• Rocky Mountain Research Station
• 240 West Prospect
• Fort Collins, CO 80526
• (970) 498-1100

Changes in Great Basin Sagebrush and Woodland Ecosystems

Across the Great Basin settlement related activities and climate change resulted in woodland expansion that began within the 1880's across the region. The reduction of fine fuels by livestock grazing and other land use practices, and the associated reduction in the frequency, and a change in the extent and patterns of fire, are the primary drivers in this expansion of the woodlands. The reduction in shrub and herbaceous vegetation that accompanied increasing tree dominance has also contributed to past declines in fire frequency. However, the steady increase in the level of tree dominance across increasingly more area is now driving an increase in both the amount and continuity of the fuel contributed by the trees across the landscape. These fuel loads have doubled over the last century and can be expected to double over the next 50 years. This has serious implications for the severity and extent of future fires in the Great Basin.

The loss of the sagebrush community species that follows the increasing tree dominance, combined with the intense crown fires that are now increasingly occurring, are helping to push many of these sites into dominance by exotic annuals. Once they are present, exotic annuals such as cheatgrass are resulting in the widespread degradation of both sagebrush ecosystems and pinyon-juniper woodlands. This is dramatically changing the successional patterns that follow fire. This can include the permanent loss of the sagebrush ecosystems that once existed there, and the wildlife habitat and livestock forage they once provided. As areas invaded by the trees become increasingly tree dominated, treatment to retain or restore the original sagebrush ecosystems becomes more difficult and expensive.

An ongoing Joint Fire Sciences Program funded project is developing a basic understanding of the causes and effects of tree expansion, increasing tree densities and cheatgrass invasion on sagebrush ecosystems and associated pinyon-juniper woodlands. Results will be used to devise techniques for restoring and maintaining sustainable sagebrush ecosystems and pinyon-juniper woodlands. Techniques under evaluation include the use of prescribed fire as a restoration tool and the identification of plant species and seeding methods for restoring these native communities. Collaborative research efforts supported by the Joint Fire Sciences Program are under way across the Great Basin for illustrating the ecological response of watersheds experiencing tree expansion to the use of prescribed fire and mechanical treatments to control tree dominance.