Effects of prairie vole runways on tallgrass prairie - Ross, B.E.; Reed, A.W.; Rehmeier, R.L.; Kaufman, G.A.; D.W. Kaufman (Transactions of the Kansas Academy of Science, 2007)
Disturbances by large mammals influence plant populations and ecosystem processes. In contrast, impacts on ecosystem processes at local scales by small herbivorous rodents are relatively unknown. To examine effects of the runways of prairie voles (Microtus ochrogaster) on soil nitrogen, we collected soil cores from under runways, along the runway edges and at 0.25 and 2 m away from runways. Plant samples (both current and previous year's growth) were clipped from microsites at edges of runways and at 0.25 and 2 m away from runways. Concentrations of soil nitrate were highest along runway edges and lowest 2 m away, whereas those of ammonium were highest 0.25 m away from runways and lowest under runways and along runway edges. Biomass of plants from previous growth (litter) was higher along edges of runways than at 0.25 and 2 m from runway edges. In contrast to differences in soil nitrate and ammonium concentrations and in litter biomass among microsites, carbon: nitrogen (C:N) ratios of big bluestem and live plant biomass were similar among the three microsites. Our data suggest that prairie voles do affect nutrient dynamics and plant litter at a local scale in tallgrass prairie.
Keywords: C:N ratios; Herbivory; Microtus ochrogaster; nitrogen dynamics; plant biomass; plant-animal interaction; prairie vole; runways

Effects of the herbivorous minnow, southern redbelly dace (Phoxinus erythrogaster) on stream ecosystem structure and function - Bertrand, K.N.; K. B. Gido (Oecologia, 2007)
We used field and mesocosm experiments to measure effects of southern redbelly dace (Phoxinus erythrogaster), a grazing minnow, on stream ecosystem structure and function. Ecosystem structure was quantified as algal filament length, algal biomass, size distribution of particulate organic matter (POM), algal assemblage structure, and invertebrate assemblage structure, whereas ecosystem function was based on gross and net primary productivity. Our experiments showed that moderate densities of Phoxinus temporarily reduced mean algal filament length and mean size of POM relative to fishless controls. However, there was no detectable effect on algal biomass or ecosystem primary productivity. Several factors could explain the lack of effect of Phoxinus on primary productivity including increased algal production efficiency in grazed treatments or increased grazing by other organisms in fishless treatments. The inability of Phoxinus to reduce algal biomass and system productivity contrasts with experimental results based on other grazing minnows, such as the central stoneroller (Campostoma anomalum), and questions the generality of grazer effects in stream ecosystems. However, environmental venue and the spatial and temporal scale of ecosystem measurements can greatly influence the outcome of these experiments.
Keywords: grazers; prairie streams; Stream metabolism

Environmental and plant community determinants ofspecies loss following nitrogen enrichment - Clark, C.M.; Cleland, E.E.; Scott. L. Collins; Fargione, J.E.; Gough, L.; Pennings, S.C.; K.N. Suding; Grace, J.B. (Ecology Letters, 2007)
Global energy use and food production have increased nitrogen inputs to ecosystems worldwide, impacting plant community diversity, composition, and function. Previous studies show considerable variation across terrestrial herbaceous ecosystems in the magnitude of species loss following nitrogen (N) enrichment. What controls this variation remains unknown. We present results from 23 N-addition experiments across North America, representing a range of climatic, soil and plant community properties, to determine conditions that lead to greater diversity decline. Species loss in these communities ranged from 0 to 65% of control richness. Using hierarchical structural equation modelling, we found greater species loss in communities with a lower soil cation exchange capacity, colder regional temperature, and larger production increase following N addition, independent of initial species richness, plant productivity, and the relative abundance of most plant functional groups. Our results indicate sensitivity to N addition is co-determined by environmental conditions and production responsiveness, which overwhelm the effects of initial community structure and composition.

Estimating aboveground net primary production in grassland and herbaceous dominated ecosystems - Alan K. Knapp; J. M. Briggs; Childers, D.L.; Sala, O.E. (Principles and Standards for Measuring Net Primary Production, 2007)
This paper reviews past and currently accepted methods of estimating aboveground net primary production (NPP) in grass and herb-dominated ecosystems, provides some guiding principles and recommendations to facilitate accurate determination of aboveground NPP, and discusses biases and errors and sampling adequacy.

Expanding the concept of trophic state in aquatic ecosystems: It's not just the autotrophs - W. K. Dodds; Cole, J.J. (Aquatic Sciences, 2007)
“Trophic state” is often used to classify aquatic ecosystems according to biotic productivity. Primary productivity (or a surrogate for it) has always been used as the metric of trophic state. We make the case here that both primary production and key heterotrophic processes are needed to evaluate trophic state. Defined as the relative flux rate of carbon (C) into the food web, trophic state is a fundamental property that is intimately related to both ecosystem structure and how humans influence water quality. Rates of heterotrophic activity can exceed primary production in many aquatic ecosystems including oceans, lakes, and streams. A comprehensive definition of trophic state with respect to aquatic food webs requires accounting for both the oxidation of organic C (respiration) and photosynthetic fixation of inorganic C (primary production). This inclusive definition is required because food webs can be fueled in part by allochthonous C. We propose autotrophic and heterotrophic states be defined by rates of photosynthetic and respiratory C fluxes respectively, and both be used to characterize ecosystems. Cumulative frequency distributions of both can be developed for minimally impacted aquatic systems as a baseline against which to compare human-influenced sites as well as for describing the range of conditions that aquatic organisms have experienced in their recent evolutionary history. Subsidies of organic C and inorganic nutrients to aquatic ecosystems influence heterotrophic state, so characterizing the base of the food web necessitates a stoichiometric view of supply rates, use efficiencies, and recycling of inorganic and organic materials.
Keywords: autotrophic; ecosystem; heterotrophic; Trophic state

Experimentaldesign for two-color microarrays applied in a pre-existing split-plotexperiment - Milliken, G.A.; Garrett, K.A.; Travers, S.E. (Statistical Applications in Genetics and Molecular Biology, 2007)
Microarray applications for the study of gene expression are becoming accessible for researchers in more and more systems. Applications from field or laboratory experiments are often complicated by the need to superimpose sample pairing for two-color arrays on experimental designs that may already be complex. For example, split-plot designs are commonly used in biological systems where experiments involve two types of treatments that are not readily applied at the same scale. We demonstrate how effects that are confounded with arrays can still be estimated when there is sufficient replication. To illustrate, we evaluate three methods of sample pairing superimposed on a split-plot design with two treatments, deriving the variance associated with parameter estimates for each. Design A has levels of the whole plot treatment paired on the same microarray within a level of the subplot treatment. Design B has crossed levels paired on the same microarray. Design C has levels of the treatment applied to subplots paired on the same microarray within a whole plot. Designs A and B have lower variance than design C for comparing the levels of the whole plot treatment. Designs B and C have lower variance for comparing the levels of the subplot treatment and design C has lower variance for comparing the levels of the subplot treatment within each level of the whole plot treatment. We provide SAS code for the analyses of variance discussed.
Keywords: Ecological genomics; experimental design; gene expression; microarray analysis; split-plot design

Factors affecting reproductive success in a lek-matingbird: the Greater Prairie-chicken - Nooker, J.K. (Kansas State University, 2007)
Sexual selection via female choice and male-male aggression leads to elaboration of male traits. If male traits correlated with reproductive success are honest signals of male quality, survival costs may be associated with the expression of those traits. Testosterone (hereafter ‘T’) may enhance male breeding success, but T can also reduce immunocompetence and survival. Socially monogamous male birds with higher circulating T experience reproductive advantages, but the role of T in lek mating systems is largely unknown. To address these issues, I individually marked and conducted focal behavioral observations of greater prairie-chickens (Tympanuchus cupido) at five lek sites over a 5-year period. Females were fitted with radio-telemetry to monitor nesting success and survival. I examined the relationship between male traits and mating success using multinomial discrete choice models, a statistical method not previously applied to studies of sexual selection. Male mating success was highly skewed at greater prairie-chicken leks with 18.5% of males obtaining 87.2% of all successful copulations (n = 108 males; 85 copulations). Mating success was influenced most by male behavior, followed by several morphological attributes. The role of T was quantified using blood samples and by experimentally implanting a subset of males with T. T did not consistently affect mating success. Non-territorial males had lower T levels than territorial males. Among territory holders, T was unexpectedly negatively correlated with mating success. However, the odds of receiving a copulation were 4.3 times (0.42 to 45.3) greater for T-implanted males than males with sham implants. Future work should explore the interactions among the immune system, parasite load, and mating success of prairie-chickens. Annual survival of male prairie-chickens was not related to mating success, behavior, age or T level, suggesting there is no cost of increased male mating success. Like males, reproductive success of females was also highly skewed because < 10% of nests successfully hatched young. Comparisons of seasonal and annual survival rates indicate that females experience increased mortality during the breeding season relative to the nonbreeding season. Synthesis of field estimates of demographic parameters indicates prairie-chicken populations will decline without changes in rangeland management to reduce predator numbers or provide more nesting cover.
Keywords: Female mate choice; Grouse; Nest success; Reproductive success; Sexual selection; survival; Testosterone

Fire and resource availability influence carbon and water relations of the C3 shrub Cornus drummondii in a mesic grassland - Heisler, J.L.; Alan K. Knapp; J. M. Briggs (Proceedings of the 23rd Tall Timbers Fire Ecology Conference: Fire in Grassland and Shrubland Ecosystems, 2007)
A dramatic increase in cover by woody vegetation has been observed in grasslands worldwide, due to independent and interacting global changes. In the C4-dominated mesic tallgrass prairie of North America, the most proximate factor driving this shift in growth-form dominance is fire exclusion. In 2001, we reintroduced annual fire into a C4-dominated mesic grassland where it had been excluded for 10 y, and evaluated changes in stem density and ecophysiology of an increasingly abundant C3 woody plant, roughleaf dogwood(Cornus drummondii). Our primary objective was to quantify the impacts of fire-induced aboveground mortality and resource constraints on the persistence of roughleaf dogwood in this ecosystem. In both years of the study (2001–2002), burned shrubs suffered a complete loss of aboveground biomass due to top-kill from spring fire but persisted via resprouting. A considerable reduction in total growing-season precipitation in 2002, as compared to 2001, revealed that resprouts had lower mortality with reduced soil moisture, were less vulnerable to reductions in soil moisture availability, and maintained higher predawn xylem pressure potentials and rates of photosynthesis than did unburned shrubs. Additionally, enrich-ment of13Cleaf in burned shrubs in 2002 was indicative of greater water use efficiency of resprouting stems. During the drought that occurred in the second growing season, mortality of stems within unburned shrub islands increased and was nearly 9 times more than in burned shrub islands. Thus, resprouting shrubs—with their characteristics of reduced leaf tissue, taller stems, and greater stem densities—are efficient in rapidly reoccupying post-fire environments, even with the added stress of below-average precipitation during the growing season. The results of this study suggest that within this grassland, reintroduction of fire will not eliminate rough leaf dogwood in the short term because of its ability to resprout vigorously and persist, even under stressful moisture conditions. Given that North American grasslands are important both economically and ecologically, fire management plans should therefore emphasize frequent fire to prevent shrub establishment

Fishes and floods: stream ecosystem drivers in the Great Plains - Bertrand, K.N. (Kansas State University, 2007)
Global climate change could lead to less frequent but more severe precipitation events in the Great Plains, altering the hydrologic regimes of streams. It is important to quantify species roles in these dynamic systems, because changes in stream communities are likely to accompany predicted changes in hydrology. The effects of species on ecosystem processes also are limited by the frequency of disturbance, because prairie streams are harsh, nonequilibrium systems characterized by a wide range of disturbances. In particular, frequent floods that reset the ecosystem to an early successional state can override the influence of consumer populations because the availability of resources is too unpredictable to maintain stable populations of those species or because species are absent following the flood. As flood frequency decreases, potential consumer effects may intensify. Using a combination of field and experimental stream mesocosm experiments, I (1) characterized the ecosystem effects of southern redbelly dace (Phoxinus erythrogaster), a grazing minnow, (2) tested the interactive effects of flood frequency and the presence of water column (red shiner; Cyprinella lutrensis) or grazing minnows (Phoxinus) on ecosystem processes, and (3) tested the effects of species loss from the grazer functional feeding group on stream ecosystem structure and function. I found that dace affected some aspects of ecosystem structure but not function, which suggested that grazer effects in prairie streams may not be consistent across taxa. In the context of flood frequency, both the water column omnivore and dace affected recovery of prairie stream primary producers following flooding disturbance by stimulating production, presumably through nutrient remineralization. However, some of these effects were transient or dependent on flood frequency, and my results indicate that consumer effects depend not only on environmental venue but also on the balance between consumptive losses and nutrient stimulation. In a comparison of the effects of removing different taxa from a grazer assemblage, the loss of crayfish, snails, or dace from a grazer assemblage did not differentially affect ecosystem processes, suggesting overlap in the ecosystem roles of these species in the context of this experiment.
Keywords: Biodiversitym; Ecosystem function; Flood frequency; Grazing minnow; Omnivorous minnow; Prairie stream

Genesis and spatial distribution of uplandsoils in east central Kansas - Presley, D.R. (Kansas State University, 2007)
Upland soils in east central Kansas have a complex genesis, often contain one or more paleosols, and form in multiple parent materials including loess, colluvium, residuum, and alluvium. Quaternary loess/paleosol investigations have largely ignored this region of Kansas, as the total loess thickness on uplands is <2 m thick. In this study, the objectives are to examine the morphology and genesis of the soils of interest and how these characteristics vary within soil profiles, across landscapes, and throughout the current series mapping extent. The series of interest include the Irwin, Konza, Dwight, and Ladysmith soil series. Methods used in this study include field descriptions and sampling, terrain analysis, micromorphological investigations, and laboratory characterization, including silt and clay mineralogy. Accelerator mass spectrometry (AMS) was used for numerical dating and determination of stable carbon isotope values (δ13C) for selected paleosols. Radiocarbon ages ranged from 24,000 to 19,000 yr BP and δ13C values were between -19 and -17 ‰ (PDB), indicating that the paleosols were formed in Gilman Canyon loess or the Severance formation, under a mix of C3 and C4 vegetation. Terrain analysis results illustrated that, in given drainage areas, the soil series were mapped on a wide range of slope positions. Field observations and terrain analysis confirmed no relationships between mollic epipedon thickness, solum thickness, paleosol thickness, or depth to the paleosol with respect to landform. Micromorphological investigations revealed increasing soil development with depth, i.e., the presence of two paleosols beneath the modern soil. Mean particle size and mineralogy vary geographically within individual series. Pedogenic carbonate accumulations and redoximorphic concentrations are common features of the soils of interest, and less common features include sodium and gypsum accumulations, slickensides, and redoximorphic depletions. Results from this study will be provided to the USDA-NRCS for use in future soil survey updates, and will contribute to Quaternary loess/paleosol knowledge in Kansas and the Great Plains.
Keywords: genesis; kansas; Loess; mapping; Paleosols; soil

Global-scale similarities in nitrogen release patterns during long-term decomposition - Parton, W.J.; Silver, W.L.; Burke, I.C.; Grassens, L.; Harmon, M.E.; Currie, W.S.; King, J.Y.; Adair, E.C.; Brandt, L.A.; Hart, S.C.; Fasth, B. (Science, 2007)
Litter decomposition provides the primary source of mineral nitrogen (N) for biological activity in most terrestrial ecosystems. A 10-year decomposition experiment in 21 sites from seven biomes found that net N release from leaf litter is dominantly driven by the initial tissue N concentration and mass remaining regardless of climate, edaphic conditions, or biota. Arid grasslands exposed to high ultraviolet radiation were an exception, where net N release was insensitive to initial N. Roots released N linearly with decomposition and exhibited little net N immobilization. We suggest that fundamental constraints on decomposer physiologies lead to predictable global-scale patterns in net N release during decomposition.

Grasshopper (Orthoptera: Acrididae) communities respond to fire, bison grazing and weather in North Americantallgrass prairie: A long-term study - Jonas, J.L.; Anthony Joern (Oecologia, 2007)
Because both intrinsic and extrinsic factors influence insect population dynamics, operating at a range of temporal and spatial scales, it is difficult to assess their contributions. Long-term studies are ideal for assessing the relative contributions of multiple factors to abundance and community dynamics. Using data spanning 25 years, we investigate the contributions of weather at annual and decadal scales, fire return interval, and grazing by bison to understand the dynamics of abundance and community composition in grasshopper assemblages from North American continental grassland. Each of these three primary drivers of grassland ecosystem dynamics affects grasshopper population and community dynamics. Negative feedbacks in abundances, as expected for regulated populations, were observed for all feeding guilds of grasshoppers. Abundance of grasshoppers did not vary in response to frequency of prescribed burns at the site. Among watersheds that varied with respect to controlled spring burns and grazing by bison, species composition of grasshopper assemblages responded significantly to both after 25 years. However, after more than 20 years of fire and grazing treatments, the number of years since the last fire was more important than the managed long-term fire frequency per se. Yearly shifts in species composition (1983–2005), examined using non-metric multidimensional scaling and fourth-corner analysis, were best explained by local weather events occurring early in grasshopper life cycles. Large-scale patterns were represented by the Palmer Drought Severity Index and the North Atlantic Oscillation (NAO). The NAO was significantly correlated with annual mean frequencies of grasshoppers, especially for forb- and mixed-feeding species. Primary grassland drivers—fire, grazing and weather—contributing both intrinsic and extrinsic influences modulate long-term fluctuations in grasshopper abundances and community taxonomic composition.
Keywords: Fire frequency; Insect populations; Konza Prairie; Long-Term Ecological Research Program; Weather

Insect development under predation risk, variable temperature, and variable food quality - Logan, J.D.; Wolesensky, W.; Anthony Joern (Mathematical Biosciences and Engineering, 2007)
We model the development of an individual insect, a grasshopper, through its nymphal period as a function of a trade-off between prey vigilance and nutrient intake in a changing environment. Both temperature and food quality may be variable. We scale up to the population level using natural mortality and a predation risk that is mass, vigilance, and temperature dependent. Simulations reveal the sensitivity of both survivorship and development time to risk and nutrient intake, including food quality and temperature variations. The model quantifies the crucial role of temperature in trophic interactions and development, which is an important issue in assessing the effects of global climate change on complex environmental interactions.
Keywords: eco-physiology; grasshoppers; Temperature; vigilance

Intra-seasonal precipitation patterns and aboveground productivity in three perennial grasslands - Swemmer, A.M.; Alan K. Knapp; Snyman, H.A. (Journal of Ecology, 2007)
1 Relationships between above-ground net primary productivity (ANPP) of grasslands and annual precipitation are often weak at the site level, with much of the inter-annual variation in ANPP left unexplained. A potential reason for this is that the distribution of precipitation within a growing season affects productivity in addition to the total amount. 2 We analysed long-term ANPP data for three southern African temperate grasslands (mean annual precipitation ranging from 538 mm to 798 mm) to determine the effects of precipitation event size, number and spacing relative to seasonal totals. 3 Ungrazed, non-manipulated treatments at each site showed contrasting results despite sharing a common, dominant species. At the driest site, a model combining average event size and number of events per growing season provided a substantially better fit to the ANPP data than precipitation amount (seasonal total). At the wettest site, the interval between events was the most important precipitation variable. Precipitation distribution was not important at the intermediate site where amount was the best predictor of ANPP. A limit to the size of precipitation events efficiently utilized for ANPP was evident for the driest site only. 4 At each site, experimental treatments that altered species composition and soil fertility had little effect on precipitation–ANPP relationships. The lack of consistency in the relative importance of the precipitation variables among sites suggests that local, edaphic factors modify precipitation–ANPP relationships. 5 This analysis demonstrates that the distribution and size of precipitation events can affect ANPP independent of precipitation amount. As altered precipitation regimes are forecast by global climate models, the sensitivity of ecosystems to precipitation distribution should be considered when predicting responses to climate change. 6 While mean values of precipitation, and other ecosystem drivers, are typically used to predict function at the level of whole ecosystems, our results show that more complex measures of environmental variability may be required to understand ecosystem function, and to increase the accuracy of predictions of ecosystem responses to global change.

Linking benthic algal biomass to stream substratum topography - Murdock, J.N.; W. K. Dodds (Journal of Phycology, 2007)
The physical properties of substrata significantly influence benthic algal development. We explored the relationships among substratum surface texture and orientation with epilithic microphytobenthic biomass accumulation at the whole-substratum and micrometer scales. Unglazed clay tiles set at three orientations (horizontal, vertical, and 45°), and six substrata of varying surface roughness were deployed in a prairie stream for 3 weeks. Substrata were analyzed for loosely attached, adnate, and total benthic algal biomass as chl a, and confocal laser scanning microscopy was used to measure substrata microtopography (i.e., roughness, microscale slope angles, and three-dimensional surface area). At the whole-substratum level, vertical substrata collected significantly (P < 0.05) less algal biomass, averaging 34% and 36% less than horizontal and 45° substrata, respectively. Benthic algal biomass was also significantly less on smoother surfaces; glass averaged 29% less biomass than stream rocks. At the microscale level, benthic algal biomass was the greatest at intermediate values, peaking at a mean roughness of approximately 17 μm, a mean microscale slope of 50°, and a projected/areal surface area ratio of 2:1. The proportion of adnate algae increased with surface roughness (26% and 67% for glass and brick, respectively), suggesting that substratum type changes the efficiency of algal removal by brushing. Individual substrata and microsubstrata characteristics can have a strong effect on benthic algae development and potentially affect reach scale algal variability as mediated by geomorphology.
Keywords: confocal microscopy; microphytobenthos; orientation; periphyton; roughness; surface area

Linking water uptake with rooting patterns in grassland species - Jesse B. Nippert; Alan K. Knapp (Oecologia, 2007)
Water availability strongly governs grassland primary productivity, yet this resource varies dramatically in time (seasonally) and space (with soil depth and topography). It has long been assumed that co-occurring species differ in their partitioning of water use by depth, but direct evidence is lacking. We report data from two growing seasons (2004–2005) in which we measured the isotopic signature of plant xylem water from seven species (including C3 forbs and shrubs and C4 grasses) growing along a topographic gradient at the Konza Prairie Biological Station. Plant xylem stable oxygen isotope ratio (δ18O) values were compared to soil water δ18O profiles, recent rainfall events, and groundwater. Species varied in both their temporal patterns of water use and their responses to seasonal droughts in both years. During wet periods, species differences in water use were minimal, with common dependency on recent rainfall events stored in the upper soil layers. However, during dry periods, most C3 species used proportionally more water from deeper portions of the soil profile relative to the C4 grasses. Plants in uplands used more shallow soil water compared to those in lowlands, with the greatest differences across the topographic gradient occurring during dry periods. While the documented vertical root distribution varies by species and growth form in this grassland, each of the species we measured appeared to compete for the same surface layer soil moisture when water was not limiting. Thus, our results suggest that variation in precipitation history and landscape positions are greater determinants of water-use patterns than would be expected based on absolute rooting depth.
Keywords: C3 plants; C4 plants; Mixing model; Stable oxygen isotope ratio; tallgrass prairie

Microbial responses to nitrogen addition in three contrasting grassland ecosystems - Lydia H. Zeglin; Stursova, M.; Sinsabaugh, R.L.; Scott. L. Collins (Oecologia, 2007)
The effects of global N enrichment on soil processes in grassland ecosystems have received relatively little study. We assessed microbial community response to experimental increases in N availability by measuring extracellular enzyme activity (EEA) in soils from three grasslands with contrasting edaphic and climatic characteristics: a semiarid grassland at the Sevilleta National Wildlife Refuge, New Mexico, USA (SEV), and mesic grasslands at Konza Prairie, Kansas, USA (KNZ) and Ukulinga Research Farm, KwaZulu-Natal, South Africa (SAF). We hypothesized that, with N enrichment, soil microbial communities would increase C and P acquisition activity, decrease N acquisition activity, and reduce oxidative enzyme production (leading to recalcitrant soil organic matter [SOM] accumulation), and that the magnitude of response would decrease with soil age (due to higher stabilization of enzyme pools and P limitation of response). Cellulolytic activities followed the pattern predicted, increasing 35–52% in the youngest soil (SEV), 10–14% in the intermediate soil (KNZ) and remaining constant in the oldest soil (SAF). The magnitude of phosphatase response did not vary among sites. N acquisition activity response was driven by the enzyme closest to its pH optimum in each soil: i.e., leucine aminopeptidase in alkaline soil, β-N-acetylglucosaminidase in acidic soil. Oxidative enzyme activity varied widely across ecosystems, but did not decrease with N amendment at any site. Likewise, SOM and %C pools did not respond to N enrichment. Between-site variation in both soil properties and EEA exceeded any treatment response, and a large portion of EEA variability (leucine aminopeptidase and oxidative enzymes), 68% as shown by principal components analysis, was strongly related to soil pH (r = 0.91, P < 0.001). In these grassland ecosystems, soil microbial responses appear constrained by a molecular-scale (pH) edaphic factor, making potential breakdown rates of SOM resistant to N enrichment.
Keywords: Extracellular enzyme activity; Soil carbon

Mycorrhizal community dynamics following nitrogen fertilization: A cross site test in five grasslands - Egerton-Warburton, L.M.; Johnson, N.C.; Allen, E.B. (Ecological Monographs, 2007)
Arbuscular mycorrhizal fungi (AMF) are considered both ecologically and physiologically important to many plant communities. As a result, any alteration in AMF community structure following soil nitrogen (N) enrichment may impact plant community function and contribute to widespread changes in grassland productivity. We evaluated the responses of AMF communities to N fertilization (≥100 kg N·ha−1·yr−1) in five perennial grasslands within the Long-Term Ecological Research network to generate a broader understanding of the drivers contributing to AMF species richness and diversity with increasing soil N fertility, and subsequent effects to host-plant communities. AMF spore and hyphal community data at three mesic sites (Cedar Creek, Kellogg Biological Station, Konza Prairie) and two semiarid sites (Sevilleta, Shortgrass Steppe) were collected over two consecutive years and used to test four hypotheses about AMF responses to N fertilization. Under ambient soil N, plant annual net primary productivity and soil phosphorus (P) were strongly related to climatic differences in AMF communities (semiarid vs. mesic). Following N fertilization, the drivers of AMF community structure were soil N availability, N:P supply ratio, and host-plant photosynthetic strategy (C3 vs. C4) but not climate. In P-rich soils (low N:P), N fertilization reduced AMF productivity, species richness, and diversity and intensified AMF community convergence due to the loss of rare AMF species and the increased abundance of Glomus species. In P-limited soils (high N:P), AMF productivity, species richness, and diversity increased with N fertilization; the most responsive AMF taxa were Acaulospora, Scutellospora, and Gigaspora. Soil N or N:P × host-plant (C3, C4) interactions further modified these responses: AMF hyphae (primarily Gigasporaceae) associated with C3 plants increased in abundance with N fertilization, whereas C4 plants hosted nitrophilous Glomus species. Such responses were independent of the duration or quantity of N fertilization, or the time since cessation of N fertilization. This synthesis provides a new understanding of AMF community patterns and processes, and it identifies three key drivers (soil N, N:P, host plant) of AMF community structure that may be tested in other communities.

Nest mate size, but not short-term need, influences begging behavior of a generalist brood parasite - Rivers, J.W. (Behavioral Ecology, 2007)
Hosts of generalist brood parasites often vary with regards to their life-history traits, and these differences have the potential to influence the competitive environment experienced by brood-parasitic nestlings. Although begging by brood parasites is more exaggerated than their hosts, it is unclear if generalist brood parasites modulate their begging behavior relative to host size. I examined the begging behavior of brown-headed cowbird (Molothrus ater) nestlings when competing against nest mates that differ in size and under different levels of short-term need. Cowbird nestlings begged on nearly all feeding visits, responded to adults as fast as (or faster than) their nest mates, and typically begged more intensively than their nest mates. Latency to beg, time spent begging, and maximum begging posture of cowbirds were similar during supplementation and deprivation treatments, indicating begging intensity was not influenced by short-term need. Time spent begging by cowbirds varied among hosts of 3 different sizes when short-term need was standardized, suggesting that nest mate size strongly influenced begging behavior. Cowbirds obtained more food when competing against an intermediate-sized host due to lower provisioning rates of small hosts or because of increased competitive ability of large host nestlings. Overall, cowbirds obtained the greatest volume of food per unit time spent begging when competing against intermediate hosts, but this value approached that of the small host when adjusted for modal brood size. These results demonstrate that cowbirds adjust their begging relative to the size of the hosts against which they compete but not to levels of short-term need.
Keywords: begging behavior; begging intensity; brown-headed cowbird; Molothrus ater; nestling competition; short-term need

Nutrient resources and stoichiometry affect the ecology of above- and belowground invertebrate consumers - Jonas, J.L. (Department of Biology, 2007)

Optimizing radio retention andminimizing radio impacts in a field study of Upland Sandpipers - Mong, T.W.; Sandercock, B.K. (Journal ofWildlife Management, 2007)
Two challenges in wildlife telemetry are optimizing the duration of transmitter attachment and minimizing the impacts of radios on the behavior and demography of the study animal. We tested 4 methods of radio attachment for a breeding population of upland sandpipers (Bartramia longicauda) under natural conditions at a tallgrass prairie site in Kansas, USA. To estimate radio retention and weekly survival rates, we used the nest survival model of Program MARK. Radio retention was lowest at the start and the end of the breeding period. The expected duration of radio retention was 1.8 years for a leg-loop harness, 40 days for radios glued to clipped feathers, 26 days for radios glued directly to feathers, and 7 days for radios glued to bare skin. Few radiomarked birds died during our study, but 4 of 8 mortality events were discovered within one week of radiomarking. Both glue and harnesses increased predation risk immediately after radio attachment. The weekly probability of survival was high after a 1-week acclimation period, and the expected survival for a 10-week breeding period was similar in males and females. Attachment of radios with glue had no effect on annual return rates. However, attachment of radios with leg harnesses resulted in lower return rates among radiomarked birds than birds without radios. Radios attached with glue were shed in <1 year but radios attached with harnesses were retained for up to 1–2 years. Our results indicate a tradeoff between optimizing radio retention and minimizing impacts on demography. Glue techniques had retention rates that were suitable for only short-term studies, but attachment with glue had no long-term effect on annual return rates. Leg harnesses provided effective radio retention that had little effect on survival rates during the stationary breeding period, but resulted in lower annual return rates. Robust estimates of radio retention and survival will assist researchers in selecting attachment techniques that best meet the study goals of future telemetry projects.
Keywords: Bartramia longicauda; glue; harness; kansas; radio attachment; shorebird; survival; Upland Sandpiper

Photosynthetic traits in C3 and C4 grassland species in mesocosm and field environments - Jesse B. Nippert; Fay, P.A.; Alan K. Knapp (Environmental and Experimental Botany, 2007)
The North American tallgrass prairie is composed of a diverse mix of C3 and C4 plant species that are subject to multiple resource limitations. C4 grasses dominate this ecosystem, purportedly due to greater photosynthetic capacity and resource-use efficiency associated with C4 photosynthesis. We tested the hypothesis that intrinsic physiological differences between C3 and C4 species are consistent with C4 grass dominance by comparing leaf gas exchange and chlorophyll fluorescence variables for seven C4 and C3 herbaceous species (legumes and non-legumes) in two different settings: experimental mesocosms and natural grassland sites. In the mesocosms, C4 grasses had higher photosynthetic rates, water potentials and water-use efficiency than the C3 species. These differences were absent in the field, where photosynthetic rates declined similarly among non-leguminous species. Thus, intrinsic photosynthetic advantages for C4 species measured in resource-rich mesocosms could not explain the dominance of C4 species in the field. Instead, C4 dominance in this ecosystem may depend more on the ability of the grasses to grow rapidly when resources are plentiful and to tolerate multiple limitations when resources are scarce.
Keywords: A:Ci curves; C3; C4; Chlorophyll fluorescence; gas exchange; Konza; tallgrass prairie

Primary production: Guiding principles and standards for measurement - Fahey, T.J.; Alan K. Knapp (Principles and Standards for Measuring Net Primary Production, 2007)
This chapter serves as an introduction to the book, outlining the general considerations in the measurement of net primary production (NPP) in particular biomes or groups of biomes (e.g. savannas, grasslands and forests), the temporal and spatial variation and principles of site selection, field sampling and laboratory procedures for NPP measurement, and statistical analysis and quality assurance/quality control.

Principles and Standards for Measuring Net Primary Production - Fahey, T.J.; Alan K. Knapp (Principles and Standards for Measuring Net Primary Production, 2007)
Standardized approaches for the measurement of primary production — the rate of energy storage in the organic matter of plants — are essential to facilitate scientific comparisons and syntheses as well as policy and management on global climate change and the carbon cycle. This book provides an overview of the principles that should underlie every program of measurement of primary production in the Earth's major biomes. Each of seven biome-based chapters provides an overview of essential features of primary production processes in the biome and detailed descriptions of the procedures used to quantify primary production in grasslands, shrublands, forests, peatlands and tundra, salt marshes, marine pelagic, and freshwater ecosystems. Recent advances in the measurement of belowground production in terrestrial biomes are described. The book also provides detailed guidelines for information management based upon current experiences of the US Long-Term Ecological Research network. Advanced techniques are described for scaling up empirical measurements of primary production using remotely-sensed information. Finally, the principles and practices for quantifying uncertainty in primary production measurements are explored using examples from various biomes.
Keywords: belowground; biomes; carbon cycle; Ecosystems; remote sensing; uncertainty

Response of microbial communities to water stress in irrigated anddrought-prone tallgrass prairie soils - Williams, M.A. (Soil Biology & Biochemistry, 2007)
To better understand how water stress and availability affect the structure of microbial communities in soil, I measured the change in phospholipid fatty acids (PLFA) and the incorporation of 13C-labeled glucose into the PLFA following exposure to water stress. Overlaid on the laboratory water stress treatment, samples were collected from drought-prone and irrigated (11 years) tallgrass prairie soil (0–10 cm depth). In the laboratory, soils were either incubated at −250 kPa or dried steadily over a 3-d period to −45 MPa. On the fourth day, the dried samples were brought up to −250 kPa and then all samples received 250 μg of glucose-C (+4000 δ13C-PDB) solution that brought them to −33 kPa matric water potential. Samples were then extracted for PLFA following 6 and 24 h of incubation (25 °C). Non-metric multidimensional scaling (NMS) techniques and multi-response permutation procedure (MRPP) showed that the largest effect on the mol% distribution of PLFA was related to the field scale water addition experiment. In response to irrigation, the PLFA 16:1ω5, 18:1+, and 18:2ω6,9 showed increases, and a15:0, a17:0, and cy19:0 showed decreases in their respective mol%. Effects related to the induction of laboratory water stress were predominantly associated with a decrease in the mol% distribution of the putative fungal biomarker (18:2ω6,9) with little to no change in the mol% distribution of the bacterial biomarkers. Interestingly, the flow of C to the microbial community was not strongly related to any single PLFA, and differences were rather subtle, but multivariate MRPP detected change to the community structure related to the laboratory water stress treatment but not related to the 11 years of field irrigation. Our results suggest that both the total and the actively metabolizing bacterial community in soil were generally resistant to the effects of water stress brought by rewetting of dry soil. However, more research is needed to understand the nature of the fungal response to drying and rewetting in soil.
Keywords: 13C-PLFA compound-specific isotope analysis of microbial communities; Drying–rewetting

Root dynamics of three dominant prairie grasses from different population sources - Klopf, R. (Southern Illinois University, 2007)

Rust and drought effects on gene expression and phytohormone concentration in big bluestem - Frank, E.E. (Kansas State University, 2007)
While plants are typically exposed to multiple stressors in the field, studies of genome-wide gene expression and phytohormone responses in wild plant species exposed to multiple stressors are rare. Our objectives were to determine the effects of drought andrust stress on gene expression in Andropogon gerardii, the dominant grass in tallgrass prairie, and associated levels of phytohormone production. In a factorial design, plants experiencing drought or non-drought conditions were either inoculated with the rust pathogen Puccinia andropogonis or not inoculated. Gene expression was evaluated with maize microarrays. Drought-stressed plants significantly decreased expression of genes associated with photosynthesis and the hypersensitive response, while expression of genes associated with chaperones and heat-shock proteins increased. No significant differences in gene expression in response to the rust treatment were detected using a mixed model analysis of variance and false discovery rate protection, probably because of the low infection rate. Phytohormone production increased when both stresses were present. The rust treatment significantly increased benzoic acid (BA) production in the presence of drought, while the drought treatment alone significantly increased salicylic acid (SA) production. Leaf tips usually had higher levels of all phytohormones in all treatments and the leaf section evaluated had a larger effect on phytohormone level than did the treatments applied.

The saturation of N cycling in Central Plains streams: 15N experiments across a broad gradient of nitrate concentrations - O'Brien, J.M.; W. K. Dodds; Wilson, K.C.; Murdock, J.N.; Eichmiller, J. (Biogeochemistry, 2007)
We conducted 15NO 3 − stable isotope tracer releases in nine streams with varied intensities and types of human impacts in the upstream watershed to measure nitrate (NO 3 − ) cycling dynamics. Mean ambient NO 3 − concentrations of the streams ranged from 0.9 to 21,000 μg l−1 NO 3 − –N. Major N-transforming processes, including uptake, nitrification, and denitrification, all increased approximately two to three orders of magnitude along the same gradient. Despite increases in transformation rates, the efficiency with which stream biota utilized available NO 3 − -decreased along the gradient of increasing NO 3 − . Observed functional relationships of biological N transformations (uptake and nitrification) with NO 3 − concentration did not support a 1st order model and did not show signs of Michaelis–Menten type saturation. The empirical relationship was best described by a Efficiency Loss model, in which log-transformed rates (uptake and nitrification) increase with log-transformed nitrate concentration with a slope less than one. Denitrification increased linearly across the gradient of NO 3 − concentrations, but only accounted for ∼1% of total NO 3 − uptake. On average, 20% of stream water NO 3 − was lost to denitrification per km, but the percentage removed in most streams was <5% km−1. Although the rate of cycling was greater in streams with larger NO 3 − concentrations, the relative proportion of NO 3 − retained per unit length of stream decreased as NO 3 − concentration increased. Due to the rapid rate of NO 3 − turnover, these streams have a great potential for short-term retention of N from the landscape, but the ability to remove N through denitrification is highly variable.
Keywords: denitrification; Nitrate; nitrification; Saturation; stream; Uptake

Seven years of enhanced water availability influences the physiological, structural and functional attributes of a soil microbial community - Williams, M.A.; C. W. Rice (Applied Soil Ecology, 2007)
Water availability is known to influence many aspects of microbial growth and physiology, but less is known about how complex soil microbial communities respond to changing water status. To understand how long-term enhancement of soil water availability (without flooding) influences microbial communities, we measured the seasonal dynamics of several community-level traits following >7 years of irrigation in a drought-prone tallgrass prairie soil. From late May to mid-September, water was supplied to the irrigated treatments based on calculated plant water demand. Phospholipid fatty acids (PLFA) were used to assess changes in microbial community structure and physiology. To assess the community-level physiological profile, microbial utilization of BIOLOG substrates was determined. After incubation for 2 days, the distribution of added 13C-glucose in microbial and respired pools was used as an index of substrate utilization efficiency. We also measured the relative contribution of fungi and bacteria to soil microbial biomass via substrate-induced respiration (SIR). Multivariate analysis of mol% PLFA and BIOLOG substrate utilization indicated that both water availability and sampling time influenced both the physiological and structural characteristics of the soil microbial community. Specific change in biomarker PLFA revealed a decreased ratio of cyclopropyl to ω7-precursors due to water addition, suggesting community-level stresses were reduced. Over the growing season, continuously greater water availability resulted in a 53% greater ratio of fungal to bacterial biomass using SIR, and a 65% increase in fungal PLFA. The number of substrates utilized by the cultivable microbial community tended to be greater in continuously wetted soil, especially during periods of low rainfall. While water dynamics appeared to be associated with some of the shifts in microbial community activity, structural and functional changes in the community appeared to be more closely linked to the cumulative effects of water regime on ecosystem properties. Seasonality strongly influenced microbial communities. The environmental factors associated with seasonal change need to be more closely probed to better understand the drivers of community structure and function.
Keywords: Microbial community; physiology; PLFA; Stress; Substrate use efficiency; Water availability

Soil water partitioning contributes to species coexistence in tallgrass prairie - Jesse B. Nippert; Alan K. Knapp (Oikos, 2007)
The majority of tallgrass prairie root biomass is located in the upper soil layers (0–25 cm), but species differences exist in reliance on soil water at varying depths. These differences have led to the hypothesis that resource partitioning belowground facilitates species co-existence in this mesic grassland. To determine if plant water relations can be linked to soil water partitioning as a potential mechanism allowing C3 species to persist among the more dominant C4 grasses, we measured differences in the source of water-use using the isotopic signature of xylem water, volumetric soil water content at 4 depths, and leaf water potentials. Data were collected for seven species representing C4 grasses, C3 forbs and C3 shrubs over three growing seasons at the Konza Prairie (Kansas, USA) to encompass a range of natural climatic conditions. C4 grasses relied on shallow soil water (5 cm) across the growing season and had midday leaf water potentials that were highly correlated with shallow soil water regardless of soil water availability at other portions of the soil profile (20, 40 and 90 cm). In contrast, C3 species only used shallow soil water when plentiful at this depth; these species increased their dependence on soil water from greater depths as the upper soil layers dried. Structural equation models describing plant water relations were very similar for the three C4 species, whereas a unique set of models and drivers were identified for each of the C3 species. These results support soil water partitioning as a mechanism for species coexistence, as C4 species in this grassland have relatively consistent dependence on water in shallow soil layers, whereas C3 species show niche differentiation in water use strategies to avoid competition with C4 grasses for water in shallow soil layers when this resource is limiting and leaf water stress is high.

Spatial variation in predation attempts on artificial snakes in a fire-disturbed tallgrass prairie - Wilgers, D.J.; Horne, E.A. (Southwestern Naturalist, 2007)
The tallgrass prairie historically burned every 2 to 3 y, removing the litter layer and leaving post-burn environments inhospitable to many terrestrial species. Selection pressures, such as lack of food and shelter and increased predation, are intensified for some species over limited time periods. To quantify predation pressures on large snakes, artificial snakes were placed in recently burned and long-term unburned areas of a grassland system in northeastern Kansas. Any disturbance to the original placement of the model snake was considered a predation attempt. Statistical models were used to estimate daily survival rates of individual artificial snakes within both habitat types. A group effect (burned vs. unburned) was selected as the single top model, garnishing >93% of the support for the data. Survival estimates from this top model indicated artificial snakes in newly burned areas had significantly lower daily survival than those placed within unburned sites. Indirect evidence from destroyed artificial snakes indicated raptors were a major predator on large snakes. Overall herpetofaunal activity in burned areas was low during the first 20 d post-burn, with increasing activity throughout the rest of the season. However, activity within unburned areas was constant throughout the spring. Burning tallgrass prairie likely increases predation pressure on large snakes in the area for 1 to 2 mo following the burn due to the lack of cover against aerial predators.

Stream insect occupancy-frequency patterns and metapopulation structure - Heatherly, T.; M.R. Whiles; D.J. Gibson; Scott. L. Collins; Huryn, A.D.; Jackson, J.K.; Palmer, M.A. (Oecologia, 2007)
An understanding of the distribution patterns of organisms and the underlying factors is a fundamental goal of ecology. One commonly applied approach to visualize these is the analysis of occupancy-frequency patterns. We used data sets describing stream insect distributions from different regions of North America to analyze occupancy-frequency patterns and assess the effects of spatial scale, sampling intensity, and taxonomic resolution on these patterns. Distributions were dominated by satellite taxa (those occurring in ≤10% of sites), whereas the occurrence of core taxa (occurring in ≥90% of sites) determined the overall modality of occupancy-frequency patterns. The proportions of satellite taxa increased with spatial scale and showed positive relationships with sampling intensity (r 2=0.74–0.96). Furthermore, analyses of data sets from New York (USA) showed that generic-level assessments underestimated the satellite class and occasionally shifted occupancy-frequency distributions from unimodal to bimodal. Our results indicate that, regardless of species- or generic-level taxonomy, stream insect communities are characterized by satellite species and that the proportion of satellite species increases with spatial scale and sampling intensity. Thus, niche-based models of occupancy-frequency patterns better characterize stream insect communities than metapopulation models such as the core-satellite species hypothesis.
Keywords: aquatic insect; Core-satellite; Distribution; Sampling intensity; spatial scale

Supply, bioavailability, and source of dissolved organic carbon in a prairie stream - Eichmiller, J.J. (Kansas State University, 2007)

Trophic state, eutrophication, and nutrient criteria in streams - W. K. Dodds (Trends in Ecology and Evolution, 2007)
Trophic state is the property of energy availability to the food web and defines the foundation of community integrity and ecosystem function. Describing trophic state in streams requires a stoichiometric (nutrient ratio) approach because carbon input rates are linked to nitrogen and phosphorus supply rates. Light determines the source of carbon. Cross system analyses, small experiments and ecosystem level manipulations have recently advanced knowledge about these linkages, but not to the point of building complex predictive models that predict all effects of nutrient pollution. Species diversity could indicate the natural distribution of stream trophic status over evolutionary time scales. Delineation of factors that control trophic state and relationships with biological community properties allows determination of goals for management of stream biotic integrity.

Are soil mite assemblages structured by the identity of native and invasive alien grasses? - John, M.G.; Wall, D.H.; Hunt, H.W. (Ecology, 2006)
Associations between plants and animals in aboveground communities are often predictable and specific. This has been exploited for the purposes of estimating the diversity of animal species based on the diversity of plant species. The introduction of invasive alien plants into an ecosystem can result in dramatic changes in both the native plant and animal assemblages. Few data exist at the species level to determine whether belowground animal assemblages share the same degree of association to plants. The hypotheses that soil mites (Acari) form assemblages specifically associated with different native grass species in an unmanipulated natural ecosystem and that invasive alien grasses will impact soil mite assemblage composition in this setting were tested. Soil mites sampled beneath five native and two invasive alien species of grasses at the Konza Prairie Biological Station, Kansas, USA, were similarly abundant, species rich, diverse, and taxonomically distinct. No mite species had affinities for a specific grass species. There was no evidence from analysis of similarity, canonical correspondence analysis, or a nonparametric assemblage analysis that the assemblage composition of soil mites was specific to grass species. Results suggest that soil mite assemblages were more related to characteristics of the plant assemblage as a whole or prevailing soil conditions. The most recent invasive alien grass did not support a successionally younger mite fauna, based on the ratio of mesostigmatid to oribatid mites, and neither of the two invasive grasses influenced mite assemblage structure, possibly because they had not yet substantially altered the soil environment. Our results suggest that extrapolations of soil mite diversity based on assumptions of plant specificity would be invalid.

An automatic activity-monitoring system for small mammals under natural conditions - Rehmeier, R.L.; Kaufman, G.A.; D.W. Kaufman (Journal of Mammalogy, 2006)
Small mammals spend a majority of their lives in shelter sites such as belowground burrows. Understanding temporal patterns of burrow use would provide valuable information about the influence of physiological and environmental factors on activity patterns. To examine patterns of burrow use, we developed a system that automatically monitors activity of deer mice (Peromyscus maniculatus) at artificial burrows in tallgrass prairie. The automatic activity-monitoring system is composed of a passive integrated transponder (PIT)–tag transceiver that reads the identification tags of individuals and an infrared trail monitor that confirms movements in and out of artificial burrows. We PIT-tagged and monitored nightly activity of <90 deer mice on Konza Prairie Biological Station in northeastern Kansas from July 2003 to December 2004. The monitoring system allowed us to examine individual variation in activity relative to sex, parental attendance, and early exploration by young. We also discuss advantages and disadvantages of the system compared to other activity-monitoring techniques, so that researchers might develop similar systems for other study species.
Keywords: deer mouse; kansas; passive integrated transponder (PIT) tag; Peromyscus maniculatus; tallgrass prairie; time of activity

Belowground bud banks increase along a precipitation gradient of the North American Great Plains: a test of the meristem limitation hypothesis - Dalgleish, H.J.; D.C. Hartnett (New Phytologist, 2006)
• In perennial grasslands, the below-ground population of meristems (bud bank) plays a fundamental role in plant population dynamics. Here, we tested the ‘meristem limitation hypothesis’ prediction – that bud banks increase along an increasing precipitation/productivity gradient in North American grasslands – and assessed the seasonal dynamics of bud banks. • We sampled bud and stem populations quarterly at six sites across a 1100 km gradient in central North America. • Bud banks increased with average annual precipitation, which explained 80% of the variability between the sites. In addition, seasonal changes in grass bud banks were surprisingly similar across a 2.5-fold range in precipitation and a 4-fold range of productivity: densities peaked in March, decreased in June and increased slightly in September. • Increasing meristem limitation may constrain vegetation responses to inter-annual changes in resources. An important consequence of this is that biomes with large bud banks may be the most responsive to environmental change. If meristem limitation represents an important constraint on productivity responses to environmental variability, then bud banks must be considered in developing predictive models for grassland responses to environmental change.

Biologic cycling of silica across a grassland bioclimosequence - Blecker, S.W.; McCulley, R.L.; Chadwick, O.A.; Kelly, E.F. (Global Biogeochemical Cycles, 2006)
[1] The dynamics of biologic Si cycling in grassland ecosystems are largely unknown and likely to impact mineral weathering rates regionally and diatom productivity globally; key regulatory processes in the global Si cycle are closely tied to the global carbon cycle. Across a bioclimatic sequence spanning major grassland ecosystems in the Great Plains, soil biogenic silica depth distributions are similar to that of soil organic carbon; however, unlike soil organic carbon, quantities of soil biogenic silica decrease with increasing precipitation, despite an increase in annual biogenic inputs through litterfall across the same gradient. Though comprising only 1–3% of the total Si pool, faster turnover of biogenic Si and annual cycling by grasses should positively impact mineral dissolution. Our results suggest that the largest reservoir of biogenic Si in terrestrial ecosystems resides in soils, and emphasize the potential significance of grasslands in the global biogeochemical cycle of Si.

Bud banks of perennial savanna grasses in Botswana - D.C. Hartnett; Setshogo, M.P.; Dalgleish, H.J. (African Journal of Ecology, 2006)
Three semi-arid savanna grasses in Botswana (Stipagrostis uniplumis, Eragrostis lehmanniana, and Aristida stipitata) were sampled to quantify their belowground bud banks during the dormant season and to estimate their relative allocation to vegetative and sexual reproduction. Bud banks of these African perennial caespitose grasses were also compared with four perennial caespitose grasses of semi-arid North American grasslands. The three African grasses each maintained approximately two buds per tiller and showed a high percentage (88–99%) of tillers producing seed. Only E. lehmanniana produced new aerial tillers from axillary buds at elevated nodes on the stem as well as from the belowground bud bank. Compared with species of North American grasslands, these African grasses produced fewer belowground buds but showed a much higher percentage of tillers producing seed. These patterns indicate relatively greater belowground meristem limitation, lower allocation to vegetative reproduction (tillering) and higher allocation to seed reproduction in these African grasses, although studies of more species are needed to assess the generality of this pattern. The management of savannas in ways that favour the maintenance of a reserve population of belowground buds may increase the ability of grasses to respond to pulses of resource availability, increase their compensatory growth capacity following grazing or drought, and decrease the invasibility of these plant communities by exotic species, whereas maintaining allocation to sexual reproduction may be important for conserving genetic variation and enhancing their capacity to adapt to environmental change.
Keywords: clonal plants; meristems; Plant demography; reproductive strategy; Vegetative reproduction

Canopy chlorophyll estimation with hyperspectral remote sensing - Gao, J. (Kansas State University, 2006)
In this research, proximal measurements of hyperspectral reflectance were used to develop models for estimating chlorophyll content in tallgrass prairie at leaf and canopy scales. Models were generated at the leaf scale and then extended to the canopy scale. Three chlorphyll estimation models were developed, one based on reflectance spectra and two derived from derivative transformations of the reflectance spectra. The triangle chlorophyll index (TCI) model was derived from the reflectance spectrum, whereas the first and second derivative indices (FDI and SDI) models were developed from the derivative transformed spectra. The three models were found to be well- correlated with the chlorophyll content measured with solvent extraction. The result indicated that the three models were effective for the leaf scale estimates of chlorophyll content. The three chlorophyll models developed at the leaf scale were further extended to the canopy scale and fine-scale images. The three models were found to be conditionally effective for estimating canopy chlorophyll content. The TCI model was more effective in dense vegetation, and the FDI and SDI models were better in sparser vegetation. This research suggests that the extension of chlorophyll models from the leaf scale to canopy scale is complex and affected not only by soil background, but also by canopy structure and components
Keywords: canopy; chlorophyll content; hyperspectrum; remote sensing

Climate change effects on plant disease: from genes to ecosystems - Garrett, K.A.; Dendy, S.P.; Frank, E.E.; Rouse, M.N.; Travers, S.E. (Annual Review of Phytopathology, 2006)
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 pathosystem-specific 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.

The coevolution of society and invasivespecies: Sericea lespedeza in the Kansas Flint Hills - Cline, D. (Kansas State University, 2006)

A comparison of the reproductive systems of the invasive Lespedeza cuneata (Dum.-Cours.) G. Don (Fabaceae) with three native congeners in the Flint Hills region of the tallgrass prairie - Woods, T.M. (Kansas State University, 2006)

A comparison of the species-timerelationship across ecosystems and taxonomic groups - White, E.P.; P. Adler; Lauenroth, W.K.; Gill, R.A.; Greenberg, D.; Kaufman, D.M.; Rassweiler, A.; Rusak, J.A.; M. A. Smith; Steinbeck, J.; Waide, R.B.; Yao, J. (Oikos, 2006)
The species–time relationship (STR) describes how the species richness of a community increases with the time span over which the community is observed. This pattern has numerous implications for both theory and conservation in much the same way as the species–area relationship (SAR). However, the STR has received much less attention and to date only a handful of papers have been published on the pattern. Here we gather together 984 community time-series, representing 15 study areas and nine taxonomic groups, and evaluate their STRs in order to assess the generality of the STR, its consistency across ecosystems and taxonomic groups, its functional form, and its relationship to local species richness. In general, STRs were surprisingly similar across major taxonomic groups and ecosystem types. STRs tended to be well fit by both power and logarithmic functions, and power function exponents typically ranged between 0.2 and 0.4. Communities with high richness tended to have lower STR exponents, suggesting that factors increasing richness may simultaneously decrease turnover in ecological systems. Our results suggest that the STR is as fundamental an ecological pattern as the SAR, and raise questions about the general processes underlying this pattern. They also highlight the dynamic nature of most species assemblages, and the need to incorporate time scale in both basic and applied research on species richness patterns.

Controls of nitrogen spiraling in Kansas streams - O'Brien, J.M. (Kansas State University, 2006)

Controls on nutrients across a prairie stream watershed: Land use and riparian cover effects - W. K. Dodds; Oakes, R.M. (Environmental Management, 2006)
Nutrient inputs generally are increased by human-induced land use changes and can lead to eutrophication and impairment of surface waters. Understanding the scale at which land use influences nutrient loading is necessary for the development of management practices and policies that improve water quality. The authors assessed the relationships between land use and stream nutrients in a prairie watershed dominated by intermittent stream flow in the first-order higher elevation reaches. Total nitrogen, nitrate, and phosphorus concentrations were greater in tributaries occupying the lower portions of the watershed, closely mirroring the increased density of row crop agriculture from headwaters to lower-elevation alluvial areas. Land cover classified at three spatial scales in each sub-basin above sampling sites (riparian in the entire catchment, catchment land cover, and riparian across the 2 km upstream) was highly correlated with variation in both total nitrogen (r2 = 53%, 52%, and 49%, respectively) and nitrate (r2 = 69%, 65%, and 56%, respectively) concentrations among sites. However, phosphorus concentrations were not significantly associated with riparian or catchment land cover classes at any spatial scale. Separating land use from riparian cover in the entire watershed was difficult, but riparian cover was most closely correlated with in-stream nutrient concentrations. By controlling for land cover, a significant correlation of riparian cover for the 2 km above the sampling site with in-stream nutrient concentrations could be established. Surprisingly, land use in the entire watershed, including small intermittent streams, had a large influence on average downstream water quality although the headwater streams were not flowing for a substantial portion of the year. This suggests that nutrient criteria may not be met only by managing permanently flowing streams.
Keywords: nitrogen; Phosphorus; Prairie watershed; Riparian; water quality

Convergence and contingency in production-precipitation relationships in North American and South African C4 grasslands - Alan K. Knapp; Burns, C.E.; Fynn, R.W.S.; Kirkman, K.P.; Morris, C.D.; M.D. Smith (Oecologia, 2006)
Mesic grasslands in North America and South Africa share many structural attributes, but less is known of their functional similarities. We assessed the control of a key ecosystem process, aboveground net primary production (ANPP), by interannual variation in precipitation amount and pattern via analysis of data sets (15- and 24-year periods) from long-term research programs on each continent. Both sites were dominated by C4 grasses and had similar growing season climates; thus, we expected convergence in precipitation–ANPP relationships. Lack of convergence, however, would support an alternative hypothesis—that differences in evolutionary history and purportedly greater climatic variability in South Africa fundamentally alter the functioning of southern versus northern hemisphere grasslands. Neither mean annual precipitation nor mean ANPP differed between the South African and North American sites (838 vs. 857 mm/year, 423.5 vs. 461.4 g/m2 respectively) and growing season precipitation–ANPP relationships were similar. Despite overall convergence, there were differences between sites in how the seasonal timing of precipitation affected ANPP. In particular, interannual variability in precipitation that fell during the first half of the growing season strongly affected annual ANPP in South Africa (P < 0.01), but was not related to ANPP in North America (P = 0.098). Both sites were affected similarly by late season precipitation. Divergence in the seasonal course of available soil moisture (chronically low in the winter and early spring in the South African site vs. high in the North American site) is proposed as a key contingent factor explaining differential sensitivity in ANPP to early season precipitation in these two grasslands. These long-term data sets provided no support for greater rainfall, temperature or ANPP variability in the South African versus the North American site. However, greater sensitivity of ANPP to early season precipitation in the South African grassland suggests that future patterns of productivity may be more responsive to seasonal changes in climate compared with the North American site.
Keywords: climate; Evolutionary history; Net primary production; Precipitation; soil moisture

Determining ecoregional reference conditions for nutrients, secchi depth, and chlorophyll a in Kansas lakes and reservoirs - W. K. Dodds; Carney, E.; Angelo, R.T. (Lake and Reservoir Management, 2006)
Baseline environmental conditions are a critical consideration in the development of scientifically defensible aquatic nutrient criteria. We applied three methods to ecoregionally stratified data to determine reference conditions in Kansas lakes and reservoirs with respect to total phosphorus, total nitrogen, Secchi depth, and planktonic chlorophyll a (chl a). First, minimally developed lake/watershed units were identified based on existing geographical databases and visual basin surveys. Lakes and reservoirs in these watersheds were considered minimally-to-least impacted “reference” waters. Second, median nutrient, Secchi depth, and chl a values were determined for the best one-third of lakes and reservoirs and applied as indicators of reference condition (trisection). Third, a regression-based extrapolation method was applied to estimate water quality conditions in the absence of anthropogenic influences. The first method suggested no ecoregional effect on the trophic status of minimally impacted reference water bodies, whereas the other two methods indicated some significant ecoregional differences. Lack of ecoregional effect in reference bodies could indicate that differences were driven by anthropogenic influences rather than natural regional characteristics. Reference conditions, as determined by these three methods, broadly agreed for all parameters and were generally at or less than literature values for the mesotrophic-eutrophic threshold for lakes and reservoirs worldwide. Reference values for total phosphorus were primarily less than levels commonly associated with cyanobacterial blooms. Overall, the data suggest that multiple methods can be used to determine reference condition, and that in Kansas lakes and reservoirs reference condition corresponds to mesotrophic state.
Keywords: ecoregion; eutrophication; nitrogen; nutrient criteria; Phosphorus

Development of taxon-specific markers for high-throughput screening of microbial-feeding nematodes - Jones, K.L.; Todd, T.C.; Herman, M.A. (Molecular Ecology Notes, 2006)
In an effort to assess the taxonomic identity of large-scale samplings of nematodes from the Konza Tallgrass Prairie, we sequenced a portion of the 18S rRNA gene and its associated internally transcribed spacer (ITS1) from 74 nematodes encompassing four taxonomic families. From these sequences, we have developed a series of molecular probes to distinguish 16 distinct microbivorous nematode taxa. Using a combination of low power microscopy and taxon-specific real-time probes, the 74 nematodes were correctly assigned to their respective taxonomic groups. This optimized method provides a high-throughput assay to determine nematode identities across larger data sets.
Keywords: 18S rRNA; 5′ nuclease assaym; Nematoda; real-time PCR; Taqman

Does plant species co-occurrence influence soil mite diversity? - John, M.G.; Wall, D.H.; Behan-Pelletier, V.M. (Ecology, 2006)
Few studies have considered whether plant taxa can be used as predictors of belowground faunal diversity in natural ecosystems. We examined soil mite (Acari) diversity beneath six grass species at the Konza Prairie Biological Station, Kansas, USA. We tested the hypotheses that soil mite species richness, abundance, and taxonomic diversity are greater (1) beneath grasses in dicultures (different species) compared to monocultures (same species), (2) beneath grasses of higher resource quality (lower C:N) compared to lower resource quality, and (3) beneath heterogeneous mixes of grasses (C3 and C4 grasses growing together) compared to homogeneous mixes (C3 or C4 grasses) using natural occurrences of plant species as treatments. This study is the first to examine the interaction between above- and belowground diversity in a natural setting with species-level resolution of a hyper-diverse taxon. Our results indicate that grasses in diculture supported a more species and phylogenetically rich soil mite fauna than was observed for monocultures and that this relationship was significant at depth but not in the upper soil horizon. We noted that mite species richness was not linearly related to grass species richness, which suggests that simple extrapolations of soil faunal diversity based on plant species inventories may underestimate the richness of associated soil mite communities. The distribution of mite size classes in dicultures was considerably different than those for monocultures. There was no difference in soil mite richness between grass combinations of differing resource quality, or resource heterogeneity.

Ecological genomics and epidemiology - Garrett, K.A.; Hulbert, S.H.; Leach, J.E.; Travers, S.E. (European Journal of PlantPathology, 2006)
The huge amount of genomic data now becoming available offers both opportunities and challenges for epidemiologists. In this “preview” of likely developments as the field of ecological genomics evolves and merges with epidemiology, we discuss how epidemiology can use new information about genetic sequences and gene expression to form predictions about epidemic features and outcomes and for understanding host resistance and pathogen evolution. DNA sequencing is now complete for some hosts and several pathogens. Microarrays make it possible to measure gene expression simultaneously for thousands of genes. These tools will contribute to plant disease epidemiology by providing information about which resistance or pathogenicity genes are present in individuals and populations, what genes other than those directly involved in resistance and virulence are important in epidemics, the role of the phenotypic status of hosts and pathogens, and the role of the status of the environmental metagenome. Conversely, models of group dynamics supplied by population biology and ecology may be used to interpret gene expression within individual organisms and in populations of organisms. Genomic tools have great potential for improving understanding of resistance gene evolution and the durability of resistance. For example, DNA sequence analysis can be used to evaluate whether an arms race model of co-evolution is supported. Finally, new genomic tools will make it possible to consider the landscape ecology of epidemics in terms of host resistance both as determined by genotype and as expressed in host phenotypes in response to the biotic and abiotic environment. Host phenotype mixtures can be modeled and evaluated, with epidemiological predictions based on phenotypic characteristics such as physiological age and status in terms of induced systemic resistance or systemic acquired resistance.

The ecological significance of tallgrass prairie arthropods - M.R. Whiles; Charlton, R.E. (Annual Review of Entomology, 2006)
Tallgrass prairie (TGP) arthropods are diverse and abundant, yet they remain poorly documented and there is still much to be learned regarding their ecological roles. Fire and grazing interact in complex ways in TGP, resulting in a shifting mosaic of resource quantity and quality for primary consumers. Accordingly, the impacts of arthropod herbivores and detritivores are expected to vary spatially and temporally. Herbivores generally do not control primary production. Rather, groups such as grasshoppers have subtle effects on plant communities, and their most significant impacts are often on forbs, which represent the bulk of plant diversity in TGP. Belowground herbivores and detritivores influence root dynamics and rhizosphere nutrient cycling, and above- and belowground groups interact through plant responses and detrital pathways. Large-bodied taxa, such as cicadas, can also redistribute significant quantities of materials during adult emergences. Predatory arthropods are the least studied in terms of ecological significance, but there is evidence that top-down processes are important in TGP.

Effect of litter accumulation on seed predation in three prairie types - Reed, A.W.; Kaufman, G.A.; D.W. Kaufman (American Midland Naturalist, 2006)

Effects of burn regimes ontallgrass prairie herpetofaunal species diversity and communitycomposition in the Flint Hills, Kansas - Wilgers, D.J.; Horne, E.A. (Journal of Herpetology, 2006)
The Flint Hills region of Kansas is the largest contiguous area of tallgrass prairie remaining today. Historically, the tallgrass prairie burned every 2–3 yr on average, but current land managers have altered burn regimes, resulting in a range of habitats from annually burned to long-term unburned. We used drift fence/funnel trap arrays and coverboards to estimate species richness, evenness, and diversity of herpetofauna within three different burn regimes: annual, 4-yr, and long-term unburned at Konza Prairie Biological Station, Riley County, Kansas. During the spring and fall of 2003–2004, 315 individuals from 20 species were captured across all burn regimes. Herpetofaunal species richness, evenness, and diversity estimates were not different between the three burn treatments. However, because of species-specific responses to individual burn regimes, community composition was significantly different between the habitats (χ2 = 158.19, df = 20, P < 0.001). Four species exhibited preferences among burn regimes, which differed significantly from independent assortment, with Eumeces obsoletus and Phrynosoma cornutum preferring annual burn treatments, Scincella lateralis preferring 4-yr burn treatments, and Diadophis punctatus preferring long-term unburned treatments. Species-specific responses were likely because of changes in vegetation structure and microhabitat (temperature and moisture content) created through different frequencies of fire disturbances. Maximizing large-scale herpetofaunal diversity across the Flint Hills' rangelands could be accomplished by creating a large number of small scale habitat types through a mosaic style burning plan.

Effects of floods on fish assemblages in an intermittent prairie stream - Franssen, N.R.; K. B. Gido; Strakosh, T.R.; Bertrand, K.N.; Franssen, C.M.; Paukert, C.P.; Pitts, K.L.; Guy, C.S.; Tripe, J.A.; Shrank, S.J. (Freshwater Biology, 2006)
1. Floods are major disturbances to stream ecosystems that can kill or displace organisms and modify habitats. Many studies have reported changes in fish assemblages after a single flood, but few studies have evaluated the importance of timing and intensity of floods on long-term fish assemblage dynamics. 2. We used a 10-year dataset to evaluate the effects of floods on fishes in Kings Creek, an intermittent prairie stream in north-eastern, Kansas, U.S.A. Samples were collected seasonally at two perennial headwater sites (1995–2005) and one perennial downstream flowing site (1997–2005) allowing us to evaluate the effects of floods at different locations within a watershed. In addition, four surveys during 2003 and 2004 sampled 3–5 km of stream between the long-term study sites to evaluate the use of intermittent reaches of this stream. 3. Because of higher discharge and bed scouring at the downstream site, we predicted that the fish assemblage would have lowered species richness and abundance following floods. In contrast, we expected increased species richness and abundance at headwater sites because floods increase stream connectivity and create the potential for colonisation from downstream reaches. 4. Akaike Information Criteria (AIC) was used to select among candidate regression models that predicted species richness and abundance based on Julian date, time since floods, season and physical habitat at each site. At the downstream site, AIC weightings suggested Julian date was the best predictor of fish assemblage structure, but no model explained >16% of the variation in species richness or community structure. Variation explained by Julian date was primarily attributed to a long-term pattern of declining abundance of common species. At the headwater sites, there was not a single candidate model selected to predict total species abundance and assemblage structure. AIC weightings suggested variation in assemblage structure was associated with either Julian date or local habitat characteristics. 5. Fishes rapidly colonised isolated or dry habitats following floods. This was evidenced by the occurrence of fishes in intermittent reaches and the positive association between maximum daily discharge and colonisation events at both headwater sites. 6. Our study suggests floods allow dispersal into intermittent habitats with little or no downstream displacement of fishes. Movement of fishes among habitats during flooding highlights the importance of maintaining connectivity of stream networks of low to medium order prairie streams.

Effects of prescribed burns and bison (Bos bison)grazing on breeding bird abundances in tallgrass prairie - Powell, A.F.L.A. (Auk, 2006)
Grassland birds have declined more than any other avian assemblage in North America, with nearly every species showing negative population trends. In the Flint Hills of Kansas, the largest remnant of the tallgrass prairie biome, annual spring burning of rangeland has recently replaced burning every 2–3 years. I examined effects of different burning and bison (Bos bison) grazing regimes on June abundances of seven bird species using a 23-year data set from the Konza Prairie Biological Station. Fire significantly affected the abundances of six of the seven species. Effects varied among species but, notably, four grass-dependent species—Grasshopper Sparrow (Ammodramus savannarum), Henslow’s Sparrow (A. henslowii), Dickcissel (Spiza americana), and Eastern Meadowlark (Sturnella magna)— and the shrub-dependent Bell’s Vireo (Vireo bellii)—were least abundant or absent at sites in the breeding season immediately following burning. Upland Sandpipers (Bartramia longicauda) were most abundant at sites in the season following burning, whereas Brown-headed Cowbirds (Molothrus ater) exhibited no significant response. Bison grazing increased abundance of Upland Sandpiper and Grasshopper Sparrow, nearly eliminated Henslow’s Sparrow, and (in combination with recent fire) lowered the abundance of Dickcissel. Although fire and grazing are natural forces that maintain tallgrass prairie, their action was, until recently, intermittent and patchy, providing grassland birds with a variety of levels of disturbance. If the vast Flint Hills prairie is to serve as a grassland bird stronghold, the region-wide practice of annual burning with intensive grazing must be replaced with alternatives that restore heterogeneity to the landscape.

Effects of rangeland management on community dynamics of the herpetofauna of the tallgrass prairie - Wilgers, D.J.; Horne, E.A.; Sandercock, B.K.; Volkmann, A.W. (Herpetologica, 2006)
The Flint Hills of Kansas and Oklahoma are the largest remaining tracts of tallgrass prairie in North America. This area has undergone major changes in land management practices in the past 30 years. Traditional season-long cattle stocking with variable burn schedules has diversified to include intensive-early cattle stocking accompanied by annual burning. To understand how different land management practices affect the herpetofauna of a tallgrass prairie, we used mark-recapture statistics to analyze herpetofaunal community dynamics. We analyzed survey data collected over a 15-year time span (1989–2003) from a rangeland site in Cowley County, KS, USA. A modified Jolly-Seber open population model, POPAN-5, was used to estimate four community parameters: probability of species loss (φ′), probability of detection (P), probability of entry (Pent), and species richness (N). The top models included burn status as a covariate for species loss rate, while cattle stocking received moderate support as a covariate. Rates of species loss were higher during burn years (φ′  =  0.04, 95% CI: 0.02 to 0.08) than nonburn years (φ′  =  0.00, 95% CI: 0.00 to 0.01). Analysis of the impacts of different management practices was difficult due to confounding effects of changes in both burning and grazing. Declines in species richness tended to be steepest during a period of season-long stocking, but results were not statistically significant. Though our limited data set does not allow us to draw strong conclusions on the effects of land management on herpetofaunal populations, the mark-recapture models illustrated in our study should prove to be a valuable tool in future analyses of similar data.
Keywords: Amphibians; Flint Hills; Mark-recapture; POPAN; Reptiles; Species loss

Effects of season of fire and fire type on the demography and abundance of clonal shrubs in tallgrass prairie - K.M. Hajny (Kansas State University, 2006)

Enhancing collaborative research on the environment in sub-Saharan Africa - D.C. Hartnett; Semazzi, F.H.M. (OISE National Science Foundation Report, 2006)

Estimation of demographic parameters from liveencounter data: a summary review - Sandercock, B.K. (Journal of Wildlife Management, 2006)
Estimation of demographic parameters is central to research questions in wildlife management, conservation, and evolutionary ecology. I review the 7 major classes of mark–recapture models that investigators can use to estimate apparent survival and other parameters from live-encounter data. Return rates are the product of 4 probabilities: true survival (S), site fidelity (F), site propensity (δ), and true detection (p*). Cormack-Jolly-Seber (CJS) models improve upon return rates by separating apparent survival (ϕ = S × F) from the probability of encounter (p = δ × p*). The main drawback to mark–recapture models based on live-encounter data is that the complement of apparent survival (1 − ϕ) includes losses to mortality and to permanent emigration, and these 2 ecological processes are difficult to disentangle. Advanced mark–recapture models require additional sampling effort but estimate apparent survival with greater precision and less bias, and they also offer estimates of other useful demographic parameters. Time-since-marking or transient models control for individuals not encountered after the occasion they are first marked, a common feature of wildlife populations. Temporal symmetry models combine forward- and reverse-time modeling to estimate recruitment (f) and the finite rate of population change (λ). Multi-strata models include dynamic categorical information and offer state-specific estimates of apparent survival and encounter rates, as well as probabilities of changing states (Ψ). Robust design models subdivide sampling occasions into shorter periods, and they partition encounter rates (p) into estimates of temporary emigration (γ = 1 − δ) and true detection (p*). Joint models combine live encounters with other sources of information, including dead-recovery data, and decompose apparent survival into estimates of true survival (S) and site fidelity (F). Cormack-Jolly-Seber and multi-strata models have a large literature, but many of the advanced models have not yet received widespread use. In the future, wildlife ecologists should design field studies that take advantage of the best possible statistical procedures now that a range of alternative models and software tools are available.
Keywords: apparent survival; Cormack-Jolly-Seber; joint model; multi-strata; population change; recruitment; return rate; robust design; temporal symmetry; transient

Eutrophication and trophic state in rivers and streams - W. K. Dodds (Limnology and Oceanography, 2006)
Many natural streams are net heterotrophic, so I propose that trophic state be divided into autotrophic and heterotrophic state. This division allows consideration of the influence of external carbon sources as well as nutrients such as nitrogen and phosphorus. Empirical results suggest that phosphorus and nitrogen are the most important nutrients regulating autotrophic state in flowing waters and that benthic algal biomass is positively correlated to gross primary production in streams. Reference (minimally influenced by human activities) nutrient concentrations and correlations of nutrients with algal biomass are used to characterize reference distributions of stream autotrophic state. Only when reference nutrient concentrations are in the upper one third of those expected in the United States, is maximum benthic chlorophyll projected to exceed 100 mg m!2 (a concentration commonly used to indicate nuisance levels) "30% of the time. Average reference nutrient concentrations lead to sestonic chlorophyll concentrations above those considered typical of eutrophic lakes ("8 mg m!3 ) less than half the time. Preliminary analysis suggests that autotrophic state is variable in small pristine streams because it is influenced by canopy cover (light), but heterotrophic state is less variable because it can be based on allochthonous or autochthonous production. Nitrogen and phosphorus enrichment can influence both heterotrophic and autotrophic state, and these effects could cascade to animal communities. Stoichiometry should be considered because carbon, nitrogen, and phosphorus are all involved in trophic state. The proposed definition of trophic state offers a starting conceptual framework for such considerations.

Evaluation of MODIS NPP and GPP products across multiple biomes - Turner, D.P.; Ritts, W.D.; Cohen, W.B.; Gower, S.T.; Running, SW.; Zhao, M.; Costa, M.H.; Kirschbaum, A.; J.M. Ham; Saleska, S.; Ahl, D.E. (Remote Sensing of Environment, 2006)
Estimates of daily gross primary production (GPP) and annual net primary production (NPP) at the 1 km spatial resolution are now produced operationally for the global terrestrial surface using imagery from the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor. Ecosystem-level measurements of GPP at eddy covariance flux towers and plot-level measurements of NPP over the surrounding landscape offer opportunities for validating the MODIS NPP and GPP products, but these flux measurements must be scaled over areas on the order of 25 km2 to make effective comparisons to the MODIS products. Here, we report results for such comparisons at 9 sites varying widely in biome type and land use. The sites included arctic tundra, boreal forest, temperate hardwood forest, temperate conifer forest, tropical rain forest, tallgrass prairie, desert grassland, and cropland. The ground-based NPP and GPP surfaces were generated by application of the Biome-BGC carbon cycle process model in a spatially-distributed mode. Model inputs of land cover and leaf area index were derived from Landsat data. The MODIS NPP and GPP products showed no overall bias. They tended to be overestimates at low productivity sites — often because of artificially high values of MODIS FPAR (fraction of photosynthetically active radiation absorbed by the canopy), a critical input to the MODIS GPP algorithm. In contrast, the MODIS products tended to be underestimates in high productivity sites — often a function of relatively low values for vegetation light use efficiency in the MODIS GPP algorithm. A global network of sites where both NPP and GPP are measured and scaled over the local landscape is needed to more comprehensively validate the MODIS NPP and GPP products and to potentially calibrate the MODIS NPP/GPP algorithm parameters.
Keywords: biomes; Global; Gross primary production; Landsat; MODIS; Monitoring; Net primary production; Validation

An evaluation of single-pass versus three-pass backpack electrofishing to estimate trends in species abundance and richness in prairie streams - Bertrand, K.N.; K. B. Gido; Guy, C.S. (Transactions of the Kansas Academy of Science, 2006)
Backpack electrofishing is a common method used to compare total species richness and relative abundance of stream fishes across space and time. However, as with any sampling method, it is important to evaluate the sampling effort necessary to capture patterns of variation in fish assemblage structure across samples. Thus, we evaluated the efficacy of single-pass versus multiple-pass backpack electrofishing for minnows and darters in intermittent prairie streams. We found that in 14 of 19 three-pass electrofishing samples, we detected all species during the first pass. The samples where we missed species on the first pass were in pools with six to nine species, suggesting a single-pass sample worked best for pools with lower species richness. We also found that both the raw abundance (i.e., catch rates) and rank abundance of four common species based on the first pass is highly concordant with the second and third passes. Nevertheless, differences in capture efficiency varied by species and density. In particular, our ability to deplete a species from a stream pool was highly variable when fish densities were low, and for Phoxinus erythrogaster, it was variable across all densities. Overall, our data suggest single-pass electrofishing can be used to detect spatial and temporal trends in abundance and species richness given standardized effort, but may not be representative of absolute population densities.
Keywords: backpack electrofishing; darters; intermittent prairie streams; minnows; sampling efficiency

Fire frequency and mosaic burning effects on atallgrass prairie ground beetle assemblage - Cook, W.M.; Holt, R.D. (Biodiversity and Conservation, 2006)
Fire frequency has significant effects on the biota of tallgrass prairie, including mammals, vascular plants and birds. Recent concern has been expressed that widespread annual burning, sometimes in combination with heavy livestock grazing, negatively impacts the biota of remaining prairie remnants. A common management recommendation, intended to address this problem, is to create a landscape with a mosaic of different burn regimes. Pitfall trapping was used to investigate the impacts of fire pattern on the diversity and species composition of ground beetles (Coleoptera: Carabidae) at Konza Prairie Biological Station in eastern Kansas, USA. Trapping was conducted over three seasons in landscape units burned on average every 1, 4, or 20 years, and in a fourth season across the available range of vegetative structure to assess the variability of the community within the study system. In the fifth season communities were also followed immediately after two fire events to detect within-season effects of fire and to study short-term patterns of post-disturbance community assembly. Fire frequency had comparatively minimal effects on ground beetle diversity measures, and most numerically common species were observed widely across habitat and management types. Fire frequency effects were manifested primarily in changes in abundance of common species. Colonization of burned areas apparently did not occur from juxtaposed non-burned areas, but from underground or from long distances. While these results suggest that widespread annual burning of tallgrass prairie remnants may not have dramatic effects on prairie ground beetles, we urge caution regarding the application of these results to other taxa within tallgrass prairie.
Keywords: Carabidae; Fire frequency; Ground beetles; Pitfall trapping; Species richness; tallgrass prairie

Growth responses of twodominant C4 grass species to altered water availability - Swemmer, A.M.; Alan K. Knapp; M.D. Smith (InternationalJournal of Plant Sciences, 2006)
Identifying key ecophysiological traits that differ among dominant plant species and can be linked to species‐specific responses to drought would improve our ability to forecast community and ecosystem responses to global climate change. The mesic grasslands of the central plains of North America are dominated by two C4 grass species, Andropogon gerardii and Sorghastrum nutans, which purportedly differ in their tolerance of water stress. Individuals of these two species were grown in the field under rain‐out shelters and subjected to wet (watered every 2–3 d) or dry (repeatedly subjected to wilting before watering) soil moisture regimes. A range of ecophysiological traits potentially important for tolerating water stress were concurrently measured. Although few traits differed between the species in the wet treatment, several traits were identified in the dry treatment that may enable A. gerardii to better tolerate drought. These were greater allocation to roots, reduced allocation to flowering, more rapid leaf turnover, and more rapid recovery of photosynthesis after wilting. The latter two traits may be particularly important for coping with increased variability in rainfall regimes in the future and are consistent with recently documented responses of A. gerardii to experimental increases in soil moisture variability.
Keywords: Andropogon gerardii; biomass allocation; Climate change; leaf turnover; photosynthesis; Sorghastrum nutans; water stress

Herbivore impact on grassland plant diversity depends on habitat productivity and herbivore size - E.S. Bakker; Ritchie, M.E.; Olff, H.; Milchunas, D.G.; Knops, J.M.H. (Ecology Letters, 2006)
Mammalian herbivores can have pronounced effects on plant diversity but are currently declining in many productive ecosystems through direct extirpation, habitat loss and fragmentation, while being simultaneously introduced as livestock in other, often unproductive, ecosystems that lacked such species during recent evolutionary times. The biodiversity consequences of these changes are still poorly understood. We experimentally separated the effects of primary productivity and herbivores of different body size on plant species richness across a 10-fold productivity gradient using a 7-year field experiment at seven grassland sites in North America and Europe. We show that assemblages including large herbivores increased plant diversity at higher productivity but decreased diversity at low productivity, while small herbivores did not have consistent effects along the productivity gradient. The recognition of these large-scale, cross-site patterns in herbivore effects is important for the development of appropriate biodiversity conservation strategies.

Host-parasite interactions on an experimental landscape - Kosciuch, K.L. (Kansas State University, 2006)

Impact of hydroclimatic fluctuations on the soil water balance - Daly, E.; Porporato, A. (Water Resources Research, 2006)
[1] We analyze the propagation of daily fluctuations in rainfall and potential evapotranspiration to soil moisture dynamics, using a stochastic model that accounts for these two different forms of hydroclimatic variability. The pulsing, intermittent behavior of daily precipitation is described by a compound Poisson process that models the unpredictability of both frequency and amount of rainfall events, while fluctuations in potential evapotranspiration that act continuously in time are assumed to be Gaussian. The resulting model for the soil water balance is thus a stochastic differential equation, forced by a state-dependent compound Poisson noise and a multiplicative Gaussian noise. Steady state probability distribution functions (pdfs) of soil moisture are obtained analytically along with the equations for the expected water balance and its variability. The multiplicative effect of temporal fluctuations in potential evapotranspiration on soil moisture reduces the soil water losses caused by evapotranspiration compared to the case when they are not present. Most importantly, the analysis also shows that because of their different forms and state dependence the impact of rainfall variability on soil moisture dynamics is much more significant than that of potential evapotranspiration, the fluctuations of which do not affect appreciably the soil moisture statistical properties.

Intra-annual rainfallvariability and grassland productivity: can the past predictthe future - Jesse B. Nippert; Alan K. Knapp; J. M. Briggs (Plant Ecology, 2006)
Precipitation quantity has been shown to influence grassland aboveground net primary productivity (ANPP) positively whereas experimental increases in of temporal variability in water availability commonly exhibit a negative relationship with ANPP. We evaluated long term ANPP datasets from the Konza Prairie Long Term Ecological Research (LTER) program (1984–1999) to determine if similar relationships could be identified based on patterns of natural variability (magnitude and timing) in precipitation. ANPP data were analyzed from annually burned sites in native mesic grassland and productivity was partitioned into graminoid (principally C4 grasses) and forb (C3 herbaceous) components. Although growing season precipitation amount was the best single predictor of total and grass ANPP (r 2=0.62), several measures of precipitation variability were also significantly and positively correlated with productivity, independent of precipitation amount. These included soil moisture variability, expressed as CV, for June (r 2=0.45) and the mean change in soil moisture between weekly sampling periods in June and August (%wv) (r 2=0.27 and 0.32). In contrast, no significant relationships were found between forb productivity and any of the precipitation variables (p>0.05). A multiple regression model combining precipitation amount and both measures of soil moisture variability substantially increased the fit with productivity (r 2=0.82). These results were not entirely consistent with those of short-term manipulative experiments in the same grassland, however, because soil moisture variability was often positively, not negatively related to ANPP. Differences in results between long and short term experiments may be due to low variability in the historic precipitation record compared to that imposed experimentally as experimental levels of variability exceeded the natural variability of this dataset by a factor of two. Thus, forecasts of ecosystem responses to climate change (i.e. increased climatic variability), based on data constrained by natural and recent historical rainfall patterns may be inadequate for assessing climate change scenarios if precipitation variability in the future is expected to exceed current levels.
Keywords: ANPP; Climate change; grassland; Precipitation variability; soil moisture; tallgrass prairie

Life by the drop: Water as a physiological driver of the tallgrass prairie plant community - Jesse B. Nippert (Colorado State University, 2006)

MODIS land cover and LAI collection 4 product quality across nine sites in the western hemisphere - Cohen, W.B.; Maiersperger, T.K.; Turner, D.P.; Ritts, W.D.; Pflugmacher, D.; Kennedy, R.E.; Kirschbaum, A.; Running, S.W.; Costa, M.; Gower, S.T. (IEEE Transactions in Geosciences and Remote Sensing, 2006)
Global maps of land cover and leaf area index (LAI) derived from the Moderate Resolution Imaging Spectrometer (MODIS) reflectance data are an important resource in studies of global change, but errors in these must be characterized and well understood. Product validation requires careful scaling from ground and related measurements to a grain commensurate with MODIS products. We present an updated BigFoot project protocol for developing 25-m validation data layers over 49-km2 study areas. Results from comparisons of MODIS and BigFoot land cover and LAI products at nine contrasting sites are reported. In terms of proportional coverage, MODIS and BigFoot land cover were in close agreement at six sites. The largest differences were at low tree cover evergreen needleleaf sites and at an Arctic tundra site where the MODIS product overestimated woody cover proportions. At low leaf biomass sites there was reasonable agreement between MODIS and BigFoot LAI products, but there was not a particular MODIS LAI algorithm pathway that consistently compared most favorably. At high leaf biomass sites, MODIS LAI was generally overpredicted by a significant amount. For evergreen needleleaf sites, LAI seasonality was exaggerated by MODIS. Our results suggest incremental improvement from Collection 3 to Collection 4 MODIS products, with some remaining problems that need to be addressed

Modular experimental riffle-pool stream system - Matthews, W.J.; K. B. Gido; Garrett, G.P.; Gelwick, F.P.; Stewart, J.; Schaefer, J. (Transactions of the American Fisheries Society, 2006)
We describe a modular method for building a large, outdoor experimental stream system that has great flexibility for research projects in fish ecology, behavior, conservation, or management. The system has been in use for more than a decade at the University of Oklahoma Biological Station (Kingston, Oklahoma) and has been used with modification at four other research facilities in the Midwest. Here, we document the system in detail, including specifications for construction of the original system and modifications or improvements at other sites. The system uses commercially available, customized fiberglass round tank and trough units that can be configured in many different ways to create flowing pool and riffle habitats. The system appears to be a good mimic of small natural streams based on system flow rates, establishment of natural substrates and cover, stream chemistry relative to that of a natural creek, and fish behaviors. At least 39 fish species have been used successfully in 1–14-month experiments in these systems and approximately half have reproduced. The system offers great flexibility of design to experimenters, is cost effective, and may be of interest at other facilities that research basic biology, conservation, or management of stream fishes.

Molecular approach for assessing responses of microbial-feeding nematodes to burning and chronic nitrogen enrichment in a native grassland - Jones, K.L.; Todd, T.C.; Wall-Beam, J.L.; Coolon, J.D.; John M. Blair; Herman, M.A. (Molecular Ecology, 2006)
A substantial proportion of the primary productivity in grassland ecosystems is allocated belowground, sustaining an abundant and diverse community of microbes and soil invertebrates. These belowground communities drive many important ecosystem functions and are responsive to a variety of environmental changes. Nematodes, an abundant and diverse component of grassland soil communities, are particularly responsive to altered environmental conditions, such as those associated with reduced fire frequency and nitrogen enrichment, with the most consistent responses displayed by microbial-feeding nematodes. However, much of the available research characterizing nematode responses to environmental change has been carried out at the taxonomic level of family or by broad trophic categories (e.g. fungivores, bacterivores). The extent to which differential responses to environmental change occurs at the genus level or below is unclear. Therefore, the objective of this study was to use molecular methods to quantify the response of microbial-feeding nematodes, at the lowest levels of taxonomic resolution, to nitrogen enrichment and changes in fire frequency. Using sequencing and quantitative polymerase chain reaction (PCR) probes for the 18S ribosomal RNA gene and the ITS1 region, we identified 19 microbial-feeding nematode taxa across four families. When nematodes were sampled across treatments, we found that some nematode taxa within a family responded similarly to nitrogen and burning treatments, while other taxa within the same family respond quite differently. Additionally, although nematodes from different families on average responded differently to nitrogen enrichment and burning, similar responses were seen in nematode taxa that span three taxonomic families. Thus, if nematodes are to be used as indicators of environmental change, care should be taken to assess the response at the lowest taxonomic level possible.

Mycorrhizal-mediated phosphorus transfer between tallgrass prairie plants Sorghastrum nutans and Artemisia ludoviciana - G.T. Wilson; D.C. Hartnett; C. W. Rice (Functional Ecology, 2006)
1A glasshouse 32P-labelling study examined arbuscular mycorrhizal (AM)-mediated transfer of phosphorus between individuals of two tallgrass prairie species, an obligately mycotrophic grass (Sorghastrum nutans Vitm.) and a facultatively mycotrophic forb (Artemisia ludoviciana Nutt.). 2Regardless of which species served as donor, 32P was transferred between both intra- and interspecific neighbours via AM mycelia. However, nutrient transfer via AM fungi was not uniform between neighbouring species. 3Conservative estimates indicate that interplant transfer via AM fungi accounted for >50% of the total 32P acquisition by S. nutans, but accounted for only 20% of 32P uptake into A. ludoviciana. 4While this study did not show conclusively that a common mycelial network acted as a conduit for nutrient transfer, it clearly demonstrated that mycorrhizae facilitated transfer. 5The results indicate that differential movement of plant resources via AM mycelium may be a mechanism whereby a dominant, highly mycotrophic grass extends competitive advantage over a less mycotrophic, subdominant forb species in grasslands.

Natural 15N abundances in a tallgrass prairie exposed to 8 years of elevated atmospheric CO2 - Williams, M.A.; C. W. Rice; Owensby, C.E. (Soil Biology & Biochemistry, 2006)
After 8-y of elevated CO2, we previously detected greater amounts of total soil nitrogen, suggesting that rates of ecosystem N flux into or out of tallgrass prairie had been altered. Denitrification and associative N fixation rates are the two primary biological processes that are known to control N loss and accumulation in tallgrass prairie soil. Therefore, our objective was to assess the natural abundance of plant and soil 15N isotopes as a cumulative index of potential change in efflux or influx of N into and out of the tallgrass prairie after 8-y of exposure to elevated CO2. Aboveground plant delta 15N values of Andropogon gerardii were close to zero and more positive as a result of elevated CO2, but whole-soil values at the 5–30 cm depth were significantly reduced (6.8 vs 7.3; P<0.05) under elevated CO2-chamber (EC) relative to ambient CO2- chamber (AC). Total, aboveground plant biomass, root-in-growth, extractable N, microbial biomass N, and soil pools collectively exhibited a range of delta 15N values from −2.8 to 7.3. Measurements of surface soil 15N indicate that a change in N inputs and outputs has occurred as a result of elevated atmospheric CO2. In addition to possible changes in denitrification and N2 fixation, other sources of N such as the re-translocation of N to the surface from deeper soil layers are needed to explain how soil N accrues in surface soils as a consequence of elevated CO2. Our results support the notion that C accrual may promote N accrual, possibly driven by high plant and microbial N demand amplified by soil N limitation.

Nest desertion bya cowbird host: an anti-parasite behavior or a response to egg loss? - Kosciuch, K.L.; Parker, T.H.; Sandercock, B.K. (Behavioral Ecology, 2006)
Natural selection can favor songbirds that desert nests containing eggs of the parasitic brown-headed cowbird (Molothrus ater). However, the high variability in desertion of parasitized nests within species is perplexing in light of the typically high costs of parasitism. Because nest desertion can also be a response to partial clutch predation, we first asked if Bell's vireos (Vireo bellii) deserted nests in response to the presence of cowbird eggs (antiparasite response hypothesis) or to egg removal by predators and female cowbirds (egg predation hypothesis). Second, we asked whether variation in nest desertion was due to intrinsic differences among individuals or to variation in nest contents. We monitored a large number of nests (n = 494) and performed a clutch manipulation experiment to test these hypotheses. The number of vireo eggs that remained in a nest was a strong predictor of desertion both within and among pairs. Neither the presence of a single cowbird egg, which leads to nest failure for this host, nor the number of cowbird eggs received in a vireo nest influenced nest desertion. Furthermore, vireos did not desert experimental nests when we immediately exchanged cowbird eggs for vireo eggs but deserted if we removed vireo eggs and replaced them with cowbird eggs the following morning. Desertion of parasitized nests by Bell's vireos can be almost entirely explained as a response to partial or complete clutch loss and does not appear to have been altered by selection from brood parasitism.
Keywords: Bell's Vireo; brown-headed cowbird; egg predation; evolutionary lag; host–parasite coevolution; Molothrus ater; Vireo bellii

Non-neutral patterns of species abundance in grassland communities - Harpole, W.S.; Tilman, D. (Ecology Letters, 2006)
Although the distribution of plant species abundance in a Minnesota grassland was consistent with neutral theory, niche but not neutral mechanisms were supported by the ability of species traits to predict species abundances in three experimental grassland communities. In particular, data from 27 species grown in monoculture showed that species differed in a trait, R*, which is the level to which each species reduced the concentration of soil nitrate, the limiting soil nutrient and which is predicted to be inversely associated with competitive ability for nitrogen (N). In these N-limited habitats, species abundance ranks correlated with their predicted competitive ranks: low R* species, on average dominated. These correlations were significantly different than expected for neutral theory, which assumes the exchangeability of species traits. Additionally, we found that changes in relative abundance after environmental change (N-addition or disturbance) were not neutral but also were significantly associated with R*.

Nutrients and the Dead Zone: Ecological stoichiometry and depressed dissolved oxygen in the northern Gulf of Mexico - W. K. Dodds (Frontiers in Ecology and the Environment, 2006)

Patterns of plant diversity and their management across South African rangelands - Uys, R.G. (University of Cape Town, 2006)

Redefining the community:a species-based approach - W. K. Dodds; Nelson, J.A. (Oikos, 2006)
We propose that effective community size can be defined on the basis of the web of indirect interactions experienced on average by each individual species. Indirect interaction chains are composed of links provided by direct interactions. We analyzed previously published data on 20 assemblages of species. Chain strengths were estimated by the weakest link and by the product of link strength. The average strength of the interaction chain decreased with increasing numbers of links with both models. Positive indirect interactions in chains with an even number of links offset negative direct interactions. We set the community size by the chain length where 95% of the indirect interactions are weaker than 10% of the mean of the absolute value of direct interaction strength. Using the multiplicative model, seven assemblages had a community size (web of interaction length) of three links, one of four links, and the remainder of communities were too small to set community size. The analysis suggests that effective communities of size are rarely investigated in ecological experiments.

The role of seed and vegetative reproduction in plant recruitment and demography in tallgrass prairie - Benson, E.; D.C. Hartnett (Plant Ecology, 2006)
Recruitment, establishment and survivorship of seed- and vegetatively-derived shoots were quantified biweekly in annually burned and infrequently burned tallgrass prairie to investigate the contributions of seed and vegetative reproduction to the maintenance and dynamics of tallgrass prairie plant populations, the demography of seedlings and ramets, and the influence of fire on the demography of grasses and forbs. Clonally produced grass and forb ramets comprised >99%of all established shoots present at the end of the growing season, whereas established seedlings accounted for <1%,emphasizing the rarity of successful seedling establishment and the importance of vegetative reproduction in driving the annual regeneration and dynamics of aboveground plant populations in tallgrass prairie. Most recruitment from vegetative reproduction occurred early in the growing season and was higher in annually burned than infrequently burned sites, although low levels of new stem recruitment occurred continuously throughout the growing season. Peak recruitment on annually burned prairie coincided with peak recruitment of the dominant C4 grasses Andropogon gerardii and Sorghastrum nutans prior to prescribed spring fire, with a second peak in recruitment occurring following fire. On infrequently burned prairie, grass and forb recruitment was highest in early April and declined steadily through May. The naturalized C3 grass, Poa pratensis, was responsible for most of the early recruitment on unburned sites, whereas A. gerardii contributed most to recruitment later in May. Infrequently burned prairie was dominated by these two grasses and contained a larger forb component than annually burned prairie. The principal demographic effect of fire was on ramet natality rather than mortality. Fire regime, plant functional group, or timing of cohort emergence before or after fire did not affect ramet survivorship. C4 grass shoots that emerged early and were damaged by fire showed similar survivorship patterns to tillers that emerged after fire. Differences in species composition between annually burned and infrequently burned prairie are driven by fire effects on vegetative reproduction and appear to be related principally to the effect of fire and detritus accumulation on the development of belowground vegetative meristems of C4 grasses and their emergence dynamics.
Keywords: fire ecology; grassland; Rhizomes; Sexual reproduction; Survivorship

Scale-dependent interaction of fire andgrazing on community heterogeneity in tallgrass prairie - Scott. L. Collins; M.D. Smith (Ecology, 2006)
Natural disturbances affect spatial and temporal heterogeneity in plant communities, but effects vary depending on type of disturbance and scale of analysis. In this study, we examined the effects of fire frequency (1-, 4-, and 20-yr intervals) and grazing by bison on spatial and temporal heterogeneity in species composition in tallgrass prairie plant communities. Compositional heterogeneity was estimated at 10-, 50-, and 200-m2 scales. For each measurement scale, we used the average Euclidean Distance (ED) between samples within a year (2000) to measure spatial heterogeneity and between all time steps (1993–2000) for each sample to measure temporal heterogeneity. The main effects of fire and grazing were scale independent. Spatial and temporal heterogeneity were lowest on annually burned sites and highest on infrequently burned (20-yr) sites at all scales. Grazing reduced spatial heterogeneity and increased temporal heterogeneity at all scales. The rate of community change over time decreased as fire frequency increased at all scales, whereas grazing had no effect on rate of community change over time at any spatial scale. The interactive effects of fire and grazing on spatial and temporal heterogeneity differed with scale. At the 10-m2 scale, grazing increased spatial heterogeneity in annually burned grassland but decreased heterogeneity in less frequently burned areas. At the 50-m2 scale, grazing decreased spatial heterogeneity on 4-yr burns but had no effect at other fire frequencies. At the 10-m2 scale, grazing increased temporal heterogeneity only on 1- and 20-yr burn sites. Our results show that the individual effects of fire and grazing on spatial and temporal heterogeneity in mesic prairie are scale independent, but the interactive effects of these disturbances on community heterogeneity change with scale of measurement. These patterns reflect the homogenizing impact of fire at all spatial scales, and the different frequency, intensity, and scale of patch grazing by bison in frequently burned vs. infrequently burned areas.

Sentinel nematodes of land-use change and restoration in tallgrass prairie - Todd, T.C.; Powers, T.O.; Mullin, P.G. (Journal of Nematology, 2006)
Changes in land use and the associated changes in land cover are recognized as the most important component of human-induced global change. Much attention has been focused on deforestation, but grasslands are among the most endangered ecosystems on Earth. The North American tallgrass prairie is a dramatic example, exhibiting a greater than 95% decline in historical area. Renewed interest in prairie conservation and restoration has highlighted the need for ecological indicators of disturbance and recovery in native systems, including the belowground component. The tallgrass prairie differs from the agricultural systems that have replaced it in having greater diversity and heterogeneity of resources, less physical soil disturbance (although other disturbances, such as fire and grazing, are prominent), and greater nitrogen limitation. Understanding the responses of nematode taxa to these characteristic differences is crucial to the development and improvement of community indices, but while knowledge of disturbance responses by individual taxa is accumulating, the level of necessary taxonomic resolution remains in question. Although nematode communities generally are better described for temperate grasslands than for other natural ecosystems, identification of sentinel taxa is further confounded by high levels of diversity, and both spatial and temporal heterogeneity.

Species richness- productivity relationship for small mammals along a desert-grassland continuum: differential responses of functional groups - Reed, A.W.; Kaufman, G.A.; D.W. Kaufman (Journal of Mammalogy, 2006)
We used published data to calculate small-mammal species richness at 43 sites in North America to examine the response of species richness to increasing primary productivity. We estimated species richness for the entire community and for each of 4 functional groups (insectivore, granivore, herbivore, and omnivore). Total richness exhibited a significant unimodal relationship to increasing amounts of annual precipitation and was driven by granivores; this functional group exhibited the most pronounced decline in richness with high precipitation. We suggest that the decline in granivore richness is due to increased litter associated with increased productivity.
Keywords: desert; functional group; Grasslands; Primary productivity; Resource heterogeneity; small mammals; Species richness

Superstatistics of hydro-climatic fluctuations and interannual ecosystem productivity - Porporato, A.; Vico, G.; Fay, P.A. (Geophysical Research Letters, 2006)
[1] Ecosystems driven by hydro-climatic fluctuations at different time scales can be interpreted as non-equilibrium dynamical systems. Here we explore the propagation of daily and interannual rainfall fluctuations through the soil-plant system using the theory of superstatistics. With the help of simplified stochastic models of rainfall, we show how interactions of daily and interannual rainfall fluctuations may qualitatively change the probability distributions of rainfall toward higher frequencies of extreme droughts and intense storms. This in turn is likely to induce marked changes in productivity of mesic ecosystems, while more xeric ecosystems might be insensitive or even benefit from them. This study provides a theoretical basis for predictions of ecosystem responses to the increased precipitation variability expected in future North American climate regimes.

Sustainable management of insect herbivores in grassland ecosystems: new perspectives in grasshopper control - Branson, D.H.; Anthony Joern; Sword, G.A. (BioScience, 2006)
Grasshoppers are insect herbivores common to grassland ecosystems worldwide. They comprise important components of biodiversity, contribute significantly to grassland function, and periodically exhibit both local and large-scale outbreaks. Because of grasshoppers' potential economic importance as competitors with ungulate grazers for rangeland forage, periodic grasshopper outbreaks in western US rangeland often elicit intervention over large areas in the form of chemical control. Available information combined with alternative underlying conceptual frameworks suggests that new approaches for sustainable management of grasshopper outbreaks in US rangeland should be pursued. There are many reasons to believe that approaches to grasshopper management that aim to reduce or prevent outbreaks are possible. These habitat manipulation tactics maintain existing ecological feedbacks responsible for sustaining populations at economically nonthreatening levels. Sustainable strategies to minimize the likelihood and extent of grasshopper outbreaks while limiting the need for chemical intervention are a rational and attainable goal for managing grasslands as renewable resources.
Keywords: Grassland ecology; habitat manipulation; insect population dynamics; prevention of grasshopper outbreaks; sustainable pest management

Temperature and kairomone induced life history plasticity in coexisting Daphnia - Bernot, R.J.; W. K. Dodds; Quist, M.C.; Guy, C.S. (Aquatic Ecology, 2006)
We investigated the life history alterations of coexisting Daphnia species responding to environmental temperature and predator cues. In a laboratory experiment, we measured Daphnia life history plasticity under different predation risk and temperature treatments that simulate changing environmental conditions. Daphnia pulicaria abundance and size at first reproduction (SFR) declined, while ephippia (resting egg) formation increased at high temperatures. Daphnia mendotae abundance and clutch size increased with predation risk at high temperatures, but produced few ephippia. Thus, each species exhibited phenotypic plasticity, but responded in sharply different ways to the same environmental cues. In Glen Elder reservoir, Kansas USA, D. pulicaria dominance shifted to D. mendotae dominance as temperature and predation risk increased from March to June in both 1999 and 2000. Field estimates of life history shifts mirrored the laboratory experiment results, suggesting that similar phenotypic responses to seasonal cues contribute to seasonal Daphnia population trends. These results illustrate species-specific differences in life history plasticity among coexisting zooplankton taxa.
Keywords: Daphnia mendotae; Daphnia pulicaria; Ephippia; Life history; Phenotypic plasticity

Temperature- dependent phenology and predation in arthropod systems - Logan, J.D.; Wolesensky, W.; Anthony Joern (Ecological Modelling, 2006)
A central issue in ecology is to determine how environmental variations associated with global climate change, especially changing temperatures, affect trophic interactions in various ecosystems. This paper develops a temperature-dependent, stage-based, discrete, cohort model of the population dynamics of an insect pest under pressure from a predator. Guided by experimental data, the model is applied specifically to predation of grasshoppers by rangeland lycosid spiders. The development rate of insect arthropods is strongly affected by temperature, and these temperature-dependent phenological effects couple with shifts in the daily activity periods for both prey and predator, thereby increasing or decreasing opportunities for interaction. The model addresses these effects quantitatively by introducing a temperature-dependent, joint-activity factor that enters the predator’s functional response. The model also includes a prey mortality rate that is temperature-dependent through the prey development rate. The model is parameterized using field and experimental data for spiders and grasshoppers. We investigate the effect of the solar power index (sunlight), mean temperature, and temperature variation, as measured by amplitude, on the developmental times and survivorship both with, and without, predation. We conclude that increasing variation in temperature results in a stronger relative effect on survivorship due to predation.
Keywords: grasshoppers; Lycosid spiders; phenology; Predator–prey models; Temperature

Unusual disturbance of small mammal live traps by American crows - Matlack, R.S.; Rehmeier, R.L.; McMillan, B.R.; D.W. Kaufman; Kaufman, G.A. (Transactions of the Kansas Academy of Science, 2006)

The use of pasture reflectance characteristics and arbuscular mycorrhizal root colonization to predict pasture characteristics of tallgrass prairie grazed by cattle and bison - Villarreal, M.; Cochran, R.C.; Johnson, D.E.; Towne, E.G.; G.T. Wilson; D.C. Hartnett; Goodin, D.G. (Grass and Forage Science, 2006)
An experiment was conducted to evaluate the potential for using arbuscular mycorrhizal fungal (AMF) root colonization and pasture reflectance characteristics as indicators of changes in tallgrass prairie vegetation resulting from differences in grazing history. The experiment was conducted within the context of a separate long-term experiment in which eight 4·9-ha pastures were grazed by either bison or cattle for nine consecutive years. Two separate ungrazed pastures were selected for comparison with grazed areas on the basis of similarity in burning regime, vegetation, soil and topographic characteristics. Four 45 m-long transects were located in the upland sites within each pasture, and four plots were clipped to ground level along each transect. Reflectance readings were taken with a hand-held radiometer at each sampling location and a soil core was collected within each plot for analysis of AMF root colonization. Reflectance readings at sixteen different wavelengths were used directly as inputs during multiple regression development or were transformed into each of three vegetation indices (normalized difference vegetation index, soil-adjusted vegetation index and wide-dynamic-range vegetation index) and used in simple linear regressions. Ungrazed pastures were characterized by higher (P < 0·01) grass biomass, total biomass and canopy height than grazed pastures, but had a lower proportional abundance of forbs (P < 0·01) and amounts of forb biomass (P = 0·04). Species of herbivore did not significantly influence above-ground characteristics that were measured. In general, AMF root colonization was relatively small and was not significantly affected by treatment and, accordingly, the variation was insufficient to test its potential as an indicator of grazing effects on vegetation or its potential relationship with pasture reflectance. Multiple regression equations based on individual wavelength reflectance values explained significantly more of the variation in above-ground vegetation characteristics than did simple regressions using vegetation indices as predictor variables (r2 values from 0·36 to 0·46 vs. 0·11 to 0·27) and have the potential to predict above-ground vegetation characteristics in heterogeneous rangelands.
Keywords: Arbuscular mycorrhizal fungi; bison; Cattle; pasture characteristics; reflectance methods; tallgrass prairie

Using measured peakflow values to evaluate the effectiveness of the rational method for prarie dominated watersheds in Northeast Kansas - Holste, J.C. (Kansas State University, 2006)

Abundance and possible functions of the root-colonising dark septate endophytic fungi - Mandyam, K.G.; A. Jumpponen (Studies in Mycology, 2005)
A comparison of published estimates of mycorrhizal and dark septate endophyte (DSE) colonisation from various ecosystems suggests that DSE may be as abundant as mycorrhizal fungi as judged by the proportion of host plants colonised in mixed plant communities, or by the extent of colonisation in sampled root systems. While many strides have been made in understanding the ecological significance of the mycorrhizal fungi, our knowledge about the role of DSE fungi is in its infancy. In order to provide a framework of testable hypotheses, we review and discuss the most likely functions of this poorly understood group of root-associated fungi. We propose that, like mycorrhizal symbioses, DSE-plant symbioses should be considered multifunctional and not limited to nutrient acquisition and resultant positive host growth responses. Admittedly, many mycorrhizal and endophyte functions, (e.g. stress tolerance, pathogen or herbivore deterrence) are likely to be mediated by improved nutritional status and increased fitness of the host. Accordingly, it is pivotal to establish whether or not the DSE fungi are involved in host nutrient acquisition, either from inorganic and readily soluble sources, or from organic and recalcitrant sources. Facilitation by DSE of the use of organic nitrogen, phosphorus and sulphur sources by plants is a topic that warrants further attention and research. Even in the absence of a clear nutrient uptake function, the extensive DSE colonisation that occurs is likely to pre-emptively or competitively deter pathogens by minimising the carbon available in host rhizosphere environment. The DSEs' high melanin levels and their potential production of secondary metabolites toxic or inhibitory to herbivores are also likely to be factors influencing host performance. Finally, the broad host ranges speculated for most DSE fungi thus far suggest that they are candidates for controlling plant community dynamics via differential host responses to colonisation. We emphasise the need for simple experiments that allow unravelling of the basic biological functions of DSE fungi when they colonise their hosts.
Keywords: abundance; Dark septate endophytes (DSE); multifunctional symbioses; mutualism; mycorrhiza

Branching responses in Silphium integrifolium (Asteraceae) following mechanical or gall damage to apical meristems and neighbor removal - Fay, P.A.; Throop, H.L. (American Journal of Botany, 2005)
Branching in plants increases plant access to light and provides pathways for regrowth following damage or loss of the apical meristem. We conducted two experiments in an eastern Kansas tallgrass prairie to determine how apical meristem loss (by clipping), apical meristem damage (by insect galling), and increased light availability affected growth, reproduction, and branching in Silphium integrifolium (Asteraceae). The first experiment compared clipping with galling. Clipping increased axillary shoot numbers, while galling increased axillary shoot lengths, reflecting different allocation responses among damage types and inhibition of branching by galls. However, total capitulum production was less in all gall/clip treatments than in intact shoots. The second experiment compared clipping with mowing the surrounding vegetation to increase light availability. Mowing increased total leaf, total capitulum, and axillary shoot length and axillary capitulum production in clipped and unclipped plants and in large vs. small shoots. The presence of the neighboring canopy, not of an intact apical meristem, was therefore the stronger limitation on leaf and capitulum production. These experiments suggest that damage and light competition affected both branching frequency and the partitioning of resources among shoots, branches, and leaves. Because Silphium's growth form is widespread, similar responses may occur in other grassland forbs.
Keywords: Antistrophus silphii; apical dominance; Asteraceae; branching competition; galls; Herbivory; Konza Prairie

Can rDNA analyses of diverse fungal communities in soil and rootsdetect effects of environmental manipulations--a case study from tallgrass prairie - A. Jumpponen; Johnson, L.C. (Mycologia, 2005)
We tested whether fungal communities are impacted by nitrogen deposition or increased precipitation by PCR-amplifying partial fungal rRNA genes from 24 soil and 24 root samples from a nitrogen enrichment and irrigation experiment in a tallgrass prairie at Konza Prairie Biological Station in northeastern Kansas, U.S.A. Obtained fungal sequences represented great fungal diversity that was distributed mainly in ascomycetes and basiodiomycetes; only a few zygomycetes and glomeromycetes were detected. Conservative extrapolated estimates of the fungal species richness suggest that the true richness may be at least twice as high as observed. The effects of nitrogen enrichment or irrigation on fungal community composition, diversity or clone richness could not be unambiguously assessed because of the overwhelming diversity. However, soil communities differed from root communities in diversity, richness and composition. The compositional differences were largely attributable to an abundant, soil-inhabiting group placed as a well-supported sister group to other ascomycetes. This group likely represents a novel group of fungi. We conclude that the great fungal richness in this ecosystem precluded a reliable assessment of anthropogenic impacts on soil or rhizosphere communities using the applied sampling scheme, and that detection of novel fungi in soil may be more a rule than an exception.
Keywords: Biodiversity; environmental change; fungi; nitrogen; Precipitation; soil DNA

Carrion beetles (Coleoptera: Silphidae) of the Konza Prairie Biological Stationbeetles (Coleoptera: Silphidae) of the Konza Prairie Biological Station - Rintoul, D.A.; Krueger, L.M.; Woodard, C.; Throne, J.E. (Journal of the Kansas Entomological Society, 2005)
Pitfall traps were used to determine diversity, seasonality, and numbers of burying beetles on the Konza Prairie Biological Station (KPBS) during the summers of 1997 and 1998. Traps were baited with either beef liver (1997) or whole mouse carcasses (1997 and 1998); significantly more carrion beetles were found in traps baited with carcasses. A total of 1003 carrion beetles, representing 8 species, were trapped over the course of 1556 trap nights. One of these species, Necrophila americana Linneaus, had not previously been recorded in Riley County. One additional species was found at sites where pitfall trap bait was discarded, bringing the total number of KPBS silphid species to 9. Bait age was an important determinant in attracting silphids to pitfall traps, as numbers of beetles in the trap continued to increase with bait age up to 6 days. Grassland topography (upland vs. lowland trap sites) significantly affected the numbers of carrion beetles trapped. Grassland burn history did not affect number of carrion beetles trapped, but did seem to influence species diversity.
Keywords: Konza Prairie Biological Station; Nicrophorus marginatus; pitfall trap; seasonal occurrence; Silphidae

Chronic nitrogen loading in streams - Bernot, M.J.; W. K. Dodds (Ecosystems, 2005)

Comparing the influence of precipitation, fire, and topography on plant productivity in the tallgrass prairie - Jesse B. Nippert; John M. Blair (2005)

Competition, facilitation, and niche differentiation in two foliar pathogens - Al-Naimi, F.; Garrett, K.A.; Bockus, W.W. (Oecologia, 2005)
We studied competition between the obligate biotroph Puccinia triticina (designated here as Puccinia) and the facultative saprophyte Pyrenophora tritici-repentis (designated here as Pyrenophora) in older and younger leaves in a set of three host genotypes selected to be resistant to Puccinia only, Pyrenophora only, or neither. Age-related resistance is important for both of these pathogens. The facultative saprophyte Pyrenophora was generally a stronger competitor than the biotrophic Puccinia, even experiencing facilitation from the presence of Puccinia when Pyrenophora had the advantage of earlier inoculation. Both pathogen species produced the most spores when they were introduced before the competing species and more spores when introduced simultaneously compared to after the competitor. The pre-interactive niche of Puccinia was larger than the post-interactive niche and sporulation by Puccinia was substantially reduced in environments in which Pyrenophora had high sporulation rates. The pre-interactive niche of Pyrenophora was similar to the post-interactive niche and Pyrenophora had proportionally lower reductions in sporulation due to interspecific competition in the pre-interactive niche.
Keywords: Facultative saprophytes; Impact niche; Obligate parasites; Requirement niche; Rust fungi

Contribution to the taxonomy and faunistics of the genus Meropleon Dyar (Lepidoptera: Noctuidae) - Metlevski, J. (2005)
A new species of owlet moth, Meropleon linae (Lepidoptera: Noctuidae) from Kansas, is described and illustrated. Meropleon linae is distinguished from other species of Meropleon by forewing color and pattern, shape of thevalva, and structure of the aedoeagus. Meropleon linae is most similar morphologically to M. cinnamicolor Ferguson. New distribution records for M. ambifuscum (Newman) and the first record for M. titan Todd in Kansas are given.

Density-dependent habitatselection by Brown-headed Cowbirds (Molothrus ater) in tallgrassprairie - Jensen, W.E.; Cully, J.F. (Oecologia, 2005)
Local distributions of avian brood parasites among their host habitats may depend upon conspecific parasite density. We used isodar analysis to test for density-dependent habitat selection in brown-headed cowbirds (Molothrus ater) among tallgrass prairie adjacent to wooded edges, and prairie interior habitat (>100 m from wooded edges) with and without experimental perches. Eight study sites containing these three habitat treatments were established along a geographical gradient in cowbird abundance within the Flint Hills region of Eastern Kansas and Oklahoma, USA. The focal host species of our study, the dickcissel (Spiza americana), is the most abundant and preferred cowbird host in the prairie of this region. Cowbird relative abundance and cowbird:host abundance ratios were used as estimates of female cowbird density, whereas cowbird egg density was measured as parasitism frequency (percent of dickcissel nests parasitized), and parasitism intensity (number of cowbird eggs per parasitized nest). Geographical variation in cowbird abundance was independent of host abundance. Within study sites, host abundance was highest in wooded edge plots, intermediate in the experimental perch plots, and lowest in prairie interior. Cowbirds exhibited a pattern of density-dependent selection of prairie edge versus experimental perch and interior habitats. On sites where measures of cowbird density were lowest, all cowbird density estimates (female cowbirds and their eggs) were highest near (≤100 m) wooded edges, where host and perch availability are highest. However, as overall cowbird density increased geographically, these density estimates increased more rapidly in experimental perch plots and prairie interiors. Variation in cowbird abundance and cowbird:host ratios suggested density-dependent cowbird selection of experimental perch over prairie interior habitat, but parasitism levels on dickcissel nests were similar among these two habitats at all levels of local cowbird parasitism. The density-dependent pattern of cowbird distribution among prairie edge and interior suggested that density effects on perceived cowbird fitness are greatest at wooded edges. A positive relationship between daily nest mortality rates of parasitized nests during the nestling period with parasitism intensity levels per nest suggested a density-dependent effect on cowbird reproductive success. However, this relationship was similar among habitats, such that all habitats should have been perceived as being equally suitable to cowbirds at all densities. Other unmeasured effects on cowbird habitat suitability (e.g., reduced cowbird success in edge-dwelling host nests, cowbird despotism at edges) might have affected cowbird habitat selection. Managers attempting to minimize cowbird parasitism on sensitive cowbird hosts should consider that hosts in otherwise less-preferred cowbird habitats (e.g., habitat interiors) are at greater risk of being parasitized where cowbirds become particularly abundant.
Keywords: Edge effects; Ideal free distribution; Isodar; Molothrus ater; Spiza americana

Distribution of carnivore burrows in a prairie landscape - Kaufman, G.A.; Kocher, S.D.; D.W. Kaufman (Great Plains Research, 2005)
Mammals impact prairie ecosystems through burrowing activities. Burrows used by carnivores were studied in four habitat types at the Konza Prairie Biological Station, a native tallgrass prairie near Manhattan, KS. We surveyed nearly 40 km of 10-m-wide transects and counted burrows in upland, slope, and lowland prairie and along ravines. Burrows were placed selectively along slopes (7.3 per km) and to a lesser extent along edges of ravines (4.2), but only infrequently in upland (0.6) and never in lowlands (0.0). We also recorded features (e.g., location, aspect, and slope steepness) along slope transects at a 30 m intervals to estimate availability of these features. Points of hills (18.7 burrows per km) were used more than sides of hills (2.0) or upper ends of ravines (1.5). Burrows on points were placed selectively on steep rather than shallow slopes and on south- and west-facing slopes rather than north- and east-facing slopes.
Keywords: burrows; carnivores; kansas; tallgrass prairie; topography

Do individual plant speciesshow predictable responses to nitrogen addition across multipleexperiments? - Pennings, S.C.; Clark, C.M.; Cleland, E.E.; Scott. L. Collins; Gough, L.; Gross, K.L.; Milchunas, D.G.; K.N. Suding (Oikos, 2005)
A number of experiments have addressed how increases in nitrogen availability increase the productivity and decrease the diversity of plant communities. We lack, however, a rigorous mechanistic understanding of how changes in abundance of particular species combine to produce changes in community productivity and diversity. Single experiments cannot provide insight into this issue because each species occurs only once per experiment, and each experiment is conducted in only one location; thus, it is impossible from single experiments to determine whether responses of particular species are consistent across environments or dependent on the particular environmental context in which the experiment was conducted. To address this issue, we assembled a dataset of 20 herbaceous species that were each represented in at least 6 different fertilization experiments and tested whether responses were general across experiments. Of the 20 species, one consistently increased in relative abundance and five consistently decreased across replicate experiments. A partially-overlapping group of 8 species displayed responses to nitrogen that varied predictably among experiments as a function of geographic location, neighboring species, or a handful of other community characteristics (ANPP, precipitation, species richness, relative abundance of focal species in control plots, and community composition). Thus, despite modest replication and a limited number of predictor variables, we were able to identify consistent patterns in response of 10 out of 20 species across multiple experiments. We conclude that the responses of individual species to nitrogen addition are often predictable, but that in most cases these responses are functions of the abiotic or biotic environment. Thus, a rigorous understanding of how plant species respond to nitrogen addition will have to consider not only the traits of individual plant species, but also aspects of the communities in which those plants live.

Ecological consequences of C4 grass invasion of a C4 grassland: A dilemma for management - Reed, H.; Seastedt, T.R.; John M. Blair (Ecological Applications, 2005)
Many successful exotic invasive species are functionally distinct from the dominant native species they displace. Occasionally invasion occurs where the exotic species possesses functional traits relatively similar to those of the dominant native. We examined the ecological consequences of such an invasion within a mesic, temperate grassland at the Konza Prairie Long-Term Ecological Research site. We assessed potential changes in carbon (C) and nitrogen (N) cycling and plant diversity following the invasion of a C4 bunch grass species, Andropogon bladhii, into a tallgrass prairie dominated by the native C4 grass species, A. gerardii. In these prairies burning is an important management tool used to maintain native-species dominance. We determined how frequent spring fires affected the impacts of A. bladhii in this system. Over a two-year study our results show that burning regulated the effects that the invasive species has on the native prairie. Compared to the native species, A. bladhii exhibited significantly greater plant biomass, significantly lower pools of soil N, significantly lower rates of decay and C cycling, and higher foliar and root tissue C:N ratio in response to burning. Notable spatial heterogeneity in C and N cycling was evident in areas dominated by the invasive bunch grass. In addition to altered ecosystem processes, areas dominated by the invasive, A. bladhii, had significantly lower plant species diversity. In a grassland ecosystem where burning is an important management tool for controlling exotic-species establishment, maintaining native-species dominance, and increasing productivity, A. bladhii may be able to successfully out-compete the native C4 grass species by using traits typically used to explain the dominance of the native species. With frequent fire, the invasive species has the potential to decrease long-term fertility by lowering N inputs in litter and increasing erosion in non-vegetated soil between bunches, while also having a negative effect on plant diversity. By using fire to promote native C4 grasses and maintain these tallgrass prairies, the threat of invasion by nonnative C4 species may raise a dilemma for future management of these C4 grasslands.

An ecosystem in transition: causes and consequences of the conversion of mesic grassland to shrubland - J. M. Briggs; Alan K. Knapp; John M. Blair; Heisler, J.L.; Hoch, G.A.; Lett, M.S.; McCarron, J.K. (BioScience, 2005)
Woody plant expansion is one of the greatest contemporary threats to mesic grasslands of the central United States. In this article, we synthesize more than 20 years of research to elucidate the causes and consequences of the ongoing transition of C4-dominated grasslands to savanna-like ecosystems codominated by grasses and woody plants. This transition is contingent on fire-free intervals, which provide the opportunity for recruitment both of new individuals and of additional shrub and tree species into this grassland. Once shrubs establish, their cover increases regardless of fire frequency, and infrequent fires accelerate the spread of some shrub species. This process has resulted in a new dynamic state of shrub–grass coexistence in the mesic grasslands of North America. Important consequences of this shift in plant life-form abundance include alterations in plant productivity, species diversity, and carbon storage. Without drastic measures such as mechanical removal of shrubs, it is unlikely that management of fire and grazing regimes alone will be sufficient to restore historic grass dominance in these ecosystems.
Keywords: fire; Grasslands; Grazing; tallgrass prairie; woody vegetation

The effect of brown-headed cowbird removal on thedemography of the dickcissel (Spiza americana) - Hewett, E.L. (Cornell University, 2005)

Effects of fire and plant invasion on aspects of aboveground and belowground interactions in an eastern tallgrass prairie - Reed, H. (University of Colorado, 2005)
This thesis is comprised of three studies evaluating whether shifts in soil or plant communities affect each other as well as ecosystem processes. I used contrasting fire regimes and a plant species invasion to test hypotheses regarding the biological effects of composition on decomposition, plant species effects on ecosystem functioning, and root-associated bacterial relationships with plant species. All studies were conducted at the Konza Prairie Biological Station (KPBS), a representative tallgrass prairie ecosystem of the United States. I compared soil biota effects on decomposition and decomposition stability in burned and unburned prairie. Upon assessing effects of soil biota composition on decomposition rates and decomposition stability of various surface and buried substrates, I found no consistent effect of community composition on decomposition or decomposition stability. Rather, a complex interaction between community composition and substrate type mediated responses. Burn regimes influenced the effects of soil communities on decomposition stability and suggested effects on functional stability should be considered when managing ecosystems. The second and third studies used the invasion of Andropogon bladhii, a C4 grass species, onto KPBS to examine whether displacement of a native C4 dominant (Andropogon gerardii ) by the non-native C4 species affects ecosystem properties and community structure. I measured plant species diversity, pools and cycling rates of C and N in native and invasive dominated sites. The invasive species imposes spatial heterogeneity in soil properties, creates a potential to decrease ecosystem N availability, and reduces plant species diversity. A positive response to burning exacerbates this species' ecosystem effects and thwarts management practices to exclude invasive species. Finally, I compared root-associated bacterial communities of each plant species in the first known study to use a molecular phylogenetic approach to examine root-bacteria in a non-agriculture system. The two plant species harbor similar bacteria groups when examined at a broad taxonomic scale; but distinct communities are evident when compared at finer taxonomic resolutions. A large effect on root bacteria as a possible invasion mechanism was not evident, however, the role of these bacteria in assisting the invasive plant in altering biogeochemical properties of the prairie cannot be ruled out.

Effects of long-term fire and mowing on root dynamics in tallgrass prairie - Kitchen, D.J. (Kansas State University, 2005)

Environmental constraints on a global relationship among leaf and root traits of grasses - Craine, J.M.; Lee, W.G.; Bond, W.J.; Willians, R.J.; Johnson, L.C. (Ecology, 2005)
Uncertainties regarding the relationships between leaf and root traits have impeded an integrated understanding of plant evolution and the efficient parameterization of ecosystem models. We measured key root and leaf traits of grasses from 77 sites in four grassland regions of the world (New Zealand, Australia, South Africa, North America). Within each region, the relationships among leaf traits paralleled those among root traits. Plants with low root or leaf N concentrations had roots or leaves with high tissue density, high lignin concentrations, low amount of mass that was soluble in a neutral detergent solution, large diameter/thickness, and were less enriched in 15N. Yet, whether comparing plants within a region or among all four regions, there was little relationship between root traits and leaf traits, except for a positive relationship between root and leaf N concentration and between root and leaf δ15N. At the global scale, factors such as soil freezing and the type of nutrient limitation appear to determine relationships among leaves and roots. C4 grasses not only had lower leaf N concentrations than C3 grasses but also lower root N concentrations. When compared at the same root N concentration, C4 grasses had greater leaf N concentrations than C3 grasses.

Estimation of stream nutrient uptake from nutrient addition experiments - Payn, R.A.; Webster, J.R.; Mulholland, P.J.; Valett, H.M.; W. K. Dodds (Limnology and Oceanography Methods, 2005)
Nutrient uptake in streams is often quantified by determining nutrient uptake length. However, current methods for measuring nutrient uptake length are often impractical, expensive, or demonstrably incorrect. We have developed a new method to estimate ambient nutrient uptake lengths using field experiments involving several levels of nutrient addition. Data analysis involves plotting nutrient addition uptake lengths versus added concentration and extrapolating to the negative ambient concentration. This method is relatively easy, inexpensive, and based on sound theoretical development. It is more accurate than the commonly used method involving a single nutrient addition. The utility of the method is supported by field studies directly comparing our new method with isotopic tracer methods for determining uptake lengths of phosphorus, ammonium, and nitrate. Our method also provides parameters for comparing potential nutrient limitation among streams.

Evidence for a general species-time-area relationship - P. Adler; White, E.P.; Lauenroth, W.K.; Kaufman, D.M.; Rassweiler, A.; Rusak, J.A. (Ecology, 2005)
The species–area relationship (SAR) plays a central role in biodiversity research, and recent work has increased awareness of its temporal analogue, the species– time relationship (STR). Here we provide evidence for a general species–time–area relationship (STAR), in which species number is a function of the area and time span of sampling, as well as their interaction. For eight assemblages, ranging from lake zooplankton to desert rodents, this model outperformed a sampling-based model and two simpler models in which area and time had independent effects. In every case, the interaction term was negative, meaning that rates of species accumulation in space decreased with the time span of sampling, while species accumulation rates in time decreased with area sampled. Although questions remain about its precise functional form, the STAR provides a tool for scaling species richness across time and space, for comparing the relative rates of species turnover in space and time at different scales of sampling, and for rigorous testing of mechanisms proposed to drive community dynamics. Our results show that the SAR and STR are not separate relationships but two dimensions of one unified pattern.

Factors influencing nightly activity of deer mice (Peromyscus maniculatus) in tallgrass prairie - Rehmeier, R.L. (Kansas State University, 2005)
Little is known about nightly activity patterns of nocturnal small mammals under natural conditions, and how these activity patterns might be affected by photoperiod, season, and sex, age, and reproductive status of individuals. The main objectives of this research were: 1) to find an appropriate method for marking individual deer mice (Peromyscus maniculatus) so that their activity could be monitored remotely; 2) to design a portable activity-monitoring system to investigate temporal patterns of shelter use by deer mice under natural conditions; 3) to determine the influence of environmental conditions such as photoperiod and season on nightly activity of deer mice; and 4) to compare effects of demographic or physiological factors such as sex, age, and reproductive status on nightly activity of deer mice at artificial burrows in tallgrass prairie. In general, commencement of activity was correlated positively with timing of sunset, and time of retirement to the burrow was correlated positively with sunrise. Among adults, males first emerged from the burrow earlier and made more trips of shorter duration in a night than did females, although total duration of trips was similar. Return visits and subsequent stays typically were shorter for males than females, but total time spent in the burrow and retirement time relative to sunrise were similar for both sexes. Young deer mice emerged significantly later, made more trips of shorter duration, spent less total time outside, and retired to their burrow earlier than adults. Reproductive females emerged later, made fewer trips of generally longer duration, and spent shorter total amounts of time away from the burrow each night than non-reproductive females. Return visits of reproductive females were of longer duration than non-reproductives, but total time spent inside and time of retirement for the night did not differ relative to reproductive status. From parturition through lactation, activity of females showed a number of directional trends. Results suggest that under natural conditions, activity patterns of deer mice are highly variable but responsive to both the changing physical environment and internal conditions related to sex-specific maximization of fitness.
Keywords: Activity-monitoring system; kansas; Nocturnal; PIT tag; reproduction; rodent

Factors influencing persistence of white-footed mice (Peromyscus leucopus) - McMillan, B.R.; Kaufman, G.A.; D.W. Kaufman (The Prairie Naturalist, 2005)

Functional and abundance based mechanisms explain diversity loss due to nitrogen fertilization - K.N. Suding; Scott. L. Collins; Gough, L.; Clark, C.M.; Cleland, E.E.; Gross, K.L.; Milchunas, D.G.; Pennings, S. (Proceedings of the National Academy of Sciences, 2005)
Human activities have increased N availability dramatically in terrestrial and aquatic ecosystems. Extensive research demonstrates that local plant species diversity generally declines in response to nutrient enrichment, yet the mechanisms for this decline remain unclear. Based on an analysis of >900 species responses from 34 N-fertilization experiments across nine terrestrial ecosystems in North America, we show that both trait-neutral and trait-based mechanisms operate simultaneously to influence diversity loss as production increases. Rare species were often lost because of soil fertilization, randomly with respect to traits. The risk of species loss due to fertilization ranged from >60% for the rarest species to 10% for the most abundant species. Perennials, species with N-fixing symbionts, and those of native origin also experienced increased risk of local extinction after fertilization, regardless of their initial abundance. Whereas abundance was consistently important across all systems, functional mechanisms were often system-dependent. As N availability continues to increase globally, management that focuses on locally susceptible functional groups and generally susceptible rare species will be essential to maintain biodiversity.

Geographic variation in Brown-headed Cowbird (Molothrus ater) parasitism on Dickcisssels (Spiza americana) in Great Plains tallgrass prairie - Jensen, W.E.; Cully, J.F. (Auk, 2005)
The incidence of brood parasitism by Brown-headed Cowbirds (Molothrus ater; hereafter “cowbirds“) within host species typically reflects the continental pattern in cowbird abundance across North America, where parasitism is heaviest in the Great Plains. However, we found considerable variation in cowbird parasitism on Dickcissel (Spiza americana) nests within a subregion of the Great Plains (the Flint Hills), where the highest levels of cowbird parasitism on grassland bird nests had been previously reported. Local parasitism frequencies on Dickcissel nests varied latitudinally across the Flint Hills, ranging from 0% to 92% of nests parasitized. Interestingly, we found no obvious patterns in habitat or host attributes that were associated with this steep geographic gradient in brood parasitism. Cowbird parasitism on Dickcissel nests was not correlated with the vertical density of local prairie vegetation, mean nest distance to edge, proportion of forest to grassland habitat surrounding study sites (≤5 to 10 km), geographic variation in host abundance, or Dickcissel density or nest initiation dates. Parasitism frequencies and intensities (number of cowbird eggs per parasitized nest) on Dickissel nests were only significantly related to variation in local female cowbird density. Dickcissel clutch size and apparent fledging success were negatively correlated with local cowbird parasitism levels. Geographic patterns in cowbird abundance within and among regions should be considered when establishing conservation areas for grassland birds or other cowbird hosts of concern.
Keywords: brood parasitism; brown-headed cowbird; Dickcissel; geographic variation; Molothrus ater; Spiza americana

Habitat of origin and changes in water chemistry influence development of western chorus frogs - N.M. Gerlanc; Kaufman, G.A. (Journal of Herpetology, 2005)
A variety of biotic and abiotic variables have been shown to affect length of larval period and size of juveniles at metamorphosis in amphibians. However, influence of water quality on phenotypic plasticity of growth and development of tadpoles generally has received less attention. We examined how abiotic factors in the larval environment change over time and how these changes affect the growth and development of larval amphibians. Western Chorus Frogs, Pseudacris triseriata, in tallgrass prairie breed in ephemeral aquatic habitats including intermittent streams and bison wallows. Our objectives were to determine whether abiotic factors in the larval environment of P. triseriata changed predictably as pools dried and to determine whether these changes affected growth and development of tadpoles when the environment was simulated in the laboratory. In our field studies, pH increased gradually in wallows, whereas ammonium increased in streams, as each habitat dried. In the laboratory, we examined the effects of increased levels of pH and ammonium on growth and development of tadpoles collected from both wallows and streams. Tadpoles collected from streams metamorphosed significantly faster in the high ammonium treatment than tadpoles from wallows. In contrast, tadpoles from wallows metamorphosed faster in the high pH treatment than tadpoles collected from streams. Growth rates of tadpoles from streams were not significantly affected by high pH, whereas those from wallows were not significantly affected by high ammonium treatments. We suggest that changes in abiotic factors over the course of the larval period may influence developmental rate and that natal habitat may determine how tadpoles respond to changes in abiotic factors.

Habitat use and susceptibility to predation of four prairie stream fishes: implications for conservation of the endangered Topeka shiner - Knight, G.L.; K. B. Gido (Copeia, 2005)
Local extirpations of the federally endangered Topeka Shiner (Notropis topeka) have been linked to the introduction of Largemouth Bass (Micropterus salmoides). However, because other native minnow species have persisted at these locations, our objective was to test whether Topeka Shiners were more susceptible to predation by Largemouth Bass than other native minnows. We conducted behavioral observations of Topeka Shiners, Red Shiners (Cyprinella lutrensis), Bluntnose Minnows (Pimephales notatus), and Common Shiners (Luxilus cornutus) in an indoor experimental stream, in which we examined the interactive effects of cover and the presence of a predator on longitudinal and lateral position, height in water column, cover use, and activity of these minnows. Significant differences in habitat use and response to bass were observed among species, but there was no evidence to suggest that Topeka Shiners would be more susceptible to predation than other native species. Subsequent experiments in outdoor experimental streams that allowed Largemouth Bass to forage on an assemblage of these four minnows indicated that consumption rates across species were similar, further suggesting that Topeka Shiners were not more susceptible to predation than the other minnows. Although our experiments suggest that Largemouth Bass randomly prey on this guild of minnows, the added mortality and potential indirect effects of this introduced predator likely have negative effects by further reducing the abundance of already rare Topeka Shiners.

Harshness: characterization of intermittent stream habitat over space and time - Fritz, K.M.; W. K. Dodds (Marine and Freshwater Research, 2005)
Frequently disturbed environments, such as intermittent streams, are ecologically useful for studying how disturbance characteristics (e.g. frequency, magnitude) affect community structure and succession. We developed a harshness index that quantifies ecologically pertinent spatial and temporal characteristics of prairie intermittent streams that may limit or reduce diversity and abundance to predict benthic macroinvertebrate assemblage characteristics. The index incorporates 11 variables that describe the hydrological regime (e.g. average flow, flow variability, drying and flooding) and distance to perennial surface water. We started with 27 variables, but removed 16 that did not increase the predictive value of the index. The relationships among index values and annual mean macroinvertebrate assemblage characteristics (taxonomic richness, diversity, evenness and abundance) were tested over two years using seven sites that represent a range of flow permanence (recent and historical), flood magnitude (recent and historical) and surface-water connectivity. Mean annual taxonomic richness was significantly related to the harshness index. Evenness and abundance were not related to harshness. Further analyses indicated that distance to the nearest permanent habitat was less important than annual or historical hydrological parameters, even though prior research had documented higher rates of colonisation at sites that were closer to nearest permanent habitat. Both annual factors that can alter abundance and colonisation immediately (e.g. floods, drought in each year) and historical factors (e.g. probability of drying, average length of dry period over decades) may influence assemblage characteristics. Historical factors may influence evolutionary adaptations of invertebrates and may predominate when relative disturbance rates are lower such as in years with less flooding.

Hyporheic oxygen flux and substratum spatial heterogeneity: effects on whole-stream dynamics - Wilson, K.C. (Kansas State University, 2005)

Impacts of land management practices on tallgrassprairie herpetofauna - Wilgers, D.J. (Kansas State University, 2005)

Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystem - Harper, C.W.; John M. Blair; Fay, P.A.; Alan K. Knapp; Carlisle, J.D. (Global Change Biology, 2005)
Predicted climate changes in the US Central Plains include altered precipitation regimes with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control C cycling and storage. Soil carbon dioxide (CO2) flux is an important component of C cycling in terrestrial ecosystems, and is strongly influenced by climate. While many studies have assessed the influence of soil water content on soil CO2 flux, few have included experimental manipulation of rainfall amounts in intact ecosystems, and we know of no studies that have explicitly addressed the influence of the timing of rainfall events. In order to determine the responses of soil CO2 flux to altered rainfall timing and amounts, we manipulated rainfall inputs to plots of native tallgrass prairie (Konza Prairie, Kansas, USA) over four growing seasons (1998–2001). Specifically, we altered the amounts and/or timing of growing season rainfall in a factorial combination that included two levels of rainfall amount (100% or 70% of naturally occurring rainfall quantity) and two temporal patterns of rain events (ambient timing or a 50% increase in length of dry intervals between events). The size of individual rain events in the altered timing treatment was adjusted so that the quantity of total growing season rainfall in the ambient and altered timing treatments was the same (i.e. fewer, but larger rainfall events characterized the altered timing treatment). Seasonal mean soil CO2 flux decreased by 8% under reduced rainfall amounts, by 13% under altered rainfall timing, and by 20% when both were combined (P<0.01). These changes in soil CO2 flux were consistent with observed changes in plant productivity, which was also reduced by both reduced rainfall quantity and altered rainfall timing. Soil CO2 flux was related to both soil temperature and soil water content in regression analyses; together they explained as much as 64% of the variability in CO2 flux across dates under ambient rainfall timing, but only 38–48% of the variability under altered rainfall timing, suggesting that other factors (e.g. substrate availability, plant or microbial stress) may limit CO2 flux under a climate regime that includes fewer, larger rainfall events. An analysis of the temperature sensitivity of soil CO2 flux indicated that temperature had a reduced effect (lower correlation and lower Q10 values) under the reduced quantity and altered timing treatments. Recognition that changes in the timing of rainfall events may be as, or more, important than changes in rainfall amount in affecting soil CO2 flux and other components of the carbon cycle highlights the complex nature of ecosystem responses to climate change in North American grasslands.

Indicators of plant species richness in AVIRIS spectra of a mesic grassland - Carter, G.A.; Alan K. Knapp; Anderson, J.E.; Hoch, G.A.; M.D. Smith (Remote Sensing of Environment, 2005)
Hyperspectral imagery of the Konza Prairie Biological Station in northeastern Kansas was used to evaluate upwelling spectral radiance, prairie spectral reflectance and band ratios of each as potential indicators of vascular plant species richness in a mesic grassland. The extent to which spatial variability in these parameters related to plant species richness also was investigated. A 224 channel hyperspectral data cube acquired in June 2000 by the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) provided complete coverage of the 400–2500 nm range at approximately 10 nm per channel. After band deletions accounted for detector overlap and strong atmospheric attenuation features, 176 bands were retained for analysis and spanned the 404–2400 nm range. Prairie reflectance was estimated via radiative transfer modeling and scaling to a library spectrum of highway construction material. Data were sampled from pixels having a 19 m ground sample distance (GSD) to represent each of 93 vegetation sampling transects. Reflectance and radiance at mid-infrared wavelengths (e.g., 1553 nm), and band ratios that were based on atmospheric windows in the red, near-infrared and mid-infrared spectra estimated species richness to within 6 to 7 species per transect. The 856 to 780 nm radiance or reflectance ratio yielded maximum adjusted coefficients of determination (r2) of approximately 0.4 in regressions with richness when data from bison-grazed and ungrazed areas were combined. These regressions remained significant (p ≤ 0.001) when only ungrazed areas were assessed although r2 reduced to approximately 0.2. Richness was related significantly also to the 433 to 674 nm reflectance ratio for grazed-plus-ungrazed and ungrazed-only areas. In contrast, the effectiveness of the 433 to 674 nm radiance ratio was reduced by atmospheric backscatter. Species richness did not correlate strongly or consistently with transect spatial variability (coefficient of variation or range) in radiance, reflectance or band ratio value, apparently as a consequence of the relatively small area sampled for each transect (approximately 0.5 ha). Relationships between richness and prairie spectral features were explained by the influence of soil exposure on both parameters. Richness and estimated soil exposure tended to increase from ungrazed lowlands, to ungrazed slopes, to ungrazed uplands to grazed areas. Remotely sensed estimates of soil exposure may be particularly useful in addressing plant species richness on grazed grasslands owing to an overall similarity in spectral reflectance among dominant plant species.
Keywords: AVIRIS; Biodiversity; Bison grazing; grassland; Hyperspectral; Plant species richness; Radiance; Reflectance; Soil exposure; Spatial variability; Spectral mixing

Introduced species in Kansas: floristic changes and patterns of collection based onan historical herbarium - Woods, T.M.; Strakosh, S.C.; Nepal, M.P.; Chakrabarti, S.; Simpson, N.B.; Mayfield, M.H.; Ferguson, C.J. (Sida, 2005)

Long-term disturbance from fire and bison grazing modulates grasshopper species assemblages (Orthoptera) in tallgrass prairie - Anthony Joern (Ecology, 2005)
Understanding determinants of local species diversity remains central to developing plans to preserve biodiversity. In the continental United States, climate, grazing by large mammals, fire, and topography are important ecosystem drivers that structure North American tallgrass prairie, with major impacts on plant community composition and vegetation structure. Frequency of fire and grazing by bison (Bos bison), through effects on plant community composition and altered spatial and structural heterogeneity of vegetation in tallgrass prairie, may act as bottom-up processes that modulate insect community species richness. As previously seen for plant species richness, I hypothesized that grazing had more impact than fire frequency in determining species richness of insect herbivore communities. I examined this prediction with grasshoppers at Konza Prairie, a representative tallgrass prairie site in which fire frequency and bison grazing are manipulated over long terms with landscape-level treatments. Topographic position (upland vs. lowland) and fire frequency (1-, 2-, 4-year intervals, and unburned) did not significantly influence grasshopper species richness or indices of diversity, while grazing had significant effects. On average, I found ∼45% more grasshopper species and significantly increased values of Shannon H′ diversity at sites with bison grazing. Species abundances were more equally distributed (Shannon's Evenness Index) in grazed sites as well. No significant interactions among burning and grazing treatments explained variation in grasshopper species diversity. Grasshopper species richness responded positively to increased heterogeneity in vegetation structure and plant species richness, and negatively to average canopy height and total grass biomass. Variation in forb biomass did not influence grasshopper species richness. A significant positive relationship between grasshopper species richness and overall grasshopper density was observed. Species richness increased marginally as watershed area of treatments in grazed areas increased, but not in ungrazed areas. Disturbance from ecosystem drivers operating at watershed spatial scales exhibits strong effects on local arthropod species diversity, acting indirectly by mediating changes in the spatial heterogeneity of local vegetation structure and plant species diversity.

Long-term study of abundance of the hispid cotton rat in native tallgrass prairie - Rehmeier, R.L.; Kaufman, G.A.; D.W. Kaufman; McMillan, B.R. (Journal of Mammalogy, 2005)
We studied patterns of and factors influencing abundance of hispid cotton rats (Sigmodon hispidus) in tallgrass prairie habitats from autumn 1981 to spring 2001 at the Konza Prairie Biological Station, Kansas. Abundance of cotton rats was low during autumn (X̄ = 0.57 individuals/trapline) and extremely low in spring (X̄ = 0.04 individuals/trapline). Autumn abundance varied widely in 20 years (range: 0.00–2.50 individuals/trapline) and among 14 sites (0.05–1.35 individuals/trapline). Spring prairie fires had a positive influence on cotton rats during the 1st (X̄ = 0.8 individuals/trapline) and 2nd autumns (X̄ = 1.0 individuals/trapline), but not during the 3rd or later autumns (X̄ = 0.2 individuals/trapline). Cotton rats were associated strongly with lowland prairie relative to breaks and upland prairie. Autumn abundance was correlated positively with previous winter (December–February) average maximum temperature, but was not correlated with previous winter precipitation, summer (June–August) average maximum temperature, summer precipitation, or aboveground net primary productivity. Although previous winter maximum temperature accounted for only 32% of interautumn variation in abundance, winter harshness appears to be the major factor driving temporal variation in autumn abundance of hispid cotton rats.
Keywords: fire; hispid cotton rat; kansas; Sigmodon hispidus; spatial variation; tallgrass prairie; temporal variation; topography

Mycorrhizal symbiosis and insect herbivory in tallgrass prairie microcosms - Kula, A.R.; D.C. Hartnett; G.T. Wilson (Ecology Letters, 2005)

A new species of Epimicta Forster (Hymenoptera: Braconidae) from North America and new distribution records for E. griffithsi Wharton - Kula, R.; Zolnerowich, G. (Proceedings of the Entomological Society of Washington, 2005)

Nitrogen enrichment causes minimal changes in arbuscular mycorrhizal colonization but shifts community composition - evidence from rDNA data - A. Jumpponen; Trowbridge, J.; Mandyam, K.G.; Johnson, L.C. (Biology and Fertility of Soils, 2005)
Intracellular arbuscular mycorrhizal (AM) colonization was compared between nitrogen (NH4NO3) fertilized (10 g N m−2) and nonfertilized tallgrass prairie plots. In the microscopic analyses of host roots, only intracellular coils showed an increasing trend as a result of N fertilization, whereas intracellular colonization by arbuscules, hyphae, or vesicles did not differ between the N treatments. Clone libraries established from pooled PCR products of AM fungi contained exclusively species of Glomus; no other genera were detected indicating that Glomus spp. dominated the host roots. Comparisons between observed and random topologies indicated that cloned sequence placement covaried with N treatment: unique clades within Glomus originated exclusively from N-fertilized or nonfertilized treatments. We conclude that the communities of dominant and most commonly occurring AM fungi changed in response to N amendment, although the root colonization showed minimal or no response.
Keywords: Arbuscular mycorrhiza; Nitrogen deposition; Ribosomal DNA; tallgrass prairie

Partitioning of nitrogen over five growing seasons in tallgrass prairie - Dell, C.J.; Williams, M.A.; C. W. Rice (Ecology, 2005)
Annual spring burning of tallgrass prairie increases plant biomass production despite losses of N and lower net N mineralization. To better understand how burning influences the cycling of N in prairie, 15N was injected to soil as NH4+, and the partitioning between plant and soil N pools was followed over five growing seasons in annually burned and unburned prairie. Applied 15N was rapidly immobilized with <2% and 11% of the 15N remaining in inorganic forms six days after application in burned and unburned prairie, respectively. Seventy-seven percent (burned prairie) and 70% (unburned prairie) of the applied 15N was initially recovered as soil organic N (oN), with a majority accounted for in microbial biomass. Plants contained ∼20% of the applied N with the largest portion recovered from roots regardless of burning. At the end of the first growing season, only 55% of the applied 15N was recovered from the unburned prairie, while 85% was recovered from burned prairie. The total 15N content of the plants changed little during the first growing season, but the portion recovered in the rhizomes increased, indicating belowground N storage. Total recovery and distribution of applied N changed little from the end of the first to the end of the second season growing season. Accumulations of 15N within the plants decreased greatly between the second and fifth growing seasons, but N lost from plants was accounted for in oN. Conservation of N by plants and tight cycling of N within the root zone suggest mechanisms by which prairie can be a highly productive ecosystem despite limited N availability. The immobilization of potentially mineralized N within the root zone increased with burning, offsetting the loss of N to fire probably by reducing leaching and denitrification losses.

Pollinator importance andtemporal variation in a population of Phlox divaricata L. (Polemoniaceae) - Wiggam, S.; Ferguson, C.J. (American Midland Naturalist, 2005)
Temporal variation in climatic conditions is a regular occurrence for most early spring flowering plants in temperate regions, often producing variation in available pollinators. Evaluating the effectiveness and importance of pollinators to a plant population provides an indication of the relative influence of each visitor on a population's reproductive success and selection on floral traits. This study examined pollinator activity and its effect on seed set in a population of Phlox divaricata L. (Polemoniaceae), investigating variation over the 24-h day and the flowering season for two consecutive years. Eleven species, representing three orders of insects, were documented visiting the study population, although lepidopterans (four species, particularly Hemaris diffinis and Megalographa biloba) accounted for 90% of all visitation. The highest visitation rates (and resulting seed set) occurred during the morning and afternoon diurnal time periods and the evening crepuscular time period. The relative frequencies of the different visitors varied over the 24-h day and between flowering seasons. Most visitors that could be evaluated were found to be effective pollinators. Thus, a pollinator's importance to reproductive success was generally dictated by its visitation frequency, H. diffinis being the most important pollinator. This study highlights the importance of considering temporal variation in effective pollinators in species experiencing variable environmental conditions.

Quantifying sediment transport across an undisturbed prairie landscape using cesium-137 and high resolution topography - Kaste, J.M.; Heimsatha, A.M.; Hohmann, M. (Geomorphology, 2005)
Soil erosion is a global environmental problem, and anthropogenic fallout radionuclides offer a promising tool for describing and quantifying soil redistribution on decadal time scales. To date, applications of radioactive fallout to trace upland sediment transport have been developed primarily on lands disturbed by agriculture, grazing, and logging. Here we use 137Cs to characterize and quantify soil erosion at the Konza Prairie Long-Term Ecological Research (LTER) site, an undisturbed grassland in northeastern Kansas. We report on the small scale (< 10 m) and landscape scale (10 to 1000 m) distribution of fallout 137Cs, and show significant variability in the concentrations and amounts of 137Cs in soils at our site. 137Cs soil concentrations and amounts typically vary by 10% to 30% on small scales, which most likely represents the spatial heterogeneity of the depositional processes. Landscape scale variability of soil 137Cs was significantly higher than small scale variability. Most notably, soils collected on convex (divergent) landforms had 137Cs inventories of 2500 to 3000 Bq m− 2, which is consistent with the expected atmospheric inputs to the study area during the 1950s and 1960s. Concave landforms, however, had statistically lower inventories of 1800 to 2300 Bq m− 2. The distribution of 137Cs on this undisturbed landscape contrasts significantly with distributions observed across disturbed sites, which generally have accumulations of radioactive fallout in valley bottoms. Because the upslope contributing area at each sampling point had a significant negative correlation with the soil inventory of 137Cs, we suggest that overland flow in convergent areas dominates soil erosion at Konza on time scales of decades. Very few points on our landscape had 137Cs inventories significantly above that which would be predicted from direct deposition of 137Cs on the soil surface; we conclude therefore that there is little net sediment storage on this undisturbed landscape.
Keywords: Erosion; Geomorphology; grassland; Konza Prairie; Overland flow

Regional patterns in carbon cycling across the Great Plains of North America - McCulley, R.L.; Burke, I.C.; Nelson, J.A.; Lauenroth, W.K.; Alan K. Knapp; Kelly, E.F. (Ecosystems, 2005)
The large organic carbon (C) pools found in noncultivated grassland soils suggest that historically these ecosystems have had high rates of C sequestration. Changes in the soil C pool over time are a function of alterations in C input and output rates. Across the Great Plains and at individual sites through time, inputs of C (via aboveground production) are correlated with precipitation; however, regional trends in C outputs and the sensitivity of these C fluxes to annual variability in precipitation are less well known. To address the role of precipitation in controlling grassland C fluxes, and thereby soil C sequestration rates, we measured aboveground and belowground net primary production (ANPP-C and BNPP-C), soil respiration (SR-C), and litter decomposition rates for 2 years, a relatively dry year followed by a year of average precipitation, at five sites spanning a precipitation gradient in the Great Plains. ANPP-C, SR-C, and litter decomposition increased from shortgrass steppe (36, 454, and 24 g C m−2 y−1) to tallgrass prairie (180, 1221, and 208 g C m−2 y−1 for ANPP-C, SR-C, and litter decomposition, respectively). No significant regional trend in BNPP-C was found. Increasing precipitation between years increased rates of ANPP-C, BNPP-C, SR-C, and litter decomposition at most sites. However, regional patterns of the sensitivity of ANPP-C, BNPP-C, SR-C, and litter decomposition to between-year differences in precipitation varied. BNPP-C was more sensitive to between-year differences in precipitation than were the other C fluxes, and shortgrass steppe was more responsive than were mixed grass and tallgrass prairie.
Keywords: grassland; Great Plains; litter decomposition; Net primary production; Precipitation; Regional trends; soil respiration

Reproductive biology of Lespedeza cuneata - Haller, S.J. (William Jewell College, 2005)

Rodent seed predation and GUDs: effect of burning and topography - Reed, A.W.; Kaufman, G.A.; D.W. Kaufman (Canadian Journal of Zoology, 2005)
We examined the relationships between seed predation and the habitat into which a seed falls, abundance of rodents within that habitat, and foraging pattern of rodents within that habitat. Using seed plots, we assessed seed predation in burned and unburned tallgrass prairies at biweekly intervals between May and September in 2001 and 2002. Significantly more seed was removed from plots in burned than unburned prairies. Rodent abundance did not differ between burned prairie and unburned prairie, although the abundance of omnivorous–granivorous rodents (herbivores excluded) was greater in burned than unburned prairie. Proportion of seed removed in burned and unburned prairies was independent of both total rodent abundance and abundance of omnivorous–granivorous rodents. We also measured giving-up density (GUD) of rodents in burned and unburned prairies during the spring and summer of 2002. GUDs did not differ significantly in burned and unburned prairies. However, rodents had a higher GUD in uplands than in limestone breaks or lowland habitats. Our results suggest that rodent foraging in tallgrass prairie is affected by microhabitat and that rodent abundance is not sufficient to predict seed predation.

Short-term competition for ammonium and nitrate in tallgrass prairie - Dell, C.J.; C. W. Rice (Soil Science Society of America Journal, 2005)
The availability of N limits productivity in tallgrass prairie. Spring burning is common because it results in greater plant productivity despite reducing net N mineralization. To better explain how burning affects inorganic N availability in tallgrass prairie, the partitioning of 15N among plant and soil pools was measured in June and August 1994. Approximately 2.5 μg N g−1 soil was injected as either NH4 or NO3 to a depth of 15 cm within cores in burned and unburned prairie. Cores were removed from the field 6 d after injection, and 15N recovery in plant and soil N pools was determined. No more than 14% of the applied 15N remained in inorganic form 6 d after application. The largest portion of the applied 15N (35–80%) was recovered in the soil organic nitrogen pool (No). Burning significantly increased the immobilization of both NH4 and NO3 within No, and microbial biomass accounted for ≥50% of the 15N recovered in No Accumulation of 15N in plants accounted for ≤35% of the applied 15N with a majority recovered from roots. Burning had little effect on 15N recovery in plants; however, 15N accumulations in roots were significantly greater when NO3 was used. Results indicate that immobilization within soil organic matter (SOM) controls the availability of both NH4 and NO3 to plants. Increased immobilization in soils with burning probably results largely from increased microbial N demand resulting from greater litter inputs with wider C to N ratios. Further research is needed to determine if abiotic mechanisms for N immobilization also significantly influence N availability in prairie soils.

Silica biogeochemistry across a grassland climosequence - Blecker, S.W. (Colorado State University, 2005)

Simulated carbon sink response of shortgrass steppe, tallgrass prairie and forest ecosystems to rising [CO2], temperature and nitrogen input - Pepper, D.A.; Del Grosso, S.J.; McMurtrie, R.E.; Parton, W.J. (Global Biogeochemical Cycles, 2005)
[1] The response of plant ecosystems to environmental change will determine whether the terrestrial biosphere will remain a substantial carbon sink or become a source during the next century. We use two ecosystem models, the Generic Decomposition And Yield model (G'DAY) and the daily time step version of the Century model (DAYCENT), to simulate net ecosystem productivity (NEP) for three contrasting ecosystems (shortgrass steppe in Colorado, tallgrass prairie in Kansas, and Norway spruce in Sweden) with varying degrees of water, temperature, and nutrient limitation, to determine responses to gradual increases in atmospheric CO2 concentration ([CO2]), temperature, and nitrogen input over 100 years. Using G'DAY, under rising [CO2], there is evidence of C sink “saturation,” defined here as positive NEP reaching an upper limit and then declining toward zero, at all three sites (due largely to increased N immobilization in soil organic matter) but a positive C sink is sustained throughout the 100 years. DAYCENT also predicts a sustained C sink at all three sites under rising [CO2], with evidence of C sink saturation for the Colorado grassland and the C sink levels off after 80 years for the Kansas grassland. Warming reduces soil C and the C sink in both grassland ecosystems but increases the C sink in the forest. Warming increases decomposition and soil N mineralization, which stimulates net primary productivity (NPP) at all sites except when inducing water limitation. At the forest site some of the enhanced N release is allocated to a woody biomass pool with a low N:C ratio so that warming enhances NEP without increased N input at the forest site, but not at the grassland sites. Responses to combinations of treatments are generally additive for DAYCENT but more interactive for G'DAY, especially under combined rising [CO2] and warming at the strongly water- and N-limited shortgrass steppe. Increasing N input alleviates C sink saturation and enhances NEP, NPP, and soil C at all sites. At the water-limited grassland sites the effect of rising [CO2] on growth is greatest during the drier seasons. Key sensitivities in the simulations of NEP are identified and include NPP sensitivity to gradual increase in [CO2], N immobilization as a long-term feedback, and the presence or not of plant biomass pools with low N:C ratio.

Soil biotic interactions and carbon dynamics - Watson, G. (Kansas State University, 2005)

Soil heterogeneity effects on tallgrass prairie community heterogeneity: anapplication of ecological theory to restoration ecology - S.G. Baer; Scott. L. Collins; John M. Blair; Fiedler, A.; Alan K. Knapp (Restoration Ecology, 2005)
Spatial heterogeneity of resources can influence plant community composition and diversity in natural communities. We manipulated soil depth (two levels) and nutrient availability (three levels) to create four heterogeneity treatments (no heterogeneity, depth heterogeneity, nutrient heterogeneity, and depth + nutrient heterogeneity) replicated in an agricultural field seeded to native prairie species. Our objective was to determine whether resource heterogeneity influences species diversity and the trajectory of community development during grassland restoration. The treatments significantly increased heterogeneity of available inorganic nitrogen (N), soil water content, and light penetration. Plant diversity was indirectly related to resource heterogeneity through positive relationships with variability in productivity and cover established by the belowground manipulations. Diversity was inversely correlated with the average cover of the dominant grass, Switchgrass (Panicum virgatum), which increased over time in all heterogeneity treatments and resulted in community convergence among the heterogeneity treatments over time. The success of this cultivar across the wide range of resource availability was attributed to net photosynthesis rates equivalent to or higher than those of the native prairie plants in the presence of lower foliar N content. Our results suggest that resource heterogeneity alone may not increase diversity in restorations where a dominant species can successfully establish across the range of resource availability. This is consistent with theory regarding the role of ecological filters on community assembly in that the establishment of one species best adapted for the physical and biological conditions can play an inordinately important role in determining community structure.
Keywords: grassland; Panicum virgatum; restoration; soil heterogeneity; switchgrass; tallgrass prairie

Sources of Sr and implications for weathering of limestone under tallgrass prairie, northeastern Kansas - Wood, H.K.; G. L. Macpherson (Applied Geochemistry, 2005)
Grasslands of north-central Kansas are underlain by carbonate aquifers and shale aquitards. Chemical weathering rates in carbonates are poorly known, and, because large areas are underlain by these rocks, solute fluxes are important to estimating global weathering rates. Grasslands exist where the amount of precipitation is extremely variable, both within and between years, so studies in grasslands must account for changes in weathering that accompany changes in precipitation. This study: (1) identifies phases that dominate chemical fluxes at Konza Prairie Biological Station (KPBS) and Long-Term Ecological Research Site, and (2) addresses the impact of variable precipitation on mineral weathering. The study site is a remnant tallgrass prairie in the central USA, representing baseline weathering in a mid-temperate climate grassland. Groundwater chemistry and hydrology in the 1.2 km2 watershed used for this study suggest close connections between groundwater and surface water. Water levels fluctuate seasonally. High water levels coincide with periods of precipitation plus low evapotranspiration rather than during precipitation peaks during the growing season. Precipitation is concentrated before recharging aquifers, suggesting an as yet unquantified residence time in the thin soils. Groundwater and surface water are oversaturated with respect to calcite within limitations of available data. Water is more dilute in more permeable aquifers, and water from one aquifer (Morrill) is indistinguishable from surface water. Cations other than Ca co-vary with each other, especially Sr and Mg. Potassium and Si co-vary in all aquifers and surface water, and increases in concentrations of these elements are the best indicators of silicate weathering at this study site. Silicate-weathering indices correlate inversely to aquifer hydraulic conductivity. 87Sr/86Sr in water ranges from 0.70838 to 0.70901, and it decreases with increasing Sr concentration and with increasing silicate-weathering index. Carbonate extracted from aquifer materials, shales, soil, and tufa has Sr ranging from about 240 (soil) to 880 ppm (Paleozoic limestone). 87Sr/86Sr ranges from 0.70834 ± 0.00006 (limestone) to 0.70904 ± 0.00019 (soil). In all cases, 87Sr/86Sr of aquifer limestone is lower than 87Sr/86Sr of groundwater, indicating a phase in addition to aquifer carbonate is contributing solutes to water. Aquifer recharge controls weathering: during periods of reduced recharge, increased residence time increases the total amount of all phases dissolved. Mixing analysis using 87Sr/86Sr shows that two end members are sufficient to explain sources of dissolved Sr. It is proposed that the less radiogenic end member is a solution derived from dissolving aquifer material; longer residence time increases its contribution. The more radiogenic end member solution probably results from reaction with soil carbonate or eolian dust. This solution dominates solute flux in all but the least permeable aquifer and demonstrates the importance that land-surface and soil-zone reactions have on groundwater chemistry in a carbonate terrain.

Taxon-dependent scaling: beetles, birds, and vegetation at four North American grassland sites - Bossenbroek, J.M.; Wagner, H.H.; Wiens, J.A. (Landscape Ecology, 2005)
Because organisms respond to the environment at different scales, it is important to develop ways of determining the appropriate scales for a specific ecological process and organism. We consider whether the relative importance of different scales is associated with organism mobility, and whether this relationship is independent of landscape characteristics. We observed abundances of particular species for vascular plants, ground-dwelling beetles and breeding birds along eight 2-km transects of 40 sampling stations each, distributed over four sites along the regional gradient from shortgrass steppe in central Colorado to tallgrass prairie in central Kansas. For each transect and taxonomic group, the relative importance of factors measured at the trap scale (1 m; soil texture and hardness, vegetation height, bare ground), at the local scale (10 m; density of shrubs and cacti) and at the landscape scale (30 m; Landsat 7 TM spectral bands, slope and elevation) was assessed using hierarchical canonical variance partitioning with forward selection of explanatory variables. Plant, beetle and bird community composition was explained by environmental factors measured at all three scales. Factor influence was more consistent between transects and between plants and beetles for the more homogeneous landscapes of the shortgrass steppe than for the more heterogeneous landscapes of the tallgrass prairie. We conclude that, independent of the mobility of a taxonomic group, factors at several scales are important in explaining community composition. The importance of different scales shifts along a regional gradient, and the variability between sites is high even for nearby sites.
Keywords: Canonical correspondence analysis; Colorado; Hierarchical-variance partitioning; Kansas Species–environment relationships; prairie

A test for community change using a null model approach - Schaefer, J.; K. B. Gido; M.D. Smith (Ecological Applications, 2005)
Quantifying patterns of temporal or spatial change in community structure is critical for assessing the impact of disturbances on biological systems and the stability of ecosystems. Detecting change in communities can be problematic, however, because of the inherent variability of systems and limitations of commonly used methods, such as similarity indices and ordination that do not explicitly test a hypothesis. Here we present empirical data to show a strong relationship between species mean abundance and variability across three broad taxonomic groups (plants, zooplankton, and fish). These statistical relationships were then used to construct null models of expected community variability that were used to test against the observed temporal change of these communities. We evaluated the ability of this approach to detect significant temporal change above that associated with random variation with nine communities (three Midwestern stream fish, three north temperate zooplankton, and three tallgrass prairie plant), each having long-term data sets and different expected levels of change. Nonrandom change was detected in 21.3% of samples from the expected low-change communities, 52.6% in moderately changed communities, and 60.4% in high-change communities. Thus, this approach was effective in detecting change over time in those communities expected to change most. By using empirical relationships between species abundance and variability, this null model approach provides ecologists and resource managers an objective tool, which can be used along with existing community indices and statistical techniques to assess the type and magnitude of community change with limited data sets.

Using local seed in prairie restoration - Gustafson, D.J.; D.J. Gibson; Nickrent, D.L. (Native Plants Journal, 2005)
Choice among local, non-local, and cultivar seeds for restoring native ecosystems is not purely an academic question—it also has practical consequences.In this article we summarize a series of genetic and competition studies of big bluestem (Andropogon gerardii Vitman. [Poaceae]), Indian grass (Sorghastrum nutans (L.) Nash. [Poaceae]), and purple prairie clover (Dalea purpurea Vent.[Fabaceae]) from remnant and restored Illinois (local) prairies, non-local remnant prairies, and 6 grass cultivars. We found genetic differences between local and non-local seed sources, that large populations do not necessarily have higher genetic diversity relative to small populations, and differences in plant performance could be related to seed source. Although obtaining large quantities of non-local and cultivar grass seeds may be affordable, available, and desirable given the amount of seeds required for prairie restoration, our research indicates genetic and plant performance differences between local and non-local seed sources in all 3 species. Such differences can affect both the short- and long-term success of restoration activities.
Keywords: Andropogon gerardii; cultivars; Dalea purpurea; Ecotype; Fabaceae; Poaceae; remnant and restored grasslands; Sorghastrum nutans

Using radio-telemetry to determine range and resourcerequirements of Upland Sandpipers at an experimentally managed prairielandscape - Mong, T.W. (Kansas State University, 2005)
The native grasslands of North America are highly fragmented, and remaining tracts are intensively managed for grazing. Loss of tallgrass prairie and changing land management practices has caused many grassland birds that rely on these areas for breeding to decline in population numbers. To investigate resource selection and area use requirements of the upland sandpiper, we outfitted birds with radio transmitters at the experimentally managed Konza Prairie Biological Station in northeast Kansas. Two logistical challenges for wildlife telemetry projects are: minimizing the impact of radios on survival and movement, and optimizing the duration of transmitter attachment. We compared 4 methods of radio attachment for upland sandpipers under field conditions at breeding sites in tallgrass prairie. The daily probabilities of radio retention (DRR) for our 4 attachment methods were: 0.9992 (SE = 0.0005, n = 85) for a leg loop harness, 0.9801 (SE = 0.0099, n = 11) for radios glued to clipped feathers, 0.9627 (SE = 0.0085, n = 25) for radios glued directly to feathers and 0.8538 (SE = 0.0322, n = 20) for radios glued to plucked skin. The expected duration of radio attachment ranged from 1290 days for the leg loop harness, and 6 to 50 days for the glue attachment techniques. Survival rates of males (DSR = 0.9987, SE = 0.0009, n = 53) and females (DSR = 0.9988, SE = 0.0008, n = 71) were similar, and the probability of surviving the 90-day breeding season was about 0.90 in both sexes. We recommend attaching radios with glue to clipped feathers for short-term telemetry studies and a leg loop harness if longer retention is desired. The unique landscape of Konza Prairie allowed us to investigate specific tallgrass management strategies, and their impact on the range and habitat requirements of a bird that relies on the prairie for breeding. We found that upland sandpipers have large home ranges during the breeding season (male: = 199.0 ha ± 40.5 SE, n = 21, female: = 247.7 ha ± 51.7 SE, n = 23). Male home ranges were twice as large during brood-rearing ( = 200.8 ha ± 69.1 SE, n = 9) than during the nesting period ( = 67.02 ha ± 11.84 SE, n = 14, 1 = 5.14, P = 0.023). Upland sandpipers selected home range sites that had been burned the same spring (n = 44, ²3 = 31.65, P < 0.001), but did not show preference for certain habitat types within their home range ( ²3 = 1.49, P = 0.685). During brood rearing upland sandpipers used sites with higher percentages of bare ground, herbaceous and short woody vegetation, and low amounts of vegetative litter. Management strategies for the upland sandpiper should seek to preserve large contiguous tracts of tallgrass prairie that receive a heterogeneous mix of burning and grazing.
Keywords: Compositional analysis; Resource selection; Retention rate; Upland Sandpiper; Utilization distribution

Vegetationtrends in tallgrass prairie from bison and cattle grazing - Towne, E.G.; D.C. Hartnett; Cochran, R.C. (Ecological Applications, 2005)
Comparisons between how bison and cattle grazing affect the plant community are understood poorly because of confounding differences in how the herbivores are typically managed. This 10-year study compared vegetation changes in Kansas (USA) tallgrass prairie that was burned and grazed season-long at a moderate stocking rate by either bison or cattle. We held management practices constant between the herbivores and equalized grazing pressure by matching animals so that the total body mass in all pastures was similar each year. Trends in species cover and diversity indices in the bison and cattle pastures were compared with ungrazed prairie that also was burned annually. We found that little bluestem (Schizachyrium scoparium) cover decreased over time in bison pastures, and big bluestem (Andropogon gerardii) cover increased over time in cattle pastures. Grazing by either herbivore increased the canopy cover of annual forbs, perennial forbs, and cool-season graminoids, but both annual and perennial forb cover increased at a greater rate in bison pastures than in cattle pastures. Missouri goldenrod (Solidago missouriensis) and heath aster (Symphyotrichum ericoides) were primarily responsible for the increased forb cover in grazed pastures. Species richness at both small (10 m2) and large (200 m2) spatial scales increased at a greater rate in bison pastures than in cattle pastures, but richness did not change through time in ungrazed prairie. The number of annual forb species was significantly higher in bison pastures than in pastures grazed by cattle. Residual graminoid biomass at the end of the grazing season was lower in bison pastures than in cattle pastures, whereas forb residuum increased over time at a greater rate in pastures grazed by bison than in pastures grazed by cattle. Although bison and cattle differentially altered some vegetation components, the plant communities in bison and cattle pastures were 85% similar after 10 years of grazing. We conclude that most measurable differences between bison-grazed and cattle-grazed pastures in tallgrass prairie are relatively minor, and differences in how the herbivores are typically managed may play a larger role in their impact on prairie vegetation than differences between the species.

Woody plant encroachment and removal in mesic grassland: production and composition responses of herbaceous vegetation - Lett, M.S.; Alan K. Knapp (American Midland Naturalist, 2005)
The clonal shrub Cornus drummondii is rapidly displacing mesic grassland in the central U.S. due to fire suppression and changes in land use. Once established, this shrub is not readily eliminated by the return of frequent fire, leading to significant and perhaps irreversible shifts in tallgrass prairie structure and function. We assessed the impacts of C. drummondii encroachment on herbaceous aboveground net primary production (ANPP) and plant community structure in tallgrass prairie and the role this species plays in the conversion of grassland ecosystems to shrub/woodlands. We also removed established C. drummondii clones to assess the potential of the grassland ecosystem to recover after shrub dominance. Aboveground net primary production, vegetative cover and species richness and diversity (exclusive of C. drummondii) were significantly reduced beneath shrub islands relative to open grassland, with reductions in ANPP and richness of up to 94 and 45%, respectively. Forbs were the dominant growth form in the C. drummondii understory, and 10 species primarily associated with woodland habitats occurred only within shrub islands. Upon removal of C. drummondii, ANPP, richness and diversity recovered to grassland values within 2 y; however, forbs remained the dominant growth form, comprising 73% of total cover. These results indicate that C. drummondii exerts strong control over the structure and function of unburned mesic grassland ecosystems and that this shrub may be key in the conversion of grasslands to woodlands. Removal of C. drummondii resulted in some aspects of recovery, but the return of graminoid dominance was not attained after 2 y. This represents a legacy effect of C. drummondii of unknown duration. Prevention of woody species encroachment through frequent burning is a preferred management option for this ecosystem.

Algal-bacterial co-variation in streams: a cross-stream comparison - Gao, X.; Olapade, O.A.; Kershner, M.W.; Leff, L.G. (Archive fur Hydrobiologie, 2004)
Algal-bacterial co-variation has been frequently observed in lentic and marine environments, but the existence of such relationships in lotic ecosystems is not well established. To examine possible co-variation, bacterial number and chlorophyll-a concentration in water and sediments of nine streams from different regions in the USA were examined. In the water, a strong relationship was found between chlorophyll concentration and bacterial abundance. There was not a significant linear relationship between the abundance of sediment bacteria and sediment or water chlorophyll concentration. The linear regression results obtained between bacterial numbers and chlorophyll concentration in water were generally similar to those reported in other studies on lentic and marine systems suggesting that factors that cause this co-variation may be similar.
Keywords: Algae; Bacteria; Chlorophyll; Doc; stream

Barley yellow dwarf disease in natural populations of dominant tallgrass prairie species in Kansas - Garrett, K.A.; Dendy, S.P.; Power, A.G.; Blaisdell, G.K.; Alexander, H.M.; McCarron, J.K. (Plant Disease, 2004)
The grasses Sorghastrum nutans (Indian grass), Schizachyrium scoparium (little bluestem), Panicum virgatum (switchgrass), and Andropogon gerardii (big bluestem) are four of the most common plant species present in a tallgrass prairie (1). Infection with barley yellow dwarf virus (BYDV, family Luteoviridae) is of interest in these species because of the potential effects of the virus on tallgrass prairie plant communities and the potential for tallgrass prairie to function as a reservoir of the virus for infection in wheat or barley fields. In a previous inoculation experiment, an unidentified strain of BYDV transmitted by the aphid species Rhopalosiphum padi was reported to infect S. scoparium but none of the other three grass species (2). We sampled for the presence of five virus strains in at least 50 blooming plants of each grass species in a natural tallgrass prairie stand in August 2000. Samples were collected in watersheds that were designated 1B, 1D, K1A, 20B, and 20C at Konza Prairie Biological Station in the Flint Hills near Manhattan, KS. To detect the virus, we used enzyme-linked immunosorbent assay (ELISA) with antibodies purchased from Agdia (Elkhart, IN). For the PAV, MAV, RMV, and SGV strains, we used double-antibody sandwich ELISA with alkaline phosphatase label. For Cereal yellow dwarf virus (RPV), we used compound direct ELISA with alkaline phosphatase label. The scoring of ELISA results was based on comparison with infected and uninfected control plants of the same species. Symptoms of infection in the field were difficult to interpret visually, since plants in this natural environment often showed multiple symptoms of stress. None of the five strains were detected in 51 individuals of S. nutans. For 50 individuals of S. scoparium, the incidence of infection by the different strains was 4% for MAV, 0% for PAV, 2% for RMV, 0% for RPV, and 58% for SGV. For 51 individuals of P. virgatum, the incidence of infection was 31% for MAV, 0% for PAV, 0% for RMV, 0% for RPV, and 4% for SGV. For 64 individuals of A. gerardii, the incidence of infection was 59% for MAV, 0% for PAV, 0% for RMV, 0% for RPV, and 3% for SGV. The impact of BYDV on these tallgrass prairie species remains to be determined. The PAV strain is the most commonly reported strain in wheat in Kansas but was not recovered from these grass species.

Belowground bud banks and meristem limitation in tallgrass prairie plant populations - Benson, E.; D.C. Hartnett; Mann, K. (American Journal of Botany, 2004)
Rhizome meristem populations were sampled in tallgrass prairie to quantify the size, grass : forb composition, and temporal and spatial variability of the soil bud bank and to compare fire effects on bud bank and seed bank composition. Soil cores (10.5 cm diameter, 15 cm deep) were collected from replicate annually and infrequently burned tallgrass prairie sites, and intact rhizomes and rhizome buds were censused. Bud bank densities ranged from approximately 600 to 1800 meristems/m2 among sites and had high spatial and seasonal variability. In annually burned prairie, the total bud bank density was two-fold greater and the grass : forb meristem ratio was more than 30-fold greater than that of infrequently burned prairie. These patterns are opposite those observed in soil seed banks at this site. The rhizome population in annually burned prairie was 34% larger than the established aboveground tiller population. By contrast, the bud bank density in unburned prairie was significantly lower than aboveground stem densities, indicating possible belowground meristem limitation of stem density and net primary production on infrequently burned prairie. The patterns observed in this study suggest that the densities and dynamics of tallgrass prairie plant populations, as well as their response to disturbance (e.g., fire and grazing) and climatic variability, may be mediated principally through effects on the demography of belowground bud populations. Patterns of seed reproduction and seed bank populations have little influence on short-term aboveground population dynamics of tallgrass prairie perennials.
Keywords: fire; Rhizomes; Seed bank; tallgrass prairie

Bison wallows: community assembly and population dynamics in isolated ephemeral aquatic habitats of the tallgrass prairie - N.M. Gerlanc (Kansas State University, 2004)

Carbon and nitrogen pools in a tallgrass prairie soil under elevated carbon dioxide - Williams, M.A.; C. W. Rice; Omay, A.; Owensby, C. (Soil Science Society of America Journal, 2004)
Soil is a potential C sink and could offset rising atmospheric CO2 The capacity of soils to store and sequester C will depend on the rate of C inputs from plant productivity relative to C exports controlled by microbial decomposition. Our objective was to measure pools of soil C and N to assess the potential for C accrual and changes to N stocks as influenced by elevated atmospheric CO2 Treatments (three replications, randomized complete block design) were ambient CO2—no chamber (NC), ambient CO2—chamber (AC), and two times ambient CO2—chamber (EC). Long-term (290 d) incubations (35°C) were conducted to assess changes in the slow soil fractions of potentially mineralizable C (PMC) and potentially mineralizable N (PMN). Potentially mineralizable C was enhanced (P < 0.1) by 19 and 24% in EC relative to AC and NC soil at the 0- to 5- and 5- to 15-cm depths, respectively. Potentially mineralizable N was significantly greater by 14% at the 0- to 5-cm depth in EC relative to AC, but decreased by 12% in EC relative to NC (P < 0.1). Measurements of PMC indicate that increases in total soil C under elevated CO2 in a previous study were a consequence of accrual into the slow pool. Relatively large amounts of new C deposited as a result of elevated CO2 (Cnew) remained in the soil after the 290-d incubation. In contrast to accumulation of C into the slow fraction, Cnew was integrated into a passive fraction of soil organic matter (SOM). Accumulation of N was also detected in the whole soil, which cannot be explained by current estimates of ecosystem N flux.

Carbon and nitrogen stoichiometry and nitrogen cycling rates in streams - W. K. Dodds; Marti, E.; Tank, J.; Pontius, J.L.; Hamilton, S.K.; Grimm, N.B.; W.B. Bowden; W.H. McDowell; Peterson, B.J.; Valett, H.M.; Webster, J.R.; Gregory, S. (Oecologia, 2004)
Stoichiometric analyses can be used to investigate the linkages between N and C cycles and how these linkages influence biogeochemistry at many scales, from components of individual ecosystems up to the biosphere. N-specific NH4 + uptake rates were measured in eight streams using short-term 15N tracer additions, and C to N ratios (C:N) were determined from living and non-living organic matter collected from ten streams. These data were also compared to previously published data compiled from studies of lakes, ponds, wetlands, forests, and tundra. There was a significant negative relationship between C:N and N-specific uptake rate; C:N could account for 41% of the variance in N-specific uptake rate across all streams, and the relationship held in five of eight streams. Most of the variation in N-specific uptake rate was contributed by detrital and primary producer compartments with large values of C:N and small values for N-specific uptake rate. In streams, particulate materials are not as likely to move downstream as dissolved N, so if N is cycling in a particulate compartment, N retention is likely to be greater. Together, these data suggest that N retention may depend in part on C:N of living and non-living organic matter in streams. Factors that alter C:N of stream ecosystem compartments, such as removal of riparian vegetation or N fertilization, may influence the amount of retention attributed to these ecosystem compartments by causing shifts in stoichiometry. Our analysis suggests that C:N of ecosystem compartments can be used to link N-cycling models across streams.
Keywords: carbon; Carbon:Nitrogen ratio; nitrogen; stoichiometry; streams

Comparison of hyperspectral and multispectral data for estimating leaf area index in four biomes - Lee, K-S.; Cohen, W.B.; Kennedy, R.E.; Maiersperger, T.K.; Gower, S.T. (Remote Sensing of Environment, 2004)
Motivated by the increasing importance of hyperspectral remote sensing data, this study sought to determine whether current-generation narrow-band hyperspectral remote sensing data could better track vegetation leaf area index (LAI) than traditional broad-band multispectral data. The study takes advantage of a unique dataset, wherein field measurements of LAI were acquired at the same general time and grain size as both Landsat ETM+ and AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) imagery in four different biomes. Biome types sampled included row-crop agriculture, tallgrass prairie, mixed hardwood-conifer forest, and boreal conifer forest. The effects of bandwidth, band placement, and number of bands were isolated from radiometric quality by comparing regression models derived from individual AVIRIS channels with those derived from simulated ETM+ and MODIS channels using the AVIRIS data. Models with selected subsets of individual AVIRIS channels performed better to predict LAI than those based on the broadband datasets, although the potential to overfit models using the large number of available AVIRIS bands is a concern. Models based on actual ETM+ data were generally stronger than those based on simulated ETM+ data, suggesting that, for predicting LAI, ETM+ data suffer no penalty for having lower radiometric quality. NDVI was generally not sensitive to LAI at the four sites. Band placement of broad-band sensors (e.g., simulated ETM+ and MODIS) did not affect relationships with LAI, suggesting that there is no inherent advantage to MODIS spectral properties over those of ETM+ for estimating LAI. Spectral channels in the red-edge and shortwave-infrared regions were generally more important than those in the near-infrared for predicting LAI.
Keywords: Hyperspectral; LAI; Multispectral

Competition and coexistence in grassland co-dominants: responses to neighbor removal and resource availability - Silletti, A.M.; Alan K. Knapp; John M. Blair (Canadian Journal of Botany, 2004)
We examined the role of interspecific competition in the regulation of abundance and coexistence of the dominant grasses in tallgrass prairie using a removal experiment with Andropogon gerardii Vitman and Sorghastrum nutans L. Nash, two of the most abundant grasses in tallgrass prairie. Plant removal treatments (using foliar herbicide), applied to 0.3-m2 plots at the Konza Prairie Biological Station (northeast Kansas, USA), included removal of all A. gerardii, removal of all S. nutans, and no removal. To determine whether soil fertility altered the outcome, we included a fertilizer addition treatment (10 g N·m2) fully crossed with the removal treatments. Andropogon gerardii removal resulted in significantly increased net photosynthesis, stomatal conductance, and tiller mass in S. nutans. Sorghastrum nutans removal had little effect on A. gerardii, suggesting asymmetric competition. Fertilizer significantly increased tiller mass and flowering stalk production in S. nutans, but had little effect on A. gerardii. The ability of A. gerardii to suppress the performance of S. nutans is consistent with the greater abundance of A. gerardii over much of the tallgrass prairie, while the ability of S. nutans to take advantage of increased resources may be one mechanism by which it avoids competitive exclusion. Because of the greater variability in the performance of S. nutans than in that of A. gerardii, any natural or anthropogenic alterations to this grassland that lead to shifts in dominance between these species may affect ecosystem productivity and stability.Key words: Andropogon gerardii, competition, grassland, neighbour removal, photosynthesis, Sorghastrum nutans, tallgrass prairie.

Competitive relationships of Andropogon gerardii (big bluestem) from remnant and restored native populations and select cultivated varieties - Gustafson, D.J.; D.J. Gibson; Nickrent, D.L. (Functional Ecology, 2004)
1Although genetic differentiation among plant populations is well known, its relevance for preserving the integrity of native ecosystems has received little attention. In a series of competition experiments with Andropogon gerardii Vitman, a dominant species of the North American Tallgrass Prairie, plant performance was related to seed provenance and restoration activities. 2Glasshouse experiments showed plant performance to be a function of seed source. Differential target plant performance relative to competitor identity was observed when plant performance was assessed across a range of competitor densities. Local and non-local plants were larger when competing against non-local plants relative to the local and cultivar plants, while cultivar plants were consistently larger than local and non-local plants regardless of competitor identity or density. The consistency of cultivar performance could reflect directional selection during cultivar development for consistently high fecundity, vigorous vegetative growth and resistance to pathogens. 3In a field experiment, non-local plants were half the size of local and cultivar plants, supporting recognition of seed provenances of A. gerardii based on differences in plant performance among source populations observed in the glasshouse study, and previous genetic analyses of the same populations. 4This study establishes that seed provenance and restoration activities influence the competitive ability of a dominant species which, in turn, may affect plant community structure and potential ecosystem function.

Conservation genetics of two co-dominant species in the endangered tallgrass prairie ecosystem - Gustafson, D.J.; D.J. Gibson; Nickrent, D.L. (Journal of Applied Ecology, 2004)
1. Global habitat fragmentation and loss of undisturbed grasslands has led to the use of non-local seed and cultivars in restoration. There is concern that these sources may be genetically depauperate and their introduction may lead to loss of unique local genotypes. Within this context we considered the issue with regard to the once widespread but now highly fragmented North American tallgrass prairie. 2. We characterized the genetic diversity and genetic relationships of the co-dominant species in this system, big bluestem Andropogon gerardii and Indian grass Sorghastrum nutans, from seven remnant and six restored local tallgrass prairies, a non-local remnant prairie, and five cultivated varieties. 3. Randomly amplified polymorphic DNA (RAPD) analysis of these grasses showed that genetic diversity was mostly retained within rather than among populations, and did not differ among restored or remnant populations or cultivars. 4. Genetic diversity estimates were not correlated with the area of the grassland, nor was there a clear association between diversity and species abundance. All of the restored grasslands in this study were established with seed from at least two local populations and were as genetically diverse as remnant sites. 5. Principal components analysis of RAPD band frequencies showed that the local remnant and restored populations were genetically different from the non-local remnant grasslands and were consistently different to the cultivars. The genetic relationships among local remnant and restored populations reflected biogeography and human activities. 6. Synthesis and applications. Restoration practitioners have often assumed that small populations are genetically depauperate and therefore the need for multiple seed sources to increase genetic diversity outweighs concerns over potential genetic differences among widespread species. Our research, however, indicates that genetic diversity is much less of an issue in these perennial outcrossing autopolyploid grasses than genetic differences among local and non-local or cultivar seed sources. Combining these results with our previous research, indicating differences in plant performance as a function of the source population, suggests that genetic differences and ecological performance among local and non-local seed sources are more of a concern than genetic diversity. Translocating non-local seed in order to increase diversity, or using cultivars, is likely to alter the genetic structure of remnant populations and potentially influence the associated community and affect ecosystem structure and function in unforeseen ways.

On the construction and calibration of dual probe heat capacity sensors - J.M. Ham; Benson, E.J. (Soil Science Society of America Journal, 2004)
Dual-probe heat-capacity (DPHC) sensors can be used to measure soil heat capacity (C), water content, and temperature. Research was conducted to test design factors that affect sensor calibration, including: (i) calibration media, (ii) diameter and length of the needle probes, (iii) sensor body material, and (vi) duration and total power of the applied heat pulse. All sensors were calibrated in media with known C, including: agar (water), water-saturated glass beads, and dry glass beads. Calibration consisted of collecting heat pulse data in a given media and then calculating the apparent probe spacing (r app, distance between heater and detector needles) that yielded correct value of C An ideal sensor would have the same r app regardless of media type. The r app for all sensor designs increased as C decreased, on average changing by 6.7% between agar and dry beads. This undesirable result was consistent with previous studies that showed DPHC sensors calibrated in agar overestimated C in drier soils. Needle diameter (1.27 vs. 1.65 mm), sensor body material (urethane vs. high-conductivity epoxy), and shortening of the detector probe had a small effect on r app Sensors made with urethane bodies, 1.27-mm diam. needle probes, and shortened temperature probes showed less sensitivity to calibration media and are therefore recommended. The r app for this design only increased by 2.6% between dry and water-saturated wet beads. Apparent probe spacing was not affected by changes in total applied power (400–1600 J m−1) or heat pulse duration (2–16 s) when the correct analytical model was used to compute C

Convergence across biomes to a common rain-use efficiency - Huxman, T.E.; M.D. Smith; Fay, P.A.; Alan K. Knapp; Shaw, M.R.; Loik, M.E.; Smith, S.D.; Tissue, D.T.; Zak, J.C.; Weltzin, J.F.; Pockman, W.T.; Sala, O.E.; et al. (Nature, 2004)

Cytogenetic characterization and disease resistance of perennial grasses and disease response to host diversity - Cox, C.M. (Kansas State University, 2004)

Determining landscape structure and heterogeneity using image texture indices - Gao, J.; Goodin, D.G. (2004)

Direct and indirect effects of fire on shrub density and aboveground productivity in a mesic grassland - Heisler, J.L.; J. M. Briggs; Alan K. Knapp; John M. Blair; Seery, A. (Ecology, 2004)
Determinants of the balance between grass and woody vegetation in grasslands and savannas have received considerable attention because of the potential for dramatic shifts in ecosystem structure and function as one growth form replaces the other. We studied a mesic grassland where recently established “shrub islands” are increasing in abundance due to fire suppression. Our objective was to assess the role of the direct effects of fire vs. indirect alterations in resource availability (N and light), as mechanisms that may constrain/facilitate shrub (Cornus drummondii) encroachment. The direct effects of fire in 2001 and 2002 were 100% aboveground mortality of C. drummondii shoots and removal of the detrital layer. Post-fire resprouting resulted in ∼600% increase in stem density compared to a 200% increase in shrub islands protected from fire. In burned shrub islands with an added detrital layer, temperature and light penetration to the soil surface were reduced (by 6.5°C and to <3% of full sunlight), but stem density still increased by ∼400%. Thus, both the direct effects of fire and the indirect effect on the energy environment increased C. drummondii stem densities. In contrast, N additions did not influence new stem production or aboveground net primary productivity (ANPP; grams per square meter per year), suggesting that N availability did not constrain shrub growth during this study. While fire did not impact total ANPP, it did shift the relative abundance of growth forms. Grass productivity (360.7 ± 20.1 g/m2 [mean ± 1 se]) was stimulated (an increase of ∼30%) by the high light conditions of the post-fire environment, while C. drummondii ANPP (34.2 ± 2.4 g/m2) was reduced by ∼30%. In shrub islands protected from fire, C. drummondii ANPP was greatest (50.4 ± 2.2 g/m2), whereas lower graminoid ANPP (282.5 ± 19.9 g/m2) was observed. The persistence of woody vegetation, despite two successive fires, along with a significant reduction in grass ANPP (∼30%) suggests that once established, C. drummondii can persist and exclude C4 grasses. Thus, restoring fire to mesic grasslands may prevent further conversion to shrub/woodland, but the abundance of shrubs is likely to remain unchanged with community structure co-dominated by multiple growth forms.

Dominance not diversity determines invasibility of tallgrass prairie - M.D. Smith; Wilcox, J.; Kelly, T.; Alan K. Knapp (Oikos, 2004)
Many recent studies suggest that more diverse communities are more resistant to invasion. Community characteristics that most strongly influence invasion are uncertain, however, due to covariation of diversity with competition and crowding. We examined separately the effects of species richness and dominance on invasion by an exotic legume, Melilotus officinalis, in intact, native Kansas grassland. We manipulated dominance of C4 grasses by reducing their abundance (i.e. ramet densities) by ∼25 and 50%. In addition, richness was reduced by removing species that were mainly rare and uncommon as might be expected with environmental changes such as drought and fragmentation. In both years of the study (2001–2002), invasibility, measured as peak establishment of Melilotus, was not affected by a 3-fold reduction in species richness, nor was there an interaction between loss of species and reduced dominance on invasion. In contrast, reductions in abundance of the dominants significantly reduced invasibility of the grassland plots in both years. Because the abundance of dominants was highly correlated with measures of competition (i.e. ratio of dominant biomass to total biomass) and crowding (total stem densities), this pattern was opposite to that expected if competition were indeed limiting invasion. Rather, invasion appeared to be facilitated by the dominant species, most likely because reduced dominance increased environmental stress. Our results suggest that dominance is the key community characteristic determining invasibility, because highly competitive and space-filling species can either enhance or reduce susceptibility to invasion depending on whether dominants create a more competitive environment or alleviate stressful conditions.

Eastern moles on the Konza Prairie Biological Station - O'Neal, P.R.; D.W. Kaufman (Transactions of the Kansas Academy of Science, 2004)
We examined the local distribution of the eastern mole (Scalopus aquaticus) along the Kings Creek drainage on the Konza Prairie Biological Station (located south of Manhattan, Kansas). Our 46-ha study site included primarily intermixed riparian woodland and native and planted grassland. Within this site, we surveyed burrow ridges and soil mounds of eastern moles in 116 circular sampling plots. Each sampling plot had a 10-m radius; total surface area of plots was 3.6 ha. Plots were placed at 40-m intervals along 13 transects, which paralleled each other and were 100 m apart. Eastern moles were associated with wooded vegetation (i.e. plots under tree canopy). Eastern moles also were associated positively with bare soil (plots with >2 m2 as contrasted to those with <2 m2 of bare soil). This positive association with plots that had >2 m2 of bare soil held even for the 74 local sites that were under tree canopy along Kings Creek. The association with wooded areas along Kings Creek was consistent with past studies that found eastern moles selectively choose relatively loose, moist soils.
Keywords: eastern mole; habitat association; kansas; Konza Prairie; Scalopus aquaticus

The effect of solar zenith angle and sensor view angle on observed patterns of spatial structure in tallgrass prairie - Goodin, D.G.; Gao, J.; Henebry, G.M. (IEEE Transactions on Geoscience and Remote Sensing, 2004)
While it has long been recognized that the anisotropic reflectance properties of a natural surface affect the intensity and spectral distribution of radiance received by a remote sensing instrument, the effects of canopy reflectance geometry on the observed spatial structure of canopy reflectance have not adequately been evaluated. In this paper, near-surface spectrometers were used as part of two experiments to evaluate the systematic variations in the sun-target-sensor geometry on semivariogram metrics (range, sill+nugget variance) summarizing the spatial structure observed in a tallgrass prairie canopy. In the first experiment, reflectance measurements and normalized difference vegetation index (NDVI) values were collected at five sensor viewing angles (-50°, -25°, 0°, 25°, and 50°) from six measurement grids representing three burn treatments and two slope/aspect situations. In the second experiment, data were collected at 2-h intervals, beginning at ≈0800 LST from the same grids with the radiometer at nadir, allowing the spatial structure of reflectance and NDVI to be observed under naturally changing illumination. Results of the geostatistical analysis show that both the range and sill+nugget variance values change with viewing angle. These effects were consistent across all treatments and slope/aspect combinations. However, when viewed from nadir, the sill+nugget variance values of the canopy changed with solar illumination angle and the range values remained nearly constant. These relationships were also observed across all treatments and slope/aspect combinations. The results suggest that sill+nugget values for the same surface may not be directly comparable if not acquired under very similar view angle and illumination conditions. Range values are comparable if the nadir view is used, but not under off-nadir viewing conditions. The implications of these findings point to the need for caution in interpreting spatial structure derived from close-range radiometry or from satellite/aircraft instruments with cross-track or off-nadir pointing capabilities, and in the comparison of images acquired under varying illumination conditions.

Effects of fire and grazing on small-scale spatial heterogeneity in a tallgrass prairie - van Veen, G.F (Groningen University, 2004)
1. Grazing and fire are historically two important factors in the development and maintenance of many grassland systems. Most previous studies investigated their effects separately. We conducted a study to gain insight in the effects of fire, grazing and their interaction on small-scale (0.25 m2) vegetation heterogeneity and distribution of resources. In four different treatments (IU = annually burned, ungrazed, 4U = 4-year burned, ungrazed, I G = annually burned, grazed, 4G = 4-year burned, grazed) we measured plant species composition and resource availability. 2. Grazing had a positive effect on species richness, diversity and evenness, while it decreased the dominance of C4-grasses (e.g. Andropogon gerardii). Fire had an opposite effect, it reduced species richness, diversity and evenness and enhanced the cover of C4- grasses. The effect of fire was stronger in the absence of grazing. 3. Heterogeneity in the plant community was increased under grazing, whereas fire or a fire-grazing interaction had no significant effect on a small scale (0.25 m2). The increased heterogeneity in grazed sites was strongly correlated with increased resource availability, and not with enhanced patchiness in resources distribution. 4. The availability of resources (light and N) was only affected by the grazing treatment. No spatial patterns in resource distribution were found in the present study. 5. We conclude that grazing is the most important factor on the small scale, I determining the resource availability, vegetation composition and heterogeneity

Effects of food supplementation on female nest attentiveness and incubation Mate-feeding in two sympatric wren species - Pearse, A.T.; Cavitt, J.F.; Cully, J.F. (Wilson Bulletin, 2004)
We examined effects of incubation mate feeding on female incubation behavior and correlates of fitness by providing female Bewick's Wrens (Thryomanes bewickii) and House Wrens (Troglodytes aedon) with food supplements. Males of these species vary in their rates of feeding; Bewick's Wrens feed their incubating mates frequently, whereas House Wrens seldom engage in this behavior. Average length of incubation bout and nest attentiveness (proportion of time spent on the nest) were higher for supplemented female Bewick's Wrens and House Wrens compared to controls. Furthermore, mates of supplemented Bewick's Wrens provisioned females at lower rates than controls, and their rate of feeding was inversely correlated with ambient temperature. Incubation length and hatching success were not significantly different between treatments for either species. These results suggest that incubation mate feeding can increase female nest attentiveness and perhaps enhance fitness of both males and females. In House Wrens, potential tradeoffs between the benefits of parental care and opportunities to obtain additional mates may explain why males rarely feed incubating females.

Effects of introduced largemouth bass (Micropterus salmoides) on the behavior and persistence of native prey: implications for conservation of the endangered Topeka shiner (Notropis topeka) - Knight, G.L. (Kansas State University, 2004)

Effects of prescribed burning and grazingon breeding bird abundances in tallgrass prairie - Powell, A.F.L.A. (University of Kansas, 2004)

Empirical comparison of Landsat 7 and IKONOS multispectral measurements for selected Earth Observation System (EOS) validation sites - Goward, S.N.; Davis, P.E.; Fleming, D.; Miller, L.; Townshend, J.R. (Remote Sensing of Environment, 2004)
The Space Imaging IKONOS observatory may provide an important benefit in terrestrial scientific research. The five-band, 1 m panchromatic and 4 m multispectral measurements have the potential to provide a source of measurements to evaluate subpixel land cover variability in measurements from observatories such as Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Terra MODIS sensor. The IKONOS observations are at a spatial scale equivalent to field measurements typically carried out in ecological and land cover research. As such, the IKONOS observations may serve as a source of “virtual” ground measurements, for the lower spatial resolution, global observatories. In this study we examine how well IKONOS sensor observations replicate Landsat 7 ETM+ visible/near infrared observations for selected Earth Observation System (EOS) validation sites in the United States. The sites examined—Beltsville, MD, Konza Prairie, KS, and Sevilleta, NM—sample the east–west moisture gradient across the United States. Observations for each site were acquired, as nearly time-coincident as possible, from ETM+ and the IKONOS sensor, several times over the growing season. This was done to insure that we compared these two sensors over the widest range of observing conditions possible. We also examined IKONOS imagery from Phoenix, AZ, where Space Imaging had and had not applied a modulation transfer function compensation (MTFC) process. The MTFC is their standard product. We found that this product, at the original 4 m spatial resolution, appears to have minor radiometric artifacts as a result of the process. When the IKONOS observations were aggregated to 30 m, this problem was essentially absent, allowing us to proceed with the remainder of our study. We processed the IKONOS sensor and ETM+ measurements to produce close approximates of each other. Our processing steps included ortho-rectification, calibration to planetary reflectance, pixel alignment and pixel aggregation. We initially found radiometric differences between the two sensors that increased with increasing wavelength. Space Imaging updated their calibration information, based on analyses from NASA Stennis Space Center staff, which removed much of this discrepancy. We now find that the IKONOS red and near infrared measurements differ between the two sensors, with IKONOS generally producing higher reflectance in the red band and lower reflectance in the near infrared band than the Landsat 7 ETM+ sensor. This results in the IKONOS sensor producing lower spectral vegetation index measurements, for the same target, than ETM+, a measurement variation that has been observed between other sensors. We also encountered far more cirrus cloud (and shadow) contamination in these paired observations that we had expected. After careful initial selection, we lost over half of our image pairs from the analysis because of cirrus cloud contamination. We do not know whether this is simply because of the paired, comparative design of this study or whether it relates to the increased spatial and radiometric resolution of the IKONOS sensor. The results of this study not only provide a baseline assessment of IKONOS versus Landsat 7 ETM+ visible and near infrared measurements but also suggest some of the issues that need more attention when comparing other sensor systems as well as developing the design of future land observatories.
Keywords: ETM+; IKONOS; Landsat 7

Fast ground-water mixing and basal recharge in an unconfined, alluvial aquifer, Konza LTER Site, Northeastern Kansas - G. L. Macpherson; Sophocleous, M. (Journal of Hydrology, 2004)
Ground-water chemistry and water levels at three levels in a well nest were monitored biweekly for two and a half years in a shallow unconfined floodplain aquifer in order to study the dynamics of such shallow aquifers. The aquifer, in northeastern Kansas, consists of high porosity, low hydraulic conductivity fine-grained sediments dominated by silt and bounded by fractured limestone and shale bedrock. Results show that the aquifer underwent chemical stratification followed by homogenization three times during the study period. The length of time between maximum stratification and complete homogenization was 3–5 months. The chemical parameters most useful for demonstrating the mixing trends were dissolved nitrate and sulfate. Higher nitrate concentrations were typical of unsaturated zone water and were sourced from fertilizer applied to the cultivated fields on the floodplain. Variations in sulfate concentrations are attributed to dissolution of rare gypsum in limestone bedrock and variable evapoconcentration in the unsaturated zone. The mixing of three chemically different waters (entrained, unsaturated-zone water; water entering the base of the floodplain aquifer; and water in residence before each mixing event) was simulated. The resident water component for each mixing event was a fixed composition based on measured water chemistry in the intermediate part of the aquifer. The entrained water composition was calculated using a measured composition of the shallow part of the aquifer and measurements of soil-water content in the unsaturated zone. The incoming basal water composition and the fractions of each mixing component were fitted to match the measured chemistry at the three levels in the aquifer. A conceptual model for this site explains: (1) rapid water-level rises, (2) water-chemistry changes at all levels in the aquifer coincident with the water-level rises, (3) low measured hydraulic conductivity of the valley fill and apparent lack of preferential flow pathways, (4) minuscule amounts of unsaturated-zone recharge, and (5) dissolved oxygen peaks in the saturated zone lagging water-level peaks. We postulate that rainfall enters fractures in bedrock adjacent to the floodplain. This recharge water moves rapidly through the fractured bedrock into the base of the floodplain aquifer. The recharge event through the bedrock causes a rapid rise in water level in the floodplain aquifer, and the chemistry of the deepest water in the floodplain aquifer changes at that time. The rising water also entrains slow-moving, nitrate-rich, unsaturated-zone water, altering the chemistry of water in the shallow part of the aquifer. Vertical chemical stratification in the aquifer is thus created by the change in water chemistry in the upper and lower parts of the saturated zone. As the water level begins to decline, the aquifer undergoes mixing that eventually results in homogeneous water chemistry. The rise in water level from the recharge event also displaces gas from the unsaturated zone that is then replaced as the water level declines following the recharge event. This new, oxygen-rich vadose-zone air equilibrates rapidly with saturated-zone water, resulting in a dissolved oxygen pulse in the ground water that peaks one-half to 2 months after the water-level peak. This oxygen pulse subsequently declines over a period of 2–6 months.
Keywords: Chemical stratification; Dissolved oxygen; Floodplain aquifer; Ground-water recharge; Loess; Soil-water modeling

Field vs. lab pH in remote wells, Konza Prairie LTER site, and implications for limestone weathering - G. L. Macpherson (A. A. Balkema Publishers, New York, 2004)

Fire effects on mycorrhizal symbiosis and root system architecture in southern African savanna grasses - D.C. Hartnett; Potgieter, A.L.F.; G.T. Wilson (African Journal of Ecology, 2004)
Mycorrhizal symbiosis is a key factor influencing aspects of grassland and savanna structure and functioning including plant growth, competition, population and community dynamics, and responses to fire and herbivory. This study assessed the effects of fire on mycorrhizal symbiosis and root system architecture (RSA) in South African savanna grasses. Eighteen grass species were sampled across contrasting fire frequency treatments in the Kruger National Park experimental burn plots. All eighteen species studied were highly colonized by arbuscular mycorrhizal fungi (AMF). Both mycorrhizal symbiosis and RSA were strongly affected by fire, with an increase in AMF colonization and a decrease in root branching and fine root development with decreasing fire frequency. Greater water limitation in frequently burned savanna may result in greater fine root development, thus reducing plant dependency on AMF for acquisition of soil resources. Reduced mycorrhizal colonization in frequently burned savanna may also be driven by higher phosphorus : nitrogen ratios, or indirect effects related to higher grazing intensities in frequently burned sites.
Keywords: fire; Grasses; mycorrhizas; root architecture; Savannas

Generality in ecology: testing North American grassland rules in South African savannas - Alan K. Knapp; M.D. Smith; Scott. L. Collins; Zambatis, N.; Peel, M.; Emery, S.M.; Wojdak, J.; Horner-Devine, M.C.; Biggs, H.; Kruger, J.; Andelman, S.J. (Frontiers in Ecology and the Environment, 2004)
Ecology has emerged as a global science, and there is a pressing need to identify ecological rules – general principles that will improve its predictive capability for scientists and its usefulness for managers and policy makers. Ideally, the generality and limits of these ecological rules should be assessed using extensive, coordinated experiments that ensure consistency in design and comparability of data. To improve the design of these large-scale efforts, existing data should be used to test prospective ecological rules and to identify their limits and contingencies. As an example of this approach, we describe prospective rules for grassland responses to fire and rainfall gradients, identified from long-term studies of North American grasslands and tested with existing data from long-term experiments in South African savanna grasslands. Analyses indicated consistent effects of fire on the abundance of the dominant (grasses) and subdominant (forbs) flora on both continents, but no common response of grass or forb abundance across a rainfall gradient. Such analyses can inform future research designs to refine and more explicitly test ecological rules.

Gibberella konza (Fusarium konzum) sp nov from prairie grasses, a new species in the Gibberella fujikuroi species complex - Zeller, K.A.; Summerell, B.A.; Bullock, S.; Leslie, J.F. (Mycologia, 2004)
The Gibberella fujikuroi species complex (Fusarium section Liseola and allied taxa) is composed of an increasingly large number of morphological, biological and phylogenetic species. Most of the known species in this group have been isolated from agricultural ecosystems or have been described from a small number of isolates. We sampled Fusarium communities from native prairie grasses in Kansas and recovered a large number of isolates that superficially resemble F. anthophilum. We used a combination of morphological, biological and molecular characters to describe a new species, Gibberella konza (Gibberella fujikuroi mating population I [MP-I]), from native prairie grasses in Kansas. Although female fertility for field isolates of this species appears to be low, G. konza is heterothallic, and we developed reliably female fertile mating population tester strains for this species. The F. konzum anamorph is differentiated from F. anthophilum and from other Fusarium species in section Liseola by mating compatibility, morphology, AFLP fingerprint profile and differences in β-tubulin DNA sequence.
Keywords: AFLP; biological species; DNA sequence; Fusarium anthophilum; mating population; β-tubulin

Granivory in the prairie of central North America - Reed, A.W. (Kansas State University, 2004)

Grazing management effects on plant species diversity in tallgrass prairie - Hickman, K.R.; D.C. Hartnett; Cochran, R.C.; Owensby, C.E. (Journal of Range Management, 2004)
A 6-year study was conducted in tallgrass prairie to assess the effects of grazing management (cattle stocking densities and grazing systems) on plant community composition and diversity. Treatments included sites grazed season-long (May to October) at 3 stocking densities (3.8, 2.8, and 1.8 hectares per animal unit), ungrazed control sites, and sites under a late-season rest rotation grazing system at this same range of stocking densities. Plant communities were sampled twice each season using a nearest-point procedure. Native plant species diversity, species richness, and growth form diversity were significantly higher in grazed compared to ungrazed prairie, and diversity was greatest at the highest stocking density. This enhancement of plant species diversity under grazing was not a result of increased frequency of weedy/exotic species. There were no significant effects of grazing system on plant diversity, nor any significant stocking density × grazing system interactions, indicating that animal density is a key management variable influencing plant species diversity and composition in tallgrass prairie and that effects of animal density override effects of grazing systems. Increasing cattle stocking densities decreased the abundance of the dominant perennial tall grasses, and increased abundance of the C4 perennial mid-grasses. The frequency of perennial forbs was relatively stable across grazing treatments. Abundance of annual forbs varied among years and grazing treatments. In half of the years sampled, annual forbs showed the highest frequency under intermediate stocking density. Patterns of responses among plant groups suggest that some species may respond principally to direct effects of grazers and others may respond to indirect effects of grazers on competitive relationships or on the spatial patterns of fuel loads and fires. Thus, this study suggests that large grazer densities, fire, and annual climatic variability interact to influence patterns of plant community composition and diversity in tallgrass prairie. Effects of varying management such as stocking densities and grazing systems on plant species diversity and the relative abundances of different plant growth forms or functional groups may have important consequences for grassland community stability and ecosystem function.
Keywords: Biodiversity; cattle grazing; Flint Hills; grazing systems; plant ecology; range management; stocking rates

Influence of fire, topography, and consumer abundance on seed predation in tallgrass prairie - Reed, A.W.; Kaufman, G.A.; D.W. Kaufman (Canadian Journal of Zoology, 2004)
We assessed seed predation by vertebrates and invertebrates in three fire-frequency treatments (<1 year, 1–4 years, and >4 years since fire) and in three topographic positions (upland, limestone breaks, and lowland) in tallgrass prairie. Two types of seed trays, one for vertebrates and one for invertebrates, were placed in each treatment during each nocturnal and diurnal period. Vertebrates removed significantly more seeds than did invertebrates. Fire frequency and topographic position affected seed removal by both vertebrates and invertebrates. Seed removal by invertebrates was influenced negatively by fire; the greatest seed removal occurred in uplands and lowlands in unburned prairie. Vertebrates removed the most seeds in burned prairie and in lowlands and limestone breaks. Time of day also influenced seed removal by vertebrates, as nocturnal vertebrates (assumed to be rodents) removed more seeds than diurnal vertebrates. Abundance of rodents, however, did not predict accurately seed removal in fire treatments or topographic positions, as rodents removed fewer seeds than expected in prairie that had not been burned in >4 years and in lowlands. This pattern likely was due to the presence of a well-developed plant litter layer in both unburned and lowland habitats, which reduces the likelihood of a rodent locating seeds.

Influence of prey abundance on raptors in tallgrass prairie - Reed, A.W.; Kaufman, G.A.; Rintoul, D.A.; D.W. Kaufman (Prairie Naturalist, 2004)
We examined relationships between winter abundance of diurnal raptors (red-tailed hawk, Buteo jamaicensis; rough-legged hawk, B. lagopus; ferruginous hawk, B. regalis; and northern harrier, Circus cyaneus) and both the abundance of microtine rodents (prairie vole, Microtus ochrogaster; and southern bog lemming, Synaptomys cooperi) and aboveground net primary productivity (ANPP) in tallgrass prairie. We used Christmas Bird Count data for each year during 1975 through 1999 from Manhattan, Kansas to index winter raptor abundance (number of hawks per party hour). Microtine rodent abundance (average number of microtine rodents per trapline in burned and unburned prairie) was estimated by using long-term data gathered from autumn and spring surveys along 14 permanent traplines from autumn 1981 to spring 2000 in tallgrass prairie on the Konza Prairie Biological Station. An estimate of ANPP for each year during 1975 through 1999 was provided by the Konza Prairie Long-Term Ecological Research Program. Winter raptor abundance was related positively to ANPP during the preceding growing season (P = 0.01) and to microtine abundance in the previous spring (P = 0.03). Based on a stepwise regression, 39% of the annual variation in winter raptor counts was explained by ANPP and the log of spring microtine abundance. Overall, our analyses suggested that winter raptor abundance was higher in years with higher than lower prey availability, but that other factors also influenced winter raptor abundance.
Keywords: ANPP; microtine rodents; predator-prey; raptor; tallgrass prairie

Influence of shrub encroachment on aboveground net primary productivity and carbon and nitrogen pools in a mesic grassland - Lett, M.S.; Alan K. Knapp; J. M. Briggs; John M. Blair (Canadian Journal of Botany, 2004)
The clonal shrub Cornus drummondii C.A. Mey. is rapidly increasing in cover and displacing mesic grassland species in the central USA as a consequence of fire suppression. We assessed the impact of C. drummondii on carbon (C) and nitrogen (N) pools and C fluxes in a tallgrass prairie in eastern Kansas, USA, through a comparison of both burned and unburned C. drummondii islands with open grassland areas. Allometric equations relating C. drum mondii foliage and wood biomass to basal stem diameter were developed to estimate aboveground biomass and net primary productivity (ANPP) of C. drummondii. Within C. drummondii islands, ANPP was 496 ± 45 g C·m2·year1, nearly three times that within open grassland (167 ± 13 g C·m2·year1). As a result of greater aboveground biomass, aboveground C and N storage within shrub islands (3270 ± 466 g C·m2, 37.9 ± 5.3 g N·m2) was substantially greater than that within open grassland (241 ± 33 g C·m2, 6.1 ± 0.8 g N·m2). No change in soil organic C or total N to 10-cm depth was evident; however, soil CO2 flux was significantly reduced in C. drummondii islands relative to the open grassland. The storage of C in aboveground biomass of C. drummondii represents a significant short-term increase in C storage relative to open grassland. However, potential alterations in belowground processes must be quantified before the long-term net effect of shrub encroachment on C and N pools within this mesic grassland can be determined.Key words: aboveground biomass, Cornus drummondii, net primary productivity, shrub encroachment, tallgrass prairie.

Interactive effects of burn regime and bison activity on tallgrass prairie vegetation - Trager, M.; G.T. Wilson; D.C. Hartnett (American Midland Naturalist, 2004)

Interfertility of two mating populations in the Gibberella fujikuroi species complex - Leslie, J.F.; Zeller, K.A.; Wohler, M.; Summerell, B.A. (European Journal of Plant Pathology, 2004)
Gibberella fujikuroi and Gibberella intermedia (mating populations ‘C’ and ‘D’ of the G. fujikuroi species complex) can be distinguished by differences in the spectrum of mycotoxins produced, the lack of sexual cross-fertility and diagnostic differences in their DNA sequences. Some isolates from these two biological species, however, can interbreed and complete meiosis to produce viable progeny. Analysis of marker segregation amongst such hybrid progeny can be used to estimate the degree of genomic rearrangement and genetic incompatibility that has accumulated since these sibling species diverged. Recombinant progeny were isolated from crosses of the standard tester strains for these two species and from crosses between these standard testers and a field isolate (KSU X-10626) that was cross-fertile with tester strains of both species. Progeny in all of the crosses segregated for amplified fragment length polymorphisms (AFLPs). Segregation of AFLP loci deviated from 1:1 for two thirds of the loci amongst the progeny of the cross between the ‘C’ and ‘D’ mating population tester strains, but <20% of the polymorphic loci in the cross of either tester with KSU X-10626 showed such distortion. It was concluded that G. intermedia and G. fujikuroi are sufficiently interfertile to belong to the same biological species, but that changing the nomenclature to reflect this interfertility requires more evidence for the natural occurrence of a continuum in fertility than is presently available.
Keywords: AFLP; biological species; fumonisin; Fusarium fujikuroi; Fusarium proliferatum; Gibberella intermedia; interspecific hybrids; Konza Prairie; mating type; sexual crosses

Invasion in space and time: non-native species richness and relative abundance respond to interannual variation in productivity and diversity - Cleland, E.E.; M.D. Smith; Andelman, S.J.; Bowles, C.; Carney, K.M.; Horner-Devine, M.C.; Drake, J.M.; Emery, S.M.; Gramling, J.M.; Vandermast, D.B. (Ecology Letters, 2004)
Ecologists have long sought to understand the relationships among species diversity, community productivity and invasion by non-native species. Here, four long-term observational datasets were analyzed using repeated measures statistics to determine how plant species richness and community resource capture (i.e. productivity) influenced invasion. Multiple factors influenced the results, including the metric used to quantify invasion, interannual variation and spatial scale. Native richness was positively correlated with non-native richness, but was usually negatively correlated with non-native abundance, and these patterns were stronger at the larger spatial scale. Logistic regressions indicated that the probability of invasion was reduced both within and following years with high productivity, except at the desert grassland site where high productivity was associated with increased invasion. Our analysis suggests that while non-natives were most likely to establish in species rich communities, their success was diminished by high resource capture by the resident community.

Large ungulates in mesic temperate grassland: Mechanisms on late season aboveground re-growth in Konza tallgrass prairie - Kweka, D. (Wageningen University, 2004)

Life on the edge: the ecology of Great Plains prairie streams - W. K. Dodds; K. B. Gido; M.R. Whiles; Fritz, K.M.; Matthews, W.J. (BioScience, 2004)
Great Plains streams are highly endangered and can serve as model systems for studying disturbance ecology and related issues of resistance and resilience in temperate freshwaters. These streams exist in a precarious balance between flood and drying. In general, microbial activity recovers in days to weeks after drying or flooding, and invertebrate and fish species are quick to follow. In lower forested reaches, floods may be more intense but drying less common. Upstream reaches of prairie streams are characterized by frequent drying, little canopy cover, and limited leaf input. Life history and adaptations alter the ways in which stream organisms respond to these linear patterns. Human modification has altered these patterns, leading to large-scale loss of native grassland streams. The future for Great Plains streams is bleak, given the land-use changes and water-use patterns in the region and the large areas required to preserve intact, ecologically functional watersheds.

Life-history and mark-recapture analysis of the regalfritillary (Speyeria idalia Drury) - Deal, I. (Lenoir-Rhyne College, 2004)

Long-distance movements of the deer mouse in tallgrass prairie - Rehmeier, R.L.; Kaufman, G.A.; D.W. Kaufman (Journal of Mammalogy, 2004)
Long-distance movements may play an important role in regulating populations of small mammals. To examine such movements, we livetrapped 1,712 deer mice (Peromyscus maniculatus) on 14–28 permanent traplines from autumn 1981 to spring 1990 on the Konza Prairie Biological Station, Kansas. These data were collected under a variety of climatic and biotic conditions that resulted in detection of > 100 long-distance movements by deer mice between traplines (moves of 50–1,320 m). Males made more moves than females, but distance moved did not differ by sex. Age did not affect the number or distance of movements. On average, more long-distance moves occurred in spring and summer than in autumn, but distance did not differ by season. Proportion of the population making intertrapline movements was inversely related to abundance of deer mice. Deer mice did not exhibit a fire-positive response in long-distance movement. Our results indicate that deer mice may be more mobile than originally thought. Researchers should incorporate improved methods for detecting longer movements to better understand causes and consequences of these movements.
Keywords: fire; kansas; Movement; Peromyscus maniculatus; prairie deer mouse; relative abundance; season; tallgrass prairie

Microbial community composition across the Great Plains: Landscape versus regional variability - McCulley, R.L.; Burke, I.C. (Soil Science Society of America Journal, 2004)
Rates of nutrient cycling vary across landscape and regional scales. This biogeochemical variability can be partially attributed to patterns in plant community characteristics and abiotic and edaphic conditions across topographic gradients at the landscape-scale or across regional climatic gradients. However, it is also possible that concomitant changes in the microbial communities performing these biogeochemical processes occur across the same spatial scales and may therefore contribute to the observed biogeochemical trends. To assess patterns of microbial community composition across regional and landscape scales, we sampled upland and lowland topographic positions at three grassland communities spanning a 500-mm regional precipitation gradient across the central Great Plains. Soil microbial community composition and biomass were determined using phospholipid fatty acid (PLFA) analysis. Microbial biomass increased across the regional gradient, and different microbial communities were associated with the different grassland community types. The relative abundance of fungi decreased while gram-negative anaerobic bacteria increased from shortgrass steppe to tallgrass prairie. There were no differences in microbial biomass at the landscape-scale, and the only alteration in microbial community composition between upland and lowland landscape positions was a shift toward more nonspecific bacteria in lowlands. The fact that the trends in microbial biomass and community composition at the landscape-scale were less pronounced suggests that variability in microbial community composition is larger regionally across the Great Plains than landscape variability associated with topographical features at any particular site. Alterations in the microbial community may play a role in determining the biogeochemical patterns of grasslands in the Great Plains region.

Needed: A unified infrastructure to support long-term scientific research on public lands - Pringle, C.M.; Scott. L. Collins (Ecological Applications, 2004)

Plant community responses to resource availability and heterogeneity during restoration - S.G. Baer; John M. Blair; Scott. L. Collins; Alan K. Knapp (Oecologia, 2004)
Availability and heterogeneity of resources have a strong influence on plant community structure in undisturbed systems, as well as those recovering from disturbance. Less is known about the role of resource availability and heterogeneity in restored communities, although restoration provides a valuable opportunity to test our understanding of factors that influence plant community assembly. We altered soil nitrogen (N) availability and soil depth during a prairie restoration to determine if the availability and/or heterogeneity of soil resources influenced plant community composition in restored grassland communities. Plant community responses to three levels of N availability (ambient, enriched by fertilization, and reduced by carbon amendment) and two levels of soil depth (deep and shallow) were evaluated. In addition, we evaluated plant community responses to four whole plot heterogeneity treatments created from the six possible combinations of soil N availability and soil depth. The soil depth treatment had little influence on community structure during the first 3 years of restoration. Total diversity and richness declined over time under annual N enrichment, whereas diversity was maintained and richness increased over time in soil with reduced N availability. Non-native species establishment was lowest in reduced-N soil in the initial year, but their presence was negligible in all of the soil N treatments by the second year of restoration. Panicum virgatum, a native perennial C4 grass, was the dominant species in all soil N treatments by year three, but the magnitude of its dominance was lowest in the reduced-N soil and highest in enriched-N soil. Consequently, the relative cover of P. virgatum was strongly correlated with community dominance and inversely related to diversity. The differential growth response of P. virgatum to soil N availability led to a higher degree of community similarity to native prairie in the reduced-N treatment than in the enriched-N treatment. There were no differences in plant community structure among the four whole plot-level heterogeneity treatments, which all exhibited the same degree of similarity to native prairie. Diversity and community heterogeneity in the whole-plot treatments appeared to be regulated by the dominant species’ effect on light availability, rather than soil N heterogeneity per se. Our results indicate that a strong differential response of a dominant species to resource availability in a restored community can regulate community structure, diversity, and similarity to the native (or target) community, but the importance of resource heterogeneity in restoring diversity may be dampened in systems where a dominant species can successfully establish across a range of resource availability.
Keywords: diversity; grassland; nitrogen; tallgrass prairie

Predation by gray catbird on brown thrasher eggs - Rivers, J.W.; Sandercock, B.K. (Southwestern Naturalist, 2004)
The gray catbird (Dumetella carolinensis) has been documented visiting and breaking the eggs of artificial nests, but the implications of such observations are unclear because there is little cost in depredating an undefended nest. During the summer of 2001 at Konza Prairie Biological Station, Kansas, we videotaped a gray catbird that broke and consumed at least 1 egg in a brown thrasher (Toxostoma rufum) nest. Our observation was consistent with egg predation because the catbird consumed the contents of the damaged egg after breaking it. The large difference in body mass suggests that a catbird (37 g) destroying eggs in a thrasher (69 g) nest might risk injury if caught in the act of predation and might explain why egg predation by catbirds has been poorly documented. Our observation indicated that the catbird should be considered as an egg predator of natural nests and that single-egg predation of songbird nests should not be attributed to egg removal by female brown-headed cowbirds (Molothrus ater) without additional evidence.

Quality and quantity of suspended particles in rivers: Continent-scale patterns in the United States - W. K. Dodds; K. B. Gido; M.R. Whiles; Fritz, K.M.; Matthews, W.J. (Environmental Management, 2004)
Suspended solids or sediments can be pollutants in rivers, but they are also an important component of lotic food webs. Suspended sediment data for rivers were obtained from a United States–wide water quality database for 622 stations. Data for particulate nitrogen, suspended carbon, discharge, watershed area, land use, and population were also used. Stations were classified by United States Environmental Protection Agency ecoregions to assess relationships between terrestrial habitats and the quality and quantity of total suspended solids (TSS). Results indicate that nephelometric determinations of mean turbidity can be used to estimate mean suspended sediment values to within an order of magnitude (r2 = 0.89). Water quality is often considered impaired above 80 mg TSS L−1, and 35% of the stations examined during this study had mean values exceeding this level. Forested systems had substantially lower TSS and somewhat higher carbon-to-nitrogen ratios of suspended materials. The correlation between TSS and discharge was moderately well described by an exponential relationship, with the power of the exponent indicating potential acute sediment events in rivers. Mean sediment values and power of the exponent varied significantly with ecoregion, but TSS values were also influenced by land use practices and geomorphological characteristics. Results confirm that, based on current water quality standards, excessive suspended solids impair numerous rivers in the United States.
Keywords: Ecoregions; Land use; pollution; Seston; Suspended sediment; Turbidity; water quality

Resistance and resilience of macroinvertebrate assemblages to drying and flood in a tallgrass prairie stream system - Fritz, K.M.; W. K. Dodds (Hydrobiologia, 2004)
Intermittent streams are common worldwide, and the ability of invertebrates to recover from floods and drought is a key feature of communities from these highly disturbed ecosystems. The macroinvertebrate assemblages of Kings Creek in northeastern Kansas were sampled regularly from four intermittent and two perennial sites over 2 years (1995–1996) to investigate the response and recovery to seasonal drying and floods. A ≈9mo drying period reduced taxa richness and density to 14% and 3% of pre-drying assemblages, respectively, in 1995–1996, whereas a 2mo drying period reduced richness by half and density to 4% of pre-drying assemblages in 1996. Floods at intermittent sites reduced densities and richness by 95% and ≈50%, respectively. A >50 y-flood reduced macroinvertebrate richness by 97% and density by >99% at a downstream perennial site. Resistance and resilience of total macroinvertebrate density was typically greater to floods than to drying, whereas resilience of taxa richness did not differ between disturbance types. The time required for recovery to pre-flood conditions (richness and density) was half as long (27 vs. 76 day) for intermittent sites compared to perennial sites. Colonization of intermittent sites was a function of distance from upstream refugia. Floods were a more important disturbance on assemblages in a downstream reach as compared to upstream reaches. In contrast, upstream reaches were more likely to dry. Recovery following flood and drought was dominated by colonization as opposed to tolerance, thus resilience is more important than resistance in regulating macroinvertebrate communities in these streams, and relative position in the landscape affects disturbance type, intensity, and ability of communities to recover from disturbance.
Keywords: disturbance; drying; floods; intermittent streams; macroinvertebrates; prairie streams

Scale dependence in the relationship between species richness and productivity: the role of spatial and temporal turnover - Chalcraft, D.R.; Williams, J.W.; M.D. Smith; M.R. Whiles (Ecology, 2004)
Recent research in aquatic systems suggests that productivity–richness relationships change with spatial scale and that species turnover (i.e., spatial and temporal variation in species composition) plays an important role in generating this scale dependence. The generality of such scale dependence and the effects of variation in temporal scale remain unknown. We examined the extent to which the richness–productivity relationship in terrestrial plant communities depends on spatial or temporal scale and evaluated how spatial and temporal turnover (i.e., species turnover in space and time) generates scale dependence in these relationships using data from two Long-Term Ecological Research (LTER) sites (Jornada and Konza). We found a weak hump-shaped relationship (Jornada) and no relationship (Konza) between richness and productivity at the smallest focal scale (1 m2 at Jornada and 50 m2 at Konza) at each site, but strong hump-shaped relationships at the largest focal scale (49 m2 at Jornada and 200 m2 at Konza) for each site. Relationships between spatial turnover and productivity at each site mirrored the productivity–richness relationships that emerged at the larger spatial scale (i.e., a significant hump-shaped pattern). In contrast, temporal turnover was unrelated to productivity, and hence increasing temporal scale did not appreciably change the form of the productivity–richness relationship. Our study suggests that the way in which productivity–richness relationships change with spatial or temporal scale depends on the form and strength of the underlying relationship between species turnover and productivity. Moreover, we contend that a dominant effect of increasing productivity is the generation of dissimilarity in species composition among localities that comprise a region, rather than increasing the number of species that occur within local communities. Thus, understanding the mechanisms that cause species turnover to vary with productivity is critical to understanding scale dependence in richness–productivity relationships.

Seasonal and temporal variation of arbuscular mycorrhizal and dark septate endophytic fungi in a tallgrass prairie ecosystem - Mandyam, K.G. (Kansas State University, 2004)

Seasonal, topographic and burn frequency effects on biophysical/spectral reflectance relationships in tallgrass prairie - Goodin, D.G.; Gao, J.; Hutchinson, J.M.S. (Int. J. Remote Sensing, 2004)
Application of remote sensing relies on understanding how the physical properties of surfaces (especially vegetated surfaces) control spectral reflectance. Empirical investigation of links between canopy properties/processes and spectral response have generally consisted of univariate modelling of one spectral response variable in terms of one canopy property, or less frequently, in terms of two or more canopy variables. While this approach has been fruitful, it cannot account for multivariate interactions of spectral and surface properties in determining canopy response across the spectrum. In this study, two closely related multivariate analysis techniques, canonical correlation and redundancy analysis, are used to investigate the relationship between a series of tallgrass prairie canopy biophysical properties and spectral reflectance measured in situ using a portable radiometer. To capture a variety of different conditions within the tallgrass canopy, data were collected at two times during the 2002 growing season (28 May and 18 August), from two different slope/aspect situations, located on one frequently burned and one infrequently burned watershed. Results suggest that canopy structure (canopy height, greenness fraction) is the most consistent influence on spectral reflectance during both data collection periods. Canopy optical properties also emerge as an important control in August. Neither soil moisture nor plant physiology/biochemistry systematically influenced spectral reflectance. The relative importance of the various canopy variables shows some dependence on burn frequency and topographic setting.

Species diversity of and toxin production by Gibberella fujikuroi species complex strains isolated from native prairie grasses in Kansas - Leslie, J.F.; Zeller, K.A.; Logrieco, A.; Mule, G.; Moretti, A.; Ritieni, A. (Applied and Environmental Microbiology, 2004)
Fusarium species from agricultural crops have been well studied with respect to toxin production and genetic diversity, while similar studies of communities from nonagricultural plants are much more limited. We examined 72 Fusarium isolates from a native North American tallgrass prairie and found that Gibberella intermedia (Fusarium proliferatum), Gibberella moniliformis (Fusarium verticillioides), and Gibberella konza (Fusarium konzum) dominated. Gibberella thapsina (Fusarium thapsinum) and Gibberella subglutinans (Fusarium subglutinans) also were recovered, as were seven isolates that could not be assigned to any previously described species on the basis of either morphological or molecular characters. In general, isolates from the prairie grasses produced the same toxins in quantities similar to those produced by isolates of the same species recovered from agricultural hosts. The G. konza isolates produce little or no fumonisins (up to 120 μg/g by one strain), and variable but generally low to moderate amounts of beauvericin (4 to 320 μg/g) and fusaproliferin (50 to 540 μg/g). Toxicity to Artemia salina larvae within most species was correlated with the concentration of either beauvericin or fusaproliferin produced. Organic isolates from some cultures of G. moniliformis were highly toxic towards A. salina even though they produced little, if any, beauvericin or fusaproliferin. Thus, additional potentially toxigenic compounds may be synthesized by G. moniliformis strains isolated from prairie grasses. The Fusarium community from these grasses appears to contain some species not found in surrounding agricultural communities, including some that probably are undescribed, and could be capable of serving as a reservoir for strains of potential agricultural importance.

A technique for establishing reference nutrient concentrations across watersheds impacted by humans - W. K. Dodds; Oakes, R. (Limnology and Oceanography Methods, 2004)
Establishing reference nutrient conditions for rivers and streams is necessary to assess human impact on aquatic ecosystems and protect water quality and biotic integrity. Several methods have been proposed: (1) percentiles from statistical distributions of all rivers and streams in a region or dataset, (2) reference stream approaches, and (3) modeling river networks from existing reference streams. We propose an additional statistical method to estimate the influence of anthropogenic land uses on lotic nutrient concentrations. First, we quantify regional variation by using analysis of covariance, where total nitrogen or total phosphorus is the dependent variable, region is the categorical predictor, and percentage of anthropogenic land use (e.g., cropland, urban land) is the covariate. This allows for the aggregation of regions if there is not a significant regional effect, or if there is a significant regional effect, identifies the need to analyze regions separately. Second, we develop multiple linear regression models with best-model techniques in which anthropogenic land-use classifications are the independent variables, and the logarithms of in-stream nutrient concentrations are the dependent variables. The intercept of these regression models (i.e., expected nutrient concentration in the absence of human activities assuming linear extrapolation to the origin) represents the reference nutrient concentrations. This analysis suggests that larger percentages of cropland and urban land have strong positive influences on in-stream nutrient concentrations, both in eastern Kansas and across the conterminous United States. The most appropriate method for regions may depend on the relative availability of reference sites and other data sources. The covariance/reference approach offers a potential method for regions with limited numbers of reference sites.

Variability in grasshopper densities in response to fire frequency and bison grazing from tallgrass prairie - Anthony Joern (Environmental Entomology, 2004)
While weather can contribute significantly to grasshopper population dynamics in North American grasslands, local environmental conditions resulting from land use practices may be equally important. In this study, significant differences in grasshopper density were detected among adjacent watersheds from Kansas Flint Hills tallgrass prairie that differed in fire frequency and especially bison grazing treatments. Grasshopper densities were ≈2.5 times greater in grazed watersheds compared with ungrazed ones. Grasshopper densities also varied somewhat in response to fire frequency, mostly in species-specific ways. No treatment interactions on overall grasshopper density were detected. The effects of fire frequency and bison grazing were implemented in part through their combined effect on the structural heterogeneity of vegetation, and other habitat characteristics. Individual grasshopper species responded uniquely to combinations of fire frequency and bison grazing. Grazing resulted in significant increases in density for seven of the nine most abundant species; fire frequency affected two species; and one species did not respond to either fire or grazing. Understanding effects of habitat on grasshopper densities provides opportunities to manage these populations for economic or conservation needs.
Keywords: Bison grazing; Konza Prairie; Orthoptera; population dynamics; prescribed burning

Vegetation-mediated changes in microclimate reduce soil respiration as woodlands expand into grasslands - Smith, D.L.; Johnson, L.C. (Ecology, 2004)
This study compared annual and growing-season in situ soil respiration and soil C cycling in paired juniper woodland and C4-dominated grassland sites in eastern Kansas (USA) to determine if, under similar edaphic and regional climate conditions, vegetation change alters soil CO2 dynamics. We found marked differences in soil respiration related to vegetation: Growing season mean woodland soil respiration rates (4.6 μmoles·m−2·s−1) averaged 38% less than paired grassland sites. Soil moisture did not explain the difference in soil respiration between woodlands and grasslands. Soil temperatures at the 10-cm depth were 5°C cooler in woodlands during the growing season and significantly different between woodlands and grasslands throughout the year, explaining most of the low soil respiration in woodlands. However, there were subtle intrinsic differences in the response of soil respiration to temperature between woodlands and grasslands: Woodland and grassland respiration response was significantly different at the P = 0.05 level, also indicated by a grassland Q10 of 2.4 compared to 2.2 in woodlands. We found no significant differences between woodlands and grasslands in long-term (82-week) laboratory incubations of potentially mineralizable soil C and short-term incubations for microbial biomass C. Similarly, root biomass did not differ between woodlands and grasslands and could not explain the lower in situ woodland soil respiration. Thus, vegetation-mediated reduction in soil temperature under the canopy explained much of the lower in situ woodland soil respiration. Lower soil respiration in the woodland resulted in an annual flux of 533.6 (±21.7) compared to 858.4 (±14.5) g C·m−2·yr−1 in grasslands, nearly 38% lower in the woodland (means ± 1 se). Assuming root respiration is 50% of soil respiration, we estimate that the turnover of woodland soil C stocks may be slowed by 15 years relative to grassland. This suggests that, if juniper expansion (now occurring across nearly 5 million hectares in the Great Plains) proceeds to canopy closure, annual soil C flux may be potentially reduced by as much as 19 × 106 Mg of C below C flux rates that occurred historically from tallgrass prairie soils.

Water relations in grassland and desert ecosystems exposed to elevated atmospheric CO2 - Morgan, J.A.; Pataki, D.E.; Korner, C.; Clark, H.; Del Grosso, S.J.; Grunzweig, J.M.; Alan K. Knapp; Mosier, A.R.; Newton, P.C.D.; Niklaus, P.A.; Jesse B. Nippert; Nowak, R.S.; et al. (Oecologia, 2004)
Atmospheric CO2 enrichment may stimulate plant growth directly through (1) enhanced photosynthesis or indirectly, through (2) reduced plant water consumption and hence slower soil moisture depletion, or the combination of both. Herein we describe gas exchange, plant biomass and species responses of five native or semi-native temperate and Mediterranean grasslands and three semi-arid systems to CO2 enrichment, with an emphasis on water relations. Increasing CO2 led to decreased leaf conductance for water vapor, improved plant water status, altered seasonal evapotranspiration dynamics, and in most cases, periodic increases in soil water content. The extent, timing and duration of these responses varied among ecosystems, species and years. Across the grasslands of the Kansas tallgrass prairie, Colorado shortgrass steppe and Swiss calcareous grassland, increases in aboveground biomass from CO2 enrichment were relatively greater in dry years. In contrast, CO2-induced aboveground biomass increases in the Texas C3/C4 grassland and the New Zealand pasture seemed little or only marginally influenced by yearly variation in soil water, while plant growth in the Mojave Desert was stimulated by CO2 in a relatively wet year. Mediterranean grasslands sometimes failed to respond to CO2-related increased late-season water, whereas semiarid Negev grassland assemblages profited. Vegetative and reproductive responses to CO2 were highly varied among species and ecosystems, and did not generally follow any predictable pattern in regard to functional groups. Results suggest that the indirect effects of CO2 on plant and soil water relations may contribute substantially to experimentally induced CO2-effects, and also reflect local humidity conditions. For landscape scale predictions, this analysis calls for a clear distinction between biomass responses due to direct CO2 effects on photosynthesis and those indirect CO2 effects via soil moisture as documented here.
Keywords: biomass; Carbon dioxide enrichment; Landscape predictions; soil water; Stomata

Abiotic constraints on the establishment of Quercus seedlings in grasslands - Danner, B.T.; Alan K. Knapp (Global Change Biology, 2003)
High evaporative demand and periodic drought characterize the growing season in midwestern grasslands relative to deciduous forests of the eastern US, and predicted climatic changes suggest that these climatic extremes may be exacerbated. Despite this less than optimal environment for tree seedling establishment, deciduous trees have expanded into adjacent tallgrass prairie within the last century leading to a dramatic land cover change. In order to determine the role of light and temperature on seedling establishment, we assessed carbon and water relations and aboveground growth of first-year Quercus macrocarpa seedlings exposed to one of three conditions: (1) intact tallgrass prairie communities (control), (2) aboveground herbaceous biomass removed (grass removal), and (3) shade plus biomass removal to reduce light (PFD) to levels typical of the grassland-forest ecotone (shade). In the 2000 growing season, precipitation was 35% below the long-term average, which had a significant negative effect on oak seedling carbon gain at midseason (photosynthesis declined to 10% of maximum rates). However, net photosynthesis and stomatal conductance in the shade treatment was ca. 2.5 and 1.5 times greater, respectively, than in control treatment seedlings during this drought. During this period, leaf and air temperatures in control seedlings were similar whereas leaf temperatures in the shade treatment remained below air temperature. A late-season recovery period, coincident with decreased air temperatures, resulted in increased net photosynthesis for all seedlings. Increased photosynthetic rates and water relations in shaded seedlings compared to seedlings in full sun suggest that, at least in dry years, high light and temperature may negatively impact oak seedling performance. However, high survival rates for all seedlings indicate that Q. macrocarpa seedlings are capable of tolerating both present-day and future climatic extremes. Unless historic fire regimes are restored, forest expansion and land cover change are likely to continue.