Designs for greenhouse studies of interactions between plants - D.J. Gibson; Connolly, J.; D.C. Hartnett; Weidenhamer, J.D. (Journal of Ecology, 1999)
1 Designs for greenhouse studies of interactions between plants are reviewed and recommendations for their use are provided. 2 Papers published over a 10-year period showed the replacement series design to be the most popular, especially in studying crop–weed interactions. Fifty per cent of the studies involved only two species, although studies testing the interaction between different genotypes of only a few species were also popular. 3 Limitations imposed by the choice of design, the variables measured, and the analysis used on the range of inferences that may be validly drawn from the experiment are frequently not well understood or appropriate for the questions that appear to be addressed. One example is the failure to distinguish the outcome of competition (the long-term outcome of interaction) and the effects of species on each other. 4 Studies in which only final yield is measured are severely limited as to the inferences which may be drawn. Effects due to interspecific interaction during the course of the experiment cannot then be separated from pre-existing differences, and interpretation may be biased towards species whose individuals were initially larger. In addition, measurements at several times are necessary to understand the changing dynamics of species interaction. 5 Simple pair-wise mixtures can assess the effect of treatment factors on the outcome of competition. Replacement series and related diallel designs generally produce results that may be size-biased even when initial interspecific differences are known. Additive designs (including target–neighbour designs), despite confounding density with species proportions, offer considerable scope for addressing mechanistic questions about interspecific interactions. Designs that allow response surface analysis can avoid many of the problems inherent in the other methods, but all need to be adjusted for initial interspecific differences. Designs for multiple species experiments are still largely untested, although several designs have been used. At the level of the individual plant, hexagonal fan designs permit study of the effects of varying the spatial pattern, and the densities and the relative proportions of interacting species, but suffer from lack of independence and lack of randomization.

Do caespitose and rhizomatous grass growth forms constitute unique functional groups? - Derner, J.D.; Briske, D.D.; Eldridge, D.; Freudenberger, D. (People and Rangelands: Building the Future, 1999)
Studies of a semiarid shortgrass plant community (Central Plains Experimental Range, Colorado, USA) and a mesic tallgrass community (Konza Prairie Research Natural Area, Kansas, USA) are described. Soil C and N pools were measured from soil cores taken below rhizomatous and caespitose grass species from both grazed and ungrazed sites. Physiological plasticity was determined for the roots of both grass types by exposure to ammonium sulfate solution and rhizome and root morphological plasticity was determined on the long-term grazed sites. Caespitose grasses [Schizachyrium scoparium and Bouteloua gracilis] accumulated larger pools of nutrients in soils directly beneath plants than rhizomatous grasses [Andropogon gerardii and Pascopyrum smithii [Elymus smithii]] did in rhizomes. Caespitose and rhizomatous grasses had inconsistent modifications of nutrient pools on grazed compared with ungrazed sites, which indicated the occurrence of either species- or system-specific responses. Neither grass type expressed morphological or physiological root plasticity in the mesic community but both grass types expressed morphological root plasticity and the rhizomatous grass displayed significant physiological root plasticity in the semiarid plant community

Does a tradeoff exist between morphological and physiological root plasticity? A comparison of grass growth forms - Derner, J.D.; Briske, D.D. (Acta Oecologica, 1999)
A series of experiments were conducted to evaluate the potential tradeoff between morphological and physiological root plasticity in caespitose and rhizomatous grass growth forms in semi-arid and mesic communities. Morphological and physiological root plasticity were evaluated with in-growth cores and excised root assays, respectively. The rhizomatous grass in the semi-arid community was the only species to display significant physiological root plasticity, but all species possessed the capacity to proportionally increase 15N uptake with increasing concentrations of (15NH4)2SO4 solution. Neither the caespitose nor the rhizomatous grass displayed morphological root plasticity in response to nitrogen addition in the mesic community. In contrast, significant morphological root plasticity occurred in species of both growth forms in the semi-arid community. These data suggest that the compact architecture and the ability to accumulate nutrients in soils directly beneath caespitose grasses did not increase selection pressure for physiological root plasticity at the expense of morphological root plasticity and that the coarse grained foraging strategy and low density of large diameter roots did not increase morphological root plasticity at the expense of physiological root plasticity in rhizomatous grasses. These preliminary data suggest that 1) a high maximum uptake rate for nitrogen in these perennial grasses may minimize the expression of physiological root plasticity, 2) morphological and physiological root plasticity may represent complimentary, rather than alternative, foraging strategies, and 3) the expression of root plasticity may be strongly influenced by abiotic variables within specific habitats.
Keywords: clonal plants; plant foraging; plant-soil relations; Resource heterogeneity

Effect of spring burning on the surface energy balance in a tallgrass prairie - D. Bremer; J.M. Ham (Agricultural and Forest Meteorology, 1999)
Spring burning of dead biomass in tallgrass prairie is a common practice that may influence heat and water vapor transport from the landscape. Bowen ratio methods were used to measure the surface energy balances and evapotranspiration (ET) from burned (B) and unburned (UB) prairie near Manhattan, KS, USA. Data were collected from day of year (DOY) 109–258, 1997 following fire on the B site on DOY 107. Early in the growing season, differences in albedo and surface conductance to water vapor transport (gs, i.e., mulch effect) caused large variations in energy fluxes between B and UB sites. During a 44-day period immediately after the burn (DOY 109–152), albedo averaged 43% lower on the B compared with the UB site. Consequently, available energy (net radiation minus soil heat flux) was 8.6% higher on the B than on the UB site. The gs during that time was over three times higher on the B site, a result of dead biomass removal by fire. During the same period, the daytime Bowen ratios averaged 0.79 on the B site and 2.89 on the UB site, with ET rates of 2.97 mm per day (B site) and 1.40 mm per day (UB site). By DOY 152, canopy growth had moderated differences in albedo and available energy between sites. However, gs and ET remained higher on the B site between DOY 152 and 181. Green leaf area index averaged 71% higher on the B site, and was the primary cause for this mid-season effect (i.e., differences in transpiration). By DOY 182, the effects of the burn on energy fluxes were negligible. Cumulative estimates of ET during the 150-day period were 503 mm on the B site and 408 mm on the UB site, thus, burning increased seasonal ET by 23.3%. Results suggest that land management or environmental factors that affect dead litter, albedo, or green leaf area will have strong impacts on the water and energy balances of a grassland.
Keywords: Bowen ratio; Evapotranspiration; fire; grassland; Land management; Seasonal variation

Effects of altered soil water availability on a tallgrass prairie nematode community - Todd, T.C.; John M. Blair; Milliken, G.A. (Applied Soil Ecology, 1999)
Climate change predictions for the Great Plains region of North America include reduced growing season precipitation. The consequence of this prediction for soil fauna and belowground processes was investigated at two spatial scales by integrating experimental manipulation of soil moisture levels with natural variation in soil-water availability. Experiments consisted of (1) reciprocal core transplants across a regional precipitation gradient and (2) supplemental irrigation applied across a local topographic gradient. This report examines functional-level responses by the tallgrass prairie nematode community to differences in soil moisture levels over a four-year period. Effects on nematode community structure were complex and dependent upon nematode trophic habit and depth in the soil profile. The strongest and most consistent responses to changes in soil-water availability were displayed by herbivorous taxa, with 71% higher densities observed under wetter soil conditions across experiments and years. Responses of microbial-feeding nematodes were more variable, with lower densities observed, in some cases, in the presence of experimentally-increased soil moisture levels. Effects of regional differences in soil-water availability on the nematode community were uniformly restricted to depths >20 cm. Community responses to short-term changes in soil moisture were not consistent with patterns in community structure developed under different natural moisture regimes, suggesting divergent short-term and long-term responses of belowground biota and processes to changes in soil-water availability.
Keywords: Climate change; community structure; Nematode; soil moisture; tallgrass prairie

The effects of bison crossings on the macroinvertebrate community in a tallgrass prairie stream - Fritz, K.M.; W. K. Dodds; Pontius, J. (American Midland Naturalist, 1999)
The distribution and diversity of macroinvertebrates in relation to bison crossings was studied for four seasons in a headwater reach of a tallgrass prairie stream. Species richness was significantly higher above crossings only during the fall. Summer samples revealed significantly higher EPT (richness within only Ephemeroptera, Plecoptera and Trichoptera) index values above crossings than at crossings. On average, over 10% more fine sediment (<0.2 mm) occurred at the crossings than above or below crossings. Densities of two taxa (Hydropsyche spp. and Elmidae) were significantly higher above or below crossings, whereas three taxa (Bezzia/Palpomyia spp., Culicoides sp., and Naididae/Tubificidae) were significantly higher at crossings for at least one season. Overall, this study suggests that impact of bison on benthic communities of headwater streams was spatially limited. Although bison may have less impact upon stream communities than previous studies of cattle impacts have shown, differences in climate and stocking rate could be important factors.
Keywords: tallgrass prairie

Effects of breeding pool permanence on growth and development of western chorus frogs, Pseudacris triseriata , in tallgrass prairie - N.M. Gerlanc (Kansas State University, 1999)
Keywords: tallgrass prairie

Effects of fire, browsers, and gallers on New Jersey Tea (Ceanothus herbaceous) growth and reproduction - Throop, H.L.; Fay, P.A. (American Midland Naturalist, 1999)
Woody plant species in grassland ecosystems can be subjected to damage from fire and multiple herbivore species, but interactions between fire and herbivory can modify their separate impacts on woody plant life histories. We studied how galling (by Periploca ceanothiella, Lepidoptera: Cosmopterigidae), deer browsing (Odocoilius virginianus) and fire affected the growth and reproduction of the woody shrub Ceanothus herbaceous (Rhamnaceae) on a burned and an unburned site at Konza Prairie Research Natural Area in eastern Kansas. Fire was the major influence on C. herbaceous growth, causing plants to produce long unbranched vegetative ramets from protected belowground meristems, while unburned plants were heavily branched and bore shorter shoots and numerous inflorescences. Unburned plants experienced higher gall frequencies, more galls on their longest shoots, but similar deer browsing compared to burned plants. Ramets with herbivore damage had more branches and inflorescences than undamaged ramets, especially where both herbivores were present. Ceanothus herbaceous' flexible life history responses suggest tolerance of multiple forms of damage.
Keywords: fire

The Effects of fire, mowing, and fertilizer amendments on arbuscular mycorrhizas in tallgrass prairie - Eom, A.H.; D.C. Hartnett; G.T. Wilson; Figge, D.A. (American Midland Naturalist, 1999)
Tallgrass prairie sites subjected to 10 y of annual burning, mowing, nitrogen (N) fertilization or phosphorus (P) fertilization and untreated reference sites were studied to examine effects of these management practices on arbuscular mycorrhizal (AM) symbiosis. Spring burning of native prairie field plots significantly reduced AM fungal species diversity, while increasing spore abundance. This increase in total spore number was due to a general increase in most of the 17 fungal species present. In general, the management treatments had larger effects on the richness component of diversity than on the evenness of AM species abundances. Burning and mowing had no significant effects on AM fungal colonization of roots or extraradical mycorrhizal hyphae (EMH) development. However, nitrogen fertilization significantly increased root colonization and EMH development, and P amendment decreased EMH development. There was no significant effect of fertilizer amendment on AM spore abundance, fungal species diversity or richness, but N and P fertilization decreased fungal species evenness. Effects of management practices on AM fungi may be mediated through changes in soil resources or microclimate or through changes in their host plants. These effects on AM symbiosis and community structure are important because AM fungi strongly influence the growth, demography, competitive relationships, relative abundances and diversity of plants in grassland communities.
Keywords: tallgrass prairie

Effects of prairie fire and grazing on brown thrasher nest predation - Cavitt, J.F. (University of Nebraska at Kearney, 1999)
Keywords: fire

Elevated CO2 and leaf longevity in the C4 grassland dominant Andropogon gerardii - Alan K. Knapp; Bargman, N.; Maragni, L.A.; McAllister, C.A.; D. Bremer; J.M. Ham; Owensby, C.E. (International Journal of Plant Sciences, 1999)
In central U.S. grasslands, plant and ecosystem responses to elevated CO2 are most pronounced when water availability is limited. In a northeast Kansas grassland, responses to elevated CO2 in leaf area, number, development, and longevity were quantified for the tallgrass prairie dominant, Andropogon gerardii. Plants were grown in open‐top chambers (OTCs) modified to limit water availability and to maximize responses to elevated CO2. In OTCs with elevated (×2 ambient) levels of CO2, aboveground biomass production and leaf water potentials were increased significantly compared with those of plants in OTCs with ambient CO2. There were no differences in leaf area or leaf number per tiller in A. gerardii in elevated compared with ambient OTCs. However, leaf area in adjacent unchambered plots with greater water availability was significantly higher than in the OTCs. The time required for developing leaves to achieve maximum leaf area was reduced by 29%, and the period of time until leaves senesced was increased by 20% for plants exposed to elevated compared with ambient CO2. Thus, leaves of this C4 grass species expanded more rapidly (6 d) and remained green longer (9 d) when exposed to elevated CO2. Such CO2‐mediated increases in leaf longevity in the dominant species may allow this grassland to respond more opportunistically to temporally variable rainfall patterns in high‐CO2 environments. These responses should be included in leaf‐based simulation models that attempt to mechanistically link physiological alterations to predicted canopy responses to increased CO2.
Keywords: Ecophysiology; elevated carbon dioxide; grassland; leaf lifespan; tallgrass prairie; Water relations

Evaluation of native legumes for use as cover crops - Schartz, R.J.; Janke, R.R. (Journal of Sustainable Agriculture, 1999)
This study evaluated germination and establishment characteristics of native legumes, which may hold potential for development as water-efficient cover crops in Kansas. Twenty-three species were subjected to hot water scarification, cold-moist stratification, and no pretreatment and allowed to germinate on moist filter paper under ambient laboratory conditions for 16 days. In the field, 1 m2 plots were planted with 1.1 grams of seed of each of 23 native species and five introduced species at three planting dates, two in the fall and one in early spring. Seedlings were counted in late June. The effect of seed treatment on germination in the lab was highly species dependent. Hot water scarification had positive (4 species), neutral (16 species), or negative (3 species) effects on early germination (day 2), though fewer differences were seen on day 16. Stratification rarely had significant negative consequences and also affected both the rate and total amount of germination. Both species and planting date had significant effects on establishment in field plots. Establishment of all species was most successful with spring planting. Because of extremely dry conditions, this trend could be attributable to moisture availability. Though these results are preliminary, the lack of germination inhibition and successful establishment of some of the species in the field indicates that this is a promising direction of future research for new cover crops for harsh conditions.
Keywords: cover crop; germination; Native legumes; planting date; seed treatment

Exotic plant species in a C4-dominated grassland: Invasibility, disturbance and community structure - M.D. Smith; Alan K. Knapp (Oecologia, 1999)
We used data from a 15-year experiment in a C4-dominated grassland to address the effects of community structure (i.e., plant species richness, dominance) and disturbance on invasibility, as measured by abundance and richness of exotic species. Our specific objectives were to assess the temporal and spatial patterns of exotic plant species in a native grassland in Kansas (USA) and to determine the factors that control exotic species abundance and richness (i.e., invasibility). Exotic species (90% C3 plants) comprised approximately 10% of the flora, and their turnover was relatively high (30%) over the 15-year period. We found that disturbances significantly affected the abundance and richness of exotic species. In particular, long-term annually burned watersheds had lower cover of exotic species than unburned watersheds, and fire reduced exotic species richness by 80–90%. Exotic and native species richness were positively correlated across sites subjected to different fire (r = 0.72) and grazing (r = 0.67) treatments, and the number of exotic species was lowest on sites with the highest productivity of C4 grasses (i.e., high dominance). These results provide strong evidence for the role of community structure, as affected by disturbance, in determining invasibility of this grassland. Moreover, a significant positive relationship between exotic and native species richness was observed within a disturbance regime (annually burned sites, r = 0.51; unburned sites, r = 0.59). Thus, invasibility of this C4-dominated grassland can also be directly related to community structure independent of disturbance.
Keywords: community structure; disturbance; exotic species; grassland; Invasibility

Expansion of eastern red cedar in the northern Flint Hills, Kansas - Hoch, G.A.; J. M. Briggs (University of Nebraska at Kearney, 1999)

Influence of differing land management on the invasion of North American tallgrass prairie soils by European earthworms - Callaham, M.A. Jr.; John M. Blair (Pedobiologia, 1999)
Keywords: tallgrass prairie

Interacting influence of mycorrhizal symbiosis and competition on plant diversity in tallgrass prairie - M.D. Smith; D.C. Hartnett; G.T. Wilson (Oecologia, 1999)
In tallgrass prairie, plant species interactions regulated by their associated mycorrhizal fungi may be important forces that influence species coexistence and community structure; however, the mechanisms and magnitude of these interactions remain unknown. The objective of this study was to determine how interspecific competition, mycorrhizal symbiosis, and their interactions influence plant community structure. We conducted a factorial experiment, which incorporated manipulations of abundance of dominant competitors, Andropogon gerardii and Sorghastrum nutans, and suppression of mycorrhizal symbiosis using the fungicide benomyl under two fire regimes (annual and 4-year burn intervals). Removal of the two dominant C4 grass species altered the community structure, increased plant species richness, diversity, and evenness, and increased abundance of subdominant graminoid and forb species. Suppression of mycorrhizal fungi resulted in smaller shifts in community structure, although plant species richness and diversity increased. Responses of individual plant species were associated with their degree of mycorrhizal responsiveness: highly mycorrhizal responsive species decreased in abundance and less mycorrhizal responsive species increased in abundance. The combination of dominant-grass removal and mycorrhizal suppression treatments interacted to increase synergistically the abundance of several species, indicating that both processes influence species interactions and community organization in tallgrass prairie. These results provide evidence that mycorrhizal fungi affect plant communities indirectly by influencing the pattern and strength of plant competitive interactions. Burning strongly influenced the outcome of these interactions, which suggests that plant species diversity in tallgrass prairie is influenced by a complex array of interacting processes, including both competition and mycorrhizal symbiosis.
Keywords: Arbuscular mycorrhizal fungi; Competition; diversity; Species coexistence; tallgrass prairie

The keystone role of bison in North American tallgrass prairie - Alan K. Knapp; John M. Blair; J. M. Briggs; Scott. L. Collins; D.C. Hartnett; Johnson, L.C.; Towne, E.G. (BioScience, 1999)

Lone star tick abundance, fire, and bison grazing in tallgrass prairie - Cully, J.F. (Journal of Range Management, 1999)
Lone star ticks (Amblyomma americanum L.) were collected by drag samples of 1 km transects on 12 watersheds at Konza Prairie Research Natural Area near Manhattan, Kans., during summer 1995-1996. Watersheds were treated to 2 experimental treatments: 3 burn intervals (1-year, 4-year, and 20-year) and 2 grazing treatments (grazed by bison (Bos bison L.) or ungrazed). The objectives were to determine whether fire interval, time since most recent burn, and the presence of large ungulate grazers would cause changes in lone star tick abundance in tallgrass prairie in central Kansas. Watersheds burned at 1-year intervals had fewer larvae and adults than watersheds burned at 4-year or 20-year intervals. Watersheds burned during the year of sampling had fewer ticks than watersheds burned one or more years in the past. For watersheds burned 1 or more years in the past there was no effect from time since burn. The presence of bison did not affect tick abundance. Spring burning is an effective method to reduce tick populations in tallgrass prairie during the year of the burn.
Keywords: Amblyomma americanum; habitat; integrated pest management; Ixodidae

Managing Data from Multiple Disciplines, Scales, and Sites to Support Synthesis and Modeling - Olson, R.J.; J. M. Briggs; Porter, J.H.; Mah, G.R.; Stafford, S.G. (Remote Sensing Environment, 1999)
The synthesis and modeling of ecological processes at multiple spatial and temporal scales involves bringing together and sharing data from numerous sources. This article describes a data and information system model that facilitates assembling, managing, and sharing diverse data from multiple disciplines, scales, and sites to support integrated ecological studies. Cross-site scientific-domain working groups coordinate the development of data associated with their particular scientific working group, including decisions about data requirements, data to be compiled, data formats, derived data products, and schedules across the sites. The Web-based data and information system consists of nodes for each working group plus a central node that provides data access, project information, data query, and other functionality. The approach incorporates scientists and computer experts in the working groups and provides incentives for individuals to submit documented data to the data and information system.

Manipulation of soil resource heterogeneity in a tallgrass prairie restoration - S.G. Baer; John M. Blair; Alan K. Knapp (University of Nebraska at Kearney, 1999)
Plant species diversity in native prairie ecosystems is influenced by heterogeneity of soil resources, which results from interactions among plant communities, soil properties, topography, and disturbance. Key factors which promote plant diversity in native prairie include soil moisture, rooting depth, and nutrient availability. Most prairie restorations in the Great Plains occur on former agricultural land and the soil template for these restorations has been physically homogenized through tillage practices. The reduction in soil resource heterogeneity in restored prairies may be causally related to low plant species diversity commonly encountered in these sites. To examine the role of soil heterogeneity in restoring prairie ecosystems, replicated blocks (n=4) of 4 plots consisting of different levels of soil heterogeneity were established in an agricultural field. The 4 plot types included: control (least heterogeneous with respect to soil resources), altered plant rooting depth, altered nutrient availability, and combined variation in plant rooting depth and nutrient availability (maximum heterogeneity). Plant rooting depth was varied by burying limestone barriers at 25 cm to create alternating strips of deep and shallow soil. Variation in soil nutrient (inorganic N) availability was established via increased N (+fertilizer), decreased N (+ recalcitrant C), and no change in N. All plots were seeded with the dominant native grasses and >30 forb species. Incorporation of recalcitrant C reduced total inorganic N availability 90% as a result of 98% reduction in available nitrate. Plots containing strips of low N availability exhibited significantly (p < 0.05) greater spatial variability than plots without this manipulation. Thus, the experimental design and methods implemented have increased heterogeneity of soil nutrients, and this will enable us to address the role of variation in soil resources on restoring tallgrass prairie.
Keywords: altered plant rooting depth; altered soil nutrient availability; Great Plains; limestone barriers; recalcitrant C; soil template; Species diversity

Measuring decomposition, nutrient turnover and stores in plant litter - Harmon, M.E.; Naddlehoffer, K.J.; John M. Blair (Standard Soil Methods for Long Term Ecological Research, 1999)

Multiscale assessment of binary and continuous landcover variables for MODIS validation, mapping, and modeling applications - Milne, B.T.; Cohen, W.B. (Remote Sensing of the Environment, 1999)
Validation, mapping, and modeling efforts require accurate methods to transform process rates and ecosystem attributes estimated from small field plots to the 250–1000-m-wide cells used by a new generation of land cover mapping sensors. We provide alternative scale transformations, each with attendant assumptions and limitations. The choice of method depends on spatial characteristics of the land cover variables in question and consequently may vary between biomes or with the intended application. We extend the fractal similarity dimension renormalization method, previously developed for binary maps, to continuous variables. The method can preserve both the mean and the multifractal properties of the image, thereby satisfying a major goal, namely, to provide accurate areal estimates without sacrificing information about within-site variation. The scale transformation enables the multifractal scaling exponents of landscapes or individual spectral bands to be brought in and out of register with each other, thereby opening another dimension upon which to detect the scales at which various land use or terrain processes operate. Alternatively, landscapes can be selectively rescaled to highlight patterns due to particular processes. We recommend geostatistical procedures with which to assess spatial characteristics both within a site and within individual image cells. We recommend that aggregation of fine-grain measurements during validation of the Moderate Resolution Imaging Spectrometer (MODIS) products be based on continuous variables to reduce errors that originate from uncertainties in binary maps.

Mycorrhizae influence plant community structure and diversity in tallgrass prairie - D.C. Hartnett; G.T. Wilson (Ecology, 1999)
In grassland ecosystems, symbiotic associations between plants and mycorrhizal fungi are widespread and have important influences on the life histories, demography, and species interactions of plants, and on belowground ecosystem processes. To assess the consequences of the symbiosis at the plant community level, we conducted a 5-yr field experiment in tallgrass prairie to investigate the influence of arbuscular mycorrhizal fungi on plant species composition, relative abundances, and diversity. Replicate plots in which mycorrhizal fungi were suppressed with benomyl application every two weeks during each growing season, were compared to nontreated mycorrhizal control plots on six watershed units at the Konza Prairie in northeastern Kansas. Benomyl successfully reduced mycorrhizal colonization to <25% of mycorrhizal control plots. Mycorrhizal colonization of roots in control plots was inversely related to annual precipitation. Suppression of mycorrhizae resulted in decreases in abundances of the dominant, obligately mycotrophic C4 tall grasses, compensatory increases in abundances of many subordinate facultatively mycotrophic C3 grasses and forbs, but no change in total aboveground biomass, as estimated from canopy density. Suppression of mycorrhizal symbiosis resulted in a large increase in plant species diversity. Two possible mechanisms for mycorrhizal mediation of plant species composition and diversity are: (1) alterations in resource distribution among neighbors via hyphal connections, and (2) differential host species responses to mycorrhizal fungal colonization in communities in which the competitive dominants are more strongly or more weakly mycotrophic than their neighbors. The results of this study demonstrate that mycorrhizal symbiosis can have large effects on plant community structure, and that differential host species response to fungal colonization is a key factor explaining the dominance of warm-season C4 grasses in tallgrass prairie and limiting plant species evenness and diversity. The results also underscore the importance of above- and belowground linkages in tallgrass prairie and indicate that alterations in belowground fungi and rhizosphere processes can have large effects on aboveground floristic composition and diversity in grasslands.
Keywords: tallgrass prairie

Nitrogen limitation in dryland ecosystems: responses to temporal and geographical variation in precipitation - Hooper, D.U.; Johnson, L.C. (Biogeochemistry, 1999)
We investigated the relationship between plant nitrogen limitation and water availability in dryland ecosystems. We tested the hypothesis that at lower levels of annual precipitation, aboveground net primary productivity (ANPP) is limited primarily by water whereas at higher levels of precipitation, it is limited primarily by nitrogen. Using a literature survey of fertilization experiments in arid, semi-arid, and subhumid ecosystems, we investigated the response of ANPP to nitrogen addition as a function of variation in precipitation across geographic gradients, as well as across year-to-year variation in precipitation within sites. We used four different indices to assess the degree of N limitation: (1) Absolute Increase of plant production in response to fertilization (the slope of ANPP vs. amount of added N at different levels of annual precipitation); (2) Relative Response (the percent increase in fertilized over control ANPP at different levels of N addition); (3) Fertilizer Use Efficiency (FUE, the absolute gain in productivity per amount of fertilizer N), and (4) Maximum Response (the greatest absolute increase in ANPP at saturating levels of N addition). Relative Response to fertilization did not significantly increase with increasing precipitation either across the geographic gradient or across year-to-year variation within sites. Nor did the Maximum Response to fertilization increase with increasing precipitation across the geographic gradient. On the other hand, there was a significant increase in the Absolute Increase and FUE indices with both geographical and temporal variation in precipitation. Together, these results indicate that there is not necessarily a shift of primary limitation from water to N across the geographic water availability gradient. Instead, our results support the hypothesis of co-limitation. The apparently contradictory results from the four indices of N limitation can best be explained by an integration of plant ecophysiological, community, and ecosystem mechanisms whereby plants are co-limited by multiple resources, species shifts occur in response to changing resource levels, and nitrogen and water availability are tightly linked through biogeochemical feedbacks.
Keywords: arid; Fertilization; Net primary productivity; nitrogen limitation; semi-arid; Water availability

Nutrient and energy characteristics of invertebrates from two locations in Kansas - Shawn, C.P.; Robel, R.J.; Kemp, K. (The Prairie Naturalist, 1999)
We collected Carabidae, Gryllidae, and Acrididae from three areas in two locations in Kansas to determine if their nutrient and energy characteristics were reated to soil fertility. Carbon content (%) of Acrididae was greater in samples collected on areas with higher soil carbon and nitrogen. Protein content (%) of Carabidae biomass was not related to soil fertility whereas Acrididae was. Calcium and phosphorus content (ppm) of Carabidae biomass did not differ by area, but potassium connntent did. Calcium, phosphorus, potassium, and energy (cal/g) content of Gryllidae biomass varied with frequency of burning in tallgrass prairie. Energy content of Carabidae biomass varied by area and burning; frequency. Protein content did not differ among the three invertebrate taxa, but calcium, phosphorus, and potassium content did. Energy content of Carabidae was greater than that of Acrididae. Differences in nutrient and energy content of invertebrate biomass appeared to be related to vegetation on the areas, which was a reflection of soil fertility.
Keywords: acrididae; Carabidae; energy content; Gryllidae; invertebrates; Konza Prairie; nutrient content

Ophthalmic examination and conjunctival bateriologic culture results from a herd of North American bison - Davidson, H.J.; Vestweber, J.G.; Brightman, A.H.; van Slyke, T.H.; Cox, L.K.; Chengappa, M.M. (Journal of the American Veterinary Medical Association, 1999)

Phenological influences on the albedo of prairie grassland and crop fields - Song, J. (International Journal of Biometeorology, 1999)
The albedo of land surfaces is strongly affected by transient surface conditions. For a vegetated surface, albedo can change with soil moisture, fractional canopy cover, and plant phenology as well as solar zenith angle (θs). In this study, the relationships between albedo and plant phenology in prairie grassland and agricultural crops were examined by removing the effect of variations in θs. Albedos were evaluated at a constant θs, which was assigned to be 20° in this study. For days with a minimum θs larger than 20°, a polynomial function that relates albedos to θs was derived and applied to estimate the albedos at 20°. After the removal of θs variations, the observed albedos of grassland at the Konza Prairie showed a linearly decreasing trend from spring to winter due to prairie phenology. The observed albedo of a maize field showed a clear increase from seedling to peak green stage, except when drought caused a decrease in near-infrared reflectance. The observed albedos of a winter wheat field showed an uninterrupted decrease from peak green to harvesting stage.
Keywords: Agricultural crops; Albedo; phenology; Prairie grassland; Solar zenith angle

Rare species of small mammals in northeastern Kansas tallgrass prairie - McMillan, B.R.; D.W. Kaufman; Kaufman, G.A. (University of Nebraska at Kearney, 1999)
We sampled small mammals in native tallgrass prairie habitat from autumn 1981 to spring 1998 on Konza Prairie Research Natural Area, Kansas. In 130,560 trap-nights, we captured 14 species of small mammals. In decreasing order of abundance, the relatively common species were the deer mouse (Peromyscus maniculatus), western harvest mouse (Reithrodontomys megalotis), Elliot's short-tailed shrew (Blarina hylophaga), white-footed mouse (P. leucopus), prairie vole (Microtus ochrogaster), thirteen-lined ground squirrel (Spermophilus tridecemlineatus), and hispid cotton rat (Sigmodon hispidus). Likewise, rare species were the southern bog lemming (Synaptomys cooperi), hispid pocket mouse (Chaetodipus hispidus), eastern woodrat (Neotoma floridana), house mouse (Mus musculus), plains harvest mouse (Reithrodontomys montanus), least shrew (Cryptotis parva), and meadow jumping mouse (Zapus hudsonius). Relative abundances of the rare species ranged from 0.002 (individuals/trapline/sampling period) for the meadow jumping mouse to 0.112 for the southern bog lemming. All rare species combined comprised approximately 2% of the small mammal community in grasslands on Konza Prairie. Southern bog lemmings selectively used sites that were left unburned for 2-3 years in contrast to those burned annually and those unburned for s 4 years. Time since fire had no detectable effect on numbers of individuals for the other 6 rare species. In addition, southern bog lemmings, eastern woodrats, and hispid pocket mice were distributed nonrandomly with respect to topography.
Keywords: Chaetodipus hispidus; Cryptotis parva; eastern woodrat; fire; hispid pocket mouse; house mouse; Konza Prairie Research Natural Area; least shrew; meadow jumping mouse; Mus musculus; Neotoma floridana; plains harvest mouse; Reithrodontomys montanus; southern bog lemming; Synaptomys cooperi; topography; Zapus hudsonius

Relationships between leaf area index and Landsat TM spectral vegetation indices across three temperate zone sites - Turner, D.P.; Cohen, W.B.; Kennedy, R.E.; Fassnacht, K.S.; J. M. Briggs (Remote Sensing of the Environment, 1999)
Mapping and monitoring of leaf area index (LAI) is important for spatially distributed modeling of vegetation productivity, evapotranspiration, and surface energy balance. Global LAI surfaces will be an early product of the MODIS Land Science Team, and the requirements for LAI validation at selected sites have prompted interest in accurate LAI mapping at a more local scale. While spectral vegetation indices (SVIs) derived from satellite remote sensing have been used to map LAI, vegetation type, and related optical properties, and effects of Sun–surface–sensor geometry, background reflectance, and atmospheric quality can limit the strength and generality of empirical LAI–SVI relationships. In the interest of a preliminary assessment of the variability in LAI–SVI relationships across vegetation types, we compared Landsat 5 Thematic Mapper imagery from three temperate zone sites with on-site LAI measurements. The sites differed widely in location, vegetation physiognomy (grass, shrubs, hardwood forest, and conifer forest), and topographic complexity. Comparisons were made using three different red and near-infrared-based SVIs (NDVI, SR, SAVI). Several derivations of the SVIs were examined, including those based on raw digital numbers (DN), radiance, top of the atmosphere reflectance, and atmospherically corrected reflectance. For one of the sites, which had extreme topographic complexity, additional corrections were made for Sun–surface–sensor geometry. Across all sites, a strong general relationship was preserved, with SVIs increasing up to LAI values of 3 to 5. For all but the coniferous forest site, sensitivity of the SVIs was low at LAI values above 5. In coniferous forests, the SVIs decreased at the highest LAI values because of decreasing near-infrared reflectance associated with the complex canopy in these mature to old-growth stands. The cross-site LAI–SVI relationships based on atmospherically corrected imagery were stronger than those based on DN, radiance, or top of atmosphere reflectance. Topographic corrections at the conifer site altered the SVIs in some cases but had little effect on the LAI–SVI relationships. Significant effects of vegetation properties on SVIs, which were independent of LAI, were evident. The variability between and around the best fit LAI–SVI relationships for this dataset suggests that for local accuracy in development of LAI surfaces it will be desirable to stratify by land cover classes (e.g., physiognomic type and successional stage) and to vary the SVI.

Responses of Bell's vireos to brood parasitism by the brown-headed cowbird in Kansas - Parker, T.H. (Wilson Bulletin, 1999)
I studied patterns of cowbird parasitism and responses to this parasitism by Bell's Vireos (Vireo bellii) in Kansas. Bell's Vireos abandoned parasitized nests at a significantly higher rate than unparasitized nests. Lower probability of brood parasitism later in the season may help make abandonment followed by renesting beneficial. Burial of cowbird eggs by vireos was also observed in several cases. I did not detect a strong relationship between nest site vegetation characteristics and the probability of brood parasitism.

Responses of soil microarthropods to changes in soil water availability in tallgrass prairie - O'Lear, H.E.; John M. Blair (Biology and Fertility of Soils, 1999)
Changes in precipitation and soil water availability predicted to accompany global climate change would impact grasslands, where many ecosystem processes are influenced by water availability. Soil biota, including microarthropods, also are affected by soil water content, although little is known about how climate change might affect their abundance and distribution. The goal of this study was to examine soil microarthropod responses to altered soil water availability in tallgrass prairie ecosystems. Two separate experiments were done. The first utilized control and irrigated plots along a topographic gradient to examine the effects of soil water content on microarthropod densities. Microarthropods, mainly Acari, were significantly less abundant in irrigated plots and were generally less abundant at the wetter lowland sites. The second study utilized reciprocal core transplants across an east-west regional precipitation gradient. Large, intact cores were transplanted between a more mesic tallgrass site (Konza Prairie) and a more arid mixed-grass site (Hays) to determine the effects of different soil water regimes on microarthropod abundance and vertical distribution. Data from non-transplanted cores indicated greater total microarthropod densities at the drier Hays site, relative to the wetter Konza Prairie site. Data from the transplanted cores indicated significant effects of location on Acari densities in cores originating from Hays, with higher densities in cores remaining at Hays, relative to those transplanted to Konza. Acari densities in cores originating from Konza were not affected by location; however, oribatid mite densities generally were greater in cores remaining at Konza Prairie. These results confirm the importance of soil water content in affecting microarthropod densities and distributions in grasslands, and suggest complex, non-linear responses to changes in water availability.
Keywords: Acari; Climate change; Grassland soils; Soil microarthropods; Soil water content

Soil air carbon dioxide and nitrous oxide concentrations in profiles under tallgrass prairie and cultivation - Sotomayor, D.; C. W. Rice (Journal of Environmental Quality, 1999)
Assessing the dynamics of gaseous production in soils is of interest because they are important sources and sinks of greenhouse gases. Changes in soil air carbon dioxide (CO2) and nitrous oxide (N2O) concentrations were studied in a Reading silt loam (fine-silty, mixed, mesic Typic Argiudolls) under prairie and cultivation. Concentrations were measured in situ over a 17-mo period to a depth of 3 m. Multilevel samplers permitted collection of gases with subsequent measurement by gas chromatography in the laboratory. Soil air N2O concentrations were near atmospheric levels for a majority of the study period in the prairie site (0.184–2.25 µL L−1) but were significantly higher in the cultivated site (0.257–7.56 µL L−1). Annual mean N2O concentrations were 0.403 and 1.09 µL L−1 in the prairie and cultivated sites, respectively. Soil air CO2 annual mean concentrations were 1.56 × 104 and 1.10 × 104 µL L−1 and ranged from 0.096 × 104 to 6.45 × 104 µL L−1 and 0.087 × 104 to 3.59 × 104 µL L−1 in the prairie and cultivated sites, respectively. Concentrations generally increased with depth, with maximum soil air N2O and CO2 concentrations at 1.0 m in the prairie site and 0.5 m in the cultivated site. Nitrous oxide in the cultivated site and CO2 at both sites did not change markedly over winter months, but CO2 and N2O concentrations reached maximums during the summer months and decreased as the year progressed. Although soil air concentrations peaked and decreased faster at shallower depths, deeper depths exhibited relative maximum concentrations for longer time periods.
Keywords: tallgrass prairie

Soil Carbon and nitrogen availability: Nitrogen mineralization, nitrification, soil respiration potentials - Robertson, G.P.; Wedin, D.; Groffman, P.M.; John M. Blair; Holland, E.; Nadelhoffer, K.J.; Harris, D. (Standard Soil Methods for Long Term Ecological Research, 1999)

Soil invertebrates - Coleman, D.C.; John M. Blair; Elliott, E.T.; Wall, D.H. (Standard Soil Methods for Long Term Ecological Research, 1999)

Success of C4 photosynthesis in the field: lessons from communities dominated by C4 plants - Alan K. Knapp; Medina, E. (C4 Plant Biology, 1999)

Survey of common sunflower (Helianthus annuus) resistance to imazethapyr and chlorimuron in northeast Kansas - Baumgartner, J.R.; Al Khatib, K.; Currie, R.S. (Weed Technology, 1999)
Imazethapyr resistance in common sunflower (Helianthus annuus) was confirmed in 1996 in a field near Rossville, KS. In 1997, common sunflower achenes were collected within a 20-km radius of the field with known resistance to determine if resistance was present in nearby fields or if resistance had spread to the native population on the roadside. Collections were made from 14 soybean (Glycine max) fields, one corn (Zea mays) field, and 11 roadsides. Achenes from Konza Prairie Research Natural Area, a prairie that had received no herbicide applications in the past 25 yr, served as the susceptible control. Common sunflower seedlings were treated in a greenhouse with 71 g ai/ha imazethapyr and 11 g ai/ha chlorimuron. In all 15 fields sampled, at least 1% of the common sunflower exhibited an intermediate response to imazethapyr or chlorimuron. In 13 fields, at least 1% of the plants were resistant to imazethapyr, and in all 15 fields, at least 1% of the plants were resistant to chlorimuron. Ten roadsides had common sunflower that showed intermediate response to imazethapyr or chlorimuron. At least 1% of the plants from seven roadsides were resistant to imazethapyr or chlorimuron. Common sunflower collected from fields with repeated applications of imazethapyr showed more resistance to imazethapyr than to chlorimuron. Nomenclature: Chlorimuron, 2-(((((4-chloro-6-methoxy-2-pyrimidinyl)amino)carbonyl)amino)sulfonyl)benzoic acid; imazethapyr, 2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1-H-imidazol-2-yl)-5-ethyl-3-pyridinecarboxylic acid; common sunflower, Helianthus annuus L. 3 HELAN; corn, Zea mays L.; soybean, Glycine max (L.) Merr

Variation in grazing tolerance among three tallgrass prairie plants - Damhoureyeh, S.A. (Kansas State University, 1999)
Keywords: tallgrass prairie

Variations in microbial activity due to fluctuations in soil water content at the water table interface - Banks, M.K.; Clennan, C.; W. K. Dodds; C. W. Rice (Journal of Environmental Science and Health, 1999)
A soil column experiment was designed to investigate the response of an indigenous microbial population to a vertically fluctuating water table. A subsurface environment with a transitional zone was simulated. The water table in the soil columns was raised and lowered, and compared to columns under static conditions. Carbon dioxide and oxygen concentrations were measured. Peaks of CO2 occurred in the fluctuating columns immediately following a rise in the water table. Dissolved O2 in the fluctuating columns was consistently lower throughout the experiment, but these lower concentrations were exaggerated immediately following a rise in the water table. Values for total organic carbon in the pore water were slightly lower in the fluctuating columns. The results of this soil column study indicate that vertical fluctuation of the water table can enhance microbial activity of indigenous soil microbial populations. This increase in microbial activity suggests an increased rate of available carbon under these conditions.
Keywords: bioremediation; microbial activity; soil interface; soil texture; Soil water content; subsurface sediments

Weather effects on winter birds: the response of a Kansas winter bird community to weather, photoperiod, and year - Stapanian, M.A.; Smith, C.C.; Finck, E.J. (Wilson Bulletin, 1999)

Animal populations and communities - D.W. Kaufman; Kaufman, G.A.; Fay, P.A.; Zimmerman, J.L.; Evans, E.W. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Aspects of methane flow from sediment through emergent cattail (Typha latifolia) plants - Yavitt, J.B.; Alan K. Knapp (New Phytologist, 1998)
We measured the flow of methane in Typha latifolia L. (cattail)-dominated wetlands from microbial production in anoxic sediment into, through, and out of emergent T. latifolia shoots (i.e. plant transport). The purpose was to identify key environmental and plant factors that might affect rates of methane efflux from wetlands to the Earth's atmosphere. Methane accumulated in leafy T. latifolia shoots overnight, reaching concentrations up to 10000 μl l−1 (vs. atmospheric concentrations <4 μl l−1), suggesting that lower stomatal conductance at night limits methane efflux from the plant into ambient air. Daytime light and (or) lower atmospheric humidity that induce convective gas flow through the plant coincided with (a) an increase in the rate of methane efflux from T. latifolia leaves to ambient air (from <0·1 to >2·0 μmol m−2 (leaf) s−1) and (b) a decrease in shoot methane concentration to <70 μl l−1. Very short fluctuation in stomatal conductance during the day did not affect the methane efflux rate unless, possibly, the rate of photosynthesis decreased. A strong relationship between the maximum daily rate of methane efflux and shoot methane concentration (measured before the onset of convective gas flow) suggests T. latifolia plants behave like a capacitor (filling with methane at night, emitting the stored methane during the day). Experimentally cutting leaves (to prevent pressurization) reduced plant capacitance for methane.

Belowground biology and processes - C. W. Rice; Todd, T.C.; John M. Blair; Seastedt, T.R.; Ramundo, R.A.; G.T. Wilson (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Biotic interactions between grazers and plants: Relationships contributing to atmospheric boundary layer dynamics - Dyer, M.I.; Turner, C.L.; Seastedt, T.R. (Journal of Atmospheric Sciences, 1998)
During 1987 and 1988 First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE) studies conducted in the tallgrass prairie of central Kansas, variations in ungulate grazing intensity produced a patchy spatial and temporal distribution of remaining vegetation. Equally variable plant regrowth patterns contributed further to a broad array of total primary production that resulted in a pronounced mosaic of grazing impacts. This regrowth potential, derived from a relative growth rate (RGR) equation comparing ungrazed and grazed plants, determines much of the ecosystem dynamics within and among the grazed pastures and between years. Rates of change in new plant growth (DRGRg) ranged from 2100% to 140%; however, 78% of the time in 1987 and 71% in 1988, productivity increased as a function of grazing intensity. Since plant growth potential in ungrazed (RGRug) and grazed systems (RGRg) have inherently different attributes, interactions with the abiotic environment may develop many uncertainties. Thus, changes in growth rates in grazed areas compared to ungrazed areas (DRGRg) may impose major controls over system productivity and associated biological processes currently not accounted for in ecosystem models. Because FIFE microsite atmospheric boundary layer (ABL) studies did not directly incorporate grazing intensity into their design, Type I and Type II statistical errors may introduce significant uncertainties for understanding cause and effect in surface flux dynamics. As a consequence these uncertainties compromise the ability to extrapolate microsite ABL biophysical findings to other spatial and temporal scales.

Carbon and nitrogen mineralization in tallgrass prairie and agricultural soil profiles - Ajwa, H.A.; C. W. Rice; Sotomayor, D. (Soil Science Society of America Journal, 1998)
In situ mineralization of N may contribute significantly to total inorganic-N pools deep in the soil profile. We conducted long-term laboratory incubation experiments to evaluate the net C and N mineralization in soils collected from various depths in tallgrass prairie and agricultural fields of the same geological materials and soil type. Samples were packed to a bulk density of 1.4 g cm-3 in 5-cm-diameter by 10-cm-long cores. The cores were incubated at 35°C for 40 wk in sealed containers. Net C mineralization was measured by evolved CO2, and N mineralized was measured by periodic leaching with NH+4 and NO-3 measured in the leachate. Carbon and N mineralization in the surface horizon were greater in the tallgrass prairie than in the agricultural soil. In both the tallgrass prairie and agricultural soil profiles, C mineralization was least at the water-table depth. Carbon mineralization was described by a first-order kinetic model, but N mineralization was described better by a consecutive (sigmoidal) reaction model. At most depths, the ratios of potentially mineralizable organic C (C0) to total organic C (C0/TOC) and potentially mineralizable organic N (N0) to total N (N0/TN) were greater in the agricultural soil profile than in the tallgrass prairie soil profile. The C0 and N0 in the surface soil (0–0.2 m) represented 11.6 and 12.2% of the total organic C and N pools for the tallgrass prairie soil profile, respectively, and 21.0 and 10.2% of the total organic C and N pools for the agricultural soil profile. Management practices affected the mineralization potentials and rates of both the surface and subsurface soils.
Keywords: tallgrass prairie

Climate change, elevated CO2 and predictive modeling: Past and future climate change scenarios for the tallgrass prairie - Seastedt, T.R.; Hayden, B.P.; Owensby, C.E.; Alan K. Knapp (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Data entry - J. M. Briggs; Benson, B.J.; Hartman, M.; Ingersoll, R. (Data and Information Management in the Ecological Sciences: A Resource Guide, 1998)
One of the many issues that an information management specialist must consider is the need to convert data into a usable electronic format. This frequently means converting data collected in the field, usually on paper, into an electronic form that can then be used in a statistical or graphical package by the researcher. The purpose of this paper is to present guidelines that we have found useful in making this conversion as quick and error-free as possible.

Data management at a long-term ecological research site - J. M. Briggs (Long-Term Ecological Research in the East Asia-Pacific Region: Biodiversity and Conservation of Terrestrial and Freshwater Ecosystems, 1998)

Decomposition and nutrient dynamics of Oak (Quercus spp.) logs after five years of decomposition - Schowalter, T.D.; Zhang, Y.I.; Sabin, T.E. (Ecography, 1998)
Decomposition of oak Quercus spp. logs (25 35 cm diameter, 3 m long) was compared among log substrates in Oregon, Minnesota. Kansas and North Carolina during the first five years on the ground. Decomposition of whole logs (weighted by substrate) averaged 0.069 yr-1 (±0.16 SD). but followed a 2-exponential model (k = 0.12 yr-1 year 1 and k = 0.06 yr -1 years 2 5), reflecting qualitative differences among log substrates (outer and inner bark, sapwood and heartwood). Rapid loss from bark substrates contributed to the initial rapid decay rate. Sapwood decay rate averaged 0.15 yr-1 and dominated the second log decay rate. Heartwood lost only 6% mass during the first five years, for an overall decay rate of 0.012 yr-1 that likely will represent a longer-term third exponential decay rate. Carbon loss amounted to ca 5 kg yr-1 per 170 kg log. Nutrient concentrations generally declined during the first five years, but nitrogen, sulfur, and sodium accumulated in sapwood and heartwood during this period. Sulfur content increased in all substrates and doubled in whole logs during this 5-yr period. Complex patterns of nutrient content suggest patterns of microbial colonization and nutrient utilization. Polynomial models were developed to describe rates of carbon and nutrient flux in log substrates.

Description of the larval stages of Heterosternuta diversicornis (Sharp) Coleoptera: Dytiscidae, Hydroporinae - Alarie, Y.; Fritz, K.M. (Entomologica Scandinavica, 1998)
Description of structures of all three larval instars of Heterosternuta diversicornis (Sharp) is presented. The chaetotaxy and porotaxy of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi are discussed in detail. A close similarity between larvae of H. diversicornis, H. wickhami Zaitzev and H. cocheconis (Fall) is confirmed. All three species distinguish from the closely related species of the genus Neoporus Guignot by (i) a very short and constricted siphon, (ii) the primary setae FE8 and FE9 which are subequal in length to the maximum width of the metafemur (first instar), (iii) the absence of natatory setae on all tibiae and tarsi, and (iv) the contiguous position of the primary setae UR2 and UR3 on the urogomphomere 1.

Determinants of soil CO2 flux from a sub-humid grassland: Effect of fire and fire history - Alan K. Knapp; Conard, S.L.; John M. Blair (Ecological Applications, 1998)
Soil CO2 flux (JCO2) was measured at midday over a 2-yr period in undisturbed tallgrass prairie (Konza Prairie, Kansas, USA) to quantify seasonal and annual budgets, to evaluate temperature and moisture as determinants of soil CO2 flux, and to assess the effect of a common land management tool, spring fire, and fire history on soil respiration. We hypothesized that: (1) maximum rates and annual estimates of soil JCO2 would be greater in more productive burned sites than in unburned sites, (2) soil JCO2 would be greater in newly burned sites with a history of fire exclusion than in annually burned sites (consistent with differences in aboveground production), and (3) soil temperature and water availability would be primary abiotic determinants of soil JCO2 in tallgrass prairie. A preliminary assessment of the effects of large herbivores on soil JCO2 was included to evaluate the hypothesis that removal of aboveground biomass would reduce soil JCO2. Results indicated that spring fire increased maximum monthly soil JCO2 by 20–55% relative to unburned tallgrass prairie, with greatest monthly differences measured in April (fourfold higher in burned sites). In burned sites that differed in fire history, maximum monthly JCO2 in annually burned prairie was 33% greater than in burned sites with a history of fire exclusion. Soil JCO2 in these latter sites was still significantly higher than in unburned sites. Soil JCO2 in sites grazed by bison was reduced by as much as 30% relative to adjacent ungrazed areas. Reduced root biomass and activity in grazed areas, unburned sites, and sites with a history of fire exclusion suggest that plants play a major role in determining soil JCO2 in this grassland. Soil temperature at 5 cm was related strongly to midday JCO2 in both annually burned sites (r2 = 0.58) and unburned sites (r2 = 0.71). In contrast, differences in soil moisture among sites, enhanced by comparing irrigated grassland to control areas, increased maximum monthly JCO2 by only 8%. Thus, soil temperature was the primary abiotic determinant of soil JCO2 during this study. Maximum monthly estimates of soil JCO2 in tallgrass prairie ranged from 10.3 μmol CO2·m−2·s−1 in unburned sites to 15.1 μmol·m−2·s−1 in annually burned irrigated sites, whereas annual estimates varied from 4.7 to 7.8 kg CO2/m2. Over the 2-yr period, spring fire increased estimated annual soil JCO2 by 38–51% relative to unburned sites, while irrigation increased annual soil JCO2 by 13%. These estimates for tallgrass prairie are much higher than those reported for most temperate ecosystems but are similar to estimates for tropical forests. Characteristics of undisturbed tallgrass prairie that may lead to high levels of soil JCO2 include: high above- and belowground productivity; a relatively high proportion of C stored belowground; levels of soil microbial biomass and activity that are among the highest in native ecosystems in the United States; and the lack of a single dominant factor such as temperature, moisture, or nutrient availability, that consistently limits biotic processes during the growing season. The sensitivity of soil JCO2 in tallgrass prairie to different land use practices (fire and grazing) suggests that it is critical to include these factors in the development of grassland C budgets, as well as in regional models that estimate biogeochemical responses to land use change.
Keywords: fire

Disturbance, diversity and species interactions in tallgrass prairie - Scott. L. Collins; Steinauer, E.M. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Diversity of terrestrial macrofauna - D.W. Kaufman; Fay, P.A.; Kaufman, G.A.; Zimmerman, J.L. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

The dynamic tallgrass prairie: Synthesis and research opportunities - Scott. L. Collins; Alan K. Knapp; D.C. Hartnett; J. M. Briggs (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Ecology of arbuscular mycorrhizas in tallgrass prairie - Eom, A.H. (Kansas State University, 1998)

Effect of burning and grazing on carbon and energy fluxes in a tallgrass prairie - D. Bremer (Kansas State University, 1998)
Keywords: tallgrass prairie

The effects of soil disturbances on tallgrass prairie - Rogers, W.E. (Kansas State University, 1998)
Keywords: tallgrass prairie

Evaluation of a digital camera as a low-cost airborne sensor for high spatial resolution remote sensing - Goodin, D.G. (1998)

The evolution of reproduction in trees: Its effect on squirrel ecology and behavior - Smith, C.C. (Ecology and Evolutionary Biology of Tree Squirrels, 1998)

Evolution of the Konza Prairie LTER Information Management System - J. M. Briggs (Data and Information Management in the Ecological Sciences: A Resource Guide, 1998)

The flora of Konza Prairie: A historical review and contemporary patterns - Freeman, C.C. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Fluxes of CO2, water vapor, and energy from a prairie ecosystem during the seasonal transition from carbon sink to carbon source - J.M. Ham; Alan K. Knapp (Agricultural and Forest Meteorology, 1998)
In many temperate-zone ecosystems, seasonal changes in environmental and biological factors influence the dynamics and magnitude of surface-atmosphere exchange. Research was conducted to measure surface-layer fluxes of CO2, water vapor, and energy in a C4-dominated tallgrass prairie during the autumnal transition from carbon sink to carbon source. Data were collected between DOY 220 and 320, 1996 on the Konza Prairie Research Natural Area near Manhattan, KS, USA. Mass fluxes were measured with a tower-based conditional sampling (CS) system, and the surface energy balance was measured with Bowen ratio (BR) methods. Soil-surface CO2 fluxes were measured with a closed-chamber system. Carbon and energy fluxes decreased over the study period as the canopy senesced. When skies were clear, daily net CO2 exchange (NCE) varied from a maximum gain of 17.8 g CO2 m−2 day−1 on DOY 226 to a maximum loss of −10.3 g CO2 m−2 day−1 on DOY 290. Over the 100-day study period, the ecosystem had a net loss of −217 g CO2 m−2, with the change from sink to source occurring on about DOY 255. Soil-surface CO2 fluxes were −0.4 mg CO2 m−2 s−1 at the start of the study but declined to −0.04 mg CO2 m−2 s−1 on DOY 320. The Bowen ratio increased from 0.5 to 4 over the study period. The seasonal trend in NCE was governed by the senescence of the canopy and not abrupt changes in weather. Senescence also influenced canopy conductance, which caused a seasonal transformation in the surface energy balance. Data suggest that any climatic or management factors that affect the rate and timing of the autumnal sink-source transition can have a strong influence, on the carbon and water balance in the ecosystem.
Keywords: Carbon sink-source transition; Seasonal variation; Surface-atmosphere exchange; Tallgrass prairie ecosystem

Geomorphology of the Konza Prairie - Oviatt, C.G. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie - Alan K. Knapp; J. M. Briggs; D.C. Hartnett; Scott. L. Collins (Oxford University Press, 1998)
Keywords: tallgrass prairie

Grasslands, Konza Prairie and long-term ecological Research - Alan K. Knapp; Seastedt, T.R. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Hybridization of Mountain Bluebird and Eastern Bluebird in Northeastern Kansas - Cavitt, J.F.; Pearse, A.T.; Rintoul, D.A. (Kansas Ornithological Society, 1998)

Hydrology and aquatic chemistry - Gray, L.J.; G. L. Macpherson; Koelliker, J.K.; W. K. Dodds (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Influence of maternal diet and perishability on caching and consumption behavior of juvenile eastern woodrats - Post, D.M.; McDonald, M.W.; Reichman, O.J. (Journal of Mammalogy, 1998)
We tested the hypotheses that juvenile eastern woodrats (Neotoma floridana) learned to select appropriate foods to cache by cues from the maternal diet and that the effect of perishability affected caching and consumption behavior of juvenile woodrats. In May 1993, female woodrats were mated and placed on a diet of garlic-flavored chow. Females in group A were fed garlic-flavored chow until offspring were weaned. Females in group B were fed garlic-flavored chow until parturition and then were placed on a diet of standard laboratory chow. All offspring were weaned at 45 days postpartum and maintained on a diet of standard laboratory chow. In October and November 1993, juveniles were tested to determine their preference for caching and consumption of garlic-flavored chow or a novel (mint) flavored chow. Juveniles in group A cached more garlic-flavored chow than juveniles in group B (P = 0.04). There was no difference between groups in the amount of garlic chow consumed (P = 0.5). Naive juveniles preferred to cache dry apple (P = 0.01) but preferred to consume fresh apple (P = 0.01). The outcome of our experiments suggests that maternal diet influences the cache-food selection of naive woodrats. Further, naive juvenile woodrats treat perishable and non-perishable foods in a manner similar to adults suggesting that their response to such foods is not learned.
Keywords: caching; diet; juveniles; learning; Neotoma floridana; woodrats

Interspecific variation in plant responses to mycorrhizal colonization in prairie grasses and forbs - G.T. Wilson; D.C. Hartnett (American Journal of Botany, 1998)

Landcover patterns in tallgrass prairie: interactions of abiotic factors and land management practices - Rieck, D.R. (Kansas State University, 1998)
Keywords: tallgrass prairie

A landscape perspective of patterns and processes in tallgrass prairie - J. M. Briggs; Nellis, M.D.; Turner, C.L.; Henebry, G.M.; Su, H. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Is leaf-level photosynthesis related to plant success in a highly productive grassland? - McAllister, C.A.; Alan K. Knapp; Maragni, L.A. (Oecologia, 1998)
We addressed the question: “Are short-term, leaf-level measurements of photosynthesis correlated with long-term patterns of plant success?” in a productive grassland where interspecific competitive interactions are important. To answer this question, seasonal patterns of leaf-level photosynthesis were measured in 27 tallgrass prairie species growing in sites that differed in species composition and productivity due to differences in fire history. Our specific goals were to assess the relationship between gas exchange under field conditions and success (defined as aerial plant cover) for a wide range of species, as well as for these species grouped as dominant and sub-dominant grasses, forbs, and woody plants. Because fire increases productivity and dominance by grasses in this system, we hypothesized that any relationship between photosynthesis and success would be strongest in annually burned sites. We also predicted that regardless of fire history, the dominant species (primarily C4 grasses) would have higher photosynthetic rates than the less successful species (primarily C3 grasses, forbs and woody plants). Because forbs and woody species are less abundant in annually burned sites, we expected that these species would have lower photosynthetic rates in annually burned than in infrequently burned sites. As expected, the dominant C4␣grasses had the highest cover on all sites, relative to␣other growth forms, and they had the highest maximum and seasonally averaged photosynthetic rates (17.6 ± 0.42 μmol m−2 s−1). Woody species had the lowest average cover as well as the lowest average photosynthetic rates, with subdominant grasses and forbs intermediate in both cover and photosynthesis. Also as predicted, the highest overall photosynthetic rates were found on the most productive annually burned site. Perhaps most importantly, a positive relationship was found between leaf-level photosynthesis and cover for a core group of species when data were combined across all sites. These data support the hypothesis that higher instantaneous rates of leaf-level photosynthesis are indicative of long-term plant success in this grassland. However, in contrast to our predictions, the subdominant grasses, forbs and woody species on the annually burned site had higher photosynthetic rates than in the less frequently burned sites, even though their average cover was lower on annually burned sites, and hence they were less successful. The direct negative effect of fire on plant cover and species-specific differences in the availability of resources may explain why photosynthesis was high but cover was low in some growth forms in annually burned sites.
Keywords: Competition; grassland; photosynthesis; Plant cover; tallgrass prairie

Long-term ecological consequences of varying fire frequency in a humid grassland - Alan K. Knapp; John M. Blair; J. M. Briggs (Fire in Ecosystem Management: Shifting The Paradigm From Suppression to Prescription, 1998)
Keywords: fire

Modulation of diversity by grazing and mowing in native tallgrass prairie - Scott. L. Collins; Alan K. Knapp; J. M. Briggs; John M. Blair; Steinauer, E.M. (Science, 1998)
Species diversity has declined in ecosystems worldwide as a result of habitat fragmentation, eutrophication, and land-use change. If such decline is to be halted ecological mechanisms that restore or maintain biodiversity are needed. Two long-term field experiments were performed in native grassland to assess the effects of fire, nitrogen addition, and grazing or mowing on plant species diversity. In one experiment, richness declined on burned and fertilized treatments, whereas mowing maintained diversity under these conditions. In the second experiment, loss of species diversity due to frequent burning was reversed by bison, a keystone herbivore in North American grasslands. Thus, mowing or the reestablishment of grazing in anthropogenically stressed grasslands enhanced biodiversity.
Keywords: tallgrass prairie

Nitrate loading of shallow ground water, prairie vs. cultivated land, northeastern Kansas, USA - G. L. Macpherson (A.A. Balkema, 1998)

Nitrogen cycling in tallgrass prairie soils - Dell, C.J. (Kansas State University, 1998)
Keywords: tallgrass prairie

Nutrient and energetic characteristics of grasshoppers of different life stages - Robel, R.J.; Desjardins, C.A.; Kemp, K.E. (The Prairie Naturalist, 1998)

Patterns and controls of aboveground net primary production in tallgrass prairie - Alan K. Knapp; J. M. Briggs; John M. Blair; Turner, C.L. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Permutation of two-term local quadrat variance analysis: general concepts for interpretation of peaks - Campbell, J.E.; Franklin, D.J.G.; Newman, J.A. (Journal of Vegetation Science, 1998)
Many ecological studies use Two-Term Local Quadrat Variance Analysis (TTLQV) and its derivatives for spatial pattern analysis. Currently, rules for determining variance peak significance are arbitrary. Variance peaks found at block size 1 and at > 50 % of the transect length are the only peaks whose use is explicitly prohibited. Although the use of variance peaks found at block sizes > 10 % of the transect length have also been warned against, many researchers interpret them regardless. We show in this paper that variance peaks derived from TTLQV are subject to additional ‘rules of thumb’. Through the use of randomization and permutation analyses on real and simulated data of species abundance in contiguous plots along a single transect, we show that variance peaks found at block sizes 1, 2 and 3 occur frequently by chance and thus likely do not indicate biologically meaningful patterns. The use of multiple replicate transects decreases the probability of Type II error.
Keywords: Permutation analysis; Spatial pattern; Variance peak

Plant populations: Patterns and processes - D.C. Hartnett; Fay, P.A. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

The pollination biology of the genus penstemon (Scrophulariaceae) in the tallgrass prairie - Clinebell, R.R. II. (Saint Louis University, 1998)
The pollination ecology of six taxa of prairie species of Penstemon (Scrophulariaceae) was studied on eight sites in Illinois, Kansas and Missouri. These sites span much of the floristic and ecological diversity contained in the tallgrass prairie of the central United States
Keywords: tallgrass prairie

A portable chamber for in situ determination of benthic metabolism - W. K. Dodds; Brock, J. (Freshwater Biology, 1998)
1. Many stream ecologists are interested in determining the metabolic rates of benthic organisms, particularly those of production and respiration. It is often necessary to make these measurements on fresh material in the field at remote sites. Recirculating chambers are commonly used for this purpose. 2. A broad variety of recirculating chambers are described in the literature, but each design has inherent limitations. The most common are inability to control flow in the chamber and match it with external flow rates, and a lack of the power required to do this for extended periods. Alteration of spectral irradiance, temperature rise and elevated internal chamber pressures are additional limitations that have received little attention. 3. We have designed and constructed a flow chamber that eliminates some of these problems. The chamber utilizes a DC motor-driven propeller as an efficient recirculator (axial impeller), minimizing power requirements and it is constructed of UVB transparent acrylic to allow a full spectral complement of solar irradiance in the interior. Modular components allow the chamber to be taken apart quickly for cleaning and replacement of parts, making it more functional than some previous designs. 4. The axial impeller chamber was compared to a similar sized conventional chamber that had a small diameter return line and a high capacity centrifugal pump. The axial impeller chamber had less of a temperature rise during field incubations, lower power consumption and less internal pressure in the return line when producing equivalent water velocities. 5. The reported axial impeller design had relatively homogeneous velocity across the working section relative to other chambers and was capable of water velocities in excess of 1 m s–1.

Regional climate and the distribution of tallgrass prairie - Hayden, B.P. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Responses of soil respiration to clipping and grazing in a tallgrass prairie - D. Bremer; J.M. Ham; Owensby, C.E.; Alan K. Knapp (Journal of Environmental Quality, 1998)
Soil-surface CO2 flux (Fs) is an important component in prairie C budgets. Although grazing is common in grasslands, its effects on Fs have not been well documented. Three clipping treatments: (i) early-season clipping (EC); (ii) full-season clipping (FC); and (iii) no clipping (NC); which represented two grazing strategies and a control, were applied to plots in a tallgrass prairie in northeastern Kansas, USA. Measurements of Fs were made with a portable gas-exchange system at weekly to monthly intervals for 1 yr. Concurrent measurements of soil temperature and volumetric soil water content at 0.1 m were obtained with dual-probe heat-capacity sensors. Measurements of Fs also were obtained in grazed pastures. Fs ranged annually from 8.8 × 10−3 mg m−2 S−1 during the winter to 0.51 mg m−2 s−1 during the summer, following the patterns of soil temperature and canopy growth and phenology. Clipping typically reduced Fs 21 to 49% by the second day after clipping despite higher soil temperatures in clipped plots. Cumulative annual Fs were 4.94, 4.04, and 4.11 kg m−2 yr−1 in NC, EC, and FC treatments, respectively; thus, dipping reduced annual Fs by 17.5%. Differences in Fs between EC and FC were minimal, suggesting that different grazing strategies had little additional impact on annual Fs. Daily Fs in grazed pastures was 20 to 37% less than Fs in ungrazed pastures. Results suggest that grazing moderates Fs during the growing season by reducing canopy photosynthesis and slowing translocation of carbon to the rhizosphere.
Keywords: tallgrass prairie

Responses to short-term shade in soybean leaves: Effects of leaf position and drought stress - Fay, P.A.; Alan K. Knapp (International Journal of Plant Science, 1998)
This study examined how leaf position in the canopy affected photosynthetic and stomatal responses to short-term, minutes-long shade periods during a drought cycle in soybean (Glycine max [L.] Merr.). All soybean leaves had similar basic responses to short-term shade, including rapidly decreased photosynthetic rates (Aco2 ), slower decreases in stomatal conductance (g,), and delayed stomatal reopening and photosynthetic recovery after leaves were reilluminated. Drought stress lowered overall Aco2 and restricted photosynthetic and stomatal responses to short-term shade with the negative effects of drought being stronger in lower than in upper leaves. Some of the negative effects of drought persisted after drought was relieved, causing reduced overall water use efficiency, especially in lower leaves. These results indicate that leaf position effects on stomatal responses to short-term shade events become important during and after stress.

The role of food supply and nest predation in limiting reproductive success of Brown Thrashers (Toxostoma rufum ) : Effects of predator removal, food supplements and predation risk - Cavitt, J.F. (Kansas State University, 1998)

The role of mycorrhizae and dominant competitors in tallgrass prairie plant community structure and belowground processes - M.D. Smith (Kansas State University, 1998)
Keywords: tallgrass prairie

Seasonality of finely-resolved spatial structure of NDVI and its component reflectances in tallgrass prairie - Goodin, D.G.; Henebry, G.M. (International Journal of Remote Sensing, 1998)
Grass canopies exhibit distinct seasonality in reflectance and spatial patterns in reflectance result from landscape heterogeneity. To investigate the spatial structure of NDVI and its two component reflectances at fine resolution in burned and unburned tallgrass prairie, we use range and relative nugget effect two indicators of spatial structure derived from semivariograms. Results show that spatial dependence of the three spectral measures are similar in the early season when the litter layer has been removed by burning and again in the later season when the canopy is senescent. However, as the canopy develops, the spatial dependence of NDVI deviates from that of its component reflectances. In the unburned canopy, red reflectance appears to strongly influence the spatial pattern of NDVI. In the burned canopy, neither component reflectance strictly determines the spatial pattern of NDVI. Maximum divergence in spatial pattern between NDVI and its components coincides with minimum available moisture, suggesting a relation between moisture stress and spatio-spectral heterogeneity.
Keywords: tallgrass prairie

Sodium Accumulation and Genesis of Polygenetic Soils in Northcentral Kansas - Glaze, S.L. (Kansas State University, 1998)

Soil and microbial responses in tallgrass prairie to elevated CO2 - Williams, M.A. (Kansas State University, 1998)
Keywords: tallgrass prairie

Soils and soil biota - Ransom, M.D.; C. W. Rice; Todd, T.C.; Wehmueller, W.A. (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

Structure and dynamics of aquatic communities - Gray, L.J.; W. K. Dodds (Grassland Dynamics: Long-Term Ecological Research in Tallgrass Prairie, 1998)
Keywords: tallgrass prairie

The structure of mammalian faunas in the New World: from continents to communities - Kaufman, D.M. (University of New Mexico, 1998)

Suggested classification for stream trophic state: Distributions of temperate stream types by chlorophyll, total nitrogen and phosphorus - W. K. Dodds; Jones, J.R.; Welch, E.B. (Water Research, 1998)
Aquatic scientists and managers have no conventional mechanism with which to characterize and compare nutrients and algal biomass in streams within a broader context analogous to trophic state categorization in lakes by chlorophyll (chl) and nutrients. We analyzed published data for a large number of distinct, temperate, stream sites for mean benthic chl (n=286), maximum benthic chl (n=176), sestonic chl (n=292), total nitrogen (n=1070), and total phosphorus (n=1366) as a first effort to establish criteria for trophic boundaries. Two classification systems are proposed. In the first system, the boundary between oligotrophic and mesotrophic categories is defined by the lower third of the cumulative distribution of the values. The mesotrophic–eutrophic boundary is defined by the upper third of the distribution. In the second system, individual streams are placed more precisely in a broad geographic context by assessing the proportion of streams that have greater or lesser nutrient and chl values. The proposed relationships for streams were compared to trophic criteria published for lakes. The proposed trophic boundaries for streams generally include a broader range of values in the mesotrophic range than conventional criteria for lakes. The ratio of maximum to mean benthic chl for streams was significantly higher than that found for planktonic chl in lakes, reflecting the greater variance in streams. This high variance in streams suggests that the proposed stream trophic criteria should be viewed only as a general first approach to categorizing stream ecosystems.
Keywords: Chlorophyll; eutrophic; mesotrophic; nitrogen; nutrients; oligotrophic; periphyton; Phosphorus; rivers; streams

Terrestrial nutrient cycling in tallgrass prairie - John M. Blair; Seastedt, T.R.; C. W. Rice; Ramundo, R.A. (Grassland Dynamics: Long-term Ecological Research, 1998)
Keywords: tallgrass prairie

Variability in leaf optical properties among 26 species from a broad range of habitats - Alan K. Knapp; Carter, G.A. (American Journal of Botany, 1998)
Leaves from 26 species with growth forms from annual herbs to trees were collected from open, intermediate, and shaded understory habitats in Mississippi and Kansas, USA. Leaf optical properties including reflectance, transmittance, and absorptance in visible and near infrared (NIR) wavelengths were measured along with leaf thickness and specific leaf mass (SLM). These leaf properties and internal light scattering have been reported to vary with light availability in studies that have focused on a limited number of species. Our objective was to determine whether these patterns in leaf optics and light availability were consistent when a greater number of species were evaluated. Leaf thickness and SLM varied by tenfold among species sampled, but within-habitat variance was high. Although there was a strong trend toward thicker leaves in open habitats, only SLM was significantly greater in open vs. understory habitats. In contrast, leaf optical properties were strikingly similar among habitats. Reflectance and reflectance/transmittance in the NIR were used to estimate internal light scattering and there were strong relationships (r1 > 0.65) between these optical properties and leaf thickness. We concluded that leaf thickness, which did not vary consistently among habitats, was the best predictor of NIR reflectance and internal light scattering. However, because carbon allocation to leaves was lower in understory species (low SLM) yet gross optical properties were similar among all habitats, the energy investment by shade leaves required to achieve optical equivalence with sun leaves was lower. Differences in leaf longevity and growth form within a habitat may help explain the lack of consistent patterns in leaf optics as the number of species sampled increases.

Variability of spectral reflectance and vegetation indices in tallgrass prairie: spatio-temporal analysis using semivariograms and close-range remote sensing - Goodin, D.G.; Henebry., G.M. (1998)
The effects of fire and other disturbances on spatial patterning of vegetation in tallgrass prairie has been extensively studied using remote sensing. Data used in these studies is frequently typically collected from operational remote sensing satellites with spatial resolution coarse relative to the grassland canopy. The authors use semivariograms calculated from close range remote sensing instruments to investigate the spatial structure of spectral reflectance and vegetation indices in tallgrass prairie at finer spatial resolution more appropriate to the developing canopy. Data were collected at the Konza Prairie Research Natural Area near Manhattan, KS. Two watersheds were surveyed; one unburned the other burned just prior to data collection. Spatial dependence and anisotropy for three spectral bands (TM3, TM4, and TM5) and two vegetation indices (NDVI, NDVIc) were calculated for three dates distributed throughout the 1997 growing season. Results show that both anisotropy and dominant scale of spatial dependence vary seasonally and across spectral region

Advantages of principal components analysis for land cover segmentation from SAR image series - Henebry, G.M. (ESA, 1997)

Avian community responses to fire, grazing and drought in the tallgrass prairie - Zimmerman, J.L. (Ecology and Conservation of Great Plains Vertebrates, 1997)
Vegetation typical of the tallgrass prairie occurs east of the Great Plains in bottomland “openings” and as small “glades” or “balds” within the eastern deciduous forest. West of the Mississippi River, however, coverage by tallgrass prairie expands with the increasingly greater aridity under the deepening rainshadow of the western mountains. Along the Kansas-Missouri border on the western fringe of the deciduous forest, prairie is present across 50–80% of the region (Schroeder 1983). Forested area within this prairie-forest mosaic continues to diminish, decreasing to as little as 7% in the Flint Hills Uplands (Knight et al. 1994). The portion of the Great Plains characterized by the tallgrass prairie community exists in a climate that allows the development of forest as a bordering “gallery” along stream courses. These naturally occurring forest fragments, these island remnants of the continental forest to the east, remain an integral aspect of the tallgrass prairie landscape, contributing a disproportionately greater component, considering the small extent of their coverage, to the regional avian species richness (Faanes 1984, Zimmerman 1993).
Keywords: tallgrass prairie

A case of senescence for the white-footed mouse? - McMillan, B.R.; Kaufman, G.A.; D.W. Kaufman (The Southwestern Naturalist, 1997)

Comparative ecology of native and introduced ungulates - D.C. Hartnett; Steuter, A.A.; Hickman, K.R. (Ecology and Conservation of Great Plains Vertebrates, 1997)
The defining period of coevolution among Great Plains plant and ungulate species occurred during the past 12,000 years (Mack and Thompson 1982, Axelrod 1985). In the late Pleistocene and early Holocene, a diverse array of large grazers and browsers were reduced to a much smaller group of ungulate species represented by bison (Bison bison), pronghorn (Antilocapra americana), deer (Odocoileus hemionus and O. virginianus), and elk (Cervus canadensis). These changes occurred in the presence of nomadic humans from the Asian steppe who were immigrating to the Great Plains during the same time. The landscape was characterized by gently rolling interfluvial surfaces covered with perennial herbaceous vegetation. These exposed grasslands were periodically interrupted by more protected wetland, riparian woodland, or scarp woodland habitats. Although wetlands and woodlands occupied less than 7 and less than 3% of the Great Plains, respectively (National Wetlands Inventory, and Nebraska Natural Heritage Program data bases), the heterogeneity that they created at landscape scales played a major role in determining the distribution and abundance of native ungulates. Extreme cold and heat, drought, flood, fire, wind, and countless biotic interactions caused locally short-term fluctuations in ungulate populations and long-term shifts in landscape features. These dynamic temporal changes were overlayed on a multi-scale spatial mosaic. Native ungulates were adapted to this landscape.

Contingent effects of plant species on soils along a regional moisture gradient in the Great Plains - Vinton, M.A.; Burke, I.C. (Oecologia, 1997)
The central grassland region of the United States encompasses major gradients in temperature and precipitation that determine the distribution of plant life forms, which in turn may influence key ecosystem processes such as nutrient cycling and soil organic matter dynamics. One such gradient is the threefold increase in precipitation from the eastern Colorado shortgrass-steppe, in the rain shadow of the Rocky Mountains, to the tallgrass prairie in eastern Kansas. We investigated the relative roles of plant species and plant cover in influencing soil C and N cycling in three sites along this gradient. Plant cover (i.e., the presence or absence of an individual plant) was relatively more important than plant species in explaining variability in soil properties at the dry site, the Central Plains Experimental Range in␣northeastern Colorado. However, plant species explained relatively more of the variability in soil properties than did plant cover at the two wetter sites, Hays and Konza, in central and eastern Kansas. The wetter sites had more continuous plant cover, resulting in less plant-cover-induced variation in soil C and N, than did the dry site, which had distinct patches of bare ground. Plant species at the wetter sites had higher and more variable levels of tissue C:N than plant species at the dry site, due to both within species changes and changes in species composition. Aboveground tissue C:N was better correlated with net nitrogen mineralization rates at the wet sites than the dry site. Thus, tissue chemistry appears to exert more control on nitrogen dynamics at the wet than the dry sites. The results suggest that plant species traits that are relevant to nutrient cycling (e.g., tissue C:N ratios, spatial patterns, productivity) reflect environmental limitations as well as species' physiological potentials. Furthermore, a dominant environmental driver such as precipitation may ameliorate or exaggerate the importance of individual species traits for nutrient cycling.
Keywords: grassland; Litter quality; Plant-soil interactions; Soil carbon; Soil nitrogen

The contribution of drought-related decreases in foliar nitrogen concentration to decreases in photosynthetic capacity during and after drought in prairie grasses - Heckathorn, S.A.; DeLucia, E.H.; Zielinski, R.E. (Physiologia Plantarum, 1997)
While stomatal closure usually limits photosynthesis during drought, our previous results suggest that drought-related decreases in foliar nitrogen concentration (NL) limit photosynthesis during recovery from drought in prairie grasses. Here we estimate the importance of decreases in NL to decreased photosynthetic capacity (PScap) during drought and a subsequent recovery period in three perennial C4 prairie grasses. PScap (O2 evolution at light and CO2 saturation) decreased 69 to 78% during drought in these grasses, and full recovery of PScap required 8 to 12 days, until younger leaves were expanded or older leaves were repaired, depending on species. Decreases in NL explained 38 to 51% of the loss of PScap during drought and accounted for 51 to 69% of the total loss of PScap integrated over the post-drought recovery period. N-related loss of PScap appeared to result more from decreases in ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), phosphoenolpyruvate carboxylase (4.1.1.31), and other soluble photosynthetic enzymes, than from decreases in thylakoid N-containing compounds. Decreases in quantum yield of O2 evolution and Fv/Fm (variable-to-maximum fluorescence of dark-adapted leaves) during drought were small, so we assumed that little damage to photsystem II (PSII) and thylakoid membrane function occurred. Further, F0 (minimum F) decreased or remained unchanged, dark F0 was greater than light F0, and decreases in photochemical quenching (the fraction of oxidized PSII) were reversed within 1–3 days after drought. Therefore, prolonged increases in non-photochemical quenching (qn; thermal dissipation of excess light energy) during and after drought were indicative of protective downregulation and were likely associated with disproportionate loss of soluble photosynthetic proteins during drought. In support of this, post-drought recovery of qn paralleled recovery of NL and PScap. Thus, in C4 prairie grasses, loss of PScap during drought is largely the result of decreases in shoot NL and of associated protective downregulation, decreasing carbon assimilation for 1–2 weeks after drought.
Keywords: Drought; nitrogen; photosynthesis; prairie grasses; water stress

Detecting fire and grazing patterns in tallgrass prairie using spectral mixture analysis - Wessman, C.A.; Bateson, C.A.; Benning, T.L. (Ecological Applications, 1997)
Global grasslands are typically under management practices (such as fire and grazing) that alter nutrient cycling, ecosystem composition, and distribution of organic matter from the unmanaged condition. We evaluated landscape-level response to fire and grazing treatments in the Konza Tallgrass Prairie Research Natural Area, Kansas, using spectral mixture analysis of Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data acquired 31 August 1990. Spectral mixture analysis derives the fractional abundances of spectrally unique components in the landscape. The reflectance spectra of these components are called endmembers. Endmember fractions values were compared against ground values of live biomass, current standing dead biomass, and litter for 12 watersheds. Analysis of variance (ANOVA) was performed on 37 watersheds with known burning and grazing histories for each of the remote sensing variables. Seven endmembers were selected from the AVIRIS data using a manual endmember selection method: nonphotosynthetic vegetation (NPV), soil, rock, shade, and three green vegetation endmembers (GV1, GV2, and GV3). Each vegetation endmember correlated differently to biomass measurements and revealed unique relationships to management treatments. From regressions, ANOVAs, and image analysis, these three endmembers were inferred to represent canopy vertical structure or leaf area index (LAI), greenness, and fractional cover of grass, respectively. There was a stronger relationship between the sum of GV1 and GV3 fractions and live grass biomass values than there was with the (unsummed) individual fractions. In an ANOVA, the sum separated both burn and grazing treatments as well as the treatment interaction. The NPV fraction was strongly correlated with ground measurements of litter and standing dead biomass, and significantly separated burn treatments. The soil fraction differentiated grazing treatments, and analysis of the soil fraction image revealed a spatial coherence of grazing patterns along drainages. Similar analyses were perfomed on the Normalized Difference Vegetation Index (NDVI), a commonly used two-band index computed from red and near-infrared reflectance. NDVI, shown in previous studies to estimate the fraction of photosynthetically active radiation absorbed by green vegetation (FPAR), was a poor indicator of canopy biomass, but it successfully separated fire treatments. Broad-scale assessment of the state and structure of managed grassland systems requires the identification of several indicator variables. Spectral mixture analysis, unlike NDVI, not only separated treatments but also allowed for the identification of five remotely sensible factors affected by the management treatments, namely, vertical structure, percentage cover or patchiness, greenness, and distribution of soil and litter.
Keywords: tallgrass prairie

Distribution of runoff and rivers related to vegetative characteristics, latitude, and slope: A global perspective - W. K. Dodds (Journal of the North American Benthological Society, 1997)
The geographic distribution of streams on earth can be associated with terrestrial vegetation, slope, and latitude, among other factors. Classifying flowing water habitats by associated vegetative cover is useful because factors such as downstream transport of organic carbon (C), sediments, nutrients, and other dissolved or suspended materials are influenced heavily by the vegetative characteristics of the watershed. Global datasets with 1-degree spatial resolution were analyzed to characterize both volume of runoff and number of mapped rivers associated with each of 14 classes of vegetation, and how runoff is influenced by latitude and slope. The vegetation classes (land cover) were ranked in decreasing order with respect to runoff. About 30% of the global runoff originates from broadleaf evergreen forest, followed by wooded C4 grassland (14.8%), cultivated land (8.9%), coniferous forest and woodland (8.3%), ice (7.8%), wooded C3 grassland (6.0%), mixed coniferous and broadleaf deciduous forest (5.4%), C3 grassland (5.3%), tundra (4.5%), high latitude deciduous forest and woodland (3.9%), broadleaf deciduous forest and woodland (2.3%), C4 grassland (1.7%), shrubs and bare ground (1.4%), and desert and bare ground (0.5%). Numbers of mapped rivers followed a similar pattern, except that broadleaf evergreen forests did not dominate, and tundra habitats were much more important. Counts of intermittent rivers were generally highest in the areas with the lowest runoff. River counts are likely to be less reliable than runoff estimates because they rely upon the subjective judgment of cartographers. Equatorial and northern temperate regions accounted for the greatest proportion of total runoff. A weak positive relationship occurred between slope and runoff. This analysis may assist investigators in determining how well their results can be extrapolated beyond regional scales.
Keywords: rivers; Runoff; streams; Terrestrial systems; vegetation

Ecology of small mammals in prairie landscapes - Kaufman, G.A.; D.W. Kaufman (Ecology and Conservation of Great Plains Vertebrates, 1997)
When one crosses the prairie landscapes of central North America, one becomes aware of the impacts that humans have had on the region. Recent anthropogenic modifications of the presettlement prairie not only have changed vegetation but also altered distributional ranges, spatial use within ranges, and total numbers of many species of animals. Although human activities often reduce ranges and abundances of animals and these reductions usually are the foci of issues of conservation, human impacts do not always lead to such reductions. Anthropogenic changes can and do lead to increases in numbers, distributional ranges, or both for some species. Some of these increases result from altered landscapes that provide conditions more suitable for some species than the conditions available in native environments. Other increases are due to intentional introductions of both domestic and wild species and to accidental introductions of wild species.

Ecophysiology and demography of Yucca glauca in the central Great Plains - Maragni, L.A. (Kansas State University, 1997)
Keywords: Ecophysiology

Effects of bison and cattle on growth, reproduction, and abundances of five tallgrass prairie forbs - Damhoureyeh, S.A.; D.C. Hartnett (American Journal of Botany, 1997)
Forb populations were sampled on Kansas tallgrass prairie to examine the effects of native (bison) and domestic (cattle) ungulates on plant growth, reproduction, and species abundances. Five locally and regionally abundant native tallgrass prairie perennials, Baptisia bracteata, Oenothera speciosa, Vernonia baldwinii, Solidago missouriensis, and Salvia azurea, were selected for study. Replicate watershed-level treatments included three grazing regimes (ungrazed, grazed by cattle, and grazed by bison), and two spring fire frequencies (annually burned and burned at 4-yr intervals). The results show that forb responses to ungulates in tallgrass prairie are complex and vary significantly among plant species, ungulate species, fire regimes, and plant life history stages. Some forbs (e.g., B. bracteata, O. speciosa, and V. baldwinii) increased in growth and reproduction in grazed sites, indicating competitive release in response to selective grazing of the dominant warm-season matrix grasses. Forbs that reduced performance in grazed sites are likely negatively affected by disturbances generated by ungulate nongrazing activities, because none of the forbs studied were directly consumed by bison or cattle. Large grazers had no detectable effect on the frequency of plant damage by other herbivores or pathogens. Significant effects of grazers on patterns of flowering and seed production were not congruent with their effects on population densities, indicating that variation in sexual reproduction plays a minor role in regulating local population abundances. Furthermore, the native and domestic ungulates differ significantly in their effects on forb growth and reproduction.
Keywords: tallgrass prairie

Effects of fire, mowing and nitrogen additions on root characteristics in tallgrass prairie - Benning, T.L.; Seastedt, T.R. (Journal of Vegetation Science, 1997)
Root harvests and root windows were used to study the influence of fire, mowing and nitrogen additions on root lengths, biomass, and nitrogen content in tall-grass prairie. Four years of nitrogen additions (10 g m2 yr−1) increased below-ground mass by 15 % and nitrogen concentration in that mass by 77 %. In general, live roots and rhizomes exhibited greater increases in nitrogen concentrations than detrital roots and rhizomes. After four years of treatment, live roots and rhizomes immobilized an additional 1.5 to 5 g/m2 of nitrogen, depending upon specific treatment, while dead roots and rhizomes immobilized an additional 3 to 3.5 g/m2. Average root growth parameters, as measured with root windows, were positively correlated with above-ground peak foliage biomass; however, the only significant correlation was between average new root growth and above-ground peak foliage biomass (r = 0.73, p ≤ 0.04). Root growth and decay, as measured by annual mean values for eight root windows over a four year interval, were insensitive to climatic and treatment effects.
Keywords: Below-ground Biomass; Rhizome; Root growth; Root window

Effects of mycorrhizae on plant productivity and species abundances in tallgrass prairie microcosms - G.T. Wilson; D.C. Hartnett (American Journal of Botany, 1997)
Experimental microcosms (40 X 52 X 32 cm) containing an assemblage of eight tallgrass prairie grass and forb species in native prairie soil were maintained under mycorrhizal (untreated control) or mycorrhizal-suppressed (fungicide-treated) conditions to examine plant growth, demographic, and community responses to mycorrhizal symbiosis. The fungicide benomyl successfully reduced mycorrhizal root colonization in the fungicide-treated microcosms to only 6.4% (an 83% reduction relative to mycorrhizal controls). Suppression of mycorrhizas resulted in a 31% reduction in total net aboveground plant production and changes in the relative production of C4 and C3 plants. The C4 tallgrasses Andropogon gerardi and Sorghastrum nutans produced less plant biomass in the fungicide-treated microcosms, and had a greater ratio of reproductive to vegetative biomass. Cool-season C3 grasses, Koeleria pyramidata and Poa pratensis accumulated more biomass and were a significantly greater proportion of total community biomass in mycorrhizal-suppressed microcosms. Forbs showed variable responses to mycorrhizal suppression. The two legumes Amorpha canescens and Dalea purpurea had significantly lower survivorship in the fungicide-treated microcosms, relative to the controls. The results confirm the high mycorrhizal dependency and growth responsiveness of dominant prairie grasses, and indicate that differential growth and demographic responses to mycorrhizal colonization among species may significantly affect plant productivity and species relative abundances in tallgrass prairie
Keywords: tallgrass prairie

The effects of natural disturbances on lotic fauna of a pristine tallgrass prairie stream - Fritz, K.M. (Kansas State University, 1997)
Keywords: tallgrass prairie

Effects of organismal and distance scaling on analysis of species distribution and abundance - Scott. L. Collins; Glenn, S.M. (Ecological Applications, 1997)
As communities and populations become increasingly fragmented, much theoretical and some empirical research has focused on the dynamics of metapopulations. Many metapopulation models describe dynamics among populations in a region, yet the scale of the region to which different models apply often is undefined. Because the spatial scale is undefined, testing predictions and assumptions of these models is problematic. Our goal is to present two scaling concepts relevant to these models, distance scaling and organismal scaling, and to apply these scaling notions to patterns of species distribution. To determine distance effects, we analyzed patterns of distribution of four taxonomic groups in tallgrass prairie (grasshoppers, small mammals, vascular plants, and breeding birds) at two spatial scales. To asses organismal effects, we held spatial scale constant and we compared patterns of distribution and abundance among these taxonomic groups. Using long—term data from Konza Prairie, Kansas, there were significant differences in the pattern of distribution of grasshoppers, small mammals, vascular plants, and breeding birds within a single spatial scale. The number of core species (species occupying >90% of the sites in a region) of plants and birds was less than the number of satellite species (those occupying <10% of the sites in a region). The opposite was true for grasshoppers and small mammals. All four distribution patterns were significantly nonrandom, but only grasshoppers and small mammals were significantly bimodal at this scale. Plants and birds were unimodal. The patterns of distribution within these taxonomic groups at two spatial scales were significantly different as well. In all cases, the percentage of species in the core group declined, and the percentage of species in the satellite group increased as spatial scale increased. These results demonstrate the difficulty of testing theoretical models with only one taxonomic group at a single spatial scale. One should not accept or reject a model until the spatial domains of organismal and distance scaling have been properly evaluated. As communities and populations become increasingly fragmented, much theoretical and some empirical research has focused on the dynamics of metapopulations. Many metapopulation models describe dynamics among populations in a region, yet the scale of the “region” to which different models apply often is undefined. Because the spatial scale is undefined, testing predictions and assumptions of these models is problematic. Our goal is to present two scaling concepts relevant to these models, distance scaling and organismal scaling, and to apply these scaling notions to patterns of species distribution. To determine distance effects, we analyzed patterns of distribution of four taxonomic groups in tallgrass prairie (grasshoppers, small mammals, vascular plants, and breeding birds) at two spatial scales. To assess organismal effects, we held spatial scale constant and we compared patterns of distribution and abundance among these taxonomic groups. Using long-term data from Konza Prairie, Kansas, there were significant differences in the pattern of distribution of grasshoppers, small mammals, vascular plants, and breeding birds within a single spatial scale. The number of core species (species occupying >90% of the sites in a region) of plants and birds was less than the number of satellite species (those occupying <10% of the sites in a region). The opposite was true for grasshoppers and small mammals. All four distribution patterns were significantly non-random, but only grasshoppers and small mammals were significantly bimodal at this scale. Plants and birds were unimodal. The patterns of distribution within these taxonomic groups at two spatial scales were significantly different as well. In all cases, the percentage of species in the core group declined, and the percentage of species in the satellite group increased as spatial scale increased. These results demonstrate the difficulty of testing theoretical models with only one taxonomic group at a single spatial scale. One should not accept or reject a model until the spatial domains of organismal and distance scaling have been properly evaluated.

Evolutionary implications of meiotic chromosome behavior, reproductive biology, and hybridization in 6X and 9X cytotypes of Andropogon gerardii (Poaceae ) - Norrmann, G.A.; Quarin, C.L.; Keeler, K.H. (American Journal of Botany, 1997)
Andropogon gerardii, big bluestem, has 60 and 90 chromosome cytotypes. Meiosis in the hexaploid was shown to be regular, although some secondary associations of bivalents form. Meiosis in the enneaploid (2n = 9z = 90) is irregular, leading to most gametes having unbalanced chromosome complements. Both cytotypes show considerable self-incompatibility. Cytotypes crossed freely, forming a variety of fertile euploids and aneuploids. Indistinguishable exomorphology, intermixing in natural populations, and compatibility suggest that A. gerardii is best understood as a cytotypically complex single species.

Fall point counts: Time of day affects numbers and species of birds counted - O'Leske, D.L.; Robel, R.J.; Kemp, K.E. (Transactions of the Kansas Academy of Science, 1997)
Time of day is known to affect results of avian surveys during breeding season and winter. Because little is known of the effects of time of day on avian surveys conducted between breeding season and winter, we conducted a series of point counts during early morning, midmorning, midafternoon, and late afternoon from mid September through early December. Numbers of birds counted and species richness differed by time of day and season, but only 1 of 16 time-of-day differences in numbers of birds counted was significant (P < 0.05) because the number of birds counted fluctuated widely during the study. Point-count data collected during early morning and late afternoon produced similar avian assemblages, but significantly different (P < 0.05) from assemblages created by data collected during midmorning and midafternoon periods, which were significantly different (P < 0.05) from each other. Caution is urged when using point-count data collected at different times of the day in the fall to describe avian abundances and compare avian assemblages in the Plains States

Fire, N availability and plant response in grasslands: A test of the transient maxima hypothesis - John M. Blair (Ecology, 1997)
In tallgrass prairie, periodic spring fires often result in enhanced aboveground net primary productivity (ANPP) that exceeds the productivity of either annually burned or unburned sites. This study evaluated two alternate hypotheses for the “pulse” in productivity following an infrequent fire: (1) enhanced ANPP results from increased net N mineralization rates due to the removal of surface litter and elevated soil temperatures following fire (the enhanced mineralization hypothesis) or (2) enhanced ANPP results from a transient release from both light and N limitation during a nonequilibrium period as a switch from energy to N limitation occurs (the transient maxima hypothesis). The former hypothesis predicts greater N availability following an infrequent fire, relative to either annually burned or unburned prairie. The latter predicts that N availability following an infrequent fire will decline to intermediate levels, relative to unburned and annually burned prairie, and continue to decline with successive annual fires. To test these hypotheses, I measured inorganic soil N, net N mineralization rates, and plant productivity and N content at Konza Prairie in sites with several different burn histories (unburned, annually burned, infrequently burned). Inorganic soil N and cumulative net N mineralization rates were greatest on the unburned sites, lowest in annually burned sites, and intermediate in infrequently burned sites. Net N mineralization rates and plant tissue N content both declined with successive spring burning. These results did not support the enhanced mineralization hypothesis but indicated that enhanced ANPP following an infrequent fire resulted from an accumulation of inorganic and mineralizable N in the absence of fire which, under conditions of adequate light availability, was utilized following a spring fire. This is consistent with the transient maxima hypothesis and suggests that nonequilibrium responses to multiple, variable resources (light, energy, N) are an important aspect of tallgrass prairie ecosystem dynamics.
Keywords: fire

Gradient models, gradient analysis and hierarchical structure in plant communities - Hoagland, B.W.; Scott. L. Collins (Oikos, 1997)
Two general models of plant community structure, the community-unit and the continuum, have dominated the thinking of American community ecologists. Hypotheses derived from these and other models of plant community structure rarely have been tested, however. Traditionally, analyses of gradient structure have focused primarily on whether or not the boundaries of species response curves are clustered, which does not provide a complete picture of gradient structure. In this study, we statistically analyzed three characteristics of plant community structure along gradients (1) pattern of boundaries of species distributions, (2) pattern of modes of species response curves, and (3) whether or not species distributions exhibit hierarchical structure. In combination, these characteristics yield eight different models of vegetation structure along gradients. To determine if vegetation corresponds to any of these models, we sampled species composition using belt transects of contiguous quadrats in a total of 42 wetland sites in Minnesota and the southern Great Plains, USA. Boundaries of species distributions were clustered in 10 of 42 cases, modes of species response curves were clustered in 19 of 42 cases, and species distributions exhibited hierarchical structure in all 42 cases. Results varied between sites. Overall, four models of community structure were supported. None of the sites sampled supported the models often associated with the continuum or the community-unit. These results confirmed the need to explore alternative models of gradient structure, and suggested that more than one model of vegetation structure may be needed to represent community structure along gradients.

Influence of protozoa and nutrient availability on nitrification rates in subsurface sediments - Strauss, E.A.; W. K. Dodds (Microbial Ecology, 1997)
Protozoan abundance, nitrification potential, and related factors in saturated subsurface sediments and the overlying soil were compared at a nonfertilized grassland and an agricultural cropland site. In a 6-week laboratory experiment, DOC, ammonium, and protozoan abundance were manipulated in flasks containing groundwater-sediment slurries. Microbial abundance (protozoa, actively respiring bacteria, and total bacteria) and nutrient concentrations (extractable ammonium and nitrate) were measured. Results from the soil profile analysis showed that protozoan abundance declined with depth at both sites, but significant numbers (392 cells g−1dw) were found in groundwater sediments at the cropland site. Nitrification potential declined with depth at the grassland site and increased with depth at the cropland site. In the laboratory experiment, treatment responses generally were observed within 3 weeks, but had diminished by 6 weeks. Protozoa reduced bacterial populations through the first 3 weeks, but this effect was not significant by week 6. In the cropland sediments, increased net nitrate production occurred in the two reduced protozoa treatments that received ammonium, suggesting that nitrification was occurring and was limited by ammonium. High protozoan abundance in the cropland sediments increased the nitrate flux response, unless DOC was added; in this case, no response occurred. No such responses were recorded in the grassland sediments. Apparently, appreciable nitrification can occur in some groundwater sediments, if sufficient ammonium is present and DOC availability is low. Furthermore, nitrification can be enhanced when protozoan abundance is elevated. Finally, our results suggest that surface land use practices can alter subsurface nitrification rates and microbial community structure.

Intermediate disturbance and its relationship to within-and between-patch structure - Scott. L. Collins; Glenn, S.M. (New Zealand Journal of Ecology, 1997)
The intermediate disturbance hypothesis has been the focus of considerable analysis in terrestrial and aquatic systems. This model predicts that species diversity will be highest at intermediate frequencies of disturbance. Despite numerous theoretical and empirical analyses, the utility of the model is still the subject of intense debate. Rather than developing restrictive time and space constraints on application, we suggest that the model may best be used as a generalizable framework for testing hypotheses in both aquatic and terrestrial systems. In addition, we believe that the model may be applied to both within- and between-patch scales. Finally, we propose an empirical model in which disturbance is an extinction causing event, and post-disturbance succession is modeled based on the dynamics of immigration and extinction. Such a model can incorporate a variety of patterns in species diversity in response to disturbance.

Interspecific interactions: constructing a general, neutral model for interaction type - W. K. Dodds (Oikos, 1997)
Experiments have not been devised to provide unbiased estimates of the relative co-occurrence of all different interaction types in communities. Thus, we have no idea what types of interspecific interactions to expect if we randomly sample species from an environment. The probability that a unidirectional, non-zero interaction is negative (P-) or positive (P+) has a direct effect on the expected types of reciprocal interspecific interactions. Analysis of field studies where strengths and signs of interactions between seven or more species were documented (large studies were selected to avoid bias from choosing species known to interact) suggests that P+=P-=0.5. Data also suggest that the proportion of non-zero interactions (C) is generally less than 0.6 when 10 or more interactions are considered. The proportion of expected reciprocal interspecific interactions can be calculated given the proportion of direct interactions that are not significantly different from zero and assuming that non-zero interactions are equally likely to be positive or negative. In general, this neutral model predicts that if species are chosen from an environment randomly, non-interaction (0/0), commensalism (+/0), or amensalism (-/0) will be most common when C < 0.6. Predation and functionally similar interactions (+/-), competition (-/-), and mutualism (+/+) should be relatively rare when there are less than 10 species with C < 0.6. Predation should be twice as common as competition or mutualism, and mutualism as common as competition. The neutral model suggests that community ecologists place undue emphasis on competition and predation.

Landscape gradients and habitat structure in native grasslands of the central great plains - Vinton, M.A.; Scott. L. Collins (Ecology and Conservation of Great Plains Vertebrates, 1997)
Habitat variables have a powerful influence on the distribution and abundance of organisms, and many organisms directly affect the physical structure of their local environment. These interactions produce a complex feedback system that drives community dynamics. This scenario is particularly true in grasslands where the effects of “keystone engineers,” such as the North American bison (Bison bison), have a tremendous influence on ecosystem structure and function (Collins and Benning 1996). This interplay between organisms and habitat structure in grasslands occurs within a climatic regime that varies dramatically from one year to the next. In addition, the relative influence of different habitat variables changes at different spatial and temporal scales.

Mammals of the Konza Prairie: new observations and an updated species list - McMillan, B.R.; Kaufman, G.A.; Matlack, R.S. (The Prairie Naturalist, 1997)

Modelling impact of bison on tallgrass prairie - Nellis, M.D.; J. M. Briggs (Transactions Kansas Academy of Science, 1997)
Keywords: tallgrass prairie

Mycorrhizal fungi affect root stele tissue in grasses - Miller, R.M.; Hetrick, B.A.D.; G.T. Wilson (Canadian Journal of Botany, 1997)
Although arbuscular mycorrhizal symbiosis was initially believed to have little or no impact on root morphology, we now recognize that subtle changes do occur and that these changes may be of considerable consequence to host growth and nutrition, as well as functional growth strategy. In examining the stele and root diameters of C3 and C4 grasses, C4 grasses were demonstrated to have a significantly larger proportion of their fibrous roots occupied by stele tissue than do C3 grasses. In fact, functional growth strategy (C3 versus C4) was observed to be a relatively good predictor of stele area. Mycorrhizal fungi also influenced the amount of stele tissue, but the effect was not the same for both C3 and C4 grasses. The stele area of all C4 grasses except for Sorghastrum nutans was greater in the presence of mycorrhizal colonization. Among the C3 grasses, only Bromus inermis showed a significant increase, although Elymus cinereus and Lolium perenne displayed significant decreases in response to arbuscular mycorrhizal colonization. Changes in the stele area of the plant species were closely related to their responsiveness to mycorrhizal symbiosis and might in part explain both beneficial and detrimental responses of plants to mycorrhizae. An increase in stele circumference induced by mycorrhizae would allow for greater uptake and passage of water and nutrients to the vascular cylinder, and growth depressions could be a direct outcome of reduced stele circumference. Thus, differences in stele circumference represent a possible mechanism for mycorrhizal impacts on host plants. These findings indicate that structural differences among grasses are related to different functional capabilities and further emphasize the need for better integration of comparative anatomy and morphology procedures in the study of mycorrhizal symbiosis. Key words: stele, root anatomy, mycorrhizal dependency, functional growth strategy, mycorrhiza, C3 and C4 grasses.

Nest predation and its relationship to nest placement in tallgrass prairie shrub patches - Parker, T.H. (Kansas State University, 1997)

NOAA AVHRR land surface albedo algorithm development - Toll, D.L.; Shirley, D.; Kimes, D.S. (International Journal of Remote Sensing, 1997)
The primary objective of this research is to develop a surface albedo model for the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR). The primary test site is the Konza prairie, Kansas (U.S.A.), used by the International Satellite Land Surface Climatology Project (ISLSCP) in the First ISLSCP Field Experiment (FIFE). In this research, high spectral resolution field spectrometer data was analyzed to simulate AVHRR wavebands and to derive surface albedos. Development of a surface albedo algorithm was completed by analysing a combination of satellite, field spectrometer, and ancillary data. Estimated albedos from the field spectrometer data were compared to reference albedos derived using pyranometer data. Variations from surface anisotropy of reflected solar radiation were found to be the most significant albedo-related error. Additional error or sensitivity came from estimation of a shortwave mid-IR reflectance (1.3-4.0 mum) using the AVHRR red and near-IR bands. Errors caused by the use or AVHRR spectral reflectance to estimate both a total visible (0.4-0.7 pm) and near-IR (0.7-1.3 mum) reflectance were small. The solar spectral integration, using the derived ultraviolet, visible, near-IR and SW mid-IR reflectivities, was not sensitive to many clear-sky changes in atmospheric properties and illumination conditions
Keywords: ISLSCP

Organic matter dynamics in Kings Creek, Konza Prairie, Kansas, USA - Gray, L.J. (Journal of the North American Benthological Society, 1997)

Photosynthetic gas exchange and water relations responses of three tallgrass prairie species to elevated carbon dioxide and moderate drought - Hamerlynck, E.P.; McAllister, C.A.; Alan K. Knapp; J.M. Ham; Owensby, C.E. (International Journal of Plant Science, 1997)
Undisturbed tallgrass prairie was exposed to ambient and elevated (twice-ambient) levels of atmospheric CO2 and experimental dry periods. Seasonal and diurnal midday leaf water potential (Ψ leaf), net photosynthesis $(A_{\text{net}})$, and stomatal conductance (g s) responses of three tallgrass prairie growth forms—a C4 grass, Andropogon gerardii; a broad-leaved woody C3 shrub, Symphiocarpos orbiculatus; and a C3 perennial forb, Salvia pitcheri—were assessed. $Ψ _{\text{leaf}}$ in A. gerardii and S. orbiculatus was higher under elevated CO2, regardless of soil moisture, while $Ψ _{\text{leaf}}$ in S. pitcheri responded only to drought. Elevated CO2 always stimulated $A_{\text{net}}$ in the C3 species, while A. gerardii $A_{\text{net}}$ increased only under dry conditions. However, $A_{\text{net}}$ under elevated CO2 in the C3 species declined with drought but not in the C4 grass. Under wet conditions, g s reduced in elevated CO2 for all species. During dry periods, gs at elevated CO2 was sometimes higher than in ambient CO2. Our results support claims that elevated CO2 will stimulate tallgrass prairie productivity during dry periods and possibly reduce temporal and spatial variability in productivity in these grasslands.
Keywords: Water relations

Plant strategies for coping with variable light regimes - Alan K. Knapp; Fay, P.A. (Mechanisms of Environmental Stress Resistance in Plants, 1997)

Radar backshatter soil-moisture relationships over tallgrass prairie - Hutchinson, J.M.S. (Kansas State University, 1997)
Keywords: tallgrass prairie

The relationship between leaf-level photosynthetic rates and success in a high productivity grassland - McAllister, C.A. (Kansas State University, 1997)

Simulating the surface energy budget over the Konza Prairie with a mesoscale model - Song, J.; Willmott, C.J.; Hanson, B. (Agricultural and Forest Meteorology, 1997)
Using FIFE observations on four golden days and a coupled soil-canopy-atmosphere (mesoscale) dynamic model, we simulate the biophysical influences of a prairie on the surface energy budget. Atmospheric dynamics within the model are fully three-dimensional. Canopy and soil submodels were modified to include the aggregate effects of standing brown vegetation on stomatal conductance and surface energy partitioning, and litter cover on soil thermal and hydraulic properties. Model-simulated energy fluxes compare reasonably well to in situ measurements. It was found that the spatial variation of simulated latent-, sensible-, and ground-heat fluxes is very sensitive to soil-moisture and biomass distributions over the FIFE domain. High latent-heat fluxes are related to high occurrences of green leaf-area indices (LAIgreen), low brown leaf-area indices (LAIbrown), and high soil-moisture contents, as well as to sufficient available energy. High sensible-heat fluxes often are coincident with a low LAIgreen, high LAIbrown, and relatively dry soils. High ground-heat fluxes occur with lower values of total LAI and high soil-moisture contents. As a result of soil-canopy-atmosphere interactions, simulated air temperatures vary spatially up to 2degree C. In addition, it was found that-for a prairie environment like the Konza Prairie with green leaf-area indices less than 2-simulated latent-heat fluxes from the canopy are about two times greater than those from the soil beneath the canopy
Keywords: FIFE

Soil N and plant responses to fire, topography and supplemental N in tallgrass prairie - Turner, C.L.; John M. Blair; Schartz, R.J.; Neel, J.C. (Ecology, 1997)
Tallgrass prairie in the Flint Hills region of Kansas is characterized by considerable topographic relief coupled with variation in soil properties. These topoedaphic gradients, together with variation in fire regimes, result in temporal and landscape-level variability in soil resource availability and plant responses. Nitrogen usually is considered to be the nutrient most limiting to primary productivity in tallgrass prairie, but few studies have addressed how N availability varies seasonally, or across the landscape and with fire frequency. We measured soil inorganic N, in situ net N mineralization, aboveground net primary productivity (ANPP), and N mass on plots either fertilized with N in 1993 or in 1994, or unfertilized, in uplands and lowlands of two annually burned and two long-term unburned sites during the 1994 growing season. In addition, our study was conducted in the year following record rainfall, allowing us to assess the potential for high precipitation amounts to affect subsequent N cycling and plant production. Both fire treatment and topography affected soil N availability. In general, N mineralization was greater on unburned than on burned sites and was up to five times greater on uplands than lowlands. Total extractable soil N was highest early in the season and least at midseason, and it also tended to be higher in unburned sites than burned sites on unfertilized plots. Added N increased ANPP, but there were no differences between plots fertilized in 1994 and those fertilized in 1993. In general, patterns of ANPP on control plots were consistent with known production responses to topography and burning (higher in annually burned sites and in lowland sites) but were inversely related or unrelated to patterns of N availability (higher in unburned sites and at upland topographic positions). Potential loss of N by volatilization during spring burning was greater than in years with normal rainfall amounts and represented a significant portion of aboveground plant N mass. Potential N losses did not appear to limit ANPP or N availability in the current growing season. Our results suggest that different factors control soil N mineralization and plant productivity, which explains, in part, why patterns of ANPP are not well correlated with patterns of N availability in tallgrass prairie ecosystems.
Keywords: tallgrass prairie

Spatial and temporal patterns of vegetation in the Flint Hills - J. M. Briggs; Rieck, D.R.; Turner, C.L.; Henebry, G.M.; Goodin, D.G.; Nellis, M.D. (Transactions Kansas Academy of Science, 1997)
In tallgrass prairie, complex interactions among multiple limiting resources in combination with a variety of land use practices can lead to a heterogeneous landscape. Remote-sensing data (AVHRR) were coupled with abiotic factors to explore spatial and temporal vegetation patterns of the Flint Hills in Kansas and Oklahoma. This information should enable the detection of both natural (e.g., interannual variation in precipitation and temperature) and anthropogenic (e.g., climate change, over-grazing, land-use practices) stresses on this grassland ecosystem. Shifts in the spatial and temporal patterns of vegetation (as measured from NDVI by AVHRR) have been correlated with meteorological data (from 117 weather stations) to identify key abiotic variables that determined vegetation patterns across this region. In 4 years, the combination of annual precipitation and growing degree days was useful to detect spatial and temporal vegetation patterns of the Flint Hills. However, it is imperative that land-use patterns are known in order to assess adequately spatial and temporal patterns of vegetation in this area.

Spatial variability of nitrogen mineralization at the field scale - Mahmoudjafari, M.; Kluitenberg, G.J.; Havlin, J.L.; Sisson, J.B.; Schwab, A.P. (Soil Science Society of America Journal, 1997)
Spatial variability of N mineralization represents a potential problem in predicting the quantity of N mineralized under field conditions. An understanding of mineralization variability is needed if prediction of potential mineralization is to be incorporated into fertilizer recommendation models. The objective of this study was to characterize spatial variability of N mineralization in a Kansas agricultural field. Intact undisturbed soil cores were collected at 108 locations within a 1.7-ha field following wheat (Triticum aestivum L.) harvest. The undisturbed cores were incubated aerobically, and NO−3 was leached periodically as a measure of mineralization. Variability was characterized by examining the spatially distributed values of mineralization potential, N0, and mineralization rate constant, k, parameters of the classical first-order mineralization rate model. Values of N0 were distributed normally with low variability (coefficient of variation [CV] = 15%) and weak autocorrelation. Values of k also followed a normal distribution with low variability (CV = 14%) but were spatially independent. Both N0 and k determined the spatial pattern of Nm, the quantity of N mineralized at a particular time. Variability in k controlled the spatial pattern of Nm earlier in the incubation period, and variability in N0 controlled the spatial pattern late in the incubation period. The incubation approach used in this study allowed characterization of the spatial patterns in N0, but the spatial variability of k observed in this study may not adequately represent field conditions because conditions of constant temperature and water content were used.

Spatiotemporal scales of non-equilibrium community dynamics: a methodological challenge - Bartha, S.; Czaran, T.; Scheuring, I. (New Zealand Journal of Ecology, 1997)
The Intermediate Disturbance Hypothesis [IDH] and the Gradual Climate Change Hypothesis [GCC] offer intuitively appealing, verbal non-equilibrium explanations to species coexistence in competitive communities, but so far they lack a solid theoretical background and a proper experimental methodology. To make them testable and comparable on a solid methodological basis, they should be formulated as well-defined non-equilibrium community dynamical models. We suggest that this is possible, if explicit assumptions on the spatiotemporal structure of the environment and the pattern-generating mechanisms of the species assemblage in question are given. In the framework of a non-spatial population dynamical model we show that disturbance and climate change effects can be safely distinguished, and the "intermediate" level of external effects leading to maximum community diversity can be quantified. Based on the information statistical analysis of field data and simulation results, we explain why it is necessary to consider simultaneously the spatiotemporal patterns of the vegetation, the abiotic environment and the disturbances in order to predict the consequences of external effects regarding community diversity.

A technique for monitoring ecological disturbance in tallgrass prairie using seasonal NDVI trajectories and a discriminant function mixture model - Goodin, D.G.; Henebry, G.M. (Remote Sensing of the Environment, 1997)
Natural and anthropogenic disturbance in tallgrass prairie communities can induce changes in plant species composition, including shifts in the relative abundance of C3 and C4 lifeforms. The asynchronous seasonality in greenness exhibited by C3 and C4 species enables monitoring of their relative abundance using temporal trajectories of sensor-derived vegetation indices, such as NDVI. We use close-range measurements made over 22 experimental plots at the Konza Prairie Research Natural Area (KPRNA) to evaluate seasonal trajectories in NDVI as a function of Full-size image (<1 K) ratio. The NDVI data were collected from each plot at approximately 10-day intervals throughout the 1995 growing season. Metrics for summarizing the temporal behavior of NDVI trajectories were derived from two transformations of the data: 1) a conventional approach plotting NDVI against day of year and 2) an alternative approach plotting normalized cumulative integrated NDVI against growing degree day. Discriminant function mixture models derived from each set of inetrics were used together with species composition data from the experimental plots to derive relative Full-size image (<1 K) abundances. Results show that both methods can classify the majority of cases into their correct Full-size image (<1 K) abundance category; however, the transformation using normalized integrated NDVI against growing degree day was a significantly better discriminator (p=0.0102). The techniques presented are effective for monitoring relative Full-size image (<1 K) abundance in tallgrass prairie; however, more investigation is needed to assess their performance at different spatial resolutions and in different geographic settings.
Keywords: tallgrass prairie

Trace elements in recent algal carbonate at the Konza LTER site, northeastern Kansas, determination by laser ablation microprobe (LAM) ICPMS - G. L. Macpherson; Jackson, S. (Geological Society of America, 1997)

Validation of kernel-driven semiempirical models for the surface bidirectional reflectance distribution function of land surfaces - Hu, B.; Lucht, W.; Li, X.; Strahler, A.H. (Remote Sensing of Environment, 1997)
A semi-empirical, kernel-driven Ambrals BRDF (bidirectional reflectance distribution function) model was developed for correcting and studying view and illumination angle effects of a wide variety of land covers in remote sensing applications. This model was validated by demonstrating its ability to model 27 different multiangular data sets well, representing major types of land cover, including crops (maize, soyabeans, wheat, sorghum, vineyards, vegetables and sunflowers), grasslands (Konza prairie), Jack pine [Pinus banksiana], black spruce [Picea mariana] and aspen [Populus spp.] forests, and bare and ploughed soil. The selection of the kernels used in the model was related to land cover type, and the inversion accuracy was good in nearly all cases: the correlation coefficient between modelled and observed reflectances was larger than 0.9 for about half of the data sets and larger than 0.70 in all but two cases where the observations were irregular. The average root mean squared error of the inversions was 0.034. A new kernel modelling the sun zenith angle dependence of multiple scattering improved fits for dense vegetation. Operation of the Ambrals model was demonstrated by applying it to an ASAS (Advanced Solid-State Array Spectroradiometer) image on a per-pixel basis

Water vapor fluxes and their impact under elevated CO2 in a C4 tallgrass prairie - Owensby, C.E.; J.M. Ham; Alan K. Knapp; D. Bremer; Auen, L.M. (Global Change Biology, 1997)
We measured leaf-level stomatal conductance, xylem pressure potential, and stomate number and size as well as whole plant sap flow and canopy-level water vapour fluxes in a C4-tallgrass prairie in Kansas exposed to ambient and elevated CO2. Stomatal conductance was reduced by as much as 50% under elevated CO2 compared to ambient. In addition, there was a reduction in stomate number of the C4 grass, Andropogon gerardii Vitman, and the C3 dicot herb, Salvia pitcheri Torr., under elevated CO2 compared to ambient. The result was an improved water status for plants exposed to elevated CO2 which was reflected by a less negative xylem pressure potential compared to plants exposed to ambient CO2. Sap flow rates were 20 to 30% lower for plants exposed to elevated CO2 than for those exposed to ambient CO2. At the canopy level, evapotranspiration was reduced by 22% under elevated CO2. The reduced water use by the plant canopy under elevated CO2 extended the photosynthetically-active period when water became limiting in the ecosystem. The result was an increased above- and belowground biomass production in years when water stress was frequent.
Keywords: tallgrass prairie

Biological properties of soil and subsurface sediments under abandoned pasture and cropland - W. K. Dodds; Banks, M.K.; Clenan, C.S.; C. W. Rice; Sotomayor, D.; Strauss, E.A.; Yu, W. (Soil Biology & Biochemistry, 1996)
Little is known about the effects of most surface land-use practices on shallow subsurface microbial communities. We analyzed duplicate cores taken aseptically from up to 10 m depth from unconsolidated valley sediments (soils) beneath an abandoned pasture reverting to tall grass prairie and cropland. Both profiles had similar soil texture, with moderately higher silt under cropland and a slight decrease in clay with depth. Soluble organic C was about two times higher in the grassland site and dissolved O2 was about 8% lower compared with the cropland site. Water content and C-to-N ratios were greatest at the grassland surface but were less in the grassland than the cropland site within 2 m depth. In general, numbers of aerobic heterotrophic bacteria and protozoa decreased with depth until the saturated zone (4.3 m in grassland and 5.3 m in the cropland site). Bacterial numbers as determined by plate counts were about 10-fold less at the groundwater interface than in the surface soils at both sites. Direct microscopic counts of total bacteria were approximately the same in the surface soil and the sediments at the top of the water table at both sites. The top of the water table generally did not exhibit elevated microbial biomass or activity relative to deeper sediments. There was no significant relationship between protozoan numbers and microbial thymidine uptake at the cropland site, but a negative relationship was observed at the grassland site. The data suggest that cultivation may affect microbial biomass and activity in the subsurface, as well as community interactions between protozoa and bacteria.

Biomass and density responses in tallgrass prairie legumes to annual fire and topographic position - Towne, E.G.; Alan K. Knapp (American Journal of Botany, 1996)
Annually burned tallgrass prairie is purported to be a nitrogen-limited system, especially when compared to unburned prairie. To test the hypothesis that legumes, potential nitrogen-fixers, would increase in relative abundance in annually burned sites, we assessed their density and biomass for two seasons on upland and lowland soils in annually burned and unburned watersheds. Total legume density was significantly higher in burned (8.0 ± 1.0 [SE] stems/m2) than in unburned watersheds (3.0 ± 0.3 stems/m2). Species with higher (P < 0.05) densities in burned than in unburned prairie included Amorpha canescens, Dalea candida, Dalea purpurea, Lespedeza violacea, Psoralea tenuiflora, and Schrankia nuttallii. Desmodium illinoense was the only legume that responded negatively to annual fire. Total legume biomass did not differ between burned (11.3 ± 1.3 g/m2) and unburned prairie (10.5 ± 0.9 g/m2). Biomass productions of Dalea candida and Psoralea tenuiflora were higher (P < 0.05) in burned than in unburned sites, but biomasses of other legumes were similar between burn treatments. Average individual stem masses of Amorpha canescens and Baptisia bracteata were significantly greater in unburned than in burned prairie. Legumes were affected differentially by topographic location. Total legume density was higher (P < 0.05) on lowland soils (6.6 ± 1.0 stems/m2) than on upland soils (4.3 ± 0.5 stems/m2). However, total legume biomass was not different between lowland soils (12.0 ± 1.2 g/m2) and upland soils (9.9 ± 1.0 g/m2). Densities and biomasses of Amorpha canescens, Desmodium illinoense, and Lespedeza capitata were higher on lowland sites than on upland sites, whereas densities and biomasses of Baptisia bracteata and Dalea purpurea were higher on upland than on lowland soils. Most legume species are either fire tolerant or exhibit a positive response to fire and their persistence in annually burned prairie suggests that they may play an important role in the nitrogen budget of this ecosystem.
Keywords: tallgrass prairie

Clonal biology of the caespitose grass Schizachyrium scoparium: mechanisms of intraclonal regulation and ecological success - Derner, J.D. (Texas A&M University, 1996)

Comparisons of water consumption between two grassland emberizids - Zimmerman, J.L. (The Prairie Naturalist, 1996)

Denitrification in soil profiles beneath grassland and cultivated soils - Sotomayor, D.; C. W. Rice (Soil Science Society of America Journal, 1996)
The denitrification potential of subsoils and aquifers must be characterized to assess the ultimate fate of soil N. This experiment was conducted to study changes in the subsurface distribution and activity of denitrifying bacteria as a result of cultivation. We examined soil profiles for their capacity (N addition) and potential (N + C addition) to denitrify as well as for denitrifying bacterial numbers in a Reading silt loam (fine, mixed, mesic Typic Argiudoll) soil under grassland and cultivation. Denitrifying enzyme activity was undetectable throughout the subsurface of soil profiles at both sites. Overall, the cultivated site had significantly higher NO−3 concentrations, denitrifier populations, and denitrification potential. Denitrifying bacteria were stratified in the vadose zone at the prairie site, with lowest numbers and lowest denitrification potential occurring at the interface of the water table. Although C addition enhanced denitrification at this site, the profile was not nearly as limited by C as that of the cultivated site. The results demonstrated that increased N inputs and cultivation during approximately 50 yr changed the denitrifying population and denitrification potential in the vadose and saturated zones of soils.

Detecting spatial and temporal patterns of aboveground production in a tallgrass prairie using remotely-sensed data - Su, H.; J. M. Briggs; Alan K. Knapp; John M. Blair; Krummel, J.R. (1996)
Spatial and temporal patterns of aboveground production in a tallgrass prairie ecosystem constitute one of the important spatial components associated with ecological processes and biophysical resources (e.g., water and nutrients). This study addresses the effects of disturbance, topography, and climate on the spatial and temporal patterns of North American tallgrass prairie at a landscape level by using high resolution satellite data. Spatial heterogeneity (SH) derived from the satellite data was related to the impacts of the disturbance of fire and grazing, topographical gradient, and amount of precipitation during the growing season. The result suggests that ecological processes and biophysical resources can be quantified with high resolution satellite data for tallgrass prairie management
Keywords: tallgrass prairie

Development of water-usage coefficients for the Tallgrass Prairie - Lewis, S.L. (Kansas State University, 1996)
Keywords: tallgrass prairie

Diversity of denitrifying bacteria in cultivated and native prairie soil profiles - Halda-Alija, L. (Kansas State University, 1996)

The dynamics of bison (Bos bison) grazing patches in tallgrass prairie - Catchpole, F.B. (Kansas State University, 1996)
Keywords: tallgrass prairie

Early season cuticular conductance and gas exchange in two oaks near the western edge of their range - Hamerlynck, E.P.; Alan K. Knapp (Trees, 1996)
Seasonal changes in minimum leaf conductance to water vapor (gmin), an estimate of cuticular conductance, and photosynthetic gas exchange in two co-occurring oak species in north-east Kansas (USA) were examined to determine if leaf gas exchange characteristics correlated with differences in tree distribution. Bur oak (Quercus macrocarpa Michx.) is more abundant in mesic gallery forest sites, whereas chinquapin oak (Quercus muehlenbergii Englm.) is more abundant in xeric sites. Early, during leaf expansion, gmin was significantly lower in chinquapin oak than in bur oak, though midday water potentials were similar. After leaves had fully expanded, gmin decreased to seasonal minimum values of 4.57 (±0.274) mmol m-2 s-1 in bur oak, and 2.66 (±0.156) mmol m-2 s-1 in chinquapin oak. Water potentials at these times were significantly higher in chinquapin oak. As leaves were expanding, photosynthesis (Anet) was significantly higher in chinquapin oak than in bur oak. Later in the growing season, Anet and gleaf increased dramatically in both species, and were significantly higher in bur oak relative to chinquapin oak. We concluded that bur and chinquapin oak have a number of leaf gas exchange characteristics that minimize seasonal water loss. These characteristics are distinct from trees from more mesic sites, and are consistent with the distribution patterns of these trees in tall-grass prairie gallery forests.
Keywords: Cuticular conductance; Gallery forests; Leaf development; photosynthesis; Quercus

The ecology of a subterranean isopod, Caecidotea tridentata - Edler, C.; W. K. Dodds (Freshwater Biology, 1996)
1. The blind isopod Caecidotea tridentata is the dominant invertebrate in a simple community of subterranean organisms inhabiting the local, shallow aquifer under Konza Prairie, Kansas, U.S.A. 2. The ecology of this karst aquifer was explored by sieving water from a spring, collecting water samples for analysis, and manipulating sediments and invertebrates in the laboratory. The size frequency distribution was stable and gravid females were present throughout the year, suggesting continuous reproduction. 3. The number of isopods collected per litre was negatively correlated with discharge and the abundance of bacteria, but positively related to the numbers of an amphipod (Bactrurus hubrichti). This may be explained if both the isopods and the amphipods track the saturated zone below the top of the water table; at lower discharge, the top of the water table is closer to the spring outlet. The suspended bacteria wash out in greater numbers with high discharge. 4. When isopods and carbon were added in a pairwise experimental design to sediments collected from the aquifer, the isopods significantly stimulated numbers and activity of planktonic and sedimentary bacteria, while carbon had no effect. This suggests that invertebrates can affect the microbes locally in an aquifer.

Ecosystem level responses of tallgrass prairie to elevated CO2 - Owensby, C.E.; J.M. Ham; Alan K. Knapp; C. W. Rice; Coyne, P.I.; Auen, L.M. (Carbon Dioxide and Terrestrial Ecosystems, 1996)
Keywords: tallgrass prairie

The effect of density dependence on community structure - W. K. Dodds; Henebry, G.M. (Ecological Modelling, 1996)
The effect of population density controls on the relationship between stability and species richness was explored by constructing Monte Carlo community models with density dependent population controls. Simulated communities with more initial species exhibit proportionally fewer extinctions. This form of stability is greatest at low interaction strengths and intermediate connectivities. Stability appeared to be related to the fact that species with more interactions were less likely to be driven to extinction by negative interactions. Species with mutualistic (+ / +) and commensal (0/ +) interactions survive at greater than expected proportions, while those with relatively more competitive (− / −) and amensal (0 / −) interactions tend toward extinction. Incorporation of density dependent population control thus leads to features that previous community models have not exhibited. It is suggested that communities with many of the populations controlled by abiotic factors in a density dependent fashion should exhibit increased stability with more species.
Keywords: Community matrix; Competition; density dependence; mutualism

Effects of altered soil water on liter decomposition and microarthropod composition - O'Lear, H.A. (Kansas State University, 1996)

Effects of bison and cattle grazing on growth, biomass allocation and reproduction of five tallgrass prairie forbs - Damhoureyeh, S.A. (Kansas State University, 1996)
Keywords: tallgrass prairie

Effects of bison grazing, fire and topography on floristic diversity in tallgrass prairie - D.C. Hartnett; Hickman, K.R.; Walter, L.E.F. (Journal of Range Management, 1996)
Grazed and ungrazed sites subjected to different fire frequencies were sampled on the Konza Prairie Research Natural Area in northeast Kansas after 4 years of bison grazing (1987-1991). The objective was to study effects of bison grazing on plant species composition and diversity components (plant species richness, equitability, and spatial heterogeneity) in sites of contrasting fire frequency. Cover and frequency of cool-season graminoids (e.g. Poa pratensis L., Agropyron smithii Rydb., Carex spp.) and some forbs (e.g. Aster ericoides [A. Gray] Howell, and Oxalis stricta L.) were consistently higher in sites grazed by bison than in ungrazed exclosures, whereas the dominant warm-season grasses (Andropogon gerardii Vitman, Sorghastrum nutans [L.] Nash, Panicum virgatum L., Schizachyrium scoparium [Michx.] Nash) and other forbs (e.g. Solidago missouriensis Nutt.) decreased in response to bison. Plant species diversity (H′) and spatial heterogeneity in all areas sampled were significantly increased by bison. Increased heterogeneity and mean species richness in grazed prairie (40 species per sample site) compared to ungrazed prairie (29 species per site) were likely a result of greater microsite diversity generated by bison, whereas preferential grazing of the dominant grasses and concomitant increases in subordinate species resulted in an increase in equitability of species abundances. Species/area relationships indicated greater effects of bison on plant species richness with increasing sample area. Increases in plant diversity components associated with bison grazing were generally greater in annually burned than in 4-year burned sites. Effects of ungulate grazers on floristic diversity have important implications given recent evidence that plant species diversity and the compositional and production stability of grassland plant communities are positively related.
Keywords: tallgrass prairie

Effects of bison grazing on plant species diversity in tallgrass prairie - D.C. Hartnett; Hickman, K.R.; Walter, L.E.F. (1996)
Keywords: tallgrass prairie

Effects of grazing systems and stocking rates on plant species diversity in Kansas tallgrass prairie - Hickman, K.R.; D.C. Hartnett; Cochran, R.C. (1996)
Keywords: tallgrass prairie

Effects of large ungulate herbivory on tallgrass prairie plant population and community structure - Hickman, K.R. (Kansas State University, 1996)
Keywords: tallgrass prairie

Effects of management practices on nematode community structure in tallgrass prairie - Todd, T.C. (Applied Soil Ecology, 1996)
The effects of burning, mowing, and nitrogen (N) and phosphorus (P) fertilization on the trophic structure of a tallgrass prairie nematode community were examined in a long-term field experiment established in 1986. Nematode densities and trophic composition were determined in October of 1987, 1989, and 1994 following 2, 4, and 9 years of treatment, respectively. Total populations of obligate herbivores tended to increase with annual burning and N fertilization but responses by individual taxa were relative to the structure and composition of vegetation as determined by management practice. In contrast, mowing resulted in consistent reductions in herbivore densities. The family Tylenchidae, with species classified as both root and fungal feeders, exhibited short-term decreases in numbers due to burning and long-term increases in numbers due to mowing. Treatment responses by this group were more consistent with the behavior of known fungal-feeding than root-feeding nematodes. Microbivore densities increased with burning and N fertilization, while numbers of omnivores and predators declined with chronic N additions. The effects of P fertilization on nematode population densities varied with management practice, primarily N fertilization. Canonical discriminant analysis differentiated trophic groups based on their responses to mowing and P-fertilization. Measurements of the trophic composition of the nematode community, particularly the relative abundance of individual herbivore taxa and the proportion of fungivores to microbivores, were good indicators of ecosystem responses to management practices.
Keywords: disturbance; fire; Mowing; Nematode; nitrogen; tallgrass prairie; Trophic structure

Elucidation of factors associated with the maturity related decline in degradability of big bluestem cell wall - Titgemeyer, E.C.; Cochran, R.C.; Towne, E.G.; Armendariz, C.K.; K.C. Olson (Journal of Animal Science, 1996)
Big bluestem (Andropogon gerardii) forage samples were collected from three ungrazed, annually burned pastures at 38, 58, and 97 d after burning. Cell wall material received five treatments: chlorite delignification, chlorite delignification plus alkali extraction, NaOH, NaOCH3 in methanol, or NaBH4. Untreated and treated cell walls were analyzed for carbohydrate composition (glucose, xylose, arabinose, galactose, and uronic acids), acetyl bromide lignin, acid detergent lignin, alkali-labile phenolics (p-coumaric and ferulic acids), acetyl groups, and 24- and 72-h in vitro degradabilities of neutral monosaccharides. A number of compositional features, notably concentrations of xylose, core lignin as measured by acetyl bromide lignin, alkali-labile phenolics, and acetyl groups, were well related to the decline in cell wall degradability that occurred with increasing maturity of big bluestem. p-Coumaric acid increased with increasing maturity to a greater extent than did ferulic acid. Acid detergent lignin was not well related to degradability of the cell wall for either the untreated or chemically treated cell walls. Chemical treatments failed to identify any particular cell wall component as being most inhibitory. However, all treatments improved in vitro degradability of the carbohydrate fraction, indicating that components contributing to the undegradability of big bluestem cell wall are sensitive to chemical alteration. Treatments involving alkali were most effective for improving degradability of big bluestem cell walls.

Fire and topographic effects on decomposition rates and nitrogen dynamics of buried wood in tallgrass prairie - O'Lear, H.A.; Seastedt, T.R.; J. M. Briggs; John M. Blair; Ramundo, R.A. (Soil Biology & Biochemistry, 1996)
Decay rates and N dynamics of wood in soils of annually burned and unburned tallgrass prairie were measured over a 3-y period. Wooden dowels were placed at upland, mid-slope and lowland sites in two annually burned and two unburned watersheds. After 3 y, an average of only 15% of initial wood mass remained in burned watersheds, while 34% remained in unburned watersheds. Topographic position also significantly affected decay rates, with dowels decaying faster in the shallow-soil, upland sites and slope sites than in the deep-soil, lowland sites. This pattern is opposite of that generally observed for plant productivity (i.e. greater at lowland sites compared to uplands), and suggests that the controls of belowground decomposition and plant productivity are dissimilar. Dowels in both burned and unburned watersheds showed significant increases in N concentration over 3 y. Topographic position did not affect N concentration in the residual dowel material. Burn treatment, however, did affect N concentration, with dowels decomposing in burned watersheds having a higher average N concentration (0.5% after 3 y exposure) than dowels in unburned watersheds (0.43%). Relatively rapid decay rates resulted in net release of N, despite increased N concentration in the residual material. Faster net N release on the annually burned watershed was due to faster mass loss, since there were no differences in the rate of increase in N concentration per unit mass lost. Surface soil temperatures on burned prairie following spring fire usually exceed those on unburned prairie. However, average monthly summer soil temperatures (May–August) at a 10 cm depth in burned and unburned plots during the study were not statistically different and could not explain decay rate differences. Additionally, one of our unburned watersheds was accidentally burned during the first year of the study. Surprisingly, there were no significant differences in rates of wood decay between that watershed and the other unburned watershed. This suggests that indirect effects of annual fire (i.e. changes in the composition of soil flora and fauna) may override the short-term effects of fire (i.e. changes in soil temperature and moisture) on belowground decomposition in tallgrass prairie.
Keywords: tallgrass prairie

Forest spread and phase transitions at forest-prairie ecotones in Kansas, U.S.A - Loehle, C.; Li, B.L.; Sundell, R.C. (Landscape Ecology, 1996)
The spread of gallery forest habitat into upland areas is of substantial interest to resource managers because such spread has many implications for the management of grassland and forest habitats. This study used a dynamic percolation model to examine the potential rates of spread or invasion of forest in eastern Kansas. Aerial photos taken 16 years apart at the Fort Riley training base were used to calibrate a spatially explicit contagion model of forest spread to interpolate and extrapolate the forest spread processes. Results fit the actual pattern of spread well, as measured by both visual inspection and a multiscale fractal measure of pattern. Comparisons to a long-term fire-exclusion experiment in Geary County, Kansas, and to the Konza Prairie also provided validation. Both the simulation and the 100-year Geary County series showed an interesting pattern of forest spread. Spread was slow and steady until about 20% forest cover was reached, at which point the rate increased. We conclude that this self-accelerating response is due to spatial patterns created by the spreading forest that tend to accelerate the growth process after a critical point is reached. On the basis of theoretical study and experimental simulation of the percolation phase transitions, we suggest that fractal dimensions in a transient ecotone of binary mixtures (e.g., trees and grasses) should range between 1.56 and 1.8958, and the critical fractal dimension during ecotonal phase transitions should be 1.7951. This critical point of about 18.5% forest cover that we predicted was close to the observed result and might represent a phase transition at the forest-prairie ecotone
Keywords: gallery forest

Genesis and morphology of soils on the Konza Prairie Research Natural Area, Riley and Geary Counties, KS - Wehmueller, W.A. (Kansas State University, 1996)
The Konza Prairie Research Natural Area (KPRNA) is a 3487 ha tract of tallgrass prairie set aside for long-term ecological research. The purpose of this study is to describe the morphology of soils, investigate processes of soil genesis, and record the distribution of soils for one watershed (N4D) within KPRNA. The soils for the N4D watershed are mapped at a scale of 1:2,000. The soil map depicts the aerial distribution of soils in the study area. In the study area, there are four soil-landscape associations: (1) soils on the less sloping summits; (2) steeply sloping soils on side slopes; (3)soils on foot slopes; and (4) soils on terraces and flood plains. Parent material stratigraphy is much more complex than previous studies had shown. Soils on Summits developed in a thin mantle of loess overlying welded paleosols formed in hillslope sediment over residuum from Permian cherty limestone. The dominant pedogenic processes in the composite modern soil and paleosol formed in hillslope sediment are leaching of carbonate and translocation of clay resulting in formation of an argillic horizon. The extent of weathering observed in the paleosol suggests a longer period of soil formation than that of the composite modern soil and paleosol formed in hillslope sediment. Soils on side slopes have formed in hillslope sediment over residuum weathered from shale. On the steeply sloping side slopes, the soils exhibit no evidence of clay translocation. The lack of clay translocation and abundance of carbonates indicate that these soils are not highly weathered. Translocation and redistribution of carbonate was the dominant pedogenic process. In contrast, soils developed in similar parent materials on more gently sloping side slopes are leached more deeply and have argillic horizons. Soils on foot slopes have also formed in hillslope sediment over residuum. The depth to the lithologic discontinuity between the hillslope sediment and residuum is deeper for the soils on foot slopes compared to soils on side slopes. For soils on foot slopes, the dominant pedogenic process involves the translocation of clay and subsequent formation of an argillic horizon. There are multiple levels of terraces and flood plains in the study area. The parent material is alluvium. Buried soils on both terraces and flood plains suggest periods of stability and soil formation followed by periods of additional deposition. The dominant pedogenic processes have been organic matter accumulation and redistribution of carbonates.

Global grassland ecosystem modelling: development and test of ecosystem models for grassland systems - Parton, W.J.; Coughenour, M.B.; Scurlock, J.M.O.; Ojima, D.S.; Gilmanov, T.G.; Scholes, R.J.; Schimel, D.S.; Kirchner, T.B.; Menaut, J.C.; Seastedt, T.R.; Moya, E.G.; Kamnalrut, A.; et al. (Global Change: Effects on Coniferous Forests and Grasslands, 1996)

Hydrogeology of thin-bedded limestones: the Konza Prairie Long-Term Ecological Research site, Northeastern Kansas - G. L. Macpherson (Journal of Hydrology, 1996)

Impact of climate and atmospheric carbon dioxide changes on grasslands of the world - Ojima, D.S.; Parton, W.J.; Coughenour, M.B.; Scurlock, J.M.O.; Kirchener, T.B.; Kittel, T.G.F.; Hall, D.O.; Schimel, D.S.; Moya, E.G.; Gilmanov, T.G.; Seastedt, T.R.; Kamnalrut, A.; et al. (Global Change: Effects on Coniferous Forests and Grasslands, 1996)

Impact of Ischnodemus falcus (Hemiptera: Lygaeidae) on photosynthesis and production of Spartina pectinata wetlands - Johnson, S.R. (Environmental Entomology, 1996)
Wetlands dominated by the C4 grass. Spartina pectinata (Link), were investigated to quantity the effects of high densities of lsehnodemus falicus (Say) on leaf-level photosynthesis and aboveground biomass production. Photosynthetic rates of plants within heavily infested stands were greatly reduced from that of plants supporting low densities of I. falicus. In early May 1993, photosynthetic rates of S. pectinata with minor I. falicus presence were >30 μmol m−2 s−1 with peak rates of 45 μmo1 m−2 s−1 in mid-June. In nearby infested S. pectinata wetlands, individual plants had rates as low as 5 μmol m−2 s−1 in early May and peak rates of 24 μmol m−2 s−1 in mid-July. Along with reduced photosynthetic rates, plants hosting high insect densities had lower aboveground production than did plants that had low insect densities. In 1994, when insect densities were ubiquitously low, there were no differences in peak photosynthetic rates or biomass accumulation between stands of S. pectinata that had been host to high versus low densities of insects in 1993. Thus, although infestation of I. falicus on S. pectinata had significant short–term effects, the lack of a long–term effect suggests that S. pectinata can successfully deal with periodic insect outbreaks.
Keywords: biomass; infestation; lschnodemus falicus; photosynthesis; prairie wetlands; Spartina pectinata

Interference competition from House wrens as a factor in the decline of Bewick's wrens - Kennedy, E.D.; White, D.W. (Conservation Biology, 1996)

Interspecific nutrient transfer in a tallgrass prairie plant community - Walter, L.E.F.; D.C. Hartnett; Hetrick, B.A.D.; Schwab, A.P. (American Journal of Botany, 1996)
Interplant nutrient transfer may be an important ecological process in grasslands, and may significantly influence plant neighborhood interactions. We investigated the potential for phosphorus transfer between the dominant grass Andropogon gerardii and several neighboring plant species in tallgrass prairie via a field 32PO4 labelling experiment. The mean amount of 32P received from donor shoots differed significantly among neighboring species and decreased with increasing distance from the donor. In general, forbs and cool-season C3 grasses received more labelled 32P than warm-season C4 grasses. Phosphorus transfer occurred over distances up to 0.5 m. The effects of species and distance on movement of phosphorus changed with increasing time after labelling. The relative mass of receiver and donor shoots did not affect amounts of 32P transfer. A benomyl fungicide treatment, applied to suppress mycorrhizal activity, likely did not affect existing vegetative hyphae and did not affect the amount of 32P transferred. These studies demonstrate that: (1) phosphorus is transferred among neighboring species in tallgrass prairie plant communities, (2) phosphorus may be transferred over significantly greater distances than reported in other grasslands, and (3) there is differential transfer among co-occurring species. Hypothesized mechanisms accounting for these patterns in tallgrass prairie include mycorrhizal hyphal interconnections and/or extensive and differential root and rhizosphere overlap among neighboring species.
Keywords: mycorrhizae; Phosphorus; tallgrass prairie

Microbial ecology and denitrification in tallgrass prairie and cultivated soils - Sotomayor, D. (Kansas State University, 1996)
Keywords: tallgrass prairie

Microcosms for aquifer research: Application to colonization of various sized particles by groundwater microorganisms - W. K. Dodds; Randel, C.; Edler, C. (Groundwater, 1996)
Flow-through microcosms were constructed to conduct ecological experiments on aquifer organisms. The two 5-channel microcosms were simple to construct, were fed by an artesian spring, and maintained close to in situ temperature and O2 concentrations. They were used to test relative microbial colonization of three substrate sizes: silt (0.063 mm), sand (0.9 mm), and gravel (3 mm). After 96 days of incubation, O2 microelectrode measurements revealed the lowest O2 tension in the silt, the highest in the gravel, and intermediate values in the sand. Microbial activity (3[H]-thymidine incorporation) was greatest in the gravel, followed by sand and then silt. Denitrification was greatest in the silt, followed by sand and then gravel. Microbial activity may be greatest with the largest particle size because of increased water exchange through pores, and denitrification may be greatest with the smallest particle sizes because of the occurrence of anaerobic microzones.

Mycorrhizthe responses of tallgrass prairie grasses from a central and a relictual site to inoculation with arbuscular al fungi in native and foreign combinations (big bluestem, Andropogon gerardii, Indiangrass (Sorghastrum nutans), Kansas, Colorado) - Fisher, D.M. (University of Colorado at Boulder, 1996)
This study was undertaken to determine whether arbuscular mycorrhizal (AM) fungal host specificity occurs within local sites. In addition, ecotypic variation in Big Bluestem (Andropogon gerardii) and Indiangrass (Sorghastrum nutans) from two sites was described and the responses of these hosts and their symbionts to drought was assessed in a greenhouse study
Keywords: tallgrass prairie

New technologies for remote sensing of ecosystem change in rangelands - Wessman, C.A.; Schimel, D.S.; S.R. Archer; Bateson, C.A.; Braswell, B.H.; Ojima, D.S.; Parton, W.J.; West, N.E. (Rangelands in A Sustainable Biosphere, 1996)
The collective area of rangelands, 40-50% of the global land surface, presents significant logistical challenges for obtaining ecological data for large, heterogeneous areas quickly, cheaply and with a significant level of accuracy. The use of remote sensing for rangeland monitoring and scaling up from plot to region is reviewed. A major challenge in remote sensing applications lies with assessing ecosystem function from spectral measurements of ecosystem structure. New methods which may assist in the identification and tracking of rangeland response to management practices at the regional scale and provide information on vegetation structure at the continental scale are described. On-going attempts to develop a coupled remote sensing rangeland ecosystem modelling approach for monitoring structure and quantifying energy flow and nutrient cycling are described and examples using Konza Prairie, Kansas, USA data are given

Nitrogen transport from tallgrass prairie watersheds - W. K. Dodds; John M. Blair; Henebry, G.M.; Koelliker, J.K.; Ramundo, R.A.; Tate, C.M. (Journal of Environmental Quality, 1996)
Discharge and N content of surface water flowing from four Karst watersheds on Konza Prairie Research Natural Area, Kansas, managed with different burn frequencies, were monitored from 1986 to 1992. The goal was to establish the influence of natural processes (climate, fire, and bison grazing) on N transport and concentration in streams. Streams were characterized by variable flow, under conditions that included an extreme flood and a drought during which all channels were dry for over a year. The estimated groundwater/stream water discharge ratio varied between 0.15 to 6.41. Annual N transport by streams, averaged across all watersheds and years, was 0.16 kg N ha−1 yr−1. Annual N transport per unit area also increased as the watershed area increased and as precipitation increased. Total annual transport of N from the prairie via streams ranged from 0.01 to 6.0% of the N input from precipitation. Nitrate and total N concentrations in surface water decreased (P < 0.001, r values ranged from 0.14–0.26) as length of time since last fire increased. Increased watershed area was correlated negatively (P < 0.0001) to stream water concentrations of NO−3N and total N (r values = −0.43 and −0.20, respectively). Low N concentration is typical of these streams, with NH+4-N concentrations below 1.0 µg L−1, NO−3-N ranging from below 1.4 to 392 µg L−1, and total N from 3.0 to 714 µg L−1. These data provide an important baseline for evaluating N transport and stream water quality from unfertilized grasslands.
Keywords: tallgrass prairie

Photosynthetic and stomatal responses to high temperature and light in two oaks at the western limit of their range - Hamerlynck, E.P.; Alan K. Knapp (Tree Physiology, 1996)
Bur oak (Quercus macrocarpa Michx.) and chinquapin oak (Q. muehlenbergii Engl.) leaves were exposed to high temperatures at various photosynthetic photon flux densities under laboratory conditions to determine if species-specific responses to these factors were consistent with the distribution of these oaks in gallery forests in the tallgrass prairies of northeastern Kansas, USA. Measurements of the ratio of chlorophyll fluorescence decrease, Rfd, indicated that chinquapin oak maintained greater photosynthetic capacity than bur oak across all tested combinations of irradiance (100, 400, 700 and 1000 μmol m−2 s−1) and temperature (40, 42, 44, 46 and 48 °C). In both oak species, manipulation of leaf temperature to about 47 °C for 45 min in the field led to a 45% decrease in carbon assimilation up to one week after the heat treatment, and to sharp reductions in stomatal conductance. Photosynthetic recovery patterns indicated that bur oak took longer to recover from heat stress than chinquapin oak, suggesting that heat stress may be important in determining distribution patterns of these oak species. Based on a comparison of the results with data from other forest species, we conclude that the photosynthetic temperature tolerances of bur oak and chinquapin oaks facilitate their dominance at the western limit of the eastern deciduous forest.
Keywords: Chlorophyll fluorescence; heat stress; Quercus macrocarpa; Quercus muehlenbergii

Photosynthetic and stomatal responses to variable light in a cool-season and warm-season prairie forb - Fay, P.A.; Alan K. Knapp (International Journal of Plant Science, 1996)
Species differences in photosynthetic and stomatal responses to steady-state and variable light were examined in two co-occurring tallgrass prairie forbs, the cool-season legume Baptisia bracteata var. glabrescens and the warm-season composite Helianthus annuus. Previous studies indicated that these species might have similar responses to short-term, minutes-long shade because of their similar growth forms. However, photosynthetic carbon gain, oxygen evolution, transpiration, and leaf xylem pressure potential measurements showed that Helianthus was far more responsive than Baptisia to changes in light availability. Helianthus had higher photosynthetic capacity, photosynthetic temperature optimum, stomatal conductance, and transpiration rates, rapid stomatal closure during shade, and delayed photosynthetic recovery when light levels increased, traits common to species exposed to high temperatures or periodic drought stress. Baptisia, active under cooler, wetter conditions than Helianthus, had lower photosynthetic capacity, photosynthetic temperature optimum, stomatal conductance, and transpiration, and no stomatal response to shade, responses typifying species that experience little water stress. We suggest that environmental and physiological factors may combine to reinforce greatly different photosynthetic and stomatal responses to short-term shade in species with similar growth form, especially in habitats with long, seasonally varying growing conditions.

Plant tolerance of gall-insect attack and gall-insect performance - Fay, P.A.; D.C. Hartnett; Alan K. Knapp (Ecology, 1996)
We examined plant tolerance of gall—insect attack and gall—insect performance in rosinweed (Silphium integrifolium, Asteraceae) and its apical meristem galler Antistrophus silphii (Hymenoptera: Cynipidae). Gall densities were varied in field rosinweed populations, while gall densities, water, and nutrients were varied for rosinweed in an experimental garden. Field plants grew under prevailing resource and competitive conditions, but garden plants grew free from competition, so gall—insect impacts, rosinweed regrowth, and gall—insect performance were observed under widely different growing conditions. Seasonal measures of rosinweed growth and leaf physiology, and end—of—season measures of biomass, reproduction, gall—wasp emergence, growth, sex ratios, and parasitism were made for both experiments. Rosinweed poorly tolerated Antistrophus gall damage in the field. Galls reduced plant height, leaf area, and inflorescence production. Rosinweed diverted biomass to stems, but produced no regrowth from axillary meristems. In the garden, rosinweed was much more tolerant of Antistrophus gall damage. Galls initially reduced plant height and leaf area, but axillary meristems grew profusely after gall formation, producing nearly all galled plant inflorescences and more than replacing leaf area initially lost to gall formation. Water— and nutrient—supplemented rosinweed were most tolerant of gall damage, experiencing little loss of total biomass or reproductive output. Field rosinweed failed to mount a tolerance—enhancing regrowth response because galls, resource availability, and competition combined to constrain axillary meristem growth. Gall—wasp performance was largely independent of rosinweed tolerance. Emergence, growth, sex ratios, and parasitism were comparable in field and garden, and only slightly affected by resource availability. Gall—insect performance may be buffered from environmental variation, disconnecting plant and herbivore population dynamics. Rosinweed's poor tolerance of gall damage may typify forb responses to herbivory in highly competitive grassland plant communities.

Potentially mineralizable N as an indicator of active soil nitrogen - Drinkwater, L.E.; Cambardella, C.A.; Reeder, J.D.; C. W. Rice (Methods for Assessing Soil Quality, 1996)

Prairie ecology-the tallgrass prairie - Steinauer, E.M.; Scott. L. Collins (Prairie Conservation-Preserving North America's Most Endangered Ecosystem, 1996)
Keywords: tallgrass prairie

The relationship of floods, drying, flow and light to primary production and producer biomass in a prairie stream - W. K. Dodds; Hutson, R.E.; Eichem, A.C.; Evans, M.E.; Gudder, D.A.; Fritz, K.M.; Gray, L. (Hydrobiologia, 1996)
Factors related to autochthonous production were investigated at several sites along a prairie stream at Konza Prairie Research Natural Area. Primary production, algal biomass, litter input, and ability of floods to move native substrate were measured. Additional experiments were conducted to establish the influence of light and water velocity on primary production rates and recovery of biomass following dry periods. The study period encompassed two extreme (> 50 year calculated return time) floods, thus we were able to analyze the effects of scour on periphyton biomass and productivity. Biomass of sedimentary algae was reduced greatly by flooding and did not reach preflood amounts during the 2 months following the first flood. Rates of primary production associated with sediments recovered to levels above preflood rates within 2 weeks. Biomass of epilithic periphyton was not affected as severely as that of sedimentary algae. Little relationship was observed between water velocity and photosythetic rates. Production reached maximum rates at 25% of full sun light. Epilithic chlorophyll levels recovered within eight days following a dry period, and chl a was an order of magnitude greater on rocks than sediments 51 days after re-wetting. Estimated annual rates of primary production were 2.6 times greater in the prairie than in the forest reaches of the stream. The ratio of annual autochthonous:allochthonous carbon input was 4.81 for prairie and 0.32 for the forest. Periphyton production in prairie streams is resilient with regard to flooding and drought and represents a primary carbon source for the system.
Keywords: autochthonous; Flood; light; periphyton; Primary production; water velocity

Responses in stomatal conductance to elevated CO2 in 12 grassland species that differ in growth form - Alan K. Knapp; Hamerlynck, E.P.; J.M. Ham; Owensby, C.E. (Vegetatio, 1996)
Responses in stomatal conductance (g st ) and leaf xylem pressure potential (ψ leaf ) to elevated CO2 (2x ambient) were compared among 12 tallgrass prairie species that differed in growth form and growth rate. Open-top chambers (OTCs, 4.5 m diameter, 4.0 m in height) were used to expose plants to ambient and elevated CO2 concentrations from April through November in undisturbed tallgrass prairie in NE Kansas (USA). In June and August, ψ leaf was usually higher in all species at elevated CO2 and was lowest in adjacent field plots (without OTCs). During June, when water availability was high, elevated CO2 resulted in decreased g st in 10 of the 12 species measured. Greatest decreases in g st (ca. 50%) occurred in growth forms with the highest potential growth rates (C3 and C4 grasses, and C3 ruderals). In contrast, no significant decrease in g st was measured in the two C3 shrubs. During a dry period in September, reductions in g st at elevated CO2 were measured in only two species (a C3 ruderal and a C4 grass) whereas increased g st at elevated CO2 was measured in the shrubs and a C3 forb. These increases in g st were attributed to enhanced ψ leaf in the elevated CO2 plants resulting from increased soil water availability and/or greater root biomass. During a wet period in September, only reductions in g st were measured in response to elevated CO2. Thus, there was significant interspecific variability in stomatal responses to CO2 that may be related to growth form or growth rate and plant water relations. The effect of growth in the OTCs, relative to field plants, was usually positive for g st and was greatest (>30%) when water availability was low, but only 6–12% when ψ leaf was high. The results of this study confirm the importance of considering interactions between indirect effects of high CO2 of plant water relations and direct effects of elevated CO2 on g st , particularly in ecosystems such as grasslands where water availability often limits productivity. A product of this interaction is that the potential exists for either positive or negative responses in g st to be measured at elevated levels of CO2.
Keywords: elevated CO2; Growth form; Stomatal Conductance; tallgrass prairie; Water relations

Responses of a C4 grass and three C3 forbs to variation in nitrogen and light in tallgrass prairie - Turner, C.T.; Alan K. Knapp (Ecology, 1996)
In tallgrass prairie, high plant species diversity results not from a large number of grass species, but from a large number of forb (nongrass, herbaceous) species. Forbs exhibit morphological, life history, and ecophysiological characteristics that contrast sharply with those of the dominant C4 grasses. Success of the subdominant forbs varies strongly with topographic position and burning regime, and landscape scale patterns of abundance are well documented. But comparatively little is known about the mechanisms determining these patterns in persistent tallgrass prairie forbs. To elucidate these mechanisms, (1) leaf—level physiological characteristics of the dominant C4 grass, Andropogon gerardii, and four co—occurring C3 forbs were measured in response to natural and experimentally manipulated gradients of N availability, and (2) seasonal light environments of forbs in contrasting topographic positions and burning regimes and their morphological and physiological responses in these environments were compared to determine whether resource availability and utilization patterns contributed to patterns of forb distribution and abundance. The effects of burning regime and topographic position on maximum rate of photosynthesis (A) and stomatal conductance to water vapor (g) measured at the leaf level were not consistent with patterns of forb abundance. Nitrogen did not appear to limit forb physiological processes, even though increased N availability resulted in higher tissue N concentrations and greater biomass. There was no consistent increase in (A) or decrease in (g) in response to fertilization. However, (A) at low light levels was as much as 67% higher in fertilized Vernonia baldwinii and A. gerardii compared to unfertilized plants. Greater light availability to forbs in the canopy was associated with lower grass biomass production in uplands compared to lowlands and in unburned compared to burned sites. Forbs did not appear to adjust morphologically (leaf area and plant height) to different light environments at different sites. As a result, as much as 90% of forb leaf area in the burned lowland was displayed in low light, whereas as little as 30% of forb leaf area was in low light in the uplands at midseason. Estimates of potential whole—plant carbon uptake, based on leaf area distribution relative to available light and (A) as a function of light availability, agreed well with patterns of forb abundance and production. Differences in light availability may account for much of the variability in forb abundance related to burning regime and topographic position by limiting carbon gain in forbs more in burned lowlands than in other sites.
Keywords: tallgrass prairie

Responses of two forbs, Solidago canadensis and Vernonia baldwinii , to variation in nitrogen availability and light environments in lowland, annually burned tallgrass prairie - Davy, A.L. (Kansas State University, 1996)
Keywords: tallgrass prairie

Retranslocation of shoot nitrogen to rhizomes and roots in prairie grasses may limit loss of N to grazing and fire during drought - Heckathorn, S.A.; DeLucia, E.H. (Functional Ecology, 1996)
1. It has previously been shown that perennial C4 grasses of tallgrass prairie retranslocate up to 30% of shoot nitrogen (N) to rhizomes and roots in response to water stress and that retranslocation contributes to drought-related decreases in shoot N concentration and photosynthetic capacity, resulting in decreased post-drought carbon gain for 1-2 weeks. 2. In this paper the following hypothesis is tested: under N-limited conditions, the benefits of retranslocation may include limiting loss of shoot N to grazing (or fire) during drought, resulting in increased end-of-season whole-plant biomass, N content, and reproduction. All shoot tissue was removed from young N-limited plants either before or after drought, thereby preventing or allowing the opportunity for retranslocation, and the effects of each clipping treatment on biomass and N content after flowering and senescence were determined. 3. In Spartina pectinata, a mesic species that remobilizes 20-30% of shoot N during drought, plants clipped before drought (no retranslocation) had decreased biomass, N content, and tiller (but not seed) production relative to plants clipped after drought. In contrast, Schizachyrium scoparium, a xeric species that retranslocates little shoot N, exhibited decreased biomass, N content, and tiller and seed production in plants clipped after drought: the result of growth-related increases in total shoot N during drought, and thus greater N loss in plants clipped after drought. Time of clipping had no effect on Andropogon gerardii, a species of intermediate drought tolerance that retranslocates ca. 10% of shoot N during drought. 4. These results support the hypothesis that drought-induced shoot N retranslocation to below-ground tissues represents a trade-off between N protection and post-drought carbon assimilation in prairie grasses.
Keywords: fire

Role of microbial biomass C and N in soil quality - C. W. Rice; Moorman, T.; Beare, M. (Methods for Assessing Soil Quality, 1996)

Seasonal NDVI trajectories in response to disturbance: toward a spectral-temporal mixing model for tallgrass prairie - Goodin, D.G.; Henebry, G.M. (IEEE, 1996)
Natural and anthropogenic disturbance in tallgrass prairie communities can induce changes in plant species composition, including shifts in abundance of C3 vs. C4 lifeforms. The asynchronous seasonalities in greenness that C3 and C4 species exhibit should enable monitoring of their relative abundance using sensor derived vegetation indices, such as NDVI. The authors used close-range measurements made over 22 experimental. Plots at the Konza Prairie Research Natural Area (KPRNA) to evaluate seasonal trajectories in canopy greenness as a function of C3/C4 ratio. NDVI data were collected from each plot at approximately ten day intervals throughout the 1995 growing season. Temporal trajectories were used to develop discriminant functions to model relative C3/C4 abundances. The discriminant model yielded values of Kendall's τb and Cohen's κ statistic of 0.794 and 0.781, indicating strong agreement between classes and an overall classification significantly better than random assignment. Results suggest the possibility of applying spectral-temporal mixture models derived from close-range sensing to larger scale monitoring of tallgrass prairie
Keywords: tallgrass prairie

Soil invertebrates as indicators of soil quality - John M. Blair; Bohlen, P.J.; Freckman, D.W. (Methods for Assessing Soil Quality. SSSA Special Publication, 1996)

Spatial and temporal patterns in functional diversity - Scott. L. Collins; Benning, T.L. (Biodiversity: A Biology Of Numbers and Difference, 1996)

Spatio-temporal dynamics of soil moisture in tallgrass prairie using ERS-1 SAR image time series: first year results - Henebry, G.M.; Alan K. Knapp (IEEE, 1996)
Radar remote sensing of soil moisture has been demonstrated in croplands and rangelands. The authors are interested in synoptic estimates of soil moisture to aid long term ecological investigation of tallgrass prairie and have initiated a three year study to develop this technology. The authors' study area, Konza Prairie Research Natural Area (KPRNA), exhibits a variety of factors to complicate soil moisture estimation via synthetic aperture radar (SAR) including significant terrain variation, heterogeneous soil types and depths, and watershed-level experimental treatments including prescribed burning, grazing by large ungulates, and water supplementation. Several indicators of the moisture status of soil-water-vegetation continuum were gathered during the 1995 growing season including soil moisture via neutron probe and TDR, xylem pressure,potential values, and aboveground biomass (wet and dry weights). Due to orbital track overlap, eleven ERS-1 SAR images of KPRNA were acquired from mid-April to early October. Spring through mid-summer were unusually cool and wet, thereby delaying phenological development and attenuating the water stress typical of the later growing season. Backscattering values show some consistent agreement with ground data. Watersheds burned in April showed markedly higher backscattering at the end of the growing season due to a lack of litter layer from previous seasons' growth. Grazed units that were also burned showed the highest backscattering caused by no litter layer and more exposed soil
Keywords: tallgrass prairie

Trophic interactions and plant species richness along a productivity gradient - Moen, J.; Scott. L. Collins (Oikos, 1996)
We analyzed the interactive effects of trophic structure and disturbance on species diversity of plant communities along a productivity gradient by merging the intermediate disturbance hypothesis with a simple three-trophic-level predator-prey model. In two-trophic-level systems, i.e. without carnivores, the model produces a unimodal, hump-shaped pattern of species richness, which is consistent with patterns predicted from other models. If carnivores are included, trophic cascades produce a bimodal pattern of species richness over the productivity gradient. We have found no appropriate data sets in the literature with which to assess the validity of our model. We thus offer the model as an alternative hypothesis to be tested regarding plant species richness in productivity gradients, and as a reminder of the importance of trophic structure for patterns and processes in plant communities.

Use of coleopteran prey by Phidippus audax (Araneae, Salticidae ) in tallgrass prairie wetlands - Johnson, S.R. (The Journal of Arachnology, 1996)
Phidippus audax (Hentz 1845) was observed in the field and tested in a laboratory in order to estimate its use of two locally abundant, soft-bodied coleopteran species, Diabrotica undecimpunctata (Chrysomelidae, Galerucinae) and Chauliognathus pennsylvanicus (Cantharidae). In the field, Phidippus audax was most commonly observed hunting on leaves or stems of the common milkweed and feeding upon species of Diptera or Diabrotica undecimpunctata. Despite high densities of Chauliognathus pennsylvanicus, P. audax was never observed feeding upon this species. In laboratory feeding trials, P. audax always retreated from C. pennsylvanicus and always attacked D. undecimpunctata. Also, P. audax retreated from models displaying the markings of C. pennsylvanicus in 88% and attacked models displaying the markings of D. undecimpunctata in 85% of the laboratory trials.
Keywords: tallgrass prairie

Ammonia volatilization during drought in perennial C4 grasses of tallgrass prairie - Heckathorn, S.A.; DeLucia, E.H. (Oecologia, 1995)
We measured foliar NH3 volatilization as part of our study of the decrease (up to 40%) in shoot N concentration during drought in three perennial C4 grasses of tallgrass prairie. Volatilization of recently expanded leaves was quantified using cuvettes and acid traps for Spartina pectinata, Andropogon gerardii, and Schizachyrium scoparium, a mesic, intermediate, and xeric species, respectively. In general, volatilization decreased during drought, approaching zero as stomates closed, and increased with plant N status and drought tolerance. Prior to drought, NH3 volatilization was greater in xeric than mesic species (179 and 131 vs. 115 ng m-2 s-1 for individual leaves of S. scoparium and A. gerardii vs. Sp. pectinata). During a 2–3 week drought, whole-shoot volatile N losses can exceed 5% of total plant N in these species, accounting for 2–10% of the decrease in shoot percent N (again, xeric > mesic). Drought-induced N retranslocation of shoot N to roots and rhizomes is responsible for c. 63% of the decrease in percent N in Sp. pectinata, 28% in A. gerardii, and 8% in S. scoparium. The remainder of the decrease in percent N is attributable to growth dilution of existing shoot N, accounting for 34, 65, and 87% of the decrease in shoot percent N during drought in Sp. pectinata, A. gerardii, and S. scoparium, respectively. Thus, the relative importance of volatilization, retranslocation, and dilution in decreasing foliar percent N during drought in prairie grasses is species dependent and related to drought tolerance.
Keywords: Ammonia volatilization; Drought; Nitrogen Prairie grasses; Retranslocation

Antimicrobial activity of dogwood fruits (Cornus drummondii) from winter food caches of the eastern woodrat (Neotoma floridana ) - Post, D.M.; Urban, J.E. (Journal of Chemical Ecology, 1995)
Post-harvest loss of resources to microbial competitors affects a number of species of animals, and many of them have evolved behaviors that reduce the likelihood of such loss. We previously described the inhibition ofBacillus psychrophilus by dogwood fruits (Cornus drummondii), which can comprise a significant portion of the winter food cache of the eastern woodrat (Neotoma floridana). The present study is a further investigation of the ability of dogwood fruits to inhibit growth ofB. psychrophilus. Additionally, we tested the antimicrobial activity of dogwood fruits onEscherichia coli andStaphlococcus aureus. Results of our study indicate that fresh fruits inhibit the growth ofB. psychrophilus andS. aureus but notE. coli. However, fruits taken from woodrat dens after four and six months storage inhibited growth of all three species of bacteria. Further, the strength of inhibition increased over the test period. We suggest the presence of an inhibitor allows woodrats to compete effectively for a valuable and limited food resource.
Keywords: antimicrobial activity; Bacillus psychrophilus; caching; Cornus drummondii; dogwood fruit; eastern woodrat; Escherichia coli; Neotoma floridana; Staphlococcus aureus

Bison selectivity and grazing responses of little bluestem in tallgrass prairie - Pfeiffer, K.E.; D.C. Hartnett (Journal of Range Management, 1995)
The perennial bunchgrass little bluestem (Schizachyrium scoparium [Michx.] Nash) was examined in a 5-yr study on tallgrass prairie to determine how fire influences its use by bison and its responses to grazing. On unburned prairie, bison grazed only 5% of the available little bluestem, selecting it only 30% as frequently as big bluestem, the dominant co-occurring species. On burned prairie, grazing frequency of little bluestem was over 3-fold greater and equal to that of its dominant neighbor. Grazing frequency of little bluestem was affected by plant size (basal area). On burned sites, plants of intermediate size classes were least abundant (<10% of total) but were grazed most frequently (>50%). Small plants were most abundant but were grazed least frequently. Density, tiller numbers, and basal area of little bluestem were significantly greater in annually burned compared to infrequently burned sites but were decreased by > 50% in grazed compared to ungrazed sites. Grazing shifted the population size distribution toward higher frequencies of smaller individuals (< 50 cm2 basal area), whereas burning increased the frequency of large (> 200 cm2 basal area) individuals. In unburned prairie, little bluestem accumulates a persistent clump of standing dead tillers that appear to serve as a physical deterrent to grazing. Although burning enhances its growth, it also removes its canopy of dead tillers exposing the plant to grazers. The shift in population structure toward a high frequency of smaller (and perhaps less drought- or grazing-tolerant) individuals may contribute to the decline of little bluestem populations under persistent grazing. Thus, plant growth form, population size structure, and fire interact to influence bison grazing patterns and responses of little bluestem to grazing on tallgrass prairie.
Keywords: tallgrass prairie

Comparative gas exchange and nitrogen responses of the dominant C4 grass, Andropogon gerardii, and five C3 forbs to fire and topographic position in tallgrass prairie during a wet year - Turner, C.T.; Kneisler, J.R.; Alan K. Knapp (International Journal of Plant Science, 1995)
High plant species diversity in tallgrass prairie results not from a large number of grass species but, rather, from a large number of forb (nongrass, herbaceous) species. Although morphological characteristics of tallgrass prairie forbs differ strongly from those of the grasses and their patterns of abundance vary substantially with burning regime and topographic position, comparatively little is known about the ecology of persistent tallgrass prairie forbs. We measured leaf-level physiological characteristics of the dominant C4 grass, Andropogon gerardii, and five co-occurring C3 forb species in response to burning regime and topographic position to determine if there were either absolute or seasonal differences in resource utilization patterns that could contribute to the patterns of forb distribution and abundance in tallgrass prairie. In a wet year, neither fire nor topographic position affected leaf-level physiological characteristics in the grass and forbs studied, and thus responses were not consistent with extant patterns of forb abundance (greater forb abundance in unburned and upland sites). Water use efficiency in A. gerardii was 40%-170% greater and foliar N concentration was consistently lower in the grass than in the forbs, but there were no distinct or consistent differences between the grass and forbs in maximum rates of photosynthesis and stomatal conductance or xylem pressure potential. Moreover, seasonal patterns of gas exchange in forbs and the grass were not different, as might be expected when comparing C3 and C4 species. These results indicate that, when assessed at the leaf level, responses of these prairie plants to fire or topographic position during a wet year are not indicative of their success in these sites. However, seasonal water stress is a typical feature of the tallgrass prairie environment and water use patterns indicate that the prevalence of soil moisture limitations in most years may be a key factor influencing plant distribution and success in this ecosystem.
Keywords: tallgrass prairie

Comparison of spatial and temporal variability of ecological parameters from 12 North American ecosystems - Kratz, T.K.; Magnuson, J.J.; Bayley, P.; Benson, B.J.; Berish, C.W.; Bledsoe, C.S.; Blood, E.R.; Bowser, C.J.; Carpenter, S.R.; Cunningham, G.L.; Dahlgren, R.; Frost, T.M.; et al. (Evaluating And Monitoring The Health Of Large-Scale Ecosystems, NATO ASI series, Vol I 28, 1995)

The coyote: an indicator species of environmental change on the great plains - Gipson, P.S.; Brillhart, D.E. (Our living resources: a report to the nation on the distribution, abundance, and health of U.S. plants, animals, and ecosystems, 1995)

Dynamics of big bluestem (Andropogon gerardii) in ungrazed tallgrass prairie - D.J. Gibson; Towne, E.G. (1995)

The ecophysiology of bur oak (Quercus marocarpa Michx.) and chinquapin oak (Quercus muehlenbergii Emglm.) at the western limit of their distribution - Hamerlynck, E.P. (Kansas State University, 1995)
Keywords: Ecophysiology

Effect of topography on the distribution of small mammals on the Konza Prairie Research Natural Area, Kansas - Kaufman, G.K.; D.W. Kaufman; Brillhart, D.E.; Finck, E.J. (1995)

Effects of bison grazing, on floristic diversity in tallgrass prairie - D.C. Hartnett; Hickman, K.R.; Walter, L.E.F. (1995)
Keywords: tallgrass prairie