Academic literature on the topic 'Sagebrush obligate'

Abstract Sagebrush communities, covering millions of hectares in the western United States, are among our most imperiled ecosystems. They are challenged by various anthropogenic stressors, including invasion by nonnative grasses that degrade habitat quality and alter ecosystem function. Sagebrush restoration efforts are underway to improve habitat conditions to benefit a wide range of sagebrush-dependent species. Because birds are good indicators of habitat quality, monitoring avian metrics is an effective way to measure progress of sagebrush restoration. We compared avian community composition and individual species abundance among three sagebrush–steppe habitat types with varying degrees of invasion by nonnative crested wheatgrass Agropyron cristatum at the Camas National Wildlife Refuge in southeastern Idaho, USA. Sagebrush-obligate birds, such as sage thrasher Oreoscoptes montanus and sagebrush sparrow Artemisiospiza nevadensis, were most abundant in sagebrush habitats with an understory of native grass. Community composition was similar between sagebrush habitats with native and nonnative grasses, but quite different from bird communities occupying crested wheatgrass. The Habitats and Populations Strategies database, a conservation planning tool, predicts that restoration of crested wheatgrass sites to sagebrush in poor or fair condition will increase the density of sagebrush-obligate bird species. Taken together, these results suggest that restoration of crested wheatgrass near-monocultures back to sagebrush will improve habitat value for much of the bird community whether or not the understory can be converted to primarily native grasses, or a mix of natives and nonnatives. Of the sagebrush bird species of concern, Brewer's sparrow Spizella breweri occupied sagebrush habitats with native vs. nonnative understory at similar abundances, and this species could serve as a metric of intermediate restoration success. However, sagebrush sparrow and sage thrasher, which were significant indicators of sagebrush with native grasses, will likely benefit most from full restoration of a native herbaceous understory. Grassland-obligate birds such as horned lark Eremophila alpestris and grasshopper sparrow Ammodramus savannarum were most abundant at crested wheatgrass–dominated sites and may not benefit from restoration back to shrubland; managers should understand potential trade-offs.

We assessed plant community succession following prescribed fire on ungrazed Wyoming big sagebrush steppe, eastern Oregon. Treatments were burned (Burn; September and October, 2002) and unburned (Control) sagebrush steppe. Herbaceous yield, vegetation canopy cover and density were compared between treatments after fire (2003–18). Herbaceous yield in the Burn treatment was about double the Control for most of the study period. Prior to fire, native perennials comprised 90–95% of herbaceous yield. After fire, native perennials represented 78% (range 67–93%) and exotic annuals 22% (range 7–33%) of total yield. Exotic annuals increased after fire and responded in two stages. In the first 8 years after fire, desert alyssum dominated the annual plant composition. In the last half of the study, cheatgrass co-dominated the annual component with alyssum. Sagebrush recovery was slow and we estimated sagebrush cover would return to pre-burn levels, at the earliest, in 115 years. Burning Wyoming big sagebrush steppe would be detrimental to sagebrush-obligate wildlife for an extended time period, because of lost cover and structure provided by sagebrush. The additional forage provided on burned areas may give livestock manager’s greater flexibility to rest or defer unburned habitat for wildlife species of critical concern.

Iconic sagebrush ecosystems of the American West are threatened by larger and more frequent wildfires that can kill sagebrush and facilitate invasion by annual grasses, creating a cycle that alters sagebrush ecosystem recovery post disturbance. Thwarting this accelerated grass–fire cycle is at the forefront of current national conservation efforts, yet its impacts on wildlife populations inhabiting these ecosystems have not been quantified rigorously. Within a Bayesian framework, we modeled 30 y of wildfire and climatic effects on population rates of change of a sagebrush-obligate species, the greater sage-grouse, across the Great Basin of western North America. Importantly, our modeling also accounted for variation in sagebrush recovery time post fire as determined by underlying soil properties that influence ecosystem resilience to disturbance and resistance to invasion. Our results demonstrate that the cumulative loss of sagebrush to direct and indirect effects of wildfire has contributed strongly to declining sage-grouse populations over the past 30 y at large spatial scales. Moreover, long-lasting effects from wildfire nullified pulses of sage-grouse population growth that typically follow years of higher precipitation. If wildfire trends continue unabated, model projections indicate sage-grouse populations will be reduced to 43% of their current numbers over the next three decades. Our results provide a timely example of how altered fire regimes are disrupting recovery of sagebrush ecosystems and leading to substantial declines of a widespread indicator species. Accordingly, we present scenario-based stochastic projections to inform conservation actions that may help offset the adverse effects of wildfire on sage-grouse and other wildlife populations.

Relatively little is known about pygmy rabbits Brachylagus idahoensis except that they are typically associated with dense stands of big sage Artemisia tridentata. Because they are entirely dependent on sagebrush communities for survival, however, they may potentially serve as an effective means of environmental surveillance in shrub-steppe grasslands. The overall objective of this study is to clarify some of the ecological/physiological adaptations of the world's smallest leporid and define its obligate shrub-steppe association relative to structural, compositional, and micrometeorological features. We placed particular emphasis on the winter ecology of pygmy rabbits, and on understanding how such a small species (400 grams) that does not hibernate or significantly deposit fat, manages to survive in areas of extreme environmental temperatures, consuming primarily sagebrush.

We used remotely sensed imagery to identify and map montane meadow types (M-types) along a moisture gradient, and to develop spectrally-based spatially-explicit models for predicting species diversity patterns in two regions of the Greater Yellowstone Ecosystem: 1) Grand Teton National Park and Bridger Teton National Forest and 2) the Gallatin National Forest and Yellowstone National Park. We investigated the potential to predict species assemblages associated with these meadow types and we also tested our ability to classify specific subsets of montane meadow types such as wetland and sagebrush communities. We also compared our results to the predictability of communities when our sampling sites were classified by GAP analysis. We classified wetlands into 2 categories that differed by the percentage of obligate wetland plant species. Accuracy of wetland classification based upon remotely sensed data was 70%. We classified 4 sagebrush communities [low sagebrush (Artemesia arbuscula), big sagebrush (Artemesia tridentata ssp. vaseyana), mixed low sagebrush/big sagebrush, and bitterbrush (Purshia tridentata)/big sagebrush]. Overall accuracy of our sagebrush community classification based upon remotely sensed data was 65%, and was highest for the mixed big sagebrush/low sagebrush community at 86%. We also investigated the association of plant, bird and butterfly species with each of the meadow types. Because of the rarity of many of the species, our analyses focused on species for which we had minimum standards of data. These standards varied among taxonomic groups, but species only observed infrequently were not included in the analyses. The abundances of 6 of the 11 most abundant bird species were significantly correlated with meadow type as defined by satellite imagery. However, 10 out of 11 bird species showed a significant correlation when both remotely sensed data and landscape variables (e.g., shrub biomass, percent cover of willow or sagebrush, and meadow area) were added to the models. Butterfly species showed even stronger associations with particular meadow types, especially in the Teton region. We used regression tree analyses to separate meadow types by their associated species of butterflies. Fourteen of 67 butterfly species distribution patterns could be used to classify sampling sites into one of five different meadow types with 92% accuracy in 1997 and 96% accuracy in 1998. From the perspective of global climate change indicators, mesic meadows showed the greatest seasonal and interannual variability in spectral response and highest species diversity of plants. Given the rich biodiversity of mesic montane meadows and their sensitivity to variations in temperature and moisture, they may be important to monitor in the context of environmental change. Finally, we were able to do some additional related studies funded by a grant from the Nature Conservancy's David H. Smith Fellowship program (to Su and Debinski). We compared the scale of mapping of biotic communities in the EPA-funded project with the GAP analysis approaches in Montana and Wyoming. We found that both the 1 ha MMU M-Type map and 100 ha MMU Wyoming GAP map were significantly associated with bird, butterfly and plant community similarity. However, the 2 ha Montana GAP map was not associated with bird and plant community similarity and only discriminated differences in butterfly species composition between one map class and the others. This difference is probably explained by the fact that Montana GAP had a coarser categorical resolution of meadow types which was not sensitive to community variation associated with the hydrology of the meadows.

Future demands for increased food production are expected to have severe impacts on prairie biodiversity and ecosystem integrity. Prairie avifauna of North America have experienced drastic population declines, prompting numerous conservation efforts, which have been informed primarily by small-scale studies. We applied a large-scale perspective that integrates scale dependency in avian responses by analyzing observations of 20 prairie bird species (17 grassland obligates and three sagebrush obligate species) from 2009–2012 in the western prairie region of the United States. We employed a multi-species model approach to examine the relationship of land ownership, habitat, and latitude to landscape-scale species richness. Our findings suggest that patterns and processes influencing avian assemblages at the focal-scale (e.g., inference at the sampling unit) may not function at the landscape-scale (e.g., inference amongst sampling units). Individual species responses to land ownership, habitat and latitude were highly variable. The broad spatial extent of our study demonstrates the need to include lands in private ownership to assess biodiversity and the importance of maintaining habitat diversity to support avian assemblages. Lastly, focal-scale information can document species presence within a study area, but landscape-scale information provides an essential complement to inform conservation actions and policies by placing local biodiversity in the context of an entire region, landscape or ecosystem.

In arid and semi-arid landscapes around the world, wildfire plays a key role in maintaining species diversity. Dominant plant associations may depend upon particular fire regime characteristics for their persistence. Mountain shrub communities in high-elevation landscapes of the Intermountain West, USA, are strongly influenced by the post-fire recovery dynamics of the obligate-seeding shrub, mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle). This species is a short-distance disperser with a short-lived seedbank, leading to highly variable post-fire recovery times (15–100 years). We investigated the relative importance of site productivity and seasonal climate in explaining the variance in recovery time for 36 fires, comprising a fire chrono-sequence (from 1971 to 2007) for the Great Basin and Colorado Plateau. A. t. vaseyana recovery was positively related to precipitation in the cool season immediately following fire, likely because deep soil-water recharge that persists throughout the growing season enhances first-year seedling survival. Percentage sand fraction positively correlated with recovery rate yet negatively correlated with live cover in unburnt stands. Our data support the hypothesis that post-fire recovery rate of A. t. vaseyana depends on the climatically controlled ephemerality of the regeneration niche, as is likely true for many arid-land shrub species.

Abstract The pygmy rabbit Brachylagus idahoensis is a sagebrush-obligate species of conservation concern that occurs in the Great Basin and adjacent intermountain areas in the western United States. The species is not known to occur in Colorado, despite proximity to existing populations of pygmy rabbits in Wyoming. We provide the first documentation of the pygmy rabbit in Colorado. Fecal pellets diagnostic of pygmy rabbits were collected in the Vermillion Bluffs area of northwestern Colorado. Samples from 16 pellet clusters were collected for species identification via genetic analyses, and we were able to extract and amplify sufficient DNA from 7 of 16 pellet samples. All seven samples were identified as originating from pygmy rabbits based on a species-specific mitochondrial DNA fragment analysis test. To verify species identification, we also sequenced 225 base pairs of the mitochondrial DNA cytochrome b region from all seven pellet samples. Presence of pygmy rabbits was confirmed from three locations separated by 2.4–7.7 km and pellets represented both adult and juvenile rabbits. Based on the sparseness of burrows in the area, density of pygmy rabbits in the area likely is low; however, systematic surveys by trained observers are needed to delineate the range and density of this species in Colorado. Given the conservation concern for pygmy rabbits across their current range, the newly confirmed presence of this species suggests that assessment of their conservation status in Colorado is warranted.

Changes in shrubsteppe passerine bird habitat associations in response to disturbance were investigated at multiple temporal and spatial scales. Spatial measures incorporated the effects of area at different ecological scales (nest site, territory, and landscape) to include ecologically meaningful extents. Temporal measures included seasonal and annual effects, and were designed to detect lagged responses should they occur. Local-to-landscape scale effects of mechanical restoration treatments on local extirpation and abundances of nine species indicated most were insensitive to changes in habitat quality, while abundance models showed only broad declines. Changing the availability of nesting habitat on both the attractiveness and quality of an area at multiple extents confirmed the need for long-term study effects due to lagged responses in expressed preference and changes to nesting habitat quality. Time since treatment affected nest success in two of the four species, yet the changes in habitat quality did not forecast changes in habitat preference as expected. Non-adaptive mismatches seemingly occurred as habitat preferences indicated treatments may create benign-appearing 'sink' habitat for species that remained in the area. The umbrella species concept is misapplied at this scale: each species' response was consistent, but responses varied in scale, timing, and direction among species. Patterns of nest density and nest site descriptions demonstrated population-level movement in response to treatments, suggesting half the focal species moved nest sites to remaining habitat areas. Larger scale responsive movements were observed in the remaining species, both out of and into the nest plot. Descriptions of nesting habitat characteristics for the focal species tested if the selected nesting habitat was consistent between pre- and post-treatment, and determined which habitat characteristics, including distance to disturbance, were related to nest success. Descriptions of nesting habitat characteristics support previous work in terms of structural characteristics. Habitat selection was consistent even when the available habitat was not, implying these species choose sites and are not merely settling randomly. However, selected nesting habitat was not strongly tied to nest success at local scales and nest success was negatively related to landscape qualities that treatments were designed to enhance.

The pygmy rabbit (Brachylagus idahoensis) is a sagebrush (Artemisia sp.) obligate that depends on sagebrush habitats for food and cover throughout its life cycle. Invasive species, frequent fires, overgrazing, conversion of land to agriculture, energy development, and many other factors have contributed to recent declines in both quantity and quality of sagebrush-steppe habitats required by pygmy rabbits. Because of the many threats to these habitats and the believed decline of pygmy rabbit populations, there is a need to further understand habitat requirements for this species and how they respond to disturbance. This study evaluated habitat selection by pygmy rabbits in Utah and assessed response of this small lagomorph to construction of a large-scale pipeline (i.e. Ruby pipeline) in Utah. We collected habitat data across Utah at occupied sites (pygmy rabbit occupied burrows) and compared these data to similar measurements at unoccupied sites (random locations within sagebrush habitat where pygmy rabbits were not observed). Variables such as horizontal obscurity, elevation, percent understory composed of sagebrush and other shrubs, and sagebrush decadence best described between occupied (active burrow) and unoccupied (randomly selected) sites. Occupied sites had greater amounts of horizontal obscurity, were located at higher elevations, had greater percentage of understory comprised of sagebrush and shrubs, and had less decadent sagebrush. When considering habitat alterations or management these variables should be considered to enhance and protect existing habitat for pygmy rabbits. The Ruby pipeline was a large-scale pipeline project that required the removal of vegetation and the excavation of soil in a continuous linear path for the length of the pipeline. The area that was disturbed is referred to as the right of way (ROW). From our assessment of pygmy rabbit response to construction of the Ruby pipeline, we found evidence for habitat loss and fragmentation as a result of this disturbance. The size of pygmy rabbit space-use areas and home ranges decreased post construction, rabbits shifted core-use areas away from the ROW, and there were fewer movements of collared rabbits across the ROW. Mitigation efforts should consider any action which may reduce restoration time and facilitate movements of rabbits across disturbed areas.

Habitat selection has long been viewed as a multi-scale process. Observed species responses to resource gradients are influenced by variation at the scale of the individual, population, metapopulation, and geographic range. Understanding how species interact with habitat at multiple levels presents a complete picture of an organism and is necessary for conservation of endangered species. The main goal of this dissertation is to evaluate distribution, relative abundance, and habitat selection of a rare species, the pygmy rabbit Brachylagus idahoensis, at multiple scales in order to improve management and conservation for this species. At the broadest scale, pygmy rabbit occurrence and relative abundance were modeled in the Duck Creek allotment of northern Utah using a hierarchical spatial model. Pygmy rabbits are not easily observable, and the model used two levels of indirect detection to make statistically rigorous spatial predictions. We found that the model predicted the general pattern of rabbit occurrence and abundance within the study area, and that there was spatial heterogeneity in the probability of pygmy rabbit occurrence within a study domain that was known to be occupied. The resulting model framework could be used to develop a long-term monitoring program for pygmy rabbits and other species for which hierarchically nested levels of indirect observation are collected. The mid-scale analysis evaluated pygmy rabbit home range placement and movement with respect to sagebrush removal treatments using null models based on an optimal central place foraging behavior. While placement of home-range centers did not appear to be affected by the treatments, within-home range movements were farther from treatments than expected by the null models for two rabbits (of eight), and rabbits that approached treatment edges were less likely to enter treatments than expected by chance. Rabbits are not extirpated from sites that have been treated, but the observed reluctance to enter treated patches calls for caution when conducting sagebrush removal treatments near occupied pygmy rabbit burrows. At the finest level of resolution, the spatial ecology of pygmy rabbit use of burrows was evaluated. Both the placement of burrows in general and pygmy rabbit use of burrows were clustered. While the habitat gradients experienced by each of the rabbits evaluated affected the modeled habitat selection responses, some generalities were observed. Selection of high cover suggests that pygmy rabbit use of burrows may be linked to predator avoidance behavior. Additionally, pygmy rabbit use of clustered burrows affects management actions including: habitat modeling, monitoring, and species introduction. Explicit attention to resource distribution will improve efforts to predict species responses to management actions.