Field measurements of alkalinity from lakes in the Uinta Mountains, Utah, 1956-1991

History and technical literature describing potential effects of livestock grazing on mule deer ( Odocoileus hemionus ) populations and winter range habitat are reviewed. Recommendations for livestock grazing on winter ranges within the Great Basin are advanced.     

Vegetal change on a northern Utah foothill range in the absence of livestock grazing between 1948 and 1982

Reexamination of a semiarid foothill rangeland, first evaluated in 1948, indicated that secondary succession continues to shift toward a perennial grass-forb community formerly dominated by xeric shrubs, particularly big sagebrush ( Artemisia tridentata spp. vaseyana ). The direct role in livestock grazing in establishment and maintenance of shrub-dominant plant communities appears confirmed in the decline of shrubs upon cessation of livestock grazing in summer and continued browsing by mule deer in winter. The reduction of shrub forages on mule deer winter ranges is a major factor in population declines.     

Vegetation changes after livestock grazing exclusion and shrub control in the southern Chihuahuan Desert

Vegetation cover and production were evaluated after nearly 7 years of livestock grazing exclusion and shrub control in an area with a long history of heavy livestock grazing in the southern Chihuahuan Desert, Mexico. An exclosure was established to prevent livestock grazing. In half of the excluded area, the main shrub, Larrea tridentata , was mechanically controlled. Outside the exclosure, heavy livestock grazing occurred as customary and shrubs were not controlled. Absence of grazing resulted in 50% higher grass cover and 35% higher total biomass. Larrea tridentata cover was twice as high on the grazed area as on the ungrazed area. Vegetation cover was dominated by grasses (42%) in the ungrazed area, whereas in the grazed area, cover was equally divided between grasses (28%) and shrubs (27%). Shrub control did not affect vegetation cover or herbage production. Multivariate analysis confirmed that inside the excluded area, shrub control had little impact on the plant community. The effect of grazing, however, clearly distinguished the community outside the exclosure from that inside the exclosure.     

Ecological review of black-tailed prairie dogs and associated species in western South Dakota

Black-tailed prairie dogs ( Cynomys ludovicianus ) once occupied extensive areas throughout the Great Plains. In recent years massive control programs have been initiated to reduce prairie dog populations, primarily to benefit the livestock grazing industry. Currently in western South Dakota most prairie dogs are found on public lands. Control programs using toxicants for prairie dogs have been found to be economically unfeasible when not combined with reductions in livestock grazing. Control programs also have negatively impacted some nontarget species of birds and small mammals. Livestock grazing is directly related to prairie dog densities. Prairie dog and livestock grazing activities are responsible for keeping plant phenological development in a suppressed vegetative stage with higher nutritional qualities that attract greater herbivore use. Prairie dog colonies create and enhance habitat for many wildlife species; in western South Dakota 134 vertebrate wildlife species have been documented on prairie dog towns. Scientific evidence strongly suggests that prairie dogs are valuable components of the prairie ecosystem. They are responsible for maintaining, creating, and regulating habitat biodiversity through soil and vegetative manipulation for a host of vertebrate and invertebrate species dependent upon prairie dog activity for their survival.     

Livestock and vegetation responses to rotational grazing in short-grass steppe

There is a paucity of information concerning livestock and vegetation responses to rotational grazing in short-grass steppe. We compared effects between 1995 and 2003 of time-controlled, short-duration rotational grazing against season-long continuous grazing, at a moderate stocking rate (1.95 ha ? animal unit month –1 ), on livestock gains and on foliar and basal cover in short-grass steppe. Livestock average daily gains, grazing-season gains, and beef production did not differ between grazing systems. We observed no relationship between precipitation (annual or growing-season) and average daily gain. In contrast, both grazing-season gains and beef production exhibited a significant curvilinear response to both growing-season and annual precipitation. Basal and foliar cover of all plant functional groups (C 3 annual grasses, C 3 perennial grasses and grass-likes, C 4 perennial grasses, cactus, annual forbs, perennial forbs, and shrubs/subshrubs) did not differ between grazing systems. Litter and bare ground were also unaffected by grazing system, with litter increasing and bare ground decreasing over the duration of this experiment. Land managers in shortgrass steppe who are implementing rotational grazing at moderate stocking rates should not expect increased livestock gains or changes in basal and foliar cover of the plant community. Rotational grazing may be a useful management tool for achieving conservation goals through modifications of seasonality and intensity of use in paddocks within larger management units to accommodate spatial variability in vegetation and temporal variation in precipitation.     

Effects of grazing exclusions on rangeland vegetation and soils, east central Idaho

Nineteen exclosures on sagebrush steppe and shadscale rangelands, varying in age from 18 to 38 years, were sampled for plant species richness, plant composition, indicators of soil erosion, ground cover, vegetative cover, and herb-low shrub layer screening cover. Features within the exclosures were compared with adjacent sites of the same size that were open to grazing by livestock and wildlife. Species richness typically was slightly greater inside exclosures than in adjacent grazed sites (median = 2 more species inside exclosures), but the difference was not significant ( P = 0.16). Similarity of plant community composition between exclosures and adjacent grazed sites ranged from 45% to 82%. Evidences of soil movement, soil pedestals, and soil flow patterns were all more pronounced outside exclosures than inside ( P ≤ 0.02), even though many sites were on flat to mild slopes (median slope = 12%). Meta-analysis of the 19 exclosure sites indicated that grazing exclusion resulted in less bare ground cover compared with adjacent grazed sites ( P ≤ 0.05). The effect of grazing exclusion on visible soil surface cryptogams was significant ( P ≤ 0.05), with generally greater cover inside exclosures. Cryptogam cover differences between grazed sites and exclosures tended to increase with the number of years of grazing exclusion ( r = 0.64, P = 0.046). Pseudoroegneria spicata , a principal livestock forage, averaged greater basal cover inside exclosures than outside on 4 of 10 sites where it occurred, although no exclosure sites had greater P. spicata cover on grazed sites. Meta-analysis of the 10 sites indicated that grazing exclusion resulted in greater P. spicata cover compared with adjacent grazed areas ( P ≤ 0.05). Poa secunda , a short-growing grass that initiates growth early in the spring and is not important livestock forage, averaged greater basal cover outside exclosures on 5 of 15 sites where it occurred. Meta-analysis of the 15 sites indicated a significant treatment effect ( P ≤ 0.05), with greater Poa secunda basal cover outside exclosures. Grazing exclusion resulted in greater screening cover in the herb-low shrub layer (0-0.5 m height; P ≤ 0.05). These results indicate that despite improved livestock grazing management over the past half century, livestock grazing still can limit the potential of native plant communities in sagebrush steppe ecosystems, and that the health of semiarid ecosystems can improve with livestock exclusion in the absence of other disturbances. A few exclosure sites were similar for the measured parameters, suggesting that these sites were ecologically stable and that exclusion of livestock grazing was not sufficient to move succession toward more pristine conditions, at least within the time periods studied. Managed disturbance such as fire or mechanical brush treatments may be necessary to restore herb productivity on these ecologically stable sites.     

Effect of Timing of Grazing on Soil-Surface Crytogamic Communities in a Great Basin Low-Shrub Desert: A Preliminary Report

Cover and species richness of vascular and cryptogamic components of the plant community were inventoried in experimental grazing paddocks at the USDA/FS Desert Range Experimental Station, Millard County, Utah. The grazing treatments considered have been applied continuously for over 50 years. The effects of heavy (ca 17 sheep days/acre) grazing treatment applied in two different seasons (early winter versus a split between early and late winter) differed significantly between seasons. Cryptogamic cover and cryptogamic species richness both showed larger decreases under early-late as opposed to early winter only grazing. Vascular plant cover (relative to controls) was also reduced by early-late winter grazing, but not to a significant degree. Late season grazing, likewise, had no significant effect on number of vascular species per transect.     

Grasshopper densities on grazed and ungrazed rangeland under drought conditions in southern Idaho

Low-density grasshopper populations were sampled at 15 pairs of rangeland sites in south central Idaho. One site of each pair had not been grazed by livestock for at least 10 years. Grazed sites were managed under normal grazing regimes established by the Bureau of Land Management. Mean grasshopper density was higher on ungrazed sites than on grazed sites. Proportions of Melanoplus sanguinipes were higher on ungrazed sites than on grazed sites and were higher on annual grasslands than on other vegetation types. Effects of grazing appeared to be independent of vegetation type. Proportions of Comhpocerinae, a subfamily of grasshoppers that feeds almost exclusively on grasses, were affected by vegetation type, but not grazing. Crested wheatgrass seedings supported the highest proportions of Gomphocerinae. Proportions of Oedipodinae were affected by grazing and vegetation type. Higher proportions of Oedipodinae were found on grazed sites than on ungrazed sites, and on sagebrush/grass sites than on annual grasslands. Results indicate that livestock grazing during drought conditions tends to reduce grasshopper populations in southern Idaho rangeland.     

Effects of livestock grazing exlosure on aquatic macroinvertebrates in a montane stream, New Mexico

Aquatic macroinvertebrate populations inhabiting reaches of a stream within areas excluded from livestock grazing for a decade were markedly different from those in grazed areas when density, biomass, biotic condition indices, and mean chi square indices of the two populations were compared. Increased densities and biomasses of more tolerant forms of macroinvertebrates were observed in grazed reaches. Because pretreatment data were not available, differences in macroinvertebrate populations and relative tolerances of taxa in grazed and ungrazed areas could be as easily attributed to linear changes in stream habitat as to removal of domestic livestock. Results of this study have implications for the design of future research on the effects of livestock grazing on stream environments and biota: (1) baseline/pretreatment information is prerequisite, and (2) the study should take a watershed (ecosystem) approach.     

Effects of horse grazing in spring on survival, recruitment, and winter injury damage of shrubs

The use of domestic grazers to shift the growth advantage toward shrubs is a commonly applied tool on winter ranges managed primarily for big game. Results from horses grazing in spring indicated grazing also benefits shrub survival, seedling recruitment, and reduced winter injury damage on some species of shrubs.     

Plant composition and erosion potential of a grazed wetland in the salmon river subbasin, Idaho

Wetlands are dynamic habitats with many unique, important functions including filtering sediments and providing diverse habitats for fish and wildlife. Wetlands in the western United States are particularly important because they offer habitat for a number of protected runs of endangered fish species. Historically, livestock grazing has altered wetland and riparian area form and function by facilitating exotic species invasions, altering spatial heterogeneity of vegetation, and increasing erosion. In this study we examined vegetation structure and erosion potential in a wetland meadow exposed to unregulated grazing along Deer Creek in the Salmon River subbasin, Idaho. We characterized the vegetation composition and structure within the study area and attempted to assess potential erosion conditions using the Revised Universal Soil Loss Equation (RUSLE), an empirical approach developed by the U.S. Department of Agriculture—Agricultural Research Service (USDA-ARS). We found no significant spatial variability in species richness and noted a moderate number of exotic species in the total plant composition. Plant cover was higher near slightly entrenched banks, indicating that uncontrolled livestock were primarily occupying gently sloped streambanks and the interior of the meadow. Based on current vegetation composition and RUSLE results, uncontrolled grazing may be negatively impacting the study area. If uncontrolled grazing were excluded or carefully managed in the wetland meadows of the upper portion of the Deer Creek watershed, a reduction in excess sediments to Deer Creek may occur.     

Response of winterfat ( Ceratoides lanata ) communities to release from grazing pressure

Sixteen study sites were established in grazed and ungrazed stands of winterfat in Kane County, Utah. The area is located within the winter range of cattle and along U.S. Highway 89 between Kanab, Utah, and Page, Arizona. Road construction in 1957 dissected several winterfat communities, and following fencing part of the communities were released from grazing. Differences in species composition, vegetation, and soil characteristics between grazed and ungrazed sites were assessed. Major differences in site characteristics appeared due to the influence of winter grazing by cattle. Winterfat and Indian ricegrass showed increased cover on the nongrazed sites following release from grazing pressure. Winterfat also showed significant negative interspecific association patterns with all major species.     

Invasion of big sagebrush ( Artemisia tridentata ) by white fir ( Abies concolor ) on the southeastern slopes of the Warner Mountains, California

White fir ( Abies concolor ) appears to be invading vegetation dominated by big sagebrush ( Artemisia tridentata ) on the southeastern slopes of the Warner Mountains of extreme northeastern California. The time of initial tree establishment within the shrubs was determined by increment borings. Possible causes of the invasion involving specific climatic conditions, fire history, and grazing use of the area during years of the establishment were explored. Heavy grazing by domestic livestock, particularly sheep, appears responsible for altering the sagebrush - grass vegetation and allowing tree invasion.     

Effects of long-term livestock grazing and habitat on understory vegetation

The herbaceous understory stratum contains most of the plant diversity in ponderosa pine ( Pinus ponderosa P. & C. Lawson var. scopulorum Engelm.) forests of the American Southwest and provides critical food and habitat for many wildlife species. During the last century, this stratum has been affected by livestock grazing and by increased dominance of overstory trees. We sampled a unique grazing exclosure to examine the relative importance of long-term livestock grazing (grazed or ungrazed) and habitat (park or tree) on the understory community. We sampled 3 plots of 192 contiguous quadrats (each quadrat 0.5 m 2 ) in each of the 4 treatment combinations, for a total of 2304 quadrats. Species-area curves were generated by aggregating quadrats into nonoverlapping areas at grain sizes of 0.5 to 576 m 2 . The effects of habitat and grazing on species density were evident at very different scales. Species density was higher in park than tree plots at scales ≤32 m 2 but did not differ between habitats at larger scales. Species density differed minimally between grazed and ungrazed treatments at small grains, but grazed plots contained more species than ungrazed plots at larger grains. Grazing treatments differed at smaller grains (to 4–8 m 2 ) than did habitats (to 32 m 2 ), with respect to density of native species and graminoids. Grazed plots had more exotic species than ungrazed plots at all grain sizes, though few exotics were present. Twenty-two species were identified as indicator species associated with habitats and/or grazing treatments. Evaluations of plant community response to treatments would be improved by accounting for the grain at which data have been collected and analyzed and by identifying indicator species associated with various treatments. These data would enable more-informed conservation and management decisions.     

Demography of Astragalus scaphoides and effects of herbivory on population growth

Losses in fecundity due to predispersal herbivory can be large; however, the effects of this loss on long-term population viability have rarely been investigated. I conducted a demographic study of Astragalus scaphoides (Fabaceae), a long-lived perennial endemic to east central Idaho and adjacent Montana, by following mapped individuals at two sites from 1986 to 1993. Astragalus scaphoides suffers losses of predispersal fecundity averaging nearly 50% from insect seed predation and inflorescence predation by insects and livestock. Cattle reduced fecundity by 0-85%. Nonetheless, estimates from matrix projection models indicate that both sample populations had positive growth in most years. Elasticity analyses revealed that population growth occurred in spite of relatively small contributions by recruitment compared to growth and survival of nonreproductive plants. Results suggest that populations of this long-lived perennial depend little on reproduction and recruitment for growth and can persist in association with seasonal-rotation livestock grazing.     

Boggy meadows, livestock grazing, and interspecific interactions: influences on the insular distribution of montane Lincoln's Sparrows ( Melospiza lincolnii alticola )

I surveyed 34 meadows in California and Oregon to count Lincoln's Sparrows ( Melospiza lincolnii alticola ) and to identify habitat features that might influence their local, insular occurrence. Lincoln's Sparrows were most common in wet meadows with little damage by grazing. Singing males were concentrated in flooded or boggy areas near meadow edges, where pines ( Pinus sp.) provided elevated perches for singing and vigilance. Patches of willows ( Salix sp.) were often present nearby. Numbers of male Lincoln's Sparrows were strongly and negatively correlated with abundance of sympatric Song Sparrows ( M. melodia fisherella ). Lincoln's Sparrows breeding in montane meadows are potentially vulnerable to local extirpation because of their insular distribution, low population density, and fluctuating habitat conditions. Heavy damage from livestock grazing drastically increases the probability of local extirpation.     

The effect of livestock grazing on the rainbow grasshopper: population differences and ecological correlates

This study examined the effect of livestock grazing on a common herbivore in semiarid grasslands of the Southwest: the rainbow grasshopper, Dactylotum variegatum . Population attributes and key environmental variables were compared between sites on active cattle ranches and sites on a 3160-ha ungrazed sanctuary. Although density of D. variegatum nymphs did not differ significantly between grazed and ungrazed sites, adult density was significantly lower on grazed sites, and sex ratios differed between grazed and ungrazed sites over time. Grazed sites had higher percentages of bare ground and fewer Baccharis pteronioides , a common shrub. However, only bare ground was highly correlated with adult D. variegatum density; lower adult densities were associated with more bare ground. At a smaller scale, D. variegatum tended to be more abundant in areas with B. pteronioides on grazed sites and less abundant in areas on ungrazed sites. This study suggests that cattle grazing influences ecological variables important in determining density, sex ratio, and spatial distribution of D. variegatum at both large and small spatial scales.     

Review of selenium in soils, plants, and animals in Nevada

Selenium is critical in livestock nutrition; forage can be either potentially deficient or toxic in this element. Selenium is accumulated in excessive amounts by a relatively few species of plants. Several of these plants, termed indicator species, occur in the western Great Basin; however, selenium toxicity is not a problem in Nevada for domestic livestock. The detection of marginal dietary deficiencies of selenium is of much greater economic importance to the livestock industry than an excess of this element. Selenium occurs as a trace element in the composition of various minerals. Selenium levels are very low in volcanic rocks of recent origin. Accumulations of this element require concentration through secondary dispersion and subsequent sedimentation. Therefore, excesses of selenium are usually associated with siltstone, sandstone, or other sedimentary rocks. Selenium is usually found in soils as selenate, a water-soluble mineral. The selenium concentration of plants is directly related to the selenate concentration in soil. In soils low in selenate, the ability of plants to accumulate selenium is similar. In soils with high levels of selenate, indicator species accumulate 10 times as much selenium as other species. The foliage of most indicator plants is generally avoided by grazing animals. Deficiencies in dietary selenium are associated with the occurrence of white muscle disease, retained placentas, and general unthriftiness of animals. Insufficient dietary selenium can be overcome through injection, intraluminal pellets, or supplementation with salt mixtures.     

Grasshopper diversity and abundance in relation to elevation and vegetation from a snapshot in Mediterranean Anatolia: role of latitudinal position in altitudinal differences

Previously described patterns of altitudinal differences in species diversity and abundance still need to be tested in respect of generality across lineages and regions. Grasshopper diversity and abundance of an altitudinal transect in the eastern Mediterranean were studied to test the generality of these patterns. To identify the reasons underlying altitudinal differences, vegetation of the study area was studied. Our data show that species diversity and abundance are highest at middle altitudes and lower at high and low altitudes for grasshoppers. This pattern is consistent with that found in many arthropod groups, but it is not consistent with the pattern reported for Orthoptera in previous studies. A cluster analysis based on the grasshopper diversity and abundance identified three distinct altitudinal zones. Possible reasons for these distinct zones were the altitudinal differences in plant composition, the precipitous nature near the summits, urbanization and grazing livestock, and the latitudinal position of the study area.