• Mechanisms that result in large herbivore grazing distribution patterns

      Bailey, D. W.; Gross, J. E.; Laca, E. A.; Rittenhouse, L. R.; Coughenour, M. B.; Swift, D. M.; Sims, P. L. (Society for Range Management, 1996-09-01)
      Grazing distribution patterns of large herbivores are affected by abiotic factors such as slope and distance to water and by biotic factors such as forage quantity and quality. Abiotic factors are the primary determinants of large-scale distribution patterns and act as constraints within which mechanisms involving biotic factors operate. Usually there is a proportional relationship between the time large herbivores spend in a plant community and the available quantity and quality of forage. This grazing pattern may result from decisions made by animals at different spatial and temporal scales. Foraging velocity decreases and intake rate increases in areas of abundant palatable forage. These non-cognitive mechanisms that occur at smaller spatial scales (bites, feeding stations, small patches) could result in observed grazing patterns. However, large herbivores also appear to select areas (patches and feeding sites) to graze. Optimal foraging models and other models assume animals use "rules of thumb" to decide where to forage. A cognitive mechanism assumes animals use spatial memory in their foraging decisions. With such abilities, large herbivores could return to nutrient-rich sites more frequently than to nutrient-poor sites. Empirical studies indicate that large herbivores have accurate spatial memories and have the ability to use spatial memory to improve foraging efficiency. Body size and perceptual abilities can constrain the choices animals can make during foraging. A conceptual model was developed to demonstrate how cognitive foraging mechanisms could work within constraints imposed by abiotic factors. Preliminary predictions of the model correspond to observed grazing patterns. Recognizing that large herbivores may use previous experiences to decide where to forage may be useful in developing new techniques to modify grazing patterns. Grazing distribution patterns appear to result from decisions and processes made at a variety of spatial and temporal scales.
    • Performance of rose clover and hairy vetch interseeded into Old World bluestem

      Volesky, J. D.; Mowrey, D. P.; Smith, G. R. (Society for Range Management, 1996-09-01)
      Old World bluestems (Bothriochloa spp.) are extensively used throughout the Southern Plains. Interseeding these stands with persistent nitrogen-fixing legumes could reduce N fertilizer input, extend the grazing season, and enhance diet quality. The objective of this study was to evaluate production and persistence of 'Overton R18' and TXR20 rose clover (Trifolium hirtum All.) and hairy vetch (Vicia villosa Roth) when interseeded into Old World bluestem. Treatments included these interseeded annual legumes and bluestem + 100 kg/ha N fertilizer. Both rose clover and vetch produced a measurable quantity of forage by early spring before bluestem began to grow. Crude protein and in vitro dry matter digestibility were higher in legume treatments when legumes were actively growing. Total season forage production was similar (6,460 kg/ha; P > 0.05) between rose clover and bluestem + N treatments except during 1991 when production under the Overton R18 treatment was less than bluestem + N or TXR20 rose clover. Average rose clover seed production (26 kg/ha) was greater than vetch (2 kg/ha; P < 0.05) resulting in greater rose clover forage compared to vetch during natural reseeding years. Rose clover plant counts 4 years after the original seeding showed an average of 22 plants/m2. Both rose clover entries appear to have excellent potential over previously available germplasm because of improved cold tolerance and the ability to produce substantial quantities of seed for natural reseeding even after close defoliation.
    • Potential of new tetraploid germplasm in Russian wildrye

      Asay, K. H.; Johnson, D. A.; Jensen, K. B.; Sarraj, W. M.; Clark, D. H. (Society for Range Management, 1996-09-01)
      Induced and natural tetraploids have been proposed as promising sources of germplasm in breeding programs to improve Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]. Studies were conducted under semiarid conditions to evaluate the potential of tetraploid (2n=4x=28) Russian wildrye germplasm recently obtained from Kazakhstan. The teraploids had significantly heavier seeds, greater seedling vigor, and they were significantly taller, and had longer and wider leaves than standard diploid (2n=2x=14) cultivars. Carbon isotope discrimination, which has been negatively correlated with water-use efficiency in cool-season grasses, was significantly lower in the tetraploid accessions than the diploid cultivars. Dry matter and seed yield of these unselected tetraploid accessions were superior to the diploid cultivar Vinall and equivalent to more recently developed diploid cultivars, Bozoisky-Select and Syn-A. In general, relative phenological development and forage quality of the tetraploid populations did not differ significantly from the diploid cultivars; however, water content, which has been associated with greater succulence, was significantly higher in the tetraploid accessions. Significant variation was found among entries within ploidy levels for most characters indicating that genetic variability is available for additional improvement through selection. Results indicate that these tetraploid accessions can be used in the development of promising breeding populations and support earlier conclusions that tetraploid germplasm should receive emphasis in future Russian wildrye breeding programs.
    • Selaginella densa reflectance: Relevance to rangeland remote sensing

      Hall-Beyer, M.; Gwyn, Q. H. J. (Society for Range Management, 1996-09-01)
      Selaginella densa Ryd. is a shallow-rooted spikemoss that grows on sparsely vegetated short and mid-grass prairie. It covers a proportion of bare soil which may rival that covered by grasses. Not a forage plant, it is treated in agronomic research as background to the edible plants. Even when it appears to the eye as dry and without active chlorophyll, its spectral reflectance resembles more closely that of forage plants than that of soil background. It is distinguishable from dense stands of chlorophyll-rich fortes and grasses using the normalized differential vegetation index, but S. densa in all cases resembles sparse grasses. Its presence must be considered when estimating range condition using remote sensing techniques.
    • Soil quality response of reestablished grasslands to mowing and burning

      Schacht, W. H.; Stubbendieck, J.; Bragg, T. B.; Smart, A. J.; Doran, J. W. (Society for Range Management, 1996-09-01)
      Prescribed burning and mowing are management practices commonly used on grasslands even though there is limited knowledge of long-term effects on soil quality. The influences of mowing and burning on soil quality were determined on 2 reestablished tallgrass sites in eastern Nebraska dominated by silty clay loam soils. Burn treatments included seasonal (i.e., October, May, or July) prescribed burning at either 1-year or 4-year intervals. Mow treatments included seasonal mowing at 4-year intervals. Both burn and mow treatments have been imposed at Site 1 since fall 1981. Only the burn treatments have been applied at Site 2 since fall 1979. Soil quality measurement were made at both sites in summer 1994. Season of application of the mow and burn treatments and season X treatment interactions were not significant. Infiltration rates at Site 1 for the mow and annual burn treatments were slower than for the control, whereas infiltration rate was comparable for the year burn treatments and the control. Unlike Site 1, the 1-year and 4-year burn treatments at Site 2 had similar infiltration rates, and the burn treatments had slower infiltration rates than the control. Generally, soil bulk density, pH, electrical conductivity, total nitrogen content, and organic matter content were similar for all treatments. Results demonstrate that repeated burning or mowing treatments can detrimentally impact infiltration rates on silty clay loam sites; however, soil properties other than those measured would need to be studied to explain infiltration response.
    • Technical Note: Spring grazing preference of wheatgrass taxa by Rocky Mountain elk

      Jones, T. A.; Urness, P. J.; Nielson, D. C. (Society for Range Management, 1996-09-01)
      We measured the grazing preference of 3 castrated male Rocky Mountain elk (Cervus elaphus nelsoni) for 2 crested (Agropyron desertorum [Fischer ex Link] Schultes), 5 thickspike (Elymus lanceolatus ssp. lanceolatus [Scribner &J.G. Smith] Gould), 3 Snake River (proposed name E. lanceolatus ssp. wawawaiensis), and 2 bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) entries. Number of bites and visits were highly correlated in early May (r2=0.77) and late May (r2=0.83). 'Critana' and 'Elbee' thickspike and 'Hycrest' and 'Nordan' crested wheatgrasses can be recommended for seedings for elk spring grazing where these grasses are adapted.
    • Viewpoint: Concept design in range management science

      Scarnecchia, D. L. (Society for Range Management, 1996-09-01)
      This paper is an analysis of general principles involved in designing concepts for range science. It discusses the diversity of conceptuality in range science, from dimensional units to variables to simple models to more complex decision-aiding models. It examines how considerations of abstraction, confounding, and generalization allow development of multi-objective concepts needed in a range management science of many variable, interactions, and models. Examples related to each principle are provided. The paper discusses the importance of avoiding internal confounding within concepts and the necessity that such confounding be avoided in order to allow clear analyses. Ad hoc indices are characterized as inadequate substitutes for explicit models of more complex concepts such as preference and diet selection. Design efforts emphasizing multiple objectives will produce concepts of general use in range management science.