Risk of Cheatgrass Displacement of Sagebrush and other Native Vegetation

Among threats to the sagebrush ecosystem in the Great Basin and elsewhere (BLM 1999, 2002; Nachlinger et al. 2001; Wisdom et al. 2003) is the threat of displacement of native habitats by cheatgrass (Bromus tectorum). Mapping these threats in the sagebrush ecosystem will allow managers to identify areas of native vegetation at high risk of displacement, where active restoration may be required, versus areas at low risk, where conservation of existing habitats may be preferable. A draft model of risk of displacement of sagebrush and other native vegetation cover types by cheatgrass was applied to the 14 ecological provinces that intersect the Great Basin. The model was applied to sagebrush cover and other vegetation types believed to be susceptible to invasion by cheatgrass. The rule set developed for this cheatgrass model is topographically driven and is based on vegetation cover type, ecological province, elevation, aspect, slope, and occurrence of vegetation on valley floors. Risk was assigned to one of three categories: low, moderate, or high. All susceptible vegetation types were assumed to be at some risk of displacement by cheatgrass; thus, the only areas with no risk were those occupied by other (i.e., non-susceptible) vegetation cover types.

Citations:
Bureau of Land Management. 1999. The Great Basin Restoration Initiative: out of ashes, an opportunity. Bureau of Land Management, National Office of Fire and Aviation, Boise, Idaho. 28 pp.

Bureau of Land Management. 2002. Management considerations for sagebrush (Artemisia) in the western United States: a selective summary of current information about the ecology and biology of woody North American sagebrush taxa. U.S. Department of the Interior, Bureau of Land Management, Washington, DC.

Nachlinger, J., K. Sochi, P. Comer, G. Kittel, and D. Dorfman. 2001. Great Basin: an ecoregion-based conservation blueprint. The Nature Conservancy, Reno, Nevada.

Wisdom, M. J., M. M. Rowland, L. H. Suring, L. Schueck, C. Wolff Meinke, B. C. Wales, and S. T. Knick. 2003b. Procedures for regional assessment of habitats for species of conservation concern in the sagebrush ecosystem. Unpublished report on file at Pacific Northwest Research Station, 1401 Gekeler Lane, La Grande, OR 97850.