Black Sagebrush Research Articles

Passive restoration of vegetation and biological soil crusts following 80 years of exclusion from grazing across the Great Basin

Restoration targets for biological soil crusts are largely unknown. We surveyed seven 80‐year‐old grazing exclosures across northern Nevada for biocrusts to quantify reference conditions at relatively undisturbed sites. Exclosures were associated with the following plant communities: Wyoming big sagebrush, black sagebrush, and areas co‐dominated by winterfat and Wyoming big sagebrush. Cover of biocrusts and shrubs were generally higher than other plant groups at these sites, regardless of being inside or outside of the exclosures, suggesting these groups make up most of the native flora across the region. Important in forming soil structure, cyanobacteria of the order Oscillatoriales were less abundant and diverse in black sagebrush communities. Grazing had a negative effect on the abundance of Oscillatoriales but not the number of algal taxa, including cyanobacteria. Abundance of light algal crusts were not influenced by plant community or grazing. Dark algal crusts were generally less abundant on grazed sites. Influences of plant community and grazing were most apparent when accounting for reproductive rates of lichens and mosses based on establishment mechanisms. Abundance of shrubs, perennial grasses, Oscillatoriales, fast reproducing biocrusts and the number of algal and cyanobacterial taxa, varied by plant community, suggesting that restoration should be plant community specific. We demonstrate the affinity of rapidly reproducing biocrusts for winterfat‐Wyoming big sagebrush co‐dominated plant communities, regardless of grazing pressure. Across sites, the effects of grazing were most evident on the abundance of Oscillatoriales and slowly reproducing biocrusts following 80 years of cessation from grazing.

Climatic Influences on Establishment Pulses of Four Artemisia Species in Nevada

Shrub recruitment in arid and semiarid regions often occurs in pulses controlled by specific weather events. Previous research suggested that Wyoming sagebrush in Wyoming is no exception. We examined four species/subspecies of sagebrush in Nevada, in 2009 and 2010, to discover if evidence of recruitment pulses was contained in the annual growth-ring records. Sagebrush species and subspecies occur on a wide variety of ecological sites that require different management strategies. Species included black sagebrush (Artemisia nova A. Nelson), Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis Beetle & Young), Lahontan sagebrush (Artemisia arbuscula subsp. longicaulis Winward & McArthur), and low sagebrush (Artemisia arbuscula Nutt. ssp. arbuscula). Eighty stem sections were collected from each of 24 stands (6 stands per species or subspecies) at different geographic locations along east-west or north-south gradients where each species or subspecies naturally occurred. Annual growth-ring analysis was used to determine the year of establishment and the relationship between recruitment and weather events. Results indicated stand ages and locations were different (P > 0.001) among species and subspecies, and years of recruitment were strongly correlated with local and hemispheric weather patterns. Linear and multiple regressions modeled recruitment pulses for all four species. Weather-based predictor variables indicated complex interactions between recruitment and climatic controls. Pacific Decadal Oscillation (PDO) index variables were prominent predictors for all four species at their associated sites. Other important local weather variables included total annual precipitation the year before recruitment, the year of recruitment, and the year following recruitment. In Nevada and the Great Basin, it is imperative that successful sagebrush seeding technologies are discovered and implemented. Ecological restoration and postfire rehabilitation methods should be timed correctly with respect to precipitation patterns (positive phase PDO) and/or designed to mimic conditions responsible for natural sagebrush recruitment.

Distribution and Habitat of Ixodes pacificus (Acari: Ixodidae) and Prevalence of Borrelia burgdorferi in Utah.

Knowledge about the distribution and abundance of the western black-legged tick, Ixodes pacificus Cooley and Kohls, in Utah is limited. Recent concerns over tick-borne diseases in Utah, primarily Lyme disease, have reinvigorated the need to understand the distribution and habitats favored by this tick species. We surveyed 157 sites throughout Utah to examine the distribution, abundance, and habitat of I. pacificus. In total, 343 adult ticks were collected from 2011 to 2013. Specifically, 119 I. pacificus, 217 Dermacentor andersoni Stiles, six D. albipictus Packard, and one D. hunteri Bishopp were collected. Overall, tick abundance was relatively low in the areas evaluated in Utah. I. pacificus collections were limited to sites above 1700 m. Ninety-two percent of I. pacificus were captured in the Sheeprock Mountains in Tooele County. I. pacificus positive collection sites were characterized by Gambel oak (Quercus gambelii Nuttall), juniper (Juniperus spp. L.), big sagebrush (Artemisia tridentata Nuttall) and black sagebrush (A. nova Nelson), and mixed grass habitat. All I. pacificus ticks were tested for the presence of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner, sensu stricto) using real-time PCR. All ticks tested negative for B. burgdorferi. The likelihood of encountering I. pacificus and acquiring Lyme disease in the areas evaluated in Utah is considerably low due to low tick abundance and limited distribution, as well as low prevalence (or absence) of B. burgdorferi in Utah.

Vegetation Responses to Pinyon–Juniper Treatments in Eastern Nevada

Comparisons of tree-removal treatments to reduce the cover of single-leaf pinyon (Pinus monophylla Torr. and Frém.) and Utah juniper (Juniperus osteosperma [Torr.] Little), and subsequently increase native herbaceous cover in black sagebrush (Artemisia nova A. Nelson), are needed to identify most cost-effective methods. Two adjacent vegetation management experiments were initiated in 2006 and monitored until 2010 in eastern Nevada to compare the costs and efficacy of various tree reduction methods. One Department of Energy (DOE) experiment compared a control to five treatments: bulldozing imitating chaining ($205 · ha-1), lop-pile-burn ($2 309 · ha-1), lop-and-scatter ($1 297 · ha-1), feller-buncher and chipper ($4 940 · ha-1), and mastication ($1 136 · ha-1), whereas a second Bureau of Land Management (BLM) experiment compared one-way chaining ($205 · ha-1) to a control treatment. Chaining and bulldozing resulted in the least reduction of tree cover among the treatments. In the DOE experiment, forb cover only decreased in the mastication treatment. Litter increased in all methods. Slash cover was lowest in the control and lop-pile-burn treatments, intermediate in the feller-buncher and mastication treatments, and highest in the bulldozing and lop-and-scatter treatments. By 2010, forb cover and the combined cover of dead shrubs and trees were increased and decreased, respectively, by chaining in the BLM experiment. Nonnative annual grass and biotic crust were absent or uncommon before and after treatment implementation. In both experiments, tree removal resulted in a nonsignificant increase in perennial grass cover even 4 yr post-treatment. An ecological return-on-investment (EROI) metric was developed to compare perennial grass cover and tree cover per unit area cost of each active treatment. By 2010, chaining or bulldozing, followed by mastication, showed the highest EROI for improving perennial grass and decreasing tree cover. Mastication is recommended for restoration of smaller tree-encroached areas, whereas land managers should reconsider smooth chaining, despite its negative perceptions, for rapid and cost-efficient restoration of large landscapes obligates.

Twentieth century carbon stock changes related to Piñon-Juniper expansion into a black sagebrush community

BackgroundIncreases in the spatial extent and density of woody plants relative to herbaceous species have been observed across many ecosystems. These changes can have large effects on ecosystem carbon stocks and therefore are of interest for regional and national carbon inventories and for potential carbon sequestration or management activities. However, it is challenging to estimate the effect of woody plant encroachment on carbon because aboveground carbon stocks are very heterogeneous spatially and belowground carbon stocks exhibit complex and variable responses to changing plant cover. As a result, estimates of carbon stock changes with woody plant cover remain highly uncertain. In this study, we use a combination of plot- and remote sensing-based techniques to estimate the carbon impacts of piñon and juniper (PJ) encroachment in SE Utah across a variety of spatial scales with a specific focus on the role of spatial heterogeneity in carbon estimates.ResultsAt a plot scale (300 m2) areas piñon juniper (PJ) encroached areas had 0.26 kg C m-2 less understory vegetation carbon compared to un-encroached sites. This lower amount of carbon was offset by an average of 1.82 kg C m-2 higher carbon in PJ vegetation and 0.50 kg m-2 of C in PJ surface-litter carbon. Soil mineral carbon stocks were unaffected by woody plant cover and density. Aboveground carbon stocks were highly dependent on PJ vegetation density. At a 300 m2 plot-scale, plots with low and high density of PJ forest had 1.40 kg C m-2 and 3.69 kg m-2 more carbon than the un-encroached plot. To examine how these 300 m2 variations influence landscape scale C estimates, historical and contemporary aerial photos were analyzed to develop forest density maps in order to estimate above ground PJ associated C stock changes in a 25 ha area. This technique yielded an average estimate of 1.43 kg m-2 of C accumulation with PJ encroachment. Combining this estimate with analysis of tree growth increments from dendrochronologies, we estimate that these PJ stands are accumulating aboveground C at an annual rate of 0.02 kg C m-2 with no slowing of this rate in healthy PJ. This result is in contrast to what has been observed in large areas of drought related PJ mortality, where C accumulation has ceased.ConclusionsThese results illustrate that the encroachment of PJ forests in SE Utah over the last century has resulted in a large (and ongoing) accumulation of carbon in PJ trees and surface litter. However, the magnitude of the increase depends to on the density of vegetation across the landscape and the health of forest stands. Both management activities that remove forest carbon and forest mortality due to drought or wildfire have the potential to quickly reverse the multi-decadal accumulation of carbon in these stands.

Phytochemistry predicts habitat selection by an avian herbivore at multiple spatial scales

Animal habitat selection is a process that functions at multiple, hierarchically. structured spatial scales. Thus multi-scale analyses should be the basis for inferences about factors driving the habitat selection process. Vertebrate herbivores forage selectively on the basis of phytochemistry, but few studies have investigated the influence of selective foraging (i.e., fine-scale habitat selection) on habitat selection at larger scales. We tested the hypothesis that phytochemistry is integral to the habitat selection process for vertebrate herbivores. We predicted that habitats selected at three spatial scales would be characterized by higher nutrient concentrations and lower concentrations of plant secondary metabolites (PSMs) than unused habitats. We used the Greater Sage-Grouse (Centrocercus urophasianus), an avian herbivore with a seasonally specialized diet of sagebrush, to test our hypothesis. Sage-Grouse selected a habitat type (black sagebrush, Artemisia nova) with lower PSM concentrations than the alternative (Wyoming big sagebrush, A. tridentata wyomingensis). Within black sagebrush habitat, Sage-Grouse selected patches and individual plants within those patches that were higher in nutrient concentrations and lower in PSM concentrations than those not used. Our results provide the first evidence for multi-scale habitat selection by an avian herbivore on the basis of phytochemistry, and they suggest that phytochemistry may be a fundamental driver of habitat selection for vertebrate herbivores.

Using gas chromatography to determine winter diets of greater sage‐grouse in Utah

AbstractSagebrush (Artemisia spp.) constitutes the majority (>99%) of sage‐grouse (Centrocercus spp.) winter diets. Thus, identification and protection of important winter habitats is a conservation priority. However, not all sagebrush may be alike. More information is needed regarding sage‐grouse sagebrush winter dietary preferences for application to management. The objective of our research was to determine if chemical analysis of fecal pellets could be used to characterize winter sage‐grouse diets as a substitute for more invasive methods. We collected and analyzed fecal pellets and sagebrush samples from 29 different sage‐grouse flock locations in northwestern and southcentral Utah. Using gas chromatography, we were able to identify crude terpene profiles that were unique to Wyoming sagebrush (A. tridentata wyomingensis) and black sagebrush (A. nova). We subsequently used the profiles to determine sagebrush composition of sage‐grouse fecal pellets, thus reflecting sage‐grouse winter diets. This technique provides managers with a tool to determine which species or subspecies of sagebrush may be important in the winter diets of sage‐grouse populations. © 2011 The Wildlife Society.

Survival and detectability bias of avian fence collision surveys in sagebrush steppe

AbstractWe used female ring‐necked pheasant (Phasianus colchicus) carcasses as surrogates for greater sage‐grouse (Centrocercus urophasianus) to study factors influencing survival and detection bias associated with avian fence collision surveys in southern Idaho, USA, during spring 2009. We randomly placed 50 pheasant carcasses on each of 2 study areas, estimated detection probability during fence‐line surveys, and monitored survival and retention of carcasses and their associated sign over a 31‐day period. Survival modeling suggested site and habitat features had little impact on carcass survival, and constant survival models were most supported by the data. Model averaged carcass daily survival probability was low on both study areas and ranged from 0.776 to 0.812. Survival of all carcass sign varied strongly by location, and the top sign survival model included a site effect parameter. Model averaged daily survival probability for collision sign on the 2 study sites ranged from 0.863 to 0.988 and varied between sites. Logistic regression modeling indicated detection probability of carcasses during fence‐line surveys for avian collision victims was influenced by habitat type and microsite shrub height at the carcass location. Carcasses located in big sagebrush (Artemisia tridentata) habitats were detected at a lower rate (0.36) than carcasses in little (A. arbuscula) and black sagebrush (A. nova) habitats (0.71). Increasing shrub height at the carcass location from the little sagebrush mean of 16.5 cm to the big sagebrush mean of 36.0 cm reduced detection probability by approximately 30%. Avian fence collision surveys in sagebrush‐steppe habitats should be conducted at ≤2‐week sampling intervals to reduce the impact of survival bias on collision rate estimates. Two‐week sampling intervals may be too long in areas with low carcass and sign survival, therefore survival rates should be estimated on all study areas to determine the appropriate sampling interval duration. Researchers should be aware of the effects of local vegetation on detection probabilities, and methods to correct detection probabilities based on collision site attributes should be applied to ensure more accurate collision rate estimates. Additionally, caution should be used when aggregating or comparing uncorrected collision data from areas with differing vegetation, as detection probabilities are likely different between sites. © 2011 The Wildlife Society.

Cheatgrass Invasion in Salt Desert Shrublands: Benefits of Postfire Reclamation

Abstract In 1998, fires burned more than 11 330 ha of rangeland on Dugway Proving Ground in Utah's west desert. Postfire revegetation was implemented in 2 affected salt desert shrub communities (greasewood; Sarcobatus vermiculatus Hook. and black sagebrush/shadscale; Artemisia nova A. Nels; Atriplex confertifolia Torr. & Frem.) to deter cheatgrass ( Bromus tectorum L.) encroachment. We monitored cheatgrass densities for 3 years after the fire in burned drill seeded, burned not-seeded, and unburned plots to assess the rate of invasion and determine the impact on cheatgrass of drill seeding perennial species. Cheatgrass invaded quickly in both shrub sites following the fires. In the greasewood site, drill seeded species germinated but did not establish. This was likely due to a combination of soil salinity and extremely dry weather conditions during the second year of the study. Drill seeded species in the black sagebrush site germinated and established well, resulting in the establishment of 16.5 perennial grasses · m -2 and 1 356 shrubs · ha -1 . Cheatgrass densities were consistently lower in drill seeded versus not-seeded plots, although these were not always statistically different when Bonferroni comparisons were considered. The initial decrease in cheatgrass densities in drill seeded plots may have resulted from soil disturbance coupled with extremely low precipitation rather than competitive effects. Nevertheless, as seeded species mature and increase their competitive ability, we predict long-term suppression of cheatgrass in the absence of further disturbance.

Effect of Method, Site, and Taxon on Line-Intercept Estimates of Sagebrush Cover

Sage-grouse (Centrocercus spp.) are arguably the best known of the many wildlife species that inhabit sagebrush (Artemisia spp.) ecosystems. Lack of standardization in the procedures used to assess sagebrush cover may contribute to inconsistencies in reported habitat requirements for sage-grouse and other wildlife. We compared 3 applications of the line-intercept method for 3 sagebrush taxa. We sampled 2 mountain big sagebrush (A. tridentata vaseyana) sites, 2 Wyoming big sagebrush (A. t. wyomingensis) sites, and 1 black sagebrush (A. nova) site to determine whether the results generated by the 3 methods differed. Percent cover as determined by agency methods was up to 2.6 times greater than that from research applications. Cover differences among techniques were influenced by taxa and site (P ≤ 0.001) because both affected shrub morphology. We believe it will be difficult to identify and achieve wildlife habitat guidelines for minimal sagebrush cover requirements if methodologies are not standardized.

Mule Deer and Elk Foraging Preference for 4 Sagebrush Taxa

A 10 year study under natural winter conditions at 2 sites tested the hypothesis that mule deer (Odocoileus hemionus hemionus) and elk (Cervus elaphus nelsoni) forage equally on 4 sagebrush (Artemisia L.) taxa. Each year approximately 2,500 available leaders on 244 plants on the Northern Yellowstone Winter Range were examined for browsing. Browsing levels increased with winter severity, reaching 91% of leaders browsed for mountain big sagebrush (A. tridentata ssp. vaseyana [Rydb.] Beetle), the preferred taxon (p< 0.05) that averaged 56.1% at the 2 sites. Wyoming big sagebrush (A.t. ssp. wyomingensis Beetle and Young) was narrowly preferred (38.6%) over basin big sagebrush (A.t. Nutt. ssp. tridentata) (30.3%). Black sagebrush (A. nova Nels.) was least preferred (17.0%). Differences in preference among taxa were smallest during the severest winters when more elk were present thereby increasing total sagebrush utilization. Mule deer diets averaged 52% sagebrush over the study. Many sagebrush plants were damaged and even killed by heavy browsing during the study. Promoting sagebrush productivity should be a management objective on similar winter game ranges.

Influence of an Environmental Gradient on Physiology of Singleleaf Pinyon

The acquisition of water and regulation of its loss are important to plant 'success' in arid environments. Species existing over a range of environmental conditions should respond physiologically to varying conditions to maximize water use efficiency and avoid low tissue water potentials. Seasonal and diurnal ecophysiological responses of singleleaf pinyon (Pinus monophylla Torr. and Frem.) were investigated along an environmental gradient involving elevation, moisture and temperature in Nevada. The gradient was represented by study sites in black sagebrush (Artemisia nova A. Nels), mountain big sagebrush (Artemisia tridentata ssp. vaseyana Nutt.), and mountain mahogany (Cercocarpus ledifolius Nutt.) communities. Xylem pressure potential, conductance, and transpiration were measured over 2 growing seasons. Xylem pressure potential and leaf conductance ranged from -3.0 to -0.7 MPa and 0.01 to 0.43 cm s-l, respectively, during the study. Carbon isotope discrimination (delta) of needles was determined in August 1990. Differences in delta values were not significant between sites at the lowest and highest elevations but were significant between the driest site (black sage) and the relatively wetter site (mountain mahogany). Leaf conductance was influenced by but not strongly correlated with predawn xylem pressure potentials, relative humidity, and temperature. Generally, there was little difference in water use characteristics of singleleaf pinyon along the environmental gradient in this study. Thus, it appears that singleleaf pinyon's ability to exist over a range of environmental conditions is not a function of variable ecophysiological responses but an opportunistic response to the availability of resources and conditions suitabie for erowth to occur.

Fire Effects and Fire History of Mesa Verde National Park

Mesa Verde consists of a series of mesas in a north to south trend. The mesa tops are narrow strips, cut by numerous canyons of varying depth. Mesa Verde sandstones, particularly the Cliff House Formation, form the canyon slopes. Long Mesa, an area of focus in this study, has an elevation 2180 m at the south to 2517 m at the north end. Long Canyon cuts down to an elevation of 2133 m. The vegetation on Long Mesa is a mosaic of mature pinon-juniper woodlands and mountain shrub associations. Shrub associations range from Gambels oak, (Quercus gambelii), and serviceberry, (Amelancheir utahensis), to Black Sagebrush, Artemesia nova), and Bitterbrush, (Purshia tridentata). Although there is a body of information concerned with the effect of fire on pinon-juniper woodlands, there are no adequate studies of the shrub-rich pinon-juniper ecosystem of Colorado. Succession following fire was documented by Erdman (1970) in Mesa Verde National Park. He reported that annuals dominate initially, then perennial grasses and forbs, followed by shrub invasion. The open shrub stage becomes a "thicket" approximately 100 years after the fire. The shrubs, he suggests, are outcompeted by pinon and juniper trees, which dominate by about 300 years. Fire and its relationship to resource management in Mesa Verde Park has been outlined by Omi and Emrick (1980). Focus was given to succession (cover and frequency of grass and shrub elements) following the 1873, 1934, and 1972 fires, and models predict the possibilities of control over moderate and severe fires in various vegetation classes within the Park. The study was concerned primarily with the nature of fire behavior and various fire-related management tools for use by Resource Management personnel.

Influence of sagebrush terpenoids on mule deer preference

The effect on mule deer (Odocoileus hemionus hemionus Rafinesque) preference of compounds in mountain big sagebrush [Artemisia tridentata Nutt. ssp.Vaseyana (Rydb.) Beetle], Wyoming big sagebrush (A. t. ssp.Wyomingensis Beetle and Young), basin big sagebrush (A. t. ssp.Tridentata), and black sagebrush (A. nova Nels.) was compared using a two-choice preference test. Compounds tested included:p-cymene, 1,8-cineole, methacrolein (two concentrations), and the nonvolatile crude terpenoid fraction (NVCTF) from each taxon. The compounds were tested by applying them to chopped alfalfa hay at concentrations similar to those found in nature. The intake of the treated hay was compared with that of an untreated control. Eight deer were used as test animals in an 8 - 8 Latin-square design. All compounds tested significantly deterred ingestion (P < 0.05). Compound influence on preference, in order of increasing deterrence, was as follows: 50% methacrolein, mountain big sagebrush NVCTF, methacrolein, basin big sagebrush NVCTF,p- cymene, Wyoming big sagebrush NVCTF, black sagebrush NVCTF, and 1,8-cineole. Methacrolein appears to be an important preference determinant among big sagebrush subspecies, andp-cymene between black sagebrush and big sagebrush. The NVCTFs containing sesquiterpene lactones as one of their constituents were closely related to the preference of all four taxa. Future studies of animal preference for sagebrush should consider all of the potential defensive chemicals in the foliage.

Fire Effects and Fire History of Mesa Verde National Park

Mesa Verde consists of a series of mesas in a north to south trend. The mesa tops are narrow strips, cut by numerous canyons of varying depth. Mesa Verde sandstones, particularly the Cliff House Formation, form the canyon slopes. Long Mesa, an area of focus in this study, has an elevation 2180 m at the south to 2517 m at the north end. Long Canyon cuts down to an elevation of 2133 m. The vegetation on Long Mesa is a mosaic of mature pinon-juniper woodlands and mountain shrub associations. Shrub associations range from Gambels oak, (Quercus gambelii), and serviceberry, (Amelancheir utahensis), to Black Sagebrush, (Artemesia nova), and Bitterbrush, (Purshia tridentata). Although there is a body of information concerned with the effect of fire on pinon-juniper woodlands, there are no adequate studies of the shrub-rich pinon­juniper ecosystem of Colorado. Succession following fire was documented by Erdman (1970) in Mesa Verde National Park. He reported that annuals dominate initially, then perennial grasses and forbs, followed by shrub invasion. The open shrub stage becomes a "thicket" approximately 100 years after the fire. The shrubs, he suggests, are outcompeted by pinon (Pinus edulis) and juniper trees (Juniperus osteosperma), which dominate by about 300 years.

Interpretation of Environmental Gradients Which Influence Sagebrush Community Distribution in Northeastern Nevada

Sagebrush stands on the Humboldt National Forest, northeastern Nevada, were classified by two-way indicator species analysis (TWINSPAN) into 15 community types. Detrended correspondence analysis (DECORANA) was used to ordinate samples and plant species and characterize environmental gradients regulating community structure. Regression of soil attributes with sample ordination scores suggested that the plant communities respond to a complex gradient involving soil depth, water holding capacity, mollic epipedon thickness, clay content, and effective rooting depth. Soil chemical properties which displayed significant correlations with sample ordinations included pH, base saturation, calcium, total nitrogen, organic matter, and phosphorus. These soil properties are considered to either directly influence or indirectly reflect the available soil moisture of a site. The transition from black sagebrush (Artemisia nova Nels.) to low sagebrush (A. arbuscula Nutt.), basin big sagebrush (A. tridentata Nutt. ssp. tridentata) and mountain big sagebrush (A. tridentata Nutt. ssp. vaseyana) stands along DECORANA Axis 1 appeared to represent a gradient of increasing available soil moisture. Elevation and aspect were not correlated with sample ordination scores. This lack of correspondence is presumably due to various soil properties (e.g., depth, rock content, texture) which modify the direct effects of elevation and aspect on available soil moisture.

Crude Terpenoid Influence on in vitro Digestibility of Sagebrush

The infiuence of crude terpenoid content on in vitro organic matter digestibility (IVOMD) was determined for basin big sagebrush (ArteMia trident& Nutt. ssp. tridentata), Wyoming big sagebrush (A.t. ssp. wyomingensis Beetle and Young), mountain big sagebrush (A.t. ssp. vaseyana [Rydb.] Beetle), and black sagebrush (A. nova Nels.). IVOMD was determined using mule deer (OdocoiIeus hemionus hemionus), sheep (Ovis ammon a&s), and steer (Bos taurus) rumen inocula with current year’s growth collected from the 4 taxa at a common site on 1 Jan., 15 Feb., and 1 Apr. 1981. All inocuia had similar digestive efficiency. Extracting crude terpenoids from foliage increased IVOMD by an average of 12.3% overall. Few differences in IVOMD among taxa and dates were evident in foliage after crude terpenoids had been extracted. Order of increasing digestibility among taxa without crude terpenoids extracted was black sagebrush, mountain, Wyoming, and basin big sagebrushes, respectively. IVOMD generally Increased from January to April as crude terpenoids decreased. Crude terpenoid concentrations were lowest in mountain big sagebrush, intermediate in black sagebrush and Wyoming big sagebrush, and greatest in basin big sagebrush.

Crude Terpenoid Influence on Mule Deer Preference for Sagebrush

Samples of current year's growth of leaves and stems were collected in February 1983 from basin big sagebrush (Artemisia tridentata Nutt. tridentata), Wyoming big sagebrush (A.t. wyomingensis Beetle and Young), mountain big sagebrush (A.t. vaseyana [Rydb.] Beetle), and black sagebrush (A. nova Nels.) on a mule deer (Odocoikus hemionus hemionus) winter range near Gardiner, Montana. Samples were from both lightly and heavily used plants (form classes) within each taxon. Crude terpenoids were separated into 3 groups: headspace vapors, volatile, and nonvolatile crude terpenoids. Compounds in each group are thought to stimulate the sensory organs of mule deer. Individual compounds were identified and quantified for comparison with preference ranks among taxa and between utilization form classes. Seven compounds were selected by discriminant analysis as indicators among the 4 taxa, with methacrolein+ethanol, p-cymene, and the sesquiterpene lactones the most probable preference determinants. Seven other compounds were found useful for separating plants within taxa into form classes. Chemical differences between the 2 form classes, however, were less distinguishable than were those among the 4

In Vitro Digestibility of Juniperus osteosperma (Torr.) Little from 17 Utah Sites

Abstract Fall in vitro digestibility was determined on forage collected from Utah juniper (Juniperus osteosperma) trees from 17 sites throughout the pinyon-juniper zone of Utah. On an individual tree basis, the in vitro digestibility ranged from 33.4 to 53.1 percent of dry matter. Forage from mature and juvenile trees was significantly more digested than forage from seedlings. Forage collected from some sites was sigificantly more digested than from other sites. Digestibility across sites ranged from 39.2 to 47.9 percent of dry matter digested. Utah juniper was more digestible than some winter range plants such as antelope bitterbrush (Purshia tridentata), Gambel oak (Quercus gambelii), chokecherry (Prunus virginiana), and less than others such as big sagebrush (Artemisia tridentata) and black sagebrush (Artemisia nova). It is an average to slightly above average winter food for deer. Genetic improvement or selection for superior nutritive cultivars may be possible. Forest Sci. 32:834-840.

Pronghorn Reactions to Winter Sheep Grazing, Plant Communities, and Topography in the Great Basin

The winter distribution of pronghorn over a 142-km2 area on the Desert Experimental Range was significantly related to sheep grazing during the current winter, presence of black sagebrush, and topographic characteristics. Even moderate sheep use during the dormant period left grazing units relatively unfavorable for pronghorn until spring regrowth-at least on ranges where key pronghorn forage plants were in short supply. Winter use areas preferred by pronghorn were above the valley bottoms in rolling to broken topography where black sagebrush communities were evident. Movement characteristics of pronghorn have allowed many of them to readily locate rested grazing units, and, therefore, avoid severe dietary competition with sheep. The Great Basin and other parts of the Intermountain West contain about 16 million ha of low-shrub cold desert. Most of these lands are publicly owned, and their primary use has traditionally been the grazing of sheep in winter and cattle in various seasons. In the last decade or so land managers have intensified efforts to consider the needs of wild animals, and require specific information to consistently make good management decisions. Information is available on pronghorn diets, water requirements, and predator losses (Beale and Holmgren 1975, Beale and Smith 1970, Beale and Smith 1973), but no intensive study has been accomplished in the Great Basin region to document the effects of livestock grazing systems on pronghorn (Antilocapra americana) populations Kindschy et al. 1978). Neither have the impact of other uses of the low-shrub desert on pronghorn been well documented for the Great Basin. A study to probe the effects of winter sheep grazing and certain environmental factors on pronghorn distribution wasconducted on the USDA Forest Service Desert Experimental Range near Milford, Utah, during the winters of 1976-81. Pronghorns thrive best on ranges with a diversity of grass-forbshrub communities (Autenrieth 1978), but are widely adaptable to different forage conditions across the total range of the species. The severity of competition between pronghorns and domestic livestock appears to vary greatly with differences in species of livestock, season of the year, and plant species available to the foraging ruminants (Salwasser 1980, Yoakum 1980). Although pronghorn habitat has mainly been manipulated by livestock grazing, many proposed energy, mineral, and defense activities threaten severe habitat disruptions. Winter ranges are often especially critical for pronghorn and are of particular concern (Kindschy et al. 1978). When the most important plants in the pronghorn's diet are a minor component of the vegetation, widespread surface disturbances or intensive sheep grazing of all available habitat could result in increased winter mortality for the pronghorn. The size and stability of pronghorn winter home ranges appear to be important in the animal's ability to adapt to newly created unfavorable habitat situations. Bayless (1969) found the pronghorn's winter home range to average 10-1 1 kM2, but one-half of the Authors are principal range scientist, Intermountain Forest and Range Experiment Station, Shrub Sciences Laboratory, Provo, Utah 84601; and wildlife biologist, Utah Division of Wildlife Resources, Cedar City, Utah 84720. Authors thank range technician John Kinney for his initiative and consistency of observation which made this study possible. Manuscript received Jan. 21, 1983. animals observed shifted home range at least once during the winter. This suggests that pronghorns may be flexible in their selection and use of wintering areas, although Howard et al. (1980) reported pronghorn avoided rough, broken terrain.