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Sagebrush Ecosystems and Species
Wyoming has more sagebrush than any other state. Sagebrush occupies approximately 50% (32 million acres, Figure 1) of Wyoming's land area (Merrell et al. 1996, BLM 2001, Wyoming Sage-Grouse Working Group 2003). Wyoming’s sagebrush communities are as diverse as the landscape, which is covered by 13 different types of sagebrush. Sagebrush-associated vegetation types provide habitat for approximately 87 species of mammals, 297 species of birds and 63 species of fish, reptiles and amphibians (Wyoming Interagency Vegetation Committee 2002) which have been influenced by historic fire intervals and both domestic and wild ungulate grazing. Many of Wyoming’s species of greatest conservation need (Wyoming Game and Fish Department 2005, Table 1) depend upon healthy sagebrush communities during some part or all of their lives. Wyoming is fortunate to have the opportunity to work with private landowners to conserve sagebrush systems while they still exist across relatively large, intact landscapes. Additionally, the Wyoming Game and Fish Department (WGFD) recognizes humans as essential components of the landscape, and the importance of maintaining responsible economic use of resources must be factored into our primary mission of conserving the state’s wildlife.
(Click map to enlarge)
Figure 1. Distribution of sagebrush on both private and public lands in Wyoming (modified from [Merrell et al. 1996, BLM 2001]).
Table 1. Sagebrush Ecosystems Species of Greatest Conservation Need in Wyoming (WGFD 2005).
Over time, Wyoming’s sagebrush communities have turned into monotypic stands of late successional stage plants that are typically > 50 years old (Wyoming Interagency Vegetation Committee 2002). This has resulted in reduced plant species quantity and diversity. The department’s 2003 Strategic Habitat Annual Report (WGFD 2004) reported that many big sagebrush communities were in advanced seral stages and characterized by a poor understory, plant diversity, and cover. In addition, recorded sagebrush browse use in several areas has exceeded use index thresholds for seven of the past ten years. During that same time period, sagebrush vigor, seed production, and carrying capacity declined, and plant mortality increased. There has been a downward trend in big sagebrush production since 1993. The loss of big sagebrush and loss of diversity and vigor in Wyoming's big sagebrush systems has negatively affected sagebrush-obligate species and other species associated with these ecosystems (Paige and Ritter 1999). Sagebrush-obligate wildlife species have adapted to heterogeneous sagebrush communities comprised of multiple age classes of plants across the landscape. Now that many of these sagebrush communities are predominantly old and decadent, they lack the vigorous younger plants that keep them viable and productive for sagebrush-dependent wildlife. Also, as sagebrush plants become denser, they can dominate the site and become very competitive for water and nutrients. Site domination reduces the forb and grass diversity necessary for a healthy sagebrush community and reduced forb and grass availability decreases the amount of essential food and cover available for wildlife species.
Other problems affecting sagebrush ecosystem include fire suppression. Historic fire intervals and recent fire suppression have shaped much of Wyoming’s sagebrush landscape. Fire suppression has resulted in the increase of woody species and the decrease of important herbaceous species essential to rangeland health.
Noxious and invasive plants are also a threat to the health, vigor and diversity of sagebrush systems. Cheatgrass is a plant that appears to be expanding and rapidly invading sagebrush systems, particularly those that are stressed by drought, excessive herbivory, and other ground disturbing activities such as roads, well pads, and wildfire. The Wyoming Cooperative Weed and Pest Survey data at the University of Wyoming shows cheatgrass increasing in 18 of 23 counties in the state. The survey also reported that ten of the state's 23 counties have more than 20,000 acres of surface dominated by cheatgrass. An increase in cheatgrass cover has been recorded on several previous prescribed burn treatments, as well as in some previously treated sagebrush-mowed areas. Cheatgrass has also been invading 'undisturbed' sagebrush communities, especially on south-facing slopes. Other noxious invaders in the sagebrush system include: Japanese brome (Bromus japonicus), leafy spurge, spotted knapweed, other knapweeds, halogeton (Halogeton glomeratus), and dalmation toadflax (Linaria dalmatica). Noxious and invasive plants can be very aggressive and can dominate plant communities. When this happens, they reduce the diversity of the native plant community and, in turn, reduce the food items and cover diversity that native wildlife have adapted to over thousands of years.
Wyoming is arguably the energy capital of the U.S and mineral development occurs throughout the sagebrush ecosystems in Wyoming and involves the extraction of gas, oil, coal, uranium, bentonite, trona, and other minerals. Extraction of these minerals results in direct removal of sagebrush, and habitat fragmentation is caused by mine excavation, roads, drill pads, fences, power lines, pipelines and other mining activities. These activities directly and indirectly reduce the food, cover, and special habitat requirements available for native species.
Proposed Conservation Actions
Managing the sagebrush landscape for habitat heterogeneity with high shrub cover and vigor, large patch size, little fragmentation, and low disturbance (Holmes and Johnson 2005a,b), will enhance both land sustainability and wildlife populations. Some proposed conservation activities include:
1. Maintain or enhance natural patterns (e.g. seasonal migrations), functions (e.g. cover/food), and processes (e.g. fire) in sagebrush systems;
2. Encourage livestock grazing and sagebrush management practices to improve decadent sagebrush communities that lack sagebrush vigor and understory forb and grass diversity and productivity;
3. Interseed sagebrush stands with forbs and grasses using native seed where appropriate;
4. Establish cooperative agreements with willing landowners to maintain habitat intactness and preserve the sagebrush habitat that is integral for maintaining sagebrush habitat diversity and sagebrush-obligate wildlife species;
5. Develop grass bank or forage reserve management agreements to provide management opportunities for sensitive big sagebrush communities. This may include, but is not limited to, assisting livestock operators with moving grazing to other areas during times when private lands habitat improvement projects are being implemented, and/or from areas affected by wildfires, droughts or other natural events, to enhance sagebrush habitat recovery; and
6. Initiate or continue cooperative efforts to control noxious and invasive plants in sagebrush communities on priority areas in Wyoming.
Sagebrush projects will focus on landscapes predominantly covered by sagebrush communities that have multiple or dense concentrations of at-risk animal and plant species. Additional priority areas include areas important to Greater Sage-Grouse (Centrocercus urophasianus), Sage Sparrow (Amphispiza belli) or Brewer’s Sparrow (Spizella breweri) populations, areas of multiple concern and risk as identified by the Sage-Grouse working groups, and priority areas identified by WGFD’s Strategic Habitat Plan.
Expected Results and Benefits
Prescribed livestock grazing, interseeding, and sagebrush management will improve decadent sagebrush communities that lack sagebrush vigor and diversity, increase productivity in the understory forbs and grasses, and improve habitat for the Greater Sage-Grouse. The Deseret Ranch experienced a six-fold increase in male lek attendance by implementing timed livestock grazing, planting forbs, using mechanical treatments, breaking up stands of old sagebrush, modifying fences, and identifying sagebrush stands for protection (Danvir 2002). Securing permanent conservation easements will maintain open spaces, maintain intact habitats, and prevent habitat fragmentation and conversion of sagebrush habitat integral to maintaining sagebrush habitat diversity and sagebrush obligate wildlife species into the future. Developing grass bank agreements will accelerate and enhance sagebrush habitat recovery.
Prescribed burning done in mosaic patterns in the sagebrush ecosystem can improve high-protein forb and insect diversity in monotypic sagebrush stands. These high-protein forbs and insects can be critical to the survival of Sage-Grouse, Sage Sparrows and Brewer’s Sparrows. Prescribed grazing can improve habitat to leave residual forage to provide nesting cover for Sage-Grouse. The residual cover left by managed grazing in sagebrush also provides insect hiding cover and thus insect food critical to the survival of these three species’ chicks. Grazing can also be adjusted to allow grass, forb, and shrub re-growth to maintain vigor and health of native plants. Maintenance of native vegetation is important to maintain native wildlife species.
All of these activities will maintain or enhance populations of Greater Sage-Grouse, Brewer’s Sparrow and Sage Sparrow for sagebrush ecosystems, and will benefit other sagebrush species such as the:
Sage Thrasher (Oreoscoptes montanus);
Sagebrush vole(Lemmiscus curtatus);
Western harvest mouse (Reithrodontomys megalotis);
Great Basin pocket mouse (Perognathus parvus);
Olive-backed pocket mouse (Perognathus fasciatus);
Plains pocket gopher (Geomys bursarius);
Spotted ground squirrel (Spermophilus spilosoma); and
Eastern red bat (Lasiurus borealis).
Conservation Assessment of Greater Sage-Grouse and Sagebrush Habitats
Wyoming guidelines for managing sagebrush communities with emphasis on fire management
Recommendations for Development of Oil and Gas Resources within Crucial and Important Wildlife Habitats
Literature Cited
BLM. 2001. Map of Wyoming Sagebrush Communities. Prepared by Tom Rinkes, Bureau of Land Management, Wyoming State Office, Cheyenne, Wyoming.
Danvir, R. E. 2002. Sage-Grouse Ecology and Management in Northern Utah Sagebrush-Steppe: A Deseret Land and Livestock Wildlife Research Report. Deseret Land and Livestock Ranch and The Foundation for Quality Resource Management, Woodruff, Utah.
Holmes, J. A., and M. J. Johnson. 2005a. Brewer’s Sparrow (Spizella breweri): a technical conservation assessment [Online]. USDA Forest Service, Rocky Mountain Region, Golden, Colorado. Online: http://www.fs.fed.us/r2/projects/scp/assessments/brewerssparrow.pdf
Holmes, J. A., and M. J. Johnson. 2005b. Sage Sparrow (Amphispiza belli): a technical conservation assessment [Online]. USDA Forest Service, Rocky Mountain Region, Golden, Colorado. Online: http://www.fs.fed.us/r2/projects/scp/assessments/sagesparrow.pdf
Merrill, E. H., T. W. Kohley, M. E. Herdendorf, W. A. Reiners, K. L. Driese, R. W. Marrs, and S. H. Anderson. 1996. Wyoming Gap Analysis: A geographic analysis of biodiversity, final report. Department of Zoology and Physiology, Department of Botany, and Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, Laramie.
Paige, C., and S. A. Ritter. 1999. Birds in a Sagebrush Sea - Managing Sagebrush Habitats for Bird Communities. Partners in Flight - Western Working Group. Boise, Idaho.
Wyoming Game and Fish Department. 2004. Strategic Habitat Plan Accomplishments: 2003 Annual Report. Wyoming Game and Fish Department, Cheyenne, Wyoming.
Wyoming Game and Fish Department. 2005. A comprehensive wildlife conservation strategy for Wyoming. Wyoming Game and Fish Department, Cheyenne, Wyoming.
Wyoming Interagency Vegetation Committee. 2002. Wyoming guidelines for managing sagebrush communities with emphasis on fire management. Wyoming Game and Fish Department and Wyoming Bureau of Land Management, Cheyenne, Wyoming.
Wyoming Sage-Grouse Working Group. 2003. Wyoming Greater Sage-Grouse Conservation Plan. Wyoming Game and Fish Department, Cheyenne, Wyoming.
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