; W. K. Dodds; Wilson, K.C.; O’Brien, J.M.; Graham, D.W. (Environmental Science & Technology, 2009)
Human modification of natural streams by urbanization has led to more homogeneous channel surfaces; however, the influence of channel simplification on in situ microbial distribution and function is poorly characterized. For example, denitrification, a microbial process that reduces soluble nitrogen (N) levels, requires peripheral anoxic zones that might be lost in artificial channels such as those with a concrete lining. To examine how microbial function might be influenced by channel simplification, we quantified denitrification rates and conditions in microbial mats within an urban concrete channel. We quantified spatial and diurnal patterns of nitrate uptake, diurnal dissolved oxygen (DO) levels, and nutrient conditions, along with the spatial distribution of DO, solids, chlorophyll a, and genes associated with denitrification (nirS and nirK), ammonia-oxidizing bacteria (AOB), cyanobacteria, and algal chloroplasts. Despite the channel being superficially homogeneous, nir genes were distributed in a patchy manner. Two types of gene patches were observed: one associated with nirK, which had diurnally variable DO levels and high nocturnal nitrate uptake rates, and the other associated with nirS, which had elevated AOB genes, thicker layers of mud, and an apparent 24 h nitrate uptake. All active nir patches had elevated microbial photosynthetic genes. Results imply that even artificial channels, with reduced macroscale heterogeneity, can sustain significant rates of denitrification, although the responsible communities vary with space and time. This patchiness has significant implications to extending local data to landscape level predictions and field sampling strategies but also suggests alternate channel designs to increase N retention rates.

Stream discharge and riparian land use influence in-stream concentrations and loads of phosphorus from Central Plains watersheds - Banner, E.B.K.; Stahl, A.J.; W. K. Dodds (Environmental Management, 2009)
Total annual nutrient loads are a function of both watershed characteristics and the magnitude of nutrient mobilizing events. We investigated linkages among land cover, discharge and total phosphorus (TP) concentrations, and loads in 25 Kansas streams. Stream monitoring locations were selected from the Kansas Department of Health and Environment stream chemistry long-term monitoring network sites at or near U.S. Geological Survey stream gauges. We linked each sample with concurrent discharge data to improve our ability to estimate TP concentrations and loads across the full range of possible flow conditions. Median TP concentration was strongly linked (R 2 = 76%) to the presence of cropland in the riparian zones of the mostly perennial streams. At baseflow, discharge data did not improve prediction of TP, but at high flows discharge was strongly linked to concentration (a threshold response occurred). Our data suggest that on average 88% of the total load occurred during the 10% of the time with the greatest discharge. Modeled reductions in peak discharges, representing increased hydrologic retention, predicted greater decreases in total annual loads than reductions of ambient concentrations because high discharge and elevated phosphorus concentrations had multiplicative effects. No measure of land use provided significant predictive power for concentrations when discharge was elevated or for concentration rise rates under increasing discharge. These results suggest that reductions of baseflow concentrations of TP in streams without wastewater dischargers may be managed by reductions of cropland uses in the riparian corridor. Additional measures may be needed to manage TP annual loads, due to the large percentage of the TP load occurring during a few high-flow events each year.
Keywords: Discharge; Perennial streams; Riparian zones; total phosphorus; Watershed management

Thresholds in macroinvertebrate biodiversity and stoichiometry across water-quality gradients in Central Plains (USA) streams - Evans-White, M.A.; W. K. Dodds; Huggins, D.G.; Baker, D.S. (Journal of the North American Benthological Society, 2009)
N and P often limit primary and secondary production in ecosystems, but they also can cause eutrophication and negatively influence sensitive species above a certain level or threshold point. Aquatic biodiversity can have negative threshold relationships with water-quality variables at large scales, but the specific mechanism(s) driving these threshold relationships are not well established. We hypothesized that resource quality (i.e., C:P) might partly drive primary consumer (grazer and detritivore) richness thresholds by altering competitive interactions among species with differing resource demands, but might have less influence on predator richness. We estimated total N (TN), total P (TP), and turbidity thresholds for macroinvertebrate richness across trophic levels and feeding groups in Central Plains (USA) streams. We also determined if mean taxon body C:P of groups with diversity losses were negatively related to TP, a pattern that would suggest that eutrophic communities were dominated by a few species with high dietary P demands. Primary consumers were more sensitive to TN and TP (threshold mean  =  1.0 mg N/L and 0.06 mg P/L) than secondary consumers (threshold mean  =  0.09 mg P/L), a result supporting the resource quality hypothesis. Turbidity reduced richness regardless of feeding mode (threshold mean  =  4.7 NTU), a result suggesting that turbidity and nutrient thresholds were driven by different factors. The TP-richness threshold could be driven partially by changes in food quality because the mean body C:P of shredding and collector-gathering taxa declined as TP increased (threshold mean  =  0.07 and 0.75 mg P/L, respectively). Mean scraper C:P was not related to TP, a result indicating other factors might be responsible for the scraper richness threshold. Our results suggest that changes in resource quality could contribute to large-scale losses in biodiversity in nutrient-enriched lotic ecosystems. Within shredder and collector-gatherer macroinvertebrate feeding groups, P-rich food might allow faster growing taxa with high body P demands to out-compete slower growing taxa adapted to lower quality food resources. This pattern suggests that biotic integrity is directly linked to nutrients in streams and that toxicity, low dissolved O2, and increased turbidity might not be the only mechanisms leading to reductions in diversity as nutrient concentrations increase.
Keywords: bioassessment; breakpoints; eutrophication; nutrient criteria; Species richness; water quality

Tough times call for bigger brains - Roth, T.C.; Pravosudov, V.V. (Communicative and Integrative Biology, 2009)
Memory is crucial for survival in many animals. Spatial memory in particular is important for food-caching species and may be influenced by selective pressures such as climate. The influence of climate on memory may be facilitated through the hippocampus (Hp), the part of the brain responsible in part for spatial memory. In a recent paper, we conducted the first large-scale test of the relationship between memory, the climate, and the brain in a single food-caching species, the black-capped chickadee (Poecile atricapillus). We found that birds from more harsh northern climates had significantly larger hippocampal volumes and more neurons than those from more mild southern latitudes. This work suggests that environmental pressures are capable of influencing specific brain regions, which may result in enhanced memory, and hence survival, in harsh climates. This work gives us a better understanding of how the brain responds to different environments and how animals can adapt to their environment in general.

Tracking the rhythm of the seasons in the face of global change: phenological research in the 21st century - Morisette, J.T.; Richardson, A.D.; Alan K. Knapp; Fisher, J.I.; Graham, E.A.; Abatzoglou, J.; Wilson, B.E.; Breshears, D.D.; Henebry, G.M.; Hanes, J.M.; Liang, L. (Frontiers in Ecology and the Environment, 2009)
Phenology is the study of recurring life-cycle events, classic examples being the flowering of plants and animal migration. Phenological responses are increasingly relevant for addressing applied environmental issues. Yet, challenges remain with respect to spanning scales of observation, integrating observations across taxa, and modeling phenological sequences to enable ecological forecasts in light of future climate change. Recent advances that are helping to address these questions include refined landscape-scale phenology estimates from satellite data, advanced, instrument-based approaches for field measurements, and new cyberinfrastructure for archiving and distribution of products. These breakthroughs are improving our understanding in diverse areas, including modeling land-surface exchange, evaluating climate–phenology relationships, and making land-management decisions.

Transition and resilience in the Kansas Flint Hills - Middendorf, G.; Becerra, T.A.; Cline, D. (Online Journal of Rural Research and Policy, 2009)
The tallgrass prairie has persisted in the Flint Hills of east-central Kansas for both biophysical and socioeconomic reasons, and has been one of the key elements in the development of the region. A population boom in the latter part of the 19th century and the subsequent increase in cattle in the 1860s-1870s were key factors in the transition of this landscape into a major cattle grazing region by the turn of the 20th century. At various points in the past 150 years, this social ecosystem has exhibited remarkable resilience in episodes of both drought and over-grazing. The resilience of the bluestem pastures had implications for stability in the rural economy. Yet, the land use regimes have undergone change since Euro-American arrival, thus the human signature on the land is by no means static. We approach the human-environment relationship as an ecological dialogue that includes both biophysical and social elements mutually shaping each other, and driven by human interests as much as biophysical factors. Current threats to the tallgrass prairie, including fragmentation and invasive species are discussed.
Keywords: Geography; Geology; Great Plains Studies; Sociology

Variation in benefit from arbuscular mycorrhizal fungal colonization within cultivars and non-cultivars of Andropogon gerardii and Sorghastrum nutans - Campbell, R.E. (Southern Illinois University, 2009)
Wide-scale conversion of tallgrass prairie to row-crop agriculture has spurred restoration of this endangered ecosystem. At the onset of restoration, a matrix of native plant species is sown into former crop field and includes warm-season (C4) grasses, cool-season (C3) grasses, legumes, and a large variety of herbaceous forbs. Increased demand for native seed due to a greater number of areas targeted for restoration has increased use of C4 grass cultivars by restoration practitioners. Cultivars are selectively bred to display traits such as increased productivity and digestibility, thus highlighting their original use in rangelands of the Great Plains. C4 grasses have a mutualistic relationship with arbuscular mycorrhizal fungi (AMF). In remnant tallgrass prairie, AMF can increase C4 plant uptake of belowground resources (e.g., water, soil P) by increasing root surface area. It is unknown if AMF colonization varies between seed source (cultivar or non-cultivar) of C4 grasses used in restoration and if this further affects plant biomass. Intraspecific variation in AMF colonization between two dominant warm-season prairie grasses was tested in two established prairie restoration experiments, both having plots seeded with either C4 cultivars or non-cultivars. To test for effects of seed source and AMF colonization on plant biomass, a greenhouse experiment was designed using two source populations (cultivar and non-cultivar) of two species (Andropogon gerardii Vitman and Sorghastrum nutans (L.) Nash) and soil collected at each field restoration (Kansas and Illinois). To suppress activity and colonization of AMF, a fungicide (Allban Flo: Thiophanate Methyl) was applied to half of the containers. Warm-season (C4) grass cultivars had greater or equivalent biomass production than non-cultivars at the onset of field restoration and also in the greenhouse. Furthermore, cultivars generally had less or equivalent root colonization by AMF and dependence on fungicide-free soil was greater in cultivars to retain increased accrual of biomass. It was, however, not possible to determine the role of AMF in plant biomass production as fungicide did not successfully reduce AMF root colonization in cultivars or non-cultivars, with one exception. It is critical that an effective AMF-suppression treatment be established in these types of studies. Future experiments should validate supposed effectiveness of the newly-recommended fungicide (Topsin-M) in population sources of warm-season prairie grasses and also apply it to the soil at time of planting in greenhouse studies. In the field sites, adjacent soil cultivation may have contributed to greater AMF biomass more so than surrounding remnant prairie. Future research identifying species composition of AMF at these sites is necessary to clarify differences in biomass. Despite greater plant biomass in cultivars, soil nutrient availability remained equivalent between source populations in general. Available N and P were not less in soils grown with cultivars, however soil inorganic N was inversely related to root length colonized by AMF, suggesting a role of AMF in N transfer from soil to plant. Soil P was not different between source populations likely due to legacy effects of agricultural fertilization, thus limiting a well known benefit of AMF symbiosis, at least at the onset of restoration. Non-target effects of fungicide application were observed (e.g., changes in available N) and effectiveness of AMF suppression was questionable. Fungicide lowered pH and increased N availability in soil as indicated by main effects of application and a positive relationship between pH and inorganic N across species. Fungicide application either 1) decreased N uptake by soil microorganisms (possibly including AMF) or 2) increased competition for adsorption sites and/or solubility of total inorganic N as pH changed, thus making this nutrient more available in the soil solution. Future examination quantifying indirect effects of fungicide application on soil chemistry should also be considered to better elucidate role of AMF in plant growth and soil nutrient availability between cultivars and non-cultivars of warm-season grasses used in tallgrass prairie restoration.

The water budget, climate variability, and climate impacts assessment in Northeast Kansas - Wilson, I.E.; J. J. Harrington; McLauchlan, K.K.; Martinson, E.J.; Hutchinson, S.L. (2009)

The woodland vole on Konza Prairie Biological Station, Kansas - D.W. Kaufman; Kaufman, G.A. (Transactions of the Kansas Academy of Science, 2009)

Agrarian Landscape Transition in the Flint Hills of Kansas:Legacies and Resilience - Middendorf, G.; Cline, D.; Bloomquist, L. (Agrarian Landscapes in Transition: Comparisons of Long TermEcological&Cultural Change, 2008)

Altered rainfall due to climate change: Modeling the ecological effects on grasslands - Hoover, D.L. (University of Connecticut, 2008)
The acceleration of the hydrological cycle due to global climate change is predicted to cause more extreme precipitation, characterized by fewer but more intense storms. Such altered rainfall patterns will have significant impacts on water limited ecosystems such as grasslands. This project used a land surface model, the Community Land Model 3.0 coupled with a dynamic vegetation model, to examine how changing the size and frequency of rain events impacts plants, surface hydrology and surface energy budgets in the tallgrass prairie ecosystem. We applied a similar rainfall scheme as the Rainfall Manipulation Plots at Konza Prairie Biological Station in Kansas, which consisted of an altered rainfall treatment, with fewer but more intense events, and an ambient treatment, which replicated the natural pattern of rain. Both the model and field experiments show a reduction in grass productivity from the ambient to the altered treatment and a negative correlation between soil moisture variability and productivity. In addition, based on the modeling results, the altered rainfall treatment increases runoff, decreases evapotranspiration, and increases sensible heat flux at the expense of latent heat flux.
Keywords: Climate variability; Ecosystems; Impacts of global change; Land/atmosphere interactions; structure and dynamics

Ammonium uptake and mineralization in prairie streams: chamber incubation and short-term nutrient addition experiments - O'Brien, J.M.; W. K. Dodds (Freshwater Biology, 2008)
1. We used two separate approaches to estimate ambient ammonium cycling in the north and south branches of Kings Creek, a prairie stream. Chamber experiments were conducted to determine ammonium uptake and mineralization rates associated with epilithic biofilms and filamentous algae collected from the streams. A series of short-term whole-stream ammonium addition experiments were also conducted to estimate the rate of uptake at ambient stream concentrations, based on the relationship between ammonium concentrations and uptake rates. 2. Chamber experiments were scaled up to whole-stream levels, resulting in ambient gross uptake estimates of 0.08 μg−2 s−1 for the north branch and 0.16 μg−2 s−1 for the south branch. The substrata-specific estimates of mineralization were higher than uptake in both streams. 3. Substrata-specific measurements indicated that ammonium uptake is higher in riffle habitats than in pools habitats. The results of the short-term ammonium addition experiments support these findings. 4. Short-term ammonium addition experiments show that uptake rates saturate with increasing ammonium concentrations. The observed saturation of uptake rates is consistent with a Michaelis–Menten relationship. 5. Scaled estimates of uptake from the chamber experiments were similar to estimates of ambient ammonium uptake based on the whole-stream experiments, and were comparable with previous estimates of ammonium uptake and mineralization made by using stable isotope tracer methods in Kings Creek.

Antibiotic resistance of Enterococci in American bison (Bison bison) from a nature preserve compared to that of Enterococci in pastured cattle - Anderson, J. F.; Parrish, T.D.; Akhtar, M.; Zurek, L.; Hirt, H. (Applied and Environmental Microbiology, 2008)
Enterococci isolated from a bison population on a native tall-grass prairie preserve in Kansas were characterized and compared to enterococci isolated from pastured cattle. The species diversity was dominated by Enterococcus casseliflavus in bison (62.4%), while Enterococcus hirae was the most common isolate from cattle (39.7%). Enterococcus faecalis was the second most common species isolated from bison (16%). In cattle, E. faecalis and Enterococcus faecium were isolated at lower percentages (3.2% and 1.6%, respectively). No resistance to ampicillin, chloramphenicol, gentamicin, or high levels of vancomycin was detected from either source. Tetracycline and erythromycin resistance phenotypes, encoded by tetO and ermB, respectively, were common in cattle isolates (42.9% and 12.7%, respectively). A significant percentage of bison isolates (8% and 4%, respectively) were also resistant to these two antibiotics. The tetracycline resistance genes from both bison and cattle isolates resided on mobile genetic elements and showed a transfer frequency of 10−6 per donor, whereas erythromycin resistance was not transferable. Resistance to ciprofloxacin was found to be higher in enterococci from bison (14.4%) than in enterococci isolated from cattle (9.5%). The bison population can serve as a sentinel population for studying the spread and origin of antibiotic resistance.

Applied biodiversity science: Managing emerging diseases in agriculture and linked natural systems - Garrett, K.A.; Cox, C.M. (Infectious DiseaseEcology: Effects of Ecosystems on Disease and of Disease on Ecosystems, 2008)

Assessing the multi-resolution information content of remotely sensed variables and elevation for evapotranspiration in a tall-grass prairie environment - N. Brunsell; J.M. Ham; Owensby, C.E. (Remote Sensing of Environment, 2008)
Understanding the spatial scaling behavior of evapotranspiration and its relation to controlling factors on the land surface is necessary to accurately estimate regional water cycling. We propose a method for ascertaining this scaling behavior via a combination of wavelet multi-resolution analysis and information theory metrics. Using a physically-based modeling framework, we are able to compute spatially distributed latent heat fluxes over the tall-grass prairie in North-central Kansas for August 8, 2005. Comparison with three eddy-covariance stations and a large aperture scintillometer demonstrates good agreement, and thus give confidence in the modeled fluxes. Results indicate that the spatial variability in radiometric temperature (a proxy for soil moisture) most closely controls the spatial variability in evapotranspiration. Small scale variability in the water flux can be ascribed to the small scale spatial variance in the fractional vegetation. In addition, correlation analysis indicates general scale invariance and that low spatial resolution data may be adequate for accurately determining water cycling in prairie ecosystems.
Keywords: Entropy; information theory; Konza Prairie; Latent heat; MODIS; Spatial heterogeneity; SVAT model; wavelets

Biogeochemical changes associated with Juniperus virginia encroachment into grasslands - McKinley, D.C.; Norris, M.D.; Johnson, L.C.; John M. Blair (Ecological Studies Vol. 196, Western North American Juniperus communities: A dynamic vegetation type, 2008)

Bobolinks (Dolichonyx oryzivorus) nesting at Konza Prairie Biological Station, Riley County, Kansas - M.A. Blundell; Von Korff, B. (Bulletin of the Kansas Ornithological Society, 2008)

Changes in grassland ecosystem function due to extreme rainfall events: implications for responses to climate change - Fay, P.A.; Kaufman, D.M.; Jesse B. Nippert; Carlisle, J.D.; Harper, C.W. (Global Change Biology, 2008)
Climate change is causing measurable changes in rainfall patterns, and will likely cause increases in extreme rainfall events, with uncertain implications for key processes in ecosystem function and carbon cycling. We examined how variation in rainfall total quantity (Q), the interval between rainfall events (I), and individual event size (SE) affected soil water content (SWC) and three aspects of ecosystem function: leaf photosynthetic carbon gain (inline image), aboveground net primary productivity (ANPP), and soil respiration (inline image). We utilized rainout shelter-covered mesocosms (2.6 m3) containing assemblages of tallgrass prairie grasses and forbs. These were hand watered with 16 I×Q treatment combinations, using event sizes from 4 to 53 mm. Increasing Q by 250% (400–1000 mm yr−1) increased mean soil moisture and all three processes as expected, but only by 20–55% (P≤0.004), suggesting diminishing returns in ecosystem function as Q increased. Increasing I (from 3 to 15 days between rainfall inputs) caused both positive (inline image) and negative (inline image) changes in ecosystem processes (20–70%, P≤0.01), within and across levels of Q, indicating that I strongly influenced the effects of Q, and shifted the system towards increased net carbon uptake. Variation in SE at shorter I produced greater response in soil moisture and ecosystem processes than did variation in SE at longer I, suggesting greater stability in ecosystem function at longer I and a priming effect at shorter I. Significant differences in ANPP and inline image between treatments differing in I and Q but sharing the same SE showed that the prevailing pattern of rainfall influenced the responses to a given event size. Grassland ecosystem responses to extreme rainfall patterns expected with climate change are, therefore, likely to be variable, depending on how I, Q, and SE combine, but will likely result in changes in ecosystem carbon cycling.

Climate change and plant disease risk - Garrett, K.A. (Global Climate Change and Extreme Weather Events: Understanding the Contributions to Infectious Disease Emergence, 2008)
Research in the effects of climate change on plant disease continues to be limited, but some striking progress has been made. At the genomic level, advances in technologies for the high-throughput analysis of gene expression have made it possible to begin discriminating responses to different biotic and abiotic stressors and potential trade-offs in responses. At the scale of the individual plant, enough experiments have been performed to begin synthesizing the effects of climate variables on infection rates, though pathosystemspecific characteristics make synthesis challenging. Models of plant disease have now been developed to incorporate more sophisticated climate predictions. At the population level, the adaptive potential of plant and pathogen populations may prove to be one of the most important predictors of the magnitude of climate change effects. Ecosystem ecologists are now addressing the role of plant disease in ecosystem processes and the challenge of scaling up from individual infection probabilities to epidemics and broader impacts.

Coexisting generalist herbivores occupy unique nutritional feeding niches - Behmer, S.T.; Anthony Joern (Proceedings of the National Academy of Sciences, 2008)
A mainstay of ecological theory and practice is that coexisting species use different resources, leading to the local development of biodiversity. However, a problem arises for understanding coexistence of multiple species if they share critical resources too generally. Here, we employ an experimental framework grounded in nutritional physiology to show that closely related, cooccurring and generalist-feeding herbivores (seven grasshopper species in the genus Melanoplus; Orthoptera: Acrididae) eat protein and carbohydrate in different absolute amounts and ratios even if they eat the same plant taxa. The existence of species-specific nutritional niches provides a cryptic mechanism that helps explain how generalist herbivores with broadly overlapping diets might coexist. We also show that performance by grasshoppers allowed to mix their diets and thus regulate their protein–carbohydrate intake matched optimal performance peaks generated from no-choice treatments. These results indicate the active nature of diet selection to achieve balanced diets and provide buffering capacity in the face of variable food quality. Our empirical findings and experimental approach can be extended to generate and test predictions concerning the intensity of biotic interactions between species, the relative abundance of species, yearly fluctuations in population size, and the nature of interactions with natural enemies in tritrophic niche space.
Keywords: Biodiversity; Competition; geometric framework; physiological ecology; resource partitioning

Comparing ecosystem goods and services provided by restored and native lands - W. K. Dodds; Wilson, K.C.; Rehmeier, R.L.; Knight, G.L.; Wiggam, S.; Falke, J.A.; Dalgleish, H.J.; Bertrand, K.N. (BioScience, 2008)
We determined the relative benefits for eight categories of ecosystem goods and services associated with native and restored lands across the conterminous United States. Less than 10% of most native US ecosystems remain, and the proportion that is restored varies widely by biome. Restored lands offer 31% to 93% of native land benefits within a decade after restoration, with restored wetlands providing the most economic value and deserts providing the least. Restored ecosystems that recover rapidly and produce valuable commodities return a higher proportion of total value. The relative values of the benefits provided by restoration vary both by biome and by the ecosystem goods and services of interest. Our analysis confirms that conservation should be the first priority, but that restoration programs across broad geographic regions can have substantial value. “No net loss” policies should recognize that restored lands are not necessarily equivalent to native areas with regard to estimated ecosystem benefits.
Keywords: conservation; ecosystem goods; ecosystem services; ecosystem valuation; restoration

Comparison of damage to native and exotic tallgrass prairie plants by natural enemies - Han, X.; Dend, S.P.; Garrett, K.A.; Fang, L.; M.D. Smith (Plant Ecology, 2008)
We surveyed the prevalence and amount of leaf damage related to herbivory and pathogens on 12 pairs of exotic (invasive and noninvasive) and ecologically similar native plant species in tallgrass prairie to examine whether patterns of damage match predictions from the enemy release hypothesis. We also assessed whether natural enemy impacts differed in response to key environmental factors in tallgrass prairie by surveying the prevalence of rust on the dominant C4 grass, Andropogon gerardii, and its congeneric invasive exotic C4 grass, A. bladhii, in response to fire and nitrogen fertilization treatments. Overall, we found that the native species sustain 56.4% more overall leaf damage and 83.6% more herbivore-related leaf damage when compared to the exotic species. Moreover, we found that the invasive exotic species sustained less damage from enemies relative to their corresponding native species than the noninvasive exotic species. Finally, we found that burning and nitrogen fertilization both significantly increased the prevalence of rust fungi in the native grass, while rust fungi rarely occurred on the exotic grass. These results indicate that reduced damage from enemies may in part explain the successful naturalization of exotic species and the spread of invasive exotic species in tallgrass prairie.
Keywords: Enemy release hypothesis; grassland; Invasiveness; Leaf damage; Rust fungi

Consequences of more extreme precipitation regimes for terrestrial ecosystems - Alan K. Knapp; Beier, C.; Briske, D.D.; Classen, A.T.; Luo, Y.; Reichstein, M.; M.D. Smith; Smith, S.D.; Bell, J.E.; Fay, P.A.; Heisler, J.L.; Leavitt, S.W; et al. (BioScience, 2008)
mplification of the hydrological cycle as a consequence of global warming is forecast to lead to more extreme intra-annual precipitation regimes characterized by larger rainfall events and longer intervals between events. We present a conceptual framework, based on past investigations and ecological theory, for predicting the consequences of this underappreciated aspect of climate change. We consider a broad range of terrestrial ecosystems that vary in their overall water balance. More extreme rainfall regimes are expected to increase the duration and severity of soil water stress in mesic ecosystems as intervals between rainfall events increase. In contrast, xeric ecosystems may exhibit the opposite response to extreme events. Larger but less frequent rainfall events may result in proportional reductions in evaporative losses in xeric systems, and thus may lead to greater soil water availability. Hydric (wetland) ecosystems are predicted to experience reduced periods of anoxia in response to prolonged intervals between rainfall events. Understanding these contingent effects of ecosystem water balance is necessary for predicting how more extreme precipitation regimes will modify ecosystem processes and alter interactions with related global change drivers.
Keywords: Climate change; Drought; Ecosystems; Precipitation; soil water

Conversion of grassland to coniferous woodland has limited effects on soil nitrogen cycle processes - McKinley, D.C.; C. W. Rice; John M. Blair (Soil Biology & Biochemistry, 2008)
In the last century, conversion of native North American grasslands to Juniperus virginiana forests or woodlands has dramatically altered ecosystem structure and significantly increased ecosystem carbon (C) stocks. We compared soils under recently established J. virginiana forests and adjacent native C4-dominated grassland to assess changes in potential soil nitrogen (N) transformations and plant available N. Over a 2-year period, concentrations of extractable inorganic N were measured in soils from forest and grassland sites. Potential gross N ammonification, nitrification, and consumption rates were determined using 15N isotope-dilution under laboratory conditions, controlling for soil temperature and moisture content. Potential nitrification rates (Vmax) and microbial biomass, as well as soil physical and chemical properties were also assessed. Extractable NH4+ concentrations were significantly greater in grassland soils across the study period (P ≤ 0.01), but analysis by date indicated that differences in extractable inorganic N occurred more frequently in fall and winter, when grasses were senescent but J. virginiana was still active. Laboratory-based rates of gross N mineralization (ammonification) and nitrification were greater in grassland soils (P ≤ 0.05), but only on one of four dates. Potential nitrification rates (Vmax) were an order of magnitude greater than gross nitrification rates in both ecosystems, suggesting that nitrification is highly constrained by NH4+ availability. Differences in plant uptake of N, C inputs, and soil microclimate as forests replace grasslands may influence plant available N in the field, as evidenced by seasonal differences in soil extractable NH4+, and total soil C and N accumulation. However, we found few differences in potential soil N transformations under laboratory conditions, suggesting that this grassland-to-forest conversion caused little change in mineralizable organic N pools or potential microbial activity.
Keywords: Extractable N; Forest encroachment; grassland; Isotope dilution; Juniperus; Microbial biomass; Mineralization; nitrification; Nitrogen cycling; prairie

Cowbird removals unexpectedly increase productivity of a brood parasite and the songbird host - Kosciuch, K.L.; Sandercock, B.K. (Ecological Applications, 2008)
Generalist brood parasites reduce productivity and population growth of avian hosts and have been implicated in population declines of several songbirds of conservation concern. To estimate the demographic effects of brood parasitism on Bell's Vireos (Vireo bellii), we removed Brown-headed Cowbirds (Molothrus ater) in a replicated switchback experimental design. Cowbird removals decreased parasitism frequency from 77% and 85% at unmanipulated plots to 58% and 47% at removal plots in 2004 and 2005, respectively. Vireo productivity per pair was higher at cowbird removal plots when years were pooled (mean = 2.6 ± 0.2 [SE] young per pair) compared to unmanipulated plots (1.2 ± 0.1). Nest desertion frequency was lower at cowbird removal plots (35% of parasitized nests) compared to unmanipulated plots (69%) because removal of host eggs was the proximate cue for nest desertion, and vireos experienced lower rates of egg loss at cowbird removal plots. Nest success was higher among unparasitized than parasitized nests, and parasitized nests at cowbird removal plots had a higher probability of success than parasitized nests at unmanipulated plots. Unexpectedly, cowbird productivity from vireo pairs was higher at cowbird removal plots (mean = 0.3 ± 0.06 young per pair) than at unmanipulated plots (0.1 ± 0.03) because fewer parasitized nests were deserted and the probability of nest success was higher. Our study provides the first evidence that increases in cowbird productivity may be an unintended consequence of cowbird control programs, especially during the initial years of trapping when parasitism may only be moderately reduced. Thus, understanding the demographic impacts of cowbird removals requires an informed understanding of the behavioral ecology of host–parasite interactions.

Dark spetate fungal endophytes from a tallgrass prairie and their continuum of interactions with host plants - Mandyam, Keerthi. (Kansas State University, 2008)

Defoliation synchronizes above-ground growth of co-occurring C4 grass species - Swemmer, A.M.; Alan K. Knapp (Ecology, 2008)
The aboveground net primary productivity (ANPP) of grass communities in grasslands and savannas is primarily determined by precipitation quantity. Recent research, motivated by predictions of changes in the distribution of rainfall events by global climate change models, indicates that ANPP may be affected by rainfall distribution as much as by annual totals. Grazing and community composition are also known to affect grassland ANPP. The manner in which interactions between rainfall distribution, grazing, and community composition affect the relationship between precipitation and ANPP represents a critical knowledge gap. The effects of community composition and grazing on aboveground growth responses to intraseasonal variation in water availability were investigated at seven grassland sites with a nonselective clipping experiment. The aboveground growth of the dominant C4 species at each site was measured at regular intervals for 2–3 growing seasons in the presence or absence of regular defoliation. In the absence of defoliation, there was a general lack of synchrony of intraseasonal growth among co-occurring species. Variation in growth rates was high and was only partially explained by variation in rainfall. Regular defoliation increased growth synchrony at all sites, but changes in growth responses to rainfall varied between sites. These results suggest that community composition will be important in determining ANPP–precipitation relationships under conditions of altered rainfall distribution. However this effect appears to be a result of species responding differently to soil water or other resources rather than to rainfall per se. Grazing may override the effects of community composition by reducing differences in growth patterns between species and has the potential to weaken precipitation controls on ANPP.

Demographic sensitivity of population change in the Northern Bobwhite - Sandercock, B.K.; Jensen, W.E.; Williams, C.K.; Applegate, R.D. (Journal of Wildlife Management, 2008)
The northern bobwhite (Colinus virginianus) is an economically important gamebird that is currently undergoing widespread population declines. Despite considerable research on the population ecology of bobwhites, there have been few attempts to model population dynamics of bobwhites to determine the contributions of different demographic parameters to variance of the finite rate of population change (λ). We conducted a literature review and compiled 405 estimates of 9 demographic parameters from 49 field studies of bobwhites. To identify demographic parameters that might be important for management, we used life-stage simulation analyses (LSA) to examine sensitivity of λ to simulated variation in 9 demographic parameters for female bobwhites. In a baseline LSA based on uniform distributions bounded by the range of estimates for each demographic parameter, bobwhite populations were predicted to decline (λ = 0.56) and winter survival of adults made the greatest contribution to variance of λ (r2 = 0.453), followed by summer survival of adults (r2 = 0.163), and survival of chicks (r2 = 0.120). Population change was not sensitive to total clutch laid, nest survival, egg hatchability, or 3 parameters associated with the number of nesting attempts (r2 <0.06). Our conclusions were robust to alternative simulation scenarios, and parameter rankings changed only if we adjusted the lower bounds of winter survival upwards. Bobwhite populations were not viable with survival rates reported from most field studies. Survival rates may be depressed below sustainable levels by environmental conditions or possibly by impacts of capture and telemetry methods. Overall, our simulation results indicate that management practices that improve seasonal survival rates will have the greatest potential benefit for recovery of declining populations of bobwhites.
Keywords: Colinus virginianus; fecundity; life-stage simulation analysis; population model; quail; survival

Development of water usage coefficients for the fully-watered tallgrass prairie - Hutchinson, S.L.; Koelliker, J.K.; Alan K. Knapp (Transactions of the American Society of Agricultural Engineers, 2008)

Diversity, function and potential applications of the root-associated endophytes - Kageyama, S.A.; Mandyam, K.G.; A. Jumpponen (Mycorrhiza Genetics and Molecular Biology, Eco-Function, Biotechnology, Ecophysiology, Structure and Systematics, 2008)

Does dietary-P affect feeding and performance in the mixed-feeding grasshopper (Acrididae) Melanoplus bivitattus? - Loaiza, V.; Jonas, J.L.; Anthony Joern (Environmental Entomology, 2008)
Although consequences of limited dietary protein and carbohydrate to performance are well studied for terrestrial insect herbivores, the importance of phosphorus (P) remains poorly understood. We examined the significance of dietary P to performance in fifth-instar nymphs of the grasshopper Melanoplus bivittatus fed artificial diets. Consumption, digestion, developmental rate, and growth in response to different levels of P nested within standard-Protein and carbohydrate diets were determined. Developmental rate was slowest on high-P diets; protein:carbohydrate concentration and P in diets affected frass production and consumption. Approximate digestibility and conversion of digested food were primarily influenced by the protein:carbohydrate quality of the diet but not P. Mass gain was marginally lower in the low-Protein:high carbohydrate diet used in this study. At the individual level, other than small effects to developmental rate at high concentrations for M. bivittatus, dietary P otherwise seems to have little effect on nymphal performance. To the degree that it is important, effects of dietary P depend on the concentrations of protein and carbohydrate in the diet.
Keywords: dietary phosphorus limitation to grasshopper; multiple nutrients; nutritional ecology; nutritional indices; secological stoichiometry

Ecological consequences of the replacement of native grassland by Juniperus virginiana and other woody plants - Alan K. Knapp; McCarron, J.K.; Silletti, A.M.; Hoch, G.A.; Heisler, J.L.; Lett, M.S.; John M. Blair; J. M. Briggs; M.D. Smith (Ecological Studies Vol. 196, Western North American Juniperus communities: A dynamic vegetation type, 2008)
Although grasslands have been altered by humans for thousands of years (Wedel 1961; Bond et al. 2003), the loss of grassland as a result of anthropogenic activities has increased dramatically over the past 150 years. When Europeans first settled the Midwest and Great Plains, the greatest threat to native grasslands was the conversion of the most highly productive of these ecosystems to row-crop agriculture (Samson and Knopf 1994). Later, with improvements in soil moisture management and irrigation technology, even low-productivity grasslands were plowed. Today, those remnants of the most productive grasslands that escaped the plow are threatened, as are most of Earth’s ecosystems, by a variety of global change phenomena (Vitousek et al. 1997), with the invasion and expansion of woody species into grasslands one of the greatest of these threats. The replacement of grasslands by shrubland, woodland, and forest is a concern not only in the United States but worldwide (Archer et al. 1988; Van Auken 2000; Roques et al. 2001; Silva et al. 2001). Species of woody plants that invade grasslands may include both native plants which previously existed as more minor components of the ecosystem as well as alien species (Bragg and Hulbert 1976; Harcombe et al. 1993).

Ecological genomics of nematode responses to different bacterial environments - Coolon, J.D. (Kansas State University, 2008)
Determining the genetic mechanisms involved in organismal response to environmental change is essential for understanding the effects of anthropogenic disturbance. The composition of the bacterial-feeding nematode community is an excellent biological indicator of disturbance, particularly in grassland ecosystems. We have previously shown that grassland soil nematodes are responsive to perturbations in the field including the addition of nitrogen fertilizer. We are interested in how this perturbation affects the microbial community and downstream effects on the next trophic level, the bacterial-feeding nematodes. To determine the effects of disturbance on soil bacterial communities we used massively parallel sequencing and found that chronic nitrogen addition on tallgrass prairie significantly impacts overall bacterial community diversity and the abundance of specific bacterial taxa. Because native soil nematodes lack well developed genomic tools, we employed Caenorhabditis elegans as a model for native soil nematode taxa and used transcriptional profiling to identify 204 candidate genes regulated in response to altered bacterial diets isolated from grassland soils. To biologically validate our results we used mutations that inactivate 21 of the identified genes and showed that most contribute to fitness or lifespan in a given bacterial environment. Although these bacteria may not be natural C. elegans food sources, this study aimed to show how changes in food source, as can occur in environmental disturbance, has large effects on gene expression and those genes whose expression are affected, contribute to fitness. Furthermore, we identified new functions for genes of unknown function as well as previously well-characterized genes, demonstrating the utility of this approach to further describe C. elegans genome. We also investigated the function of previously well-characterized C. elegans defense pathways in our grassland soil bacterial environments and found that some are environment specific. Additionally, we found that cuticular collagen genes are important for lifespan, and appear to function downstream of known defense pathways. Overall, our results suggest that anthropogenic disturbance in grasslands alters the most basal components of the soil food web, bacteria and bacterial-feeding nematodes through the genes they possess and how they are expressed, and resultant bottom-up effects could have profound consequences on ecosystem health and function.
Keywords: Caenorhabditis elegans; Ecological genomics; Innate immunity; Soil bacteria

The effects of bison grazing on plant diversity in a tallgrass prairie (Konza Prairie LTER). Teaching Issues and Experiments in Ecology - Dalgleish, H.J.; Woods, T.M. (Teaching Issues and Experiments in Ecology, 2008)

Effects of experimental cowbird removals on brood parasitism and nest predation in a grassland songbird - Sandercock, B.K.; Hewett, E.L.; Kosciuch, K.L. (Auk, 2008)
Brood parasitism and predation are two factors that limit seasonal fecundity in grassland songbirds. We removed Brown-headed Cowbirds (Molothrus ater) in a switchback experiment to examine the effects of brood parasitism and nest predation on the productivity of Dickcissels (Spiza americana). Nesting Dickcissels were monitored at four study plots in northeast Kansas in a two-year study. Brown-headed Cowbirds were captured with drop-in traps at two removal plots, two unmanipulated plots were reference plots, and treatments were reversed between years. To evaluate the effect of Brown-headed Cowbird removals, we compared the percentage of nests parasitized, rates of multiple parasitism, clutch size, daily nest survival rates, and overall productivity per nest between removal and reference plots. Removals of Brown-headed Cowbirds successfully reduced the probability of parasitism and rates of multiple parasitism, but only in one of two years. Brown-headed Cowbirds did not appear to contribute to nest losses, given that few nests were abandoned because of cowbird activity and that the probabilities of nest parasitism and nest survival declined simultaneously over the breeding season. Overall, nest productivity showed no difference between treatments in either year, despite reduced rates of parasitism at removal plots in 2004. High rates of nest predation minimized the potential benefits of Brown-headed Cowbird removals for increasing productivity of Dickcissels. Our results demonstrate that removals can reduce parasitism levels but that the success of removal programs may vary annually, particularly in regions where Brown-headed Cowbirds and nest predators are abundant. Management actions that minimize parasitism and predation by modifying habitat structure may provide better alternatives to programs based on removals.
Keywords: brown-headed cowbird; Dickcissel; fecundity; management; Molothrus ater; productivity; Spiza americana

Effects of grazing minnows (Phoxinus erythrogaster) and crayfish (Orconectes nais and O. neglectus) on stream ecosystem structure and function - Bengtson, J.R.; Evans-White, M.A.; K. B. Gido (Journal of the North American Benthological Society, 2008)
We compared the effects of 2 common grazers, southern redbelly dace (Phoxinus erythrogaster) and crayfish (Orconectes spp.), on ecosystem structure and function in experimental streams with pool and riffle habitats. Our goal was to identify potentially overlapping roles of these grazers in these systems. Measures of ecosystem structure included algal filament length, particulate organic matter (POM), densities of invertebrate taxa, and algal biomass. Ecosystem function was measured as gross primary productivity (GPP). Biomass-dependent effects of crayfish and dace on ecosystem properties were compared in autumn 2005 when mean water temperature was 12.9°C (range 7.6–27.9°C). Increasing crayfish biomass did not influence ecosystem properties, but increasing dace biomass negatively affected algal filament length and chironomid abundance and positively affected chydorid abundance. Effects of moderately high biomasses of dace and crayfish were compared in spring 2006 when mean water temperature was 21.4°C (range 17.5–29.9°C). Algal filament lengths were generally low relative to values obtained in autumn 2005 in both dace and crayfish treatments. In addition, algal filament length was shorter and chironomid density was lower in crayfish than in dace streams. The contrasting effects of dace and crayfish across sampling days, seasons, and habitats led us to hypothesize that physiological and behavioral traits of these species might limit the redundancy of their effects on ecosystems across broad spatial and temporal scales.
Keywords: context-dependent effects; experimental streams; foraging behavior; periphyton; physiology; Prairie stream; Primary production; Temperature

Exposure of migratory shorebirds to organophosphorus and carbamate pesticides at migratory stopover and non-breeding sites in the western hemisphere - Strum, K.M. (Kansas State University, 2008)
Monitoring programs indicate that numerous shorebird populations are subject to ongoing declines. The U.S. Shorebird Conservation Plan lists twenty-seven shorebird species as species of high concern and seven as highly imperiled, including the Buff-breasted Sandpiper (Tryngites subruficollis). One hypothesis for ongoing population declines is exposure to toxic chemicals and pollutants. The purpose of this project was to characterize plasma cholinesterases (ChEs) of migratory shorebirds and address potential exposure to organophosphorus (OP) and carbamate (CB) pesticides. Consumption or contact with these pesticides can cause mortality and a variety of sub-lethal effects. Buff-breasted Sandpipers and other upland shorebirds are particularly likely to encounter agrochemicals due to their habitat use at the non-breeding grounds. I sampled migratory shorebirds over three seasons, during north- and southbound migration in 2006 and 2007 in Texas, Kansas, and Nebraska and during the non-breeding season in 2007 in Argentina, Uruguay, and Paraguay. I collected blood samples and footwashings from reference sites, where OP and CB pesticides were not used, and agricultural sites, where these two insecticides were recommended for control of crop pests. I assessed several variables known to affect plasma ChE activity including body size, date of capture, time of capture, condition, sex, and region. Small-bodied species had higher levels of ChE activity in plasma than large-bodied species. Plasma ChE activities varied with date of capture in 3 of 5 species sampled in North America. Sex differences were significant in 1 of 4 species tested. Plasma acetylcholinesterase (AChE) activity was higher among White-rumped Sandpipers sampled in North America but there was no difference between regions among Buff-breasted Sandpipers. Time of capture and individual condition did not affect plasma ChE activity. Estimates of exposure to ChE inhibitors were addressed in five species. Plasma AChE and butyrylcholinesterase (BChE) activities of Buff-breasted Sandpipers were lower at agricultural sites in South America but BChE activity was higher at agricultural sites in North America. There were no differences between sites in four other species tested. A meta-analysis across all species indicated that in 4 of 6 comparisons habitat type had a negative effect on AChE activity consistent with exposure to ChE inhibitors but there was a regional positive effect of agricultural habitat on BChE activity in North America. Comparison of body mass between sites suggested that use of habitats with potential pesticide application did not affect mass gain. Project results suggest that 1 of 5 shorebird species tested was exposed to ChE-inhibiting pesticides at the nonbreeding grounds and future monitoring is necessary to assess potential effects at the population level. This study highlights the importance of complete sampling and addressing variability in plasma ChEs before making estimates of exposure to OP and CB pesticides. It provides the first estimates of migratory shorebird exposure to OP and CB pesticides, a potential conservation issue. Future research should include continued monitoring of Buff-breasted Sandpiper ChE levels and habitat use. Other sources of anthropogenic declines such as habitat loss and illegal hunting should be investigated for species that did not show evidence of exposure.

Fine-scale genetic structure and extra-pair parentage in the socially monogamous Upland Sandpiper - Casey, A.E. (Kansas State University, 2008)
In birds, the offspring of females in socially monogamous species can be sired not only by their social partner (within-pair mating) but also by other males (extra-pair mating), resulting in broods of mixed paternity. Several hypotheses have been proposed which attempt to explain the adaptive significance of this behavior, including the genetic diversity hypothesis, the good genes hypothesis, the genetic compatibility hypothesis and the fertility insurance hypothesis. I report results of a 5 year population study of the Upland Sandpiper (Bartramia longicauda) at Konza Prairie Biological Station in northeast Kansas. My objective was to determine the genetic mating system of this socially monogamous shorebird, and determine which of the genetic hypotheses best explains the patterns of extra-pair paternity (EPP) in the population. As part of the analysis, I optimized laboratory protocols for genetic sexing of our monomorphic study species. Potential errors in molecular sexing have been previously described but usually result in females being misidentified as males. Here, I report evidence that events in PCR reactions can lead to the opposite error, with males misidentified as females. I recommend the use of multiple primer sets and large samples of known-sex birds for validation when designing protocols for molecular sex analysis. I genotyped birds and tested for the existence of EPP in 58 family groups of Upland Sandpipers. I found 15% of chicks and 30% of broods were the result of extra-pair paternity in this population, which is high in comparison to other socially monogamous shorebirds. Only 2% of chicks and 2% of broods were attended by females unrelated to the young. I tested ecological covariates known to influence EPP in other birds including relatedness of mated pairs, morphology of the within-pair male, and nest initiation date, as well as variables which signify genetic benefits, including morphology of the offspring and offspring heterozygosity, but found no significant relationships. None of the prevailing genetic hypotheses can fully explain the high rates of EPP in this population of Upland Sandpipers. However, the discovery of fine-scale genetic structure in female birds, but not in males, suggests female natal philopatry or malebiased dispersal. This sex-specific genetic structure could be a mechanism of inbreeding avoidance, thereby eliminating the need for females to choose mates based on relatedness. This study provides the first estimates of EPP for the socially monogamous Upland Sandpiper, and provides evidence that the inbreeding avoidance mechanism of engaging in extrapair copulations does not seem to be as important in Upland Sandpipers as in other socially monogamous shorebirds. Future research should include the identification of extra-pair males and the determination of offspring fitness after departure from the nest.

Geographic patterns of song similarity in the Dickcissel (Spiza americana) - Schook, D.M.; Collins, M.D.; Jensen, W.E.; Williams, P.J.; Bader, N.E.; Parker, T.H. (Auk, 2008)
Song sharing among neighboring males is a well-known, frequent outcome of song learning in oscine passerines and some other groups, but only limited investigations of the spatial scale of this phenomenon have been pursued. On the basis of recordings of 1,043 individuals, we investigated song sharing in Dickcissels (Spiza americana) at local and regional scales at sites from northern Kansas to northern Oklahoma. Classification of song elements revealed decreasing song similarity with increasing distances between individual birds at small to intermediate scales, to ~10 km. At the largest spatial scales (10–300 km between sites), there was very little similarity among sites and no obvious tendency for a decrease in similarity with increasing distances among our 30 sites. At our intensively sampled site, analyses of quantitative measurements showed that, at least for our most widely shared song element, frequency and duration were more similar in closer birds. Thus, distance between birds influences both quantitative and qualitative song similarity in Dickcissels. Variability existed among sites in the shape of the song-sharing decay curve, which indicates that other factors besides distance also govern song-sharing patterns. We found high repeatability of individual songs for both second-year (SY) and after-second-year (ASY) males throughout the season, and high conformity to the local song neighborhood in both SY and ASY males from their first recording soon after arrival in May. Returning ASY males sang the same song they had produced the previous breeding season.
Keywords: culture; dialect; Dickcissel; Passeriformes; song sharing; spatial scale; Spiza americana

Grassland establishment under varying resource availability: A test of positive and negative feedback - S.G. Baer; John M. Blair (Ecology, 2008)
The traditional logic of carbon (C) and nitrogen (N) interactions in ecosystems predicts further increases or decreases in productivity (positive feedback) in response to high and low fertility in the soil, respectively; but the potential for development of feedback in ecosystems recovering from disturbance is less well understood. Furthermore, this logic has been challenged in grassland ecosystems where frequent fires or grazing may reduce the contribution of aboveground litter inputs to soil organic matter pools and nutrient supply for plant growth, relative to forest ecosystems. Further, if increases in plant productivity increase soil C content more than soil N content, negative feedback may result from increased microbial demand for N making less available for plant growth. We used a field experiment to test for feedback in an establishing grassland by comparing aboveground net primary productivity (ANPP) and belowground pools and fluxes of C and N in soil with enriched, ambient, and reduced N availability. For eight years annual N enrichment increased ANPP, root N, and root tissue quality, but root C:N ratios remained well above the threshold for net mineralization of N. There was no evidence that N enrichment increased root biomass, soil C or N accrual rates, or storage of C in total, microbial, or mineralizable pools within this time frame. However, the net nitrogen mineralization potential (NMP) rate was greater following eight years of N enrichment, and we attributed this to N saturation of the microbial biomass. Grassland developing under experimentally imposed N limitation through C addition to the soil exhibited ANPP, root biomass and quality, and net NMP rate similar to the ambient soil. Similarity in productivity and roots in the reduced and ambient N treatments was attributed to the potentially high nitrogen-use efficiency (NUE) of the dominant C4 grasses, and increasing cover of legumes over time in the C-amended soil. Thus, in a developing ecosystem, positive feedback between soil N supply and plant productivity may promote enhanced long-term N availability and override progressive N limitation as C accrues in plant and soil pools. However, experimentally imposed reduction in N availability did not feed back to reduce ANPP, possibly due to shifts in NUE and functional group composition.

Headwater influences on downstream water quality - W. K. Dodds; Oakes, R.M. (Environmental Management, 2008)
We investigated the influence of riparian and whole watershed land use as a function of stream size on surface water chemistry and assessed regional variation in these relationships. Sixty-eight watersheds in four level III U.S. EPA ecoregions in eastern Kansas were selected as study sites. Riparian land cover and watershed land use were quantified for the entire watershed, and by Strahler order. Multiple regression analyses using riparian land cover classifications as independent variables explained among-site variation in water chemistry parameters, particularly total nitrogen (41%), nitrate (61%), and total phosphorus (63%) concentrations. Whole watershed land use explained slightly less variance, but riparian and whole watershed land use were so tightly correlated that it was difficult to separate their effects. Water chemistry parameters sampled in downstream reaches were most closely correlated with riparian land cover adjacent to the smallest (first-order) streams of watersheds or land use in the entire watershed, with riparian zones immediately upstream of sampling sites offering less explanatory power as stream size increased. Interestingly, headwater effects were evident even at times when these small streams were unlikely to be flowing. Relationships were similar among ecoregions, indicating that land use characteristics were most responsible for water quality variation among watersheds. These findings suggest that nonpoint pollution control strategies should consider the influence of small upland streams and protection of downstream riparian zones alone is not sufficient to protect water quality.
Keywords: geographic information systems; Headwater streams; Nonpoint source pollution; Riparian zones; water quality; Watershed management

Host-plant quality alters grass/forb consumption by a mixed-feeding insect herbivore, Melanoplus bivittauts (Orthoptera: Acrididae) - Jonas, J.L.; Anthony Joern (Ecological Entomology, 2008)
1. Factors affecting the nutritional ecology of mixed-feeding, polyphagous herbivores are poorly understood. Mixed-feeding herbivores do better when they consume both forb and grass species although they typically feed primarily on forbs, which are of relatively higher protein content than grasses. 2. In a field experiment, we examined the effects of nitrogen and phosphorus fertilization and associated changes in host-plant C:N:P on proportional grass consumption by a mixed-feeding insect herbivore, Melanoplus bivittatus, using natural abundance stable carbon isotope (12C/13C) methods. We also examined a grass-feeding (Phoetaliotes nebrascensis) and forb-feeding (Hesperotettix viridis) species. 3. The C isotope signatures of M. bivittatus collected from plots fertilized with nitrogen (+N), phosphorus (+P), nitrogen and phosphorus (+N+P) and no fertilizer were compared with the C isotope signatures of plants in those plots to determine the proportion of assimilated C derived from C4 grasses and C3 forbs in each plot. We also examined the relationship between M. bivittatus diets and plant C:N:P stoichiometry. 4. The proportion of grass assimilated approximately doubled in N-fertilized treatments (39.1 ± 0.1%) compared with non-fertilized treatments (19 ± <0.1%), an increase associated with decreased C:N and increased N:P of grasses. 5. These results indicate that mixed-feeding M. bivittatus can selectively feed to balance C:N:P intake even when choosing between two structurally and chemically different groups of plants. 6. The strong relationship between diet selection and grass stoichiometry also suggests that plant nutrient composition may be more important than defensive chemistry in food choice.
Keywords: C3 photosynthetic pathway; C4 photosynthetic pathway; Carbon (C); grasshopper; nitrogen (N); optimal foraging; Orthoptera: Acrididae; phosphorus (P); stoichiometry; tallgrass prairie

Humanity's Footprint: Momentum, Impact and our Global Environment - W. K. Dodds (Columbia University Press, 2008)

Increased precipitation event size increases aboveground net primary productivity in a semi-arid grassland - Heisler-White, J.L.; Alan K. Knapp; Kelly, E.F. (Oecologia, 2008)
Water availability is the primary constraint to aboveground net primary productivity (ANPP) in many terrestrial biomes, and it is an ecosystem driver that will be strongly altered by future climate change. Global circulation models predict a shift in precipitation patterns to growing season rainfall events that are larger in size but fewer in number. This “repackaging” of rainfall into large events with long intervening dry intervals could be particularly important in semi-arid grasslands because it is in marked contrast to the frequent but small events that have historically defined this ecosystem. We investigated the effect of more extreme rainfall patterns on ANPP via the use of rainout shelters and paired this experimental manipulation with an investigation of long-term data for ANPP and precipitation. Experimental plots (n = 15) received the long-term (30-year) mean growing season precipitation quantity; however, this amount was distributed as 12, six, or four events applied manually according to seasonal patterns for May–September. The long-term mean (1940–2005) number of rain events in this shortgrass steppe was 14 events, with a minimum of nine events in years of average precipitation. Thus, our experimental treatments pushed this system beyond its recent historical range of variability. Plots receiving fewer, but larger rain events had the highest rates of ANPP (184 ± 38 g m−2), compared to plots receiving more frequent rainfall (105 ± 24 g m−2). ANPP in all experimental plots was greater than long-term mean ANPP for this system (97 g m−2), which may be explained in part by the more even distribution of applied rain events. Soil moisture data indicated that larger events led to greater soil water content and likely permitted moisture penetration to deeper in the soil profile. These results indicate that semi-arid grasslands are capable of responding immediately and substantially to forecast shifts to more extreme precipitation patterns.
Keywords: Climate change; Grasslands; Precipitation variability; Pulse-reserve paradigm; Rain event size

Increasing shallow groundwater CO2 and limestone weathering, Konza Prairie, USA - G. L. Macpherson; Roberts, J.A.; John M. Blair; Townsend, M.A.; Fowle, D.A.; Beisner, K.R. (Geochimica et Cosmochimica Acta, 2008)
In a mid-continental North American grassland, solute concentrations in shallow, limestone-hosted groundwater and adjacent surface water cycle annually and have increased steadily over the 15-year study period, 1991–2005, inclusive. Modeled groundwater CO2, verified by measurements of recent samples, increased from 10−2.05 atm to 10−1.94 atm, about a 20% increase, from 1991 to 2005. The measured groundwater alkalinity and alkaline-earth element concentrations also increased over that time period. We propose that carbonate minerals dissolve in response to lowered pH that occurs during an annual carbonate-mineral saturation cycle. The cycle starts with low saturation during late summer and autumn when dissolved CO2 is high. As dissolved CO2 decreases in the spring and early summer, carbonates become oversaturated, but oversaturation does not exceed the threshold for precipitation. We propose that groundwater is a CO2 sink through weathering of limestone: soil-generated CO2 is transformed to alkalinity through dissolution of calcite or dolomite. The annual cycle and long-term increase in shallow groundwater CO2 is similar to, but greater than, atmospheric CO2.

Influence of grazing and fire frequency on small-scale plant community structure and resource variability in native tallgrass prairie - Veen, G.F.; John M. Blair; M.D. Smith; Scott. L. Collins (Oikos, 2008)
In grasslands worldwide, grazing by ungulates and periodic fires are important forces affecting resource availability and plant community structure. It is not clear, however, whether changes in community structure are the direct effects of the disturbance (i.e. fire and grazing) or are mediated indirectly through changes in resource abundance and availability. In North American tallgrass prairies, fire and grazing often have disparate effects on plant resources and plant diversity, yet, little is known about the individual and interactive effects of fire and grazing on resource variability and how that variability relates to heterogeneity in plant community structure, particularly at small scales. We conducted a field study to determine the interactive effects of different long-term fire regimes (annual vs four-year fire frequency) and grazing by native ungulates (Bos bison) on small-scale plant community structure and resource variability (N and light) in native tallgrass prairie. Grazing enhanced light and nitrogen availability, but did not affect small-scale resource variability. In addition, grazing reduced the dominance of C4 grasses which enhanced species richness, diversity and community heterogeneity. In contrast, annual fire increased community dominance and reduced species richness and diversity, particularly in the absence of grazing, but had no effect on community heterogeneity, resource availability and resource variability. Variability in the abundance of resources showed no relationship with community heterogeneity at the scale measured in this study, however we found a relationship between community dominance and heterogeneity. Therefore, we conclude that grazing generated small-scale community heterogeneity in this mesic grassland by directly affecting plant community dominance, rather than indirectly through changes in resource variability.

Influence of woody vegetation on small mammals in tallgrass prairie - Matlack, R.S.; D.W. Kaufman; Kaufman, G.A. (American Midland Naturalist, 2008)
We examined response of small mammals to woody invasion of tallgrass prairie in northeastern Kansas by sampling sites that ranged from 0 to 100% in woody cover (i.e., frequently burned prairie to unburned closed-canopy gallery forest; woody coverage mapped from satellite imagery). Abundance and biomass of small mammals initially increased with increasing woody vegetation, but then decreased to their lowest level at 100% woody cover. Richness was greatest (an average of seven species) where woody cover was ≤17% and decreased to one species where woody cover was 100%. Abundance of white-footed mice (Peromyscus leucopus) increased as woody cover increased from 0 to 62% cover, but decreased in forested sites (100% cover). Abundance of western harvest mice (Reithrodontomys megalotis) decreased as woody cover increased; they were not recorded in forested sites. Deer mice (P. maniculatus) were present in sites with no to low levels of woody vegetation, but were absent in sites with moderate to high levels of woody cover. The 11 species captured were recorded in sites that had little woody vegetation (≤17% cover), whereas only seven species were captured at sites where considerable woody vegetation (≥28% cover) occurred. Even white-footed mice and eastern woodrats, which are considered woodland forms, decreased in abundance or were absent from forested sites. Overall, the results demonstrate that even relatively small amounts of woody vegetation in prairie landscapes can alter abundance, biomass and species richness and composition of small mammal communities.

Integrating soil ecological knowledge into restoration management - Heneghan, L.; Miller, S.; S.G. Baer; Callaham, M.A.; Montgomery, J.; Rhoades, C.C.; Richardson, S.; Pauvo-Zuckerman, M. (Restoration Ecology, 2008)
The variability in the type of ecosystem degradation and the specificity of restoration goals can challenge restorationists’ ability to generalize about approaches that lead to restoration success. The discipline of soil ecology, which emphasizes both soil organisms and ecosystem processes, has generated a body of knowledge that can be generally useful in improving the outcomes of restoration despite this variability. Here, we propose that the usefulness of this soil ecological knowledge (SEK) for restoration is best considered in the context of the severity of the original perturbation, the goals of the project, and the resilience of the ecosystem to disturbance. A straightforward manipulation of single physical, chemical, or biological components of the soil system can be useful in the restoration of a site, especially when the restoration goal is loosely defined in terms of the species and processes that management seeks to achieve. These single-factor manipulations may in fact produce cascading effects on several ecosystem attributes and can result in unintended recovery trajectories. When complex outcomes are desired, intentional and holistic integration of all aspects of the soil knowledge is necessary. We provide a short roster of examples to illustrate that SEK benefits management and restoration of ecosystems and suggest areas for future research.
Keywords: ecosystem processes; feedbacks; Soil ecology

Lakes and streams as sentinels of environmental change in terrestrial and atmospheric processes - Williamson, C.E.; W. K. Dodds; Kratz, T.K.; Palmer, M. (Frontiers in Ecology and the Environment, 2008)
Recent advances in our understanding of the importance of continental- to global-scale connectivity among terrestrial and aquatic ecosystems make consideration of aquatic–terrestrial linkages an urgent ecological and environmental issue. Here, we describe the role of inland waters as sentinels and integrators of the impact of humans on terrestrial and aquatic ecosystems. The metabolic responses of lakes and streams (ie the rates at which these systems process carbon) are proposed as a common metric to integrate the impacts of environmental change across a broad range of landscapes. Lakes and streams transport and alter nutrients, contaminants, and energy, and store signals of environmental change from local to continental scales over periods ranging from weeks to millennia. A carefully conceived and well-integrated network that includes monitoring and experimental approaches to terrestrial–aquatic connectivity is critical to an understanding of basic ecosystem-level processes and to forecasting and mitigating future environmental impacts at the continental scale.

Life history and production of the riffle beetle, Stenelmis crenata (Say) (Elmidae), in a tallgrass prairie stream - Stagliano, D.M.; M.R. Whiles (Aquatic Insects, 2008)
We examined life history dynamics and estimated production of the riffle beetle, Stenelmis crenata (Say, 1824), in a tallgrass prairie stream. Stenelmis crenata had a univoltine life cycle with larvae present year-round. Recruitment of first instars occurred from June–October, larval growth was synchronised through the winter, pupation occurred in late spring, and adults first appeared in late May. Adults were most abundant (24 individuals/m2) during summer and were present in samples through October. For larval biomass and production estimates, a body length–mass relationship (ash-free dry mass [AFDM] = 0.0079*TL2.7595) was constructed. Mean annual density and biomass of larvae were 235 individuals/m2 and 90.7 mg AFDM/m2, respectively. Annual larval production was 493 mg/m2/y, representing a total of ∼101 g AFDM for the stream reach examined. Production estimates for S. crenata in this stream were high compared to other estimates for elmids, and this species comprised an appreciable portion of total scraper (13.5%) production.
Keywords: aquatic insect; grassland stream; Growth rate; Konza Prairie; life cycle

Limitations to plant diversity and productivity in tallgrass prairie - Schmitt-McCain, K.N. (Kansas State University, 2008)
Approximately 96% of native tallgrass prairie in North America has been lost, which accentuates the need for effective methods to restore the structure and function of these degraded ecosystems. Many prairie restorations aim to restore grass and forb species in proportions reflecting plant species diversity in native prairie. A target grass-forb species mixture is typically chosen at the onset of restoration, but often, grasses become excessively dominant and forbs are underrepresented as the community develops. Several studies have examined the potential for increasing forb cover and diversity in newly restored grasslands, but few studies have assessed factors limiting forb cover and diversity in well-established grass-dominated prairie restorations. The primary objective of this research was to assess the potential for enhancing plant species diversity and productivity in an established grass-dominated prairie restoration by selective removals of dominant grass species, and by manipulating resources (soil nutrients, light availability) or mycorrhizal interactions. A 7-year old grass-dominated restoration was used to evaluate plant and soil responses to manipulations in three separate studies. The first study examined the potential suppressive effects of dominant grasses on plant diversity by reducing the cover and biomass of two dominant grass species, Andropogon gerardii and Panicum virgatum. After 3 years, the removal of A. gerardii increased species richness and diversity, which was correlated with increased light availability, but not changes in soil resources. The second study examined the responses of restored grassland communities to long-term manipulation of soil resources (nutrient availability or soil depth), and to aboveground biomass removal via mowing. The long-term manipulation of soil resources did not alter plant species diversity, but nitrogen and light availability were important factors regulating plant productivity. The third study assessed the effects of manipulating arbuscular mycorrhizal (AM) fungi, through the use of either commercial inoculum or fungicide, on plant communities in restored prairie. Mycorrhizal suppression reduced grass productivity, suggesting that fungicide may be useful for enhancing diversity of restored prairies that are dominated by obligate mycotrophic grasses. In total, these studies suggest that competition between dominant grasses and subordinate forbs limits plant diversity in restored tallgrass prairie.
Keywords: plant diversity; restoration; tallgrass prairie

Long-term response patterns of tallgrass prairie to frequent summer burning - Towne, G.E.; Kemp, K.E. (Rangeland Ecology and Management, 2008)
Knowledge of how tallgrass prairie vegetation responds to fire in the late growing season is relatively sparse and is based upon studies that are either spatially or temporally limited. To gain a more robust perspective of vegetation response to summer burning and to determine if repeated summer fire can drive vegetational changes in native tallgrass prairie, we evaluated species cover and richness over a 14-yr period on different topographic positions from ungrazed watersheds that were burned biennially in the growing season. We found that annual forbs were the primary beneficiaries of summer burning, but their fluctuations varied inconsistently among years. Concomitantly, species richness and diversity increased significantly with summer burning but remained stable through time with annual spring burning. After 14 yr, species richness was 28% higher in prairie that was burned in the summer than in prairie burned in the spring. Canopy cover of big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans [L.] Nash) increased significantly over time with both summer and spring burning, whereas heath aster (Symphyotrichum ericoides [L.] Nesom), aromatic aster (Symphyotrichum oblongifolium [Nutt.] Nesom), and sedges (Carex spp.) increased in response to only summer burning. Kentucky bluegrass (Poa pratensis L.) cover declined in both spring-burned and summer-burned watersheds. Repeated burning in either spring or summer did not reduce the cover or frequency of any woody species. Most perennial species were neutral in their reaction to summer fire, but a few species responded with large and inconsistent temporal fluctuations that overwhelmed any clear patterns of change. Although summer burning did not preferentially encourage spring-flowering forbs or suppress dominance of the warm-season grasses, it is a potentially useful tool to increase community heterogeneity in ungrazed prairie.
Keywords: burn season; fire ecology; grassland vegetation; growing-season fire

Modeled interactive effects of precipitation, temperature, and CO2 on ecosystem carbon and water dynamics in different climatic zones - Luo, Y.; Gerten, D.; Le Maire, G.; Parton, W.J.; Weng, E.; Zhou, X.; Keough, C.; Beier, C.; Ciais, P.; Cramer, W.; Dukes, J.S.; Emmett, B.; et al. (Global Change Biology, 2008)
Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive effects of climate warming (T), altered precipitation amounts [doubled (DP) and halved (HP)] and seasonality (SP, moving precipitation in July and August to January and February to create summer drought), and elevated [CO2] (C) on net primary production (NPP), heterotrophic respiration (Rh), net ecosystem production (NEP), transpiration, and runoff. We examined those responses in seven ecosystems, including forests, grasslands, and heathlands in different climate zones. The modeling analysis showed that none of the three-way interactions among T, C, and altered precipitation was substantial for either carbon or water processes, nor consistent among the seven ecosystems. However, two-way interactive effects on NPP, Rh, and NEP were generally positive (i.e. amplification of one factor's effect by the other factor) between T and C or between T and DP. A negative interaction (i.e. depression of one factor's effect by the other factor) occurred for simulated NPP between T and HP. The interactive effects on runoff were positive between T and HP. Four pairs of two-way interactive effects on plant transpiration were positive and two pairs negative. In addition, wet sites generally had smaller relative changes in NPP, Rh, runoff, and transpiration but larger absolute changes in NEP than dry sites in response to the treatments. The modeling results suggest new hypotheses to be tested in multifactor global change experiments. Likewise, more experimental evidence is needed for the further improvement of ecosystem models in order to adequately simulate complex interactive processes.

Modelled effects of precipitation on ecosystem carbon and water dynamics in different climatic zones - Gerten, D.; Luo, Y.; Le Maire, G.; Parton, W.J.; Keough, C.; Weng, E.; Beier, C.; Ciais, P.; Cramer, W.; Dukes, J.S.; Emmett, B.; Hanson, P.J.; et al. (Global Change Biology, 2008)
The ongoing changes in the global climate expose the world's ecosystems not only to increasing CO2 concentrations and temperatures but also to altered precipitation (P) regimes. Using four well-established process-based ecosystem models (LPJ, DayCent, ORCHIDEE, TECO), we explored effects of potential P changes on water limitation and net primary production (NPP) in seven terrestrial ecosystems with distinctive vegetation types in different hydroclimatic zones. We found that NPP responses to P changes differed not only among sites but also within a year at a given site. The magnitudes of NPP change were basically determined by the degree of ecosystem water limitation, which was quantified here using the ratio between atmospheric transpirational demand and soil water supply. Humid sites and/or periods were least responsive to any change in P as compared with moderately humid or dry sites/periods. We also found that NPP responded more strongly to doubling or halving of P amount and a seasonal shift in P occurrence than that to altered P frequency and intensity at constant annual amounts. The findings were highly robust across the four models especially in terms of the direction of changes and largely consistent with earlier P manipulation experiments and modelling results. Overall, this study underscores the widespread importance of P as a driver of change in ecosystems, although the ultimate response of a particular site will depend on the detailed nature and seasonal timing of P change.

Phenotypic correlates and survival consequences of male mating success in lek-mating Greater Prairie-chickens (Tympanuchus cupido) - Nooker, J.K.; Sandercock, B.K. (Behavioral Ecology and Sociobiology, 2008)
Female choice and male–male aggression are two modes of sexual selection that can lead to elaboration of male morphological and behavioral traits. In lek-mating species, male mating success is often strongly skewed, and it is puzzling why variation in male traits is still observed given directional female choice. If male traits correlated with reproductive success are honest signals of male quality, there may be survival costs associated with the expression of those traits. In this study, we examined whether morphological, behavioral, and territorial traits are correlated with male mating success and survival in the lek-mating greater prairie-chicken (Tympanuchus cupido). We introduce a novel application of multinomial discrete choice models for analysis of female mate choice behavior. We found that behavioral and territorial attributes showed 6.5 times more variability among males than morphological traits. Both display and aggressive behaviors were strong predictors of male mating success, suggesting that both female choice and male–male aggression were important in determining mating success among male greater prairie-chickens. Moreover, annual survival of male prairie-chickens was independent of mating success and male traits. Females appear to be choosing males based on behavioral traits where large variation exists between males (coefficient of variation >30%). Behavioral traits were the most important factor in determining mating success of male prairie-chickens, but the mechanism underlying this relationship is unknown. In the future, experimental manipulations of male hormones or parasite loads could bridge the proximate mechanisms and ultimate consequences of factors mediating male mating success in lek-mating grouse.
Keywords: Galliformes; Life history trade-off; mate choice; reproduction; Sexual selection

Plant winners and losers during grassland N eutrophication differ in biomass allocation and mycorrhizas - Johnson, N.C.; Rowland, D.L.; Corkidi, L.; Allen, E.B. (Ecology, 2008)
Human activities release tremendous amounts of nitrogenous compounds into the atmosphere. Wet and dry deposition distributes this airborne nitrogen (N) on otherwise pristine ecosystems. This eutrophication process significantly alters the species composition of native grasslands; generally a few nitrophilic plant species become dominant while many other species disappear. The functional equilibrium model predicts that, compared to species that decline in response to N enrichment, nitrophilic grass species should respond to N enrichment with greater biomass allocation aboveground and reduced allocation to roots and mycorrhizas. The mycorrhizal feedback hypothesis states that the composition of mycorrhizal fungal communities may influence the composition of plant communities, and it predicts that N enrichment may generate reciprocal shifts in the species composition of mycorrhizal fungi and plants. We tested these hypotheses with experiments that compared biomass allocation and mycorrhizal function of four grass ecotypes (three species), two that gained and two that lost biomass and cover in response to long-term N enrichment experiments at Cedar Creek and Konza Long-Term Ecological Research grasslands. Local grass ecotypes were grown in soil from their respective sites and inoculated with whole-soil inoculum collected from either fertilized (FERT) or unfertilized (UNFERT) plots. Our results strongly support the functional equilibrium model. In both grassland systems the nitrophilic grass species grew taller, allocated more biomass to shoots than to roots, and formed fewer mycorrhizas compared to the grass species that it replaced. Our results did not fully support the hypothesis that N-induced changes in the mycorrhizal fungal community were drivers of the plant community shifts that accompany N eutrophication. The FERT and UNFERT soil inoculum influenced the growth of the grasses differently, but this varied with site and grass ecotype in both expected and unexpected ways suggesting that ambient soil fertility or other factors may be interacting with mycorrhizal feedbacks.

Plasma cholinesterases for monitoring pesticide exposure in Nearctic-Neotropical migratory shorebirds - Strum, K.M.; Alfaro, M.; Haase, B.; Hooper, M.J.; Johnson, K.A.; Lanctot, R.B.; Lesterhuis, A.J.; López, L.; Matz, A.C.; Morales, C.; Paulson, B.; Sandercock, B.K.; et al. (Ornithología Neotropical, 2008)
Organophosphorus (OP) and carbamate (CB) pesticides are commonly used agrochemicals throughout the Western Hemisphere. These pesticides have caused mortalities in migratory birds and adverse physiological effects in trials with captive birds. Migratory shorebirds use a variety, of habitats during the austral summer in temperate South America and during migration through the Great Plains of the United States. Habitats where risk of exposure is high include rice fields and turf grass farms where agrochemicals are used. Cholinesterase (ChE) is a specific biomarker for monitoring OP and CB exposure and can be measured using standard laboratory procedures. Plasma ChE activity is useful as a non-lethal means of monitoring avian exposure to OP and CB pesticides. Many variables can affect enzyme activity and reactivation assays are not always possible, thus reference ChE values are a necessary component of monitoring exposure. During northbound migration in 2006, we sampled four upland and five wetland shore-bird species at four pesticide-free sites in North America, characterizing and measuring plasma ChEs in all shorebird species. Small-bodied species had higher levels of ChE activity in plasma than large-bodied species. Acetylcholinesterase (AChE), the enzyme whose inhibition leads to poisoning symptoms, showed less inter-specific variation than butyrylcholinesterase (BChE). Plasma ChE activities varied with date of capture in three of five species. Sex differences were significant in one of two species tested. Our baseline ChE values for migratory shorebirds provide a framework for future ecotoxicological studies of Nearctic-Neotropical migrant shorebirds.

Predicting and understanding ecosystem responses to climate change at continental scales - Marshall, J.D.; John M. Blair; Peters, D.P.C.; Okin, G.; Rango, A.; Williams, M. (Frontiers in Ecology and the Environment, 2008)
Climate is changing across a range of scales, from local to global, but ecological consequences remain difficult to understand and predict. Such projections are complicated by change in the connectivity of resources, particularly water, nutrients, and propagules, that influences the way ecological responses scale from local to regional and from regional to continental. This paper describes ecological responses to expected changes in four key meso-scale drivers that influence the ecosystems of the North American continental interior: drought, warming, snowpack disappearance, and altered fire regimes. Changes in these drivers will affect, for example, atmospheric smoke, dust, and reactive nitrogen concentrations; stream discharge; nitrate concentrations; sediment loads; and the vector-borne spread of invasive species and infectious diseases. A continental network of sensors and simulation models is required to detect changes in the transport vectors – atmospheric, hydrologic, and mechanized –that connect spatial scales. Knowledge of these downwind, downstream, and down-corridor effects will be critical if we are to understand and forecast responses to climate change at regional to continental scales.

Predicting NH4+ uptake andmineralization in prairie streams by using chamber incubation and short-termnutrient addition experiments - O'Brien, J.M.; W. K. Dodds (Freshwater Biology, 2008)

Rank clocks and plant community dynamics - Scott. L. Collins; K.N. Suding; Cleland, E.E.; Batty, M.; Pennings, S.C.; Gross, K.L.; Grace, J.S.; Gough, L.; Fargione, J.E.; Clark, C.M. (Ecology, 2008)
Summarizing complex temporal dynamics in communities is difficult to achieve in a way that yields an intuitive picture of change. Rank clocks and rank abundance statistics provide a graphical and analytical framework for displaying and quantifying community dynamics. We used rank clocks, in which the rank order abundance for each species is plotted over time in temporal clockwise direction, to display temporal changes in species abundances and richness. We used mean rank shift and proportional species persistence to quantify changes in community structure in long-term data sets from fertilized and control plots in a late successional old field, frequently and infrequently burned tallgrass prairie, and Chihuahuan desert grassland and shrubland communities. Rank clocks showed that relatively constant species richness masks considerable temporal dynamics in relative species abundances. In the old field, fertilized plots initially experienced high mean rank shifts that stabilized rapidly below that of unfertilized plots. Rank shifts were higher in infrequently burned vs. annually burned tallgrass prairie and in desert grassland compared to shrubland vegetation. Proportional persistence showed that arid grasslands were more dynamic than mesic grasslands. We conclude that rank clocks and rank abundance statistics provide important insights into community dynamics that are often hidden by traditional univariate approaches.

Reovirus associated with mortality of an Upland Sandpiper - Sandercock, B.K.; Casey, A.E.; Green, D.E.; Ip, H.S.; Converse, K.A. (Wader Study GroupBulletin, 2008)

Responses of breeding birds in tallgrass prairie to fire and cattle grazing - Powell, A.F.L.A. (Journal of Field Ornithology, 2008)
No other group of North American birds has declined as precipitously and over so large an area as has the grassland assemblage. In the Flint Hills of Kansas, the largest extant region of tallgrass prairie, annual spring burning of rangeland has largely replaced traditional regimes and natural patterns with longer intervals between burns. I examined effects of burning and low-intensity cattle grazing on abundances of seven bird species at Konza Prairie Research Natural Area in June 2002 and 2003. Every species was affected by fire, with Upland Sandpipers (Bartramia longicauda) more abundant, and six species—Grasshopper Sparrow (Ammodramus savannarum), Henslow's Sparrow (A. henslowii), Dickcissel (Spiza americana), Eastern Meadowlark (Sturnella magna), Brown-headed Cowbird (Molothrus ater), and Bell's Vireo (Vireo bellii)—either less abundant or absent at sites in the breeding season following a fire. These results demonstrate that annual burning limits the potential of much of the Flint Hills prairie to harbor high breeding densities of many grassland birds. On the other hand, I found a trade-off between immediate and longer-term effects of burning for several grass-dependent species. Grasshopper Sparrows, Henslow's Sparrows, and Eastern Meadowlarks, although more numerous in areas that were not burned the preceding spring, were less abundant at sites burned every 4 yrs than those burned at shorter intervals. In contrast, shrub-dependent Bell's Vireos were more abundant at sites burned every 4 yrs. Upland Sandpipers, Grasshopper Sparrows, and Eastern Meadowlarks were more abundant in grazed areas. Use of alternatives to annual burning could increase habitat heterogeneity by transforming the Flint Hills into a mosaic of regularly, but asynchronously, burned pastures that would better meet the diverse habitat needs of the region's grassland birds.

Responses of two bunchgrasses to nitrogen addition in tallgrass prairie: the role of bud bank demography - Dalgleish, H.J.; Kula, A.R.; D.C. Hartnett; Sandercock, B.K. (American Journal of Botany, 2008)
Growth of tallgrass prairie plants, many of which maintain substantial bud banks, can be limited by nitrogen (N), water, and/or light. We hypothesized that tallgrass prairie plants respond to increases in N through demographic effects on the bud bank. We tested the effects of a pulse of N on (1) bud bank demography, (2) plant reproductive allocation, and (3) ramet size. We parameterized matrix models, considering each genet as a population of plant parts. Nitrogen addition significantly impacted bud bank demography in two subdominant species of bunchgrass: Sporobolus heterolepis (a C4 grass) and Koeleria macrantha (a C3 grass), but had no effect on the size of individual ramets. Emergence from the bud bank and ramet population growth rates (λ) were significantly higher in S. heterolepis genets that received supplemental N. Nitrogen addition also affected the bud demography of K. macrantha, but N addition decreased rather than increased λ. Prospective and retrospective demographic analyses indicated that bud bank dynamics were the most important demographic processes driving plant responses to nutrient availability. Thus, the variation in productivity in these tallgrass prairie species is driven principally by the demography of the bud bank rather than by the physiology and growth of aboveground tillers. Improved understanding of bud bank dynamics may lead to improved predictive models of grassland responses to environmental changes such as altered N deposition and precipitation.
Keywords: kansas; Koeleria macrantha; Konza Prairie Long-Term Ecological Research Site; Meristem; Poaceae; Sporobolus heterolepis

Scale-dependent responses of plant biodiversity to nitrogen enrichment - Chalcraft, D.R.; Cox, S.B.; Clark, C.M.; E.E Cleland; K.N. Suding; Weiher, E.; Pennington, D. (Ecology, 2008)
Experimental studies demonstrating that nitrogen (N) enrichment reduces plant diversity within individual plots have led to the conclusion that anthropogenic N enrichment is a threat to global biodiversity. These conclusions overlook the influence of spatial scale, however, as N enrichment may alter β diversity (i.e., how similar plots are in their species composition), which would likely alter the degree to which N-induced changes in diversity within localities translate to changes in diversity at larger scales that are relevant to policy and management. Currently, it is unclear how N enrichment affects biodiversity at scales larger than a small plot. We synthesized data from 18 N-enrichment experiments across North America to examine the effects of N enrichment on plant species diversity at three spatial scales: small (within plots), intermediate (among plots), and large (within and among plots). We found that N enrichment reduced plant diversity within plots by an average of 25% (ranging from a reduction of 61% to an increase of 5%) and frequently enhanced β diversity. The extent to which N enrichment altered β diversity, however, varied substantially among sites (from a 22% increase to an 18% reduction) and was contingent on site productivity. Specifically, N enrichment enhanced β diversity at low-productivity sites but reduced β diversity at high-productivity sites. N-induced changes in β diversity generally reduced the extent of species loss at larger scales to an average of 22% (ranging from a reduction of 54% to an increase of 18%). Our results demonstrate that N enrichment often reduces biodiversity at both local and regional scales, but that a focus on the effects of N enrichment on biodiversity at small spatial scales may often overestimate (and sometimes underestimate) declines in regional biodiversity by failing to recognize the effects of N on β diversity.

Seasonal and temporal dynamics of arbuscular mycorrhizal and dark septate endophytic fungi in a tallgrass prairie ecosystem are minimally affected by nitrogen enrichment - Mandyam, K.G.; A. Jumpponen (Mycorrhiza, 2008)
Root colonization by arbuscular mycorrhizae (AM) and dark septate endophytic (DSE) fungi in nitrogen amended and unamended mixed tallgrass prairie communities were analyzed monthly over two growing seasons. Roots were stained with Trypan blue and Sudan IV and fungal structures quantified using the modified magnified intersections method. Root length colonized (RLC) by DSE exceeded AM colonization during early part of the growing season. Fungal colonization varied among the years and was greater in 2003 than in 2002. Seasonal variation among the months within a growing season was observed in 2002 but not in 2003 for both AM and DSE. AM fungi were most abundant during the peak growing season of dominant C4 vegetation while DSE were most abundant during the early part of the growing season. Hyperparasitism of AM hyphal coils by melanized septate fungi was frequently observed and increased with AM coil frequency. Although nitrogen amendment had altered the plant community composition, it had no impact on the colonization by AM or DSE fungi.
Keywords: Arbsucular mycorrhiza (AM); Dark septate endophytes (DSE); Hyperparasitism; Nitrogen amendment

Sensitivity of grassland ecosystemsacross the Great Plains to present and future variability - Heisler, J.L. (Colorado State University, 2008)
Patterns and controls of aboveground net primary productivity (ANPP) have been of long-standing interest to ecologists because ANPP integrates key aspects of ecosystem structure and function through time. In many terrestrial biomes, water availability is a primary constraint to ANPP, and it is an ecosystem driver that will be affected by future climate change. To understand the sensitivity of temperate grasslands to inter- and intra-annual variability in precipitation, I analyzed long-term ANPP data, conducted a multi-site experimental manipulation in which the number of growing season rainfall events was varied, and simulated the effects of altered rainfall regimes using a terrestrial ecosystem model (DAYCENT). I conducted this research within the Great Plains of North America—a region characterized by a strong west-east precipitation-productivity gradient and three distinct grassland types—the semi-arid shortgrass, the mixed-grass prairie, and the mesic tallgrass prairie. My results demonstrate that temperate grasslands are indeed sensitive to both inter- and intra-variability in precipitation, but the ANPP response is contingent upon ecosystem structure and typical soil water levels. Additionally, both management strategies and topographic location may interact with precipitation to enhance or diminish coherence in the ANPP response. At the dry end of the gradient (semi-arid steppe), fewer, but larger rain events led to increased periods of above-average soil water content, reduced plant water stress and increased ANPP. The opposite response was observed at the mesic end of the gradient (tallgrass prairie), where longer dry intervals between large events led to extended periods of below-average soil water content, increased plant water stress, and reduced ANPP. Mixed grass prairie was intermediate along the gradient, characterized by the greatest plant species richness, and the most sensitive to within-season variability in rainfall. Comparison of these experimental data to model simulations revealed key differences in soil water dynamics and ANPP patterns, suggesting that more experimental data is needed to parameterize biological and physical processes that drive model simulations. In conclusion, these results highlight the difficulties in extending inference from single site experiments to whole ecosystems or biomes and demonstrate the complexity inherent in predicting how terrestrial ecosystems will respond to novel climate conditions.

Shrub encroachment in North American grasslands: Shifts in growth form dominance rapidly alters control of ecosystem carbon inputs - Alan K. Knapp; J. M. Briggs; Scott. L. Collins; S.R. Archer; Bret-Harte, M.S.; Ewers, B.E.; Peters, D.P.; Young, D.R.; Shaver, G.R.; Pendall, E.; Cleary, M.B. (Global Change Biology, 2008)
Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to Atlantic coastal dunes, to quantify patterns and controls of C inputs via aboveground net primary production (ANPP). Across a fourfold range in mean annual precipitation (MAP), a key regulator of ecosystem C input at the continental scale, shrub invasion decreased ANPP in xeric sites, but dramatically increased ANPP (>1000 g m−2) at high MAP, where shrub patches maintained extraordinarily high leaf area. Concurrently, the relationship between MAP and ANPP shifted from being nonlinear in grasslands to linear in shrublands. Thus, relatively abrupt (<50 years) shifts in growth form dominance, without changes in resource quantity, can fundamentally alter continental-scale pattern of C inputs and their control by MAP in ways that exceed the direct effects of climate change alone.

Species responses to nitrogen fertilization in herbaceous plant communities, and associated species traits - Cleland, E.E.; Clark, C.M.; Scott. L. Collins; Fargione, J.E.; Gough, L.; Gross, K.L.; Pennings, S.C.; W.D. Bowman; Robertson, G.P.; Simpson, J.; Tilman, D.; K.N. Suding (Ecology, 2008)
This synthetic data set contains plant species relative abundance measures from 35 nitrogen (N) fertilization experiments conducted at 10 sites across North America. The data set encompasses the fertilization responses of 575 taxa from 1159 experimental plots. The methodology varied among experiments, in particular with regard to the type and amount of N added, plot size, species composition measure (biomass harvest, pin count, or percent cover), additional experimental manipulations, and experimental duration. At each site, each species has been classified according to a number of easily identified categorical functional traits, including life history, life form, the number of cotyledons, height relative to the canopy, potential for clonal growth, and nativity to the United States. Additional data are available for many sites, indicated by references to publications and web sites. Analyses of these data have shown that N enrichment significantly alters community composition in ways that are predictable on the basis of plant functional traits as well as environmental context. This data set could be used to answer a variety of questions about how plant community composition and structure respond to environmental changes.

Stable isotopes identify the natal origins of a generalist brood parasite, the brown‐headed cowbird Molothrus ater - Kosciuch, K.L.; Rivers, J.W.; Sandercock, B.K. (Journal of AvianBiology, 2008)
Identifying the natal origins of brood parasites is a major challenge that usually requires labor-intensive searching for nests of host species. Stable isotope analysis of feathers and other body tissues of parasitic young could be a possible tool for determining natal origins if tissues reflect the isotopic composition of the diet fed to nestlings. We measured the carbon (13C) and nitrogen (15N) isotope compositions of feathers for two age-classes of brown-headed cowbirds Molothrus ater at the Konza Prairie Biological Station near Manhattan, Kansas: nestlings raised by five species of songbird hosts in two different habitats, and juveniles captured after independence. Isotope values from cowbird nestlings did not differ among host species and we were unable to assign juvenile cowbirds to their natal hosts. However, nestlings raised in grassland habitat had feathers that contained significantly higher δ13C values and lower δ15N values than nestlings raised in shrub habitats. In addition, independent juveniles had isotopic signatures that were similar to cowbird nestlings raised on shrub habitats. Although dickcissel Spiza americana comprised the majority of samples from shrub habitats, our conclusions reflect the natural pattern of parasitism at the site and should be representative of cowbirds raised at Konza. We conclude that stable isotope analysis of feathers is effective for determining the natal origins of parasitic young if isotope values from nestlings are isotopically distinct among habitats.

Stream denitrification across biomes and its response to anthropogenic nitrate loading - Mulholland, P.J.; Helton, A.M.; Poole, G.C.; Hall, R.O. Jr.; Hamilton, S.K.; Peterson, B.J.; Tank, J.L.; L.R. Ashkenas; Cooper, L.W.; Dahm, C.N.; W. K. Dodds; Findlay, S.E.G.; et al. (Nature, 2008)
Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing1, 2 and terrestrial ecosystems are becoming increasingly nitrogen-saturated3, causing more bioavailable nitrogen to enter groundwater and surface waters4, 5, 6. Large-scale nitrogen budgets show that an average of about 20–25 per cent of the nitrogen added to the biosphere is exported from rivers to the ocean or inland basins7, 8, indicating that substantial sinks for nitrogen must exist in the landscape9. Streams and rivers may themselves be important sinks for bioavailable nitrogen owing to their hydrological connections with terrestrial systems, high rates of biological activity, and streambed sediment environments that favour microbial denitrification6, 10, 11. Here we present data from nitrogen stable isotope tracer experiments across 72 streams and 8 regions representing several biomes. We show that total biotic uptake and denitrification of nitrate increase with stream nitrate concentration, but that the efficiency of biotic uptake and denitrification declines as concentration increases, reducing the proportion of in-stream nitrate that is removed from transport. Our data suggest that the total uptake of nitrate is related to ecosystem photosynthesis and that denitrification is related to ecosystem respiration. In addition, we use a stream network model to demonstrate that excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate that is exported to receiving waters and reduces the relative role of small versus large streams as nitrate sinks.

Systematics and reproductive biology of Morus L. (Moraceae) - Nepal, M.P. (Kansas State University, 2008)
Morus L. (Moraceae) is a temperate and subtropical genus of ten to 15 species distributed in Asia, Africa, Europe, North, Central and South America. Despite its broad distribution and economic importance, it has received little attention from systematic botanists. Two species of this genus, the native M. rubra and the exotic M. alba, co-occur in eastern North America including the Flint Hills region of the Central Plains. In my dissertation research, I have conducted both species level and population level studies to obtain insights into the diversification of Morus. At the species level, my objectives were to re-evaluate the taxonomy and reconstruct the phylogeny of Morus. Based on herbarium and literature study as well as some field study, I recognize 13 species: eight species occurring in Asia, one in Africa and four in the New World. I used sequence data from the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA and the trnL-trnF region of the chloroplast DNA to reconstruct the evolutionary history of Morus. The phylogenies were congruent and indicate a) a monophyletic core group of Morus with two well-supported geographical clades (one containing Asian taxa and one of New World taxa); and b) that Morus, as currently circumscribed, is non-monophyletic. At the population level, I studied sex expression pattern variation between the Morus native-exotic pair in the Flint Hills region, and assessed hybridization between these species at Konza Prairie Biological Station (KPBS). Both species are subdioecious, and Flint Hills populations exhibit significantly male-biased sex ratios, with sex expression being size independent. Approximately 10% of individuals of each species changed sex annually. In the population study at KPBS, I applied randomly amplified polymorphic DNA (RAPD) markers and microsatellites. The Morus species were moderately ([Theta]II = 0.079; RAPD data) to highly differentiated genetically (F[subscript]ST = 0.233; microsatellite data). Analysis of genetic structure suggested interspecific gene flow and indicated the presence of later generation hybrids. The presence of the exotic congener may affect the existence and genetic integrity of the native species. Overall, these studies contribute to our understanding of diversity in this interesting plant study system.
Keywords: Interspecific hybridization; Microsatellites; Moraceae; Morus taxonomy; phylogeny; subdioecy

Temporal coherence of aboveground net primary productivity in mesic grasslands - Heisler, J.L.; Alan K. Knapp (Ecography, 2008)
Synchrony in ecological variables over wide geographic areas suggests that large-scale environmental factors drive the structure and function of ecosystems and override more local-scale environmental variation. Described also as coherence, this phenomenon has been documented broadly in the ecological literature and has recently received increasing attention as scientists attempt to quantify the impacts of global changes on organisms and their habitats. Using a mesic grassland site in North America, we assessed coherence in ecosystem function by quantifying similarity in aboveground net primary production (ANPP) dynamics in 48 permanent sampling locations (PSLs) over a 16-yr period. Our primary objective was to characterize coherence across a broad geographic region (with similar ecosystem structure and function), and we hypothesized that precipitation and a similar fire frequency would strengthen coherence between PSLs. All 48 PSLs at our site (Konza Prairie Biological Station, Manhattan, KS, USA; KPBS) were exposed to a similar regional driver of ANPP (precipitation); however, local drivers (including differences in fire frequency and soil depth at different topographic positions) varied strongly among individual PSLs. For the purpose of this assessment, the watershed-level experimental design of KPBS was considered a model, which represented different fire management strategies across the Great Plains Region. Our analyses revealed a site-level (KPBS) coherence in ANPP dynamics of 0.53 for the period of 1984–1999. Annual fire enhanced coherence among PSLs to 0.76, whereas less frequent fire (fire exclusion or a 4-yr fire return interval) failed to further increase coherence beyond that of the KPBS site level. Soil depth also strongly influenced coherence among PSLs with shallow soils at upland sites showing strong coherence across fire regimes and annually burned uplands closely linked to annual precipitation dynamics. The lack of coherence in ecosystem function in PSLs with deep soils and low fire frequencies suggests that conservation and management efforts will need to be more location specific in such areas where biotic interactions may be more important than regional abiotic drivers.

Topsin-M: the new benomyl for mycorrhizal-suppression experiments - G.T. Wilson; Williamson, M.M. (Mycologia, 2008)
The fungicide benomyl was the most commonly used biocide for both field and greenhouse experiments in which arbuscular mycorrhizal fungal (AMF) suppression is desired. Unfortunately benomyl is no longer manufactured and therefore is not available for experimental use and no fungicide has been proposed as a successful alternative for experimentally suppressing mycorrhizal fungi. In this study we examined the potential for the fungicide Topsin M® (topsin) to suppress mycorrhizal symbiosis in both field and greenhouse experiments. Topsin reduced AMF colonization of the obligately mycotrophic, warm-season grass Andropogon gerardii with a large and significant reduction in plant biomass production. Topsin reduced AMF colonization of the facultatively mycotrophic, cool-season grass Pascopyron smithii but did not significantly reduce biomass production. Fertilization with nitrogen and phosphorus was able to compensate for reductions in biomass due to the application of fungicide because biomass production of plants that received topsin fungicide was not significantly different from fertilized controls not receiving topsin. While we are not advocating that topsin fungicide is a universal mechanism for mycorrhizal-suppressed controls, in systems where benomyl was found to be successful topsin appears to be a useful, available and successful alternative.

Woody plant encroachment by Juniperus virginiana in a mesic native grassland promotes rapid carbon and nitrogen accrual - McKinley, D.C.; John M. Blair (Ecosystems, 2008)
The cover and abundance of Juniperus virginiana L. in the U.S. Central Plains are rapidly increasing, largely as a result of changing land-use practices that alter fire regimes in native grassland communities. Little is known about how conversion of native grasslands to Juniperus-dominated forests alters soil nutrient availability and ecosystem storage of carbon (C) and nitrogen (N), although such land-cover changes have important implications for local ecosystem dynamics, as well as regional C and N budgets. Four replicate native grasslands and adjacent areas of recent J. virginiana encroachment were selected to assess potential changes in soil N availability, leaf-level photosynthesis, and major ecosystem C and N pools. Net N mineralization rates were assessed in situ over two years, and changes in labile soil organic pools (potential C and N mineralization rates and microbial biomass C and N) were determined. Photosynthetic nitrogen use efficiencies (PNUE) were used to examine differences in instantaneous leaf-level N use in C uptake. Comparisons of ecosystem C and N stocks revealed significant C and N accrual in both plant biomass and soils in these newly established forests, without changes in labile soil N pools. There were few differences in monthly in situ net N mineralization rates, although cumulative annual net N mineralization was greater in forest soils compared to grasslands. Conversely, potential C mineralization was significantly reduced in forest soils. Encroachment by J. virginiana into grasslands results in rapid accretion of ecosystem C and N in plant and soil pools with little apparent change in N availability. Widespread increases in the cover of woody plants, like J. virginiana, in areas formerly dominated by graminoid species suggest an increasing role of expanding woodlands and forests as regional C sinks in the central U.S.
Keywords: carbon storage; grassland conversion; invasion; Juniperus virginiana; land cover change; Mineralization; Nitrogen cycling; Nitrogen use efficiency; woody plant encroachment

Altered ecosystem nitrogen dynamics as a consequence of land cover change in tallgrass prairie - Norris, M.D.; John M. Blair; Johnson, L.C. (American Midland Naturalist, 2007)
In recent decades, substantial areas of North American tallgrass prairie have been lost to the establishment and expansion of woodlands and forests, including those dominated by eastern redcedar (Juniperus virginiana). This shift in dominant plant life form, from C4 grasses to coniferous trees, may be accompanied by changes in productivity, standing stocks of biomass and nutrients and biogeochemical cycles. The goal of this study was to quantify and compare major pools and fluxes of nitrogen in recently established (≤ 80 y) redcedar forests and adjacent native grasslands. Three former grassland sites in the Flint Hills region of Kansas that developed closed-canopy redcedar forests in the recent past were paired with adjacent grassland sites on similar soil type and topographic position (n  =  3 sites/land cover type), and selected soil and plant nitrogen pools and fluxes were measured in replicate plots (n  =  6/site) along transects in each forest or grassland site over a 20-mo period. We found few significant differences in median soil inorganic N pools or net N mineralization rates between the forest and grassland sites, though there was a trend for greater concentrations of inorganic N in grassland sites on most sample dates, and cumulative growing season net N mineralization averaged 15% less in forest sites (14.3 kg N·ha−1·yr−1) than in grassland sites (16.9 kg N·ha−1·yr−1). Mean aboveground plant productivity of forest sites (9162 kg ha−1 yr−1) was about 2.5× greater than that of comparable grasslands (similar soils and topographic position), in spite of similar levels of soil N availability. This resulted in an ecosystem-level nitrogen use efficiency (ANPP∶litterfall N) in forests that was more than double that of the grasslands they replaced. Additional changes in N cycling associated with redcedar forest development included large accumulations of N in aboveground biomass and transfer to the forest floor via litterfall; redcedar aboveground biomass contained 617 kg N/ha, forest floor litter N was 253 kg N/ha, and litterfall N flux was 41 kg ha−1·yr−1. These are substantial increases in aboveground biomass N accumulation, surface litter N inputs, and surface litter N accumulation compared to the native grasslands characteristic of this region. These fundamental shifts in ecosystem patterns and processes have the potential to alter regional biogeochemistry and both nitrogen and carbon storage throughout areas of the eastern Central Plains where coverage of redcedars is increasing.

Belowground bud banks as regulators of grassland dynamics - Dalgleish, H.J. (Kansas State University, 2007)
In perennial grasslands, the belowground population of meristems (the bud bank) plays a fundamental role in local plant population structure and dynamics. I tested the “meristem limitation hypothesis” prediction that bud banks increase along an increasing precipitation/productivity gradient in North American grasslands. I sampled bud populations quarterly at six sites across a 1,100 km gradient in central North America. Bud banks increased with average annual precipitation, which explained 80% of variability in bud banks among sites. Seasonal changes in grass bud banks were surprisingly similar across a 2.5-fold range in precipitation and a 4-fold range of aboveground net primary productivity (ANPP). Secondly, I tested the hypothesis that tallgrass prairie plants respond to increases in a limiting resource (nitrogen) through demographic effects on the bud bank. I parameterized matrix models for individual genets, considering each genet as a population of plant parts (buds and stems). Nitrogen addition significantly impacted bud bank demography of both Sporobolus heterolepis and Koeleria macrantha. In 2005, emergence from the bud bank and growth rates (λ) of the tiller population were significantly higher in S. heterolepis genets that received nitrogen. In contrast, nitrogen addition decreased λ in K. macrantha. Both prospective and retrospective analyses indicated that bud bank dynamics are the key demographic processes driving genet responses to nutrient availability. Lastly, I tested the hypothesis that the effects of fire and grazing on plant species composition and ANPP are mediated principally through demographic effects on bud banks. I found that plants respond to fire and grazing with altered rates of belowground bud natality, bud emergence, and both short-term (fire cycle) and long-term changes in bud density. The size of the bud bank is an excellent predictor of long-term ANPP, supporting my hypothesis that ANPP is strongly regulated by belowground demographic processes. Meristem limitation due to water or nutrient availability or management practices such as fire and grazing may constrain grassland responses to inter-annual changes in resource availability. An important consequence is that grasslands with a large bud bank may be the most responsive to future climatic change or other phenomena such as nutrient enrichment, and may be most resistant to exotic species invasions.
Keywords: Bud bank; grassland; plant ecology; population biology

Carbon isotope variation in modern soils of the tallgrass prairie:Analogues for the interpretation of isotopicrecords derived from paleosols - Johnson, W.C.; Willey, K.L.; G. L. Macpherson (Quaternary International, 2007)
Use of stable carbon isotope data from paleosols to reconstruct past plant community structure (C3 vs. C4) has become commonplace. In an effort to improve our ability to make isotope-based reconstructions and to better appreciate the pitfalls, investigations were conducted on both modern soils and paleosols in the Kansas grasslands. Stable carbon isotope data were derived from soils and vegetation on the near-pristine, C4-dominated grassland of the Konza Tallgrass Prairie Long-Term Ecological Research (LTER) site in northeastern Kansas. In order to evaluate variation of δ13C within the landscape, two levels of sampling were employed: 2 m-deep upland cores extracted to assess variation with depth in the soil profile, and, to assess variability across the landscape, surface samples along two transects and from within a 660×690 m grid. For transect and grid points, both the upper 2 cm of sediment and the aboveground biomass were collected. Core samples taken at Konza reveal that soil organic carbon was depleted in 13C within the upper 10–20 cm relative to the remainder of the soil solum below, a phenomenon previously reported. In transects and the sample grid, soil organic carbon from soil surfaces was consistently more depleted in 13C than aboveground tissue of associated vegetation samples. Slope, azimuth, and insolation were computed from field data and a high-resolution DEM of the sample grid, but these variables offered no significant explanation of the spatial variability in δ13C data from soil organic carbon. The observation that modern landscape position has little effect on δ13C over short distances, at least in a C4-dominated community, lends support to the application of δ13C analysis to buried soils for paleoenvironmental reconstruction where paleolandscape position is often unknown. Stable carbon isotope data were derived from paleosols at from the Beisel-Steinle site located to the west of Konza in central Kansas. Three soils were examined: the interstadial paleosol within the Gilman Canyon Formation (c. 38–27k cal yr BP), the Late Pleistocene–Holocene Brady Soil, and the modern surface soil. With the exception of isotopic depletion at the top of the surface soil, all three soils exhibited similar δ13C values of about14‰, the same value realized in the soil cores from Konza, suggesting close similarity among the plant communities of the interstade, the Late Pleistocene–Early Holocene transition, and pristine prairie of today. This investigation emphasizes the need for additional research into the variation in stable carbon isotope signals vertically within the profile and across the landscape. Issues include the source of the near-surface depletion zone, the relationship between isotopic values in the soil versus those of the vegetation, and variation in soil δ13C values δ13C throughout the landscape.

Compensatory dynamics are rare in naturalecological communities - Houlahan, J.E.; Currie, D.J.; Cottenie, K.; Cumming, G.S.; Ernest, S.K.M.; Findlay, C.S.; Fuhlendorf, S.D.; Gaedke, U.; Legendre, P.; Magnuson, J.J.; McArdle, B.H.; Muldavin, E.H.; et al. (Proceedings of the National Academy of Sciences, 2007)
In population ecology, there has been a fundamental controversy about the relative importance of competition-driven (density-dependent) population regulation vs. abiotic influences such as temperature and precipitation. The same issue arises at the community level; are population sizes driven primarily by changes in the abundances of cooccurring competitors (i.e., compensatory dynamics), or do most species have a common response to environmental factors? Competitive interactions have had a central place in ecological theory, dating back to Gleason, Volterra, Hutchison and MacArthur, and, more recently, Hubbell's influential unified neutral theory of biodiversity and biogeography. If competitive interactions are important in driving year-to-year fluctuations in abundance, then changes in the abundance of one species should generally be accompanied by compensatory changes in the abundances of others. Thus, one necessary consequence of strong compensatory forces is that, on average, species within communities will covary negatively. Here we use measures of community covariance to assess the prevalence of negative covariance in 41 natural communities comprising different taxa at a range of spatial scales. We found that species in natural communities tended to covary positively rather than negatively, the opposite of what would be expected if compensatory dynamics were important. These findings suggest that abiotic factors such as temperature and precipitation are more important than competitive interactions in driving year-to-year fluctuations in species abundance within communities.
Keywords: biological interactions; Community dynamics; negative covariance; neutral models; zero-sum

Consequences of conversion of native Mesic grassland to coniferous forest on soil processes and ecosystem C and N storage - McKinley, D.C. (Kansas State University, 2007)

Consumptionof mycorrhizal and saprophytic fungi by Collembola in grassland soils - Jonas, J.L.; G.T. Wilson; White, P.M.; Anthony Joern (Soil Biology and Biochemistry, 2007)
Although soil-dwelling Collembola can influence plant growth and nutrient cycling, their specific role in soil food webs is poorly understood. Soil-free microcosm studies suggest that Collembola are primarily fungivores where they feed preferentially on saprophytic fungi (SF) over other fungal types. We directly assessed collembolan consumption of arbuscular mycorrhizal fungi (AMF) and SF using plant–soil mesocosms and natural abundance stable carbon isotope techniques. Mycorrhizal Andropogon gerardii (C4 grass) seedlings were placed in pots containing Collembola and soil from a C3 plant dominated site, while mycorrhizal Pascopyrum smithii (C3 grass) seedlings were placed in pots with Collembola and soil collected at a C4 plant dominated site. After 6 weeks, collembolans assimilated carbon derived from C3 and C4 sources in both A. gerardii and P. smithii treatments. Comparing Collembola isotope values in AMF vs. AMF-suppressed treatments, our data show that both AMF and SF were consumed in these experimental soil environments.
Keywords: Andropogon gerardii; Arbuscular mycorrhizal fungi; Collembola; grassland; Natural abundance stable isotopes; Pascopyrum smithii; Saprophytic fungi; δ13C

Demographic response of a grassland rodent to environmental variability - Reed, A.W.; Kaufman, G.A.; Sandercock, B.K. (Journal of Mammalogy, 2007)
We used stage-structured matrix population models, derived from 3 years with disparate levels of precipitation, to assess the potential effects of climate change on annual population growth (λ) of deer mice (Peromyscus maniculatus). Populations of deer mice increased during a year of normal precipitation (λ = 1.69 ± 0.02 SE) and a wet year (λ = 1.03 ± 0.02), but declined in a dry year (λ = 0.34 ± 0.02). Life-table response experiment analyses indicated that reduced survival of adults in the dry year, and reduced survival of pups and juveniles in the wet year, exerted the greatest influence on variation in population growth. Stochastic models that projected populations of deer mice for a 50-year period predicted that populations would not be able to persist if mean annual precipitation was reduced ≥11% by increasing the frequency of dry years. Furthermore, the stochastic population growth rate declined more quickly when the probability of a normal year was reduced, simulating increased variability in rainfall, relative to other scenarios examined. Our stochastic models indicate that a relatively small reduction in mean precipitation could result in substantial population declines of P. maniculatus in the mixed-grass prairie of central North America.
Keywords: Climate change; deer mouse; life-table response experiment; matrix model; Peromyscus maniculatus; prairie; stochastic model

Diurnal activity and habitat associations of white-tailed deer in tallgrass prairie of eastern Kansas - Volk, M.D.; D.W. Kaufman; Kaufman, G.A. (Transactions of the Kansas Academy of Science, 2007)
Diurnal and seasonal patterns of activity and habitat associations of white-tailed deer (Odocoileus virginianus) were assessed in a mosaic of grassland and woodland habitats on the Konza Prairie Biological Station, Kansas. We recorded deer seen during daylight hours in summer, autumn and winter periods from June 1997 through February 1998. Overall, diurnal activity increased from summer to winter and was largely crepuscular (i.e., early morning and late evening). Deer were observed primarily in lower uplands during summer and winter, and in lowlands during autumn. At a coarse scale (6.25 ha), white-tailed deer selected areas that had woody vegetation and avoided those that were dominated by grassy vegetation. In contrast, at a fine scale, groups of deer most often were observed foraging in the immediate vicinity of grassland vegetation, rather than in or by woody vegetation.
Keywords: Flint Hills; grassland; Konza Prairie; Odocoileus virginianus; seasonal activity; topography; woodland; woody invasion

Diversity of a disease resistance gene homolog in Andropogon gerardii (Poaceae) is correlated with precipitation - Rouse, M.N. (Kansas State University, 2007)
Ecological clines often result in gradients of disease pressure in natural plant communities, imposing a gradient of selection on disease resistance genes. We describe the diversity of a resistance gene homolog in natural populations of the dominant tallgrass prairie grass, Andropogon gerardii, across a precipitation gradient ranging from 47.63 cm/year in western Kansas to 104.7 cm/year in central Missouri. Since moisture facilitates infection by foliar bacterial pathogens, plants along this precipitation gradient will tend to experience heavier bacterial disease pressure to the east. In maize, the gene Rxo1 confers resistance to the pathogenic bacterium Burkholderia andropogonis. Rxo1 homologs have been identified in A. gerardii and B. andropogonis is known to infect natural populations of A. gerardii. The spatial genetic structure of A. gerardii was assessed from central Missouri to western Kansas by genotyping with AFLP markers. Samples were also genotyped for Rxo1 homologs by amplifying an 810 base pair region of the leucine-rich repeat and digesting with restriction enzymes. We compared Rxo1 homolog diversity to AFLP diversity across different spatial scales. Genetic dissimilarity based on AFLP markers was lower than would have occurred by chance at distances up to 30 m, and different prairies were more dissimilar than would have occurred by chance, but there was not a longitudinal trend in within-prairie dissimilarity as measured by AFLP markers. Dissimilarity of the Rxo1 homologs was higher in the east suggesting the presence of diversifying selection in the more disease-conducive eastern environments.
Keywords: Amplified fragment length polymorphism; Andropogon gerardii; genetic diversity; Leucine-rich repeat; Polyploidy; Spatial genetic structure

Does species diversity limitproductivity in natural grassland communities? - Grace, J.B.; Anderson, T.M.; M.D. Smith; Seabloom, E.; Andelman, S.J.; Meche, G.; Weiher, E.; Allain, L.K.; Jutila, H.; Sankaran, M.; Knops, J.; Ritchie, M.; et al. (Ecology Letters, 2007)
Theoretical analyses and experimental studies of synthesized assemblages indicate that under particular circumstances species diversity can enhance community productivity through niche complementarity. It remains unclear whether this process has important effects in mature natural ecosystems where competitive feedbacks and complex environmental influences affect diversity–productivity relationships. In this study, we evaluated diversity–productivity relationships while statistically controlling for environmental influences in 12 natural grassland ecosystems. Because diversity–productivity relationships are conspicuously nonlinear, we developed a nonlinear structural equation modeling (SEM) methodology to separate the effects of diversity on productivity from the effects of productivity on diversity. Meta-analysis was used to summarize the SEM findings across studies. While competitive effects were readily detected, enhancement of production by diversity was not. These results suggest that the influence of small-scale diversity on productivity in mature natural systems is a weak force, both in absolute terms and relative to the effects of other controls on productivity.

Ecological genomics: making the leap from model systems in the lab to native populations in the field. Frontiers in Ecology and the Environment - Travers, S.E.; M.D. Smith; Bai, J.; Hulbert, S.H.; Leach, J.E.; Schnable, P.S.; Alan K. Knapp; Milliken, G.A.; Fay, P.A.; Saleh, A.; Garrett, K.A. (Frontiers in Ecology and the Environment, 2007)
Recent reviews have emphasized the need to incorporate genomics into ecological field studies to further understand how species respond to changing environmental conditions. Genomic tools, such as cDNA (complementary DNA) microarrays, allow for the simultaneous analysis of gene expression of thousands of genes from all or part of an organism's genome (the transcription profile), thereby revealing the genetic mechanisms that underlie species' responses to environmental change. However, despite their potential, two major limitations have hindered the incorporation of microarrays and other genomic tools into field studies: (1) the limited availability of microarrays for ecologically relevant, non-model species and limited financial resources for developing new microarrays; and (2) concern that high sensitivity of gene expression to even subtle alterations in environmental conditions will hinder detection of relevant changes in field measures of transcription profiles. Here, we show that with cross-species hybridizations of microarrays developed for a closely related model organism, an appropriate experimental design, and sufficient replication, transcriptional profiling can successfully be incorporated into field studies. In this way, relevant changes in gene expression with changing environmental conditions can be detected.

Ecosystem consequences of invasive exotic species in grasslands. - Baker, P.K. (Colorado State University, 2007)

The effect of intra-seasonal variation in precipitation on the productivity of grasses and grasslands - Swemmer, A.M. (Colorado State University, 2007)

Effects of grazing on growth and morphology of rhizomatous and caespitose grasses in tallgrass prairie - N'Guessan, M. (Kansas State University, 2007)
Herbivory is one of the major biotic interactions shaping the structure and dynamics of grassland plant populations and community structure. The two major grass growth forms, rhizomatous and caespitose species, may show different grazing tolerance and short-term overcompensation may offset long-term reductions in plant performance and fitness. The objectives of this study were to assess 1) the effects of long-term ungulate grazing on plant architecture, population structure, and life history traits of the caespitose perennial grass, Schizachyrium scoparium (little bluestem), and the rhizomatous Bouteloua curtipendula (sideoats grama) in tallgrass prairie, and 2) the effects of grazing intensity (frequency of defoliation) on growth responses of little bluestem. Long-term bison grazing decreased the cover, frequency, tiller height, and proportion of tillers producing seed in little bluestem, but caused no changes in tiller density and total genet size. Grazed little bluestem plants maintained a significantly larger below ground bud bank. Bison grazing had no long-term effect on the abundance, bud bank densities, or rhizome growth of the rhizomatous side-oats grama grass. Biomass, tiller density, relative growth rates, and proportion of tillers flowering in little bluestem all decreased with increasing frequency of defoliation. However, even an intense grazing regime (9 defoliations over a 12 month period) caused no plant mortality and no changes in new tiller emergence rates, or bud bank densities. Increasing defoliation frequency did result in shifts in plant architecture, as an increasing proportion of extravaginal tillers led to a more lateral, decumbent growth form. These results show that the rhizomatous side-oats grama grass has a significantly higher grazing tolerance than does little bluestem, and/or that bison selectively graze little bluestem. Results from responses to the experimental defoliation regimes suggest that little bluestem shows lower tolerance to high frequency of defoliation, and its maintenance of a reserve below ground bud bank may be its primary tolerance mechanism, allowing tiller populations to recover following severe defoliation.
Keywords: caespitose; Grazing; growth; morphology; rhizomatous; tallgrass