Effects of urine deposition on small\-scale patch structure in prairie vegetation - Steinauer, E.M.; Scott. L. Collins (Ecology, 1995)
Large grazing mammals contribute to the species diversity of grasslands via direct and indirect effects of defoliation and urine deposition. We examined the influence of one and two applications of simulated bovine urine on vegetation structure on (1) tallgrass prairie burned either every 2 or 4 yr at Konza Prairie Research Natural Area (KPRNA), Kansas, and (2) unburned sandhills prairie at the Niobrara Valley Preserve, Nebraska. We also examined the influence of urine and the clipping of graminoids on an annually burned site at KPRNA. Plant abundance in general increased on urine patches but the response appeared dependent on litter accumulation. C"4 grasses increased at the annual burn and Niobrara sites where litter levels were low. C"3 forbs increased at the 2- and 4-yr burn sites where litter levels were high. Urine treatment significantly affected community composition at all but the 2-yr burn site. Alpha-diversity decreased on urine patches at the annual and 4-yr burn sites but increased on urine patches at the Niobrara site. Beta-diversity increased on urine patches at the annual burn and Niobrara site but decreased on urine patches at the 4-yr burn site. The clipping of graminoids at the annual burn site reduced both @a- and @b-diversity and graminoid abundance while forb abundance was not affected.

Elemental analysis of mineral lick soils from the Serengeti National Park, the Konza Prairie and Yellowstone National Park - Tracy, B.F.; McNaugthon, S.J. (Ecography, 1995)
We analyzed mineral lick soils and non-mineral lick soils from the Serengeti National Park, the Konza Prairie, and Yellowstone National Park. The concentrations of 14 different elements considered important for ungulate nutrition were analyzed to determine the relative importance of Na vs other elements in attracting animals to lick areas. Only Na was consistently higher in the mineral lick soils of the three ecosystems. Mean Na concentrations were c. 20× greater in Serengeti licks, 10× greater in Konza licks and 3× greater in Yellowstone licks compared to the respective non-lick soils. Despite the numerous elements analyzed for this survey, our results suggest that Na is the primary element initiates mineral lick use in these widely separated ecosystems. The widespread distribution of Na-deficient forage likely explains the importance of Na in most mineral licks.

Environmental and physiological factors influencing the distribution of oaks near the edge of their range - Hamerlynck, E.P.; Alan K. Knapp (1995)

Experimental analysis of intermediate disturbance and initial floristic composition: decoupling cause and effect - Scott. L. Collins; Glenn, S.M.; D.J. Gibson (Ecology, 1995)
The intermediate disturbance hypothesis predicts that richness will be highest in communities with moderate levels of disturbance and at intermediate time spans following disturbance. This model was proposed as a nonequilibrium explanation of species richness in tropical forests and coral reefs. A second model of succession, initial floristic composition, states that nearly all species, including late seral species, are present at the start of succession. This leads to the prediction that richness should be highest immediately following disturbance. We tested these predictions using plant species composition data from two long—term field experiments in North American tallgrass prairie vegetation. In contrast to one prediction of the intermediate disturbance hypothesis, there was a significant monotonic decline in species richness with increasing disturbance frequency, with no evidence of an optimum, in both field experiments. Species composition on an annually burned site was a subset of that of infrequently burned sites. The average number of species per quadrat and the number of grass, forb, and annual species were lowest on annually burned sites compared to unburned sites and sites burned once every 4 yr. The second prediction of the intermediate disturbance hypothesis, however, was supported. Richness reached a maximum at an intermediate time interval since the last disturbance. This contradicts the prediction from the initial floristic composition model of succession. These results also suggest that the two predictions of the intermediate disturbance hypothesis are independent and unrelated. We propose that this may be explained by uncoupling the effects of disturbance as a single, relatively discrete event from system response to disturbance. From this perspective, disturbance becomes an extinction—causing event in these grasslands, where recovery following disturbance is a balance between immigration and extinction.

Fine-scale spatial organization of tallgrass prairie vegetation along a topographic gradient - Bartha, S.; Scott. L. Collins; Glenn, S.M.; Kertesz, M. (Folia Geobot.Phytotax, Praha, 1995)
Fine-scale spatial patterns of native tallgrass prairie vegetation were studied on Konza Prairie, Kansas, USA. Three sites, upland, slope, and lowland, were sampled in an ungrazed watershed. Presence of vascular plant species was recorded in two 25.6 m long transects of contiguous 5×5 cm micro-quadrats on each topographic position. Spatial patterns of species and functional groups were analyzed by information theory models ofJuhász-Nagy. Within-community variability of coexistence was expressed by the diversity and spatial dependence of local species combinations. Considerable diversity in the local coexistence of species was found on each site. Upland and hillside communities were richer and more diverse in species combinations than lowland. Spatial scale effected coexistence relationships. The maxima of information theory estimates varied between 15 and 30 cm. There was no trend in the variation of characteristic scales along the topographical gradient. Above 10 m, all sites tended to be homogeneous. The analysis of spatial associations revealed that variability in the local coexistence of species was strongly constrained in all topographic positions. Overall spatial association of species was the lowest on lowland. The characteristic scales of maximum association were between 1.2 m and 3 m at all sites. The maxima of information theory estimates for the functional group-based data appeared at smaller plot sizes than for the species based analyses. Only weak spatial associations were detected among the functional groups indicating that individuals of functional groups coexist well at small scales, and form combinations close to random expectations. The length of transects did not effect the relative associations. Strong positive correlations were found between the number of components (species or functional groups) and the maxima, of information theory models suggesting that richness is a good predictor of within-community coexistence relations. However, there was no relationship between richness and the characteristic scales of community patterns.
Keywords: diversity; Functional groups; Grassland community; information theory; Konza Prairie; Scaling; Spatial associations

Gas exchange and reproduction of Spiranthes vernalis (Orchidaceae) in a Kansas tallgrass prairie - Johnson, S.R. (1995)
Keywords: tallgrass prairie

Gas exchange characteristics of Typha latifolia L. from nine sites across North America - Alan K. Knapp; Yavitt, J.B. (Aquatic Biology, 1995)
Gas exchange characteristics were measured in the field for nine populations of Typha latifolia L. from Florida to Minnesota in North America. These populations spanned a substantial gradient in growing season length and environmental conditions. The purpose of this study was to assess geographic variability in stomatal conductance (gst) in T. latifolia populations, as well as to identify key environmental and plant factors that may affect gst and, potentially, trace gas emissions through stomata. Midday rates of net photosynthesis (A) and gst were measured under full sunlight conditions at each site, and more intensive measurements of diurnal and seasonal variability were made at selected sites. In general, A varied less than gst (1.5 vs. 3 fold) among sites with maximum A (27.4 μmol m−2 s−1) and gst (1076.7 mmol m−2 s−1) measured at the southern sites. We found that A and gst in T. latifolia increased significantly with increasing temperature and light level, and varied diurnally and seasonally. Moreover, stomata closed completely at night, in contrast to some other wetland plants. Both A and gst also increased significantly along the length of leaves from the base of plants to the upper canopy. Finally, although gst was quite variable, A did not appear to be limited by gst under typical field conditions. It was concluded that generalizations that stomata in wetland plants are relatively unresponsive to environmental factors are not consistent with field responses measured in T. latifolia. As a result, because gst may influence trace gas flux in this species, spatial and temporal variations in gst need to be considered when emissions are estimated.

Geomorphology of the N4D watershed, Konza Prairie Research Natural Area, Riley and Geary Counties, Kansas - Ross, K.L. (Kansas State University, 1995)

Grassland ecosystem and landscape dynamics - Scott. L. Collins; Glenn, S.M. (The Changing Prairie, 1995)

The influence of crowding and pocket gopher disturbance on growth and reproduction of a biennial, Tragopogon dubius - Reichman, O.J. (1995)

Influence of fire frequency and burning date on the proportion of reproductive tillers in big bluestem and indiangrass - Towne, E.G. (1995)
Keywords: fire

The influence of fire on Spartina pectinata wetland communities in a northeastern Kansas tallgrass prairie - Johnson, S.R.; Alan K. Knapp (Canadian Journal of Botany, 1995)
Wetlands dominated by the C4 grass Spartina pectinata were investigated to quantify differences in plant species composition and diversity in response to fire frequency. The study site was a tallgrass prairie in northeastern Kansas that included Spartina wetlands subjected to spring fires at 1-, 2-, 4-, 10-, and 20-year intervals. Because C3 forbs in these wetlands responded strongly to different fire frequencies, the light environment and gas exchange responses of the ubiquitous forb Asclepias syriaca were also assessed. In general, species diversity was lower in annually burned wetlands because of lower forb diversity. Maximum H′ in annually burned sites was 1.64 versus 2.77 in 10- and 20-year burned sites. However, individual forb responses varied. Asclepias increased and Solidago canadensis and Galium aparine decreased in importance with increasing fire frequency. Canopy sunlight interception was greater in annually burned wetlands than in wetlands with lower burn frequencies. Despite reduced light availability, midseason photosynthetic rates of Asclepias were higher in annually burned sites. The results suggest that frequent fire in tallgrass prairie wetlands results in less diverse plant communities, similar to responses of upland prairie, and that the timing of fire, relative to life history and phenology of the subordinate species, strongly influences responses of individual forbs. Key words: wetlands, tallgrass prairie, Spartina pectinata communities, fire.
Keywords: tallgrass prairie

Influences of earthworms on biogeochemistry - John M. Blair; Parmelee, R.W.; Lavelle, P. (Earthworm Ecology and Biogeography in North America, 1995)

Interannual variability in primary production in tallgrass prairie: climate, soil moisture, topographic position and fire as determinants of aboveground biomass - J. M. Briggs; Alan K. Knapp (American Journal of Botany, 1995)
From 1975 to 1993, aboveground net primary production (NPP) at the Konza Prairie Research Natural Area in NE Kansas varied from 179 g/m2 to 756 g/m2. Across a variety of sites, NPP was significantly related to precipitation (r2 = 0.37), but much variability was unexplained. Thus, we evaluated the relationship between NPP with meteorological variables and soil moisture measurements in tallgrass prairie sites that varied in fire frequency and topographic position. Annually burned lowland sites had significantly higher NPP than either annually burned upland or unburned sites. NPP in burned sites was more strongly related to meteorological variables and soil moisture when compared to unburned sites. The lack of significant correlation between soil moisture with NPP on unburned sites suggests that factors other than water availability limit production in these sites. When NPP data were analyzed separately by life forms, interannual variability in forb NPP was not correlated with any meteorological variables, but was negatively correlated with grass NPP (r = -0.49). The inability of a single factor, such as precipitation to explain a large portion of the interannual variability in NPP is consistent with the concept that patterns of NPP in tallgrass prairie are a product of spatial and temporal variability in light, water, and nutrients, driven by a combination of topography, fire history, and climate.
Keywords: tallgrass prairie

Landscape-level interactions between topoedaphic features and nitrogen limitation in tallgrass prairie - Benning, T.L.; Seastedt, T.R. (Landscape Ecology, 1995)
Transects across watersheds with varying fire histories and remotely-sensed data were used to study vegetation-resource interactions in a tallgrass prairie in Kansas. Paired plots (fertilized, control) were established along these transects and sampled for grass and forb biomass during the 1989 and 1990 growing seasons. Fertilization resulted in significant production responses in grass and total biomass on the west slopes of the annually burned (ID) and infrequently burned (N4) watersheds for both years (p = 0.05). In 1989, fertilization also produced a significant increase in grass biomass on the west slope of the unburned transect (p = 0.05), however, total production was not significantly increased. East slopes were insensitive to nitrogen additions. Differences in production response along these transects were assessed by testing the interaction between fertilization response and slope position. Significant interactions occurred on both 1D and N4, but only in 1990. Production data for both years were also compared to Normalized Difference Vegetation Index (NDVI) values derived from thematic mapper (TM) images for 1989 and 1990. When differences among transects or watersheds were statistically different, a positive relationship between NDVI and biomass was observed. NDVI values accurately reflected the spatial patterns of production along these transects for both years although not necessarily the magnitude.
Keywords: fire; NDVI; nitrogen; transect; Watersheds

Local distribution of prairie voles (Microtus ochrogaster) on Konza Prairie: effect of topographic position - Bixler, S.H.; D.W. Kaufman (Transactions of the Kansas Academy of Science, 1995)
Prairie voles (Microtus ochrogaster) were studied in ungrazed tallgrass prairie on the Konza Prairie Research Natural Area near Manhattan, Kansas in 1984-1987. Prairie voles on our topographically diverse site demonstrated a nonrandom association with topography as upland prairie was preferred over lowland and slope prairie. Preference for upland was highly consistent among male and female residents and nonresidents, however, absolute strengths of the preference for upland did differ among years and among sex-residency classes. For example, female residents were associated more strongly with upland prairie than were male residents, whereas male residents were more likely to be captured in lowland prairie than were female residents. Patterns of use of the three topographic positions also were more variable between years and between males and females for nonresidents than residents. The latter difference was consistent with nonresidents, in part, being dispersing voles that were moving through less than optimal habitat in their search for permanent home sites.

The measurement of stability in grasslands - Scott. L. Collins (Trends in Ecology and Evolution, 1995)

Measurements of water use by prairie grasses with heat balance sap flow gauges - Senock, R.S.; J.M. Ham (Journal of Range Management, 1995)
Direct and continuous measurements of water use by range grasses are needed by both range scientists and land managers. This study tested a heat balance sap flow gauge on individual culms of the tallgrass prairie species big bluestem (Andropogon gerardii Vitman) and indiangrass [Sorghastrum nutans (L.) Nash]. Gauge performance was evaluated on potted plants in the laboratory, greenhouse, and field by comparing sap flow to gravimetric measurements of transpiration. In the laboratory, gauge-measured water loss was consistently within ±10% of gravimetric measurements for both species at flow rates ≤ 4 g $\text{hour}^{-1}$. The first-order time constant of the gauge was calculated to be <20 seconds. In the greenhouse, sap flow estimates were consistently below gravimetric water loss and negative flows were often computed because of suspected errors in the radial heat flux component. Laboratory data showed that despite the gauge being surrounded with insulation, errors in the heat balance could occur because of external air temperature changes. In the field, environmental alterations in the stem energy balance affected the accuracy of gauges placed outside a plant canopy, but accurate measurements did occur when the plants were placed within a plant canopy. Heat transfer analysis indicated that foam insulation should be 20 to 25 mm thick to minimize the effect of the environment on gauge performance.

Methane emissions to the atmosphere through emergent cattail (Typha latifolia L.) plants - Yavitt, J.B.; Alan K. Knapp (Tellus, 1995)

Nests of Hibana gracilis are reused by Phidippus clarus in wetlands of northeastern Kansas - Johnson, S.R. (The Journal of Arachnology, 1995)

Observing spatial structure in the Flint Hills using AVHRR biweekly composites of maximum NDVI - Henebry, G.M.; Su, H. (1995)

Optimal staining and sample storage time for direct microscopic enumeration of total and active bacteria in soil with two fluorescent dyes - Yu, W.; W. K. Dodds; Banks, M.K.; Skalsky, J.; Strauss, E.A. (Applied and Environmental Microbiology, 1995)
Direct counting techniques, first developed for aquatic samples, can be used to enumerate bacteria in soil and groundwater sediments. Two fluorescent dyes, 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) for actively respiring bacteria and 4(prm1),6-diamidino-2-phenylindole (DAPI) for total bacteria, were tested for their usefulness in epifluorescent direct bacterial enumeration in soil. Both dyes can be used for the same soil sample without affecting enumeration results. Staining for 8 h with CTC and for 40 min with DAPI resulted in maximum numbers of stained cells. The optimal DAPI staining concentration is 10 mg liter(sup-1). After preparation, slides should be stored at 4(deg)C and counted within 2 days for CTC and within 24 h for DAPI. Sodium PP(infi) or sodium chloride solutions were used to desorb bacteria from soil prior to counting. Counts were significantly higher when sodium chloride was used.

Plant productivity and nitrogen gas fluxes in tallgrass prairie - Groffman, P.M.; Turner, C.L. (Landscape Ecology, 1995)
We explored relationships between plant productivity and annual fluxes of nitrogen (N2) and nitrous oxide (N2O) in a tallgrass prairie landscape in central Kansas. Our objective was to develop predictive relationships between these variables that could be used in conjunction with remote sensing information on plant productivity to produce large-area estimates of N gas fluxes. Our hypothesis was that there are inherent relationships between plant productivity and N gas fluxes in tallgrass prairie because both are controlled by water and N availability. The research was carried out as part of a multi-investigator project, the First ISLSCP Field Experiment (FIFE, ISLSCP = International Satellite Land Surface Climatology Program), directed toward the use of remote sensing to characterize land-atmosphere interactions. Fluxes of N2 (denitrification) and N2O were measured using soil core techniques. Estimates of annual flux were produced by temporal extrapolation of measured rates. Annual aboveground net primary productivity (ANPP) was estimated from measurements of the maximum standing crop of plant biomass. There were strong relationships between ANPP and N gas fluxes, and between a satellite remote sensing-based index of plant productivity (normalized difference vegetation index, NDVI) and gas fluxes. We used these relationships to convert images of NDVI into images of N gas fluxes for one 83 ha watershed and for the entire 15 by 15 km FIFE site. These images were used to compute mean landscape gas fluxes (0.62 g N m-2 y-1 for N2, 0.66 g N m-2 y-1 for N2O) and total N gas production for the two areas. Our flux and production values are useful for comparison with values produced by simulation models and site-specific studies, and for assessing the significance of N gas production to ecosystem and landscape scale processes related to nutrient cycling, water quality and atmospheric chemistry.
Keywords: denitrification; NDVI; nitrous oxide; remote sensing

Population ecology of Elliot's short-tail shrew and least shrew in ungrazed tallgrass prairie - Clark, B.K.; D.W. Kaufman; Kaufman, G.A.; Gurtz, S.K. (1995)
Keywords: tallgrass prairie

Population Processes - D.C. Hartnett; Keeler, K.H. (The Changing Prairie, 1995)

Prairie voles impact plants in tallgrass prairie - D.W. Kaufman; Bixler, S.H. (1995)
Keywords: tallgrass prairie

Prairie voles occur at low density in ungrazed tallgrass prairie in eastern Kansas - Bixler, S.H.; D.W. Kaufman (The Prairie Naturalist, 1995)
Keywords: tallgrass prairie

Protozoa-bacteria interactions in subsurface sediments and the subsequent effects on nitrification - Strauss, E.A. (Kansas State University, 1995)

Regional climatic similarities in the temperate zones of North and South America - Paruelo, J.M.; Lauenroth, W.K.; Epstein, H.E.; Burke, I.C.; Aguiar, M.R.; Sala, O.E. (Journal of Biogeography, 1995)
An analysis of the climatic patterns of the temperate zones in North and South America using a global database of monthly precipitation and temperature was performed. Three synthetic variables, identified by a principal component analysis of the monthly data, were used: mean annual precipitation, mean annual temperature and the proportion of the precipitation falling during summer. The spatial gradient of the 3 variables was displayed by constructing a composite colour raster image. A parallelepiped classification algorithm was used to locate areas in both continents that are climatically similar to 5 North American long term ecological research (LTER) sites and to 2 South American LTER sites. The same algorithm was used to identify areas in South America which are climatically similar to some of the major grassland and shrubland types of North America. There was substantial overlap between the climates of North and South America. Most of the climatic patterns found in South America are well represented in North America but there are certain climates in North America that are not found in South America. An example is a climate with relatively low mean annual temperature and high summer precipitation. The climatic signatures of 3 North American LTER sites (Cedar Creek, CPER and Sevilleta) were not found in South America. The climatic signatures of two LTER sites (Konza and Jornada) had some representation in South America. Two South American research sites (Rio Mayo and Las Chilcas) were well represented climatically in North America. The climates of 6 out of 7 selected North American grassland and shrubland types were represented in South America. The northern mixed prairie type was not represented climatically in South America. It is suggested that comparisons of North and South America may provide a powerful test of climatic control over vegetation
Keywords: climate

The relations of phytophagous invertebrates and rangeland plants - Evans, E.W.; Seastedt, T.R. (Wildland Plants: Physiological Ecology and Developmental Morphology, 1995)

The role of fire in Spartina pectinata wetlands dominated tallgrass prairie wetlands - Johnson, S.R.; Alan K. Knapp (Tall Timbers Research Station, 1995)
Keywords: tallgrass prairie

Short-term responses of small mammals to autumn fire in tallgrass prairie - McMillan, B.R.; Brillhart, D.E.; D.W. Kaufman; Kaufman, G.A. (Prairie Naturalist, 1995)
Keywords: tallgrass prairie

Simulation of responses of community structure to species interactions driven by phenotypic change - W. K. Dodds; Henebry, G.M. (Ecological Modelling, 1995)
We developed a community model which considers the effect of phenotype on species interaction in order to elucidate general relationships between phenotype, species interactions and community structure. The model consists of community matrices with density-dependent species interactions and a limit on the total population of each species. A general natural pattern forms the basis of the model: organisms which are most similar compete, those which are less similar may enter into a predator-prey relationship, and those which are most different may be mutualistic. In this model, contrary to some previously published studies, increasing the number of species increased stability of community matrices. The rate of change in phenotype was varied to assess the response of community characteristics. At the highest rate of random phenotypic change there were the most species; the minimum number of species was found at intermediate rates of change. The models were run in the absence of predation, competition, or mutualism. The absence of mutualism led to more extinction. The absence of competition caused communities to quickly reach a population ceiling. Results suggest that it is extremely important to understand the relative occurrence of mutualism and competition in natural communities. Furthermore, the rate of phenotypic change could be an important but subtle determinant of community structure.
Keywords: Competition; interspecific; mutualism; networks; Species interactions

Small-mammal use of experimental patches of tallgrass prairie: influence of topographic position and fire history - Brillhart, D.E.; Kaufman, G.A.; D.W. Kaufman (1995)
Keywords: tallgrass prairie

Soil systems and nutrient cycles of the North American Prairie - Seastedt, T.R. (The Changing Prairie, 1995)

Spatial model error analysis using autocorrelation indices - Henebry, G.M. (Ecological Modelling, 1995)
No standard techniques yet exist for assessing the predictive performance of models that simulate spatially-explicit processes. Spatial simulation models generate autocorrelation patterns that are a critical aspect of model prediction. These patterns can be quantified using spatial (Moran's I) and spatio-temporal (Griffith's STI) autocorrelation indices. A method of error analysis for spatial simulation models is demonstrated using autocorrelation indices to distinguish among the effects of parameter uncertainty on a stochastic spatial simulation of seed dispersal. The resulting autocorrelation patterns of state variables display a range of nonlinear, counterintuitive effects. In contrast to techniques proposed for spatial model error analysis (contagion, spatial predictability, adjacency, multiple resolution procedure, fractal dimension, interface), autocorrelation indices can be used with interval-scaled data and have well-defined sampling distributions that enable significance testing.
Keywords: Autocorrelation; Error analysis; Spatial patterns; Uncertainty analysis

Spider communities in the canopies of annually burned and long-term unburned Spartina pectinata wetlands - Johnson, S.R. (Environmental Entomology, 1995)
Wetlands dominated by Prairie Cordgrass, Spartina pectina (Poaceae), burned annually or at 10- to 20-y intervals were investigated in 1993 and 1994 to quantify the effects of fire on spider community structure and population density. Burned and unburned wetlands had similar spider species; however, annually burned wetlands had both greater species richness and higher spider densities than long-term unburned wetlands. These dynamics parallel differences in insect densities in these wetlands. Previous work has shown that annually burned S. pectinata has much higher annual productivity; thus, the greater number and density of spiders in annually burned wetlands are consistent with these increased energy inputs.

Stomatal and photosynthetic responses to variable light in sorghum, soybeans and eastern gammagrass - Fay, P.A.; Alan K. Knapp (Physiologia Plantarum, 1995)
We studied photosynthetic and stomatal responses of grain sorghum (Sorghum bicolor [L.] Moench cv. Pioneer 8500), soybean (Glycine max L. cv. Flyer) and eastern gamagrass (Tripsacum dactyloides L.) during experimental sun and shade periods simulating summer cloud cover. Leaf gas exchange measurements of field plants showed that short-term (5 min) shading of leaves to 300–400 μmol m−2 s−1 photosynthetic photon flux density reduced photosynthesis, leaf temperature, stomatal conductance, transpiration and water use efficiency and increased intercellular CO2 partial pressure. In all species, photosynthetic recovery was delayed when leaves were reilluminated, apparently by stomatal closure. The strongest stomatal response was in soybean. Photosynthetic recovery was studied further with soybeans grown indoors (maximum photosynthetic photon flux density 1 200 μmol m−2 s−1). Plants grown indoors had responses to shade similar to those of field plants, except for brief nonstomatal limitation immediately after reillumination. These responses indicated the importance of the light environment during leaf development on assimilation responses to variable light, and suggested different limitations on carbon assimilation in different parts of the soybean canopy. Photosynthetic oxygen evolution recovered immediately upon reillumination, indicating that the light reactions did not limit soybean photosynthetic recovery. While shade periods caused stomatal closure and reduced carbon gain and water loss in all species, the consequences for carbon gain/water loss were greatest in soybean. The occurrence of stomatal closure in all three species may arise from their shared phenologies and herbaceous growth forms.
Keywords: A:Ci curves; eastern gamagrass; Glycine max; induction; light; oxygen evolution; photosynthesis; sorghum; Sorghum bicolor; soybean; Stomatal Conductance; Tripsacum dactyloides; Water use efficiency

A study of the aquatic humic substances and hydrogeology in a prairie watershed: use of humic material as a tracer of recharge through soils - Pomes, M.L. (University of Kansas, 1995)

Temporal variation in abundance of Peromyscus leucopus in wooded habitats of eastern Kansas - D.W. Kaufman; Kaufman, G.A.; Finck, E.J. (The American Midland Naturalist, 1995)
White-footed mice (Peromyscus leucopus) were sampled during spring, summer and autumn on the Konza Prairie Research Natural Area, Kansas, from autumn 1981 to spring 1988. Abundance was greater in gallery forest than in wooded outcrop habitat, although temporal patterns of abundance were similar with highs in 1981-1982 and 1985-1986. Standard deviations (SD) of the common logarithm of abundance were ≤ 0.32 for each of four sites in spring, summer and autumn, except for one forest site in spring. Our SD values were similar to those reported for other populations of P. leucopus. Abundance of P. leucopus was related to its abundance in the previous season (spring abundance vs. that in previous autumn, summer abundance vs. that in previous spring and autumn abundance vs. that in previous summer), seed production by woody vegetation and precipitation, but the factors that had a major influence on abundance of P. leucopus varied among spring, summer and autumn populations. Ambient temperature was unrelated to abundance of P. leucopus during each of the 3 seasons studied.

Travel path characteristics for free-living white-footed mice (Peromyscus leucopus) - McMillan, B.R.; D.W. Kaufman (Canadian Journal of Zoology, 1995)
Characteristics of the travel paths of white-footed mice (Peromyscus leucopus) were examined by tracking animals marked with fluorescent pigment in a wooded site in northeastern Kansas. Based on 84 trails made by 49 individuals, it was concluded that tops of structural features (rocks, branches, logs, or rock fence) were selectively used for nighttime travel. Trails averaged 41.7% structural features (SE = 6.0%), whereas sample points 20 cm away from trails averaged 18.0% structural features (SE = 1.8%). This pattern of use of structural features did not differ between male and female mice. Nighttime illumination (according to the moon phase) and season did not affect the proportion of structural features used along travel paths; this suggests that risk from visual predators was not driving the pattern of use of structural features for travel paths by white-footed mice. Rather, white-footed mice may have used surface structure for travel because structural features provide paths that are more easily traveled and remembered. Trees were climbed infrequently (0.6 trees per 100 m of trail), but more in autumn (1.9 trees per 100 m of trail) than in other seasons (0.2 trees per 100 m of trail), which likely resulted from greater availability of seeds, nuts, and fruits during autumn than during other seasons.

Use of simulated herbaceous canopy by foraging rodents - Jekanoski, R.D.; D.W. Kaufman (The American Midland Naturalist, 1995)
Use of seeds from simulated herbaceous canopy by western harvest mice (Reithrodontomys megalotis), deer mice (Peromyscus maniculatus) and white-footed mice (Peromyscus leucopus) was examined in laboratory trials. Each mouse was tested on both simulated full-moon and new-moon nights but with only one of three abundances of surface seeds (high, low or zero abundances of seeds in trays on arena floor). White-footed mice are more total seeds (surface plus canopy seeds) during dark-bright than bright-dark trials and with high than low or zero abundances of surface seeds. However, neither the order of dark and bright conditions nor availability of surface seeds influenced total seeds eaten by deer mice and harvest mice. All three species readily foraged in the canopy in the absence of surface seeds (>90% of trials on both dark and bright nights). When surface seeds were abundant, interspecific differences in canopy foraging were evident as canopy foraging occurred during 54% of trials on both dark and bright nights for harvest mice, 58% and 21% of trials on dark and bright nights, respectively, for white-footed mice and 8% and 0% of trials on dark and bright nights for deer mice.

Using anion exchange membranes to measure soil nitrate availability and net nitrification - Subler, S.; John M. Blair; Edwards, C.A. (Soil Biology & Biochemistry, 1995)
There are few methods that provide adequate integrative measures of soil N availability to plants. We evaluated a new ion-exchange membrane (IEM) technique for measuring soil NO3 availability and nitrification by burying commercially-available anion-exchange membranes (IEMs) in a silt-loam Luvisol (fine, mixed, mesic Typic Fragiudalf) and in the same soil amended with either wheat straw, legume leaves or both materials. Soil was incubated in the laboratory for periods ranging from 1 to 27 days before removing the IEMs and determining membrane-bound NO3 and soil inorganic N concentrations. The soil amendments led to large differences in soil N dynamics and rates of net N mineralization and nitrification among treatments. In all soil treatments, rates of NO3N uptake by IEMs were rapid initially, but slowed after 7 days. On all dates, significantly less NO3N was recovered from IEMs in the amended soils than from those in the control soil, probably because of greater microbial immobilization of NO3 due to the added organic substrates. The IEMs did not act as infinite sinks for NO3, since under strongly N-immobilizing conditions in the wheat straw-amended soil membrane-bound NO3N declined between 3–14 days. Across all soil treatments and sampling dates, membrane-bound NO3N was significantly correlated with soil NO3N concentrations and net soil nitrification (r2 = 0.53 and 0.86, respectively), even when net nitrification was negative. Correlations improved when data from the initial membrane equilibration period (days 1 and 3) were excluded (r2 = 0.85 and 0.96, respectively). The presence of IEMs significantly reduced soil NO3N concentrations in 3 of the 4 soil treatments, and in all of the soil treatments, net soil nitrification and N mineralization were significantly greater in the presence of the IEMs. Results from our correlative study suggest that the IEM technique can be a useful tool for assessing soil nutrient availability and mineralization processes. However, more work is needed to develop this technique before reliable interpretations can be made under a wide variety of field and laboratory conditions.

Wetlands may change tallgrass prairie from a sink to a source for atmospheric methane - Yavitt, J.B.; Alan K. Knapp (1995)
Keywords: tallgrass prairie

Aboveground biomass in tallgrass prairie: effect of time since last fire - J. M. Briggs; Fahnestock, J.T.; Ward, L.; Alan K. Knapp (1994)
Keywords: tallgrass prairie

Atmosphere-biosphere exchange flux of carbon dioxide in a tallgrass prairie modeled with satellite spectral data - Gao, W. (Journal of Geophysical Research, 1994)
The estimation of the rate of net CO2 uptake of vegetated land surfaces is essential for studies of global carbon cycle. The present paper demonstrates the use of spectral reflectance data from satellite remote sensing to model net CO2 flux (NCF) of a tallgrass canopy at the Konza prairie, Kansas. A bidirectional reflectance canopy model was used to estimate seasonal changes in canopy leaf area index (LAI) from surface reflectances remotely sensed by SPOT 1 and Landsat 5 satellites. The radiation model was also coupled with leaf conductance-photosynthesis models to scale up stomatal conductance and NCF from individual leaves to canopy level according to radiation distribution inside the canopy. The satellite-data-driven model was able to closely simulate the seasonal change in LAI as well as the short-term variation of canopy LAI caused by the dry period during late July and early August in the area. Modeled canopy stomatal conductance (gc) and NCF agree with measurements within 0.16 cm s−1 and 0.28 mg m−2 s−1, respectively, during the growth season from late May to late August. In October both measured and modeled NCF turned to small negative values as canopy photosynthesis diminished and predicted LAI approached zero. In addition to data scatter, some of the differences between modeled and measured gc and NCF may be attributed to uncertainties in seasonal changes of plant physiological status that were not detected by satellite data; some of the differences were caused by inadequate description of the dependence of nighttime CO2 flux of soil respiration on near-surface turbulent mixing.
Keywords: tallgrass prairie

Biologically active pools of soil C and N in tallgrass prairie - C. W. Rice; Garcia, F.O. (Defining Soil Quality for a Sustainable Environment, 1994)
Keywords: tallgrass prairie

Characterizing herbivore resistance traits in eight tallgrass prairie grasses - Thomas, M.A. (Kansas State University, 1994)
Keywords: tallgrass prairie

Development and refinement of the Konza Prairie LTER Research Information Management Program - J. M. Briggs; Su, H. (Environmental Information Management and Analysis: Ecosystem to Global Scales, 1994)

Drought-induced nitrogen retranslocation in perennial C4 grasses of tallgrass prairie - Heckathorn, S.A.; DeLucia, E.H. (Ecology, 1994)
We determined if drought—induced nitrogen retranslocation occurs in perrenial grasses of tallgrass prairie, as suggested from studies of annual changes in plant N content. To test this, we analyzed six C4 grasses representing a wide range of drought tolerance for shoot, rhizome, and root N before and after controlled drought. Shoot N concentration decreased in all species during drought (31—41%), including in recently expanded leaves (23—38%). No consistent pattern with respect to drought tolerance was apparent in these decreases or in observed changes in distribution of whole—plant N, although there was some suggestion of a mesic—to—xeric gradient in the magnitude of retranslocation. For example, the proportion of total plant N allocated to shoots decreased during drought 20—29% in the most mesic species over three experiments, 2—12% in the three intermediate species, and 4—6% in the two most xeric species, for pre— vs. post—drought comparisons. However, when drought—stressed plants were compared to well—watered age controls, the respective values were 20—21%, 12—20%, and 0.19%, the apparent result of size—related changes in N allocation in control plants in one experiment. In most cases, shoot N was moved primarily into rhizomes, though in one species with intermediate drought tolerance, evidence suggested that much of the retranslocated shoot N was apparently lost through fine—root turnover. Retranslocation of shoot N to rhizomes and roots, confirmed by monitoring movement of 35S—methionine, was in response to drought stress rather than phenology and involved the entire shoot (e.g., blades, culms, recently expanded leaves). Post—drought photosynthesis and leaf N concentration remained well below predrought levels 6 d following rewatering. Thus decreases in leaf N status during drought as a consequence of retranslocation likely result in lower photosynthetic capacity and decreased whole—plant carbon gain following relief of water stress after rain. Drought—induced retranslocation may serve to protect plant N from loss of herbivory, fire, and volatilization during periods when soil N uptake and carbon assimilation are limited by water availability.
Keywords: tallgrass prairie

Ecology of Spartina pectinata wetlands in northeastern Kansas - Johnson, S.R. (Kansas State University, 1994)

Effect of elevated C02 on stomatal density and distribution in a C4 grass and a C3 forb under field conditions - Alan K. Knapp; Cocke, M.; Hamerlynck, E.P.; Owensby, C.E. (Annals of Botany, 1994)
Two common tallgrass prairie species, Andropogon gerardii, the dominant C4 grass in this North American grassland, and Salvia pitcheri, a C3 forb, were exposed to ambient and elevated (twice ambient) CO2 within open-top chambers throughout the 1993 growing season. After full canopy development, stomatal density on abaxial and adaxial surfaces, guard cell length and specific leaf mass (SLM; mg cm-2) were determined for plants in the chambers as well as in adjacent unchambered plots. Record high rainfall amounts during the 1993 growing season minimized water stress in these plants (leaf xylem pressure potential was usually > -1·5 MPa in A. gerardii) and also minimized differences in water status among treatments. In A. gerardii, stomatal density was significantly higher (190 ± 7 mm-2; mean ± s.e.) in plants grown outside of the chambers compared to plants that developed inside the ambient CO2 chambers (161 ± 5 mm-2). Thus, there was a significant 'chamber effect' on stomatal density. At elevated levels of CO2, stomatal density was even lower (P < 0·05; 121 ± 5 mm-2). Most stomata were on abaxial leaf surfaces in this grass, but the ratio of adaxial to abaxial stomatal density was greater at elevated levels of CO2. In S. pitcheri, stomatal density was also significantly lower when plants were grown in the open-top chambers (235 ± 10 mm-2 outside vs. 140 ± 6 mm-2 in the ambient CO2 chamber). However, stomatal density was greater at elevated CO2 (218 ± 12 mm-2) compared to plants from the ambient CO2 chamber. The ratio of stomata on adaxial vs. abaxial surfaces did not vary significantly in this herb. Guard cell lengths were not significantly affected by growth in the chambers or by elevated CO2 for either species. Growth within the chambers resulted in lower SLM in S. pitcheri, but CO2 concentration had no effect. In A. gerardii, SLM was lower at elevated CO2. These results indicate that stomatal and leaf responses to elevated CO2 are species specific, and reinforce the need to assess chamber effects along with treatment effects (CO2) when using open-top chambers.
Keywords: Andropogon gerardii; elevated CO2; Salvia pitcheri; stomatal density; tallgrass prairie

Effect of sodium on seed choice by deer mice, white-footed mice, and hispid cotton rats - Rustiati, E.L.; D.W. Kaufman (Transactions of the Kansas Academy of Science, 1994)
Effect of sodium content on seed use was tested for deer mice (Peromyscus maniculatus), white-footed mice (P. leucopus), and hispid cotton rats (Sigmodon hispidus) using sodium-enriched pearled barley seeds (Hordeum vulgare). Each trial included the choice of four types of barley seeds [1.6 (control), 4.8, 7.1, and 16.8 mg sodium/g seed]. Seed use by deer mice and white-footed mice differed with sodium concentration but was not affected by locality (eastern versus central Kansas) or gender. In contrast, seed use by cotton rats was not influenced by sodium content and, although seed use differed between males and females (females tested were larger than the males), relative use of seed types was not affected by gender. Average sodium concentration of seeds used did not differ with locality or gender for either deer mice or white-footed mice, or among deer mice (6.6 mg/g), white-footed mice (5.6 mg/g), and cotton rats (6.2 mg/g).

Effects of mycorrhizal and plant density on yield relationships among competing tallgrass prairie grasses - Hetrick, B.A.D.; D.C. Hartnett; G.T. Wilson; D.J. Gibson (Canadian Journal of Botany, 1994)
A replacement series experiment was used to investigate the effects of mycorrhizae, phosphorus availability, and plant density on competitive relationships between three tallgrass prairie species of varying mycorrhizal dependencies. Under mycorrhizal conditions, the obligately mycorrhizal dependent warm-season grass Andropogon gerardii (big bluestem) was a better competitor in mixture with the nonmycorrhiza-dependent cool-season grass Koeleria pyramidata (Junegrass). In the absence of mycorrhizae, however, competitive effects of big bluestem were greatly reduced and Junegrass experienced competitive release. Relative yield totals increased when mycorrhizae were suppressed, suggesting greater intensity of interspecific competition in the presence of mycorrhizae. Thus, the competitive dominance of big bluestem in tallgrass prairie is strongly related to its mycorrhizal status. Elymus canadensis (Canada wild rye) outcompeted big bluestem both with and without mycorrhizae. Relative yield totals of this species mixture were also lower under mycorrhizal conditions, indicating that mycorrhizae increase the intensity of interspecific competition between them. Relative yields of wild rye competing with big bluestem increased in the absence of mycorrhizae, suggesting that it also experiences competitive release when big blue-stem are not mycorrhizal. The outcomes of competition were generally similar among the three total plant density treatments and between P-fertilized and nonfertilized treatments. However, interactions between mycorrhizal effects and plant density confirm that outcomes of interspecific competitive interactions may be density dependent in some cases.
Keywords: Andropogon gerardii; arbuscular mycorrhizae; de Wit replacement series; Elymus canadensis; Koeleria pyramidata

Effects of subterranean herbivores on vegetation - Huntly, N.; Reichman, O.J. (Journal of Mammalogy, 1994)
Fossorial herbivores are common in Eurasia, North and South America, and Africa, particularly in arid and semiarid regions. There is ample evidence, although often indirect and semiquantitative, that they have local and broad-scale effects on vegetation. These effects arise from feeding, harvesting, and caching, local soil disturbances, and longer-term changes in soil structure and topography, many aspects of which are similar among the diversity of fossorial herbivores. Often, the net effect of these animals' activities is alteration of composition of plant species and increased plant diversity. Standing crop of plants often is reduced, and long- and short-term changes in productivity can occur. Better understanding of the rules that govern diet selection and burrow size, dynamics, and geometry are needed to predict effects of these animals under specific environmental conditions.
Keywords: burrows; diet; fossorial mammals

Effects of topography and fire on spatial and temporal distribution of soil moisture in a tallgrass prairie - Su, H.; Alan K. Knapp; J. M. Briggs (Time Domain Reflectometry in Environmental, Infrastructure and Mining Applications, 1994)
Keywords: tallgrass prairie

Effects of urine deposition on small-scale patch structure and vegetative patterns in prairie vegetation - Steinaurer, E.M. (University of Oklahoma, 1994)

Elevated CO2 alters dynamic stomatal responses to sunlight in a C4 grass - Alan K. Knapp; Fahnestock, J.T.; Owensby, C.E. (Plant Cell and Environment, 1994)
Native tallgrass prairie in NE Kansas was exposed to elevated (twice ambient) or ambient atmospheric CO2 levels in open-top chambers. Within chambers or in adjacent unchambered plots, the dominant C4 grass, Andropogon gerardii, was subjected to fluctuations in sunlight similar to that produced by clouds or within canopy shading (full sun > 1500 μmol m−2 s−1 versus 350 μmol m−2 s−1 shade) and responses in gas exchange were measured. These field experiments demonstrated that stomatal conductance in A. gerardii achieved new steady state levels more rapidly after abrupt changes in sunlight at elevated CO2 when compared to plants at ambient CO2. This was due primarily to the 50% reduction in stomatal conductance at elevated CO2, but was also a result of more rapid stomatal responses. Time constants describing stomatal responses were significantly reduced (29–33%) at elevated CO2. As a result, water loss was decreased by as much as 57% (6.5% due to more rapid stomatal responses). Concurrent increases in leaf xylem pressure potential during periods of sunlight variability provided additional evidence that more rapid stomatal responses at elevated CO2 enhanced plant water status. CO2-induced alterations in the kinetics of stomatal responses to variable sunlight will likely enhance direct effects of elevated CO2 on plant water relations in all ecosystems.

Expansion of gallery forest on Konza Prairie Research Natural Area, Kansas - Knight, C.L.; J. M. Briggs; Nellis, M.D. (Landscape Ecology, 1994)
To determine the dynamics of the spatial extent of gallery forest on Konza Prairie Research Natural Area (KPRNA), aerial photographs taken over a 46 year time frame were digitized into an ARC-INFO Geographic Information System (GIS). A Global Positioning System (GPS) was used to collect ground control points to co-register the photographs for each year. Gallery forest areas for the three major drainage boundaries (Kings Creek, Shane Creek, and White Pasture) were analyzed to assess the uniformity of change in the landscape system. Results indicated that the total gallery forest area on KPRNA has increased in area from 157 ha in 1939 to over 241 ha in 1985. During this time, there was an increase in the total number of patches and a decrease in the mean size of forest patches. However, the rate of increase was not consistent over this time period, nor was it uniform from one drainage basin or stream order to another. Detailed spatial analysis of the forested area with a geomorphology and digital elevation model of Konza Prairie showed that in 1985, 58% of the forest was on alluvial/colluvial soil, yet only 15% of that soil type was forested. In addition, over 70% of the forest was on the 0–15% slope interval, but only 15–20% of that slope interval was forested. These results may be attributed to a variety of factors such as changing management practices (i.e., frequency of fires and herbicide spraying) and the temporal constraints on extent to which the gallery forest can expand across the landscape.
Keywords: burning; gallery forest; GIS; historical landuse; tallgrass prairie

Experimental manipulation of natural plant communities - Gurevitch, J.; Scott. L. Collins (Trends in Ecology and Evolution, 1994)
Attempts to elucidate the factors controlling the structure of plant communities have relied increasingly on field experiments. This is a powerful approach for testing theoretical predictions that offers important advantages over observational and comparative studies. However, field experiments suffer from intrinsic difficulties as well as more-easily remediable limitations. Recent progress has been made by new approaches including the use of multifactor experiments, and the development and dissemination of better statistical tools.

Impact of El Nino on Konza Prairie Research Natural Area - J. M. Briggs (El Nino & Long-Term Ecological Research (LTER) Sites, 1994)

Importance of photosynthetic pathways, management, and climate on plant production and soil carbon of semihumid temperate grasslands - Seastedt, T.R.; Coxwell, C.C.; Ojima, D.S.; Parton, W.J. (Ecological Applications, 1994)
A modeling study evaluated the importance of photosynthetic pathways (C3, C4, or both) and management strategies to the foliage productivity and soil carbon characteristics of a semihumid temperate grassland subjected to various combinations of climate change. Model values for plant and soil characteristics were obtained at sites near Manhattan, Kansas, and the Manhattan climate record provided the nominal climatic drivers. Model runs used both actual monthly temperature and precipitation data for a 100—yr interval and average weather conditions generated from this record. Monthly temperatures were increased 2°C, left unchanged, or decreased 2°C; annual precipitation was increased 6 cm, left unchanged, or decreased 6 cm. All possible combinations of temperature and precipitation were then used in 100—yr simulations. Regardless of the specific climate scenario, plant production was lowest for C3 grasses and highest for the mixed C3—C4 community. The nominal seasonal pattern of precipitation favored an active C3 plant community in early to late spring, prior to the emergence of the C4 vegetation. However, the higher growth and water use efficiencies of C4 vegetation during summer contributed to the maximization response of the grasslands containing both C3 and C4 grasses. An analysis of variance of annual average values observed from 100—yr simulations was used to evaluate the relative importance of climate, photosynthetic pathways, and management activities (annually burned, burned every 4 yr, unburned, or lightly grazed) to plant production and soil carbon values. Photosynthetic pathway and precipitation were identified as the most significant single variables affecting foliage production; the interaction between photosynthetic and temperature was the most significant interaction term. Management treatments were by far the most important variables affecting soil carbon values, but 2°C warming did produce substantial soil carbon losses from C3 grasslands. Enhanced carbon fixation by the C4 and C3—C4 plant communities negated the losses of soil carbon caused by enhanced soil respiration at warmer temperatures.

Leaf-level responses to light and temperature in two co-occurring Quercus (Fagaceae ) species: implications for tree distribution patterns - Hamerlynck, E.P.; Alan K. Knapp (Forest Ecology and Management, 1994)
Leaf-level responses to light environment (sun vs. shade) and high temperature were compared in two gallery forest oaks, bur oak (Quercus macrocarpa) and chinquapin oak (Quercus muehlenbergii). Our goal was to determine if species-specific differences in response to light or temperature could explain the distribution of these oaks in tallgrass prairie gallery forests. On the Konza Prairie Research Natural Area in NE Kansas (USA), bur oak is more abundant than chinquapin oak along lower reaches of streams where the forests are most productive and canopy closure is greatest. We hypothesized that bur oak is better able to acclimate physiologically to reduced light availability than chinquapin oak. Leaf level acclimation to low light in both oaks occurred through reduced photosynthetic light compensation points (PLC) (bur oak, 60.77 ± 3.02 μmol photons m−2 s−1 in sun leaves vs. 29.25 ± 0.29 photons m−2 s−1 in shade leaves; chinquapin oak, 49.47 ± 2.82 photons m−2 s−1 in sun leaves vs. 26.48 ± 1.74 photons m−2s−1 in shade leaves), resulting from nearly 50% reductions in dark respiration and specific leaf mass in both species. Apparent quantum requirement (Qreq; mol photons mol−1 O2) did not differ between sun and shade leaves in either species, and only bur oak showed differences in sun and shade leaf shape. We also hypothesized that chinquapin oak, which is more abundant in exposed, upper stream reaches, has greater photosynthetic tolerance to the high temperatures characteristics of this region. The maximum temperature tolerances (Tmax) of these oaks were compared by measuring increases in chlorophyll fluorescence. For most of the growing season, Tmax in chinquapin oak was 2.0°C higher than in bur oak. Field measurements of leaf vs. air temperatures in seedlings and adult trees indicated that Tmax was more likely to be exceeded in bur than in chinquapin oak, particularly in seedlings exposed to high solar radiation loads. We concluded that differences in thermal tolerance, in addition to previously documented differences in water relations are important determinants of distributional patterns of these oaks within gallery forests.
Keywords: gallery forest; Light acclimation; photosynthesis; Quercus; tallgrass prairie; Temperature tolerance

Long and short-term effects of fire on nitrogen cycling in tallgrass prairie - Ojima, D.S.; Schimel, D.S.; Parton, W.J.; Owensby, C.E. (Biogeochemistry, 1994)
Fires in the tallgrass prairie are frequent and significantly alter nutrient cycling processes. We evaluated the short-term changes in plant production and microbial activity due to fire and the long-term consequences of annual burning on soil organic matter (SOM), plant production, and nutrient cycling using a combination of field, laboratory, and modeling studies. In the short-term, fire in the tallgrass prairie enhances microbial activity, increases both above-and belowground plant production, and increases nitrogen use efficiency (NUE). However, repeated annual burning results in greater inputs of lower quality plant residues causing a significant reduction in soil organic N, lower microbial biomass, lower N availability, and higher C:N ratios in SOM. Changes in amount and quality of below-ground inputs increased N immobilization and resulted in no net increases in N availability with burning. This response occurred rapidly (e.g., within two years) and persisted during 50 years of annual burning. Plant production at a long-term burned site was not adversely affected due to shifts in plant NUE and carbon allocation. Modeling results indicate that the tallgrass ecosystem responds to the combined changes in plant resource allocation and NUE. No single factor dominates the impact of fire on tallgrass plant production.
Keywords: carbon; fire; immobilization; Mineralization; Nitrogen use efficiency; soil organic matter; tallgrass prairie

Mathematical simulation of C4 grass photosynthesis in ambient and elevated C02 - Chen, D.X.; Coughenour, M.B.; Alan K. Knapp; Owensby, C.E. (Ecological Modelling, 1994)
A mechanistic leaf photosynthesis model was developed for C4 grasses based on a general simplified scheme of C4 plant carbon metabolism. In the model, the PEPcase-dependent C4-cycle was described in terms of CO2 concentration in the mesophyll space using Michaelis-Menten kinetics, and the activity of PEPcase was related to the incident PAR to take account of the influence of light on the activity of C4-cycle processes. The CO2 refixation by Rubisco in the bundle sheath was described using a widely accepted C3 photosynthesis model. The model assumes a steady state balance among CO2 diffusion from surrounding atmosphere into the mesophyll space, CO2 transport into the bundle sheath by the C4-cycle, CO2 refixation by the C3-cycle in the bundle sheath, and CO2 leakage from the bundle sheath. The response to temperature of photosynthesis was incorporated via the temperature dependence of model parameters. The photosynthesis model was coupled with a stomatal conductance model in order to predict leaf photosynthesis rates at different atmospheric conditions. The empirical model of Ball et al. (1987) was adopted and slightly modified to describe responses in stomatal conductance. The coupled model was parameterized for the C4 grass Andropogon gerardii grown in both ambient (350 ppm) and elevated (700 ppm) CO2 atmospheres. The key parameters of the model were estimated by fitting the model to the measured data using non-linear regression. The model was validated by comparison the predicted photosynthetic response to PAR in both CO2-pretreatments with the measured data from an independent gas exchange experiment. The predicted photosynthesis and stomatal conductance matched the measured data quite well for both atmospheric CO2-pretreatments. At 25°C, the estimated maximum carboxylation rate of Rubisco Vcm,25, potential electron transport rate Jm,25 and quantum efficiency α were increased by CO2 enrichment. The maximum PEPcase activity Vpm,25 was lower in elevated CO2. The model predicted that the light-saturated leaf photosynthesis will increase by about 10% with the rising of atmospheric CO2 from 350 to 700 ppm at 30°C, and that the optimal temperature of photosynthesis will shift from 37 to 38.5°C. The estimated slope of the stomatal conductance model was increased by atmospheric CO2 enrichment. Stomatal conductance was significantly reduced by increasing atmospheric CO2 concentration.
Keywords: Andropogon gerardii; C4 grass; CO2 enrichment; photosynthesis; Stomatal Conductance

Microbial biomass dynamics in tallgrass prairie - Garcia, F.O.; C. W. Rice (Soil Science Society of America Journal, 1994)
The temporal dynamics and effects of burning, mowing, and N fertilization on microbial biomass (MBM) in tallgrass prairie were studied in a field experiment established in 1986. Microbial C (MC) and microbial N (MN), determined by the fumigation-incubation procedure during the growing seasons of 1989 through 1991, averaged 217 mg C kg−1 and 32.6 mg N kg−1, respectively, for the 0- to 30-cm depth. Accumulation of litter and greater production of roots near the surface resulted in stratification of MBM. Seasonally, MBM was higher in early spring, decreased with the initiation of plant growth, and then recovered by late summer or early fall. Decreases of MN between March and July coincided with plant N uptake. The increase of MC and decrease of MN during the 3 yr of the study were related to increased plant production. Burning had a short-term and variable effect on MC. Burning tended to reduce MC during dry years and increase it in normal to wet years. Mowing and raking decreased MC and MN, probably because of reduced root biomass and removal of standing vegetation. Nitrogen addition resulted in higher MN and tended to reduce MC, possibly by modifying the composition of the microbial population. Microbial biomass seems to play a critical role in conserving N in the tallgrass prairie ecosystem.
Keywords: tallgrass prairie

Microhabitat and space use by Peromyscus leucopus : influence of vertical and horizontal structure - McMillan, B.R. (Kansas State University, 1994)

Mycorrhizal activity in warm-and cool-season grasses: variation in nutrient uptake strategies - Hetrick, B.A.D.; G.T. Wilson; Schwab, A.P. (Canadian Journal of Botany, 1994)
Because cool-season grasses display little or no mycorrhizal responsiveness in prairie soil, it is unclear whether the high levels of mycorrhizal activity observed previously in these grasses represent nutrient uptake by external hyphae or simply metabolism of stored fungal reserves in roots. To distinguish between these hypotheses, a warm-season grass, Andropogon gerardii, or a cool-season grass, Bromus inermis, were grown at two temperatures on one side of a pot divided by a 43-μm nylon root barrier. Mycorrhizal function was assessed by measuring the amount of 32P translocated from one side of the pot to plants on the other side. As a control, mycorrhizal hyphae crossing the barrier were severed manually. Approximately 100 times more 32P was observed in mycorrhizal B. inermis grown at 18 °C versus 29 °C, and in B. inermis with intact versus severed hyphae at the cooler temperature. In contrast, A. gerardii accumulated approximately 4 times more 32P at 29 °C than at 18 °C, and approximately 100 times more with intact versus severed hyphae at the warmer temperature. Thus, it appears that mycorrhizal hyphae are highly active in both plant species regardless of the host's mycorrhizal responsiveness. Furthermore, mycorrhizal activity is highest at the temperature that favors growth of each species. The considerable activity of mycorrhizae in B. inermis is enigmatic since it usually has no biomass response. To further clarify the relationship between nutrient uptake and biomass response, both plant species were fertilized with a range of P levels and grown at a neutral temperature that supported the growth of both species. Although the concentration of P in B. inermis plant tissue increased in response to fertilization, there was no corresponding increase in biomass. In contrast, for A. gerardii, there was a direct and positive relationship between P fertilization and biomass produced, but tissue P concentrations remained relatively stable. Mycorrhizal symbiosis had no overall effect on biomass of B. inermis but significantly improved the growth of A. gerardii. These experiments showed clear differences in the growth strategies used by these two plant species. It is unclear whether these are differences that can be attributed to warm- and cool-season grasses in general. Short-term biomass responses as a measure of a plant's reliance on the symbiosis may not entirely reflect the contribution of the symbiosis if plants store nutrients with subsequent and perhaps delayed effects on fecundity, offspring performance, or even biomass. However, if the stored nutrient merely represents luxury consumption, this could still affect competitive ability because luxury consumption preempts the availability of nutrients for competitors.
Keywords: big bluestem; mycorrhizal dependence; mycorrhizal responsiveness; smooth bromegrass

Mycorrhizal dependence of Andropogon gerardii and Schizachyrium scoparium in two prairie soils - Anderson, R.C.; Hetrick, B.A.D.; G.T. Wilson (American Midland Naturalist, 1994)
Previous research in tallgrass prairie in Kansas indicated that warm-season, C4, grasses are obligate mycotrophs and do not grow normally in the absence of mycorrhizal symbiosis. However, the degree to which such grasses depend on mycorrhizae in other prairie soils has not been examined. Growth and mycorrhizal colonization of roots of Andropogon gerardii and Schizachyrium scoparium were compared in soil collected from Konza Prairie Research Natural Area (KPRNA), Riley County, Kansas and from Sand Ridge State Forest (SRSF), Mason County, Illinois. Plants of both species were grown in the two soils and were inoculated with Glomus etunicatum spores originally collected from KPRNA or colonized root pieces from S. scoparium plants collected from SRSF. Glomus etunicatum inoculum resulted in significantly greater root colonization and biomass of both plant species in steamed KPRNA soil than did root piece inoculum. There was no benefit from inoculation in non-sterile soil which contained indigenous mycorrhizal fungi. In SRSF soil, there was no response to inoculation with mycorrhizal fungi from either source. The lack of mycorrhizal response in SRSF soil is attributed to the greater plant-available P level of this soil. For S. scoparium grown in SRSF soil, plants grown in steamed soil produced more biomass than plants grown in steamed soil amended with nonsterile soil sievings (containing soil organisms other than mycorrhizal fungi), or in nonsterile soil. These differences could be due to competition for inorganic nutrients between soil microbes and the plant or antagonistic relationships between the plant or the mycorrhizal association and the soil microbes. Thus, the mycorrhizal dependence of these plant species is related to both soil and inoculum type or species.

Odor as a factor in nut discovery by fox squirrels - Luft, J.; Malinowski, J.; J. M. Briggs; Smith, C.C. (Transactions of the Kansas Academy of Science, 1994)
Walnuts and bur oak acorns were buried in alternate positions in a 10-×-10 grid in a riparian forest with 10-m spacing between nuts. Bur oak acorns soaked in walnut extract and walnuts were buried in a second grid of similar spacing. Fox squirrels removed walnuts fastest and at the same rate in both grids, whereas acorns soaked in walnut extract were removed faster than unsoaked acorns but slower than walnuts. In the light of earlier studies, these observations are interpreted as showing that squirrels can smell buried walnuts from a greater distance than buried acorns.

Plant demographic responses to mycorrhizal symbiosis in tallgrass prairie - D.C. Hartnett; Samenus, R.H.; Fischer, L.E.; Hetrick, B.A.D. (Oecologia, 1994)
The effects of mycorrhizal symbiosis on seedling emergence, flowering and densities of several grasses and forbs were assessed in native tallgrass prairie and in sown garden populations at the Konza Prairie in northeastern Kansas. Mycorrhizal activity was experimentally suppressed with the fungicide benomyl. Flowering and stem densities of the cool-season grass, Dichanthelium oligosanthes, sedges (Carex spp.), and the forb Aster ericoides were higher in non-mycorrhizal (benomyl-treated) than in mycorrhizal plots and the magnitude of these differences was significantly affected by burning. Mycorrhizae significantly enhanced flowering of the warmseason grasses Andropogon gerardii and Sorghastrum nutans in burned prairie, but not in unburned sites. These patterns suggest that mycorrhizal effects on the dynamics of cool-season graminoid and forb populations are likely to be mediated indirectly through effects of the symbiosis on the competitive dominance of their neighbors. Seedling emergence rates of the cool-season C3 grasses Elymus canadensis and Koeleria cristata were significantly reduced in the benomyl-treated plots, whereas benomyl treatment had no significant effect on seedling emergence of the warm-season C4 grasses A. gerardii and Panicum virgatum. The forbs showed variable responses. Seedling emergence of Liatris aspera was greater under mycorrhizal conditions, but that of Dalea purpurea was unaffected by mycorrhizal treatment. These results show that effects of mycorrhizal symbiosis on the population dynamics of co-occurring prairie plants vary significantly both among species and among different life history stages within species. The results also indicate that mycorrhizas and fire interact to influence competitive interactions and demographic patterns of tallgrass prairie plant populations.
Keywords: fire; tallgrass prairie; VA mycorrhizas Plant demography

Plant production and the biomass of soil microorganisms in late-successional ecosystems: A continental-scale study - Zak, D.R.; Tilman, D.; Parameter, R.R.; Fisher, F.M.; C. W. Rice; Vose, J.; Milchunas, D.; Martin, C.W. (Ecology, 1994)
Annual C inputs from plant production in terrestrial ecosystems only meet the maintenance energy requirements of soil microorganisms, allowing for little or no net annual increase in their biomass. Because microbial growth within soil is limited by C availability, we reasoned that plant production should, in part, control the biomass of soil microorganisms. We also reasoned that soil texture should further modify the influence of plant production on soil C availability because fine-textured soils typically support more microbial biomass than coarse-textured soils. To test these ideas, we quantified the relationship between aboveground net primary production (ANPP) and soil microbial biomass in late-successional ecosystems distributed along a continent-wide gradient in North America. We also measured labile pools of C and N within the soil because they represent potential substrate for microbial activity. Ecosystems ranged from a Douglas-fir forest in the western United States to the grasslands of the mid-continent to the hardwood forest in the eastern U.S. Estimates of ANPP obtained from the literature ranged from 82 to 1460 g@?m^-^2@?yr^-^1. Microbial biomass C and N were estimated by the fumigation-incubation technique. Labile soil pools of C and N and first-order rate constants for microbial respiration and net N mineralization were estimated using a long-term (32 wk) laboratory incubation. Regression analyses were used to relate ANPP and soil texture with microbial biomass and labile soil C and N pools. Microbial biomass carbon ranged from 2 g/m^2 in the desert grassland to 134 g/m^2 in the tallgrass prairie; microbial N displayed a similar trend among ecosystems. Labile C pools, derived from a first-order rate equation, ranged from 115 g/m^2 in the desert grassland to 491 g/m^2 in the southern hardwood forest. First-order rate constants for microbial respiration (k) fell within a narrow range of values (0.180 to 0.357 wk^-^1), suggesting that labile C pools were chemically similar among this diverse set of ecosystems. Potential net N mineralization rates over the 32-wk incubation were linear in most ecosystems with first-order responses only in the alpine tundra, tallgrass prairie, and forests. Microbial biomass C displayed a positive, linear relationship with ANPP (r^2 = 0.51), but was not significantly related to soil texture. Labile C also was linearly related to ANPP (r^2 = 0.32) and to soil texture (r^2 = 0.33). Results indicate that microbial biomass and labile organic matter pools change predictably across broad gradients of ANPP, supporting the idea that microbial growth in soil is constrained by C availability.

Prevalence of hantavirus antibodies in natural populations of deer mice in north central Kansas - Kaufman, G.A.; D.W. Kaufman; McMillan, B.R.; Brillhart, D.E. (Prairie Naturalist, 1994)

Response of roundleaf monkeyflower to flooding in small streams in northeastern Kansas - Johnson, S.R. (Prairie Naturalist, 1994)

Responses of forbs and grasses to selective grazing by bison: interactions between herbivory and water stress - Fahnestock, J.T.; Alan K. Knapp (Vegetatio, 1994)
Two abundant tallgrass prairie forb species, Ambrosia psilostachya and Vernonia baldwinii, are commonly found intact in patches where the grasses have been selectively grazed by bison. Microclimatic patterns and physiological responses of these forbs were measured in grazed and ungrazed patches. These experiments demonstrated that bison herbivory indirectly enhanced water availability and productivity of forbs growing in grazed patches. This was due primarily to the reduction in transpiring grass leaf area in grazed patches and an increase in light availability. In grazed patches, incident light at forb mid-canopy height was 53% greater than ungrazed sites at midseason and soil temperatures were always warmer (e.g., 10 ?C at 5 cm), perhaps enabling forbs to initiate growth earlier in the spring. Enhanced leaf xylem pressure potential and stomatal conductance in plants in grazed areas were most evident when water availability was low (i.e., late in the growing season and over short-term dry periods characteristic of the tallgrass prairie environment). Relative to individuals in ungrazed areas, end-of-season biomass of A. psilostachya was 40% greater and reproductive biomass and head number of V. baldwinii was 45% and 40% greater, respectively, in plants in grazed patches. A favorable growing environment maintained in grazed patches during periods of water limitation enhances carbon gain in forbs leading to increased biomass and potential fitness.
Keywords: bison; Light reduction; Selective herbivory; tallgrass prairie; water stress

Seed dispersal by adhesion: influence of dispersal agent, diaspore morphology, habitat, height of attachment, and nutrient content on the dissemination of diaspores - Lyons, S.A. (Kansas State University, 1994)

Small mammals in northeastern Kansas: differences in use of interspersed woodland and grassland - McMillan, B.R.; D.W. Kaufman (The Prairie Naturalist, 1994)

Source(s), fate and residence time of nitrate at two sites in Kansas--a comparison of carbonate and alluvial aquifers, Kansas Water Resources Research Institute Report, Contribution No. 312 - G. L. Macpherson; Schulmeister, M.K. (1994)

Space shuttle photography for monitoring global change - Nellis, M.D.; Lulla, K.; J. M. Briggs (1994)

Stomatal responses to variable sunlight in Bur Oak (Quercus macrocarpa Michx.) leaves with different photosynthetic capacities - Hamerlynck, E.P.; Alan K. Knapp (International Journal of Plant Science, 1994)
Interspecific comparisons of stomatal response to variable light have generally supported the hypothesis that stomatal adjustments are more rapid in plants with high photosynthetic capacity. We compared stomatal responses to variable light in bur oak (Quercus macrocarpa) leaves that had low photosynthetic capacity and high apparent anthocyanins levels ("red leaves") with responses in green leaves. When incident sunlight was experimentally varied, stomatal conductance (gs) in red leaves was no less responsive than in green leaves. In both leaf types, gs declined at the same rate ($18.9\ {\rm mmol}\ {\rm m}^{-2}\ {\rm s}^{-1}\ {\rm min}^{-1}$) upon shading and increased at the same rate ($13.4\ {\rm mmol}\ {\rm m}^{-2}\ {\rm s}^{-1}\ {\rm min}^{-1}$) when reilluminated. The only difference in stomatal response in red leaves was an overall reduction in gs compared with green leaves. In shade, net photosynthetic rates (${\rm A}_{\text{net}}$) in red leaves were very low (${\rm ca}.\ 2.3\ μ {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$) but still nearly 70% of full sun rates ($3.2\ μ {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$). In contrast, ${\rm A}_{\text{net}}$ in green leaves reduced by nearly 50% in shade ($7.2\ μ {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$) relative to full sun rates ($14.1\ μ {\rm mol}\ {\rm m}^{-2}\ {\rm s}^{-1}$). Internal CO2 concentrations ( C i) were always ${\rm ca}.\ 50\ μ {\rm L}\ {\rm L}^{-1}$ higher in red than in green leaves. Upon reillumination, ${\rm A}_{\text{net}}$ in red leaves immediately returned to preshade levels, while green leaves recovered more slowly, perhaps because of stomatal limitation, as indicated by reduced C i. We concluded that, although rapid stomatal responses are often correlated with photosynthetic capacity among species, within Quercus macrocarpa, stomatal responses to rapidly varying light are not related to leaf photosynthetic capacity.

Temporal variation in coyote prey in tallgrass prairie of eastern Kansas - Brillhart, D.E.; D.W. Kaufman (The Prairie Naturalist, 1994)
Keywords: tallgrass prairie

Using remote sensing to determine heterogeneity in tallgrass prairie - J. M. Briggs; Scott. L. Collins (1994)
Keywords: tallgrass prairie

Water relations and biomass responses to irrigation across a topographic gradient in tallgrass prairie - Alan K. Knapp; Koelliker, J.K.; Fahnestock, J.T.; J. M. Briggs (1994)
Keywords: Water relations

Wind induced leaf binding by prairie cordgrass onto common milkweed in northeastern Kansas - Johnson, S.R. (Prairie Naturalist, 1994)
In this study, I investigated an interaction between prairie cordgrass (Spartina pectinata) and common milkweed (Asclepias syriaca) where leaves of cordgrass became tightly bound to milkweed stems, primarily at upper nodes. Milkweed plants involved in this interaction typically had damaged leaves and increased fruit production compared to unbound milkweed plants. Cordgrass leaves apparently, by the action of wind, become wrapped around structures that are stiff and rough surfaced. No binding interactions took place between cordgrass and wooden dowels set in wetlands and designed to imitate the growth form of common milkweed. Likewise, no interactions occurred between cordgrass and hemp dogbane, a plant of similar growth form to milkweed but with smooth stems.
Keywords: Wind

Area-restricted search by plains pocket gopher (Geomys bursarius) in tallgrass prairie habitat - Benedix, J.H. (Behavioral Ecology, 1993)
Because pocket gophers have the high energetic cost of excavating burrows and an inability to detect distant food items through the soil, I hypothesized that individuals within established burrow systems would use area-restricted search as a foraging strategy. To examine this hypothesis I compared gopher foraging effort over a 10-month period between areas in which overall plant densities were experimentally varied. Gophers expended approximately 50% of their foraging effort in areas with the highest plant density, even though these made up only 33% of the available area in experimental plots. In large, gridded areas sampled for an entire season as well as in small areas in which gophers foraged for less than 1 week, gopher foraging effort was related to the density of a single leguminous plant species, Psoralea argophylla. In small plots where this plant species was at high density, gophers created more tunnel branches, thereby intensifying their search effort. Thus, area-restricted search appears to increase the rate of encounter with the patchily distributed Psoralea plants.
Keywords: area restricted search; foraging; Geomys bursarius; pocket gopher; Psorela

Biomass production in a tallgrass prairie ecosystem exposed to ambient and elevated CO2 - Owensby, C.E.; Coyne, P.I.; Ham, J.M.; Auen, L.M.; Alan K. Knapp (Ecological Applications, 1993)
Keywords: Aboveground biomass; Andropogon gerardii; Carbon dioxide; elevated CO2; kansas; Poa pratensis; Root biomass; tallgrass prairie; water-use efficiency; xylem pressure potential

The Birds of Konza: Avian Ecology of the Tallgrass Prairie - Zimmerman, J.L. (University Press of Kansas, 1993)

Bison selectivity and grazing response of little bluestem and big bluestem in burned and unburned tallgrass prairie - Pfeiffer, K.E. (Kansas State University, 1993)
Keywords: tallgrass prairie

Changes in microbial populations from eastern woodrat caches - Post, D.M.; Urban, J.E. (Southwestern Naturalist, 1993)
Change in microbial populations on three plant foods commonly stored over winter by eastern woodrats (Neotoma floridana) was assessed. It was expected that dogwood fruits (Cornus drummondii) would be affected by microbes to a greater degree than ash seed (Fraxinus pennsylvanica) or redbud seed (Cercis canadensis). Results revealed a change in microbial populations over time but dogwood fruit was no more liable to microbial infestation than seeds. One bacterial species was found in high number on all three food types while three species were found on only two of the three foods. Microbial populations from all three test items increased from November to January but March populations were not different from November populations. It is suggested that climatic factors help to control microbial populations on cache foods.

Characteristics and significance of the caches of eastern woodrats (Neotoma floridana ) - Post, D.M.; Reichman, O.J.; Wooster, D. (Journal of Mammalogy, 1993)
Caches from eastern woodrat (Neotoma floridana) dens were analyzed for plant-species composition, abundance, and energy content. Body mass and sex of den residents and the den volume were measured to determine correlations with energy content of caches. We found no difference between males and females in den volume or energy content of caches. However, a positive correlation existed between body mass of the cache owner and the amount of energy stored in the cache, such that larger individuals had a disproportionately greater reserve of energy stored in caches than did smaller individuals. The disparity suggests that small individuals are forced to forage outside the den more often than large individuals.
Keywords: caching; dens; eastern woodrats; energy; food storage; Neotoma floridana

Comparative water relations of seedling and adult Quercus species during gallery forest expansion in tallgrass prairie - Bragg, W.K.; Alan K. Knapp; J. M. Briggs (Forest Ecology and Management, 1993)
Seasonal patterns in xylem pressure potential (ψ) and stomatal conductance to water vapor (g) were compared between seedlings (1–5 years old) invading tallgrass prairie and adult trees of Quercus macrocarpa (Bur oak) and Quercus muehlenbergii (Chinquapin oak) in adjacent gallery forest. Water is often limiting to productivity in the Flint Hills of NE Kansas, thus, we hypothesized that seedlings invading a grassland would have lower ψ and g compared with adult trees, reflecting competitive interactions for water between seedlings and the dominant grasses. We found that ψ was usually lower in adult trees than in older seedlings, but in the very smallest seedlings ψ was significantly reduced compared with mature (greater than 50 years) individuals. Adult and 1- to 2-year-old seedlings had similar g during the season with highest g occurring in older (4- to 5-year-old) seedlings. In general, Q. muehlenbergii had higher ψ and lower g than Q. macrocarpa consistent with reports that Q. muehlenbergii is more drought tolerant. Rapid and extensive root growth characteristic of Quercus seedlings reduced the period of time when seedlings invading prairie must compete with the grasses for water, although water stress may still be an important factor affecting first-year seedlings in this ecosystem. In contrast, strong intraspecific competition for water within mature gallery forests may have reduced ψ and g in forest trees. Thus, the potential for water stress to impact Quercus survival and growth in this drought-prone ecosystem is greatest during establishment and then after forest development is complete. Older seedlings (greater than 4–5 years old), saplings and isolated trees within the prairie may experience the least water stress due to a reduction in both inter- and intraspecific competition for water. These data suggest that in the absence of severe fire or drought occurring during the growing season, gallery forests will continye to expand into tallgrass prairie.
Keywords: Water relations

Consequences of non-equilibrium resource availability across multiple time scales: the transient maxima hypothesis - Seastedt, T.R.; Alan K. Knapp (American Naturalist, 1993)
Nonequilibrium biotic responses to changes in resource limitation dominate the behavior of tallgrass prairie ecosystems. Rates of leaf photosynthesis on a time scale of minutes, amounts of annual plant productivity, patterns in the productivity of certain consumer groups, and amounts of soil organic matter accumulation over millennia all reflect biotic responses to frequent and recurring shifts in limiting resources. Productivity is higher during a transition period when the relative importance of an essential resource is changing than during an equilibrium interval generated by single resource limitation. These "transient maxima" are both characteristic and easily measurable in the tallgrass prairie because of the unpredictable climate and ecological constraints such as grazing and recurrent fires that modify water, nitrogen, and light availability. Such diverse phenomena as overcompensation for herbivory, the intermediate disturbance hypothesis, maximum levels of productivity observed in successional ecosystems, and widespread nitrogen limitation in terrestrial and aquatic ecosystems can be explained by biotic response to shifts in limiting resources.

Denitrification in a tallgrass prairie landscape - Groffman, P.M.; C. W. Rice; Tiedje, J.M. (Ecology, 1993)
We characterized factors controlling denitrification and quantified rates of N gas production by this process in a tallgrass prairie landscape in central Kansas. The experimental design included three land use classes (unburned, annually burned, and annually burned and grazed) in factorial combination with three slope positions (summit, back—slope, toe—slope), plus a cultivated site in a toe—slope position (10 sites total). Denitrification was measured using an acetylene—based soil core technique four times in 1987, once in early 1988, and six times in 1989. Cores were incubated under field—moist conditions and after amendment with water or water plus nitrate. Microbial biomass and nitrification and dentrification enzyme activities were also measured. Denitrification was higher (P < .05) in unburned sites than in burned, and grazed, and cultivated sites in both 1987/1988 and 1989. The cultivated site consistently had low rates of denitrification relative to the native prairie sites, even when water and nitrate were added. Levels of microbial biomass C and nitrification and denitrification enzyme activities were an order of magnitude lower in the cultivated site than in the native prairie sites. Denitrification rates were highest in the early spring of 1987 and were low at all other times. Although temporal patterns of activity were generally related to patterns of soil moisture, water additions did not stimulate activity in ungrazed prairie soils. Water plus nitrate additions consistently gave significant increases in activity. The results are consistent with previous research that has found that unburned prairie is wetter and has higher concentrations of NO3— in soil solution than burned sites. In certain years, denitrification may be significant to site fertility, landscape water quality, and atmospheric chemistry in the tallgrass prairie region.
Keywords: tallgrass prairie

Detecting change in grasslands using measures of spatial dependence with Landsat TM data - Henebry, G.M. (Remote Sensing of Environment, 1993)
Spatial dependence is a fundamental structure of spatial data that can be readily measured. Change in landscapes can be monitored effectively using measures of spatial dependence. Scale of fluctuation analysis estimates the dimensional extent to which data are significantly autocorrelated by observing the behavior of sample variance under extended local averaging. Algorithms to estimate the one-dimensional scale of fluctuation (correlation length) and two-dimensional scale fluctuation (correlation area) in image data are described. The approach is demonstrated with an analysis of a 9-year TM image series of a tallgrass prairie preserve, Konza Prairie Research Natural Area, to assess the impact of bison on the spatial patterning of vegetation.

Detection of differences in nutrient concentrations by eastern woodrats (Neotoma floridana ) - Post, D.M. (Journal of Mammalogy, 1993)
I tested the ability of a small generalist herbivore, the eastern woodrat (Neotoma floridana), to detect differences in concentrations of protein, energy, and lipid available in two nutritionally complex diet items. Within 24 h of exposure to diets, woodrats consumed a greater amount of a standard diet than diets reduced in energy or lipid by 5, 10, or 20% and a diet reduced by 20% in protein. However, they did not choose the standard over diets reduced in protein by 5 or 10%. When consumption was summed over the 9-day duration of choice trials, individuals chose the standard diet over reduced diets. The ability of woodrats to detect relatively small differences in nutrient concentrations should allow them to make efficient use of available foods.

Distinct Animal-Generated Edge Effects in a Tallgrass Prairie Community - Reichman, O.J.; Benedix, J.H.; Seastedt, T.R. (Ecology, 1993)

The effect of fire on gas exchange and aboveground production in Spartina pectinata wetlands - Johnson, S.R.; Alan K. Knapp (Wetlands, 1993)
Photosynthetic and growth responses ofSpartina pectinata were compared in annually and biennially burned wetlands in a northeastern Kansas tallgrass prairie. Photosynthetic CO2 uptake was consistently higher inSpartina pectinata in annually burned wetlands, and there was a seasonal difference in maximum photosynthetic rates. Plants in annually burned wetlands reached a maximum photosynthetic rate of 38.2 μmol m−2 s−1 in late spring, while maximum photosynthesis in plants of biennially burned wetlands was 28.6 μmol m−2 s−1 in late summer. Culm density in these wetlands was not affected by fire; however, aboveground biomass production, inflorescence density and plant height at anthesis were significantly greater in annually burned wetlands. These results indicate thatSpartina pectinata may be a fire-dependent species, with post-fire responses similar to the dominant grasses in tallgrass prairie as well as otherSpartina congeners.
Keywords: fire; gas exchange; prairie wetlands; production; Spartina pectinata; tallgrass prairie

Effect of prairie-fire ash on food choice by deer mice and hispid cotton rats - Rustiati, E.L.; D.W. Kaufman (The Prairie Naturalist, 1993)

The effects of burning tallgrass prairie on the breeding bird community - Beutler, D.K. (Kansas State University, 1993)
Keywords: tallgrass prairie

Experimental analyses of the effects of prairie ash and sodium on food choices by prairie rodents - Rustiati, E.L. (Kansas State University, 1993)

Experimental analysis of patch dynamics in tallgrass prairie plant communities - Glenn, S.M.; Scott. L. Collins (Journal of Vegetation Science, 1993)
Previous research has indicated that patch structure at small spatial scales (<100m2) in tallgrass prairies was defined by a diverse array of infrequent species because dominant species occurred in all samples at this scale. Also, patch structure was not significantly different from that derived from random species associations. Based on these results, we hypothesized that remo val of a dominant species would have no effect on patch structure in these prairies. We tested this hypothesis by removing a dominant grass, Schizachyrium scoparium (Poaceae), from half of each of four 10 m × 10 m study blocks, and comparing differences in patch structure between control and removal halves before and after removal. The minimum resolution in our study was 1 m2. Patches of similar species composition were defined by cluster analysis of presence/absence data and cover data. Patch sizes ranged from 1 to 34 m2. Following the removal of S. scoparium there was an overall increase in the number of species in the removal half of each block compared to pre-treatment levels. However, the number of patch types and number of spatially mapped groups, based on presence/absence or cover data, did not change between control and removal plots after the removal of S. scoparium. This supports the hypothesis that removal of a large, dominant species would have no effect on patch structure at this scale of resolution in these prairies. Thus, patch structure, as defined here, is an emergent property in these grasslands that is not predictable from changes in species composition. This property of stochastic patch structure results from interactions of processes operating at scales both larger and smaller than our scale of resolution. Stochastic models may provide a reasonable approach to modelling small-scale patch dynamics in tallgrass prairie communities.
Keywords: Grassland community; Patch structure; Removal experiment; Schizachyrium scoparium

Experimental observations of the cutting and climbing of vegetation by hispid cotton rats - Jekanoski, R.D.; D.W. Kaufman (The Prairie Naturalist, 1993)
Behavior of cutting and climbing of herbaceous stems by hispid cotton rats (Sigmodon hispidus) was studied using experimental grass canopies under bright and dark laboratory conditions. When seeds were abundant in ground patches, none of 10 cotton rats climbed and fed in the canopy and only two of the 10 cut grass stalks. In the absence of ground seeds, however, all of nine additional rats either cut canopy stems (24 of 36 total trials; four trials per rat) or climbed into the vegetation for seeds (6 of 36). All climbing and eating in the canopy was done by two small (40-42 g) cotton rats. For rats that did not climb, total cut stems were greater when rats (n=3) were tested for two dark nights and then two bright nights ( hivin x=49.5 stems cut during the four nights) than when rats (n=4) were tested for two bright and then two dark trials ( hivin x=27.7, P lt 0.05). Bright illumination negatively affected stem cutting on nights 1-2 (dark: hivin x=20.0 stems cut during nights 1-2, bright: hivin x=5.3, 0.09 gt P gt 0.08), but not nights 3-4 (bright: hivin x=29.5 stems cut during nights 3-4, dark: hivin x=22.3, P gt 0.10).

Fire frequency and topoedaphic controls of net primary productivity in the tallgrass prairie: Development and tests of remote sensing indices - Benning, T.L. (University of Colorado, 1993)
Keywords: tallgrass prairie

Gallwasp (Hymenoptera: Cynipidae) mortality in a spring tallgrass prairie fire - Fay, P.A.; Samenus, R.J.J. (Environmental Entomology, 1993)
The life history of the cynipid gall wasp, Antistrophus silphii Gillette, leaves it vulnerable to mortality in spring fires in the habitat of its host plant, Silphium integrifolium var. laeve Torrey and Gray. This article examines the mortality of gall wasp larvae during a prescribed bum at the Konza Prairie Research Natural Area in the tallgrass prairie of northeast Kansas. The three goals of the study were to determine (1) if A: silphii galls are most frequently found on the tallest S. integrifolium shoots, (2) if there is a relationship between growing season gall height and overwinter lodging, and (3) if gall wasps can survive fire at the heights at which they are found after overwinter lodging. A 1988 survey found that galls were relatively rare on short shoots (<100 cm), were most abundant on middle-length shoots (100–140 cm), and occurred at random on long shoots (>140 cm), suggesting that gall wasps avoided short shoots but that gall placement did not maximize gall height. A 1992 survey found that growing season gall height was not related to overwinter lodging of galled shoots, indicating that any gall wasp shoot selection patterns affecting later gall height were disrupted by winter lodging. Gall wasps placed at post-overwinter lodging heights were unable to survive an experimental fire, but a few gall wasps survived when placed above the range of naturally-occurring gall heights. A. silphii and other species with similar life histories must re-establish after fire by immigration, with subsequent population levels affected by indirect effects of fire on host-plant quality.
Keywords: Antistrophus silphii; fire; mortality

Gas exchange dynamics in C3 and C4 grasses: consequences of differences in stomatal conductance - Alan K. Knapp (Ecology, 1993)
In full sunlight (photosynthetic photon flux density, 0.4—0.7. μm, PPFD), stomatal conductance to water vapor (g) and transpiration rates (E) are usually higher, and water use efficiency lower, in C3 than C4 species. In the C3 grass Bromus inermis, the difference in conductance between full sun (photosynthetic photon flux [PPFD] > 1500 μmol°m—2°S—1) and shade (PPFD ° 400 μmol°m—2°s—1) was twice as large as in the C4 species Sorghastrum nutans (226.7 vs. 97.8 mmol.m—2.S—1, respectively). Similar differences were measured in four additional C3 and C4 grasses. Variability in PPFD incident on leaves is very common in grasslands, and stomata are known to respond relatively rapidly to fluctuations in this resource. This study evaluated the consequences of different responses in stomatal conductance between C3 and C4 grasses during periods of sunlight variability. Photosynthesis (A, measured as CO2 uptake) and g varied substantially in both B. inermis and S. nutans as PPFD fluctuated between sun and shade levels (4—10 min intervals). Time constants derived form first—order equations describing responses in g after abrupt changes in PPFD indicated that g approached steady—state levels more rapidly in S. nutans than in B. inermis. However, because of the greater magnitude of change in g between sun and shade PPFD in B. inermis, the absolute rate of change in g in this C3 grass was twice as rapid compared to S. nutans (25.7 vs. 12.4 mmol°m—2°s—1°min—1 for reductions in g, respectively). New steady—state levels in g were achieved in 12—13 min after a change in PPFD in S. nutans and 15—19 min in B. inermis. A statistically based two—state (sun/shade) simulation model was used to quantify costs in A and E of the nonsteady—state responses measured for both species as PPFD varied. Costs were calculated as the difference between model output of A or E based on field responses and model output based on hypothetical gas exchange responses in which A and g changed instantaneously. Results suggested that even though the absolute rate of change in g changed was greater in the C3 grass, costs in E during periods of short—term (2—6 min) variations in PPFD were as much as sixfold higher than in the C4 species. Lower cost in E in C4 species during periods of variable PPFD (due to inherently smaller alterations in g) is a previously unrecognized consequence of the C4 photosynthetic pathway. C4 species, and grasses in particular, often are most successful in high—PPFD, water—limited environments in which leaf—level variability in PPFD occurs daily from cloud cover and within—canopy shading. In these environments, stomatal responses that conserve water under nonsteady—state conditions may contribute significantly to the success of C4 species.

GIS Applications in Mammalogy - McLaren, S.B.; J. Brown (Special Publication of the Oklahoma Museum of Natural History, 1993)

Herbivory and its consequences - Dyer, M.I.; Turner, C.L.; Seastedt, T.R. (Ecological Applications, 1993)
We argue that herbivores often induce nonlinear or biphasic growth and development in plants. Collectively these individual responses translate into a system—level optimization curve wherein at low levels of herbivory overall community responses show increases in production potential, whereas extreme herbivory causes extreme reduction in productivity. The transition between these two states defines a point of optimal herbivory in respect to C and N processes.We present four case examples from the literature demonstrating such nonlinear responses, suggesting a widespread existence for this herbivore—plant phenomenon. The nonlinear responses appear to demonstrate temporal and spatial scale dependencies.

The hierarchical continuum concept - Scott. L. Collins; Glenn, S.M.; Roberts, D.W. (Journal of Vegetation Science, 1993)
Two general models have been proposed to explain the structure of the plant community: the community-unit model of Clements and the continuum model of Whittaker and Curtis, the latter based on Gleason's individualistic distribution of species. It is generally assumed that most ecologists now accept the continuum model. Empirical evidence suggests, however, that the continuum in its current form does not fully describe the observed patterns of vegetation along environmental gradients. In this paper, we introduce the hierarchical continuum as a general concept to represent dynamic community structure along regional spatial gradients. The hierarchical continuum is derived from a combination of the individualistic distribution of species, hierarchical assemblage structure, and the core-satellite species hypothesis. The hierarchical continuum concept predicts that the distribution of species across sites in a region will be polymodal, which reflects hierarchical structure, and that the distribution and abundance of species within and between sites will be spatially and temporally dynamic. Regional distribution of plant species in North American tallgrass prairie, southeastern flood-plain hardwood forests, northern upland hardwood forests, and boreal forests were either bimodal or polymodal as predicted by the hierarchical continuum concept. Species in tallgrass prairie were spatially and temporally dynamic with an average turnover of 8–9 species per 50 m2 yr1. In addition, the hierarchical continuum concept predicts the potential for fractal (self-similar) patterns of community structure, and provides a framework for testable hypotheses concerning species distributions along environmental gradients.
Keywords: community structure; Continuum model; Gradient analysis; Hierarchical structure

Increased photosynthesis and water potentials in Silphium integrifolium galled by cynipid wasps - Fay, P.A.; D.C. Hartnett; Alan K. Knapp (Oecologia, 1993)
Interactions between drought, insect herbivory, photosynthesis, and water potential play a key role in determining how plants tolerate and defend against herbivory, yet the effects of insect herbivores on photosynthesis and water potential are seldom assessed. We present evidence that cynipid wasp galls formed by Antistrophus silphii on Silphium integrifolium increase photosynthesis (A), stomatal conductance (g), and xylem water potential (Ψ). Preliminary data showed that in drought-stressed plants galled shoots had 36% greater A, and 10% greater stem Ψ than ungalled shoots, while in well-watered plants leaf gas exchange was not affected by galls. We hypothesized that 1) galled shoots have higher Ψ, g, and A than ungalled shoots, but this differences diminishes if plant drought stress is reduced, and 2) galls can reduce decreases in A and g if water availability decreases. A field experiment testing the first hypothesis found that galls increased g and Ψ, but that differences between galled and ungalled shoots did not diminish after plants were heavily watered. A laboratory test of the second hypothesis using potted Silphium found that galled plants had smaller drops in A and g over a 4-day dry-down period. A vs g and A vs intercellular CO2 concentration relationships were consistent with the explanation that increased Ψ allows galls to increase A by reducing stomatal limitation of A, rather than by altering sink-source relationships or by removing low-Ψ limitations on non-stomatal components of A. Our working hypothesis is that galls increase Ψ and A by reducing the shoot: root ratio so that the plant is exploiting a greater soil volume per unit leaf area. We argue that increased A is an ineffective way for Silphium to compensate for negative effects of gall insect attack. Instead, increased Ψ and A may protect gall insects from variation in resource availability caused by periodic drought stress, potentially reducing negative effects of drought on plant quality and on gall insect populations.
Keywords: Gall insect; photosynthesis; Plant-insect interactions; Silphium integrifolium; Water potential

The interactive effects of fire, bison (Bison bison) grazing and plant community composition in tallgrass prairie - Vinton, M.A.; D.C. Hartnett; Finck, E.J.; J. M. Briggs (American Midland Naturalist, 1993)
Fire and native large herbivore grazing were two important influences on the structure and function of North American grasslands. In 1988 and 1989 the influence of fire regime on grazing patterns of North American bison (Bison bison) was studied on the Konza Prairie in northeastern Kansas. Bison grazing was spatially and temporally nonrandom and was influenced by fire regime and local plant community composition. During the growing season, bison were observed up to 3 x more frequently than expected on watersheds burned in the spring. Summer grazing was concentrated in large watershed areas (79-119 ha) dominated by warm-season, perennial, C4 grasses. During the autumn and winter, bison grazed both burned and unburned watersheds more uniformly but grazed most intensively in areas with large stands of cool-season, C3 grasses. On a smaller spatial scale (5-10 m2), bison selected patches during the growing season with low forb cover dominated by the perennial C4 grass, Andropogon gerardii. Grazed patches were larger on frequently burned than on infrequently burned watersheds. The importance of fire history in determining patterns of bison grazing over the landscape indicates that interactions between bison grazing and fire regime may be important to the composition and spatial heterogeneity of tallgrass prairie vegetation.
Keywords: tallgrass prairie

Jumping spiders nest in red plastic area marker flags in prairies of Northeastern Kansas - Johnson, S.R. (Prairie Naturalist, 1993)

Landscape patterns in soil-water relations and primary production in tallgrass prairie - Alan K. Knapp; Fahnestock, J.T.; Hamburg, S.P.; Statland, L.J.; Seastedt, T.R.; Schimel, D.S. (Ecology, 1993)
Landscape variation in soil water relations, leaf xylem pressure potential (°) and leaf—level net photosynthesis (A) in Andropogon gerardii, and net primary production (NPP) were evaluated during the 1989 and 1990 growing seasons in a northeast Kansas (USA) tallgrass prairie. Landscape patterns were assessed along transects that spanned upland and lowland topographic positions in an annually burned and a long—term unburned watershed. Landscape variability in volumetric soil water content (°) was significantly greater in the unburned watershed (coefficient of variation [CV] = 0.425 and 0.479 for 0—15 and 0—30 cm soil depths in unburned prairie vs. 0.285 and 0.330 for similar depths in the burned watershed). In both watersheds, significantly higher ° and total soil water content (0—30 cm) were measured in lowlands compared to uplands. Topographic anomalies, such as a lowland ridge, resulted in local, small—scale variation in soil moisture that equaled watershed variation. Variation across landscapes in predawn °, which was expected to reflect soil water content, was similar in both watersheds (CV = 0.312). Variation in midday @j was significantly greater across the burned than the unburned watershed in 1990 (maximum range in @j from uplands to lowlands was 0.708 MPa at predawn and 0.662 MPa at midday in the burned watershed). In both watersheds, variation in midday @j was much lower relative to °. Landscape patterns in leaf—level A in A. gerardii, the dominant species in this tallgrass prairie, were inconsistent when upland and lowland sites were compared. During an extended period of drought, A was significantly higher in plants in the unburned watershed. In both watersheds, NPP was strongly correlated with °. However, variability in NPP across topographic gradients in the unburned watershed was much less pronounced (CV = 0.224—0.245) than in the annually burned watershed (CV = 0.364—0.430). Moreover, the slope of the relationship between NPP and ° was significantly greater in the annually burned watershed. We propose that relatively uniform energy limitations across topographic gradients in unburned tallgass prairie, caused by detrital accumulation that absorbs/reflects sunlight, reduced topographic variability in NPP in unburned watersheds. This pattern occurred in unburned watersheds despite greater landscape variation in ° relative to burned watersheds. Analysis of long—term records of NPP from several watersheds supported the hypothesis that variability in NPP associated with topographic position is lower in unburned vs. burned watersheds. Variability in @j across watersheds and between years was muted by negative feedback of canopy leaf area (transpiring surface) on plant—soil water relations. We concluded that patterns in landscape variability in A and @j which may vary significantly over short time intervals, were not good predictors of seasonal carbon dioxide exchange or productivity in this tallgrass prairie. Nonetheless, interactions between A and @j, when combined with nitrogen and energy limitations to A. provide the mechanisms for integrated responses measured across these landscapes.
Keywords: tallgrass prairie

Management practices in tallgrass prairie: Large- and small-scale experimental effects on species composition - D.J. Gibson; Seastedt, T.R.; J. M. Briggs (Journal of Applied Ecology, 1993)
Many studies from grasslands have reported how differing management techniques affect production levels and species composition (e.g., Ehrenreich & Aikman 1963; Wells 1980; Parr & Way 1988). In most studies the main emphasis has been on a single treatment (e.g., mowing, grazing or burning) under either highly controlled small-scale, experimental conditions (Hover & Bragg 1981; Collins 1987; Cox 1988) or less rigorous large-scale descriptive field studies (e.g., Abrams & Hulbert 1987; Gibson & Hulbert 1987). There are inherent strengths and weaknesses to both these approaches. Experimental studies, usually carried out at only one site or in small plots, may reflect local conditions; conversely, large-scale field observations usually lack statistical rigour (Hurlbert 1984) and treatment effects may be obscured by large-scale landscape heterogeneity (e.g. Gibson 1988a).
Keywords: tallgrass prairie

Maximization of aboveground grassland production: the role of defoliation frequency, intensity and history - Turner, C.L.; Seastedt, T.R.; Dyer, M.I. (Ecological Applications, 1993)
Production of tallgrass prairie vegetation was measured on experimental plots in which defoliation intensity and frequency were manipulated by mowing and using movable exclosures on areas chronically grazed by cattle. Defoliation history largely controlled whether or not defoliated plants overcompensated (exhibited enhanced production compared to undefoliated controls) for tissue removal. Plants on chronically grazed sites only compensated for foliage removed by grazers. Production on plots mowed prior to the year of measurement was similar to that on chronically grazed sites, while previously unmowed plots exhibited substantial aboveground overcompensation. Aboveground production was maximized by the most frequent mowing treatment and by intermediate mowing heights. Nitrogen and phosphorus concentrations and amounts in aboveground tissues were increased by mowing and grazing. Current mowing regime was more important than mowing history in determining nitrogen concentrations except very early in the growing season. Effects of grazing and mowing on belowground biomass were inconsistent, but frequent mowing appeared to limit accumulation of belowground N reserves and biomass. In North American grasslands, overcompensation is a nonequilibrium plant response to grazing. Photosynthate that would be stored as reserves and used for root growth and flower and seed production instead is used to replace lost leaf area, thereby resulting in higher foliage productivity. However, under chronic grazing or mowing, vegetation is prevented from maintaining high nutrient and water uptake capacity (large root biomass) and accumulating reserves that allow overcompensation responses.

Mechanisms and processes in vegetation dynamics: Introduction - Agnew, A.D.Q.; Scott. L. Collins; Maarel, E. (Journal of Vegetation Science, 1993)

Methane consumption and carbon dioxide emission in tallgrass prairie: effects of biomass burning and conversion to agriculture - Tate, C.M.; Strigel, R.G. (Global Biogeochemical Cycles, 1993)
Consumption of atmospheric methane and emission of carbon dioxide by soils were measured on unburned and annually burned tallgrass prairie and on adjacent wheat and sorghum agricultural plots in Kansas. Profiles of CH4 and CO2 concentration with soil depth were also measured. Overall patterns of CH4 consumption by soils varied temporally, with soil depth and land use. Mean CH4 consumption for the 200-day sampling period was −1.02 mg CH4 m−2 d−1 (SE=0.13, n=41) for burned prairie, −0.63 (SE=0.09, n=45) for unburned prairie, −0.85 (SE=0.20, n=36) for wheat, and −0.45 (SE=0.08, n=40) for sorghum. Less than 20 % of the variance in CH4 consumption was explained by soil temperature and/or moisture content. Overall patterns of CO2 emission from prairie and agricultural soils varied temporally, but not among land use. Mean CO2 emission for the 200-day sampling period was 15.7 g CO2 m−2 d−1 (SE=1.8, n=41) for burned prairie, 14.5 (SE=1.3, n=45) for unburned prairie, 13.9 (SE=2.1, n=36) for wheat, and 10.3 (SE=2.1, n=40) for sorghum. More than 70% of the variance in prairie CO2 emission rate was explained by soil temperature and moisture. Crop management practices influenced the timing of CO2 emission from agricultural plots but not the net annual rate of emission. Methane concentrations generally decreased and CO2 concentrations increased with soil depth, and the magnitude of CH4 and CO2 flux generally increased with increased magnitude of the soil gas concentration gradient. Fertilization of agricultural fields had no measured effect on CH4 or CO2 flux or on soil gas concentrations.
Keywords: tallgrass prairie

Microbial decomposition of elm and oak leaves in a karst aquifer - Eichem, A.; W. K. Dodds; Tate, C.M.; Edler, C. (Applied Environmental Microbiology, 1993)
Dry Chinquapin oak (Quercus macrocarpa) and American elm (Ulmus americana) leaves were placed in four microcosms fed by groundwater springs to monitor changes in dry mass, ash-free dry mass, and microbial activity over a 35-day period. Oxygen microelectrodes were used to measure microbial activity and to estimate millimeter-scale heterogeneity in that activity. Oak leaves lost mass more slowly than elm leaves. Generally, there was a decrease in total dry weight over the first 14 days, after which total dry weight began to increase. However, there were consistent decreases in ash-free dry mass over the entire incubation period, suggesting that the material remaining after initial leaf decomposition trapped inorganic particles. Microbial activity was higher on elm leaves than on oak leaves, with peak activity occurring at 6 and 27 days, respectively. The level of oxygen saturation on the bottom surface of an elm leaf ranged between 0 and 75% within a 30-mm2 area. This spatial heterogeneity in O2 saturation disappeared when the water velocity increased from 0 to 6 cm s-1. Our results suggest that as leaves enter the groundwater, they decompose and provide substrate for microorganisms. The rate of decomposition depends on leaf type, small-scale variations in microbial activity, water velocity, and the length of submersion time. During the initial stages of decomposition, anoxic microzones are formed that could potentially be important to the biogeochemistry of the otherwise oxic aquifer.

Micromorphology of polygenetic soils in a small watershed, north central Kansas, U.S.A - Wehmueller, W.A.; Ransom, M.D.; Nettleton, W.D. (Developments in Soil Science, 1993)

Observations and modeling of biomass and soil organic matter dynamics for the grassland biome worldwide - Parton, W.J.; Scurlock, J.M.O.; Ojima, D.S.; Gilmanov, T.G.; Scholes, R.J.; Schimel, D.S.; Kirchner, T.; Menaut, J.C.; Seastedt, T.R.; Moya, E.G.; Kamnalrut, A.; Kinyamario, J.I. (Global Biogeochemical Cycles, 1993)
Century is a model of terrestrial biogeochemistry based on relationships between climate, human management (fire, grazing), soil properties, plant productivity, and decomposition. The grassland version of the Century model was tested using observed data from 11 temperate and tropical grasslands around the world. The results show that soil C and N levels can be simulated to within ±25% of the observed values (100 and 75% of the time, respectively) for a diverse set of soils. Peak live biomass and plant production can be simulated within ± 25% of the observed values (57 and 60% of the time, respectively) for burned, fertilized, and irrigated grassland sites where precipitation ranged from 22 to over 150 cm. Live biomass can be generally predicted to within ±50% of the observed values (57% of the time). The model underestimated the live biomass in extremely high plant production years at two of the Russian sites. A comparison of Century model results with statistical models showed that the Century model had slightly higher r2 values than the statistical models. Data and calibrated model results from this study are useful for analysis and description of grassland carbon dynamics, and as a reference point for testing more physiologically based models prediction's of net primary production and biomass. Results indicate that prediction of plant and soil organic matter (C and N) dynamics requires knowledge of climate, soil texture, and N inputs.

Persistence of denitrifying enzyme activity and denitrification dynamics in soil - Picone, L. (Kansas State University, 1993)

Photosynthetic and stomatal responses of Avena sativa (Poaceae) to a variable light environment - Fay, P.A.; Alan K. Knapp (American Journal of Botany, 1993)
The net photosynthetic (A), stomatal conductance to water vapor (g), water use efficiency (WUE = A/transpiration), and leaf water potential (Ψ) responses of cultivated oats (Avena sativa) were determined under an experimental regime of alternating full sun (photosynthetic photon flux density, PPFD > 1,700 μmol·m-2·sec-1) and shade (300-400 μmol·m-2 sec-1 PPFD). Less extensive measurements were made on winter wheat (Triticum aestivum) to test the generality of crop species' responses. The rates of stomatal opening/closing after changes in PPFD in Avena and Triticum were compared with previously determined rates for native grasses and forbs to assess how domestication might have altered stomatal dynamics. Characteristics of Avena under alternating sun and shade were 1) rapid fluctuations in A between full sun (∼27 μmol·m-2 sec-1) and shade rates (∼12-13 μmol m-2·sec-1); 2) slower changes in g, causing progressive stomatal closure during the measurement sequence and possible stomatal limitation of A; 3) no change in leaf Ψ; and 4) a net reduction in WUE. Triticum had similar sun/shade A, g, and WUE dynamics, except that Triticum stomata returned to full-sun g between shade periods. The rates of change of g in Avena and Triticum were lower than for some desert and subalpine native species, but were similar to rates for species in adjoining native habitat. The basic stomatal dynamics of Avena and Triticum may typify many cultivated C3 species, and these data indicate that crop stomatal behavior has not diverged significantly from that of native species.

Preliminary assessment of nitrate at two sites in Kansas-comparison of alluvial aquifer and fractured limestone, Kansas Water Resources Research Institute Report, Contribution No. 305 - G. L. Macpherson (1993)

Regulation of clonal growth and dynamics of Panicum virgatum in tallgrass prairie: effects of neighbor removal and nutrient addition - D.C. Hartnett (American Journal of Botany, 1993)
Clones of the perennial grass Panicum virgatum were studied on the Konza Prairie in northeast Kansas to determine the effects of neighbors, nutrient availability, and physiological integration on ramet population dynamics and clonal growth and architecture. Opposite halves of established clones in the field were subjected differentially to treatments including neighbor removal and nitrogen addition, with intact or severed rhizome connections between halves. Neighborhood competition strongly influenced clone architecture and expansion rates. Removal of neighbors resulted in a >95% increase in radial clone expansion, intraclonal ramet densities, ramet population growth rates, ramet biomass, and percent of stems flowering, averaged over a 4-year period relative to halves or clones with intact competitors. Plant responses suggest that effects of interclonal neighbors are mediated through alteration of the light environment in the clone canopy and water availability. Addition of nitrogen did not affect lateral spread or clone structure, but resulted in significant increases in ramet size, flowering, and seed production. ANOVA revealed no significant effect of rhizome severing or treatment x severing interactions, suggesting that the size of the integrated physiological unit is much smaller than clone size and/or that physiological integration had no effect on clone responses to environmental heterogeneity at the scale of the diameter of established clones.
Keywords: tallgrass prairie

Response of insectivorous birds to emerging aquatic insects in riparian habitats of a tallgrass prairie stream - Gray, L.J. (American Midland Naturalist, 1993)
The relationship between emergence production of aquatic insects from Kings Creek, a tallgrass prairie stream, and densities of insectivorous birds (flycatcher and gleaner guilds) was examined using concurrent measurements of insect emergence and bird densities at six sites on 31 dates during May to July from 1987 to 1990. Daily insect emergence averaged 10.6 g/100-reach in the gallery forest habitat and 2.5 g/reach in the prairie/shrub habitat. Principal taxa included Chironomidae (>50% of emergence biomass), Ephemeroptera and Plecoptera. Common flycatchers were the eastern wood-pewee (Contopus virens) and great crested flycatcher (Myiarchus crinitus) in the gallery forest, and eastern kingbird (Tyrannus tyrannus) in the prairie/shrub habitat. Common gleaners were black-capped chickadee (Parus atricapillus) in the gallery forest and common yellowthroat (Geothlypis trichas) in the prairie/shrub. Flycatcher densities were highly correlated with total emergence in both habitats, but gleaner densities were correlated with emergence only in the gallery forest habitat. Both emergence and insectivore densities varied directly with the stream hydrograph, even over short, postflood recovery periods. Direct observations of feeding behavior showed that insectivores preyed upon a variety of aquatic and nonaquatic prey. Thus stream insects are an important food resource for insectivorous birds in riparian habitats of the tallgrass prairie, although insect emergence is likely insufficient to support observed insectivore densities.
Keywords: tallgrass prairie

Seasonal, temporal, and spatial variation in prey use by coyotes (Canis latrans) - Brillhart, D.E. (Kansas State University, 1993)

Small mammals of wooded habitats of the Konza Prairie Research Natural Area, Kansas - D.W. Kaufman; Kaufman, G.A.; Finck, E.J. (The Prairie Naturalist, 1993)

Stream Research in the LTER Network - Meyer, J.L.; Crocker, T.; D'Angelo, D.; W. K. Dodds; Findlay, S.E.G.; Oswood, M.; Repert, D.; Toetz, D. (LTER Network LTER publication no. 15, 1993)

Using landscape trajectories to assess the effects of radiometric rectification - Henebry, G.M.; Su, H. (International Journal of Remote Sensing, 1993)
We demonstrate a simple procedure, landscape trajectories, for quantifying the effects of radiometric correction on image characteristics. Eleven Landsat Thematic Mapper (TM) images of tallgrass prairie spanning 1987 and 1988 were radiometrically rectified to a common date using a ‘pseudoinvariant features in real space’ method (Schott et ai 1988). The Normalized Difference Vegetation Index (NDVI) was calculated for each raw and corrected image. Four watersheds within the study area were subset and the images were decomposed into spectral intensity (SI), spatial eterogeneity (SH), and spatial dependence (SD) components. Time-ordered vectors in SI-SH-SD space described landscape trajectories. Vector lengths along trajectories were calculated and integrated. Differences between measures on raw and corrected images may be attributable to climatic forcings, time of season, time since fire, and watershed topography. The correction procedure changed SI most and SD least. While the rectification procedure was linear with respect to the entire scene, specific watersheds exhibited nonlinear responses to radiometric rectification.

VA-Mycorrhizal influence on intra- and interspecific neighbor interactions among co-occurring prairie grasses - D.C. Hartnett; Hetrick, B.A.D.; G.T. Wilson; D.J. Gibson (Journal of Ecology, 1993)
1 A strongly obligately mycorrhiza-dependent grass, Andropogon gerardii, and a less dependent species, Elymus canadensis, were grown in intra- and interspecific combination in a target-neighbour experiment with and without mycorrhizal fungi to examine their influence on competition. 2 Mycorrhizal fungi significantly influenced the competitive effects and responses of both plant species. Strong competitive effects of Andropogon disappeared in the absence of mycorrhizas indicating that its competitive dominance in tallgrass prairie is highly dependent upon its mycorrhizal associations. The influence of mycorrhizal fungi on Andropogon responses to neighbours decreased with increasing neighbour density indicating reduced host plant benefit from mycorrhizas under crowded conditions. 3 Effects of mycorrhizas on competition were generally smaller for the less mycorrhiza-dependent Elymus. Elymus effects on target plants were not strongly affected by mycorrhizas. Elymus target plants in competition with Andropogon neighbours performed better when nonmycorrhizal, due to the lack of significant competitive suppression by Andropogon in the absence of mycorrhizas. The influence of mycorrhizal fungi on Elymus responses to Andropogon neighbours increased with increasing neighbour density. Neither mycorrhizas nor phosphorus fertilization had a significant effect on intraspecific competition among Elymus. 4 Patterns of tiller production by target plants were similar to patterns in their total dry weight, indicating that competitive and mycorrhizal effects on target plant size were primarily a result of effects on tiller numbers rather than individual tiller size. 5 The results show that mycorrhizal symbiosis can strongly influence the patterns and intensity of both intraspecific density effects and interspecific competition between co-occurring prairie grasses and that the degree of host-plant benefit derived from mycorrhizas is density dependent.

Water relations and growth of tallgrass prairie forbs in response to selective herbivory by bison - Fahnestock, J.T.; Alan K. Knapp (International Journal of Plant Science, 1993)
The indirect effects of selective grass herbivory by bison (Bison bison) on the xylem pressure potentials (ψ) and primary production of ungrazed tallgrass prairie forbs were assessed during the 1990 growing season on the Konza Prairie Research Natural Area (KPRNA) in northeast Kansas. Responses in three forb species, Vernonia baldwinii, Ambrosia psilostachya, and Aster ericoides, were measured in grazed and adjacent ungrazed patches. Seasonal predawn and midday ψ responses in these forbs were also compared with responses in Andropogon gerardii, the dominant grass in tallgrass prairie. Reductions in grass leaf area by herbivory may result in greater availability of soil water to the remaining forbs, if the forbs and grasses utilize similar soil water resources. Overall, selective herbivory of the grasses had an inconsistent effect on leaf ψ in the remaining forbs. When ψ were relatively high during the growing season, no significant differences in water status were detected between A. gerardii and the forbs. However, when ψ were low, predawn and midday ψ were higher in V. baldwinii (as much as 1.0 MPa), and midday ψ were higher in A. psilostachya (0.5 MPa) compared with A. gerardii. In contrast, ψ were not significantly different between A. ericoides and A. gerardii. Grazing by bison substantially increased light availability to ungrazed forbs (> 40%) in grazed relative to ungrazed areas. Compared with ungrazed areas, end-of-season aboveground biomass in grazed patches was 40% greater for individuals of A. psilostachya and 33% and 26% greater for reproductive biomass and floret numbers, respectively, in V. baldwinii. We conclude that the potential benefits of selective grass herbivory on forb water relations may be reduced or offset by other factors such as significant alterations in the microclimate of grazed patches. Nonetheless, increased productivity in grazed patches in two of the three forbs studied indicates that selective consumption of grasses by bison may benefit some forb species.
Keywords: Water relations

Water relations of Juniperus virginiana and Andropogon gerardii in an unburned tallgrass prairie watershed - Axmann, B.D.; Alan K. Knapp (Southwestern Naturalist, 1993)
We assessed several factors influencing the success of Juniperus virginiana in unburned tallgrass prairie by mapping the distribution of individuals in a 21-ha watershed on the Konza Prairie Research Natural Area in NE Kansas. We also compared the water relations of this tree with those of the dominant grass Andropogon gerardii. No general relationships were detected between the distribution of J. virginiana and plant water status, plant size, soil type, slope, aspect or elevation. Leaf xylem pressure potential (ψ) in upland trees was significantly lower (0.44 MPa) than in lowland trees, but only during the driest portion of the growing season. In contrast, topographic position influenced ψ more strongly in A. gerardii with ψ in upland plants as much as 1.0 MPa lower than in lowland plants. During wetter periods, photosynthetic rates in A. gerardii were higher than in J. virginiana in uplands, but the reverse occurred during the driest period of the growing season. The ability of J. virginiana to maintain higher ψ and higher photosynthetic rates relative to A. gerardii during periods of water limitation may contribute to its success in tallgrass prairie protected from fire.
Keywords: Water relations

Absence of interspecific competition among tallgrass prairie grasshoppers during a drought - Evans, E.W. (Ecology, 1992)
The grasshoppers Phoetaliotes nebrascensis and Orphulella speciosa overlap extensively in both diet and habitat in native tallgrass prairie at Konza Prairie, Kansas. I tested for interspecific competition between these two species during a drought year when primary productivity in the prairie was unusually low. In late June 1989, I transferred young nymphs of P. nebrascensis among enclosed plots (each 550—900 m2) to produce three pairs of plots with grasshoppers removed or added. Pretransfer densities in the six plots were estimated at 6 nymphs/m2. Experimental transfers resulted in densities of P. nebrascensis in addition plots 2—3 times as large as in paired removal plots; significant differences in density between addition and removal plots persisted throughout the summer. Densities of O. speciosa in plots with P. nebrascensis removed or added did not differ significantly throughout the growing season of 1989, nor in early summer of 1990. Furthermore, growth and development of O. speciosa in these plots (as measured by rate of maturation, and adult femur length and mass in 1989) were not reduced in the presence of high densities of P. nebrascensis, nor was reproductive potential (measured as the ratio of young nymphs present in early summer 1990 to adults in late summer 1989). These results are similar to those of a previous experiment at the same site during 1987 when primary productivity was moderate. Even under the extreme conditions of 1989, with particularly high ratios of grasshoppers to available food resources, variation in P. nebrascensis density did not adversely affect populations of O. speciosa. These results contrast with recent results for sedentary phytophagous insects, but are consistent with the hypothesis that free—ranging insect herbivores may rarely experience interspecific competition for food resources.
Keywords: tallgrass prairie

American bison dispersion: A geographic information system predictive model - J.D. Bathgate (Kansas State University, 1992)

Carbon and nitrogen dynamics and microbial ecology in tallgrass prairie - Garcia, F.O. (Kansas State University, 1992)
Keywords: tallgrass prairie

Change in nutrient content of foods stored by eastern woodrats (Neotoma florida) - Post, D.M. (Journal of Mammalogy, 1992)
I determined changes in nutrient content of plants cached by eastern woodrats (Neotoma floridana) after 60 and 120 days storage in a cache environment. The energy content of dogwood fruits (Cornus drummondii) declined significantly due to a decline in lipid content. Concentrations of other nutrients in dogwood fruits remained relatively stable as did nutrient concentrations of green ash seed (Fraxinus pennsylvanica) and redbud seed (Cercis canadensis). However, some small fluctuations in nutrients were observed. The decrease in energy content of cache material may have a significant negative impact on some woodrats that have only a limited amount of food stored in caches.

Characterization of a groundwater community dominated by Asellus tridentata (Isopoda) - Edler, C.; W. K. Dodds (1992)

Collected data of the first ISLSCP field experiment: Volume 2: Satellite Imagery 1987-1989 - Strebel, D.E.; Landis, D.R.; Newcomer, J.A.; Elburg-Obler, D.; Meeson, B.W.; Agbu, P.A. (1992)
Keywords: ISLSCP

Collected data of the first ISLSCP field experiment: Volume 3: NS001 Imagery 1987 to 1989 - Strebel, D.E.; Landis, D.R.; Newcomer, J.A.; Goetz, S.J.; Meeson, B.W.; Agbu, P.A.; McManus, J.M.P. (1992)
Keywords: ISLSCP

Collected data of the first ISLSCP field experiment: Volume 4: ASAS; PBMR Imagery 1987-1989 - Strebel, D.E.; Landis, D.R.; Newcomer, J.A.; Meeson, B.W.; Agbu, P.A.; McManus, J.M.P. (1992)
Keywords: ISLSCP

Density-independent factors affecting the avian diversity of the tallgrass prairie community - Zimmerman, J.L. (Wilson Bulletin, 1992)
Keywords: tallgrass prairie

Disturbances in tallgrass prairie: local versus regional effects on community heterogeneity - Glenn, S.M.; Scott. L. Collins; D.J. Gibson (Landscape Ecology, 1992)
Keywords: tallgrass prairie

The effect of prairie management practices on mycorrhizal symbiosis - Bentivenga, S.P.; Hetrick, B.A.D. (Mycologia, 1992)

The effect of simulated herbivory on Andropogon gerardii and Panicum virgatum as influenced by time of defoliation, fire, and plant competition - Brown, M. (Kansas State University, 1992)
Keywords: fire

Effects of bison grazing on Andropogon gerardii and Panicum virgatum in burned and unburned tallgrass prairie - Vinton, M.A.; D.C. Hartnett (Oecologia, 1992)
Responses to clipping and bison grazing in different environmental contexts were examined in two perennial grass species, Andropogon gerardii and Panicum virgatum, on the Konza Prairie in northeastern Kansas. Grazed tillers had lower relative growth rates (RGR) than clipped tillers following defoliation but this difference was transient and final biomass was not affected by mode of defoliation. Grazed tillers of both species had higher RGR throughout the season than ungrazed tillers, resulting in exact compensation for tissue lost to defoliation. However, A. gerardii tillers which had been grazed repeatedly the previous year (1988) had reduced relative growth rates, tiller biomass and tiller survival in 1989. This suggests that the short-term increase in aboveground relative growth rates after defoliation had cost to future growth plant growth and tiller survival. In general, two species had similar responses to defoliation but their responses were altered differentially by fire. The increase in RGR following defoliation of A. gerardii was relatively greater on unburned than burned prairie, and was relatively greater on unburned than burned prairie, and was influenced by topographic position. P. virgatum responses to defoliation were similar in burned and unburned prairie. Thus grazing, fire, and topographical position all intreract to influence tiller growth dynamics and these two species respond differently to the fire and grazing pattern to influence a plants' grazing history and thus its long tern performance. Key words: grazing, bison, fire, Andropogon gerardii, Panicum virgatum
Keywords: tallgrass prairie

Effects of fire on tree spatial patterns in a tallgrass prairie landscape - J. M. Briggs; D.J. Gibson (Bulletin of Torrey Botanical Club, 1992)
Spatial patterns of trees invading a tallgrass prairie in NE Kansas, USA were examined using a Geographical Information System. Without burning and with adequate moisture levels, the number of trees increased over a five year period by over 60%, while in an area burned annually the number of trees decreased. Under a variety of burning regimes, Juniperus virginiana and Celtis occidentalis were significantly more uniform in their distribution pattern than Populus deltoides and Gleditsia triacanthos. In addition, three tree species (G. triacanthos, J. virginiana and U. americana) had a significant increase in the degree of aggregation with increasing tree height, while C. occidentalis showed no relationship between aggregation and tree height. There were significant associations between adult and juvenile trees at various scales, with bird dispersed J. virginiana having a higher critical distance (39 m) than wind dispersed G. triacanthos and U. americana. The spatial pattern of tree species appears to be affected by the means of dispersion; trees with wind-dispersed seeds had clumped distributions, whereas most trees with bird-dispersed seeds were regular to random in their dispersion patterns. The spatial pattern of trees invading tallgrass prairie is a function of the burning regime, dispersal vectors, habitat availability, and reproductive mode. Key words: tallgrass prairie, spatial patterns, trees, Geographical Information System
Keywords: Wind

Effects of management and topography on the radiometric response of a tallgrass prairie - Turner, C.L.; Seastedt, T.R.; Dyer, M.I.; Kittel, T.G.F.; Schimel, D.S. (Journal of Geophysical Research, 1992)
Keywords: tallgrass prairie

Effects of scale and disturbance on rates of immigration and extinction of species in prairies - Glenn, S.M.; Scott. L. Collins (Oikos, 1992)
Relationships between local annual immigration and extinction rate of plant species and total species richness were determined from long-term data in permanent plots in tallgrass and shortgrass prairies in Kansas. Combining plots resulted in higher equilibrium numbers of species as predicted from immigration and extinction rates. Immigration and extinction rates also increased with scale. Extinction rates are higher because the regional scale supports more rare species which, in turn, have high probabilities of extinction. We also tested the hypothesis that extinction rates would be higher on burned versus unburned grasslands, and that immigration rates would be higher on grazed versus ungrazed grasslands. Extinction rates were positively correlated with the number of species at a site, and this relationship was not altered by burning or grazing. Immigration rates were variable, but were sometimes positively correlated with growing season precipitation. Immigration rates decreased in years sites were burned. Therefore, after fire, the number of species going locally extinct was still dependent on earlier species richness, but the number of species added to the site was reduced. Variances in immigration and extinction rates were high, therefore, confident predictions regarding the effects of burning or grazing regimes on species richness could not be made. Variance in rates of immigration and extinction results in a range of values within which the equilibrium number of species fluctuates randomly
Keywords: fire

Effects of soil temperature on growth, biomass allocation and resource acquisition of Andropogon gerardii Vitman - DeLucia, E.H.; Heckathorn, S.A.; Day, T.A. (New Phytologist, 1992)
Keywords: soil temperature

Effects of tallgrass prairie vegetation on the concentration and seasonality of nitrate\-nitrogen in soil water and streams - Ramundo, R.A.; Tate, C.M.; Seastedt, T.R. (University of Northern Iowa, 1992)
Inorganic nitrogen concentrations in tallgrass prairie soils and streams exhibit a sinusoidal seasonal pattern; nitrate levels are relatively high in winter and low in summer. The pattern is not observed in either rainfall or canopy drip (throughfall). Thus, the pattern is created by plant root-microbial interactions; when roots are not active, nitrates accumulate and can be leached from the soil. We used nitrogen fertilizer and herbicide in a factorial experiment to test the strength of root uptake activities on soil water nitrogen. Soil-water nitrate concentrations were 10 times higher when prairie roots were deactivated by application of a foliar herbicide. Ammonium nitrogen concentrations were unaffected. When fertilizer was added, nitrate levels of soil water beneath herbicide-treated vegetation were double that of untreated prairie. Mineralization of nitragen from herbicide-treated roots was not believed to be the source of the increased nitrate. These and previous studies at Konza Prairie emphasize the importance of plant cover in maintaining low nitrate concentrations of streams
Keywords: tallgrass prairie

Evaluation of the closed-chamber method for estimating methane emissions from aquatic plants - Alan K. Knapp; Yavitt, J.B. (Tellus, 1992)
Closed flow chambers are commonly used to measure CH4 emissions from aquatic plants. We monitored environmental and plant physiological responses to closed chambers during measurements of CH4 emission from Typha latifolia (cattails) to evaluate potential errors in emission estimates. In 1990, two wetlands were studied: one in NE Kansas and one in central New York. Leaves and stems of Typha enclosed in gas-impermable, collapsible bags were exposed to rapid increases in chamber air temperature and, thus, tissue temperatures (up to 9oC above ambient) as well as rapid reductions in both CO2 partial pressure due to photosynthesis and the leaf-to-air water vapor pressure deficit due to transpiration. These rapid (< 5 min) environmental changes within chambers are known to affect stomatal aperture through which CH4 exists Typha leaves. Indeed, stomatal conductance (g) increased up to 42% compared to control leaves after 19 min of enclosure in chambers, and chamber effects on interactions between irradiance and g were detected. The duration of enclosure also critically affected the CH4 gradient within chambers. Estimated CH4 emission from leaves in chambers sampled after 19 min (3 nmol m-2s-1) was 10-fold lower than estimates based on 30-s sampling periods (30 nmol m-2s-1) due to reduction in the leaf-to-air concentration gradient for CH4. Since closed chambers 1)induce alterations in g, 2)may result in rapid environmental changes, and 3)lead to almost instantaneous reductions in leaf-to-air concentration gradient for CH4 diffusion, we suggest that only very short enclosure times should be used when measuring CH4 emission from plants

Fire and the development of oak forests - Abrams, M.D. (BioScience, 1992)
Fire, whether it has occurred to a low, moderate, or high degree, seems to be the common denominator for the development of oak forests on upland sites and their past and present ecological status. This article reviews pre- and postsettlement forest conditions for the major oak dominated ecosystems throughout eastern North America to discern how the influence of fire and human activity have affected the past and present ecology of oak forests and how these factors will likely continue to affect forests in the future
Keywords: fire

Fire frequency and community heterogeneity in tallgrass prairie vegetation - Scott. L. Collins (Ecology, 1992)
Few studies have directly addressed the effects of disturbance on spatial and temporal heterogeneity. Spatial hererogeneity is the degree of dissimilarity in species composition from one point to another in a community, wheras temporal heterogeneity is compositional change within a site over time. The purposes of this study were to determine 1) if a quadratic relationship exists between within-site heterogenity and disturbance frequency as predicted by the intermediated disturbance hypothesis (IDH), 2)if disturbed and undistubed sites have similar heterogeneity as implied by the disturbance heterogeneity hypothesis (DHM), and whether or not these results differed with scale, and 3)if there is a relationship between spatial and temporal heterogeneity as implied by the DHM. Analyses were based on plant species composition data collected over 9 yr in quadrats permanently located in experimental management units subjected to different burning frequencies at Konza Prairie Research Natual Area, Kansas, USA. The relationship between disturbance frequency and within-site heterogeneity was opposie that predicted by the IDH. Heterogeneity was lowest at intermediate disturbance frequencies. Heterogeneity in anually burned prairie was lower than in unburned prairie and prairies burned once every 4 yr in contrast to predictions of the DHM. However, this relationship did not hold at larger spatial scales. There was a positive relationship between disturbance frequency and within-site heterogenity was opposite that predicted by the IDH. Heterogenity was lowest at intermediate disturbance frequencies. Heterogeneity in annually burned prairie was lower than in unburned prairie and prairies burned once every year in contrast to predictions of the DHM. However, this relationship did not hold at larger spatial scales. There was a positive relationship between within-site spatial and temporal heterogeneity on annually burned sites, sites burned once every 4 yr, and nearly so on sites burned every other year. Within-site heterogeneity was negatively correlated with cover of Andropogon gerardii, and positively correlated with total richness and species diversity. Studies of variation, in addition to averages, will increase our ability to predict patterns of species distribution and abundance within and between communities in response to disturbance. Key words: Andropogon gerardii, fire, grassland vegetation, intermediate disturbance hypothesis, Konza Prairie, spatial heterogeneity, species density, species diversity
Keywords: tallgrass prairie

Geographic information systems for modeling bison impact on Konza Prairie, Kansas - Nellis, M.D.; J.D. Bathgate; J. M. Briggs (GIS/LIS Proceedings, 1992)
Keywords: Information Systems

Geographic variation in length of tail of white-footed mice (Peromyscus leucopus) in Kansas - Kaufman, D.M.; D.W. Kaufman (Journal of Mammalogy, 1992)

Ground-water chemistry under tallgrass prairie, Central Kansas, USA - G. L. Macpherson (1992)
Keywords: tallgrass prairie

The growth and physiological responses of Silphium integrifolium to gall insect attack - Fay, P.A. (Kansas State University, 1992)
Keywords: insect

Growth and transition: Remote sensing and geographic information systems at Kansas State University - Nellis, M.D.; J. M. Briggs; Seyler, H.L. (Photogrammetric Engineering and Remote Sensing, 1992)
Remote sensing and geographic information systems education and research at Kansas State University have grown tremendously in the past decade. Dramatic improvements in hardware and software have enhanced offerings in a wide range of spatial analysis (including remote sensing) courses. Success in extramural funding through such agencies as the U.S. Agency for International Development and the National Science Foundation have created a major research thrust in Kansas State University's Geography and Biology programs relative to the application of remote sensing and geographic information systems for natural resource assessment and landscape ecology. The State of Kansas initatives have also enhanced Kansas State University's role in providing a significant contribution in remote sensing/geographic information systems research and education
Keywords: Information Systems

Indications of landscape condition at many scales - Milne, B.T. (Ecological Indicators, 1992)

Indirect effects of selective grass herbivory by bison on tallgrass prairie forbs - Fahnestock, J.T. (Kansas State University, 1992)
Keywords: tallgrass prairie

Leaf gas exchange in Quercus macrocarpa (Fagaceae): rapid stomatal responses to variability in sunlight in a tree growth form - Alan K. Knapp (American Journal of Botany, 1992)

Local polyploid variation in the native prairie grass Andropogon gerardii - Keeler, K.H. (American Journal of Botany, 1992)

Localized dynamics of earthworm populations in relation to bison dung in North American tallgrass prairie - James, S.W. (Soil Biology & Biochemistry, 1992)
Keywords: tallgrass prairie

Mass loss and nitrogen dynamics of decaying litter of grasslands: the apparent low nitrogen immobilization potential of root detritus - Seastedt, T.R.; Parton, W.J.; Ojima, D.S. (Canadian Journal of Botany, 1992)
Litter-bag studies and simulation modeling were used to examine the relationship between mass loss and nitrogen content of decaying prairie foliage and root litter. In contrast with forest studies, grassland roots were low in lignin and nitrogen, decayed more rapidly than foliage, and demonstrated very low nitrogen immobilization potentials. Our findings agree with reports indicating that buried substrates with high C:N ratios do not immobilize substantial amounts of nitrogen-limited environments induce steeper slopes in the mass loss-nitrogen concentration relationship. However, results suggesting rapid nitrogen mineralization contradict our own studies demonstrating reduced inorganic nitrogen availability in soils of frequently burned prairie. Simulation of observed patterns using the CENTURY grassland model indicated that these results could not occur without creating soil organic matter with unrealistically high C:N ratios. Litter-bag studies of buried substrates therefore may provide an incomplete perspective on the mass loss and nitrogen dynamics of buried litter in grassland and agroecosystem soils. key words: Andropogon gerardii, C:N ratio, decomposition, immobilization, mineralization, nitrogen

Mineralization of organic phosphorus by vesicular-arbuscular mycorrhizal fungi - Jayachandran, K.; Schwab, A.P.; Hetrick, B.A.D. (Soil Biology & Biochemistry, 1992)

Partitioning of dissolved inorganic or organic phosphorus using acidified molybdate and isobutanol - Jayachandran, K.; Schwab, A.P.; Hetrick, B.A.D. (Soil Science Society of American Journal, 1992)

Population ecology of thirteen-lined ground squirrels in ungrazed tallgrass prairie manipulated by fire - Clark, B.K.; D.W. Kaufman; Kaufman, G.A.; Gurtz, S.K.; Bixler, S.H. (1992)
From March 1983 to October 1987, thirteen-lined ground squirrels (Spermophilus tridecemlineatus Mitchill) were studied in ungrazed tallgrass prairie manipulated by fire on the Konza Prairie Research Natural Area, Kansas. Overall abundance varied among years (2.6 animals/ha in 1985; 5.6 animals/ha in 1986); however, no significant variation in sex ratio was observed (overall average=52% males for adults, 48% males for juveniles). Fire had a positive effect on ground squirrels; abundance was significantly higher in burned than unburned prairie during the year of a fire and in more recently than less recently burned prairie during years following a fire. Ground squirrels also selected hillsides with exposed rocks (breaks) over upland and lowland prairie sites. Although females and males selected similar habitats, home ranges were significantly larger for adult males (average=0.56 ha) than for adult females (0.36 ha). Both adult females and males caught on the study area typically were residents rather than transients. Further, overwinter survival did not differ between adult females and males. Overwinter survival of juvenile females was similar to adults; however, no juvenile males overwintered on the study area
Keywords: tallgrass prairie

Relationships of mycorrhizal symbiosis, rooting strategy and phenology among tallgrass prairie forbs - Hetrick, B.A.D.; G.T. Wilson; Todd, T.C. (Canadian Journal of Botany, 1992)
Keywords: tallgrass prairie

Seasonal and experimental variation in population structure of earthworms in tallgrass prairie - James, S.W. (Soil Biology & Biochemistry, 1992)
Keywords: tallgrass prairie

Seasonal and temperature effects on mycorrhizal activity and dependence of cool- and warm-season tallgrass prairie grasses - Bentivenga, S.P.; Hetrick, B.A.D. (Canadian Journal of Botany, 1992)
Keywords: tallgrass prairie

Soil invertebrate and plant responses to mowing and Carbofuran application in a North American tallgrass prairie - Todd, T.C.; James, S.W.; Seastedt, T.R. (Plant and Soil, 1992)
Keywords: tallgrass prairie

Time budgets of confined nothern cardinals and Harris' sparrows in flocks and differences in observer data - Shuman, T.W.; Robel, R.J.; Kemp, K.E.; Zimmerman, J.L. (Journal of Field Ornithology, 1992)

Transformed vegetation index for measuring spatial variation in drought impacted biomass on Konza Prairie, Kansas - Nellis, M.D.; J. M. Briggs (Transactions of the Kansas Academy of Science, 1992)

The vegetation cover, seed bank, seed rain, and seed reproduction of the relictual tallgrass prairie of Boulder county, Colorado - Santanachote, K. (University of Colorado, 1992)
Keywords: tallgrass prairie

An analysis of factors affecting the caching behavior of the eastern woodrat (Neotoma floridana) - Post, D.M. (Kansas State University, 1991)

A behavioral analysis of the plains pocket gopher (Geomys bursarius) - Benedix, J.H. (Kansas State University, 1991)

Bryophytes of konza prairie research natural area, Kansas - Merrill, G.L. (The Bryologist, 1991)
Fifty-eight species of mosses (37 genera, 18 families( and 4 species of liverworts (3 genera, 3 families) are reported from Konza Prairie Research Natural Area, a 3,487 hectare tallgrass prairie preserve in northeastern Kansas. Factors affecting the growth and persistence of bryophytes on the prairie are discussed. The occurrence of bryophytes in presettlement tallgrass prairies was probably influenced by natural disturbance due to grazing and recurring fire
Keywords: tallgrass prairie

Constraints on the growth and allocation patterns of Silphium integrifolium (Asteraceae ) caused by cynipid gall wasps - Fay, P.A.; D.C. Hartnett (Oecologia, 1991)

The contribution of mycorrhizal symbiosis to tallgrass prairie - Bentivenga, S.P. (Kansas State University, 1991)
Keywords: tallgrass prairie

Controls of nitrogen limitation in tallgrass prairie - Seastedt, T.R.; J. M. Briggs; D.J. Gibson (Oecologia, 1991)
The relationship between fire frequency and N limitation to foliage production in tallgrass prairie was studied with a series of fire and N addition experiments. Results indicated that fire history affected the magnitude of the vegetation response to fire and to N additions. Sites not burned for over 15 years averaged only a 9% increase in foliage biomass in response to N enrichment. In contrast, foliage production increased an average of 68% in response to N additions on annually burned sites, while infrequencly burned sites, burned in the year of the study, averaged a 45% increase. These findings are consistent with reports indicating that reduced plant growth on unburned prairie is due to shading and lower soil temperatures, while foliage production on frequently burned areas is constrained by N availability. Infrequent burning of unfertilized prairie therefore results in maximum production response in the year of burning relative to either annually burned or long-term unburned sites. Foliage biomass of tallgrass prairie is dominated by C4 grasses; however, forb species exhibited stronger production responses to nitrogen additions than did the grasses. After four years of annual N additions, forb biomass exceeded that of grass biomass on unburned plots, and grasses exhibited a negative response to fertilizer, probably due to competition from the forbs. The dominant C4 grasses may out-compete forbs under frequent fire conditions not only because they are better adapted to direct effects of burning, but because they can grow better under low available N regimes created by frequent fire. Key words: Andropogon gerardii, fire, nitrogen, prairie, productivity
Keywords: fire; soil temperature; tallgrass prairie

Cryptosporidium and Giardia in surface waters in and around Manhattan, Kansas - Todd, C.S.; Phillips, M.S.; Marchin, G.L.; Upton, S.J. (Transaction of the Kansas Academy of Science, 1991)
Cryptosporidium spp. and Giardia spp. are intestinal parasites that can be transmitted through water contaminated by feces. Over a 16 month period, surface waters were examined in Kansas in order to measure local geographic distribution and seasonal fluctuation of oocyst and cyst populations. Cryptosporidium and/or Giardia were found in 86 percent of the locations surveyed

Effect of leaf rolling on gas exchange and leaf temperature of Andropogon gerardii and Spartina pectinata - Heckathorn, S.A.; DeLucia, E.H. (Botanical Gazette, 1991)
We examined the effect of leaf rolling on CO2 and water vapor exchange of two C4 prairie grasses with contrasting patterns of leaf rolling. Andropogon gerardii (big bluestem) is a drought-resistant species with predominantly hypostomatal leaves that fold (adaxial surface inward) in response to low leaf water potential, while leaves of Spartina pectinata (prairie cordgrass), a mesic species, are epistomatal and roll into spirals (also adaxial surface inward). Adaxial stomata of both species are closed in completely rolled or folded leaves; thus these leaf movements have a minor effect on total leaf conductance. Energy budget calculations indicate that leaf rolling reduces transpiration by 7%-13% in water-stressed plants by lowering leaf temperature and, therefore, leaf-to- air vapor pressure deficit. This reduction is small relative to the direct effect of stomatal closure on transpiration. However, small decreases in transpiration, leaf temperature, and incident irradiance associated with leaf rolling may decrease the potential for photoinhibition, prolong physiological activity, and increase survival during drought
Keywords: Leaf temperature

Effects of fire exclusion on tallgrass prairie and gallery forest communities in eastern Kansas - Abrams, M.D.; D.J. Gibson (Southeastern Forest Experiment Station, 1991)
The purpose of this review is to synthesize a long-term body of research dealing with fire exclusion effects on tallgrass prairie and gallery forest communities on Konza Prairie in eastern Kansas. Upland and lowland prairie communities burned in spring at intervals ranging from 1-11 years were consistently dominated (79-90 percent cover) by Andropogon gerardii. With this increasing interval between fires other dominant warm-season grasses, A. scoparius and Sorghastrum nutans, had decreased cover, whereas forbs and woody species had increased cover. Aboveground biomass was higher on an annual burned versus unburned lowland prairie, due to stimulated graminoid production. Sites unburned for 10 or more years were converting to woodlands dominated by Juniperus, Ulmus, Gleditsia and Celtis. Older gallery forests occurred in stream channels and ravines and were comprised of overstory Quercus and Celtis and understory Celtis, Cercis and Ulmus. The extent of gallery forests on Konza Prairie dramatically increased from the time of European settlement (1850) to present; this has been attributed to decreased fire frequency and intensity in the region. With continued fire exclusion this century further succession in these forests has caused oak replacement by more shade tolerant species
Keywords: tallgrass prairie

Effects of fire in tallgrass prairie on growth and reproduction of prairie coneflower (Ratibida columnifera: Asteraceae) - Harnett, D.C. (American Journal of Botany, 1991)
Effects of fire on growth and reproduction of the perennial forb Ratibida columnifera were studied on the Konza Prairie Research Natural Area in northeastern Kansas, USA. Populations were sampled in seven different tallgrass prairie watersheds that varied in fire frequency and in the number of years elapsed since the last fire. Plants from sites not burned for many years were 2.6 times larger and produced 50% more stems than plants from recently burned sites. Number of seeds per plant was also higher in long-unburned sites due to greater numbers of flower heads per plant and greater numbers of achenes produced per head. Reproduction effort (ratio of inflorescence biomass to total vegetative biomass) was 33% lower in annually burned prairie than in any of the other sites. Significant differences in the relationships of inflorescence biomass to vegetative plant biomass in burned vs unburned sites indicated that burning causes direct changes in plant reproductive effort independent from its effects on plant size. There was no clear relationship between patterns of seed production among sites and patterns of R. columnifera abundance. Ratibida columnifera responses to fire are most likely a result of changes in the relative competitive abilities of forbs and the dominant perennial grasses due to post-fire changes in abiotic conditions rather than a result of direct effects of fire on the fate of buds and subsequent vegetative and floral development
Keywords: tallgrass prairie

Effects of food perishability, distance, and competitors on caching behavior of eastern woodrats - Post, D.M.; Reichman, O.J. (Journal of Mammalogy, 1991)

Effects of mycorrhizal fungus species and metalaxyl application on microbial suppression of mycorrhizal symbiosis - Hetrick, B.A.D.; G.T. Wilson (Mycologia, 1991)

Effects of plant litter on foraging and nesting behavior of prairie rodents - Clark, B.K.; D.W. Kaufman (Journal of Mammalogy, 1991)

Estimating aboveground biomass in tallgrass prairie with the harvest method: determining proper sample size using jackknifing and Monte Carlo simulations - J. M. Briggs; Alan K. Knapp (The Southwestern Naturalist, 1991)
Sample adequacy for estimating aboveground biomass in the Flint Hills (Kansas) tallgrass prairie was determined by using a combination of jackknifing and Monte Carlo simulations. Based on this analysis, we concluded that 14 and 16 0.1 -m2 (20 by 50 cm) quadrats should be harvested in burned and unburned sites, respectively, when estimating total, live graminoid and previous years dead biomass. However, 20 quadrats should be harvested to detect at least a 20% difference in production between sites due to treatments such as fire. Due to high variability in forb biomass, other measurements (cover or density) may be more appropriate for detecting fire effects on this group of plants
Keywords: tallgrass prairie

Experimental manipulation of herbivores in North American native tallgrass prairie: responses of aboveground arthropods - Evans, E.W. (American Midland Naturalist, 1991)
Keywords: tallgrass prairie

Fire, mowing and insecticide effects on soil Sternorrhyncha (Homoptera) densities in tallgrass prairie - Seastedt, T.R.; Reddy, V.M. (Journal of the Kansas Entomological Society, 1991)
Densities of soil-dwelling Sternorrhyncha (Aphidoidea + Coccoidea) in tallgrass prairie significantly increased in response to application of a foliar insecticide (carbaryl). Densities of these soil homopterans also increased in response to mowing of vegetation. Spring burning of vegetation to enhance grass production did not have a strong affect on total populations. Resource abundance of cool season grasses, as mediated by competition from other herbivores, best explain these patterns
Keywords: tallgrass prairie

Geomorphology and geomorphic history of the Konza Prairie Research Natural Area, Riley and Geary Counties, Kansas - Smith, G.N. (Kansas State University, 1991)

Glomus Mortonii sp. Nov., a previously undescribed species in the Glomaceae isolated from the tallgrass prairie in Kansas - Bentivenga, S.P.; Hetrick, B.A.D. (Mycotoxon, 1991)
Keywords: tallgrass prairie

Grassland mammal communities and fire - D.W. Kaufman; Kaufman, G.A. (Region 6, Mountain-Prairie Region, United States Fish and Wildlife Service, 1991)
Keywords: fire

Hematological and blood chemistry parameters of American bison grazing on Konza Prairie, Kansas - Vestweber, J.G.; Johnson, D.E.; Merrill, G.L.; Staats, J.J. (Journal of Wildlife Diseases, 1991)
Normal hematological and blood chemistry were measured in 45 American bison (Bison bison) that were divided into three age groups for comparison. There was a statistically significant (P less than .05) increase with advancing age in mean corpuscular volume, mean corpuscular hemoglobin, absolute neutrophil and eosinophil counts, total protein, globulin, creatinine, and blood urea nitrogen. There was a statistically significant (P less than .05) decrease with advancing age in levels of sorbital dehydrogenase, alkaline phosphatase, glucose, sodium, calcium and phosphorus. Key words: Hematology, blood chemistry, American bison, Bison bison, age groups

Image textural measures as indices of landscape patterns - Musick, B.H.; Grover, H.D. (Quantitative Methods in Landscape Ecology: The Analysis and Interpretation of Landscape Heterogeneity, 1991)

Importance of spatial and temporal dynamics in species regional abundance and distribution - Scott. L. Collins; Glenn, S.M. (Ecology, 1991)

Improving use of existing data - Tate, C.M.; Jones, C.G. (Comparative Analyses of Ecosystems: Patterns, Mechanisms and Theories, 1991)

The influence of fire periodicity on habitat structure - Mushinsky, H.R.; D.J. Gibson (Habitat Complexity: The Physical Arrangement of Objects in Space, 1991)
The ecological influence of fire on the structure of a plant community varies, as fire temperature and rate of spread are neither uniform nor consistent. The manner in which a system burns depends not only on ambient temperature, windspeed, and humidity, but also on spatial distribution of fuel loads and structural variation (type, density, and height of plants) within the vegetation
Keywords: fire

Influence of illumination and surface structure on space use by prairie deer mice (Peromyscus maniculatus bairdii) - Brillhart, D.B.; D.W. Kaufman (Journal of Mammalogy, 1991)

Influence of mowing and fertilization on biomass, productivity and spectral reflectance in Bromus inermis plots - Dyer, M.I.; Turner, C.L.; Seastedt, T.R. (Ecological Applications, 1991)

Longterm ecological questions and considerations for taking longterm measurements: Lessons from the LTER and FIFE programs on tallgrass prairie - Seastedt, T.R.; J. M. Briggs (Longterm Ecological Research: An International Perspective (SCOPE Vol. 47), 1991)
The earth, with its global problems of overpopulation, over-use and abuse of fossil fuel and nuclear energy, and production of toxic wastes, has often been compared to a sick patient. Illness is recognized as a significant deviation from known, long-term trends. Long-term monitoring represents a minimal activity for responsible individuals and agencies interested in placing current environmental problems into perspective. Long-term measurements are directed at questions involving phenomena not interpretable or perhaps not useful when viewed over short (annual or less) time scales, but are related to the long-term "health" or functioning of the system. At a minimum, the Long-term Ecological Research (LTER) data therefore provide the context in which short-term observational or experimental results can be interpreted (Magnuson, 1990). A much more interesting, albeit potentially less relevant, use of LTER data involves the study of a set of complex questions that cannot be resolved with short-term studies. The juxtaposition of basic and applied science within the context of a single research effort is a strength of the LTER program. This chapter attempts to identify a set of long-term ecological questions that are useful to a national or international network of research sites. While there exists a nearly infinite list of interesting questions that could be addressed with long-term studies, a realistic and goal-oriented list of measurements is presented. The criteria for selecting these questions involved identiying variables that 1) are useful for intersite comparisons, 2) are not strongly biased by spatial scaling factors, and 3) can provide the necessary linkages between atmospheric/climatological variables and biological measurements. "Focused studies of the interactions between the atmosphere and the biosphere that regulate trace gases can improve both our understanding of terrestrial ecosystems and our ability to predict regional- and global-scale changes in atmospheric chemistry". The list of proposed variables for study was devvelpoped from the "core LTER measurements", a guideling used since the inception of the LTER effort from recommendations suggested in Earth System Science, and from practical experience with the recent NASA- ISLSCP (International Surface Land Climatology Project) conducted on the Konza Prairie LTER site. While appropriate examples are taken from many systems, particular emphasis has been given to questions that have interested researchers studying grasslands. We build on the work of Strayer et al. (1986). Their extensive overview of long-term studies provided useful definitions of research productivity, of what constitutes "long- term research", and reasons for the "successes" of previous and existing long-term research efforts. Their findings emphasized that individual scientists and not specific research protocols or experimental designs were largely responsible for successful long-term research efforts. Here, however, we suggest that certain constraints on research designs are important if a goal of the research is to benefit directly a regional or global network
Keywords: tallgrass prairie