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West, Neil E

Sage-grouse (Centrocercus urophasianus and C. minimus) historically inhabited much of the sagebrush-dominated habitat of North America. Today, sage-grouse populations are declining throughout most of their range. Population dynamics of sage-grouse are marked by strong cyclic behavior. Adult survival is high, but is offset by low juvenile survival, resulting in low productivity. Habitat for sage-grouse varies strongly by life-history stage. Critical habitat components include adequate canopy cover of tall grasses (? 18 cm) and medium height shrubs (40?80 cm) for nesting, abundant forbs and insects for brood rearing, and availability of herbaceous riparian species for late-growing season foraging. Fire ecology of...
Litter production by Artemisia tridentata, Atriplex confertifolia and Ceratoides lanata plants was monitored from 1970 to 1974 in Curlew Valley, Utah. Chemical analysis of litter collected in 1971 was combined with data on total phytomass and net primary production collected in previous studies in the same area to estimate turnover rates of tissues and minerals. Litter production averaged 128.5, 175.6 and 191.9 g m-2 year-1 for the Ceratoides, Atriplex and Artemisia communities, respectively. This is much higher than would be predicted from a recently published model stressing evapotranspiration as the major driving variable. The percentages of aboveground phytomass that become litter, ranked in order, were Ceratoides...
Six study areas along an aridity gradient in Utah were investigated for effects of individual plants on modification of soil chemistry. Measurements were made of the contents of C, N and P and of pH and salinity. In one study area an ungrazed salt desert shrub site was compared with a comparable site with known grazing history. In two study areas, sites that had been tilled and converted from shrub steppe to introduced grass were compared with adjacent untilled soils. At all locations distinct soil chemical patterning was evident in both vertical and horizontal planes. Vertical concentration gradients with surface maxima are greater for C, N and P than for pH or salinity. Horizontal changes in chemical concentrations,...
A 20-year set of cover data on sagebrush semi-desert plant communities responding to wildfire and livestock grazing near Mills in central Utah provided an opportunity to compare the assumptions and adaptability of classical and state-and-transition models for describing secondary succession. Cover data were organized and analyzed by plant species, growth forms, and other ground cover classes. Graphical analysis, ordination (employing semi-strong hybrid multi-dimensional scaling), regression, and analysis-of-variance were used to determine whether the patterns observed were best described as community change (tightly linked species) or individualistic change (each species acting independently). Distinct differences...
Wind is a persistent force in arid and semiarid lands. Microphytic crusts have been attributed with the ability to reduce wind erosion because of soil binding qualities. The purpose of this research was to determine if microphytic crusts contribute to soil stability in an arid land setting. Threshold friction velocity is the wind speed necessary for the initiation of soil erosion and, thus, is a measure of soil surface stability. A portable wind tunnel was used to determine threshold friction velocity on soil surfaces consisting of microphytic crusts living and undisturbed (control), chemically killed microphytic crusts but otherwise undisturbed (chemically killed), and microphytic crusts mechanically removed from...
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