Assessing the response of terrestrial ecosystems to potential changes in precipitation - Weltzin, J.F.; Loik, M.E.; Schwinning, S.; Williams, D.G.; Fay, P.A.; Haddad, B.; Harte, J.; Huxman, T.E.; Alan K. Knapp; Lin, G.; Pockman, W.T.; Shaw, M.R.; et al. (BioScience, 2003)
Changes in Earth's surface temperatures caused by anthropogenic emissions of greenhouse gases are expected to affect global and regional precipitation regimes. Interactions between changing precipitation regimes and other aspects of global change are likely to affect natural and managed terrestrial ecosystems as well as human society. Although much recent research has focused on assessing the responses of terrestrial ecosystems to rising carbon dioxide or temperature, relatively little research has focused on understanding how ecosystems respond to changes in precipitation regimes. Here we review predicted changes in global and regional precipitation regimes, outline the consequences of precipitation change for natural ecosystems and human activities, and discuss approaches to improving understanding of ecosystem responses to changing precipitation. Further, we introduce the Precipitation and Ecosystem Change Research Network (PrecipNet), a new interdisciplinary research network assembled to encourage and foster communication and collaboration across research groups with common interests in the impacts of global change on precipitation regimes, ecosystem structure and function, and the human enterprise.
Keywords: Community; ecosystem; global change; Precipitation; soil moisture

Butterflies (Lepidoptera) of Konza Prairie Biological Station: An annotated checklist - Wright, V.F.; Huber, R.L.; Huber, C.L. (Journal of the Kansas Entomological Society, 2003)
Konza Prairie Biological Station is a native tallgrass prairie preserve in Riley and deary Counties. Kansas, where seventy-eight species of butterflies (Lepidoptera) were collected or sighted from 1997 through 1999. Basedon known larva] hosts, 65% were from prairie or open field habitats with 24% grass feeders, 25% from woodland or woodland borders and approximately 10% from mixed or unknown habitats. There were 1I new records for Riley County: Northern Cloudy Wing, Thorybes pylades (Scudder) (Hesperiidae), Funeral Dusky Wing, Erynnis funeralis (Scudder & Burgess) (Hesperiidae), Little Glassywing, Pompeius verna (W. Edwards) (Hesperiidae), Byssus Skipper, Problema byssus kumskaka (Scudder) (Hesperiidae), Hobomok Skipper, Poanes hobomok (T. Harris) (Hesperiidae), Dusted Skipper, Atrytonopsis hianna turneri H. A. Freeman (Hesperiidae), Coral Hairstreak, Harkenclenus titus (Fabricius) (Lycaenidae), Banded Hairstreak, Satyrium calanus falacer (Godart) (Lycaenidae) and Hickory Hairstreak, Satyrium caryaevorum (McDunnough) (Lycaenidae), Summer Azure, Celastrina neglecta (W. Edwards) (Lycaenidae) and Northern Pearly Eye. Enodia anthedon A. H. Clark (Satyridae). The larvae of Reakirt's Blue, Hemiargus isola ah-e (W. Edwards) (Lycaenidae) were found feeding on the flowers of Catclaw Sensitive Briar, Shrankia nuttallii (DC.) Standl. (Mimosaceae), a new host record A checklist is given for species found during the survey period and those whose host, habitat or distribution make it likely they may be found on Konza Prairie in the future.
Keywords: Butterfly survey; host record; Kansas county records; Species richness; tallgrass prairie

C3 shrub expansion in a C4 grassland: positive post-fire responses in resources and shoot growth - McCarron, J.K.; Alan K. Knapp (American Journal of Botany, 2003)
Changes in land management and reductions in fire frequency have enabled woody species to increase in grasslands worldwide. Nevertheless, fire is rarely eliminated from grasslands, and for shrubs to survive, they must be able cope with fire and replace aboveground structures. Because new shoots may have more available solar radiation, greater root : shoot ratios, and thus more resources available belowground after fire compared to undisturbed shrub communities, we hypothesized that carbon, nutrient, and water relations may be enhanced in stems compared to those in an undisturbed grassland. However, this same post-fire resource pulse stimulates the grasses and may intensify competitive interactions between shrubs and grasses. To test these predictions, we measured seasonal patterns in net photosynthesis (A), predawn xylem pressure potentials (XPP), leaf nitrogen (N) content, and productivity of Cornus drummondii shoots from shrub patches (islands) of different sizes in mesic grasslands burned annually, burned infrequently, and protected from fire. Seasonal average A was 20% higher (P = 0.016) in burned than in unburned shrubs, regardless of island size. Shrubs in burned sites also produced shoots with higher leaf N than unburned shrubs, and N content was higher in leaves from small islands compared to large islands (P < 0.0001). Burning caused a decrease in late summer predawn XPP in small islands (−3.1 MPa), whereas burned large islands did not differ from unburned shrubs. Post-fire productivity of new shoots was significantly greater compared to shoots in unburned sites. These results indicate that a transient period of high resource availability after fire allows for increased growth and rapid recovery of grassland shrubs. Thus, although fire has a negative effect on aboveground biomass of shrubs, the post-fire increases in resource availability, which enhance growth in the dominant grasses, are also important for recovery of woody species.
Keywords: C3; C4; Cornus drummondii; fire; shrub; tallgrass prairie; transient maxima hypothesis; woody expansion

Climate variability and ecosystem response at Long-Term Ecological Research sites - Greenland, D.; Goodin, D.G.; Smith, R.C. (Oxford University Press, 2003)

Climate variability in tallgrass prairie at multiple timescales: Konza Prairie Biological Station - Goodin, D.G.; P. Fay; McHugh, M.J. (Climate Variability and Ecosystem Response at Long-Term Ecological Research Sites, 2003)

A comparative assessment of potential mechanisms influencing plant species richness in grazed grasslands - Bakker, C.; John M. Blair; Alan K. Knapp (Oecologia, 2003)
Grazing by large ungulates often increases plant species richness in grasslands of moderate to high productivity. In a mesic North American grassland with and without the presence of bison (Bos bison), a native ungulate grazer, three non-exclusive hypotheses for increased plant species richness in grazed grasslands were evaluated: (1) bison grazing enhances levels of resource (light and N) availability, enabling species that depend on higher resource availability to co-occur; (2) spatial heterogeneity in resource availability is enhanced by bison, enabling coexistence of a greater number of plant species; (3) increased species turnover (i.e. increased species colonization and establishment) in grazed grassland is associated with enhanced plant species richness. We measured availability and spatial heterogeneity in light, water and N, and calculated species turnover from long-term data in grazed and ungrazed sites in a North American tallgrass prairie. Both regression and path analyses were performed to evaluate the potential of the three hypothesized mechanisms to explain observed patterns of plant species richness under field conditions. Experimental grazing by bison increased plant species richness by 25% over an 8-year period. Neither heterogeneity nor absolute levels of soil water or available N were related to patterns of species richness in grazed and ungrazed sites. However, high spatial heterogeneity in light and higher rates of species turnover were both strongly related to increases in plant species richness in grazed areas. This suggests that creation of a mosaic of patches with high and low biomass (the primary determinant of light availability in mesic grasslands) and promotion of a dynamic species pool are the most important mechanisms by which grazers affect species richness in high productivity grasslands.
Keywords: colonization; Grazing; heterogeneity; Species richness; tallgrass prairie

Comparing denitrification estimates for a Texas estuary by using acetylene inhibition and membrane inlet mass spectrometry - Bernot, M.J.; W. K. Dodds; Gardner, W.S.; McCarthy, M.J.; Sobolev, D.; Tank, J.L. (Applied and Environmental Microbiology, 2003)
Characterizing denitrification rates in aquatic ecosystems is essential to understanding how systems may respond to increased nutrient loading. Thus, it is important to ensure the precision and accuracy of the methods employed for measuring denitrification rates. The acetylene (C2H2) inhibition method is a simple technique for estimating denitrification. However, potential problems, such as inhibition of nitrification and incomplete inhibition of nitrous oxide reduction, may influence rate estimates. Recently, membrane inlet mass spectrometry (MIMS) has been used to measure denitrification in aquatic systems. Comparable results were obtained with MIMS and C2H2 inhibition methods when chloramphenicol was added to C2H2 inhibition assay mixtures to inhibit new synthesis of denitrifying enzymes. Dissolved-oxygen profiles indicated that surface layers of sediment cores subjected to the MIMS flowthrough incubation remained oxic whereas cores incubated using the C2H2 inhibition methods did not. Analysis of the microbial assemblages before and after incubations indicated significant changes in the sediment surface populations during the long flowthrough incubation for MIMS analysis but not during the shorter incubation used for the C2H2 inhibition method. However, bacterial community changes were also small in MIMS cores at the oxygen transition zone where denitrification occurs. The C2H2 inhibition method with chloramphenicol addition, conducted over short incubation intervals, provides a cost-effective method for estimating denitrification, and rate estimates are comparable to those obtained by the MIMS method.

Comparisons of land cover and LAI estimates derived from ETM+ and MODIS for four sites in North America: a quality assessment of 2000/2001 provisional MODIS products - Cohen, W.B.; Maiersperger, T.K.; Yang, Z.; Gower, S.T.; Turner, D.P.; Ritts, W.D.; Berterretche, M.; Running, S.W. (Remote Sensing of Environment, 2003)
The MODIS land science team produces a number of standard products, including land cover and leaf area index (LAI). Critical to the success of MODIS and other sensor products is an independent evaluation of product quality. In that context, we describe a study using field data and Landsat ETM+ to map land cover and LAI at four 49-km2 sites in North America containing agricultural cropland (AGRO), prairie grassland (KONZ), boreal needleleaf forest, and temperate mixed forest. The purpose was to: (1) develop accurate maps of land cover, based on the MODIS IGBP (International Geosphere–Biosphere Programme) land cover classification scheme; (2) derive continuous surfaces of LAI that capture the mean and variability of the LAI field measurements; and (3) conduct initial MODIS validation exercises to assess the quality of early (i.e., provisional) MODIS products. ETM+ land cover maps varied in overall accuracy from 81% to 95%. The boreal forest was the most spatially complex, had the greatest number of classes, and the lowest accuracy. The intensive agricultural cropland had the simplest spatial structure, the least number of classes, and the highest overall accuracy. At each site, mapped LAI patterns generally followed patterns of land cover across the site. Predicted versus observed LAI indicated a high degree of correspondence between field-based measures and ETM+ predictions of LAI. Direct comparisons of ETM+ land cover maps with Collection 3 MODIS cover maps revealed several important distinctions and similarities. One obvious difference was associated with image/map resolution. ETM+ captured much of the spatial complexity of land cover at the sites. In contrast, the relatively coarse resolution of MODIS did not allow for that level of spatial detail. Over the extent of all sites, the greatest difference was an overprediction by MODIS of evergreen needleleaf forest cover at the boreal forest site, which consisted largely of open shrubland, woody savanna, and savanna. At the agricultural, temperate mixed forest, and prairie grassland sites, ETM+ and MODIS cover estimates were similar. Collection 3 MODIS-based LAI estimates were considerably higher (up to 4 m2 m−2) than those based on ETM+ LAI at each site. There are numerous probable reasons for this, the most important being the algorithms' sensitivity to MODIS reflectance calibration, its use of a prelaunch AVHRR-based land cover map, and its apparent reliance on mainly red and near-IR reflectance. Samples of Collection 4 LAI products were examined and found to consist of significantly improved LAI predictions for KONZ, and to some extent for AGRO, but not for the other two sites. In this study, we demonstrate that MODIS reflectance data are highly correlated with LAI across three study sites, with relationships increasing in strength from 500 to 1000 m spatial resolution, when shortwave-infrared bands are included.
Keywords: BigFoot; ETM; IGBP; Land cover; Leaf area index; MODIS; Validation

Consequences of shrub expansion in mesic grassland: resource alterations and graminoid responses - Lett, M.S.; Alan K. Knapp (Journal of Vegetation Science, 2003)
In the mesic grasslands of the central United States, the shrub Cornus drummondii has undergone widespread expansion in the absence of recurrent fire. We quantified alterations in light, water and N caused by C. drummondii expansion in tall-grass prairie and assessed the hypothesis that these alterations are consistent with models of resource enrichment by woody plants. Responses in graminoid species, particularly the dominant C4 grass Andropogon gerardii, were concurrently evaluated. We also removed established shrub islands to quantify their legacy effect on resource availability and assess the capability of this grassland to recover in sites formerly dominated by woody plants. The primary effect of shrub expansion on resource availability was an 87% reduction in light available to the herbaceous understorey. This reduced C uptake and N use efficiency in A. gerardii and lowered graminoid cover and ANPP at the grass-shrub ecotone relative to undisturbed grassland. Shrub removal created a pulse in light and N availability, eliciting high C gain in A. gerardii in the first year after removal. By year two, light and N availability within shrub removal areas returned to levels typical of grassland, as had graminoid cover and ANPP were similar to those in open grassland. Recovery within central areas of shrub removal sites lagged behind that at the former grass-shrub ecotone. These results indicate that the apparent alternative stable state of C. drummondii dominance in tall-grass prairie is biotically maintained and driven by reductions in light, rather than resource enrichment. Within areas of shrub removal, the legacy effect of C. drummondii dominance is manifest primarily through the loss of rhizomes of the dominant grasses, rather than any long-term changes in resource availability. C. drummondii removal facilitates grassland recovery, but the effort required to initiate this transition is a significant cost of woody plant expansion in mesic grasslands. Prevention of woody plant expansion in remnant tall-grass prairies is, therefore, a preferred management option.
Keywords: Cornus drummondii; Grassland recovery; land cover change; Tall-grass prairie; Woody plant expansion

A cross-biome comparison of daily light use efficiency for gross primary production - Turner, D.P.; Urbanski, D.; D. Bremer; Wofsy, S.C.; Meyers, T.; Gower, S.T.; Gregory, M. (Global Change Biology, 2003)
Vegetation light use efficiency is a key physiological parameter at the canopy scale, and at the daily time step is a component of remote sensing algorithms for scaling gross primary production (GPP) and net primary production (NPP) over regional to global domains. For the purposes of calibrating and validating the light use efficiency (εg) algorithms, the components of εg– absorbed photosynthetically active radiation (APAR) and ecosystem GPP – must be measured in a variety of environments. Micrometeorological and mass flux measurements at eddy covariance flux towers can be used to estimate APAR and GPP, and the emerging network of flux tower sites offers the opportunity to investigate spatial and temporal patterns in εg at the daily time step. In this study, we examined the relationship of daily GPP to APAR, and relationships of εg to climatic variables, at four micrometeorological flux tower sites – an agricultural field, a tallgrass prairie, a deciduous forest, and a boreal forest. The relationship of GPP to APAR was close to linear at the tallgrass prairie site but more nearly hyperbolic at the other sites. The sites differed in the mean and range of daily εg, with higher values associated with the agricultural field than the boreal forest. εg decreased with increasing APAR at all sites, a function of mid-day saturation of GPP and higher εg under overcast conditions. εg was generally not well correlated with vapor pressure deficit or maximum daily temperature. At the agricultural site, a εg decline towards the end of the growing season was associated with a decrease in foliar nitrogen concentration. At the tallgrass prairie site, a decline in εg in August was associated with soil drought. These results support inclusion of parameters for cloudiness and the phenological status of the vegetation, as well as use of biome-specific parameterization, in operational εg algorithms.
Keywords: Primary production

Disturbance dynamics and ecological response: the contribution of long-term ecological research - Turner, M.G.; Scott. L. Collins; Lugo, A.L.; Magnuson, J.J.; Rupp, T.S.; Swanson, F.J. (BioScience, 2003)
Long-term ecological research is particularly valuable for understanding disturbance dynamics over long time periods and placing those dynamics in a regional context. We highlighted three case studies from Long Term Ecological Research (LTER) Network sites that have contributed to understanding the causes and consequences of disturbance in ecological systems. The LTER Network significantly enhances the ability to study disturbance by (a) encompassing ecosystems subject to a wide range of disturbances, (b) providing a long-term baseline against which to detect change and measure ecosystem responses to disturbance, (c) permitting observation of slow or infrequent events, (d) facilitating the use of multiple research approaches, (e) providing a focus for modeling disturbance dynamics, and (f) contributing to land and resource management. Long-term research is crucial to understanding past, present, and future disturbance dynamics, and the LTER Network is poised to make continuing contributions to the understanding of disturbance.
Keywords: biotic invasion; fire; heterogeneity; hurricane; scale

Dominant species maintain ecosystem function with non-random species loss - M.D. Smith; Alan K. Knapp (Ecology Letters, 2003)
Loss of species caused by widespread stressors, such as drought and fragmentation, is likely to be non-random depending on species abundance in the community. We experimentally reduced the number of rare and uncommon plant species while independently reducing only the abundance of dominant grass species in intact, native grassland. This allowed us to simulate a non-random pattern of species loss, based on species abundances, from communities shaped by natural ecological interactions and characterized by uneven species abundance distributions. Over two growing seasons, total above-ground net primary productivity (ANPP) declined with reductions in abundance of the dominant species but was unaffected by a threefold decline in richness of less common species. In contrast, productivity of the remaining rare and uncommon species decreased with declining richness, in part due to loss of complementary interactions among these species. However, increased production of the dominant grasses offset the negative effects of species loss. We conclude that the dominant species, as controllers of ecosystem function, can provide short-term resistance to reductions in ecosystem function when species loss is nonrandom. However, the concurrent loss of complementary interactions among rare and uncommon species, the most diverse component of communities, may contribute to additional species loss and portends erosion of ecosystem function in the long term.

An ecosystem in transition: Patterns and mechanisms of a shift in growth form dominance in mesic grasslands of central North America - Heisler, J.L. (Arizona State University, 2003)

Ecosystem significance of crayfishes and central stonerollers in a tallgrass prairie stream: Functional differences between co-occurring omnivores - M. Evans-White; W. K. Dodds; M.R. Whiles (Journal of the North American Benthological Society, 2003)
The ecosystem significance of crayfishes (Orconectes nais (Faxon) and O. neglectus (Faxon)) and central stoneroller minnows (Campostoma anomalum (Rafinesque)), was examined in a tallgrass prairie stream by estimating the trophic basis of production and consumption for each species. Annual ash-free dry mass production and production to biomass ratios of C. anomalum (260 mg m−2 y−1, 1.3) were lower than that of O. nais (719 mg m−2 y−1, 2.4) and O. neglectus (508 mg m−2 y−1, 2.1). Gut content analysis revealed no significant differences in the percentages of the various food items ingested by O. nais and O. neglectus, indicating they were functionally similar with respect to the types of organic matter processed in this system. We found a significant difference among seasons in the % of invertebrates in C. anomalum guts (p = 0.0001) and the % of algae in Orconectes spp. guts (p = 0.005), indicating the importance of measuring resource use throughout the growing season. Leaves contributed most to Orconectes spp. annual production (45%) followed by animal matter (30%), algae (19%), and amorphous detritus (6%). Algae contributed most to C. anomalum production (47%) followed by amorphous detritus (30%), animal matter (21%), and leaves (2%). Orconectes spp. consumed more leaf litter, filamentous green algae, and macroinvertebrates than C. anomalum, whereas C. anomalum consumed more diatoms. Crayfish and central stonerollers are both omnivores that function as important consumers and processors of algae and detritus in this tallgrass prairie stream, but each focuses on slightly different types of similar resources.
Keywords: central stonerollers; Growth rate; gut contents; omnivory; Orconectes; secondary production

Effects of burning on snakes in Kansas, USA, tallgrass prairie - Setser, K.; John F. Cavitt II. (Natural Areas Journal, 2003)

Effects of fire, mowing and fertilization effects on density and biomass of macroinvertebrates in North American tallgrass prairie soils - Callaham, M.A. Jr.; John M. Blair; T.C. Todd; Kitchen, D.J.; M.R. Whiles (Soil Biology & Biochemistry, 2003)
The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.
Keywords: biomass; Cicadidae; Curculionidae; disturbance; earthworms; Elateridae; Fertilization; Fertilizer; fire; grassland; insect herbivores; nitrogen; Phosphorus; Scarabaeidae

Effects of shrub encroachment and removal on plant community composition and ecosystem structure and function in a mesic grassland - Lett, M.S. (Kansas State University, 2003)

Effects of spring burning and fungicide application on growth of warm season grasses and their pathogens in a native tallgrass prairie, greenhouse, and monoculture - Morgan, G.W. (Kansas State University, 2003)

An examination of the effects of grazing on vegetative and soil parameters in the tallgrass prairie - Walters, C.M.; Martin, M.C. (Transactions of Kansas Academy of Science, 2003)
The effects of grazing on vegetative biomass and richness and various soil parameters in the tallgrass prairie were examined at the Tallgrass Prairie National Preserve (TPNP) and the Konza Prairie Biological Station (KPBS). It is hypothesized that grazing will exert significant influence on vegetative biomass and native species richness, and soil depth, moisture content, pH, nutrient levels (total Kjeldahl nitrogen and total phosphorus), and organic matter content. To test this hypothesis, four sets of samples were gathered: 10 from an ungrazed portion of TPNP and 10 from a grazed portion, 10 from an ungrazed area of KPBS and 10 from a grazed area. Results indicate that grazing decreased vegetative biomass density, increased soil nutrient levels, and increased soil organic matter content. Mixed results were found on the effects of grazing on available soil moisture and soil pH. Soil moisture content was significantly higher in the ungrazed area of TPNP, but significantly higher in the grazed area at KPBS. Soil pH was significantly higher in the ungrazed area of TPNP but no significant differences were observed at KPBS. Grazing did not significantly influence soil depth or species richness, though differences in the taxa of species observed were evident as native grass species richness decreased in grazed areas and invasive species richness increased in grazed areas.
Keywords: Grazing; kansas; soil; tallgrass prairie; vegetation

Expansion of Juniperus in the Great Plains: Changes in soil organic carbon dynamics - Smith, D.L.; Johnson, L.C. (Global Biogeochemical Cycles, 2003)
[1] Woody encroachment by Juniperus virginiana into Great Plains grasslands allowed us to answer: Does changing the type of plant input to soils alter soil organic carbon (SOC) distribution or soil carbon (C) storage? The answer is critical because woody encroachment may alter C cycling over millions of hectares in the Great Plains and Midwest. We predicted that (1) forest SOC would become concentrated in shallow soil layers compared to SOC distribution in grassland, (2) woody expansion would increase soil C storage, and (3) forest C would be apparent in the larger soil organic matter fractions. Using δ13C signatures of SOC, 1/5 of the C from 0 to 25 cm in juniper forest soils was derived from C3 juniper trees. Forest C3 input occurred primarily in shallow surface layers: Forest soils developed over former C4 prairie contained 42% C3-SOC from 0 to 2.5 cm depth, and decreased to 6% at 25 cm. Isotopic analysis of SOC size fractions revealed that at 0–2.5 cm, the forest soil fraction >212 μm was −25.7‰. The fraction <2 μm had a 13C isotope ratio of −17.0‰ at the same depth, reflecting the predominance of residual prairie C in the smallest fraction. In spite of fast dynamics of soil C turnover, there was no net change in SOC amounts over 40–60 years (cumulative mineral and organic SOC in forest, 8782 g C/m2 ± 810; in grassland, 7699 ± 1004). Thus as junipers expand into mesic areas of the Great Plains, juniper forests will provide little additional soil C storage.

Experimental test of density corrections on CO2 flux as measured using open-path eddy covariance - J.M. Ham; Heilman, J.L. (Agronomy Journal, 2003)
Eddy covariance is the most direct technique for measuring water, C, and energy fluxes above crops and managed ecosystems. When using open-path gas analyzers, corrections for air density fluctuations due to heat and water vapor flux must be applied, and these corrections are often larger in magnitude than the CO2 fluxes. Lack of energy balance closure, a common problem when using eddy covariance, implies that CO2 fluxes often are underestimated. Research was conducted to evaluate performance of the density corrections by making eddy covariance measurements above a large parking lot where CO2 and water vapor fluxes were almost zero. Uncorrected and corrected flux measurements were compared to the “known” values to determine accuracy. Data also were collected from a tallgrass prairie and a cedar forest to examine how density corrections and adjustments for energy balance closure affected daily C balances. Raw measurements from the parking lot showed apparent, density-induced, downward CO2 fluxes (i.e., apparent photosynthesis) of approximately-0.4 mg m−2 s−1 that were correlated with sensible heat. On average, the daily uncorrected CO2 flux was-12.7 g m−2 d−1, but the density correction reduced and changed the direction of the flux to 1.8 g m−2 d−1, which was very close to independent chamber measurements of 2.8 g m−2 d−1 Density corrections in the forest and prairie changed average daily CO2 fluxes by 20 to 80%. Energy balance closure averaged 80 and 95% in the prairie and forest, respectively. Corrections based on energy balance closure changed daily C balances by 16 to 35%. A plethora of post-measurement corrections, coupled with lack of energy balance closure, signals the need for additional research before eddy covariance can be routinely applied in agronomic research.

Factors affecting ammonium uptake in streams - an inter-biome perspective - Webster, J.R.; P. Mulholland; Tank, J.L.; Valett, H.M.; W. K. Dodds; Peterson, B.J.; W.B. Bowden; Dahm, C.N.; S.E.G. Findlay; Gregory, S.V.; Grimm, N.B.; Hamilton, S.K.; et al. (Freshwater Biology, 2003)
1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes. 2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15N-ammonium and downstream measurements of 15N-ammonium concentration. 3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake. 4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa). 5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake.

Grasslands of the North American Great Plains - Henebry, G.M. (Phenology: An Integrative Environmental Science, 2003)
The study of appearances of growth, development, and senescence in grassland communities is not an enterprise commonly pursued. Phenology of mid-latitude grasslands is, nevertheless, too large and diverse a collection of phenomena to cover within a single chapter, as it ought to embrace at once the vast Kazakh steppe, the chalk grasslands of southern England, and myriad other grassy landscapes. Thus, the view here shall be on the grasslands of the North American Great Plains, with particular reference to the tallgrass prairie as a type model.
Keywords: Anthesis; Great Plains; tallgrass prairie; transient maxima hypothesis

The importance of land-use legacies to ecology and conservation - D.R. Foster; Swanson, F.; Aber, J.; I. Burke; Brokaw, N.; Tilman, D.; Alan K. Knapp (BioScience, 2003)
Recognition of the importance of land-use history and its legacies in most ecological systems has been a major factor driving the recent focus on human activity as a legitimate and essential subject of environmental science. Ecologists, conservationists, and natural resource policymakers now recognize that the legacies of land-use activities continue to influence ecosystem structure and function for decades or centuries—or even longer—after those activities have ceased. Consequently, recognition of these historical legacies adds explanatory power to our understanding of modern conditions at scales from organisms to the globe and reduces missteps in anticipating or managing for future conditions. As a result, environmental history emerges as an integral part of ecological science and conservation planning. By considering diverse ecological phenomena, ranging from biodiversity and biogeochemical cycles to ecosystem resilience to anthropogenic stress, and by examining terrestrial and aquatic ecosystems in temperate to tropical biomes, this article demonstrates the ubiquity and importance of land-use legacies to environmental science and management.
Keywords: conservation; disturbance; ecosystem process; Land use; natural resource management

The influence of disturbance from military training activities on terrestrial-aquatic linkages in a tallgrass prairie ecosystem - Quist, M.C.; P. Fay; Guy, C.S.; Alan K. Knapp; Rubenstein, B.N. (Ecological Applications, 2003)
The role of allochthonous organic matter in lotic ecosystems has been an important research topic among aquatic ecologists since the seminal work by Lindeman was published in 1942. Since 1986, studies on organic matter budgets, ecosystem metabolism, and decomposition published in J-NABS have made significant contributions to the overall understanding of organic matter dynamics in streams. In this review, we summarize the utility of organic matter budgets, cover the major advances in research on ecosystem metabolism, and describe the intrinsic and extrinsic factors influencing organic matter decomposition. We also discuss future directions and current applications of research and highlight the need for additional studies on the role of land use and climate change, as well as continued use of organic matter processing as a functional metric in biomonitoring studies. We emphasize the need for continued data synthesis into comprehensive organic matter budgets. Such comparative studies can elucidate important drivers of organic matter dynamics and can assist in the understanding of large continental/global changes that might be occurring now and in the near future. In general, continued emphasis on synthesizing information into a larger framework for streams and rivers will improve our overall understanding of the importance of organic matter in lotic ecosystems.
Keywords: carbon cycling; decomposition; litter breakdown; metabolism; organic matter budgets; organic matter dynamics; streams

Insect diversity in two burned and grazed grasslands - P. Fay (Environmental Entomology, 2003)
This study examined insect diversity in two native grassland ecosystems undergoing burning and grazing by bison and cattle, the Niobrara Valley Preserve (Nebraska) and the Tallgrass Prairie Preserve (Oklahoma). Sweep-sampling for insects was conducted during July 1994 and 1995 along transects in management units that were grazed by bison and partially burned, grazed by cattle and either burned (Tallgrass) or unburned (Niobrara), or ungrazed and unburned. At both sites, species richness (S) and diversity (log series ) were higher and similarity (Sorensen’s index) lower for bison than for cattle or ungrazed management units. High bison management unit diversity was associated with significantly higher S and  in burned (Tallgrass) and unburned (Niobrara) portions of bison units compared with their respective cattle units, suggesting that habitat heterogeneity in terms of plant productivity, composition, and structure were higher in bison versus cattle and ungrazed management units. Replicated factorial experiments and sampling of additional taxa and time points are needed to verify how fire and grazing management impacts insect diversity in these grasslands.
Keywords: fire; Grazing; insects; sandhills prairie; tallgrass prairie

Interdecadal-scale variability: An assessment of LTER climate data - McHugh, M.J.; Goodin, D.G. (Climate Variability and Ecosystem Response at Long-Term Ecological Research Sites, 2003)

An introduction to climate variability and ecosystem response - Greenland, D.; Goodin, D.G.; Smith, R.C. (Climate Variability and Ecosystem Response at Long-Term Ecological Research Sites, 2003)

Invasion of exotic plant species in tallgrass prairie fragments - Cully, A.C.; J.F. Cully Jr.; Hiebert, R.D. (Conservation Biology, 2003)
The tallgrass prairie is one of the most severely affected ecosystems in North America. As a result of extensive conversion to agriculture during the last century, as little as 1% of the original tallgrass prairie remains. The remaining fragments of tallgrass prairie communities have conservation significance, but questions remain about their viability and importance to conservation. We investigated the effects of fragment size, native plant species diversity, and location on invasion by exotic plant species at 25 tallgrass prairie sites in central North America at various geographic scales. We used exotic species richness and relative cover as measures of invasion. Exotic species richness and cover were not related to area for all sites considered together. There were no significant relationships between native species richness and exotic species richness at the cluster and regional scale or for all sites considered together. At the local scale, exotic species richness was positively related to native species richness at four sites and negatively related at one. The 10 most frequently occurring and abundant exotic plant species in the prairie fragments were cool-season, or C3, species, in contrast to the native plant community, which was dominated by warm-season, or C4, species. This suggests that timing is important to the success of exotic species in the tallgrass prairie. Our study indicates that some small fragments of tallgrass prairie are relatively intact and should not be overlooked as long-term refuges for prairie species, sources of genetic variability, and material for restoration.
Keywords: tallgrass prairie

Long-term patterns of shrub expansion in a C4-dominated grassland: fire frequency and the dynamics of shrub cover and abundance - Heisler, J.L.; J. M. Briggs; Alan K. Knapp (American Journal of Botany, 2003)
Worldwide, grassland ecosystems have experienced a major shift in growth-form dominance as woody plant species have expanded and replaced native grasses. In the C4-dominated grasslands of central North America, a reduction in fire frequency is the most cited cause of this shift in growth forms as fire both enhances grass productivity and constrains the establishment and expansion of native woody vegetation. Using an 18-yr plant species composition data set, we quantified patterns of change in shrub cover, frequency, and species richness associated with three distinct fire regimes. During the study period (1983–2000), shrub cover increased most dramatically in sites in which the frequency of fire was once every 4 yr (intermediate frequency; 28.6%) followed by sites in which fire occurred only once during the 18-yr period (low frequency; 23.7%). Annual fire effectively prevented the recruitment of new woody species, but even with this high fire frequency, shrub cover increased slightly (3.7%). Comparatively, shrub species richness increased by three and six, respectively, in the intermediate- and low-frequency fire sites. These data indicate that within this grassland, periods without fire are necessary for recruitment of both new individuals and additional shrub species; however, once established, shrub cover will increase regardless of fire frequency and even annual fire will not reduce shrub abundance.
Keywords: C4 grassland; Fire frequency; growth form substitution; Shrubs; woody encroachment

Misuse of inorganic N and soluble reactive P concentrations to indicate nutrient status of surface waters - W. K. Dodds (Journal of the North American Benthological Society, 2003)
Dissolved inorganic N (DIN) and soluble reactive P (SRP) have been used by some to indicate the trophic status of waters, and concentration ratios (DIN:SRP) to indicate nutrient deficiency. The utility of such measurements should be questioned, particularly based on well-known problems associated with determination of the concentration of SRP, which is commonly assumed to represent PO43−. Another potential problem with using inorganic nutrient pools to represent trophic state and nutrient availability ratios arises because concentration values are in units of mass per unit volume, and cannot be used with certainty to estimate supply (i.e., turnover rate of the nutrient pool, expressed either in mass per unit volume per unit time or simply as per unit time) to organisms without information on uptake and remineralization. Two data sets with lotic water-column nutrient values were explored, a large, continental-scale data set with analyses and collections done by many laboratories, and a more limited data set collected and analyzed by the same laboratory. In concert, the data sets indicated that at high total N (TN) (i.e., >5 mg/L) and total P (TP) (i.e., >2 mg/L) concentrations, >60% of the nutrient is usually made up of dissolved inorganic forms, but at low levels the ratio of dissolved inorganic to total nutrients is highly variable. Last, DIN:SRP is a weak surrogate for TN:TP and thus should be used with caution to indicate nutrient limitation.
Keywords: ammonium; dissolved reactive phosphorus; inorganic nutrients; Nitrate; nutrient limitation; phosphate; water-quality monitoring

Mycorrhizal symbiosis and insect herbivory in tallgrass prairie - Kula, A.R. (Kansas State University, 2003)

Mycorrhizal symbiosis in the tallgrass prairie: above- and belowground linkages - G.T. Wilson (Kansas State University, 2003)

Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands - Johnson, N.C.; Rowland, D.L.; Corkidi, L.; Egerton-Warburton, L.M.; Allen, E.B. (Ecology, 2003)
Arbuscular mycorrhizal (AM) fungi are integral components of grasslands because most plants are associated with interconnected networks of AM hyphae. Mycorrhizae generally facilitate plant uptake of nutrients from the soil. However, mycorrhizal associations are known to vary in their mutualistic function, and there is currently no metric that links AM functioning with fungal colonization of roots. Mycorrhizal structures differ in their physiological and ecological functioning, so changes in AM allocation to intraradical (inside roots) and extraradical (in soil) structures may signal shifts in mycorrhizal function. We hypothesize that the functional equilibrium model applies to AM fungi and that fertilization should reduce allocation to arbuscules, coils, and extraradical hyphae, the fungal structures that are directly involved in nutrient acquisition and transfer to plants. This study compared AM responses to experimental N enrichment at five grasslands distributed across North America. Samples were collected from replicated N-enriched (and some P-enriched) and control plots throughout the growing season for three years. Intraradical AM structures were measured in over 1400 root samples, extraradical hyphal density was measured in over 590 soil samples, and spore biovolume was analyzed in over 400 soil samples. There were significant site × N interactions for spore biovolume, extraradical hyphae, intraradical hyphae, and vesicles. Nitrogen enrichment strongly decreased AM structures at Cedar Creek, the site with the lowest soil N:P, and it increased AM structures at Konza Prairie, the site with the highest soil N:P. As predicted by the functional equilibrium model, in soils with sufficient P, relative allocation to arbuscules, coils, and extraradical hyphae was generally reduced by N enrichment. Allocation to spores and hyphae was most sensitive to fertilization. At the mesic sites, this response was associated with a shift in the relative abundance of Gigasporaceae within AM fungal communities. This study demonstrates that N enrichment impacts mycorrhizal allocation across a wide range of grassland ecosystems. Such changes are important because they suggest an alteration in mycorrhizal functioning that, in turn, may impact plant community composition and ecosystem function.

Pollination and floral scent biology of Phlox divaricata L. (Polemoniaceae) - Harper, S. (Kansas State University, 2003)

Population differences in effects of fish on Physia integra refuge use - Bernot, R.J. (American Midland Naturalist, 2003)
Prey populations exposed to different sets of predators often adopt distinct antipredator behaviors. We investigated the refuge use of a freshwater pulmonate snail, Physa integra, in the presence and absence of fish predators. Over 80% of snails in sites with fish used refuge, while only 50% used refuge in sites without fish. Snails in sites with fish were also significantly smaller than snails in sites without fish. In a laboratory experiment, the presence of fish did not alter the habitat use of snails collected from a no-fish site, whereas snails collected from a site with fish used refuge when exposed to predation risk. These results support the hypothesis that P. integra exhibit local behavioral adaptations to their predator regime.

Productivity responses to altered rainfall patterns in a C4-dominated grassland - P. Fay; Carlisle, J.D.; Alan K. Knapp; John M. Blair; Scott. L. Collins (Oecologia, 2003)
Rainfall variability is a key driver of ecosystem structure and function in grasslands worldwide. Changes in rainfall patterns predicted by global climate models for the central United States are expected to cause lower and increasingly variable soil water availability, which may impact net primary production and plant species composition in native Great Plains grasslands. We experimentally altered the timing and quantity of growing season rainfall inputs by lengthening inter-rainfall dry intervals by 50%, reducing rainfall quantities by 30%, or both, compared to the ambient rainfall regime in a native tallgrass prairie ecosystem in northeastern Kansas. Over three growing seasons, increased rainfall variability caused by altered rainfall timing with no change in total rainfall quantity led to lower and more variable soil water content (0–30 cm depth), a ~10% reduction in aboveground net primary productivity (ANPP), increased root to shoot ratios, and greater canopy photon flux density at 30 cm above the soil surface. Lower total ANPP primarily resulted from reduced growth, biomass and flowering of subdominant warm-season C4 grasses while productivity of the dominant C4 grass Andropogon gerardii was relatively unresponsive. In general, vegetation responses to increased soil water content variability were at least equal to those caused by imposing a 30% reduction in rainfall quantity without altering the timing of rainfall inputs. Reduced ANPP most likely resulted from direct effects of soil moisture deficits on root activity, plant water status, and photosynthesis. Altered rainfall regimes are likely to be an important element of climate change scenarios in this grassland, and the nature of interactions with other climate change elements remains a significant challenge for predicting ecosystem responses to climate change.
Keywords: Climate change; Konza Prairie; Net primary productivity; Precipitation; soil moisture

Rainfall timing, soil moisture dynamics, and plant responses in a mesic tallgrass prairie ecosystem - P. Fay; Alan K. Knapp; John M. Blair; Carlisle, J.D.; Danner, B.T.; McCarron, J.K. (Precipitation Regimes and Terrestrial Ecosystems. A North American Perspective, 2003)
Keywords: tallgrass prairie

Relationships at the aboveground-belowground interface: Plants, soil biota, and soil processes - Porazinska, D.L.; Bardgett, R.D.; Blaauw, M.B.; Hunt, H.W.; Parsons, A.N.; Seastedt, T.R.; Wall, D.H. (Ecological Monographs, 2003)
Interactions at the aboveground–belowground interface provide important feedbacks that regulate ecosystem processes. Organisms within soil food webs are involved in processes of decomposition and nutrient mineralization, and their abundance and activity have been linked to plant ecophysiological traits such as species identity and the quality and quantity of plant tissue. We tested aboveground–belowground diversity relationships in a naturally developed plant community of native tallgrass prairie by taking soil samples from beneath naturally established grass tillers of chosen characteristics (e.g., homogeneous vs. heterogeneous plant combinations or C4 vs. C3 photosynthetic pathway) without imposing any disturbances to existing plant–soil relationships. The goal of this study was to elucidate the consequences, for soil microbiota (microflora phospholipid fatty acids, protozoa, and nematode functional groups) and for C and N mineralization, of plant community properties such as species richness, resource quality, resource heterogeneity, species identity, and presence of exotics. None of the biotic or abiotic soil variables was related to plant resource heterogeneity. Protozoa were not responsive to any of the plant community traits. Some bacterial and nematode groups were affected by plant characteristics specific to a particular plant species, but no uniform pattern emerged. Invasive and native plants generally were similar with respect to soil variables tested in this study. The lack of clear responses of soil variables to plant community traits indicates that idiosyncratic effects dominate both at the plant and soil biotic level and that generalized plant and soil diversity effects are hard to predict.

Responses of heterotrophic and autotrophic biofilms to nutrients in ten streams - Tank, J.L.; W. K. Dodds (Freshwater Biology, 2003)
1. Nutrient diffusing substrata were used to determine the effect of added inorganic nitrogen (N) and phosphorus (P) on the development of epilithic and epixylic biofilms in 10 North American streams. Four treatments of diffusing substrata were used: Control (agar only), N addition (0.5 m NaNO3), P addition (0.5 m KH2PO4), and N + P combined (0.5 m NaNO3 + 0.5 m KH2PO4). Agar surfaces were covered with glass fibre filters (for epilithon) or discs of untreated white oak wood veneer (for epixylon). 2. We found that if algae showed significant response to nutrient addition, N limitation (either N alone or N with P) was the most frequent response both on GF/F filters and on wood. Despite the low dissolved nutrient concentrations in our study streams, more than a third of the streams did not show any response to N or P addition. In fact, P was never the sole limiting nutrient for algal biofilms in this study. 3. Nutrient addition influenced algal colonisation of inorganic versus organic substrata in different ways. The presence of other biofilm constituents (e.g. fungi or bacteria) may influence whether algal biomass on wood increased in response to nutrient addition. Algae on organic and inorganic substrata responded similarly to nutrient addition in only one stream. 4. Fungal biomass on wood was nutrient limited in six of 10 study streams. N limitation of fungal biomass (with or without secondary P limitation) was most frequent, but P limitation did occur in two streams. 5. Our results show that biomass responses to nutrient addition by the heterotrophic and autotrophic components of the epixylic biofilm were different, though both experienced the same stream nutrient conditions. For algae and fungi growing on wood, limiting nutrients were rarely similar. Only three of nine streams showed the same biomass response to nutrient addition, including two that showed no significant change in biomass despite added nutrients.

Riparian impacts on water quality in eastern Kansas watersheds - Oakes, R.M. (Kansas State University, 2003)

The role of periphyton in phosphorus retention in shallow freshwater aquatic systems - W. K. Dodds (Journal of Phycology, 2003)
Eutrophication caused by phosphorus (P) leads to water quality problems in aquatic systems, particularly freshwaters, worldwide. Processing of nutrients in shallow habitats removes P from water naturally and periphyton influences P removal from the water column in flowing waters and wetlands. Periphyton plays several roles in removing P from the water column, including P uptake and deposition, filtering particulate P from the water, and attenuating flow, which decreases advective transport of particulate and dissolved P from sediments. Furthermore, periphyton photosynthesis locally increases pH by up to 1 unit, which can lead to increased precipitation of calcium phosphate, concurrent deposition of carbonate-phosphate complexes, and long-term burial of P. Actively photosynthesizing periphyton can cause super-saturated O2 concentrations near the sediment surface encouraging deposition of metal phosphates. However, anoxia associated with periphyton respiration at night may offset this effect. Linking the small-scale functional role of periphyton to ecosystem-level P retention will require more detailed studies in a variety of ecosystems or large mesocosms. A case study from the Everglades illustrates the importance of considering the role of periphyton in P removal from wetlands. In general, periphyton tends to increase P retention and deposition. In pilot-scale constructed periphyton-dominated wetlands in South Florida, about half of the inflowing total P was removed.
Keywords: eutrophication; microalgae; microphytobenthos; periphyton; phosphate; Phosphorus; tertiary treatment; water quality

Soil C and N responses to woody plant expansion in a mesic grassland - McCarron, J.K.; Alan K. Knapp; John M. Blair (Plant and Soil, 2003)
Changes in land management and reductions in fire frequency have contributed to increased cover of woody species in grasslands worldwide. These shifts in plant community composition have the potential to alter ecosystem function, particularly through changes in soil processes and properties. In semi-arid grasslands, the invasion of shrubs and trees is often accompanied by increases in soil resources and more rapid N and C cycling. We assessed the effects of shrub encroachment in a mesic grassland in Kansas (USA) on soil CO2 flux, extractable inorganic N, and N mineralization beneath shrub communities (Cornus drummondii) and surrounding undisturbed grassland sites. In this study, a shift in plant community composition from grassland to shrubland resulted in a 16% decrease in annual soil CO2 flux(4.78 kg CO2 m−2 year−1 for shrub dominated sites versus 5.84 kg CO2 m−2 year−1 for grassland sites) with no differences in total soil C or N or inorganic N. There was considerable variability in N mineralization rates within sites, which resulted in no overall difference in cumulative N mineralized during this study (4.09 g N m−2 for grassland sites and 3.03 g N m−2 for shrub islands). These results indicate that shrub encroachment into mesic grasslands does not significantly alter N availability (at least initially), but does alter C cycling by decreasing soil CO2 flux.
Keywords: N availability; N mineralization; shrub invasion; soil CO2 flux; soil properties

Soil resources regulate productivity and diversity in newly established tallgrass prairie - S.G. Baer; John M. Blair; Alan K. Knapp; Scott. L. Collins (Ecology, 2003)
In native tallgrass prairie, soil depth and nitrogen (N) availability strongly influence aboveground net primary productivity (ANPP) and plant species composition. We manipulated these factors in a newly restored grassland to determine if these resources similarly constrain productivity and diversity during the initial three years of grassland establishment. Four types of experimental plots with six treatment combinations of deep and shallow soil at reduced-, ambient-, and enriched-N availability formed the basis of this study. The soil responses to the experimental treatments were examined over three years, and patterns in diversity and productivity were examined in year 3. The soil depth treatment did not significantly affect soil carbon (C) and N pools or ANPP and diversity. A pulse amendment of C added to the soil prior to planting increased soil microbial biomass and decreased potential net N mineralization rates to effectively reduce N availability throughout the study. Nitrogen availability declined over time in nonamended soils as a result of plant establishment, but adding fertilizer N alleviated the increasing immobilization potential of the soil. The level of ANPP was lowest and diversity highest in the reduced-N treatment, whereas the enriched-N treatment resulted in high productivity, but low diversity. As a result, diversity was inversely correlated with productivity in these newly established communities. The same mechanism invoked to explain decreased diversity under nutrient enrichment in old-field ecosystems and native grasslands (e.g., reduced light availability with increased production) was supported in the restored prairie by the positive relationship between ANPP and intercepted light, and a strong correlation between light availability and diversity. The effects of nutrient availability on plant community composition (diversity and richness) were due primarily to the responses of prairie species, as the productivity of early successional, nonprairie species was less than 1% of total ANPP after three years of establishment. These results show that the effects of resource availability on productivity and diversity are similar in young and mature grasslands, and that manipulation of a limiting nutrient during grassland establishment can influence floristic composition, with consequences for long-term patterns of diversity in restored ecosystems.
Keywords: tallgrass prairie

Spatial heterogeneity in the herbaceous layer of a semi-arid savanna ecosystem - Augustine, D.J. (Plant Ecology, 2003)
Despite increasing recognition of the role spatial pattern can play in ecosystem function, few studies have quantified spatial heterogeneity in savanna ecosystems. The spatial distribution of herbaceous biomass and species composition was measured across three scales in a semi-arid savanna in central Kenya, and patterns were related to environmental variables at different scales. Herbaceous biomass declined across a rainfall gradient and from upper to lower topographic positions, but variation within a site (across 5–50 m) was similar in magnitude to among-site variation associated with rainfall and topography. Geostatistical analyses showed that patchiness at scales of 5–25 m explained 20% of total variation in herbaceous biomass. This pattern arose from the presence of both 5–10-m diameter patches containing high herbaceous biomass (> 170 g m−2) and 5–10-m diameter patches characterized by nearly bare soil surfaces (< 40 g m−2). Patch structure was contingent on topography, with larger bare patches at ridgeline and upper hillslope positions. Grass species distributions showed the greatest degree of patch structure and species turnover across distances of 5–45 m. Additional community variation was associated with topography, with minimal variation in species composition across the rainfall gradient. Pattern diversity significantly exceeded levels reported for four other grassland ecosystems, suggesting fundamental differences in local processes generating spatial pattern. It is hypothesized that heterogeneously distributed grazing pressure, interacting with the distribution of shrub canopies, is an important factor generating such high levels of small-scale patch structure in this savanna.
Keywords: Geostatistics; Laikipia; Pattern diversity; Plant community patch structure; topography; Ungulate grazing

Spatial variation in brown-headed cowbird(Molothrus ater) abundance and brood parasitism in the Flint Hillstallgrass prairie - Jensen, W.E. (Kansas State University, 2003)

Temporal responses of NDVI to precipitation and temperature in the central Great Plains, USA - Wang, J.R.; Price, K.P. (International Journal of Remote Sensing, 2003)
Normalized Difference Vegetation Index (NDVI) is generally recognized as a good indicator of terrestrial vegetation productivity. Understanding climatic influences, in particular precipitation and temperature, on NDVI enables prediction of productivity changes under different climatic scenarios. We examined temporal responses of remotely sensed NDVI to precipitation and temperature during a nine-year period (1989-97) in Kansas. Biweekly (every two weeks) and monthly precipitation data were derived from 410 weather stations and biweekly temperature data were derived from 17 weather stations inside and around the borders of Kansas. Biweekly and monthly climate maps were derived by interpolation. Biweekly growing season (March-October) NDVI values for Kansas were calculated using National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) NDVI images. Average growing season NDVI values were highly correlated with precipitation received during the current growing season and seven preceding months (15-month duration); biweekly NDVI values were correlated with precipitation received during 2-4 preceding biweekly periods; and response time of NDVI to a major precipitation event was typical 1-2 biweekly periods (2-4 weeks). Temperature was positively correlated with NDVI early and late in the growing season, and there was a weak negative correlation between temperature and NDVI in the mid growing season. Precipitation has the primary influence on NDVI and, by inference, on productivity. The relationship between precipitation and NDVI is strong and predictable when viewed at the appropriate spatial scale.

Trematode infection alters the antipredator behavior of a pulmonate snail - Bernot, R.J. (Journal of the North American Benthological Society, 2003)
Parasites can alter the behavior, life history, and morphology of their host. Many trematodes parasitize freshwater pulmonate snails, resulting in a reduction or the elimination of reproduction in those individuals. However, parasite effects on freshwater snail behavior are unclear. I measured trematode infection rates, size, and covered habitat use of the freshwater pulmonate snail Physa integra in a field survey of streams and ponds on Konza Prairie Biological Station. Then, in a laboratory experiment, I tested the hypothesis that behavioral decisions under the risk of predation differed between infected and uninfected P. integra. Infection rates ranged from 2% to 53% overall, but varied between snail size class and site of collection. Significantly fewer infected (7%) than uninfected P. integra (29%) were found under cover, but there was no difference in use of cover between snails infected with Paramphistomidae and Cathaemasiidae trematodes. A significantly greater proportion of larger snail size classes were infected than smaller size classes. In the laboratory experiment, habitat use by P. integra depended on predator presence and infection status. Significantly more uninfected snails used covered habitats in the presence of creek chub (Semotilus atromaculatus) than in the presence of crayfish (Orconectes nais) or in the absence of a predator. Significantly more uninfected snails used near-surface habitat in the presence of O. nais than in other treatments. However, in the presence of S. atromaculatus <20% of infected snails used cover compared to 60% of uninfected snails. Near-surface habitat use and crawlout behavior were also significantly higher among infected snails in crayfish and no predator treatments, suggesting that infected snails use near-surface habitats even when under predation risk. More detailed knowledge of this trematode–snail system is necessary, however, to determine if differences in habitat use between infected and uninfected snails is an adaptive manipulation of snail behavior by trematodes. Nevertheless, these results indicate that infection status affects the behavior of P. integra and may alter species interactions in freshwater benthic communities.
Keywords: antipredator behavior; cercariae; habitat use; parasitism; Physa integra; trematodes

Use of bison wallows by anurans on Konza Prairie - N.M. Gerlanc; Kaufman, G.A. (American Midland Naturalist, 2003)
Historically, bison were of great importance to the grassland ecosystem, affecting plants and other organisms directly through grazing and indirectly by creating soil disturbances, such as wallows. When bison were reintroduced to the Konza Prairie Biological Station, Kansas, they reactivated relic wallows as well as created new ones. Wallows, like other ephemeral pools, may be used by organisms as aquatic habitat and as breeding sites. The objective of our study was to systematically monitor bison wallows after they filled and to ascertain their use by amphibians. We also examined long-term climatic records from the Konza Prairie area to assess the past viability of bison wallows as breeding habitats for anurans, which must complete metamorphosis before wallows dry. The amount of precipitation and cool temperatures required to prolong the hydroperiod necessary for completion of metamorphosis occurred in only about 20% of the years examined. Bison may have been important in the life histories of prairie anurans by creating “pools” in the form of wallows that could be used as breeding sites. However, more information about the life history of individual species of anurans is needed before viability of bison wallows as a breeding habitat can be determined.

Vegetation dynamics from annually burning tallgrass prairie in different seasons - Towne, E.G.; Kemp, K.E. (Journal of Range Management, 2003)
Traditional perception of how tallgrass prairie responds to fire at times other than late spring is either anecdotal or extrapolated from studies that lack spatial or temporal variability. Therefore, we evaluated patterns of change in vegetation cover, species richness, diversity, and aboveground biomass production on 2 different topographic positions from ungrazed watersheds that were burned annually for 8 years in either autumn (November), winter (February), or spring (April). Topoedaphic factors influenced the response patterns of some species to seasonal fire, although differences were primarily in the rate of change. Annual burning in autumn and winter produced similar trends through time for most species. Big bluestem (Andropogon gerardii Vitman) cover increased with all burn regimes, whereas indiangrass [Sorghastrum nutans (L.) Nash] increased only with spring burning. Repeated autumn and winter burning eventually increased perennial forb cover, with the largest increases occurring in heath aster [Symphyotrichum ericoides (L.) Nesom], aromatic aster [S. oblognifolium (Nutt.) Nesom], tall goldenrod (Solidago canadensis L.), and legumes. Species richness increased (P<0.001) through time with spring and winter burning, but was similar among all burn treatments after 8 years of annual fire. Average grass and forb biomass did not differ among burn seasons on either topographic position, although interannual biomass production fluctuated inconsistently with time of burn. Our findings contrast with many of the conventional views of how tallgrass prairie vegetation responds to seasonal fire and challenges traditional recommendations that burning should only occur in late spring.
Keywords: tallgrass prairie

Aboveground invertebrate responses to land management differences in a central Kansas grassland - Jonas, J.; M.R. Whiles; Charlton, R.E. (Environmental Entomology, 2002)
Macroinvertebrate communities in a central Kansas grassland were examined to assess their responses to differences in land management and explore their viability for biological assessment of grasslands. Canopy (drop-trap) and ground-dwelling (pitfall traps) communities were quantitatively sampled from June-September 1998 and 1999. The responses of the whole arthropod community and two focal groups, Coleopteran families and Orthopteran species, to three land use types (brome fields, old fields, and native prairies) were examined. Vegetation analyses reflected clear differences among land use types. Bromus inermis Leyss, an exotic grass, and Andropogon gerardii Vitman, a native grass, dominated brome fields and native prairie sites, respectively. Old fields were composed of a mixture of native and exotic plant species. Coleopteran family richness and diversity were significantly greater in native prairies than brome fields (P < 0.05), whereas orthopteran species richness and diversity peaked in brome fields. Diversity and richness of all arthropod groups examined were significantly, positively correlated with plant species diversity and richness in drop-trap samples (P < 0.05). Coleopteran family diversity and richness in pitfall samples were positively correlated with abundance of native plants, but orthopteran species diversity and richness were negatively correlated with native plant abundance. Coleopteran and orthopteran responses to land use appeared linked to differences in management practices. Whereas coleopterans appeared most influenced by plant community composition, orthopterans showed sensitivity to mechanical disturbance associated with haying on native prairie. Plant and arthropod group diversities were not consistently correlated, demonstrating that arthropod groups can reflect differences in a landscape that may not be apparent from examining plant communities alone.
Keywords: biological assessment; Coleoptera; indicator species; Orthoptera

Altered rainfall patterns affect belowground ecosystem processes in a tallgrass prairie - Harper, C.W. (Kansas State University, 2002)
Keywords: tallgrass prairie

Altered rainfall patterns, gas exchange and growth in C3 and C4 grassland species - Fay, P.A.; Carlisle, J.D.; Danner, B.T.; Lett, M.S.; McCarron, J.K.; Stewart, C.; Alan K. Knapp; John M. Blair; Scott. L. Collins (International Journal of Plant Sciences, 2002)

Annual fire, mowing and fertilization effects on two cicadas (Homoptera:Cicadidae) in tallgrass prairie - Callaham, M.A.; M.R. Whiles; John M. Blair (American Midland Naturalist, 2002)
In tallgrass prairie, cicadas emerge annually, are abundant and their emergence can be an important flux of energy and nutrients. However, factors influencing the distribution and abundance of these cicadas are virtually unknown. We examined cicada emergence in plots from a long-term (13 y) experimental manipulation involving common tallgrass prairie management practices. The plots were arranged in a factorial experimental design, incorporating annual burning, mowing and fertilization (10 g N m−2 and 1 g P m−2). One cicada species, Cicadetta calliope, responded positively to fire, but negatively to mowing, and was most abundant in plots that were burned, unmowed and fertilized. Increased density of C. calliope in this treatment combination is related, in part, to increased availability of oviposition sites aboveground. Furthermore, C. calliope females from fertilized plots were significantly larger in body size relative to females from unfertilized prairie. Another cicada species, Tibicen aurifera, emerged only from unburned plots. The mechanism underlying this negative response to fire is unclear, but may be related to the presence of standing dead vegetation or improved quality (i.e., N content) of belowground plant tissue in unburned plots. In contrast to C. calliope, the density of T. aurifera was not affected by mowing or fertilization. However, like C. calliope, the body size of T. aurifera females was significantly greater in fertilized plots. Cicada emergence resulted in N flux ranging from 0.05–0.16 g N m−2 in unburned plots, but N flux (as cicada biomass) from annually burned plots was negligible.
Keywords: tallgrass prairie

Applications of advanced technologies in studying and managing grassland landscape integrity - Hoch, G.; B. Brock; J. M. Briggs (Integrating Landscape Ecology into Natural Resource Management, 2002)
Keywords: grassland; landscape

Assessing the rate, mechanism and consequences of conversion of tallgrass prairie to Juniperus virginiana forest - Hoch, G.A.; J. M. Briggs; Johnson, L.C. (Ecosystems, 2002)
We assessed the determinants and consequences of the expansion of Juniperus virginiana L. (red cedar) populations into central US grasslands using historical aerial photos and field measurements of forest extent, tree growth, fire-induced mortality, and responses in herbaceous species diversity and productivity. Photos from northeast Kansas dating back to 1956 indicate that native tallgrass prairie can be converted to closed-canopy red cedar forest in as little as 40 years (a 2.3% increase in forest cover per year). Mean tree density in 21 forested sites ranged from 130 to 3500 trees/ha, with most sites at more than 800 trees/ha. In younger stands, maximum growth rates of individual red cedar trees exceeded 20 cm/y in height. Land management practices were critical to the establishment and growth of red cedar forest. Grazing reduced the fuel loads by more than 30% in tallgrass prairie. Based on measurements of mortality for more than 1800 red cedar trees, fire-induced mortality in grazed areas averaged 31.6% versus more than 90% at ungrazed sites. When tallgrass prairie was converted to red cedar forest, herbaceous species diversity and productivity were drastically reduced, and most grassland species were virtually eliminated. Consequently, community structure shifted from dominance by herbaceous C4 species to evergreen woody C3 species; this shift is likely to be accompanied by alterations in carbon storage and other ecosystem processes in a relatively short time period. Here we present a conceptual model that integrates the ecological and socioeconomic factors that underlie the conversion of grassland to red cedar forest.
Keywords: fire; forest expansion; Grazing; Juniperus virginiana; land-cover change; land-use change; red cedar; tallgrass prairie

Biodiversity analysis with multi-scale images in Konza Prairie Biological Station - Gao, J.; Goodin, D.G. (2002)

Biogeochemical response of U.S. Great Plains grasslands to regional and interannual variability in precipitation - McCulley, R.L. (Colorado State University, 2002)

Biogeographic variation in nest placement: a case study with conservation implications - Parody, J.M.; Parker, T.H. (Diversity and Distributions, 2002)
Local habitat characteristics are often used to describe a species’ niche despite the fact that habitat use can vary across the geographical range. We sought to quantify variation in habitat preferences by asking how nesting habit varies within and between populations of Bell’s vireo (Vireo bellii) across its geographical range. Analyses of detailed nest placement data from three localities (Kansas, eastern New Mexico and western New Mexico) showed a general trend towards use of dense vegetation. However, there was substantial variation in nest placement and vegetation at nest sites between localities. Furthermore, a review of nest placement data from the literature shows strong differences in nest heights and species of trees even between populations less than 100 km apart. We evaluate these results in light of conservation and suggest that to be most effective, habitat conservation plans should be based on data collected at the locality where the population of interest occurs.

Can uptake length in streams be determined by nutrient addition experiments? Results from an inter-biome comparison study - Mulholland, P.J.; Tank, J.L.; Webster, J.R.; W.B. Bowden; W. K. Dodds; Gregory, S.V.; Grimm, N.B.; Hamilton, S.K.; Johnson, S.L.; Marti, E.; W.H. McDowell; Merriam, J.; et al. (Journal of the North American Benthological Society, 2002)
Nutrient uptake length is an important parameter for quantifying nutrient cycling in streams. Although nutrient tracer additions are the preferred method for measuring uptake length under ambient nutrient concentrations, short-term nutrient addition experiments have more frequently been used to estimate uptake length in streams. Theoretical analysis of the relationship between uptake length determined by nutrient addition experiments (SW′) and uptake length determined by tracer additions (SW) predicted that SW′ should be consistently longer than SW, and that the overestimate of uptake length by SW′ should be related to the level of nutrient addition above ambient concentrations and the degree of nutrient limitation. To test these predictions, we used data from an interbiome study of NH4+ uptake length in which 15NH4+ tracer and short-term NH4+ addition experiments were performed in 10 streams using a uniform experimental approach. The experimental results largely confirmed the theoretical predictions: SW′ was consistently longer than SW and SW′:SW ratios were directly related to the level of NH4+ addition and to indicators of N limitation. The experimentally derived SW′:SW ratios were used with the theoretical results to infer the N limitation status of each stream. Together, the theoretical and experimental results showed that tracer experiments should be used whenever possible to determine nutrient uptake length in streams. Nutrient addition experiments may be useful for comparing uptake lengths between different streams or different times in the same stream, however, provided that nutrient additions are kept as low as possible and of similar magnitude.
Keywords: ammonium; nitrogen limitation; nutrient cycling; nutrient spiraling; stream; uptake length

Causes and consequences of species invasion and loss: the role of dominant species and diversity in maintaining ecosystem function - M.D. Smith (Kansas State University, 2002)

Changes in ecosystem structure and function along a chronosequence of restored grasslands - S.G. Baer; Kitchen, D.J.; John M. Blair; C. W. Rice (Ecological Applications, 2002)
Changes in aboveground vegetation, roots, and soil characteristics were examined from a 12-yr chronosequence of formerly cultivated fields restored to native C4 grasses through the Conservation Reserve Program (CRP). Following 6–8 yr in the CRP, the native grasses dominated vegetation composition, and the presence of forbs was negligible. Productivity of the restored grasslands did not exhibit any directional changes with the number of years in the CRP, and productivity was generally higher than native prairie in this region. Over time, the restored grasslands accumulated root biomass of decreasing quality as indicated by increasing root biomass and C:N ratio of roots along the 12-yr chronosequence. Root biomass, root C:N ratio, C storage in roots, and N storage in roots of restored grasslands approached that of native tallgrass prairie within the 12 yr of restoration. Establishment of the perennial vegetation also affected soil physical, chemical, and biological characteristics. Soil bulk density in the surface 10 cm decreased with time since restoration. Total C, microbial biomass C, and C mineralization rates increased as a function of time since restoration. The greatest change in total C occurred in the surface 5 cm, where total C was 26% greater in 12- vs. 2-yr restored grasslands. Extractable soil nitrate and soil N transformations (i.e., net N mineralization rates and net nitrification rates) declined over the restoration chronosequence, but these values were not representative of steady-state conditions due to the high variability in these measures among the native prairies. Although complete restoration of ecosystem structure and function was not the primary intention of the CRP, this study demonstrates that establishment of the matrix vegetation (i.e., native C4 grasses) drives ecosystem processes in the trajectory of the original system. Moreover, restoration may hasten the recovery of soil C pools relative to formerly cultivated systems undergoing natural succession.
Keywords: ecosystem; function; grassland; structure

Climate variability at multiple time scales: implications for productivity in tallgrass prairie - Goodin, D.G.; Fay, P.A.; McHugh, M.J. (American Meteorological Society, 2002)
Climate is a fundamental driver of biomass productivity in ecosystems. This is especially true for grassland systems, which display greater variability in net primary productivity in response to climate fluctuation than forest, desert, or arctic/alpine systems. Although basic climate/productivity relationships have been studied over shorter time scales, the effect of longer-term climate processes such as El Niño/Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), solar activity cycles, and other quasiperiodic climatic patterns on grassland systems is largely unknown, due to the lack of long term productivity data sets to evaluate against climate data. Here, we examine how variability in temperature and rainfall at a tallgrass prairie site (Konza Prairie Biological Station, KPBS) is related to various teleconnection indices and how these indices may relate to patterns of above ground net primary productivity (ANPP). We use two data sets, a 20 year ANPP data set collected at KPBS and a 108 year precipitation and temperature record (1891-1999) from nearby Manhattan, KS. Patterns of variation are analyzed using period-spectrum analysis and correlation of climate variables to ANPP. Results show that at shorter time scales (one year or less), productivity is influenced by magnitude of precipitation and temperature, but also by the seasonal timing of precipitation events and heat accumulation. Long-term precipitation was influenced on the decadal time scale by the NAO and North Pacific (NP) circulation patterns. Long-term temperature patterns showed strongest periodicities at intradecadal time scales (" 5- 8 years), and correlated most strongly with ENSO indices. Although speculative, our results suggest that the influence of atmospheric teleconnection patterns (and their resulting weather patterns) on tallgrass productivity is indirect. Teleconnection patterns interact to influence both the magnitude and seasonal distribution of temperature and precipitation. The interplay of these variations in weather appears to exert significant control over tallgrass ANPP.

Clone size of Andropogon gerardii Vitman (Big Bluestem) at Konza Prairie, Kansas - Keeler, K.H.; Williams, C.F.; Vescio, L.S. (American Midland Naturalist, 2002)
Clone size of plants of Andropogon gerardii from Konza Prairie Biological Station, Manhattan, Kansas was estimated from spatial patterns of genetic variation, using proteins detected by starch gel electrophoresis and DNA content (ploidy) measured by flow cytometry. Unique multi-locus protein banding patterns and differences in ploidy were used to exclude plants as members of the same clone. Individual clones averaged about 2 m in diameter and areas of prairie of 100 m2 were calculated to contain an average of 31.8 genetic individuals.

Comparisons of nitrification and denitrification in prairie and agriculturally influenced streams - Kemp, M.J.; W. K. Dodds (Ecological Applications, 2002)
Whole-stream nitrification and denitrification rates were calculated from field incubation studies of representative substrata in Kings Creek and Shane Creek watersheds at the Konza Prairie Biological Station, Kansas, USA. Substrata from a relatively pristine upstream and an agriculturally influenced downstream reach were measured in both watersheds. Rates were scaled to the whole stream by the mass of each substratum in the stream reach. Substrata sampled included epilithon, leaf packs and wood (coarse benthic organic matter, CBOM), filamentous green algae, bryophytes, fine benthic organic matter (FBOM), and suspended particulate organic matter. Upstream sites had significantly lower nitrification and denitrification rates than downstream sites. Nitrification rates were dominated by nitrification associated with epilithon and filamentous green algae. Downstream sites had a higher proportion of nitrification occurring in the water column relative to upstream sites. Whole-stream denitrification was dominated by denitrification associated with FBOM and CBOM and was higher downstream. Water column ammonium (NH4+) and nitrate (NO3−) concentrations were correlated with whole-stream nitrification rates but not whole-stream denitrification rates. Whole-stream nitrification rates were positively correlated with whole-stream denitrification rates, being coupled at the whole-stream level, but not at the substratum level. Relative to the amount of NO3− produced through nitrification, the proportion of NO3− denitrified was 1.4–4.6 times greater in the downstream sites compared to the upstream sites, but the proportion of the in-stream NO3− load denitrified was ∼10 times greater in the upstream sites. These data indicate that changes in stream nitrogen cycling related to increased dissolved inorganic nitrogen concentrations do not result in a large enough increase in denitrification (the stream's capacity to retain nitrogen) to compensate for the increased nitrogen loading. Data also suggest that whole-stream nitrification and denitrification may be decoupled at the reach level by factors that decrease habitat heterogeneity (the variety of substrata types) in stream channels. This indicates that anthropogenic disturbances of small streams, such as channelization and removal of riparian vegetation, would be expected to decrease the capacity of streams to retain nitrogen.
Keywords: nitrification; prairie; stream

A cross-system comparison of bacterial and fungal biomass in detritus pools of headwater streams - Findlay, S.E.G.; Tank, J.; Dye, S.; Vallett, H.M.; Mulholland, P.J.; W.H. McDowell; Johnson, S.; Hamilton, S.K.; Edmonds, J.; W. K. Dodds; W.B. Bowden (Microbial Ecology, 2002)

Distribution of eastern woodrats in a grassland-woodland mosaic: influence of vegetation and fire - Beckmann, J.P.; Kaufman, G.A.; D.W. Kaufman (Great Plains Research, 2002)
Keywords: eastern woodrat; Konza Prairie; prairie fires; tallgrass prairie

Ecological interactions between grasses and shrubs in a tallgrass prairie - McCarron, J.K. (Kansas State University, 2002)
Keywords: tallgrass prairie

Effect of local and regional processes on plant species richness in tallgrass prairie - Scott. L. Collins; Glenn, S.M.; J. M. Briggs (Oikos, 2002)
Historically, diversity in a community was often believed to result primarily from local processes, but recent evidence suggests that regional diversity may strongly influence local diversity as well. We used experimental and observational vegetation data from Konza Prairie, Kansas, USA, to determine if: (1) there is a relationship between local and regional richness in tallgrass prairie vegetation; (2) local dominance reduces local species richness; and (3) reducing local dominance increases local and regional species richness. We found a positive relationship between regional and local richness; however, this relationship varied with grazing, topography and fire frequency. The decline in variance explained in the grazed vegetation, in particular, suggested that local processes associated with grazing pressure on the dominant grasses strongly influenced local species richness. Experimental removal of one of the dominant grasses, Andropogon scoparius, from replicate plots resulted in a significant increase in local species richness compared to adjacent reference plots. Overall all sites, species richness was higher in grazed (192 spp.) compared to ungrazed (158 spp.) areas. Across the Konza Prairie landscape, however, there were no significant differences in the frequency distribution of species occurrences, or in the relationship between the number of sites occupied and average abundance in grazed compared to ungrazed areas. Thus, local processes strongly influenced local richness in this tallgrass prairie, but local processes did not produce different landscape-scale patterns in species distribution and abundance. Because richness was enhanced at all spatial scales by reducing the abundance of dominant species, we suggest that species richness in tallgrass prairie results from feedbacks between, and interactions among, processes operating at multiple scales in space and time.
Keywords: tallgrass prairie

The effect of rescaling on fine spatial resolution NDVI data: a test using multi-resolution aircraft data - Goodin, D.G.; Henebry, G.M. (International Journal of Remote Sensing, 2002)
Simulation studies have suggested that pixel aggregation can rescale accurately both Normal Difference Vegetation Index (NDVI) data and fields of biogeophysical values inferred from NDVI. There is, however, a dearth of empirical tests of this hypothesis. This study uses nested NDVI observations acquired from an aircraft-mounted digital camera to assess the spatial properties of measured and rescaled image data. Imagery was collected at four altitudes, yielding spatial resolutions varying from 0.625 m to 3.125 m. The common area from these four images was extracted. The finest spatial resolution image was then rescaled by aggregating pixels to synthesize three rescaled images matching the spatial resolution of the measured images. The spatial properties of these measured and rescaled images were compared, using metrics derived from the variogram. Results demonstrate that the spatial patterns of rescaled data do not correspond to those of the directly observed data. The results suggest that rescaling by averaging blocks of pixels may not adequately preserve spatial properties of very high spatial resolution images and consequent inferred biogeophysical fields.

Effects of grazing intensity on growth, reproduction, and abundances of three palatable forbs in Kansas tallgrass prairie - Hickman, K.R.; D.C. Hartnett (Plant Ecology, 2002)
The effects of different intensities of cattle grazing on the aboveground growth, reproduction, and abundances of three palatable forbs were studied in native tallgrass prairie. Populations of Aster ericoides, Ruellia humilis, and Amorpha canescens were sampled at peak flowering during the 1993-1995 growing seasons in four annually-burned sites varying in cattle stocking density [ungrazed, low, moderate, high]. The three forbs exhibitedreduced shoot growth and/or reproduction under moderate to heavy grazing, and in no case did grazing increase any measure of plant performance. Ruellia showed reduced shoot height and biomass, percentage of stemsflowering, and reproductive biomass in response to grazing. Aster showed decreases in shoot biomass and height with grazing. Amorpha showed no change in shoot or reproductive biomass, but a decrease in percent of flowering stems and in reproductive allocation with grazing. Patterns in the percentage of stems grazed indicated generally high but variable palatability among these species. By contrast, the three species showedinconsistent population response to grazing. Abundance (frequency) of all three species indicated no short-term change between years in response to grazing intensity. Responses of these species differ considerably from those of most other perennial tallgrass prairie forbs that are unpalatable, unconsumed, and increase in performance (e.g. size, abundance) due to release from competition from the dominant grasses under ungulate grazing. The results demonstrate that immediate aboveground growth and reproductiveresponses of established adults to grazing are not good predictors of grazer effects on population abundances in tallgrass prairie.
Keywords: flowering

Environmental controls on soil and whole-ecosystem respiration from a tallgrass prairie - Franzluebbers, K.; Franzluebbers, A.J.; Jawson, M.D. (Soil Science Society of America Journal, 2002)
Environmental controls on C cycling in terrestrial ecosystems are difficult to define, because (i) C fluxes from plant vs. microbial activity are difficult to separate, and (ii) controlling variables are often intercorrelated. We investigated temporal and spatial determinants of soil respiration and whole-ecosystem respiration using nighttime exposure of static chambers to alkali absorption during 2 yr on a tallgrass prairie in northeastern Kansas. Soil respiration (mg CO2-C m−2 h−1) was positively related to soil organic C (SOC, kg m−2 0.1 m−1) through linear regression [ CO 2 - C = −44 + (40 SOC ) , r2 = 0.71] Temporal variations in respiration were related to soil temperature, water-filled pore space (WFPS), and a plant growth rate function, with a combined R 2 of 0.76 for soil respiration and of 0.84 for whole-ecosystem respiration. Temporal variograms suggested that both soil and whole-ecosystem respiration became increasingly dissimilar the longer the time between measurements up to 30 d, while dissimilarity in soil temperature and WFPS leveled between 10 and 20 d of separation. A plant growth rate function was an important variable that controlled whole-ecosystem respiration, as well as soil respiration. The ratio of soil respiration to whole-ecosystem respiration was ≈0.4 during maximum plant growth (July) and approached a value of 1 during minimal plant growth (November to March). We conclude that whole-ecosystem respiration is under similar environmental controls as soil respiration, the main variables being soil organic C, soil temperature, WFPS, and plant growth rate, which all control the supply of readily mineralizable substrates.
Keywords: tallgrass prairie

Expansion of woody plants in tallgrass prairie: a 15 year study of fire and fire-grazing interactions - J. M. Briggs; Alan K. Knapp; B. Brock (The American Midland Naturalist, 2002)
Temporal changes in the abundance of trees and a common shrub, Cornus drummondii, were quantified for 15 y (1981–1996) in seven tallgrass prairie watersheds in Northeast Kansas. Woody plant responses to different fire frequencies and grazing were assessed with a data set that included >9000 individuals. Although 15 tree species were included in this data set, only four (Juniperus virginiana, Celtis occidentalis, Gleditsia triacanthos and Ulmus americana) were sufficiently abundant for detailed analysis. Over the 15 y study tree density increased by two- to 10-fold, except in watersheds burned annually where woody plants remained almost completely absent throughout the study. Although increased woody plant abundance was expected in watersheds protected from fire, tree and shrub density also increased substantially in watersheds burned only once in 4 y. An intermediate fire frequency (burned every 3–5 y) actually increased the abundance of C. drummondii relative to a low fire frequency (burned only once in 15 y). Moreover, a severe wildfire in 1991, which affected all watersheds, did not markedly reverse this pattern of increase in abundance in most tree species. Four years after the addition of native herbivores (Bos bison) to three of the long-term experimental watersheds (infrequently and annually burned) woody plant abundance increased by four- and 40-fold, respectively, compared to corresponding ungrazed watersheds. Thus, the presence of large ungulate grazers in tallgrass prairie resulted in a significant increase in woody plant abundance. The most parsimonious explanation for this phenomenon is that fire intensity and extent was reduced in grazed grasslands allowing greater success of woody species.
Keywords: tallgrass prairie; woody plant

Fire behaviour as a key factor in the fire ecology of African grasslands and savannas - Trollope, W.S.W.; Trollope, L.A.; D.C. Hartnett (Forest Fire Research and Wildland Fire, 2002)
The effect of fire on natural ecosystems involves the response of living organisms to the release of heat energy through the combustion of plant material. The manner in which and the factors that influence the release of heat energy, involves the study of fire behaviour. In Africa there is a serious deficiency of knowledge concerning the behaviour of fires and this is particularly applicable to the savanna and grassland areas of the continent. Virtually no attempt has been made to quantify the dynamics of the release of heat energy during a fire and the subsequent response of plants to it. The determination of such relationships helps explain many of the apparently inexplicable effects of fire that are often cited in the literature. Research on the effects of fire has been conducted throughout the grassland and savanna areas of Africa, particularly in southern Africa, since the early period of the 20th century. An interesting feature about these early investigations and subsequent research up until 1971, was that it focused on the effects of season and frequency of burning on the forage production potential of the grass sward and the ratio of bush to grass in savanna areas However, in 1971 a conference was convened in the United States of America in Florida, by the Tall Timbers Research Station on the theme of "Fire in Africa". The major benefit that accrued from this conference was the realization that in Africa the study of fire behaviour and its effects on the ecosystem, as described by type and intensity of fire, had been largely ignored in all the fire research that had been conducted up until that time. As a consequence a research program was initiated in South Africa and later extended to East Africa, to characterise the behaviour of fires burning in savanna and grassland vegetation and determine the effect of type and intensity of fire on the vegetation. The overall effect of type of fire is that surface head fires and crown fires have the least effect on grasses and have the potential to have the greatest effect on trees. This is because the heat is released above ground level away from the growing points of the grasses and closest to the growing points of the trees. Conversely, surface back fires have the opposite effect on grass and tree vegetation. This is because the heat is released close to ground level where the growing points of grasses are located and away from the growing points of the trees in the canopy. The overall effect of fire intensity is that grasses are generally not sensitive to increasing fire intensities because their growing points are located close to ground level away from the release of heat energy. Conversely trees are sensitive to increasing fire intensities because their growing points are generally exposed to the release of heat energy in the canopy of the trees. These effects explain why intense fires favour the development of grassland and open savannas and vice versa. The behaviour of surface head and back fires is currently being compared in southern African savannas and tall grass prairies in North America and results indicate that fires burning in grass dominated communities behave similarly and may therefore have similar effects on grass and tree vegetation globally.
Keywords: African grasslands; American prairies; fire; Savannas

First Kansas record for Tetraopes texanus (Coleoptera: Cerambycidae) - Huber, R.L.; Wright, V.F. (Journal of the Kansas Entomological Society, 2002)
A red long-horned beetle was collected from the common milkweed Asclepias syriaca during an arthropod survey conducted on 26 June 1999, at Konza Prairie Biological Station in Riley County, Kansas, USA. Several weeks later, on 17 July 1999, another specimen was taken at the same location, west of the historical Hokanson Homestead, again from A. syriaca. Morphological analysis identified the species as Tetraopes texanus, which was distinguished from other related species based on the distinctive shape of the eleventh (distal) antennomere and the fringes of very long setae at the apices of the antennomeres. This is the first record of T. texanus from Kansas.

Genetic diversity and competitive abilities of Dalea purpurea (Fabaceae) from remnant and restored grasslands - Gustafson, D.J.; D.J. Gibson; Nickert, D.L. (International Journal of Plant Science, 2002)
Allozyme and randomly amplified polymorphic DNA (RAPD) analyses were used to characterize the genetic relationships of Dalea purpurea from remnant and restored Illinois tallgrass prairies and a large remnant tallgrass prairie in Kansas. The remnant Illinois populations were less genetically diverse than the restored Illinois populations and the Kansas population. These restored Illinois populations were established with at least two seed sources that were locally collected. There was little population divergence ( ), which is consistent with other perennial forbs, while the genetic relationships among populations reflected geographic proximity. In a greenhouse competition experiment, differences in performance between seedlings was not related to the remnant or restored status of Illinois populations, but plants from Kansas were significantly smaller than Illinois plants. Genetic diversity and competitive ability were not associated with the size of the original source population. Our data indicate that using multiple local seed sources for restoration projects will maintain the local gene pool while enhancing the regional genetic diversity of this species.
Keywords: conservation genetics; local seed source; restoration ecology; tallgrass prairie

Impact of global warming on ecosystems: a case study of biomass in Konza Prairie Biological Station - Gao, J.; Harrington, J. (2002)

The influence of ammonium, nitrate, and dissolved oxygen concentration on uptake, nitrification, and denitrification rates associated with prairie stream substrata - Kemp, M.J.; W. K. Dodds (Limnology and Oceanography, 2002)
Substrata samples were collected from Kings Creek on Konza Prairie Biological Station (Manhattan, Kansas) and incubated with varying levels of ammonium (NH4+), nitrate (NO3−), and dissolved oxygen (O2) to examine the response of nitrogen (N) uptake and transformation rates. Substrata collected were fine benthic organic matter (FBOM), coarse benthic organic matter, filamentous green algae, bryophytes, suspended particulate organic matter, and epilithic diatoms. Nitrification and denitrification were estimated by use of the nitrapyrin and acetylene inhibition methods, respectively. Ammonium uptake demonstrated Michaelis-Menten kinetics, with the highest maximum rates (Vmax) associated with filamentous green algae (5.90 mg N gdm−1 d−1) and epilithic diatoms (4.96 mg N gdm−1 d−1). Nitrate uptake did not saturate at the highest NO3− addition (25 µg N L−1) above ambient when associated with FBOM. Overall, maximum uptake rates of NH4+ were 10-fold higher than for NO3−. Nitrification response to increasing NH4+ concentrations was highly variable, depending on the substrata type. Nitrification was lowest under low O2 conditions, being undetectable when NO3− was added but not when NH4+ was added. Denitrification increased linearly with NO3− concentration when associated with epilithic diatoms and FBOM but became saturated at ~20 µg N L−1 above ambient concentrations when associated with filamentous green algae. Samples purged with N2 gas had the highest rates of denitrification. We predicted stream ecosystem rates using equations derived from the experimental data and substrata mass estimates measured in the field. Substantial temporal variability was predicted in uptake (0–1,300 mg NH4+−N m−2 d−1; 0–5.2 mg NO3−−N m−2 d−1), nitrification (0–35 mg NH4+−N m−2 d−1), and denitrification (0–130 µg N2O-N m−2 d−1) as due to natural variation in water column NH4+, NO3−, and O2 concentrations.

The influence of canopy green vegetation fraction on spectral measurements over native tallgrass prairie - Rundquist, B.C. (Remote Sensing of the Environment, 2002)
Spectral vegetation indices (SVIs) calculated from remotely sensed data are routinely used to monitor spatial and temporal changes in vegetation biophysical characteristics. The most commonly used SVI, the Normalized Difference Vegetation Index (NDVI), has been criticized because of its sensitivity to atmospheric conditions and substrate reflectivity, as well as its insensitivity to increases in vegetation biomass past particular thresholds. Yet, the use of NDVI remains widespread and is attractive because of the ease with which it is calculated. This article examines the utility of NDVI for monitoring the biophysical characteristic of green vegetation fraction (GVF) in comparison to other SVIs suggested as improvements. Statistical relationships between spectral response, presented in the form of SVIs, and GVF of a native tallgrass prairie canopy are explored. Broadband spectra were gathered from close-range during the 1999 growing season at the Konza Prairie Biological Station (KPBS), located in the Flint Hills region of Kansas, USA. Through simple regression analyses, spectra were related to GVF estimates derived from digital color photographs. SVIs evaluated are the NDVI, the Soil Adjusted Vegetation Index (SAVI), and the square of scaled NDVI (N*2). Results show that NDVI and N*2 were statistically related to GVF (R2 for NDVI=.77, N*2=.78) throughout the growing season. The least-squares line defining the relationship between N*2 and GVF approximated a 1:1 line. For June sample dates, all three SVIs were significant statistical predictors of GVF (R2 for NDVI=.89, N*2=.91, SAVI=.89). Regression coefficients for late-season sample dates were weaker, yet still significant in statistical terms (R2 for NDVI=.70, N*2=.70). While encouraging, these results suggest that further analyses are required to determine the usefulness of SVIs calculated from broadband devices for estimation of GVF when leaf litter dominates the scene.
Keywords: Green vegetation fraction; Field spectroscopy; Tallgrass prairie

Influence of climate variability on plant production and N-mineralization in Central US grasslands - Barrett, J.E.; McCulley, R.L.; Lane, D.R.; Burke, I.C.; Lauenroth, W.K. (Journal of Vegetation Science, 2002)
We assessed the influence of annual and seasonal climate variability over soil organic matter (SOM), above-ground net primary production (ANPP) and in situ net nitrogen (N) mineralization in a regional field study across the International Geosphere Biosphere Programme (IGBP) North American mid-latitude transect (Koch et al. 1995). We hypothesized that while trends in SOM are strongly correlated with mean climatic parameters, ANPP and net N-mineralization are more strongly influenced by annual and seasonal climate because they are dynamic processes sensitive to short-term variation in temperature and water availability. Seasonal and monthly deviations from long-term climatic means, particularly precipitation, were greatest at the semi-arid end of the transect. ANPP is sensitive to this climatic variability, but is also strongly correlated with mean annual climate parameters. In situ net N-mineralization and nitrification were weakly influenced by soil water content and temperature during the incubation and were less sensitive to seasonal climatic variables than ANPP, probably because microbial transformations of N in the soil are mediated over even finer temporal scales. We found no relationship between ANPP and in situ net N-mineralization. These results suggests that methods used to estimate in situ net N-mineralization are inadequate to represent N-availability across gradients where microbial biomass, N-immobilization or competition among plants and microbes vary.
Keywords: Annual variation; ANPP; Central Grasslands region; Environmental gradient; IGBP Transect; Mineralization; Nitrogen flux; Seasonal variation

Life history, secondary production, and ecosystem significance of acridid grasshoppers in annually burned and unburned tallgrass prairie - Meyer, C.K.; M.R. Whiles; Charlton, R.E. (American Entomologist, 2002)
Keywords: tallgrass prairie

Long-term responses of the grassland co-dominants Andropogon gerardii and Sorghastrum nutans to changes in climate and management - Silletti, A.M.; Alan K. Knapp (Plant Ecology, 2002)
Understanding responses of both dominant and sub-dominant plant speciesto management regimes and climatic variables is a critical component ofunderstanding an ecosystem's potential response to local or regional changes insuch parameters. The dominant vegetation of much of the North Americantallgrassprairie is composed of C4 grasses. As the most abundant species,Andropogon gerardii has been well characterizedecologically. The second most abundant, co-dominant species,Sorghastrum nutans, has received less attention, mainlybecause it has been considered the “ecological equivalent” ofA. gerardii and is assumed to have responses similar tothose of A. gerardii. The objective of this study was toassess the validity of this assumption by examining long-term abundancepatternsand responses to climate, fire, and grazing for both species. Based on 15 years(1983–1997) of plant species composition and cover data collected atKonzaPrairie Biological Station in northeastern Kansas, USA, we were able to detectimportant differences between these two grasses. Regression analysis showedthatlong-term reductions in the cover of A. gerardii werecorrelated with decreasing summer maximum temperatures, whereas inter-annualvariations in the cover of S. nutans were related toannualprecipitation. Additionally, the cover of S. nutansincreased with increasing fire frequency, while the cover of A.gerardii was not significantly affected by fire frequency. Bisongrazing did not significantly affect the cover of either species studied. Themean cover of A. gerardii decreased significantly over the15 years, but only a slight change was noted in the cover of S.nutans. The decrease in A. gerardiicorrespondedto increased plant species diversity and evenness and has the potential toimpact the tallgrass prairie ecosystem from population through ecosystemlevels.The observed differences in these co-dominant species may prove important underclimate change scenarios predicted for the tallgrass prairie of North America.
Keywords: C4 grasses; Cover; diversity; Dominance; fire; prairie; tallgrass

Long-term variation in abundance of Elliot's short-tailed shrew (Blarina hylophaga) in tallgrass prairie - Matlack, R.S.; D.W. Kaufman; Kaufman, G.A. (Journal of Mammalogy, 2002)
Elliot's short-tailed shrews (Blarina hylophaga) were studied in tallgrass prairie at Konza Prairie Biological Station, Kansas. Based on sampling of 14 permanent traplines from autumn 1981 to spring 1999, relative abundance was high in autumn (X̄ = 2.5 ± 0.4 SE shrews/trapline) but very low in spring (<0.1 shrews/trapline). Interannual variability in abundance in autumn was large with a range 0.1–7.0 shrews/trapline. Relative abundance of shrews in autumn was correlated positively with precipitation, soil moisture, and depth of plant litter and correlated negatively with proportion of area burned and maximum temperature. Two variables, precipitation, and amount of litter, accounted for 87% of variation in abundance of shrews in autumn. Ambient moisture and a well-developed litter layer that ameliorates microclimatic extremes appear to be the most important factors influencing abundance of shrews in tallgrass prairie.
Keywords: abiotic factors; Blarina hylophaga; Elliot's short-tailed shrew; kansas; long-term study; population dynamics; tallgrass prairie

Macroinvertebrate assemblage structure across a tallgrass prairie stream landscape - Fritz, K.M.; W. K. Dodds (Archiv Fur Hydrobiologie, 2002)
Stream macroinvertebrates were collected from four intermittent tributaries and two perennial sites within the Kings Creek basin, Konza Prairie Biological Station (KPBS) near Manhattan, KS, USA. The objectives of this study were to assess the roles of disturbances (floods and drying) and refugia on benthic and colonization (drift and aerial) assemblage composition over two years among sites with contrasting hydrologic regimes. Benthic taxa richness and diversity at the perennial headwater site were significantly greater than richness and diversity at intermittent sites, whereas the downstream perennial site did not differ significantly from two of the intermittent sites. The larger magnitude of floods at the downstream perennial site resulted in greater losses in richness than at the upstream intermittent and perennial sites. Both classification and ordination revealed that benthic assemblage composition was more strongly correlated with time since last disturbance and season than with static hydrologic descriptors, microhabitat measures, or assemblage characteristics (richness or density). Richness of aerial colonization and drift samples collected at intermittent sites was greatest at the site with the nearest upstream perennial surface water. Because Kings Creek is a relatively pristine stream, these data may be useful as a baseline for comparison with future efforts for bioassessment of intermittent prairie streams.
Keywords: tallgrass prairie

Macroinvertebrate production and trophic structure in a tallgrass prairie headwater stream - Stagliano, D.M.; M.R. Whiles (Journal of the North American Benthological Society, 2002)
Research on North American prairie stream communities has lagged behind other regions. We examined the ecosystem significance of the macroinvertebrate community of riffle/run habitats in Kings Creek, a 2nd-order tallgrass prairie stream at Konza Prairie Biological Station (Kansas, USA), by estimating secondary production, benthic organic matter standing stocks, and resource consumption and egestion by functional groups. Annual mean standing stock macroinvertebrate biomass was 2.3 g ash-free dry mass (AFDM)/m2, annual production was 19.7 g AFDM m-2 y-1, and the annual community production/biomass (P/B) ratio was 8.6. Macroinvertebrate production was higher than published estimates for forested streams of similar size, but much lower than that of a Sonoran desert stream. Distribution of production among functional groups was 30% for collector-gatherers, 9% for collector-filterers, 20% for scrapers, 23% for shredders, and 18% for predators, resembling estimates from some forested streams with the exception of higher scraper production. Although detritivorous groups were productive in this prairie stream, they appeared food limited. Consumption estimates indicated shredders and collector-gatherers annually ingested ∼80% and ∼240% of coarse particulate organic matter (CPOM) and fine particulate organic matter (FPOM) standing stocks, respectively. Thus, re-ingestion and/or diet shifts may be common, particularly among collector-gatherers, and the FPOM pool must turn over rapidly. Invertebrate predators also consumed a sizeable portion (∼52%) of prey, whereas scrapers (∼21%) and filterers (<1%) consumed relatively small portions of their respective resources, suggesting top-down influences on these groups. This study indicates that, during a period of relatively stable flow in this prairie stream, macroinvertebrate production and functional structure were roughly intermediate between North American forested and desert systems. Our results underscore the value of secondary production estimates for examining invertebrate communities in an ecosystem context
Keywords: Aquatic macroinvertebrates; Energy flow; Food web; Konza Prairie Biological Station; organic matter; Prairie stream; secondary production; Trophic structure

Measurement and modeling of soil CO2 flux in a temperate grassland under mowed and burned regimes - D. Bremer; J.M. Ham (Ecological Applications, 2002)
Soil-surface CO2 flux (Rs), which is a large component of the carbon (C) budgets in grasslands, usually is measured infrequently using static or dynamic chambers. Therefore, to quantify annual C budgets, estimates of Rs are required during days when no direct measurements of Rs are available. Other researchers have developed empirical models based on soil temperature, soil volumetric water content (θv), and leaf area index (LAI) that have provided reasonable estimates of Rs during the growing season in ungrazed tallgrass prairie. However, the effects of mowing and grazing, which are common in grasslands, on predictions of Rs from those models are uncertain. Predictions of Rs during dormancy (postsenescence to spring fire) also are uncertain. Data from a year-long mowing study, which simulated grazing, were used to refit these models. Output from the models then was compared to independent data collected from nearby prairie sites. Results showed that LAI must be included to accurately estimate Rs in mowed prairie ecosystems. When LAI was not included in the model, predicted daily Rs following mowing was nearly four times greater than measured Rs, and cumulative, annual Rs was overestimated by 95–102%. When LAI was included in the model, predictions of Rs were comparable to measured Rs in the mowing study. Annual estimates of cumulative Rs ranged from 3.93 to 4.92 kg CO2/m2. When comparing the model with independent chamber data from nearby sites, cumulative Rs during those studies was within ±9% of cumulative estimates calculated from measured Rs. The model overestimated daily Rs during a dry period, suggesting a nonlinear response of Rs to soil water content; soil water matric potential may be more appropriate than θv for modeling Rs. Data suggest that Rs, in addition to being dependent on soil temperature and soil water content, is dependent on the photosynthetic capacity of the canopy and the subsequent translocation of C belowground.

N uptake as a function of concentration in streams - W. K. Dodds; López, A.J.; W.B. Bowden; Gregory, S.; Grimm, N.B.; Hamilton, S.K.; Hershey, A.E.; Marti, E.; W.B. McDowell; Meyer, J.L.; Morrall, D.; Mulholland, P.J.; et al. (Journal of the North American Benthological Society, 2002)
Detailed studies of stream N uptake were conducted in a prairie reach and gallery forest reach of Kings Creek on the Konza Prairie Biological Station. Nutrient uptake rates were measured with multiple short-term enrichments of NO3− and NH4+ at constant addition rates in the spring and summer of 1998. NH4+ uptake was also measured with 15N-NH4+ tracer additions and short-term unlabeled NH4+ additions at 12 stream sites across North America. Concurrent addition of a conservative tracer was used to account for dilution in all experiments. NH4+ uptake rate per unit area (Ut) was positively correlated to nutrient concentration across all sites (r2 = 0.41, log–log relationship). Relationships between concentration and Ut were used to determine whether the uptake was nonlinear (i.e., kinetic uptake primarily limited by the biotic capacity of microorganisms to accumulate nutrients) or linear (e.g., limited by mass transport into stream biofilms). In all systems, Ut was lower at ambient concentrations than at elevated concentrations. Extrapolation from uptake measured from a series of increasing enrichments could be used to estimate ambient Ut. Linear extrapolation of Ut assuming the relationship passes through the origin and rates measured at 1 elevated nutrient concentration underestimated ambient Ut by ∼3-fold. Uptake rates were saturated under some but not all conditions of enrichment; in some cases there was no saturation up to 50 μmol/L. The absolute concentration at which Ut was saturated in Kings Creek varied among reaches and nutrients. Uptake rates of NH4+ at ambient concentrations in all streams were higher than would be expected, assuming Ut does not saturate with increasing concentrations. At ambient nutrient concentrations in unpolluted streams, Ut is probably limited to some degree by the kinetic uptake capacity of stream biota. Mass transfer velocity from the water column is generally greater than would be expected given typical diffusion rates, underscoring the importance of advective transport. Given the short-term spikes in nutrient concentrations that can occur in streams (e.g., in response to storm events), Ut may not saturate, even at high concentrations.
Keywords: advective transport; ammonium; areal uptake; benthos; kinetics; mass transport; Nitrate; nitrogen

Nitrogen and phosphorus relationships to benthic algal biomass in temperate streams - W. K. Dodds; Smith, V.H.; Lohman, K. (Canadian Journal of Fisheries and Aquatic Science, 2002)
Knowledge of factors limiting benthic algal (periphyton) biomass is central to understanding energy flow in stream ecosystems and stream eutrophication. We used several data sets to determine how water column nutrients and nonnutrient factors are linked to periphytic biomass and if the ecoregion concept is applicable to nutrientperiphyton relationships. Literature values for seasonal means of biomass of periphyton, nutrient concentrations, and other stream characteristics were collected for almost 300 sampling periods from temperate streams. Data for benthic chlorophyll and nutrient concentrations from a subset of 620 stations in the United States National Stream Water-Quality Monitoring Networks were also analyzed. The greatest portion of variance in models for the mean and maximum biomass of benthic stream algae (about 40%) was explained by concentrations of total N and P. Breakpoint regression and a two-dimensional KolmogorovSmirnov statistical technique established significant breakpoints of about 30 µg total P·L1 and 40 µg total N·L1, above which mean chlorophyll values were substantially higher. Ecoregion effects on nutrientchlorophyll relationships were weak. Ecoregion effects were cross-correlated with anthropogenic effects such as percent urban and cropland area in the watershed and population density. Thus, caution is necessary to separate anthropogenic effects from natural variation at the ecoregion level.

Phrynosoma cornutum (Texas horned lizard) reproduction - Owens, A.; Trager, M.; Horne, E. (Herpetological Review, 2002)

Rainfall variability, carbon cycling and plant species diversity in a mesic grassland - Alan K. Knapp; Fay, P.A.; John M. Blair; Scott. L. Collins; M.D. Smith; Carlisle, J.D.; Harper, C.W.; Danner, B.T.; Lett, M.S.; McCarron, J.K. (Science, 2002)
Ecosystem responses to increased variability in rainfall, a prediction of general circulation models, were assessed in native grassland by reducing storm frequency and increasing rainfall quantity per storm during a 4-year experiment. More extreme rainfall patterns, without concurrent changes in total rainfall quantity, increased temporal variability in soil moisture and plant species diversity. However, carbon cycling processes such as soil CO2 flux, CO2 uptake by the dominant grasses, and aboveground net primary productivity (ANPP) were reduced, and ANPP was more responsive to soil moisture variability than to mean soil water content. Our results show that projected increases in rainfall variability can rapidly alter key carbon cycling processes and plant community composition, independent of changes in total precipitation.

Recovery of three fish species to flood and seasonal drying in a tallgrass prairie stream - Fritz, K.M.; Tripe, J.A.; Guy, C.S. (Transactions of the Kansas Academy of Science, 2002)
The recovery of three fish species following a catastrophic flood (>50 y recurrence interval) and seasonal drying were studied in Kings Creek basin at the Konza Prairie Biological Station in northeastern Kansas. Fish collected from three tallgrass prairie headwater springs were marked and recaptured to determine if headwater springs were a source of fish recolonizing intermittent sections downstream and to estimate population sizes in the headwater springs. Three fish species (Campostoma anomalum, Phoxinus erythrogaster, and Etheostoma spectabile) were collected. Catch rates and population estimates of fish nine days post-flood were approximately half of the values obtained during subsequent sampling periods. Recolonization of an intermittent section was primarily by age-0 fish that seemingly were displaced downstream by flood events. The distribution of fish within the upper subbasins of the South Branch of Kings Creek was limited to perennial spring-fed reaches. The short duration of continuous flow and regular drying in these tributaries might limit the dispersal of individuals between populations in this landscape.
Keywords: tallgrass prairie

Relationships between stream size, suspended particles, and filter-feeding macroinvertebrates in a Great Plains drainage network - M.R. Whiles; W. K. Dodds (Journal of Environmental Quality, 2002)
Suspended fine particles (seston) are an important component of energy and nutrient cycling in streams, but they can also be pollutants. We examined seston dynamics and filter-feeding macroinvertebrate communities in sites representing headwaters to large rivers in the Kansas River drainage, northeastern KS. Seston samples were collected at least seasonally during low to moderate flows for one year beginning in the summer of 1999, and quality was assessed by determining organic content and C to N ratio. A rapid bioassessment approach was used to examine filter-feeders. Relationships between stream size and seston concentrations were markedly influenced by anthropogenic activities. There was no relationship between total seston concentration and stream size across all sites (r = 0.14, p > 0.05), but a significant, positive relationship was evident when impounded and suburban sites were excluded (r = 0.73, p < 0.01); this same trend was evident for organic and inorganic components. Seasonal patterns of C to N ratio were evident, with generally lower values during winter and highest values in summer. However, seasonal patterns were dampened in suburban sites and virtually absent below impoundments. Filter-feeder richness was correlated with average organic seston concentrations (r = 0.8, p < 0.01), but this relationship was also obscured by impoundments and suburban development. In particular, impoundments had a dramatic, negative effect on richness. Abundance of most hydropsychid caddisfly taxa was positively correlated with organic seston concentration. Results indicate there are significant patterns regarding seston, filter-feeders, and stream size in this Great Plains river system, but patterns are strongly influenced by human activities. These relationships are relevant to management issues regarding suspended particles and the potential development of bioassessment techniques.

The role of mycorrhizas in plant community structure and dynamics: lessons from grasslands - D.C. Hartnett; G.T. Wilson (Plant and Soil, 2002)
Research on the mycorrhizal associations over the past several decades has yielded increased understanding and appreciation of the important role of this symbiosis in the functioning and performance of plants in a wide array of terrestrial ecosystems. We now understand that the role of mycorrhizal fungi extends beyond the symbiotic acquisition of phosphorus for the host plant and reciprocal carbon provision from the host to fungus. Additional effects of mycorrhizal fungi on the functioning of their host plants including increased disease resistance, improved water relations, acquisition of other soil nutrients, and alterations in other soil physico-chemical properties have been documented. Other aspects of the ecology of mycorrhizas, including variation in the costs and benefits of carbon and nutrient exchange, the ecological significance of mycelial networks, the role of mycorrhizal symbiosis in multi-species interactions, and the extent and consequences of host-specificity in these associations have also recently been explored.

Variation in grazing tolerance among three tallgrass prairie plant species - Damhoureyeh, S.A.; D.C. Hartnett (American Journal of Botany, 2002)
Three tallgrass prairie plant species, two common perennial forbs (Artemisia ludoviciana and Aster ericoides [Asteraceae]) and a dominant C4 perennial grass (Sorghastrum nutans) were studied under field and greenhouse conditions to evaluate interspecific variation in grazing tolerance (compensatory growth capacity). Adaptation to ungulate grazing was also assessed by comparing defoliation responses of plants from populations with a 25-yr history of no grazing or moderate ungulate grazing. Under field conditions, all three species showed significant reductions in shoot relative growth rates (RGR), biomass, and reproduction with defoliation. In the two forbs, clipping resulted in negative shoot RGR and reductions in both number and length of shoot branches per ramet. Sorghastrum nutans maintained positive RGR under defoliation due to a compensatory increase in leaf production. Defoliation reduced rhizome production in A. ericoides and S. nutans, but not in A. ludoviciana. Clipping significantly reduced sexual reproductive allocation in all three species, although S. nutans showed a smaller reduction than the forbs. All three species showed similar responses to defoliation in burned and unburned sites. Under greenhouse conditions, a similar clipping regimen resulted in smaller reductions in growth and reproduction than those observed in the field. For all three species, the grazing tolerance indices calculated under natural field conditions were significantly lower than those estimated from greenhouse-grown plants, and the interspecific patterns of grazing tolerance were different. Aster ericoides exhibited the highest overall defoliation tolerance under greenhouse conditions, followed by S. nutans. Artemisia ludoviciana, the only study species that is typically not grazed by ungulates in the field, showed the lowest grazing tolerance. In the field experiment S. nutans showed the highest grazing tolerance and the two forbs had similar low tolerance indices. These patterns indicate that, despite high compensatory growth potential, limited resource availability and competition in the field significantly reduce the degree of compensation and alter interspecific differences in grazing tolerance among prairie plants. In all three species, defoliation suppressed sexual reproduction more than growth or vegetative reproduction. Significant interactions between plant responses to defoliation and site of origin (historically grazed or ungrazed sites) for some response variables (root/shoot ratios, rhizome bud initiation, and reproductive allocation) indicated some degree of population differentiation and genetic adaptation in response to a relatively short history of ungulate grazing pressure. The results of this study indicate that patterns of grazing tolerance in tallgrass prairie are both genetically based and also environmentally dependent.
Keywords: Ambrosia ludoviciana; Aster ericoides; compensatory growth; forbs; Grasses; grazing tolerance; Sorghastrum nutans; tallgrass prairie

Vascular plants of Konza Prairie Biological Station: An annotated checklist of species in a Kansas tallgrass prairie - Towne, E.G. (Sida, 2002)
The native and naturalized vascular plants of Konza Prairie Biological Station, a 3487-ha tallgrass prairie research site located in the Flint Hills of northeastern Kansas, are listed along with their primary habitat, relative abundance, flowering period, and life span. After more than 25 years of collections, the known vascular flora of Konza Prairie consists of 576 species, representing 336 genera and 96 families. Families with the most species are Poaceae (84), Asteraceae (79), Fabaceae (49), and Cyperaceae (33). Non-native species (n = 96) comprise 16.7% of the total flora. When categorized by life span, 64.6% of all species are perennials, 31.3% are annuals, and 4.2% are biennials. Species that are characteristically associated with a prairie habitat comprise 40.6% of the flora, followed by species in disturbed (22.4%), woodland (22.2%), and wetland (14.8%) habitats. In the prairie habitat, 16.2% of the species are grasses and 76.9% are herbaceous forbs. The C⁴ photosynthetic pathway occurs in 59.5% of all grass species and in 70.8% of the annual grasses. The diversified habitats created by management and research activities on Konza Prairie provide a flora richness that is likely greater than that of any other area of comparable size in the Great Plains region.
Keywords: Biodiversity; prairie flora; Species richness; tallgrass prairie; vascular plant survey

Water velocity attenuation by stream periphyton and macrophytes in relation to growth form and architecture - W. K. Dodds; Biggs, B.J.F. (Journal of the North American Benthological Society, 2002)
Periphyton and macrophytes alter water velocity in streams, influencing movement of solutes and providing microhabitat for other organisms. How assemblages with different growth form and architecture influence water velocity attenuation across mm to dm scales is not well described. A thermistor microprobe was used to measure water velocity through 4 morphologically distinct stream periphyton assemblages and 4 distinct stream macrophyte assemblages in flumes. All assemblages resulted in an exponential decay in velocity with depth. A dense assemblage of diatoms (primarily Cymbella) attenuated velocity more than filamentous green algae, filamentous green algae with interspersed diatoms, or a red alga (ANOVA, p < 0.05). External water velocity had no significant influence on the coefficient of attenuation in a filamentous green alga (ANOVA, p = 0.76). Macrophytes also attenuated water velocity, but attenuation was more variable and, in all cases, attenuation coefficients were less for macrophytes than for periphyton. A model unifying attenuation by periphyton and macrophytes was developed using biomass density (g ash-free dry mass/m3) as the independent variable and it explained 80% of the variation in attenuation. The relative variance of attenuation coefficients increased sharply as Reynolds number increased above ∼500 to 700, suggesting that variance in water velocity was dependent upon the spatial scale of the primary producer through which water is flowing, and that the distinction btween periphyton and macrophytes may have real physical ramifications.
Keywords: Algae; Current; Flow; Hydrodynamics; microphytobenthos; Primary producers; Submerged plants

White-tailed deer browsing on six shrub species of tallgrass prairie - Van Der Hoek, D.J.; Alan K. Knapp; J. M. Briggs; Bokdam, J. (Great Plains Research, 2002)
Native grasses and forbs were once dominant in tallgrass prairies, but nonnative plants have largely replaced natives in most grassland of Illinois. Ample evidence indicates that white-tailed deer (Odocoileus virginianus) have a strong impact on native forests and prairie, but we know little about their impact on nonnative grasslands. This study tested the hypothesis that foraging by deer on native forbs and woody plants increases the dominance of introduced grasses as succession proceeds in old fields of central Illinois. We tested that hypothesis using fencing that excluded deer, but not other herbivores, from replicated plots in three old fields at different successional stages. The composition of the plant community changed rapidly in early succession and showed relatively little effect of deer, other than slowing the invasion by woody plants. In mid- and late successional fields, however, fenced plots had higher relative abundance of native forbs, particularly goldenrod (Solidago spp.), and lower relative abundance of introduced perennial grasses than did control plots. Thus, deer facilitated introduced perennial grasses and inhibited native forbs and woody plants in old fields, thereby delaying succession to deciduous forest.
Keywords: tallgrass prairie

Alterations in carbon and nitrogen cycling in irrigated tallgrass prairie soil - Williams, M.A. (Kansas State University, 2001)
Keywords: tallgrass prairie

Analytical survey of the braconid wasp fauna (Hymenoptera: Braconidae) on six Midwestern U.S. tallgrass prairies - Whitfield, J.B.; Lewis, C.N. (Annals of the Entomological Society of America, 2001)
A survey of the braconid wasps on midwestern United States tallgrass prairies was conducted using malaise trapping on six sites forming an east-west transect through the prairie zone in Kansas, Missouri, and Illinois. A total of 924 specimens, representing 184 species, was recovered. Statistical analyses indicated that the asymptote of actual species richness had not yet been approached using this sampling regime. Nevertheless, this is the most complete survey yet available of prairie braconid wasps. Patterns of distinctness of the prairie fauna relative to that of other nearby plant communities are beginning to emerge.
Keywords: Biodiversity; Braconidaek; Grasslands; parasitoids; tallgrass prairies

Aquatic invertebrate and fish communities of tallgrass prairie headwater streams: Bioindicators, secondary production and bioenergetics - Stagliano, D.M. (Kansas State University, 2001)
Keywords: tallgrass prairie

Assessing changes in biomass, productivity, and C and N stores following Juniperus virginiana forest expansion into tallgrass prairie - Norris, M.D.; John M. Blair; Johnson, L.C.; McKane, R.B. (Canadian Journal of Forest Research, 2001)
An increase in woody plant abundance in regions historically dominated by grasses is a recent land cover change in grasslands worldwide. In tallgrass prairies of North America, this increase in woody plant cover includes the development of dense stands of eastern redcedar (Juniperus virginiana L.). To evaluate the consequences of this ongoing land cover change for ecosystem functioning, we developed allometric equations, using data from Kansas and Oklahoma, to estimate aboveground biomass and productivity in closed-canopy redcedar stands. We then applied these equations to three closed-canopy redcedar stands, 3580 years old, which developed on sites formerly dominated by tallgrass prairie in eastern Kansas. Aboveground plant biomass for these redcedar-dominated sites ranged from 114 100 kg/ha for the youngest stand to 210 700 kg/ha for the oldest. Annual aboveground net primary productivity (ANPP) ranged from 7250 to 10 440 kg·ha1·year1 for the oldest and younger redcedar stands, respectively. Estimates of ANPP in comparable tallgrass prairie sites in this region average 3690 kg·ha1·year1 indicating a large increase in C uptake and aboveground storage as a result of the change from prairie to redcedar forests. Therefore, the widespread occurrence of redcedars across the woodlandprairie ecotone suggests that this land-cover change may have important consequences for regional net C storage.
Keywords: tallgrass prairie

Avian response to golf course construction, hiking trails, and roadways in grasslands - Bye, S. (Kansas State University, 2001)

Below-ground carbon and nitrogen accumulation in perennial grasses: A comparison of caespitose and rhizomatous growth forms - Derner, J.D.; Briske, D.D. (Plant and Soil, 2001)
An experiment was conducted to compare below-ground soil organic carbon and total nitrogen accumulation between caespitose and rhizomatous perennial grasses in long-term (<25 yrs) grazed and ungrazed sites in semi-arid and mesic communities in the North American Great Plains. Development of greater nutrient pools beneath than between clones occurred at minimal clone basal areas (<60 cm2) for both caespitose species. Caespitose grasses accumulated substantially greater pools of carbon (20–200 fold) and nitrogen (50–500 fold) in soils to a depth of 10 cm beneath clones than rhizomatous grasses accumulated in rhizomes in both communities. Carbon and nitrogen pools in soils beneath caespitose clones exceeded combined (soil + rhizome) pools for rhizomatous grasses for a majority of the clone basal areas (>90 cm2) in the mesic community. In contrast, both pool sizes were smaller beneath the caespitose grass at all clone basal areas than the combined pools for the rhizomatous grass in the semi-arid community. The occurrence of larger soil nutrient pools beneath the rhizomatous species in the semi-arid community was largely a consequence of niche separation for microsites characterized by soils with higher nutrient concentrations, rather than plant-induced increases in nutrient concentrations. Although nutrient islands do not occur beneath rhizomatous grasses, their distribution in the semi-arid community was restricted to microsites characterized by soils with higher SOC and N concentrations. A greater efficiency of nutrient accumulation per unit rhizome mass and the maintenance of rhizome nutrient pools of similar magnitude to those of the rhizomatous grass in the mesic community may also contribute to the distribution of rhizomatous grasses in semi-arid communities. The existence of nutrient islands beneath a wide range of clone sizes in both mesic and semi-arid communities provides circumstantial evidence to suggest that nutrient islands beneath caespitose grasses may contribute to clone fitness in this growth form.
Keywords: Grazing; islands of fertility; nutrient accumulation; nutrient islands; shortgrass prairie; tallgrass prairie

C3 woody plant expansion in a C4 grassland: are grasses and shrubs functionally distinct? - McCarron, J.K.; Alan K. Knapp (American Journal of Botany, 2001)
The expansion of C3 shrubs into C4-dominated tallgrass prairies represents a fundamental shift in growth-form dominance accompanied by changes in resource acquisition and use. We assessed these changes by comparing the ecophysiological traits of the dominant C4 grass Andropogon gerardii, with traits of three C3 invasive shrub species, Cornus drummondii, Prunus americana, and Rhus glabra. We tested the hypothesis that ecophysiological traits of the shrubs would be similar within this growth form but distinct from grasses and that these species would conform to the two-layer soil water model. Photosynthetic rates in R. glabra were similar to A. gerardii and higher than in the other two shrubs, while water use efficiency was markedly greater in A. gerardii. Among all species, midday xylem pressure potentials (XPP) were distinctly lower (70%) for P. americana, but were similar among the other species. Predawn XPP was related to soil water at shallow depths for A. gerardii (r2 = 0.59) and P. americana (r2 = 0.62), and to deeper soil moisture for R. glabra (r2 = 0.63); there was no relationship for C. drummondii at any soil depth. Thus, a simple two-layer soil water model for partitioning shrub/grass resource acquisition was not appropriate for this grassland. We conclude that these shrubs could not be considered functional equivalents from an ecophysiological perspective, nor were they, as a group, distinct from A. gerardii in resource acquisition and use

Carbon and water relations of juvenile Quercus species in tallgrass prairie - Fay, P.A.; Carlisle, J.D.; Danner, B.T.; Lett, M.S.; McCarron, J.K.; Stewart, C.; Alan K. Knapp; John M. Blair; Scott. L. Collins (Journal of Vegetation Science, 2001)
In ecosystems where environments are extreme, such as deserts, adult plant species may facilitate the establishment and growth of seedlings and juveniles. Because high temperatures and evaporative demand characterize tall-grass prairies of the central United States (relative to forests), we predicted that the grassland-forest ecotone, by minimizing temperature extremes and moderating water stress, may function to facilitate the expansion of Quercus species into undisturbed tall-grass prairie. We assessed the carbon and water relations of juvenile Quercus macrocarpa and Q. muhlenbergii, the dominant tree species in gallery forests of northeast Kansas, in ecotone and prairie sites. To evaluate the potentially competitive effects of neighboring herbaceous biomass on these oaks, juveniles (< 0.5 m tall) of both species also were subjected to either: (1) removal of surrounding above-ground herbaceous biomass, or (2) control (prairie community intact) treatments. Herbaceous biomass removal had no significant effect on gas exchange or water relations in these oak species in either the prairie or the ecotone environment. Although the ecotone did alleviate some environmental extremes, photosynthetic rates and stomatal conductance were ca. 20 % higher (p < 0.05) in both oaks in prairie sites vs. the ecotone. Moreover, although leaf temperatures on average were higher in oaks in the prairie, high leaf temperatures in the ecotone had a greater negative effect on photosynthesis. These data suggest that the grassland-forest ecotone did not facilitate the growth of Quercus juveniles expanding into this grassland. Moreover, the carbon and water relations of juvenile oaks in the prairie appeared to be unaffected by the presence of the dominant C4 grasses.
Keywords: Ecotone; Facilitation; forest expansion; Quercus; tallgrass prairie

Centimeter-scale patterns of oxygen concentrations related to nitrification in prairie stream substrate - Kemp, M.J.; W. K. Dodds (Journal of the North American Benthological Society, 2001)
Dissolved oxygen (O2) was measured with microelectrodes in shallow subsurface microsites in a prairie stream and related to rates of nitrification determined in the laboratory using the nitrapyrin method. Substrata sampled included diatom mats, leaves and wood (coarse benthic organic matter, CBOM), filamentous green algae, bryophytes, and fine benthic organic matter (FBOM). Significant differences in O2 concentrations were found among the substrata, with anoxic zones occurring primarily in FBOM from deep pool sediments and CBOM from litter accumulations. Filamentous green algae and bryophytes had average O2 concentrations near saturation and intermediate rates of nitrification. Diatom mats had the highest concentrations of O2 (up to several times saturation) and the highest rates of nitrification. In the summer, O2 concentrations were above saturation in epilithon and filamentous green algal mats. Nitrification rates were highest in epilithon and filamentous green algae samples taken in the spring and autumn. A significant positive relationship between nitrification rates and O2 concentration was observed in all seasons except summer. These data suggest that O2 concentration could control nitrification in prairie streams.
Keywords: Algae; microelectrodes; N cycling; nitrification; O2 concentration; streams; tallgrass prairie

Changes in ecosystem function and effects of environmental complexity on foristic diversity during tallgrass prairie restoration - S.G. Baer (Kansas State University, 2001)
Keywords: tallgrass prairie

Changes in soil carbon dynamics during juniper expansion into tallgrass prairie - Smith, D.L. (Kansas State University, 2001)
Keywords: tallgrass prairie

A comparison of the trophic ecology of crayfish (Orconectes nais (Faxon) and Orconectes neglectus (Faxon)) and central stonerollers (Compostoma anomalum (Rafinesque)): omnivory in a tallgrass prairie stream - Evans-White, M.A.; W. K. Dodds; Gray, L.; Fritz, K.M. (Hydrobiologia, 2001)
Omnivorous fish, such as the central stoneroller minnow (Campostoma anomalum(Rafinesque)), and crayfish often play important roles in the trophic dynamics of streams. The trophic role of these two omnivores has not been compared within a system even though they both consume algae, detritus and invertebrates and often co-occur in streams in the Midwestern United States. Natural abundance of 15N and 13C isotopes and a whole stream 15N-labeled ammonium chloride release were used to compare the trophic ecology of the central stoneroller minnow (Campostoma anomalum (Rafinesque)) and two species of crayfish (Orconectes neglectus (Faxon) and Orconectes nais (Faxon)) in a tallgrass prairie stream. The δ15N and δ13C values of Orconectes spp. were more similar to coarse benthic organic matter (CBOM) and filamentous green algae than to invertebrates, fine benthic organic matter (FBOM), and periphyton. Values for δ15N and δ13C in C. anomalum were more similar to grazer and collector invertebrates and filamentous green algae than to FBOM and periphyton. Results from a 15N tracer release also indicated a portion of algae and/or invertebrates were a component of nitrogen assimilated in Orconectes spp. and C. anomalum diets. Gut contents of C. anomalum were also analyzed. In contrast to stable isotope data, amorphous detritus was a significant component of C. anomalum guts, followed by diatoms and filamentous green algae. A significant percentage of invertebrate material was found in C. anomalum guts sampled in the spring. Experiments were conducted in artificial streams to determine if Orconectes spp. and C. anomalum could reduce epilithic algal biomass in small streams. Algal biomass on clay tile substrata was decreased relative to controls in artificial stream channels containing O. neglectus (3.4 fold, p=0.0002), C. anomalum (2.1 fold, p=0.0012), and both species combined (3.0 fold, p=0.0003). Results indicate that Orconectes spp. are functioning more as algal and detrital processors than as predators in Kings Creek. Isotope and gut content data show that C. anomalum includes invertebrates as well as algae and detritus in its diet. Both species have the potential to affect algal biomass and are important omnivores in the stream food web.
Keywords: food webs; gut analysis; Herbivory; omnivory; Stable isotopes

Constraint to adaptive evolution in response to global warming - Etterson, J.R.; Shaw, R.G. (Science, 2001)
We characterized the genetic architecture of three populations of a native North American prairie plant in field conditions that simulate the warmer and more arid climates predicted by global climate models. Despite genetic variance for traits under selection, among-trait genetic correlations that are antagonistic to the direction of selection limit adaptive evolution within these populations. Predicted rates of evolutionary response are much slower than the predicted rate of climate change.

Control of nitrogen export from watersheds by headwater streams - Peterson, B.J.; Wollheim, W.M.; Mulholland, P.J.; Webster, J.R.; Meyer, J.L.; Tank, J.L.; Marti, E.; W.B. Bowden; Valett, H.M.; Hershey, A.E.; W.H. McDowell; W. K. Dodds; et al. (Science, 2001)
A comparative 15N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries. The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed from the water within a few tens to hundreds of meters. Nitrate was also removed from stream water but traveled a distance 5 to 10 times as long, on average, as ammonium. Despite low ammonium concentration in stream water, nitrification rates were high, indicating that small streams are potentially important sources of atmospheric nitrous oxide. During seasons of high biological activity, the reaches of headwater streams typically export downstream less than half of the input of dissolved inorganic nitrogen from their watersheds.

Determinants of C3 forb growth and production in a C4 dominated grassland - J. M. Briggs; Alan K. Knapp (Plant Ecology, 2001)
Forbs are the most abundant species within the vascular flora of tallgrass prairie and they make the greatest contribution to biodiversity of all growth forms. However, little is known about the factors that determine their productivity and growth rates. The objective of this study was to assess the controls of forb growth (absolute and relative) and production in tallgrass prairie from a long-term burning experiment at the Konza Prairie in NE Kansas. Over the 14-year study, forbs comprised 9% of the total biomass production on sites with a high fire frequency vs. 29% on the low fire frequency site, with gramminoids accounting for the remainder. Although interannual variations in peak biomass of the grasses was strongly correlated with environmental variables related to water availability, there were no similar relationships for forbs, suggesting that production of forbs and grasses responded to interannual variations in climate in different ways. Multivariate analysis of climatic controls on growth rates of grasses and forbs yielded similar results. Although forbs had low biomass and absolute growth per unit ground area in frequently burned prairie, their relative growth rates were highest in such sites. Thus, it appears that reduced growth rates of individual forbs per se do not limit forb success in annually burned prairie. Instead, direct negative effects of fire on forbs (increased mortality) may be responsible. Determinants of forb growth and productivity in unburned prairie remain unresolved.
Keywords: aboveground net primary production; Biodiversity; fire; forbs; Graminoids; Relative growth rates; tallgrass prairie

Different behavioral patterns of the earthworms Octolasion tyrtaeum and Diplocardia spp . in tallgrass prairie soils: potential influences on plant growth - Callaham, M.A. Jr.; John M. Blair; Hendrix, P.F. (Biology and Fertility of Soils, 2001)
This study addressed differences between Diplocardia spp. (a native North American earthworm) and Octolasion tyrtaeum (an introduced European species), with respect to behavior, influence on soil microbial biomass, and plant uptake of N in tallgrass prairie soils. We manipulated earthworms in PVC-encased soil cores (20 cm diameter) over a 45-day period under field conditions. Treatments included: (1) control with no earthworms, (2) Diplocardia spp. only, and (3) O. tyrtaeum only. Prior to addition of earthworms, seedlings of Andropogon gerardii (a dominant tallgrass) were established in each core, and a dilute solution of 13C-labeled glucose and 15N-labeled (NH4)2SO4 was added to the soil to facilitate examination of earthworm/microbe/plant interactions. We found that Diplocardia spp. were significantly more active than O. tyrtaeum, and quickly assimilated 13C and 15N from the tracer. Individuals of Diplocardia spp. were present at shallower soil depths than O. tyrtaeum throughout the study. Contrary to expectation, this greater activity of Diplocardia spp. did not result in increased plant productivity. Rather, the activity of Diplocardia spp. was associated with less plant growth and smaller amounts of N acquired by A. gerardii seedlings compared to controls or O. tyrtaeum treatments. We observed few significant influences of earthworm treatments on microbial biomass C or N pool sizes, but the microbial C/N ratio was consistently greater in the presence of Diplocardia spp. relative to O. tyrtaeum. Results of this study indicate that activity of earthworms may enhance competition for N between microbes and plants during the growing season in tallgrass prairie.
Keywords: grassland; Microbial biomass; nitrogen; Soil invertebrates; Stable isotopes

Ecological forecasts: an emerging imperative - Clark, J.S.; Carpenter, S.R.; Barber, M.; Scott. L. Collins; Dobson, A.; Foley, J.A.; Lodge, D.M.; Pascual, M.; Pielke, R; Pizer, W.; Pringle, C.; Reid, W.V.; et al. (Science, 2001)
Planning and decision-making can be improved by access to reliable forecasts of ecosystem state, ecosystem services, and natural capital. Availability of new data sets, together with progress in computation and statistics, will increase our ability to forecast ecosystem change. An agenda that would lead toward a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services requires a process that engages scientists and decision-makers. Interdisciplinary linkages are necessary because of the climate and societal controls on ecosystems, the feedbacks involving social change, and the decision-making relevance of forecasts.

Ecology of shrews in tallgrass prairie - Matlack, R.S. (Kansas State University, 2001)
Keywords: tallgrass prairie

The effects of fire on life history traits of tallgrass prairie forbs - Elder, B. (Kansas State University, 2001)
Keywords: tallgrass prairie

Effects of fire on tallgrass prairie plant population dynamics - Benson, E. (Kansas State University, 2001)
Keywords: tallgrass prairie

Effects of mycorrhizas on growth and demography of tallgrass prairie forbs - G.T. Wilson; D.C. Hartnett; M.D. Smith; Kobbeman, K. (American Journal of Botany, 2001)
The effects of arbuscular mycorrhizal (AM) symbiosis on ramet and genet densities, vegetative growth rates, and flowering of three forb species were studied in native tallgrass prairie in northeastern Kansas. Mycorrhizal activity was experimentally suppressed for six growing seasons on replicate plots in an annually burned and an infrequently burned watershed with the fungicide benomyl. Benomyl reduced mycorrhizal root colonization to an average of 4.2%, approximately a two-thirds reduction relative to controls (13.7% colonization). Mycorrhizae influenced the population structure of these forbs. Although mycorrhizal suppression had no long-term effect on genet densities and no effect on ramet survivorship throughout the growing season, the number of ramets per individual was significantly increased such that ramet densities of all three species were approximately doubled in response to long-term mycorrhizal suppression. Effects of mycorrhizae on ramet growth and reproduction varied among species. Ramet growth rates, biomass, and flowering of Salvia azurea were greater in plots with active mycorrhizal symbiosis, whereas mycorrhizae reduced ramet growth rates and biomass of Artemesia ludoviciana. Aster sericeus ramet growth rates and biomass were unaffected by the fungicide applications, but its flowering was reduced.The pattern of responses of these three species to mycorrhizae differed considerably between the two sites of contrasting fire regime, indicating that the interaction of fire-induced shifts in resource availability and mycorrhizal symbiosis together modulates plant responses and the intensity and patterns of interspecific competition between and among tallgrass prairie grass and forb species. Further, the results indicate that effects of mycorrhizae on community structure are a result of interspecific differences in the balance between direct positive effects of the symbiosis on host plant performance and indirect negative effects mediated through altered competitive interactions.
Keywords: demography; forb; tallgrass prairie

Effects of plains pocket gopher (Geomys bursarius) disturbances on tallgrass-prairie community structure - Rogers, W.E.; D.C. Hartnett; Elder, B. (American Midland Naturalist, 2001)
Our objective was to evaluate the effects of soil disturbances created by the plains pocket gopher (Geomys bursarius) on the structure of a tallgrass-prairie plant community. We predicted that soil mounds and burrows would provide sites for the establishment of subordinate plant species, thereby increasing regional plant community richness in this ecosystem that is highly dominated by perennial C4 tallgrasses. Our results, however, revealed that plant species richness and biomass were temporarily decreased or unaffected in areas disturbed by gophers. Moreover, the species found locally on mounds and burrows were a subset of the dominant plants present in the undisturbed plant community and graminoids were more frequent on disturbances than forbs. Our results indicate that perennial graminoids predominate in the rapid recovery of vegetation on pocket gopher mounds and burrows. This preempts the establishment of less frequent forbs and, contrary to our predictions, decreases plant community richness.
Keywords: tallgrass prairie

Effects of ungulate grazers on arbuscular mycorrhizal symbiosis and fungal community structure in tallgrass prairie - Eom, A.H.; G.T. Wilson; D.C. Hartnett (Mycology, 2001)
Complex interactions among mycorrhizal fungi, plants, and herbivores occur in grasslands. Grazing of aboveground vegetation may influence plants directly and indirectly through the alteration of mycorrhizal symbiosis and other below-ground processes, and mycorrhizae in turn can influence plant responses to defoliation. An understanding of these interactions is important to our understanding of the dynamics of plant and fungal communities and to the sound management and conservation of grass- land ecosystems. In this study, the effects of grazing in tallgrass prairie on mycorrhizal colonization of plant roots, fungal community composition, and ex- traradical mycorrhizal hyphal (EMH) development were examined. In October 1994 and 1995 rhizo- sphere samples were taken at different topographical positions in tallgrass prairie sites grazed for several years by cattle at varying intensities, in ungrazed sites, and inside and outside permanent 25-m2 exclosures at each site. Spores of 19 species of AM fungi were encountered in these sites, and Glomus heterosporum was the most abundant species present. Moderate and intense grazing increased root colonization by mycorrhizal fungi in both years of this study. Similar root colonization levels inside and outside permanent exclosures in the ungrazed sites indicated no confounding effects of the exclosure structure itself. In 1995, EMH development was also increased under intense grazing. AM fungal species diversity (based on AM fungal spores present) decreased with grazing under both moderate and high grazer densities in both years. Different fungal species varied in abun- dance with topographical position, however topography did not significantly affect AM fungal spore species diversity, mycorrhizal root colonization or EMH development in either year. Although overall total spore density was unaffected by grazing intensity or soil type, several individual species increased or decreased in response to these factors. These results suggest that defoliation alters plant resources which stimulates greater development of mycorrhizal symbiosis. The shifts in fungal species composition and decrease in diversity with grazing also indicates that defoliation, or alteration of the soil microenviron- ment by grazers, favors certain species of grazing- adapted AM fungi that increase under grazed conditions. The high mycorrhizal dependency of many tallgrass prairie grasses and these results together suggest significant interactions between plant-grazer and plant-fungal relationships in tallgrass prairie. In addition to direct effects of herbivory, our results indicate that grazers may influence grassland plants in- directly through alterations in soil communities and in mycorrhizal symbiosis.
Keywords: fungal communities; fungal diversity; Glomus; hyphal development; mycorrhizae

Emergence of periodical cicadas (Magicicada cassini ) from a Kansas riparian forest: densities, biomass and nitrogen flux - M.R. Whiles; Callaham, M.A.; Meyer, C.K.; B. Brock; Charlton, R.E. (American Midland Naturalist, 2001)
The 1998 emergence of 17-y periodical cicadas (Magicicada cassini) on Konza Prairie Research Natural Area (KPRNA), Kansas, was quantified using emergence trap transects and counts of emergence holes. Emergence density, biomass (emergence production) and associated nitrogen flux were estimated for the entire 100 ha gallery forest of Kings Creek, the major drainage network on KPRNA. Emergence commenced on 22 May 1998 and lasted for 24 d, with 87% of the individuals emerging within the first 9 d. Males dominated early during the emergence, and the sex ratio for the entire population was estimated at 54:46 male:female. Average emergence abundance and biomass estimated from trap transects located in low areas where cicadas were most abundant were 152/m2 and 34.9 g ash-free dry mass (AFDM)/m2, respectively. Based on emergence hole counts, average density and biomass for the 59 ha of gallery forest where cicadas emerged were 27.2 individuals/m2 and 6.3 g AFDM/m2, and emergence hole densities >100/m2 were evident in low areas of the drainage. Emergence density generally decreased with increasing elevation in the catchment. Belowground to aboveground N flux associated with M. cassini emergence in high density areas was ∼3 g N/m2, and the average for the entire emergence area was 0.63 g N/m2. The total number of individuals that emerged from the Kings Creek riparian forest was estimated at 19.6 million, which represents 4.6 metric tons AFDM and ∼0.5 metric tons N. This linear, fragmented, gallery forest of the Flint Hills supports a high density of M. cassini, and an emergence event constitutes a significant belowground to aboveground flux of energy and nutrients. Thus, the periodical cicada may be an exception to the notion that insects generally do not represent important resource pools at the ecosystem level.

Evidence of a mycorrhizal mechanism for the adaptation of Andropogon gerardii (Poaceae ) to high- and low-nutrient prairies - Schultz, P.A.; Miller, R.M.; Jastrow, J.D.; Rivetta, C.V.; Bever, J.D. (American Journal of Botany, 2001)
Andropogon gerardii seed obtained from Kansas and Illinois was grown in a controlled environment in their own and each other's soils, with and without arbuscular mycorrhizal fungi (AMF). Each ecotype grew comparatively better in its own soil indicating adaptation to its soil of origin. Overall, A. gerardii benefited more from AMF in low-nutrient Kansas soil than Illinois soil. The two ecotypes, however, did not benefit equally from mycorrhizal infection. The Kansas ecotype was three times more responsive to mycorrhizal infection in the Kansas soil than was the Illinois ecotype. Our results indicate that plant adaptation to the nutrient levels of their local soils is likely to be due, at least in part, to a shift in their dependence on mycorrhizal fungi. The Illinois ecotype of A. gerardii has evolved a reduced dependence upon these fungi and greater reliance on a more highly branched root system. In contrast, the Kansas ecotype had a significantly coarser root system and invested proportionately greater carbon in the symbiotic association with AMF as measured by spore production. This study provides the first demonstration that plants can adapt to changing soil nutrient levels by shifting their dependence on AMF. This result has broad implications for our understanding of the role of these fungi in agricultural systems.

Factors Controlling Spatial and Temporal Patterns of Nitrogen Cycling in Tallgrass Prairie Streams - Kemp, M.J. (Kansas State University, 2001)
The factors regulating nitrogen cycling in streams draining Konza Prairie Biological Station, Kansas, were analyzed to examine the influence of agricultural activity and non-anthropogenic factors. Patterns of total nitrogen concentrations in the water-column were driven largely by changes in nitrate concentration. A gradient of increasing nitrate occurred from pristine upland reaches to the more agriculturally influenced lowland reaches. The relatively pristine upstream sites had significantly lower nitrification and denitrification rates than the downstream, more agriculturally influenced, sites. Water-column ammonium and nitrate concentrations were correlated with whole stream nitrification rates, but not whole stream denitrification rates. Nitrification rates were positively correlated with denitrification rates at the whole stream level, but not at the substratum level. A significant positive relationship was observed between substrata nitrification rates and dissolved oxygen concentration in all seasons except summer, when concentrations were super saturated. Nitrogen uptake followed Michaelis-Menton kinetics when associated with all substrata, and was 10-fold higher for ammonium relative to nitrate. Nitrification and denitrification responses to variable ammonium, nitrate, and oxygen concentrations differed with substrata type. Substantial temporal variability (< 30%) was predicted in uptake, nitrification, and denitrification due to natural variation in water-column ammonium, nitrate, and oxygen concentrations. These data suggest that natural processes lead to less than 10-fold variation in nitrate concentrations in relatively pristine prairie streams, whereas variation due to agricultural inputs is < 100 fold. Data also suggest that whole stream nitrification and denitrification may be decoupled at the reach level by factors that decrease substrata heterogeneity in stream channels.
Keywords: tallgrass prairie

Feedback loops in ecological hierarchies following urine deposition in tallgrass prairie - Steinauer, M.; Scott. L. Collins (Ecology, 2001)
Although theory predicts that large-scale factors will constrain small-scale interactions, the potential for small-scale events to impact large-scale patch structure is less clear. We examined experimentally the effects of urine deposition, a highly localized event, on small- and large-scale vegetation structure and spatial variation in tallgrass prairie. The response by vegetation to urine deposition may be mediated by grazing. Thus, we also determined the probability of urine patches serving as foci for grazing events by bison. Likelihood of bison grazing was much higher on vs. off urine patches, and grazed areas initiated on urine patches expanded well beyond the area of urine deposition. Abundance of four common graminoid species, and of all graminoids combined, increased on urine patches in ungrazed prairie, while the abundance of Andropogon gerardii and total graminoids decreased on urine patches in grazed prairie. The abundance of Aster ericoides, and all forbs combined, increased on urine patches in ungrazed, but not in grazed, prairie. Species richness and Shannon-Weiner diversity increased on urine patches in ungrazed prairie but were not affected by urine treatment in grazed prairie. Total spatial variance of graminoids increased relative to controls in response to urine treatment, grazing, and the combination of these treatments. For forbs, total variance increased marginally compared to controls only in response to urine treatment in ungrazed prairie. In combination, urine patches plus grazing produced unique large-scale patch structure compared to urine patches in ungrazed prairie. The most important impact of urine patches on community structure resulted from preferential grazing of urine patches by bison, which increases both the size and severity of the grazed area. Urine patches are thus an example of a small-scale perturbation that generates larger-scale patch structure in tallgrass prairie.
Keywords: tallgrass prairie

Fire and grazing regulate belowground processes in tallgrass prairie - Johnson, L.C.; Matchett, J.R. (Ecology, 2001)
In tallgrass prairie, belowground processes are even more important than in forested systems because aboveground biomass and standing dead litter are periodically removed by frequent fires or grazers. Thus, studies that address factors regulating belowground processes are especially relevant for tallgrass prairie. We predicted that effects of grazing and burning differ belowground and that changes in root productivity caused by burning or grazing provide feedback that affects ecosystem fluxes of C and N. These differences in belowground response should be driven largely by changes in N dynamics and the degree to which burning and grazing affect the pathway and magnitude of N loss and the degree of N limitation in these systems. Fire, the major pathway of N loss in ungrazed tallgrass prairie, should result in reduced net N mineralization and N availability. We expected plants to compensate for increased N limitation by increasing their allocation to roots, as manifested in increased soil respiration and C cycling belowground. In contrast, grazing conserves N in the ecosystem by redistributing the N once contained in grass to labile forms in urine and dung. Thus, we predicted that grazing should increase N cycling rates and N availability to plants. Consequently, grazed plants should be less N limited and should allocate less C to roots and more to shoots. This, in turn, should decrease belowground C cycling, manifested as reduced soil CO2 flux. We explored the roles of grazing and burning on root growth in experimental watersheds at Konza Prairie, Kansas, USA. To assess effects of fire on root productivity, we installed root ingrowth cores in two watersheds without grazers that differ in fire frequency: annually vs. infrequently burned (four years since the last fire). To assess effects of grazing, we installed root ingrowth cores in an annually burned watershed grazed by bison and in fenced controls (exclosures). Within bison “grazing lawns,” root ingrowth cores were installed in lightly and heavily grazed patches. Concurrently, we measured in situ rates of net N mineralization and soil respiration as indices of soil N and C cycling. Annual burning resulted in a 25% increase in root growth compared to the unburned watershed (four years since last fire), as plants compensated for N limitation by increasing allocation to roots. Grazing had the opposite effect: it decreased root growth, especially in heavily grazed patches (∼30% less than in fenced controls). Grazing by ungulates increased N cycling and availability. Therefore, grazed plants, instead of being N limited, experienced C limitation as shoots regrew and plants allocated less C to roots. Interestingly, root ingrowth on the long-term unburned watershed was as low as in lightly grazed patches in the grazed watershed. Thus, seemingly disparate treatments such as infrequent burning (characterized by accumulation of detritus aboveground) and grazing (periodic biomass removal) both had higher levels of N availability than annually burned prairie in the absence of grazers. Root growth in unburned and grazed watersheds must be limited by resources other than N (e.g., C in grazing lawns or light in infrequently burned prairie). Burning and grazing also altered root tissue chemistry in contrasting ways that further accentuated the root growth differences caused by these treatments. Frequent fires lowered substrate quality of roots (C:N = 60), thus increasing N limitation. In contrast, grazing and infrequent burning improved root tissue quality (C:N = 40), promoting faster cycling of N. These large differences in root growth and tissue chemistry can result in profound ecosystem-level changes. Grazing increased net N mineralization rates from 87% to 617% compared to watersheds without grazers, whereas annual burning decreased it by ∼50% compared to unburned prairie. Although grazing speeded up N cycling, it reduced soil respiration by 50% compared to fenced controls, presumably because of reduced root mass. On the other hand, annual burning increased soil respiration, presumably because of increased root biomass. Ultimately, differences in the quantity and quality of roots provide feedback to affect C and N cycling and help to maintain and even promote the fundamental differences in N cycling between burning and grazing in tallgrass prairie.
Keywords: tallgrass prairie

Fire in Eastern Ecosystems - Wade, D.; B. Brock; Brose, P.; Grace, J.; Hoch, G.; Patterson, W. (Wildland Fire in Ecosystems: Effects of Fire on Flora. Gen. Tech. Rep. RMRS-GTR-42-vol2, 2001)
Keywords: fire

First record of the cinereus shrew for Riley County, Kansas - Matlack, R.S.; D.W. Kaufman; Charlton, R.E. (The Prairie Naturalist, 2001)

Frequency and extent of water limitation to primary production in a mesic temperate grassland - Alan K. Knapp; J. M. Briggs; Koelliker, J.K. (Ecosystems, 2001)
The frequency and extent of water limitation to aboveground net primary production (ANPP) in a mesic grassland in NE Kansas (Konza Prairie, USA) was assessed with an 8-year irrigation experiment. Since 1991, transects spanning upland and lowland sites in annually burned, ungrazed tallgrass prairie were provided with supplemental water to satisfy evapotranspirational demands. This protocol minimized water limitations during the growing season, as well as interannual variability in water stress. Irrigation of this mesic grassland increased ANPP in 6 of 8 years by an average of 26% when compared to control transects. Although interannual variation in ANPP was greater in uplands than lowlands at nominal levels of precipitation, reducing interannual variability in water availability via irrigation eliminated topographic differences; the irrigation protocol also reduced interannual variability in ANPP by as much as 40%. The addition of supplemental water enabled us to extend the relationship between annual precipitation and ANPP in grasslands to precipitation levels (average, 1153 mm; maximum, 1346 mm) similar to those experienced by more mesic grasslands that today exist only as remnants several hundred kilometers east of Kansas. This relationship was linear (r 2= 0.81), with maximum ANPP (738 g/m2) similar to values reported for sites in Illinois and Wisconsin. After 8 years of irrigation, production of the C3 forb component was twice that in control sites. These results indicate that water limitations in grasslands at the western edge of the presettlement extent of tallgrass prairie affect ANPP in most years and that this high frequency of water limitation may lead to greater dominance of the C4 grasses than is seen in more eastern grassland sites.
Keywords: Andropogon gerardii; C 4 grasses; forbs; grassland; irrigation; leaf water potential; Primary production; tallgrass prairie; water limitation

Gallery forest expansion in tallgrass prairie: mechanisms facilitating oak seedling and juvenile success - Danner, B.T. (Kansas State University, 2001)
Keywords: tallgrass prairie

Growth dynamics of gallery forest oak seedlings (Quercus macrocarpa Michx. and Quercus muhlenbergii Engelm.) from gallery forests: implications for forest expansion into grasslands - Danner, B.T.; Alan K. Knapp (Trees, 2001)
Seedling growth dynamics of Quercus macrocarpa Michx. and Quercus muhlenbergii Engelm. were compared over a 3-month period under optimal growth conditions. These two species are the dominant trees at the western limit of the eastern deciduous forest, and are typically confined to gallery forests along stream beds in tallgrass prairie. Since tallgrass prairie is characterized by a highly variable climate and is prone to periodic drought, we hypothesized that these oaks would have rapid root growth and produce deep taproots as seedlings, enabling them to avoid drought stress and persist in this region. These traits may also facilitate forest expansion into the more xeric tallgrass prairie if fires are suppressed. Taproots of Q. macrocarpa and Q. muhlenbergii grew to approximately 140 cm and 100 cm in length, respectively, after 104 days. In both species, 65% or more of seedling biomass was allocated below ground, and root/total biomass was significantly greater in Q. muhlenbergii at 0–20 and 21–40 days after germination. The seedling taproot elongation rates reported here are much greater than rates reported in other eastern deciduous forest trees. Long-term precipitation data and soil moisture patterns from tallgrass prairie, when combined with rapid taproot elongation rates, suggest that soil moisture may not limit oak establishment or growth in tallgrass prairie in most years, although water uptake by roots was not measured in this study. Other factors, such as fire, herbivory, and seed predation and dispersal may be equally important in constraining the distribution of these species to gallery forests.
Keywords: Gallery forests; Quercus; Seedling; Taproot

Habitat patchiness and plant species richness - Bascompte, J.; Rodriguez, M.A. (Ecological Letters, 2001)
The pattern of woody species richness decline with a decrease in woody vegetation cover was studied within a tallgrass prairie. The decline in species richness is highly non-linear, with a well-defined threshold below which species richness collapses. This relationship can be understood after considering information on how landscape structure changes with woody vegetation cover, and how species richness is related to landscape structure.

Influence of grazing by bison and cattle on deer mice in burned tallgrass prairie - Matlack, R.S.; D.W. Kaufman; Kaufman, G.A. (American Midland Naturalist, 2001)
We studied the influence of grazing by bison (Bos bison) and by cattle (B. taurus) on deer mice (Peromyscus maniculatus) in tallgrass prairie at the Konza Prairie Biological Station in 1997 and 1998. Small mammals were sampled by one 10-station trapline in each of four bison-grazed enclosures, four cattle-grazed enclosures and four ungrazed sites. Enclosures were 4.9 ha and the biomass of grazers in each was similar. All sites were burned annually. We sampled small mammals for 4 consecutive nights in spring before fire, in spring after fire and in autumn. Deer mice were the most abundant species (n = 285; 83% of all small mammals) captured in all treatments and in each trapping period. Deer mice were significantly more abundant in bison-grazed and cattle-grazed sites than in ungrazed sites in spring before fire (P < 0.01 and P < 0.05, respectively), but were similar in abundance in grazed and ungrazed sites following fire. Abundance of deer mice was significantly higher in bison-grazed sites than in cattle-grazed and ungrazed sites in autumn (P < 0.05 and P < 0.001, respectively). Bison and cattle differ in grazing and nongrazing behaviors (e.g., wallowing by bison) that result in differences in vegetation structure. It is likely that differences in deer mouse abundance between bison-grazed and cattle-grazed treatments were due to differences in vegetation structure caused by the two types of grazers.

Interactions between fire and invasive plants in temperate grasslands of North America - Grace, J.B.; M.D. Smith; Grace, S.L.; Scott. L. Collins; Stohlgren, T.J. (Tall Timbers Research Station, 2001)
A substantial number of invasive grasses, forbs and woody plants have invaded temperate grasslands in North America. Among the invading species are winter annuals, biennials, cool-season perennials, warm-season perennials, vines, shrubs, and trees. Many of these species have been deliberately introduced and widely planted; some are still used for range improvement, pastures, lawns, and as ornamentals, though many are listed as state or federal noxious weeds. Others have been greatly facilitated by widespread land disturbance. Historically, fire has been a major selective force in the evolution of temperate grasslands. Further, prescribed fire is commonly used as a method of ecological management for native grassland communities as well as in conjunction with restoration efforts. Within this context, it is important to understand how invasive species will interact with natural and prescribed fire regimes. In this paper, we consider what is known about how exotic species that invade temperate grasslands relate to fire. The primary issues addressed for each species are (1) Does fire appear to enhance colonization? (2) To what degree does fire affect the survival of plants? (3) Are plants that are burned able to regrow following fire and, if so, how rapidly can they recover? (4) How important is competition with native species to the response to fire? and (5) What effect does an invasive species have on the characteristics of the fire regime? For many species, results are preliminary, incomplete, or inconsistent among studies. For this reason, many of the conclusions drawn for individual species must be considered preliminary. Based on analyses of individual species, a conceptual framework is presented for considering how invasive plants may interact with fire when they invade an ecosystem. The major categories of influences are the native community, the fire regime, growth conditions for both invasive and native species, and influences that disturbances, human impacts, and landscape characteristics have had in the past and will have in the future. The examples considered in this paper provide support for a few, tentative generalizations. First, among our current worst invaders of temperate grasslands, adaptation to fire is quite variable. Some species are not well adapted to burning and can be easily eliminated; other species are better adapted but can still be eliminated if fire occurs during periods of particular vulnerability and/or at high frequency. There is a set of species that is extremely well adapted to fire and will not be eliminated through burning alone. Second, competitive interactions with native species play a crucial role in the success of nonnative invaders. In cases where differential burn responses between invasive and native species can be exploited, and adequate populations of native dominant species are present, fire can sometimes tip the competitive balance away from invasives. Third, there are a few invasive species that have exceptional attributes and for which there are no easy solutions. The ability of cheatgrass (Bromus tectorum) to enhance fire, the ability of Chinese tallow (Triadica sebifera) to suppress fire, and the ability of leafy spurge (Euphorbia esula) to resprout from repeated injury make the sespecies exceptional threats to native diversity. Finally, the available information for many invasive species is very incomplete, particularly with regard to how fire affects competitive interactions with the native community. There is much more we need to know if we are to consistently predict how invasive species will respond to fire and how burning can best be used to manage for natural diversity
Keywords: alien plants; exotic species; fire; Grasslands; invasive plants; prairie

Inter-biome comparison of factors controlling stream metabolism - Mulholland, P.J.; Fellows, C.S.; Tank, J.L.; Grimm, N.B.; Webster, J.R.; Hamilton, S.K.; Marti, E.; L.R. Ashkenas; W.B. Bowden; W. K. Dodds; W.H. McDowell; Paul, M.J.; et al. (Freshwater Biology, 2001)
1. We studied whole-ecosystem metabolism in eight streams from several biomes in North America to identify controls on the rate of stream metabolism over a large geographic range. The streams studied had climates ranging from tropical to cool-temperate and from humid to arid and were all relatively uninfluenced by human disturbances. 2. Rates of gross primary production (GPP), ecosystem respiration (R) and net ecosystem production (NEP) were determined using the open-system, two-station diurnal oxygen change method. 3. Three general patterns in metabolism were evident among streams: (1) relatively high GPP with positive NEP (i.e. net oxygen production) in early afternoon, (2) moderate primary production with a distinct peak in GPP during daylight but negative NEP at all times and (3) little or no evidence of GPP during daylight and a relatively constant and negative NEP over the entire day. 4. Gross primary production was most strongly correlated with photosynthetically active radiation (PAR). A multiple regression model that included log PAR and stream water soluble reactive phosphorus (SRP) concentration explained 90% of the variation in log GPP. 5. Ecosystem respiration was significantly correlated with SRP concentration and size of the transient storage zone and, together, these factors explained 73% of the variation in R. The rate of R was poorly correlated with the rate of GPP. 6. Net ecosystem production was significantly correlated only with PAR, with 53% of the variation in log NEP explained by log PAR. Only Sycamore Creek, a desert stream in Arizona, had positive NEP (GPP: R > 1), supporting the idea that streams are generally net sinks rather than net sources of organic matter. 7. Our results suggest that light, phosphorus concentration and channel hydraulics are important controls on the rate of ecosystem metabolism in streams over very extensive geographic areas.

Land cover change in eastern Kansas: litter dynamics of closed-canopy eastern redcedar forests in tallgrass prairie - Norris, M.D.; John M. Blair; Johnson, L.C. (Canadian Journal of Botany, 2001)
In the Great Plains region, eastern redcedar (Juniperus virginiana L.) abundance has increased dramatically in areas historically occupied by tallgrass prairie. This shift in dominant vegetation is likely to be accompanied by changes in ecosystem structure and function, including quantity, quality, and location (above- vs. below-ground) of litter inputs and subsequent effects on decomposition dynamics. The purpose of this study was to quantify and compare patterns of litterfall and decomposition in mature redcedar forests and adjacent prairie. Annual redcedar litterfall was 500 g·m-2·year-1, a large increase in foliar litter inputs compared with annually burned grassland (52 g·m-2·year-1). Using a reciprocal transplant decomposition study with four substrates, redcedar leaves and roots, and big bluestem (Andropogon gerardii Vitman) foliage and roots, we found marginal habitat effects, but greater differences between species, presumably owing to litter quality (including both C:N and lignin content). Decay rates were significantly higher in the prairie relative to the forest for each substrate. Additionally, within any particular habitat, grass litter had significantly faster decay rates than forest litter. These results suggest a shift in patterns of litter input and decomposition processes with afforestation of tallgrass prairie, which may result in long-term changes in C sequestration and storage.Key words: litter dynamics, eastern redcedar (Juniperus virginiana), big bluestem (Andropogon gerardii), decomposition, tallgrass prairie, nitrogen immobilization.
Keywords: tallgrass prairie

Lead contamination and attenuation in a shallow monitoring well, Konza Prairie Long-Term Ecological Research Site, Riley and Geary Counties, KS - Dee, K.T. (University of Kansas, 2001)

Leaf optical properties in higher plants: linking spectral characteristics to stress and chlorophyll concentration - Carter, G.A.; Alan K. Knapp (American Journal of Botany, 2001)

Long-term research and the dynamics of bird populations and communities: an overview - Scott. L. Collins (Auk, 2001)

A method to determine rate and pattern of variability in ecological communities - Scott. L. Collins; Michelli, F.; Hartt, L. (Oikos, 2001)
It is well known that ecological communities are spatially and temporally dynamic. Quantifying temporal variability in ecological communities is challenging, however, especially for time-series data sets of less than 40 measurement intervals. In this paper, we describe a method to quantify temporal variability in multispecies communities over time frames of 10–40 measurement intervals. Our approach is a community-level extension of autocorrelation analysis, but we use Euclidean distance to measure similarity of community samples at increasing time lags rather than the correlation coefficient. Regressing Euclidean distances versus increasing time lags yields a measure of the rate and nature of community change over time. We demonstrate the method with empirical data sets from shortgrass steppe, old-field succession and zooplankton dynamics in lakes, and we investigate properties of the analysis using simulation models. Results indicate that time-lag analysis provides a useful quantitative measurement of the rate and pattern of temporal dynamics in communities over time frames that are too short for more traditional autocorrelation approaches.

Nitrogen competition in a tallgrass prairie ecosystem exposed to elevated carbon dioxide - Williams, M.A.; C. W. Rice; Owensby, C.E. (Soil Science Society of America Journal, 2001)
Because N is a limiting nutrient in tallgrass prairie and most ecosystems, changes in N availability or N cycling could control the long-term response of ecosystems to elevated atmospheric CO2 If more C is sequestered into the soil, then greater microbial demand for N could decrease plant-available soil N. Alterations in N dynamics such as plant uptake, N fixation, nutrient cycling, microbial utilization, and partitioning of N into plant and soil fractions ultimately could affect the capability of ecosystems to sequester C. Our objective was to determine if competition for N between plants and microorganisms changes after 8 yr of elevated CO2 relative to ambient conditions. Treatments (three replications, randomized complete block design) were ambient CO2–no chamber (NC), ambient CO2–chamber (AC), and 2 × ambient CO2–chamber (EC). Several short laboratory incubations assessed whether turnover rates of N in soil would be altered under elevated CO2 Gross transformations of N were not altered significantly under elevated CO2 compared with ambient conditions. To examine plant–microbial competition and altered allocation patterns of N under elevated CO2, 15NH4–N was added to 25-cm-diam. polyvinyl chloride (PVC) cores (15-cm depth) in the field, which were destructively sampled after ≈5 mo. Microbial biomass contained ≈75% of the total 15N that occurred in the soil organic matter (SOM) and, thus, appeared to be a significant regulator of plant-available N. The SOM under elevated CO2 contained significantly more (>27%) 15N compared with ambient CO2 conditions. Though a chamber effect was apparent, greater 15N in the SOM pool and greater percentage 15N SOM/percentage 15N plant suggest greater microbial demand for N under elevated CO2
Keywords: tallgrass prairie

Physiological and morphological traits of exotic, invasive exotic, and native plant species in tallgrass prairie - M.D. Smith; Alan K. Knapp (International Journal of Plant Sciences, 2001)
We compared 13 traits of invasive exotic, noninvasive exotic, and ecologically similar native species to determine if there are generalizable differences among these groups that relate to persistence and spread of exotic species in tallgrass prairie plant communities. When species were grouped as invasive (two species), noninvasive (five species), and native (six species), no differences were found for the suite of traits examined, likely because of the high variability within and between groups. However, when exotic species, regardless of invasiveness, were compared with the native species, specific leaf area was ca. 40% higher for the exotic species, a result that is consistent with that of other studies. This pattern was also observed for five of seven pairwise comparisons of exotic and native species with similar life history traits. In contrast, total end‐of‐season biomass was as much as three times higher for the native species in five of seven of the native‐exotic species pairs. For other traits, differences between exotic and native species were species‐specific and were generally more numerous for noninvasive than for invasive exotic species pair‐wise comparisons. Thus, contrary to predictions, exotic species capable of successfully invading tallgrass prairie did not differ considerably from native species in most traits related to resource utilization and carbon gain. Moreover, invasive exotic species, those capable of displacing native species and dominating a community, were not distinct for the observed traits from their native counterparts. These results indicate that other traits, such as the ability to respond to resource pulses or herbivory, may explain more effectively why certain invasive species are able to invade these communities aggressively.
Keywords: biomass allocation; grassland; invasive plants; photosynthesis; specific leaf area

Regional diversity of braconid wasps (Braconidae: Hymenoptera) collected from sites in Arkansas, Oklahoma and Kansas - Lewis, C.N. (University of Arkansas, 2001)

Regional diversity of braconid wasps (Braconidae: Hymenoptera) collected from sites in Arkansas, Oklahoma and Kansas - Newcomb, L.C. (University of Arkansas, 2001)

Responses of the co-dominant grassland species Andropogon gerardii and Sorghastrum nutans to long-term manipulations of nitrogen and water - Silletti, A.M.; Alan K. Knapp (American Midland Naturalist, 2001)
The availability and distribution of essential resources such as water and nitrogen are changing on a global scale and it is important to determine the effects of such alterations on dominant and subdominant species in ecosystems. We examined the effects of long-term additions of water and nitrogen on leaf-level ecophysiological characteristics of the tallgrass prairie codominants Andropogon gerardii (big bluestem) and Sorghastrum nutans (Indian grass). Both species responded to irrigation with increased water potentials and to fertilization with decreased water potentials. Only in S. nutans, however, were net photosynthesis and stomatal conductance greater in response to both water and nitrogen addition. In contrast, A. gerardii, which currently is more abundant than S. nutans, was relatively unresponsive to resource manipulations. If net photosynthesis is positively related to plant productivity, as has been shown for tallgrass prairie species, the differential photosynthetic responses of these two grasses suggests that their patterns of abundance may change in the future if resource availability is altered. These results are also inconsistent with the historical assumption that these two grasses are “ecological equivalents.”

Seasonality and rates of mineral weathering in karst aquifers at the Konza Prairie - Wood, H.K. (University of Kansas, 2001)

Seed use by vertebrates and invertebrates in the tallgrass prairie - Reed, A.W.; Kaufman, G.A.; Boyer, J.E.; D.W. Kaufman (The Prairie Naturalist, 2001)
Use of seeds by vertebrates and invertebrates was assessed during July through August 1994 in tallgrass prairie in eastern Kansas. Two seed trays were placed at each of 40 stations with one tray available only to vertebrates and one tray available only to invertebrates during day or night. Two seed types, proso millet (Panicum miliaceum) and ryegrass (Lolium perenne), were used because of their different sizes :llld shapes. The greatest amount of seed removed was by diurnal vertebrates followed nocturnal vertebrates and then invertebrates. The large seed type (proso millet) was preferred by both diurnal and nocturnal vertebrates. whereas invertebrates showed no prefrence for seed size. The impact of vertebrates on seeds appeared to be greater than the impact of invertebrates in tallgrass prairie in summer.
Keywords: ants; diurnal and nocturnal seed use; invertebrates; rodents; tallgrass prairie; vertebrates.

Sexual segregation results in differences in content and quality of bison (Bos bison) diets - Post, D.M.; Armbrust, T.A.; Horne, E.A.; Goheen, J. (Journal of Mammalogy, 2001)
We examined diets of bison (Bos bison) bulls, cows, juveniles, and calves to determine differences in quality of diets between groups. Our results showed that bulls had a significantly higher proportion of C4 grasses in their diet than cows, juveniles, or calves. Diets of calves were of higher quality than diets of bulls, cows, or juveniles. Our results provide support for the sexual dimorphism–body size hypothesis of sexual segregation in large ungulates.
Keywords: bison; Bos bison; diet composition; diet quality; sexual segregation

Size of the local species pool determines invasibility of a C4-dominated grassland - M.D. Smith; Alan K. Knapp (Oikos, 2001)
The size of the local species pool (i.e., species surrounding a community capable of dispersal into that community) and other dispersal limitations strongly influence native plant community composition. However, the role that the local species pool plays in determining the invasibility of communities by exotic plants remains to be evaluated. We hypothesized that the richness and abundance of exotic species would be greater in C4-dominated grassland communities if the local species pool included a larger proportion of exotic species. We also predicted that an increase in the exotic species pool would increase the invasibility of sites thought to be resistant to invasion (annually burned grassland). To test these hypotheses, study plots were established within two long-term (>20 yr) fire experiments at a tallgrass prairie preserve in NE Kansas (USA). Study plots were surrounded by either a small pool of exotic species (small species pool (SSP) plots; six species) or a larger exotic species pool (large species pool (LSP) plots; 18 species). We found that richness and absolute cover of exotic species was significantly (P<0.001) lower (∼70 and 90%, respectively) in annually burned compared to unburned plots, regardless of the size of the exotic species pool. As predicted, exotic species richness was higher (P<0.001) for LSP plots (3.9 per 250 m2) than for SSP plots (0.7 per 250 m2); however, absolute cover was unaffected by the size of the exotic species pool. In the absence of fire, plots with a LSP had four times as many exotic species than SSP plots. An increase in the local exotic species pool also increased the invasibility of annually burned grassland. Indeed, richness of exotic plant species in annually burned LSP plots did not differ from unburned plots with a SSP, indicating that a larger pool of exotic species countered the negative effects of fire. These findings have important implications for predicting how the invasion of plant communities may respond to human-induced global changes, such as habitat fragmentation. Community characteristics or factors such as frequent fires in grasslands may impart resistance to invasions by exotic species in large, intact ecosystems. However, when a large pool of exotic species is present, frequent fire may not be sufficient to limit the invasions of exotic plants in fragmented landscapes.

Spatial and temporal patterns of nitrogen concentrations in pristine and agriculturally- influenced prairie streams - Kemp, M.J.; W. K. Dodds (Biogeochemistry, 2001)
Long-term data on nitrogen chemistry of streams draining Konza Prairie Biological Station (Konza), Kansas were analyzed to assess spatial and temporal patterns and examine the influence of agricultural activity on these patterns. Upland watersheds of Konza are predominantly tallgrass prairies, but agricultural fields and riparian forests border the lower reaches of the streams. We have up to 11 years of data in the relatively pristine upland reaches and 4 years of data on wells and downstream reaches influenced by fertilized croplands. Seasonal and spatial patterns in total nitrogen (TN) concentrations were driven largely by changes in the nitrate (NO3 −) concentrations. A gradient of increasing NO3 − concentrations occurred from pristine upland stream reaches to the more agriculturally-influenced lowland reaches. Nitrate concentrations varied seasonally and were negatively correlated with discharge in areas influenced by row-crop agriculture (p = 0.007). The NO3 − concentrations of stream water in lowland reaches were lowest during times of high precipitation, when the relative influence of groundwater drainage is minimal and water in the channel is primarily derived from upland prairie reaches. The groundwater from cropland increased stream NO3 − concentrations about four-fold during low-discharge periods, even though significant riparian forest corridors existed along most of the lower stream channel. The minimum NO3 − concentrations in the agriculturally influenced reaches were greater than at any time in prairie reaches. Analysis of data before and after introduction of bison to four prairie watersheds revealed a 35% increase of TN concentrations (p < 0.05) in the stream water channels after the introduction of bison. These data suggest that natural processes such as bison grazing, variable discharge, and localized input of groundwater lead to variation in NO3 − concentrations less than 100-fold in prairie streams. Row-crop agriculture can increase NO3 − concentrations well over 100-fold relative to pristine systems, and the influence of this land use process over space and time overrides natural processes.
Keywords: ammonium; groundwater; Nitrate; nutrient cycling; riparian buffer zones; streams

Species, season, and density of buried seeds surviving fox squirrel depredation - Smith, C.C.; J. M. Briggs (Prairie Naturalist, 2001)

Temporal vegetation dynamics and recolonization mechanisms on different-sized soil disturbances in tallgrass prairie - Rogers, W.E.; D.C. Hartnett (American Journal of Botany, 2001)
Assessing the various mechanisms by which plants revegetate disturbances is important for understanding the effects of disturbances on plant population dynamics, plant community structure, community assembly processes, and ecosystem function. We initiated a 2-yr experiment examining temporal vegetation dynamics and mechanisms of recolonization on different-sized soil disturbances created to simulate pocket gopher mounds in North American tallgrass prairie. Treatments were designed to assess potential contributions of the seed rain, soil seed bank, clonal propagation from the edges of a soil mound, and regrowth of buried plants. Small mounds were more rapidly recolonized than large mounds. Vegetative regrowth strategies were the dominant recolonization mechanisms, while the seed rain was considerably less important in maintaining the diversity of forbs and annuals than previously believed. All recolonization mechanisms influenced plant succession, but stem densities and plant mass on soil mounds remained significantly lower than undisturbed controls after two growing seasons. Because natural pocket gopher mounds are indistinguishable from undisturbed areas after two seasons, these results suggest that multiple modes of recruitment concurrently, albeit differentially, contribute to the recolonization of soil disturbances and influence tallgrass prairie plant community structure and successional dynamics.
Keywords: tallgrass prairie

Variation among biomes in temporal dynamics of aboveground primary production - Alan K. Knapp; M.D. Smith (Science, 2001)
Interannual variability in aboveground net primary production (ANPP) was assessed with long-term (mean = 12 years) data from 11 Long Term Ecological Research sites across North America. The greatest interannual variability in ANPP occurred in grasslands and old fields, with forests the least variable. At a continental scale, ANPP was strongly correlated with annual precipitation. However, interannual variability in ANPP was not related to variability in precipitation. Instead, maximum variability in ANPP occurred in biomes where high potential growth rates of herbaceous vegetation were combined with moderate variability in precipitation. In the most dynamic biomes, ANPP responded more strongly to wet than to dry years. Recognition of the fourfold range in ANPP dynamics across biomes and of the factors that constrain this variability is critical for detecting the biotic impacts of global change phenomena.
Keywords: Primary production

Vegetation responses to different spatial patterns of soil disturbances in burned and unburned tallgrass prairie - Rogers, W.E.; D.C. Hartnett (Plant Ecology, 2001)
Pocket gopher (Geomyidae) disturbances are created in spatiallypredictable patterns. This may influence resource heterogeneity and affectgrassland vegetation in a unique manner. We attempt to determine the extent towhich density and spatial pattern of soil disturbances influence tallgrassprairie plant community structure and determine how these disturbances interactwith fire. To investigate the effects of explicit disturbance patterns we createdsimulated pocket gopher burrows and mounds in various spatial patterns.Simulated burrows were drilled into the soil at different densities inreplicated plots of burned and unburned prairie. Separate plots of simulatedmounds were created in burned and unburned prairie at low, medium, or high mounddensities in clumped, uniform, or random spatial dispersions. In both burned and unburned plots, increased burrow density decreasedgraminoid biomass and increased forb biomass. Total-plant and graminoid biomasswere higher in burned than unburned plots while forb biomass was higher inunburned plots. Total-plant species richness was not significantly affected byburrow density or burning treatments, but graminoid species richness increasedin unburned plots and forb species richness increased in burned plots. Plant species richness was temporarily reduced directly on mounddisturbances compared to undisturbed prairie. Over time and at larger samplingscales, the interaction of fire and mound disturbance patterns significantlyaffected total-plant and graminoid species richness. The principal effect inburned and unburned prairie was decreased total-plant and graminoid speciesrichness with increased mound disturbance intensity. Although species richness at small patch scales was not increased by anyintensity of disturbance and species composition was not altered by theestablishment of a unique guild of disturbance colonizing plants, our studyrevealed that interactions between soil disturbances and fire alter the plantcommunity dominance structure of North American tallgrass prairie primarily viachanges to graminoids. Moreover, these effects become increasingly pronouncedover time and at larger spatial sampling scales.
Keywords: pattern; soil; spatial; tallgrass prairie; vegetation

Altering rainfall timing and quantity in a mesic grassland ecosystem: Design and performance of rainfall manipulation shelters - Fay, P.A.; Carlisle, J.D.; Alan K. Knapp; John M. Blair; Scott. L. Collins (Ecosystems, 2000)
Global climate change is predicted to alter growing season rainfall patterns, potentially reducing total amounts of growing season precipitation and redistributing rainfall into fewer but larger individual events. Such changes may affect numerous soil, plant, and ecosystem properties in grasslands and ultimately impact their productivity and biological diversity. Rainout shelters are useful tools for experimental manipulations of rainfall patterns, and permanent fixed-location shelters were established in 1997 to conduct the Rainfall Manipulation Plot study in a mesic tallgrass prairie ecosystem in northeastern Kansas. Twelve 9 x 14–m fixed-location rainfall manipulation shelters were constructed to impose factorial combinations of 30% reduced rainfall quantity and 50% greater interrainfall dry periods on 6 x 6–m plots, to examine how altered rainfall regimes may affect plant species composition, nutrient cycling, and above- and belowground plant growth dynamics. The shelters provided complete control of growing season rainfall patterns, whereas effects on photosynthetic photon flux density, nighttime net radiation, and soil temperature generally were comparable to other similar shelter designs. Soil and plant responses to the first growing season of rainfall manipulations (1998) suggested that the interval between rainfall events may be a primary driver in grassland ecosystem responses to altered rainfall patterns. Aboveground net primary productivity, soil CO2 flux, and flowering duration were reduced by the increased interrainfall intervals and were mostly unaffected by reduced rainfall quantity. The timing of rainfall events and resulting temporal patterns of soil moisture relative to critical times for microbial activity, biomass accumulation, plant life histories, and other ecological properties may regulate longer-term responses to altered rainfall patterns.
Keywords: Climate change; floristic diversity; Grasslands; Konza Prairie; life histories; long-term research; Net primary production; precipitation patterns; rainout shelters; soil moisture

Assessment of soil quality in fields with short- and long-term enrollment in the CRP - S.G. Baer; C. W. Rice; John M. Blair (Journal of Soil and Water Conservation, 2000)
Surface [5 to10 cm, (2 to 4 in) depth] soil quality was examined from fields representing short and long term enrollment in the Conservation Reserve Program (CRP). Total carbon (C) and nitrogen (N) amounts were similar in soil with recent and long term enrollment in the CRP and were lower than a native prairie field. Active pools of C and N, however, did increase through the CRP. Soil with long term establishment of native grasses in the CRP exhibited 141% and 33% greater microbial biomass C and N, respectively, than soil recently enrolled in the CRP. Total inorganic N was significantly lower in CRP soil with ten versus no growing seasons and was more representative of levels in a native prairie due to reductions in nitrate availability. Our study indicates that CRP promotes soil restoration; however, ten growing seasons are not adequate for recovery of total soil C and N pools at this depth to pre-cultivation levels.

Biogeochemical consequences of landcover change in eastern Kansas - Norris, M. (Kansas State University, 2000)

Carbon dynamics and microbial activity in tallgrass prairie exposed to elevated CO2 for 8 years - Williams, M.A.; C. W. Rice; Owensby, C.E. (Plant and Soil, 2000)
Alterations in microbial mineralization and nutrient cycling may control the long-term response of ecosystems to elevated CO2. Because micro-organisms constitute a labile fraction of potentially available N and are regulators of decomposition, an understanding of microbial activity and microbial biomass is crucial. Tallgrass prairie was exposed to twice ambient CO2 for 8 years beginning in 1989. Starting in 1991 and ending in 1996, soil samples from 0 to 5 and 5 to 15 cm depths were taken for measurement of microbial biomass C and N, total C and N, microbial activity, inorganic N and soil water content. Because of increased water-use-efficiency by plants, soil water content was consistently and significantly greater in elevated CO2 compared to ambient treatments. Soil microbial biomass C and N tended to be greater under elevated CO2 than ambient CO2 in the 5–15 cm depth during most years, and in the month of October, when analyzed over the entire study period. Microbial activity was significantly greater at both depths in elevated CO2 than ambient conditions for most years. During dry periods, the greater water content of the surface 5 cm soil in the elevated CO2 treatments increased microbial activity relative to the ambient CO2 conditions. The increase in microbial activity under elevated CO2 in the 5–15 cm layer was not correlated with differences in soil water contents, but may have been related to increases in soil C inputs from enhanced root growth and possibly greater root exudation. Total soil C and N in the surface 15 cm were, after 8 years, significantly greater under elevated CO2 than ambient CO2. Our results suggest that decomposition is enhanced under elevated CO2 compared with ambient CO2, but that inputs of C are greater than the decomposition rates. Soil C sequestration in tallgrass prairie and other drought-prone grassland systems is, therefore, considered plausible as atmospheric CO2 increases.
Keywords: elevated CO2; microbial activity; Microbial biomass; Soil C and N; soil water

Comparative ecology of the C4 grassland co-dominants Andropogon gerardii and Sorghastrum nutans - Silletti, A.M. (Kansas State University, 2000)

A comparison of the functional role of crayfishes and central stonerollers in a tallgrass prairie stream - Evans-White, M.A. (Kansas State University, 2000)
Keywords: tallgrass prairie

Disturbance frequency and community stability in native tallgrass prairie - Scott. L. Collins (The American Naturalist, 2000)
Ecological communities are spatially and temporally variable in response to a variety of biotic and abiotic forces. It is not always clear, however, if spatial and temporal variability leads to instability in communities. Instability may result from strong biotic interactions or from stochastic processes acting on small populations. I used 10–15 yr of annual data from the Konza Prairie Long‐Term Ecological Research site to examine whether plant, breeding bird, grasshopper, and small mammal communities in tallgrass prairie exhibit stability or directional change in response to different experimentally induced fire frequencies. Based on ordination and ANOVA, plant and grasshopper communities on annually burned sites differed significantly from plant and grasshopper communities on less frequently burned sites. Breeding birds and small mammals differed among sites as well, but these differences were not clearly related to disturbance frequency. A modified time series analysis indicated that plant communities were undergoing directional change (unstable) on all watersheds, regardless of fire frequency. Contrary to expectations, directional change was greatest on the annually burned sites and lowest on the infrequently burned sites. Unlike the plant communities, breeding bird, grasshopper, and small mammal communities were temporally stable, despite high‐compositional variability from 1 yr to the next. Stability among the consumer communities within these dynamic plant communities occurs because three‐dimensional vegetation structure does not change over time, despite changes in plant species composition. Evidence suggests that instability in the plant community results from strong biotic interactions among temporally persistent core species and stochastic dynamics among infrequent satellite species. Overall, community stability cannot be assessed if the pattern of temporal dynamics is unknown. Long‐term empirical studies of different taxa under different disturbance regimes are needed to determine over what time frames and spatial scales communities may be stable. Such studies are essential for the development of generalities regarding the relationship between disturbance frequency and community stability in terrestrial and aquatic systems.
Keywords: Community dynamics; community stability; disturbance; fire; tallgrass prairie; temporal variability

Ecology of belowground invertebrates in tallgrass prairie - Callaham, M.A. (Kansas State University, 2000)
Keywords: tallgrass prairie

Ecosystems as functional units in nature - John M. Blair; Scott. L. Collins; Alan K. Knapp (Natural Resources and Environment, 2000)

Effects of fire and grazing on soil carbon in rangelands - C. W. Rice; Owensby, C.E. (The Potential of U.S. Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect, 2000)
Keywords: fire

Effects of long-term fungicide application on microbial processes in tallgrass prairie soils - M.D. Smith; D.C. Hartnett; C. W. Rice (Soil Biology & Biochemistry, 2000)
Several studies investigating the role of arbuscular mycorrhizal (AM) fungi in plant communities have included manipulations of AM fungal symbiosis using the fungicide benomyl. The objectives of this study were to evaluate the potential non-target effects of benomyl on soil biota and nutrient cycling in tallgrass prairie and to determine how mycorrhizae may influence these belowground properties. To accomplish these objectives, soil samples were collected during the 1996–1997 growing seasons from long-term benomyl-treated plots established on tallgrass prairie (Manhattan, KS) in 1991, and the following measurements were made: total bacterial and fungal biomass; abundance of nematodes; microbial biomass carbon and nitrogen; substrate-induced respiration; and potentially mineralizable C and N. Long-term benomyl applications resulted in an 80% reduction in mycorrhizal root colonization. By reducing root colonization, benomyl applications resulted in significant decreases in total bacterial biomass and abundance of fungal-feeding and predatory nematodes (20, 12 and 33% reductions compared to control, respectively). Total microbial potential activity (i.e., substrate-induced respiration) increased by 10% with benomyl treatment, whereas the relative contribution of fungi to total microbial activity decreased significantly with benomyl applications. In addition, microbial biomass C increased from 1364 (± 51.2 SE) to 1485 (± 51.2 SE) with benomyl treatment, and total carbon increased significantly (∼8%) only in annually burned soils treated with benomyl. The magnitude of benomyl effects on soil components and processes were small (<33% change with benomyl) relative to effects on mycorrhizal root colonization (80% decrease with benomyl). These results indicate that rather than having large non-target effects, benomyl applications principally affect mycorrhizal root colonization, thereby indirectly influencing soil biota and nutrient availability. Results also indicate that mycorrhizal fungi play an important role in altering the availability and flow of carbon in prairie soil and may influence the composition and abundance of groups of some soil biota. Changes in soil organisms and nutrient availability associated with altered mycorrhizal symbiosis may influence aboveground plant species responses to mycorrhizal suppression, but further research is needed to understand these potential effects.
Keywords: Arbuscular mycorrhizal fungi; Benomyl; carbon; Microbial biomass; Nematodes; nitrogen

The Effects of size and fragmentation on tallgrass prairie plant species diversity - Cully, A.C. (Kansas State University, 2000)
Keywords: tallgrass prairie

Establishing nutrient criteria in streams - W. K. Dodds; Welch, E. (Journal of the North American Benthological Society, 2000)

Estimating tallgrass prairie soil moisture using active satellite microwave imagery and optical sensor inputs - Hutchinson, J.M.S. (Kansas State University, 2000)
Recent advances in active microwave remote sensing techniques provide the potential for monitoring soil moisture conditions at the spatial and temporal scales required for detailed local modeling efforts. The goal of this research was to produce accurate and spatially distributed estimates of soil moisture using a time series of ERS-2 images for the Konza Prairie, a tallgrass environment in northeast Kansas. The methods used in this research involve field data collection of soil moisture, digital image interpretation of optical (NOAA AVHRR and LANDSAT TM) and radar (ERS-2) imagery, and environmental modeling in a raster GIS environment
Keywords: tallgrass prairie

Faunal structure of small mammals in tallgrass prairie: an evaluation of richness and spatiotemporal nestedness - Kaufman, D.M.; Kaufman, G.A.; D.W. Kaufman (Reflections of a Naturalist: Papers Honoring Professor Eugene D. Fleharty, 2000)
Keywords: tallgrass prairie

Feeding ecology and emergence production of annual cicadas (Homoptera: Cicadidae) in tallgrass prairie - Callaham, M.A. Jr.; M.R. Whiles; Meyer, C.K.; B. Brock; Charlton, R.E. (Oecologia, 2000)
The emergence phenology and feeding ecology of annual cicadas in tallgrass prairie are poorly documented. However, these large insects are abundant, and their annual emergence represents a potentially important flux of energy and nutrients from belowground to aboveground. We conducted a study at Konza Prairie Research Natural Area in eastern Kansas to characterize and quantify cicada emergence and associated energy and nutrient fluxes. We established emergence trap transects in three habitat types (upland prairie, lowland prairie, and riparian forest), and collected cicadas every 3 days from May to September. A subset of trapped cicadas was used for species- and sex-specific mass, nutrient, and stable isotope analyses. Five species were trapped during the study, of which three were dominant. Cicadetta calliope and Tibicen aurifera exhibited significantly higher emergence production in upland prairie than in lowland prairie, and were not captured in forested sites at all. T. dorsata emerged from all three habitat types, and though not significant, showed a trend of greater abundance in lowland grasslands. Two less abundant species, T. pruinosa and T. lyricen, emerged exclusively from forested habitats. Nitrogen fluxes associated with total cicada emergence were estimated to be ∼4 kg N ha–1 year–1 in both grassland habitats, and 1.01 kg N ha–1 year–1 in forested sites. Results of stable isotope analyses showed clear patterns of resource partitioning among dominant cicada species emerging from grassland sites. T. aurifera and C. calliope had δ13C and δ15N signatures indicative of feeding on shallowly rooted C4 plants such as the warm-season grasses dominant in tallgrass prairie ecosystems, whereas T. dorsata signatures suggested preferential feeding on more deeply rooted C3 plants.
Keywords: grassland; Insect emergence; Nutrient flux; resource partitioning; Stable isotopes

Fertilization effects of species density and primary productivity in herbaceous plant communities - Gough, L.; Osenberg, C.W.; Gross, K.L.; Scott. L. Collins (Oikos, 2000)
Fertilization experiments in plant communities are often interpreted in the context of a hump-shaped relationship between species richness and productivity. We analyze results of fertilization experiments from seven terrestrial plant communities representing a productivity gradient (arctic and alpine tundra, two old-field habitats, desert, short- and tall-grass prairie) to determine if the response of species richness to experimentally increased productivity is consistent with the hump-shaped curve. In this analysis, we compared ratios of the mean response in nitrogen-fertilized plots to the mean in control plots for aboveground net primary productivity (ANPP) and species density (D; number of species per plot of fixed unit area). In general, ANPP increased and plant species density decreased following nitrogen addition, although considerable variation characterized the magnitude of response. We also analyzed a subset of the data limited to the longest running studies at each site (≥4 yr), and found that adding 9 to 13 g N m−2 yr−1 (the consistent amount used at all sites) increased ANPP in all communities by approximately 50% over control levels and reduced species density by approximately 30%. The magnitude of response of ANPP and species density to fertilization was independent of initial community productivity. There was as much variation in the magnitude of response among communities within sites as among sites, suggesting community-specific mechanisms of response. Based on these results, we argue that even long-term fertilization experiments are not good predictors of the relationship between species richness and productivity because they are relatively small-scale perturbations whereas the pattern of species richness over natural productivity gradients is influenced by long-term ecological and evolutionary processes.

Fine-scale spatial and temporal variation in the relationship between spectral reflectance and a prairie vegetation canopy - Rundquist, B.C. (Kansas State University, 2000)
Close-range remote sensing, or field spectroscopy, involves the use of hand-held or boom-mounted radiometers to study relationships between spectral characteristics of Earth surfaces and their biophysical properties as measured in the field environment. Such data often provide the basis for remote sensing work conducted at broader scales, such as those monitored by modern Earth-observing satellites. However, spatial and temporal variation in the relationships between spectral response and surface characteristics usually are not considered in the analysis of remotely sensed data

Fire and a tallgrass prairie reptile community: effects on relative abundance and seasonal activity - Cavitt, J.F. (Journal of Herpetology, 2000)
Few intensive studies have been conducted on reptile populations of the tallgrass prairie. In addition, the effects of fire on these populations are also largely unknown. I established drift fence arrays connected to funnel traps to study the community composition and seasonal activity of reptiles found on the Konza Prairie Research Natural Area located near Manhattan, Kansas. This design also gave me the opportunity to examine the response of reptile populations to a spring wildfire. A total of 657 individuals representing 12 species were captured from 1994-1996. The results suggest that one species, Coluber constrictor, may respond negatively to recent fire.
Keywords: tallgrass prairie

Genetic and competition studies of Andropogon gerardii , Sorghastrum nutans and Dalea purpurea from remnant and restored tallgrass prairies - Gustafson, D.J. (Southern Illinois University, 2000)

Henslow's Sparrow habitat associations on Kansas tallgrass prairie - Cully, J.F.; Michaels, H.L. (Wilson Bulletin, 2000)
We examined macro- and microhabitat characteristics of breeding Henslow's Sparrows (Ammodramus henslowii) on Fort Riley Military Reservation, Kansas during 1995 and 1996. Survey points were identified at the macrohabitat scale as either grassland, savanna, or woodland edge. A military disturbance index was used to quantify the severity of training disturbance to the vegetation at survey and bird use sites. At the large scale, Henslow's Sparrows were associated with grassland habitat last burned in 1993, two or three years previously. Microhabitat at Henslow's Sparrow use sites had lower tree density than random survey points, but neither shrub density nor military disturbance index differed between use sites and survey points during spring. In summer, the military track index was higher on Henslow's Sparrow's use sites. Habitat used by Henslow's Sparrows was consistently tall and dense vegetation with high litter cover during early spring, late spring, and summer whereas the vegetation of random survey points changed in response to vegetation growth. Characteristics of Henslow's Sparrow use sites included high cover by litter and dense, structurally homogeneous vegetation, whereas litter depth and standing dead vegetation, physiognomic diversity, and military disturbance did not differ from random survey points.
Keywords: tallgrass prairie

Host plant species effects on arbuscular mycorrhizal fungal communities in tallgrass prairie - Eom, A.H.; D.C. Hartnett; G.T. Wilson (Oecologia, 2000)
Symbiotic associations between plants and arbuscular mycorrhizal (AM) fungi are ubiquitous in many herbaceous plant communities and can have large effects on these communities and ecosystem processes. The extent of species-specificity between these plant and fungal symbionts in nature is poorly known, yet reciprocal effects of the composition of plant and soil microbe communities is an important assumption of recent theoretical models of plant community structure. In grassland ecosystems, host plant species may have an important role in determining development and sporulation of AM fungi and patterns of fungal species composition and diversity. In this study, the effects of five different host plant species [Poa pratensis L., Sporobolus heterolepis (A. Gray) A. Gray, Panicum virgatum L., Baptisia bracteata Muhl. ex Ell., Solidago missouriensis Nutt.] on spore communities of AM fungi in tallgrass prairie were examined. Spore abundances and species composition of fungal communities of soil samples collected from patches within tallgrass prairie were significantly influenced by the host plant species that dominated the patch. The AM fungal spore community associated with B. bracteata showed the highest species diversity and the fungi associated with Pa. virgatum showed the lowest diversity. Results from sorghum trap cultures using soil collected from under different host plant species showed differential sporulations of AM fungal species. In addition, a greenhouse study was conducted in which different host plant species were grown in similar tallgrass prairie soil. After 4 months of growth, AM fungal species composition was significantly different beneath each host species. These results strongly suggest that AM fungi show some degree of host-specificity and are not randomly distributed in tallgrass prairie. The demonstration that host plant species composition influences AM fungal species composition provides support for current feedback models predicting strong regulatory effects of soil communities on plant community structure. Differential responses of AM fungi to host plant species may also play an important role in the regulation of species composition and diversity in AM fungal communities.
Keywords: Arbuscular mycorrhizal fungi; fungal diversity; Grasslands; Host specificity; Soil communities

Life history and secondary production of grasshoppers (Orthoptera: Acrididae) in a Kansas tallgrass prairie - Meyer, C.K. (Kansas State University, 2000)
Keywords: tallgrass prairie

Movements of deer mice (Peromyscus maniculatus) in tallgrass prairie in Kansas - Rehmeier, R.L. (Kansas State University, 2000)
Keywords: tallgrass prairie

Patterns and determinants of potential carbon gain in the C3 evergreen Yucca glauca (Liliaceae) in a C4 grassland - Maragni, L.A.; Alan K. Knapp; McAllister, C.A. (American Journal of Botany, 2000)
Yucca glauca is a C3 evergreen rosette species locally common in the C4-dominated grasslands of the central Great Plains. Most congeners of Y. glauca are found in deserts, and Y. glauca’s morphological similarities to desert species (steeply angled leaves, evergreen habit) may be critical to its success in grasslands. We hypothesized that the evergreen habit of Y. glauca, coupled with its ability to remain physiologically active at cool temperatures, would allow this species to gain a substantial portion of its annual carbon budget when the C4 grasses are dormant. Leaf-level gas exchange was measured over an 18-mo period at Konza Prairie in northeast Kansas to assess the annual pattern of potential C gain. Two short-term experiments also were conducted in which nighttime temperatures were manipulated to assess the cold tolerance of this species. The annual pattern of C gain in Y. glauca was bimodal, with a spring productive period (maximum monthly photosynthetic rate = 21.1 ± 1.97 μmol·m−2·s−1) in March through June, a period of midseason photosynthetic depression, and a fall productive period in October (15.6 ± 1.25 μmol·m−2·s−1). The steeply angled leaves resulted in interception of photon flux density at levels above photosynthetic saturation throughout the year. Reduced photosynthetic rates in the summer may have been caused by low soil moisture, but temperature was strongly related (r2 = 0.37) to annual variations in photosynthesis, with nocturnal air temperatures below −5°C in the late fall and early spring, and high air temperatures (>32°C) in the summer, limiting gas exchange. Overall, 31% of the potential annual carbon gain in Y. glauca occurred outside the “frost-free” period (April–October) at Konza Prairie and 43% occurred when the dominant C4 grasses were dormant. Future climates that include warmer minimum temperatures in the spring and fall may enhance the success of Y. glauca relative to the C4 dominants in these grasslands.
Keywords: Climate change; cold tolerance; evergreen; Grasslands; Liliaceae; photosynthesis; tallgrass prairie; Water relations; Yucca

Patterns of mechanisms of eastern redcedar (Juniperus virginiana) expansion into tallgrass prairie in the Flint Hills KS - Hoch, G.A. (Kansas State University, 2000)
Keywords: tallgrass prairie

Patterns of species density and productivity at different spatial scales in herbaceous plant communities - Gross, K.L.; M.R. Whiles; Gough, L.; Inouye, R.; Cox, S.B. (Oikos, 2000)
A major challenge in evaluating patterns of species richness and productivity involves acquiring data to examine these relationships empirically across a range of ecologically significant spatial scales. In this paper, we use data from herb-dominated plant communities at six Long-Term Ecological Research (LTER) sites to examine how the relationship between plant species density and above-ground net primary productivity (ANPP) differs when the spatial scale of analysis is changed. We quantified this relationship at different spatial scales in which we varied the focus and extent of analysis: (1) among fields within communities, (2) among fields within biomes or biogeographic regions, and (3) among communities within biomes or biogeographic regions. We used species density (D=number of species per m2) as our measure of diversity to have a comparable index across all sites and scales. Although we expected unimodal relationships at all spatial scales, we found that spatial scale influenced the form of the relationship. At the scale of fields within different grassland communities, we detected a significant relationship at only one site (Minnesota old-fields), and it was negative linear. When we expanded the extent of analyses to biogeographic regions (grasslands or North America), we found significant unimodal relationships in both cases. However, when we combined data to examine patterns among community types within different biogeographic regions (grassland, alpine tundra, arctic tundra, or North America), we did not detect significant relationships between species density and ANPP for any region. The results of our analyses demonstrate that the spatial scale of analysis – how data are aggregated and patterns examined – can influence the form of the relationship between species density and productivity. It also demonstrates the need for data sets from a broad spectrum of sites sampled over a range of scales for examining challenging and controversial ecological hypotheses.

Prairie vegetation and soil nutrient responses to ungulate carcasses - Towne, E.G. (Oecologia, 2000)
The impact of large ungulate carcasses on grassland dynamics was investigated by monitoring vegetation and soil nutrients in 50-cm circular zones around the center of bison (Bos bison), cattle (B. taurus), and deer (Odocoileus virginianus) carcasses. An ungulate carcass creates an intense localized disturbance that varies with animal size and the season of death. Unlike other natural disturbances, carcasses deposit a concentrated pulse of nutrients into the soil. One year after death, inorganic nitrogen concentrations were significantly higher in the inner 50 cm at both adult and juvenile carcass sites than in surrounding prairie. Areas around a carcass became zones of fertility that favored different components of the vegetation and stimulated biomass production. Species richness and diversity at the center of carcass sites were lowest 1 year after death, but increased significantly in subsequent years. However, warm-season perennial grasses declined near the center of carcass sites and did not recover. Five years after death, ungulate carcass sites remained disturbed patches that harbored vegetation characteristically different in composition and stature from surrounding prairie. By providing a niche for species not normally found in undisturbed prairie, carcasses increased community heterogeneity and may play an important role in adding spatial complexity to grassland ecosytems.
Keywords: Carrion; disturbance; Soil nutrients; succession; tallgrass prairie

Predictive models for grazing distribution: a GIS approach - B. Brock; Owensby, C.E. (Journal of Range Management, 2000)
Grazing distribution and forage use patterns are important influences on rangeland ecosystems. Spatial patterns of grazing by domestic cattle (Bos taurus) were observed over 2 consecutive years under 2 grazing systems, intensive-early stocking and season-long stocking. The purposes were to determine factors influencing observed patterns and develop predictive models for grazing distribution and forage removal. Field-collected data on grazing distribution were linked with associated geophysical properties of pastures utilizing a GIS. Separate models were developed to predict grazing distribution and forage utilization using a backward stepwise regression procedure. The forage utilization model was linked with grazing distribution by utilizing Tobit analysis. Nineteen independent variables were used to interpret the observed variation in grazing distribution. Comparison of predicted probability of grazing values from the model with the observed grazing distribution in a hold-out data set yielded a close fit (R=.99). Eighteen independent variables were included in the forage removal model. Comparison of predicted forage removal with observed values in a hold-out data set yielded a poor fit (R=.28). Lack of forage quality variables probably accounts for the poor performance of the forage removal model. Differences in the success of the 2 models support the hypothesis that grazing distribution and forage utilization operate at different spatial scales and parameters. The use of GIS holds promise as a technique for developing useful predictive models for range management.

Quantification of the nitrogen cycle in a prairie stream - W. K. Dodds; Evans-White, M.A.; N.M. Gerlanc; Gray, L.; Gudder, D.A.; Kemp, M.J.; Lo'pez, A.L.; Stagliano, D.; Strauss, E.; Tank, J.L.; M.R. Whiles; Wollheim, W. (Ecosystems, 2000)
Nitrogen (N) was added for 35 days in the form of 15NH4Cl to Kings Creek on Konza Prairie, Kansas. Standing stocks of N in key compartments (that is, nutrients, detritus, organisms) were quantified, and the amount of labeled N entering the compartments was analyzed. These data were used to calculate turnover and flux rates of N cycling through the food web, as well as nutrient transformation rates. Inorganic N pools turned over much more rapidly in the water column of this stream than in pelagic systems where comparable measurements have been made. As with other systems, the mass of ammonium was low but it was the key compartment mediating nutrient flux through the ecosystem, whereas dissolved organic N, the primary component of N flux through the system, is not actively cycled. Nitrification was also a significant flux of N in the stream, with rates in the water column and surface of benthos accounting for approximately 10% of the total ammonium uptake. Primary consumers assimilated 67% of the inorganic N that entered benthic algae and microbes. Predators acquired 23% of the N that consumers obtained. Invertebrate collectors, omnivorous crayfish (Orconectes spp.), and invertebrate shredders dominated the N flux associated with primary consumers. Mass balance calculations indicated that at least 23% of the 309 mg of 15N added during the 35 days of release was retained within the 210-m stream reach during the release. Overall, the rates of turnover of N in organisms and organic substrata were significantly greater when C:N was low. This ratio may be a surrogate for biological activity with regard to N flux in streams.
Keywords: aquatic insects; C:N ratio; nitrogen cycle; nitrogen export; stream; Trophic structure

Relating biophysical processes to spatial patterns of spectral reflectance: A multiple-scale analysis of prairie vegetation canopies - Rundquist, B.C.; Goodin, D.G.; Smith, A.J. (2000)

Responses of grassland soil invertebrates to natural and anthropogenic disturbances - John M. Blair; Todd, T.C.; Callaham, M.A. (Invertebrates as Webmasters in Ecosystems, 2000)
his chapter aims to (1) summarize the major factors influencing invertebrate abundance and distribution in tallgrass prairie soils, focusing on the responses of selected soil invertebrate groups to natural disturbances (such as fire, grazing and drought); (2) identify potential linkages between changes in soil communities and the effects of disturbances on key plant and soil characteristics or processes; and (3) to discuss potential effects of novel anthropogenic perturbations (altered amounts of precipitation, elevated CO2 and increased N inputs) on soil communities and processes. It focuses on North American tallgrass prairies and draws upon studies undertaken at the Konza Prairie Long-Term Ecological Research site, with results from other grasslands where appropriate.

Soil CO2 flux in a tallgrass prairie - Mielnick, P.C.; Dugas, W.A. (Soil Biology & Biochemistry, 2000)
Soils are an important component of the global carbon budget due to their large C storage capacity and the ability to replenish atmospheric C via soil surface CO2 flux. Our objectives were to quantify year-round soil CO2-C fluxes in a tallgrass prairie and to develop an equation to predict flux using soil temperature and soil water content. Soil CO2-C flux, soil temperature and soil water were measured on selected days throughout the year from 1993 through 1998, n = 216, at the Blackland Research Center, Temple, Texas, USA. On any date, there was little difference in average daily soil temperatures among years, but there were large differences in soil water content among years that often were related to differences in precipitation totals. Soil CO2-C flux had a seasonal pattern that was more similar to soil temperature than soil water (minimum in the winter and maximum in the early summer). Average annual soil CO2-C fluxes, which were 1.6, 1.3, 1.2, 1.0, 2.1 and 1.5 kg CO2-C m-2 yr-1 in 1993 through 1998, respectively, increased with annual precipitation. Regressed separately, the exponential relationship between soil CO2-C flux and soil temperature accounted for approximately 46% of flux variability while a quadratic relationship between flux and soil water content accounted for 26% of the variability. Both terms were combined into one equation that explained about 52% of the flux variance. Predicted and measured fluxes showed similar patterns throughout the year, there was little bias between predicted and measured fluxes, averages were essentially equal and the root mean square error between measured and predicted fluxes was about 38% of the average flux. The equation accounted for 76% of flux variability of an independent data set from the Konza Prairie in Kansas. The relationship between flux, soil temperature and soil water content should provide accurate predictions of soil CO2 flux in tallgrass prairies in the midwestern US
Keywords: tallgrass prairie

Tallgrass prairie snake assemblage. Food habits - Cavitt, J.F. (Herpetological Review, 2000)
Keywords: tallgrass prairie

Temporal and spatial variability in a small mammal community: an example from mixed-grass prairie - Kaufman, G.A.; D.W. Kaufman (Reflections of a Naturalist: Papers Honoring Professor Eugene D. Fleharty, 2000)

Themeda quadrivalvis (Poaceae: Andropogoneae) in Kansas: An exotic plant introduced from birdseed - Towne, E.G.; Barnard, I. (Sida, 2000)

Wallowing behavior of American bison (Bos bison) in tallgrass prairie: an examination of alternate explanations - McMillan, B.R.; Cottam, M.R.; D.W. Kaufman (The American Midland Naturalist, 2000)
Wallowing is a common behavior of American bison (Bos bison). Past explanations and current hypotheses suggested for wallowing behavior include grooming behavior associated with shedding, male-male interaction (typically rutting behavior), social behavior for group cohesion, play behavior, relief from skin irritation due to biting insects, reduction of ectoparasite (tick and lice) load and thermoregulation. We monitored circannual and circadian patterns of wallowing frequency by American bison during 1996–1997 in the tallgrass prairie region of eastern Kansas. Wallowing activity increased from April to late June or July (during 1996 and 1997, respectively), decreased during midsummer, peaked again in September, decreased from September to October and then remained low from November to March. Diurnally, wallowing was low in early morning, increased to a peak in early afternoon and then decreased during mid afternoon and evening. Within the herd adult males wallowed more frequently than adult females and both adult males and females wallowed more frequently than yearlings. We observed behaviors that were consistent with all of the hypotheses previously suggested to explain wallowing behavior by bison. Based on our observations we suggest that the alternate explanations for wallowing behavior are not mutually exclusive. However, only the relief from biting insects hypotheses was consistent with both the circannual and circadian patterns of frequency of wallowing by American bison.
Keywords: tallgrass prairie

Artificial avian nest Predation in a tallgrass prairie - Goodman, J.R. (Ball State University, 1999)
Several species of Neotropical migrant songbirds are experiencing declining population numbers. One of many proposed reasons for these declines is the dramatic loss of suitable prairie and grassland nesting habitat in the central United States. The Konza Prairie - a native tallgrass prairie preserve in central Kansas - was used to study possible edge-effect predation of artificial avian ground nests. Two Japanese quail eggs were placed in created artificial nests along transect lines from a wooded edge, a recently burned edge, and a control area. The rate of nest predation after seven days was 16.1 (±12.9%) for the control area. This was taken to represent the typical base level of artificial nest predation for the Konza Prairie. The predation rates for the wooded edge and burned edge were 21.9% (±7.4%) and 18.0% (±6.0%), respectively. These rates were not statistically different from each other or the base level rate of predation. The data suggests that no edge-effect predation occurs for artificial avian ground nests along wooded or burned edges in the Konza Prairie. Predation rates of natural bird nests may be different than these results suggest. It is recommended that future studies identify nest predators and study their foraging behavior near edge habitat.
Keywords: tallgrass prairie

Biomass production and species composition change in a tallgrass prairie ecosystem after long-term exposure to elevated atmospheric CO2 - Owensby, C.E.; J.M. Ham; Alan K. Knapp; Auen, L.M. (Global Change Biology, 1999)
To determine the long-term impact of elevated CO2 on primary production of native tallgrass prairie, we compared the responses of tallgrass prairie at ambient and twice-ambient atmospheric CO2 levels over an 8-year period. Plots in open-top chambers (4.5 m diameter) were exposed continuously (24 h) to ambient and elevated CO2 from early April to late October each year. Unchambered plots were monitored also. Above-ground peak biomass was determined by clipping each year in early August, and root growth was estimated by harvesting roots from root ingrowth bags. Plant community composition was censused each year in early June. In the last 2 years of the study, subplots were clipped on 1 June or 1 July, and regrowth was harvested on 1 October. Volumetric soil water content of the 0–100 cm soil layer was determined using neutron scattering, and was generally higher in elevated CO2 plots than ambient. Peak above-ground biomass was greater on elevated CO2 plots than ambient CO2 plots with or without chambers during years with significant plant water stress. Above-ground regrowth biomass was greater under elevated CO2 than under ambient CO2 in a year with late-season water stress, but did not differ in a wetter year. Root ingrowth biomass was also greater in elevated CO2 plots than ambient CO2 plots when water stress occurred during the growing season. The basal cover and relative amount of warm-season perennial grasses (C4) in the stand changed little during the 8-year period, but basal cover and relative amount of cool-season perennial grasses (C3) in the stand declined in the elevated CO2 plots and in ambient CO2 plots with chambers. Forbs (C3) and members of the Cyperaceae (C3) increased in basal cover and relative amount in the stand at elevated compared to ambient CO2. Greater biomass production under elevated CO2 in C4-dominated grasslands may lead to a greater carbon sequestration by those ecosystems and reduce peak atmospheric CO2 concentrations in the future.
Keywords: tallgrass prairie

Bison performance and productivity on tallgrass prairie - Towne, E.G. (Southwestern Naturalist, 1999)
Productivity and performance were evaluated over a 4-year period for a herd of nonsupplemented bison (Bos bison) at the Konza Prairie Research Natural Area in northeastern Kansas. Calving rates ranged from 65.7% to 79.2%, with an average of 74.4%. Out of 317 calves born, 47.3% were male and 52.7% were female. Numbers of male and female calves born each year did not deviate from an expected 50:50 ratio except in 1997. At 6 months of age, male bison calves were significantly heavier than female calves. By 7.5 years of age, females weighed an average of 455 kg, and males averaged 727 kg. Male and female calves gained an average of 2.6% of their body mass over their first winter, but all other animals lost an average of 11.3% of their body mass over winter. All winters were relatively mild during this study, and mass losses for different age and sex groups did not differ significantly among years. Performance and productivity data for the Konza Prairie bison provide a benchmark for comparison with other herds.
Keywords: tallgrass prairie

Bison wallowing and its influence on the soil environment and vegetation characteristics in tallgrass prairie - McMillan, B.R. (Kansas State University, 1999)
Keywords: tallgrass prairie

Brown Thrasher Nest Reuse - Cavitt, J.F.; Pearse, A.T.; Miller, T.A. (A Time Saving Resource, Protection From Search-strategy Predators, or Cues for Nest-site Selection? The Condor, 1999)
We examined the potential functions of old nests in a population of Brown Thrashers (Toxostoma rufum) nesting on the Konza Prairie Research Natural Area in northeastern Kansas. We determined whether thrashers reuse nests constructed in previous years, and tested predictions of the hypothesis that old nests function to reduce the risk of nest predation by saturating the cues used by search-strategy predators. We also manipulated old-nest densities to test the hypothesis that old nests are used as indirect cues for nest-site selection. Thrashers were found to reuse nests, albeit at low rates (4% of nests monitored). We found no significant relationships between the density of old nests and the success of active nests, and experimentally removing nests did not influence nest-site selection. These results suggest that old nests may only benefit thrashers in this population as a resource to reduce the time spent in nest construction.

Changes in enzyme activities and microbial biomass of tallgrass prairie soil as related to burning and nitrogen fertilization - Ajwa, H.A.; Dell, C.J.; C. W. Rice (Soil Biology & Biochemistry, 1999)
Microbial biomass and enzyme activities are affected by management practices and can be used as sensitive indicators of ecological stability. Microbial biomass C (MBC), microbial biomass N (MBN) and eight enzyme activities involved in the cycling of C, N, P and S were studied in the surface (0–5 cm) of an Irwin silty clay loam soil (fine, mixed, mesic, Pachic Arguistoll) in a tallgrass prairie ecosystem. Treatments of annual spring burning and N fertilization were initiated in 1986 and encompassed: (1) unburned–unfertilized, (2) burned–unfertilized, (3) burned–fertilized, and (4) unburned–fertilized. Activities of dehydrogenase, β-glucosidase, urease, deaminase, denitrifying enzyme, acid phosphatase, alkaline phosphatase, and arylsulfatase were assayed. Long-term burning and N fertilization of the tallgrass prairie soil reduced MBC and MBN relative to the unburned–unfertilized treatment. The effects of burning and N fertilization varied among the enzymes and the time of sampling. Long-term burning significantly (P<0.05) increased activities of urease and acid phosphatase, but decreased activities of β-glucosidase, deaminase and alkaline phosphatase. Long-term N fertilization significantly increased activities of β-glucosidase and acid phosphatase but decreased urease activity. This study found that several soil enzyme activities can be used as indicators of ecological changes caused by N fertilization and long-term burning management practices. The relevance of these changes in surface soil to the long-term sustainability of this ecosystem needs further evaluation.
Keywords: tallgrass prairie

The comparative floral ecology of seven species of Onagraceae in native tallgrass prairie (pollination) - Nonnenmacher, H.F. (Saint Louis University, 1999)
Seven species of Onagraceae, Tribe Onagreae, occur at sites in Konza Prairie Research Natural Area and Tuttle Creek Reservoir Dam area, controlled by the Kansas Army Corp of Engineers. Three species bloom in the Spring and four species bloom from mid-Summer into Fall. The Spring group displays flowers in an unstratified pattern with fewer, but larger, flowers per stem per day, while the mid-Summer group displays several smaller flowers per day on numerous inflorescences in a stratified, three dimensional pattern on tall plants. Both groups demonstrate high fruit set in three breeding systems. Self-pollinating and self-compatible Calylophus serrulatus (Nutt.) Raven attracts a diverse forager assemblage, but only small bees less than 10mm. carry adequate pollen loads. Outcrossing vernal species include Oenothera macrocarpa Nutt., and O. speciosa Nutt. Both species open at night and attract night-flying moths, but O. macrocarpa is the preferred nectar reward source for Sphingidae, of which six species foraged in a three tiered, niche-partitioning group. Samples of pre and post-forager levels of nectar reserves indicate that in 1995 and 1996, shorter tongued sphingids were the major or foragers. O. biennis L., was weedy and cleistogamous, Gaura longiflora Spach, was weedy but outcrossing, and attracted small to medium sized bees in the morning. G. parviflora Dougl., was a self-pollinating and self-compatible weed, and Stenosiphon linifolius (Nutt.) Heynh. was an outcrosser pollinated mostly by small bees less than 6mm long
Keywords: tallgrass prairie

Comparison of common cytotypes of Andropogon gerardii (Andropoganeae, Poaceae) - Keeler, K.H.; Davis, G.A. (American Journal of Botany, 1999)

The core-satellite species hypothesis provides a theoretical basis for Grimes classification of dominant subordinate, and transient species - D.J. Gibson; Ely, J.S.; Scott. L. Collins (Journal of Ecology, 1999)

Demodicosis in an American Bison - Vestweber, J.G.; Ridley, R.K.; Nietfeld, J.C.; Wilkerson, M.J. (Canadian Veterinary Journal, 1999)
An 18-month-old, male American bison (Bison bison) was presented with 7- to 9-mm size nodules periorbital, perineal, and on the ventral surface of the tail. Demodex spp. were identified from the exudate by microscopic examination. Examination 6 mo later revealed that the infestation had nearly cleared without treatment.