Central Plains Experimental Range Research Articles

Methamidophos Application Effects on Pasimachus elongatus (Coleoptera: Carabidae): An Update

Population densities of a predatory ground beetle, Pasimachus elongatus LeConte (Coleoptera: Carabidae), were examined at the Central Plains Experimental Range, Colorado. Using distance sampling theory, I analyzed density estimates dating from before an application of the insecticide methamidophos (1988) and three beetle generations afterward (1994) to address the following questions. Have population densities of P. elongatus recovered to prespray levels? Are current population densities of P. elongatus in areas exposed to methamidophos in 1988 equal to those not exposed in 1988? How do population densities of P. elongatus vary with habitat type in methamidophos exposed and nonexposed areas? This work updates earlier findings that P. elongatus population densities decreased after methamidophos applications. Lingering differences in P. elongatus densities were found among areas differing in methamidophos exposure; these differences were also related to habitat type. Higher population densities were found in methamidophos exposed than in control areas; higher densities were also found in shrub dominated than in grass dominated sites, regardless of past methamidophos exposure. Because potential prey species were found to be equally abundant in methamidophos exposed and nonexposed areas despite the greater abundance of the carnivorous Pasimachus in treatment areas, the P. elongatus density patterns seen are discussed in relation to possible long-term disruption of the arthropod prey community by methamidophos. Other explanations for the observed patterns (including competitive release and physiological resistance) are also discussed.

The response of mycorrhizal colonization to elevated CO2 and climate change in Pascopyrum smithii and Bouteloua gracilis

Large intact soil cores of nearly pure stands of Pascopyrum smithii (western wheatgrass, C3) and Bouteloua gracilis (blue grama, C4) were extracted from the Central Plains Experimental Range in northeastern Colorado, USA and transferred to controlled environment chambers. Cores were exposed to a variety of water, temperature and CO2 regimes for a total of four annual growth cycles. Root subsamples were harvested after the completion of the second and fourth growth cycles at a time corresponding to late winter, and were examined microscopically for the presence of mycorrhizae. After two growth cycles in the growth chambers, 54% of the root length was colonized in P. smithii, compared to 35% in blue grama. Field control plants had significantly lower colonization. Elevation of CO2 increased mycorrhizal colonization in B. gracilis by 46% but had no effect in P. smithii. Temperatures 4° C higher than normal decreased colonization in P. smithii by 15%. Increased annual precipitation decreased colonization in both species. Simulated climate change conditions of elevated CO2, elevated temperature and lowered precipitation decreased colonization in P. smithii but had less effect on B. gracilis. After four growth cycles in P. smithii, trends of treatments remained similar, but overall colonization rate decreased.

Evaluating landsat thematic mapper derived vegetation indices for estimating above-ground biomass on semiarid rangelands

Ground data from the Central Plains Experimental Range in northeast Colorado and Landsat satellite images of that area acquired in August 1989, June 1990, and September 1990 were used to evaluate the level of association that can be expected from a univariate model relating spectrally derived vegetation indices (difference, ratio, and normalized difference vegetation indices) and dried green vegetation biomass. The vegetation indices were related to the ground sample estimates using a sample point, spectral class, and greenness strata approach. No strong relationships were found between the vegetation indices and sample estimates of dried green biomass using the sample point approach. The spectral class approach produced significant results only for the June 1990 sample period ( r=0.96). Significant relationships were found for the August 1989, June 1990, and September 1990 samples periods ( r 2=0.95, 0.71, and 0.95, respectively) when the data were aggregated by greenness strata. The high degree of association between green biomass and the NDVI, obtained when the data were combined into greenness strata, indicated that it is possible to predict green biomass levels on semiarid rangelands using univariate regression models.

What do LTER results mean? Extrapolating from site to region and decade to century

Abstract Although most ecological studies have been conducted at individual sites and over short time intervals, there is an increasing need to study and make predictions about how regions will change over relatively long periods. Such work requires that results be extrapolated beyond the bounds of an individual site. In this paper, we evaluated the extent to which the Central Plains Experimental Range (CPER) Long-Term Ecological Research (LTER) site may be considered to represent the shortgrass steppe of the central Great Plains. We identified the major controls over shortgrass steppe ecosystem structure and function as precipitation, temperature, soil texture and landuse, and determined the distribution of those variables for the CPER. We developed a geographic database of the four major control variables for a region comprising the central Great Plains and adjacent Central Lowlands, and compared the CPER to the region with respect to these variables. We found that the CPER could be considered to represent 18.6% of the shortgrass steppe within the central Great Plains, or 5.8% of the central Great Plains, with respect to key ecosystem controls. Although an individual site may represent a relatively small proportion of a region, results from a site or network of sites may be extrapolated in time and space through application of simulation models to regional spatial databases.

SPATIAL VARIABILITY IN SEED PRODUCTION OF THE PERENNIAL BUNCHGRASS BOUTELOUA GRACILIS (GRAMINEAE)

The effects of soil texture and grazing by cattle on the production of seeds of Bouteloua gracilis were evaluated for a semiarid grassland in northeastern Colorado. Ten locations were chosen to represent the range in soil textures and grazing intensities found at the Central Plains Experimental Range research site. Number of flowering culms, inflorescences and seeds, length of each flowering culm, total biomass of reproductive structures (culms, inflorescences, and seeds), and basal area were assessed for 96 B. gracilis plants at each location. Community‐level estimates of density of flowering culms and density of viable seeds were made for each location. Both soil texture and grazing by cattle were important to spatial variability in seed production and other indicators of reproductive effort by B. gracilis. Grazing was important in mediating effects of soil texture. On locations protected from grazing, soil texture had significant effects on seed production; the largest number of seeds was produced on the coarsest‐textured soil and the fewest number on the finest‐textured soil. Relationships between seed production and clay content and between seed production and other indicators of reproductive effort by B. gracilis were different for grazed and ungrazed locations. Spatial variability in seed production of B. gracilis as a result of spatial variability in soil texture and grazing may be important to the continued dominance of this species in the presence of disturbances that vary in time and space.

A gap dynamics simulation model of succession in a semiarid grassland

We applied a gap dynamics conceptualization of succession to a semiarid grassland by focusing on gaps produced in the belowground resource space by death of an individual of the dominant species, the perennial grass blue grama ( Bouteloua gracilis (H.B.K.) Lag. ex Griffiths). We developed a gap dynamics simulation model to examine long-term successional dynamics on gaps, time required for B. gracilis to recolonize gaps, and spatial variability of gap dynamics at the scale of the landscape. The model is similar to gap models used in forest, but is based on belowground resource use and life history characteristics of plants in shortgrass communities, and incorporates effects of small-scale disturbances and stochastic environmental factors. Average time required for B. gracilis to dominate biomass on a simulated plot was 20 years, a more rapid recovery time than has been reported from experimental studies of large-scale disturbances. Our initial simulations assumed the only control on establishment of B. gracilis seedlings was the occurrence of a restrictive set of microenvironmental conditions. A second set of simulations incorporating effects of seed availability resulted in an average recovery time of 65 years. The scale dependence of successional processes important to recruitment of B. gracilis plants is indicated since this is still a faster recovery time than was observed experimentally. Aboveground biomass on the simulated plots was dominated by B. gracilis through time and space. Relative proportion of aboveground biomass and average biomass values for each species were comparable to the composition of shortgrass plant communities at the Central Plains Experimental Range study site in northcentral Colorado. This initial analysis suggests that gap processes are important to shortgrass communities, and that a gap dynamics conceptualization based on the importance of small, frequently occurring disturbances is a promising alternative to the previous conceptual model of shortgrass communities based on effects of large-scale disturbances.

Biomass dynamics and water use efficiencies of five plant communities in the shortgrass steppe.

Standing crop biomass and water-use efficiency were estimated for five plant communities of the Central Plains Experimental Range in north central Colorado. Aboveground biomass by functional groups, surface litter amounts, and standing dead biomass were compared, as were vertical and size-class distributions of belowground biomass. Greater production and water-use efficiency values were found: (1) at coarse-textured sites, indicating the importance of the inverse texture effect, and (2) wherever site characteristics favored the establishment of lifeforms other than grasses, e.g., succulents, and shrubs. Seasonal aboveground biomass and water-use efficiencies for the grass component were similar among sites, even though the mixes of C3 and C4 grass species were different. Similar grass biomass values in very different communities suggested that high biomass and high water-use efficiencies were related less to grass types than to the abundance of non-grass life-forms.

Effects of Hay and Straw Mulches on the Establishment of Seeded Grasses and Legumes on Rangeland and a Coal Strip Mine

Straw and grass-hay mulches at rates of 1,120 and 3,360 kg/ha were applied to the surface after seeding or incorporated into the soil before seeding for 3 consecutive years of planting at Central Plains Experimental Range (CPER) near Nunn, Colorado, and at Colorado Yampa Coal Company mine (CYCC) near Steamboat Springs, Colorado. Averaged across 3 years, the stand ratings of Psathyrostachysjuncea (Fisch.) Neveski, the only species seeded at CPER, were significantly better for the check (no mulch) treatment than for any mulch treatment. At CYCC, average stand ratings were significantly better than the check when 1,120 kg/ha of straw mulch was applied to the surface after seeding. The species that consistently had the best stand ratings at CYCC were Astragalus cicer L.,Bromus biebersteinii Roem and Schult.,B. inermis Leyss., B. marginatus Nees, Elytrigia intermedia (Host) Nevski, E. intermedia subsp. barbulato (Schur) A. Live, Medicagofalcata L., M. sativa L., and Phleum pratense L. No erosion from the plots by either wind or water was observed regardless of mulch treatments.

Standardized meteorological measurements for LTER sites

Standards have been established for meteorological measurements at Long‐Term Ecological Research (LTER) Sites. The LTER program is designed to allow for coherence in research over the long term and to recognize that many parts of ecosystems operate over a long time scale and show directionality and periodicity in ecosystems. The following LTER sites are funded in 5‐year renewable funding periods and overseen by a central coordinating committee, consisting of the principal investigators for all sites, that supplies normal National Science Foundation peer review procedures: H. J. Andrews Experimental Forest, Oreg.; Cedar Creek Natural History Area, Minn.; Central Plains Experimental Range, Colo.; Coweeta Hydrological Laboratory, N.C.; Illinois and Mississippi Rivers, Ill.; Jornada Experimental Range, N. Mex.; Konza Prairie, Kans.; Niwot Ridge/Green Lakes Valley, Colo.; North Inlet, S.C.; Northern Lakes, Wis.; Okefenokee Natural Wildlife Refuge, Ga.

Simplified Simulation Model of the Plant Producer Function in Shortgrass Steppe

Models of grassland ecosystems generally have been either simple regression equations for certain processes or large complex simulation models consisting of numerous integrated sets of equations. The former do not account explicitly for interacting mechanisms and the latter are expensive and, because of their complexity, may be difficult to interpret. This paper presents a simple, 11-equation simulation model of the primary producer function in the shortgrass steppe. Model results closely approximate observed data from the Central Plains Experimental Range in northeastern Colorado. INTRODUCTION The U. S. Forest Service has the responsibility for managing vast areas of forests and grasslands. Developing comprehensive plans for these management responsibilities requires predictions about how these ecosystem types will respond to alternative management strategies (Joyce et. al., 1983). These plans must account for heterogeneous landscape units and be able to evaluate how management affects individual vegetation types within these units. Ecologists and managers are interested if generic models can be constructed for vegetation types such that these models will produce the required level of descriptive accuracy to be used in planning. In this paper we describe a grassland model designed to project realistic grassland responses to management practices, such as irrigation, fertilization and changes in the grazing regime. The resulting model is not intended to address detailed ecological questions, but rather, to provide general estimates of primary production over relatively wide geographical areas. Furthermore, the model is simple enough so that the equations capture the important ecological and physiological processes, but the model output is designed to be conveniently interpreted in relation to practical decisions about natural resource management options. During the past two decades, numerous mathematical models have been designed to simulate the essential characteristics and behavior of grassland ecosystems. These models have addressed various objectives, e. g, providing a format for improving understanding about ecosystems, providing a tool for communicating information, suggesting further experimental research, and improving management of grasslands. Many of the earlier mathematical models of grassland productivity were regression models or algebraic equations that fit patterns of observed data (Clayton et. al., 1983; Sneva and Hyder, 1962; Sims et al., 1978). Subsequently, some grassland models became very complex, consisting of hundreds of interrelated equations (e.g, Innis, 1978). While these complex models have proved useful for understanding grasslands (Parton and Risser, 1980; Risser et al., 1981; Risser and Parton, 1982), their size and complexity have made them expensive to run and, in some cases, difficult to evaluate. Therefore, the model described in this paper was designed to be relatively simple and to use independent driving variables that are easily measured.

Cattle Diets on Shortgrass Ranges with Different Amounts of Fourwing Saltbush

Cattle Diets on Shortgrass Ranges with Different Amounts of Fourwing Saltbush

Soil-Plant Factors in Early Browning of Russian Wildrye on Natrustoll Soils

The occurrence of early browning in selected areas of a 1979established Russian wlldrye (Elymus jwrceus Fisch.) plot led to a comparison of soil-plant-water relationships in the brown senescing areas, and in adjacent green healthy areas. Although the green areas exhibited better nutrient status and less salinity-sodicity associated problems than the brown areas, the main problem and cause for this premature browning appeared to be water related. A main objective of the rehabilitation program of the saltgrass meadows soils at the Central Plains Experimental Range (CPER) is to replace the largely unpalatable inland saltgrass [Distichlis stricta (Torr.) Rydb.] with better forage grasses and legumes for livestock consumption. These improved forages must be tolerant to drought stress and at the same time tolerant to saline-sodic soil conditions (McGinnies et al. 1976). Russian wildrye (Elymus junceus Fisch.) is one such species which is presently being used at the CPER to replace inland saltgrass. For 2 consecutive seasons (1980,198l) early browning has been noted in certain areas of a 1979established Russian wildrye plot (40 m X 6 m). These brown areas varied from entire sub-plots (5 m X 6 m) to parts of a sub-plot (1 m X 0.5 m). In 1981, we sampled 2 contrasting areas to assess soil and plant characteristics of both areas. Methods and Materials

Soil Bulk Density as Influenced by Grazing Intensity and Soil Type on a Shortgrass Prairie Site

Soil Bulk Density as Influenced by Grazing Intensity and Soil Type on a Shortgrass Prairie Site

Cooing Activity and Nesting of Mourning Doves in Northeastern Colorado

Cooing Activity and Nesting of Mourning Doves in Northeastern Colorado

Viable grass seeds in herbivore dung from a semi‐arid grassland

AbstractFaeces of cattle, pronghorn and rabbit were collected from the Central Plains Experimental Range, Colorado, 6, 18 and 30 months after being excreted. The faecal material was placed in moistened potting soil and seedling emergence observed. Bouteloua gracilis (blue grama grass) and Sporobolus cryptandrus (sand drop seed), emerged in abundance from cattle dung. Emergence of B. gracilis decreased with increasing period of exposure before collection, but emergence of S. cryptandrus increased with exposure. Forbs dominated the seedling populations in pronghorn dung, and few seedling populations of any species emerged from rabbit dung. The results are discussed in relation to the effect of large herbivores on the establishment of species from seed in rangeland.

Chemical Transformations of Urea‐Nitrogen and Movement of Nitrogen in a Shortgrass Prairie Soil

AbstractThis study, conducted on the Central Plains Experimental Range during the summer of 1979, was to (i) quantify the temporal dynamics of the transformations of nitrogen (N) in a simulated urine spot, (ii) determine the effect of urea hydrolysis on pH, and (iii) determine the depth of movement of nitrate by leaching. Miniplots of blue grama were established, and open‐ended aluminum cylinders 10 cm in diameter and 40 cm in length were embedded in each plot. Simulated urine was applied to two‐thirds of the plots at a rate of up to 45 g N m−2. The remaining plots were controls.After the simulated urine application, only 6% of the added N remained as urea at 2 days; no urea‐N remained at 4 days. Maximum accumulation of ammonium‐N (39.9 g N m−2) was simultaneous with the disappearance of urea. Elevated levels of nitrate were first detected at day 12 when 6.7 g N m−2 had accumulated. No measurable nitrite accumulated during the experiment.Through the first 4 days, 83% of the (urea + ammonium)‐N in the profile was in the top 15cm of the soil. With the rains near the end of the study, nitrification proceeded, and nitrate was leached through the profile to below the depth of the cores.Simulated urine significantly affected soil pH to 15 cm. From an initial pH near 6.0, urea hydrolysis increased soil pH from 0.6 to 1.3 units. As nitrification prodeeded after day 40, the pH decreased to below control levels.

Blacktail Prairie Dogs, Desert Cottontails and Cattle Trophic Relations on Shortgrass Range

Highlight: The trophic relations among blacktail prairie dogs, desert cottontails, and cattle were determined among three dogtowns at the Central Plains Experimental Range near Nunn, Colo. Sedges were the most important food of prairie dogs and cottontails and the second most important food of cattle on an annual basis. There was a high percentage similarity in the diets of the three herbivores studied; and they cDnsumed large percentages of sedges and grass. The amount of aboveground herbage eaten and made unavailable because of soil disturbances by prairie dogs and cottontails was about 24% of the total potential annual production.

Analysis and structure of four lentic communities on the Colorado (U.S.A.) shortgrass prairie

AbstractFour natural lentic habitats on the Central Plains Experimental Range in Colorado were intensively studied physically, chemically, and biologically for 2 yr (1968–1970) and intermittently for 5 (1971–1975). Lynn Lake and Lake George were chosen as examples of ephemeral or temporary sites, while Cottonwood Pond and Spring Pond were chosen as permanent habitats. Chemically, the waters of each site were analytically separated into dissolved and suspended (sestonic) components. The temporary sites were characterized by their exceptionally high seston loads, the presence of Eubranchiopoda, the prevalence of Ca as the major dissolved cation, ana the high Fe content of their sediments. The two permanent sites, on the other hand, had high total dissolved salt content, rich and varied flora and fauna, Na as the prevalent cation in the dissolved fraction, and high Ca content in the sediments. All four of the sites were “seston digesters” with large amounts of wind‐blown organic material being entrapped, decomposed, and mineralized. By comparison with adjacent soils the sediments of all four basins were much richer in K, Zn, Fe, Cu, and Mn. Both temporary and permanent sites function as nutrient sinks. Rates of daily and annual phytoplankton primary productivity are reported for the two permanent sites.

Phenological Pattern in the Shortgrass Prairie

Data were collected for 1 year on 34 range plant species and for 2 years on six species to describe phenological timing in the shortgrass prairie of northeastern Colorado and also to determine whether there were any distinct groups of plants for which a single species could be used as a phenological indicator. Observations were made in four grazing treatments and two water amendment areas (one with 100 kg/ha mineral N ad'ded). Water amendments altered the phenology of some species, while grazing and nitrogen treatments had no measurable effects on phenology. Standard cooland warm-season classification of plants does not adequately describe the phenological dynamics of the shortgrass prairie. For example, Buchloe dactyloides, a warm-season grass, flowers with Agropyron smithii, a cool-season grass, rather than with Bouteloua gracilis, another warm-season grass. Four general categories of plants having different flowering capacities are recognized: blooming only once very early in the growing season; blooming twice with a summer dormancy period; blooming once during midsummer with blooming delayed during drought; and blooming only once late in the growing season. INTRODUCTION An understanding of phenological progression of plants is basic to understanding the functioning of a grassland ecosystem and is important in sound resource management (Costello, 1939; Lieth and Radford, 1971). Phenology is associated with plant growth rates (Taylor, 1972), nutrient transfer (Sosebee and Wiebe, 1973), thermal requirements (Nuttonson, 1955), plant-water relationships (Blaisdell, 1958) and perhaps even evolutionary change (Leopold, 1961). The objectives of this study were: (1) to describe the phenological progression of a broad spectrum of shortgrass prairie species; (2) to develop an approach for monitoring the phenological progress of the shortgrass prairie plant community by observing a few indicator species, and (3) to compare water treatment and annual weather variation effects as well as any observable differences in phenological state between grazing treatments or fertilization. These measurements, when combined with abiotic and other biotic measurements, will lead to a clearer understanding of the structure and function of the shortgrass prairie ecosystem. SiTE DESCRIPTION The Pawnee Site (intensive research site of the US/IBP Grassland Biome) ig located on the western edge of the USDA Central Plains Experimental Range, approximately 12 km N of Nunn, Colorado, at an elevation of 1652 m. Topography is gentle rolling plains. The major soil types are Ascalon, Vona, Renohill and Shingle, with Ascalon predominating on the sampling areas (Reuss, 1971). Annual precipitation varies from 254 to 381 mm, about 80% occurring from May to

Vegetation Changes Induced by Prairie Dogs on Shortgrass Range

Highlight: This study documented some effects of prairie dogs on a shortgrass type of the Central Plains Experimental Range approximately 35 miles northeast of Fort Collins, Colo., and an adjacent area. Prairie dogs changed the plant species composition of the two sites studied, but these changes were not all detrimental. Species diversity was greater and some plant species used by livestock were more abundant inside than outside the prairie dog towns.