Influence of Land-Use Legacies Following Shrub Reduction and Seeding of Big Sagebrush Sites

Big sagebrush (Artemisia tridentata Nutt.) plant communities often require management to reduce shrub density and rehabilitate understory vegetation. We studied vegetation responses to a two-way chain harrow treatment and broadcast seeding of 12 herbaceous species at eight Wyoming big sagebrush (A. tridentata Nutt. subsp. wyomingensis Beetle & Young) sites. These sites differed in land-use history; five were cultivated for dryland wheat production during the 1950 ? 1980s and then seeded with introduced forage grasses (C-S), while three had not been exposed to this land-use legacy (non C-S). Our objective was to evaluate whether the C-S legacy influences the magnitude of vegetation change following contemporary treatment. Before treatment, C-S sites had lower sagebrush cover, higher dead sagebrush cover, and higher broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) cover than adjacent non C-S sites. Plant community change 3 years after treatment, determined with multivariate ordination analysis of species composition, varied between site histories, and response to treatment was most strongly correlated with reductions in sagebrush cover, increases in perennial grasses, and increases in 10 other herbaceous species—including some undesirable species and four that were seeded in 2010. Five years after treatment, mature sagebrush cover remained reduced for both land-use histories, yet density of sagebrush seedlings and broom snakeweed increased in C-S sites during the second and third years after treatment. In addition, perennial forb cover increased for C-S sites, while perennial grass biomass increased for non C-S sites. Our results emphasize that broad variability in plant community responses to sagebrush reduction and seeding is possible within the same ecological site classification and that legacy effects due to the combination of past cultivation and seeding should be considered when planning restoration projects, including the consideration that seeding may not always be necessary on C-S sites.     

Disturbance Type and Sagebrush Community Type Affect Plant Community Structure After Shrub Reduction

Treatments to reduce shrub cover are commonly implemented with the objective of shifting community structure away from shrub dominance and toward shrub and perennial grass codominance. In sagebrush (Artemisia L.) ecosystems, shrub reduction treatments have had variable effects on target shrubs, herbaceous perennials, and non-native annual plants. The factors mediating this variability are not well understood. We used long-term data from Utah’s Watershed Restoration Initiative project to assess short-term (1 − 4 yr post-treatment) and long-term (5 − 12 yr post-treatment) responses of sagebrush plant communities to five shrub reduction treatments at 94 sites that span a range of abiotic conditions and sagebrush community types. Treatments were pipe harrow with one or two passes, aerator, and fire with and without postfire seeding. We analyzed effect sizes (log of response ratio) to assess responses of sagebrush, perennial and annual grasses and forbs, and ground cover to treatments. Most treatments successfully reduced sagebrush cover over the short and long term. All treatments increased long-term perennial grass cover in Wyoming big sagebrush (A. tridentata Nutt. ssp. wyomingensis Beetle & Young) communities, but in mountain big sagebrush (ssp. vaseyana [Rydb.] Beetle) communities, perennial grasses increased only when seeded after fire. In both sagebrush communities, treatments generally resulted in short-term, but not long-term, increases in perennial forb cover. Annual grasses (largely invasive cheatgrass, Bromus tectorum L.) increased in all treatments on sites dominated by mountain big sagebrush but stayed constant or decreased on sites dominated by Wyoming big sagebrush. This result was unexpected because sites dominated by Wyoming big sagebrush are typically thought to be less resilient to disturbance and less resistant to invasion than sites dominated by mountain big sagebrush. Together, these results indicate some of the benefits, risks, and contingent outcomes of sagebrush reduction treatments that should be considered carefully in any future decisions about applying such treatments.     

Herbaceous Biomass Response to Prescribed Fire in Juniper-Encroached Sagebrush Steppe

Western juniper (Juniperus occidentalis Hook.) has expanded into sagebrush steppe plant communities the past 130 ? 150 yr in the northern Great Basin. The increase in juniper reduces herbage and browse for livestock and big game. Information on herbaceous yield response to juniper control with fire is limited. We measured herbaceous standing crop and yield by life form in two mountain big sagebrush communities (MTN1, MTN2) and a Wyoming/basin big sagebrush (WYOBAS) community for 6 yrs following prescribed fire treatments to control western juniper. MTN1 and WYOBAS communities were early-successional (phase 1) and MTN2 communities were midsuccessional (phase 2) woodlands before treatment. Prescribed fires killed all juniper and sagebrush in the burn units. Total herbaceous and perennial bunchgrass yields increased 2 to 2.5-fold in burn treatments compared with unburned controls. Total perennial forb yield did not differ between burns and controls in all three plant communities. However, tall perennial forb yield was 1.6- and 2.5-fold greater in the WYOBAS and MTN2 burned sites than controls. Mat-forming perennial forb yields declined by 80 ? 90% after burning compared with controls. Cheatgrass yield increased in burned WYOBAS and MTN2 communities and at the end of the study represented 10% and 22% of total yield, respectively. Annual forbs increased with burning and were mainly composed of native species in MTN1 and MTN2 communities and non-natives in WYOBAS communities. Forage availability for livestock and wild ungulates more than doubled after burning. The additional forage provided on burned areas affords managers greater flexibility to rest and treat additional sagebrush steppe where juniper is expanding, as well as rest or defer critical seasonal habitat for wildlife.     

Vegetation,Hydrologic, and Erosion Responses of Sagebrush Steppe 9 Yr Following Mechanical Tree Removal

Land managers across the western United States are faced with selecting and applying tree-removal treatments on pinyon (Pinus spp.) and juniper (Juniperus spp.) woodland-encroached sagebrush (Artemisia spp.) rangelands, but current understanding of long-term vegetation and hydrological responses of sagebrush sites to tree removal is inadequate for guiding management. This study applied a suite of vegetation and soil measures (0.5 ? 990 m²), small-plot rainfall simulations (0.5 m²), and overland flow experiments (9 m²) to quantify the effects of mechanical tree removal (tree cutting and mastication) on vegetation, runoff, and erosion at two mid- to late-succession woodland-encroached sagebrush sites in the Great Basin, United States, 9 yr after treatment. Low amounts of hillslope-scale shrub (3 ? 15%) and grass (7 ? 12%) canopy cover and extensive intercanopy (area between tree canopies) bare ground (69 ? 88% bare, 75% of area) in untreated areas at both sites facilitated high levels of runoff and sediment from high-intensity (102 mm ? h^? 1, 45 min) rainfall simulations in interspaces (~ 45 mm runoff, 59 ? 381 g ? m^? 2 sediment) between trees and shrubs and from concentrated overland flow experiments (15, 30, and 45 L ? min^? 1, 8 min each) in the intercanopy (371 ? 501 L runoff, 2 342 ? 3 015 g sediment). Tree cutting increased hillslope-scale density of sagebrush by 5% and perennial grass cover by twofold at one site while tree cutting and mastication increased hillslope-scale sagebrush density by 36% and 16%, respectively, and perennial grass cover by threefold at a second more-degraded (initially more sparsely vegetated) site over nine growing seasons. Cover of cheatgrass (Bromus tectorum L.) was < 1% at the sites pretreatment and 1 ? 7% 9 yr after treatment. Bare ground remained high across both sites 9 yr after tree removal and was reduced by treatments solely at the more degraded site. Increases in hillslope-scale vegetation following tree removal had limited impact on runoff and erosion for rainfall simulations and concentrated flow experiments at both sites due to persistent high bare ground. The one exception was reduced runoff and erosion within the cut treatments for intercanopy plots with cut-downed-trees. The cut-downed-trees provided ample litter cover and tree debris at the ground surface to reduce the amount and erosive energy of concentrated overland flow. Trends in hillslope-scale vegetation responses to tree removal in this study demonstrate the effectiveness of mechanical treatments to reestablish sagebrush steppe vegetation without increasing cheatgrass for mid- to late-succession woodland-encroached sites along the warm-dry to cool-moist soil temperature ? moisture threshold in the Great Basin. Our results indicate improved hydrologic function through sagebrush steppe vegetation recruitment after mechanical tree removal on mid- to late-succession woodlands can require more than 9 yr. We anticipate intercanopy runoff and erosion rates will decrease over time at both sites as shrub and grass cover continue to increase, but follow-up tree removal will be needed to prevent pinyon and juniper recolonization. The low intercanopy runoff and erosion measured underneath isolated cut-downed-trees in this study clearly demonstrate that tree debris following mechanical treatments can effectively limit microsite-scale runoff and erosion over time where tree debris settles in good contact with the soil surface.     

Longer-Term Evaluation of Sagebrush Restoration After Juniper Control and Herbaceous Vegetation Trade-offs

Degradation of shrublands around the world from altered fire regimes, overutilization, and anthropogenic disturbance has resulted in a widespread need for shrub restoration. In western North America, reestablishment of mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) is needed to restore ecosystem services and function. Western juniper (Juniperus occidentalis ssp. occidentalis Hook) encroachment is a serious threat to mountain big sagebrush communities in the northern Great Basin and Columbia Plateau. Juniper trees can be controlled with fire; however, sagebrush recovery may be slow, especially if encroachment largely eliminated sagebrush before juniper control. Short-term studies have suggested that seeding mountain big sagebrush after juniper control may accelerate sagebrush recovery. Longer-term information is lacking on how sagebrush recovery progresses and if there are trade-offs with herbaceous vegetation. We compared seeding and not seeding mountain big sagebrush after juniper control (partial cutting followed with burning) in fully developed juniper woodlands (i.e., sagebrush had been largely excluded) at five sites, 7 and 8 yr after seeding. Sagebrush cover averaged ~ 30% in sagebrush seeded plots compared with ~ 1% in unseeded plots 8 yr after seeding, thus suggesting that sagebrush recovery may be slow without seeding after juniper control. Total herbaceous vegetation, perennial grass, and annual forb cover was less where sagebrush was seeded. Thus, there is a trade-off with herbaceous vegetation with seeding sagebrush. Our results suggest that seeding sagebrush after juniper control can accelerate the recovery of sagebrush habitat characteristics, which is important for sagebrush-associated wildlife. We suggest land manager and restoration practitioners consider seeding sagebrush and possibly other shrubs after controlling encroaching trees where residual shrubs are lacking after control.     

Evaluating Mechanical Treatments and Seeding of a Wyoming Big Sagebrush Community 10 Yr Post Treatment

Increased cover of perennial grasses and forbs would increase the wildlife and forage value of many Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle & Young) communities, as well as increase their resistance to weeds. We compared six mechanical treatments in conjunction with seeding a Wyoming big sagebrush community in northern Utah over a 10-yr period. The treatments included disk plow followed by land imprinter, one-way Ely chain, one- and two-way pipe harrow, all applied in fall, and meadow aerator applied in fall and spring. A mixture of native and introduced grasses and forbs was broadcast seeded at 18.3 kg PLS ha^? 1 after the disk and before the imprinter and all other treatments. The experiment was installed in three randomized blocks, and density and cover data were collected before treatment in 2001 and 1, 2, 5, and 10 yr after treatment. All treatments initially reduced sagebrush and residual herbaceous cover and increased seeded species cover compared with the untreated control. By 10 yr after treatment, sagebrush cover was 24.5% ± 0.35% on the control, 1.6% ± 0.28% on the disk imprinter treatment, and 11.7% ± 0.79% on all other treatments. At that time, seeded grass cover was 16.5% ± 1.22% on the disk imprinter treatment and an average of 2% ± 0.1% on all other mechanical treatments. Sagebrush seedlings were recruited in all of the mechanical treatments, but least in the disk imprinter treatment. After 10 yr, the untreated control was dominated by decadent sagebrush and rabbitbrush, the disk imprinter treatment was dominated by seeded perennial grasses, and the other mechanical treatments shared dominance of sagebrush and native perennial grasses. Mechanical treatments changed the composition of this community while retaining sagebrush, but greatest understory increases were associated with greatest control of sagebrush and establishment of seeded species by disk imprinting.     

Contrasting Effects of Long-Term Fire on Sagebrush Steppe Shrubs Mediated by Topography and Plant Community

The role of fire in restoration of sagebrush plant communities remains controversial mainly because of paucity of information from long-term studies. Here, we examine 15-year post-fire responses of big sagebrush (Artemisia tridentata ssp wyomingensis) and broom snakeweed (Gutierrezia sarothrae), the two most abundant native shrubs at the John Day Fossil Beds National Monument, a protected area in north-central Oregon, USA. Fire effects were studied along gradients of topography and community type through time post-burn. Community types were distinguished as brush, plots dominated by big sagebrush and woodland, plots with a significant presence of Western juniper (Juniperus occidentalis) trees. Fire reduced big sagebrush cover in brush plots up to 100% and in woodland plots up to 86%. Broom snakeweed cover declined by 92% and 73% in brush plots and woodland plots, respectively. Big sagebrush did not show signs of recovery 15 years after burning regardless of topography and community type while broom snakeweed populations were clearly rebounding and prospering beyond pre-burn levels. Our results showed that an area initially dominated by big sagebrush (cover of big sagebrush 10-20%, cover of broom snakeweed 2-4%) dramatically shifted to an area dominated by broom snakeweed (cover of big sagebrush < 1%, cover of broom snakeweed 5%) in brush-dominated plots. Our results indicated that brush-dominated plots at lower elevation and southern exposures are the least post-fire resilient. We also observed a declining population of big sagebrush on unburned areas, suggesting the lack of post-fire recovery on burned areas was perhaps a result of low seeding potential by extant populations. Although more years of observation are required, these data indicate that recovery time, the encroachment of opportunistic competing shrubs, and the initial condition of vegetation are essential considerations by land managers when prescribing fire in big sagebrush communities.     

The Response of Thurber’s Needlegrass to Fall Prescribed Burning

Thurber’s needlegrass (Achnatherum thurberianum [Piper] Barkworth) is an important component of many sagebrush communities in the Intermountain West. Prescribed fall burning is often implemented in sagebrush plant communities to mimic historic wildfires, improve wildlife habitat, and increase livestock forage production. Burning is used because it shifts dominance from sagebrush to herbaceous vegetation. The effects of prescribed fall burning on Thurber’s needlegrass are largely unexplored. The purpose of this study was to determine the response of Thurber’s needlegrass to prescribed fall burning. A randomized block design was used, and each block consisted of a fall burned and unburned (control) Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis [Beetle & A. Young] S. L. Welsh)–bunchgrass communities. Response variables measured in the first and second years after burns were Thurber’s needlegrass community foliar cover and density, vegetative and reproductive biomass, photosynthetic rates, tissue carbon (C) and nitrogen (N) content, and N (¹⁵N:¹⁴N) and C (¹³C:¹²C) isotope ratios. Density of Thurber’s needlegrass in both postburn years and cover in the second postburn year were not different between treatments (P > 0.05), but cover was less in the burned than control treatment in the first postburn year (P = 0.008). Carbon isotope ratios in Thurber’s needlegrass differed between the burn (-25.9 ±  SE) and control (-26.3 ±  SE) treatments in the first postburn year (P = 0.019). Nitrogen isotope ratios indicated nitrogen was more available in the burned than control treatment in both years (P < 0.05). Photosynthetic rates of Thurber’s needlegrass were also generally greater in the burned than control treatment (P = 0.045). Our results suggest burning altered the availability of resources to Thurber’s needlegrass plants. Our results also suggest that prescribed fall burning is not detrimental to Thurber’s needlegrass and, thus, can be used as a method to shift dominance from sagebrush to herbaceous vegetation.     

Site,Competition, and Plant Stock Influence Transplant Success of Wyoming Big Sagebrush

Within the sagebrush steppe ecosystem, sagebrush plants influence a number of ecosystem properties, including nutrient distribution, plant species diversity, soil moisture, and temperature, and provide habitat for a wide variety of wildlife species. Recent increases in frequency and size of wildfires and associated annual grass expansion within the Wyoming big sagebrush alliance have increased the need for effective sagebrush restoration tools and protocols. Our objectives were to quay the success of Wyoming big sagebrush transplants relative to transplant stock (nursery seedlings vs. wildlings) across different ecological sites and vegetation types and to test the hypothesis that reduction of herbaceous vegetation would increase survival of transplanted sagebrush. We used a randomized block (reps = 5) design at each of three sites—1) cheatgrass dominated, 2) native plant dominated, and 3) crested wheatgrass dominated—near Elko, Nevada. Treatments included plant stock (nursery stock or locally harvested wildlings) and herbicide (glyphosate) to reduce competition from herbaceous vegetation. Transplants were planted in the spring of 2009 and 2010 and monitored for survival. Data were analyzed for site and treatment effects using mixed-model ANOVA. Surviving plant density at and 2 yr postplanting was generally highest (up to 3-fold) on the native site (P < 0.05). Density of surviving transplants was almost 3-fold higher for nursery stock on most sites for the 2009 planting, but differences in survival by planting stock were minimal for the 2010 planting. Glyphosate application increased surviving plant density up to 300% (depending on site) for both years of planting. High labor and plant material investments (relative to traditional drilling or broadcasting) may limit the size of projects for which sagebrush transplants are practical, but these costs may be partially offset by high success relative to traditional methods. Our data indicate that sagebrush transplants can be effective for establishing sagebrush on depleted sites.     

Short-Term Response of Sage-Grouse Nesting to Conifer Removal in the Northern Great Basin

Conifer woodlands expanding into sage-steppe (Artemisia spp.) are a threat to sagebrush obligate species including the imperiled greater sage-grouse (Centrocercus urophasianus). Conifer removal is accelerating rapidly despite a lack of empirical evidence to assess outcomes to grouse. Using a before-after-control-impact design, we evaluated short-term effects of conifer removal on nesting habitat use by monitoring 262 sage-grouse nests in the northern Great Basin during 2010–2014. Tree removal made available for nesting an additional 28% of the treatment landscape by expanding habitat an estimated 9603 ha (3201 ha [± 480 SE] annually). Relative probability of nesting in newly restored sites increased by 22% annually, and females were 43% more likely to nest within 1000 m of treatments. From 2011 (pretreatment) to 2014 (3 yr after treatments began), 29% of the marked population (9.5% [± 1.2 SE] annually) had shifted its nesting activities into mountain big sagebrush habitats that were cleared of encroaching conifer. Grouping treatments likely contributed to beneficial outcomes for grouse as individual removal projects averaged just 87 ha in size but cumulatively covered a fifth of the study area. Collaboratively identifying future priority watersheds and implementing treatments across public and private ownerships is vital to effectively restore the sage-steppe ecosystem for nesting sage-grouse.     

Rough Soil Surface Lessens Annual Grass Invasion in Disturbed Rangeland

Effective manipulations to prevent the spread of invasive species are needed. Downy brome (Bromus tectorum L.) is an annual invader that often expands after disturbances, compromising restoration of big sagebrush (Artemisia tridentata Nutt.) communities in western North America. This study examined the effects of two manipulations that may slow seed dispersal: soil microtopography (roughened with 50-cm relief or flat) and woody debris (0.024 m³·m^? 2 or none) on restoration of four disturbed mountain big sagebrush (A. tridentata Nutt. ssp. vaseyana) sites in Colorado. Treatments were crossed with seeding in a fully factorial experiment (n = 3). Microtopography and woody debris treatments were also crossed in a seed dispersal experiment using fluorescently marked downy brome seeds. In the restoration study, downy brome invaded two sites, one pervasively and one patchily. Seeding limited downy brome cover at both of these sites and also increased perennial grass and forb cover while limiting shrub cover. At the pervasively invaded site, the rough surface reduced unseeded plot downy brome cover from 13% to 3% by 5 yr post treatment. Woody debris increased shrub and perennial grass cover but had little effect on downy brome. In the seed dispersal experiment, the rough surface reduced downy brome mean dispersal distance twofold to threefold and 95% quantile distance threefold to sixfold. Woody debris slightly reduced downy brome dispersal only within rough surface plots. A rough surface may aid restoration by trapping downy brome seeds near the parent plant, limiting their spatial distribution, increasing intraspecific competition, and reducing propagule pressure. Designing landscapes to slow seed dispersal may help control invasives and promote establishment of seeded species.     

Mapping Tree Canopy Cover in Support of Proactive Prairie Grouse Conservation in Western North America

Invasive woody plant expansion is a primary threat driving fragmentation and loss of sagebrush (Artemisia spp.) and prairie habitats across the central and western United States. Expansion of native woody plants, including conifer (primarily Juniperus spp.) and mesquite (Prosopis spp.), over the past century is primarily attributable to wildfire suppression, historic periods of intensive livestock grazing, and changes in climate. To guide successful conservation programs aimed at reducing top-down stressors, we mapped invasive woody plants at regional scales to evaluate landscape level impacts, target restoration actions, and monitor restoration outcomes. Our overarching goal was to produce seamless regional products across sociopolitical boundaries with resolution fine enough to depict the spatial extent and degree of woody plant invasion relevant to greater sage-grouse (Centrocercus urophasianus) and lesser prairie-chicken (Tympanuchus pallidicinctus) conservation efforts. We mapped tree canopy cover at 1-m spatial resolution across an 11-state region (508 265 km²). Greater than 90% of occupied lesser prairie-chicken habitat was largely treeless for conifers (< 1% canopy cover), whereas > 67% was treeless for mesquite. Conifers in the higher canopy cover classes (16 ? 50% and > 50% canopy cover) were scarce (< 2% and 1% canopy cover), as was mesquite (< 5% and 1% canopy cover). Occupied habitat by sage-grouse was more variable but also had a relatively large proportion of treeless areas ($\stackrel{?}{x}$ = 71, SE = 5%). Low to moderate levels of conifer cover (1 ? 20%) were fewer ($\stackrel{?}{x}$ = 23, SE = 5%) as were areas in the highest cover class (> 50%; $\stackrel{?}{x}$ = 6, SE = 2%). Mapping indicated that a high proportion of invading woody plants are at a low to intermediate level. Canopy cover maps for conifer and mesquite resulting from this study provide the first and most geographically complete, high-resolution assessment of woody plant cover as a top-down threat to western sage-steppe and prairie ecosystems.     

Longer-Term Evaluation of Revegetation of Medusahead-Invaded Sagebrush Steppe

Medusahead (Taeniatherum caput-medusae [L.] Nevski) and other exotic annual grasses have invaded millions of hectares of sagebrush (Artemisia L.) steppe. Revegetation of medusahead-invaded sagebrush steppe with perennial vegetation is critically needed to restore productivity and decrease the risk of frequent wildfires. However, it is unclear if revegetation efforts provide long-term benefits (fewer exotic annuals and more perennials). The limited literature available on the topic questions whether revegetation efforts reduce medusahead abundance beyond 2 or 3 yr. We evaluated revegetation of medusahead-invaded rangelands for 5 yr after seeding introduced perennial bunchgrasses at five locations. We compared areas that were fall-prescribed burned immediately followed by an imazapic herbicide treatment and then seeded with bunchgrasses 1 yr later (imazapic-seed) with untreated controls (control). The imazapic-seed treatment decreased exotic annual grass cover and density. At the end of the study, exotic annual grass cover and density were 2-fold greater in the control compared with the imazapic-seed treatment. The imazapic-seed treatment had greater large perennial bunchgrass cover and density and less annual forb (predominately exotic annuals) cover and density than the untreated control for the duration of the study. At the end of the study, large perennial bunchgrass density average 10 plant ? m^? 2 in the imazapic-seed treatment, which is comparable with intact sagebrush steppe communities. Plant available soil nitrogen was also greater in the imazapic-seed treatment compared with the untreated control for the duration of the study. The results of this study suggest that revegetation of medusahead-invaded sagebrush steppe can provide lasting benefits, including limiting exotic annual grasses.     

Eighty Years of Grazing by Cattle Modifies Sagebrush and Bunchgrass Structure

Grazing by cattle is ubiquitous across the sagebrush steppe; however, little is known about its effects on sagebrush and native bunchgrass structure. Understanding the effects of long-term grazing on sagebrush and bunchgrass structure is important because sagebrush is a keystone species and bunchgrasses are the dominant herbaceous functional group in these communities. To investigate the effects of long-term grazing on sagebrush and bunchgrass structure, we compared nine grazing exclosures with nine adjacent rangelands that were grazed by cattle in southeast Oregon. Grazing was moderate utilization (30 ? 45%) with altering season of use and infrequent rest. Long-term grazing by cattle altered some structural aspects of bunchgrasses and sagebrush. Ungrazed bunchgrasses had larger dead centers in their crowns, as well as greater dead fuel depths below and above the crown level compared with grazed bunchgrasses. This accumulation of dry fuel near the meristematic tissue may increase the probability of fire-induced mortality during a wildfire. Bunchgrasses in the ungrazed treatment had more reproductive stems than those in the long-term grazed treatment. This suggests that seed production of bunchgrasses may be greater in ungrazed areas. Sagebrush height and longest canopy diameter were 15% and 20% greater in the ungrazed compared with the grazed treatment, respectively. However, the bottom of the sagebrush canopy was closer to the ground in the grazed compared with the ungrazed treatment, which may provide better hiding cover for ground-nesting avian species. Sagebrush basal stem diameter, number of stems, amount of dead material in the canopy, canopy gap size, and number of canopy gaps did not differ between ungrazed and grazed treatments. Moderate grazing does not appear to alter the competitive relationship between a generally unpalatable shrub and palatable bunchgrasses. Long-term, moderate grazing appears to have minimal effects to the structure of bunchgrasses and sagebrush, other than reducing the risk of bunchgrass mortality during a fire event.     

Comparison between the effects of postanesthetic xylazine and dexmedetomidine on characteristics of recovery from sevoflurane anesthesia in horses

Objective

To compare postanesthetic xylazine and dexmedetomidine on recovery characteristics from sevoflurane anesthesia in horses.

Plant Interspaces Resulting From Contrasting Grazing Management in Northern Mixed-Grass Prairie: Implications for Ecosystem Function

We assessed plant interspaces in July 2007 using continuous line intercepts in twice-replicated pastures of northern mixed-grass prairie with contrasting grazing treatments: 1) long-term (25 yr) heavily grazed, dominated by the bunchgrass blue grama (Bouteloua gracilis), and 2) ungrazed, dominated by the rhizomatous grass western wheatgrass (Pascopyrum smithii). The number of plant interspaces was 26% higher in pastures heavily grazed, but the amount of soil surface occupied by plant interspaces was 27% greater without grazing. Plant interspaces were larger without grazing (14.8 ±  cm, mean ± 1 SE) than heavily grazed (8.9 ±  cm). Plant interspaces represented 87% and 68% of the total soil surface in the ungrazed and heavily grazed communities, respectively. The percentage of soil surface covered by plant interspaces < 20 cm was higher for the heavily grazed (94%) compared to the ungrazed (79%). Litter cover in the plant interspaces was higher without grazing (80 ± 1%) compared to the heavily grazed (57 ± 3%). Grazing-induced structural changes from a rhizomatous- to a bunchgrass-dominated vegetation community were manifest in the size and distribution of plant interspaces. Ecological consequences for erosion from raindrop impacts in larger plant interspaces in the ungrazed community are likely offset by greater litter cover in these communities; conversely, lower litter cover in heavily grazed pastures may increase erosion potential despite occurrence of smaller plant interspaces and less proportion of the soil surface covered by interspaces. Management practices that increase the cover of litter in plant interspaces should reduce the potential of erosion from water and wind in this semiarid rangeland.     

Plant Age and Growing Season Nutritional Content Relationships of Three Artemisia tridentata Subspecies

The effect of plant age on growing season chemical compositions and rumen fermentation characteristics was determined for three subspecies of big sagebrush: basin (Artemisia tridentata [Nutt.] subsp. tridentata), mountain (A. tridentata subsp. vaseyana [Rybd.] Beetle), and Wyoming (A. tridentata subsp. wyomingensis [Beetle and Young]). In vitro dry matter (IVDMD) and organic matter (IVOMD) disappearance, ammonia nitrogen (NH₃N), and volatile fatty acid (VFA) content were determined at the end of two fermentation periods (24 h and 48 h) by combining rumen inocula with age-classified vegetative samples from each sagebrush subspecies. An additional one-way analysis of variance was performed to investigate potential differences among subspecies in IVDMD, IVOMD, total VFA, and NH₃N following a 48-h fermentation period. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) components were also compared among sagebrush subspecies. Age class responses were variable across the spectrum of sagebrush subspecies and response variables. Where plant age effects were indicated, the small numeric differences probably have little biological or ecological significance. Mountain sagebrush was lower in IVOMD and total VFA concentrations (P < 0.0001) than basin and Wyoming. NH₃N concentration and CP were higher (P < 0.0001) in basin sagebrush than the other two subspecies, while Wyoming sagebrush was higher in NDF, ADF, and ADL than basin and mountain subspecies (P < 0.0001). NH₃N concentration for all three subspecies was lower than the minimum level (20 mg · 100 mL^?1) required for uninhibited rumen activity. Overall, this research questions the contention that older sagebrush plants offer less nutritional value than younger ones, at least for growing season conditions. The results also provide information that can be utilized in designing supplementation strategies for domestic animals on diets with characteristically high utilization of big sagebrush.     

Evaluation of BAM (butorphanol–azaperone–medetomidine) in captive African lion (Panthera leo) immobilization

Objective

The combination of butorphanol, azaperone and medetomidine (BAM) with subsequent antagonism by naltrexone–yohimbine or naltrexone–atipamezole was evaluated for reversible immobilization of captive African lions (Panthea leo).

Extending Conifer Removal and Landscape Protection Strategies from Sage-grouse to Songbirds,a Range-Wide Assessment

Recent and unprecedented scale of greater sage-grouse (Centrocercus urophasianus) conservation in the American West enables assessment of community-level benefits afforded to other sagebrush-obligate species. We use North American Breeding Bird Survey (BBS) count data and machine-learning to assess predictors influencing spatial distribution and abundance of three sagebrush-obligate songbirds (Brewer’s sparrow [Spizella breweri], sagebrush sparrow [Artemisiospiza nevadensis], and sage thrasher [Oreoscoptes montanus]). We quantified co-occurrence of songbird abundance with sage-grouse lek distributions using point pattern analyses and evaluated the concurrence of songbird abundance within sage-grouse habitat restoration and landscape protection. Sagebrush land-cover predictors were positively associated with the abundance of each songbird species in models that explained 16 ? 37% of variation in BBS route level counts. Individual songbird models identified an apparent 40% threshold in sagebrush land-cover, over which songbird abundances nearly doubled. Songbird abundances were positively associated with sage-grouse distributions (P < 0.01); range-wide, landscapes supporting > 50% of males on leks also harbored 13 ? 19% higher densities of songbirds compared with range-wide mean densities. Eighty-five percent of the conifer removal conducted through the Sage Grouse Initiative coincided with high to moderate Brewer’s sparrow abundance. Wyoming’s landscape protection (i.e., “core area”) strategy for sage-grouse encompasses half the high to moderate abundance sagebrush sparrow and sage thrasher populations. In the Great Basin half the high to moderate abundance sagebrush sparrow and sage thrasher populations coincide with sage-grouse Fire and Invasive Assessment Tool priorities, where conservation actions are being focused in an attempt to reduce the threat of wildfire and invasive plants. Our work illustrates spatially targeted actions being implemented ostensibly for sage-grouse largely overlap high abundance centers for three sagebrush obligate passerines and are likely providing significant conservation benefits for less well-known sagebrush songbirds and other sagebrush-associated wildlife.