Ecology of Sagebrush Systems
Is there too much sagebrush or not enough?
Sagebrush lands are a topic of debate among scientists. Some believe fire suppression and overgrazing by livestock have allowed sagebrush to expand its range and invade grasslands since European settlement. Others point to evidence such as the journals of pioneers in the 1800’s who described a “sea of sagebrush,” and conclude that sagebrush is where it always was. The debate over how much sagebrush was present at the time of European settlement may continue, but there is no argument that the sagebrush land type across the Great Basin is now rapidly disappearing due to non-native plant invasion, woodland encroachment, and wildfire.
Healthy sagebrush ecosystems consist of a diverse plant and animal community. Approximately 90 bird species and more than 85 mammals use sagebrush lands for cover and food sources. Birds that require sagebrush for survival include the Greater sage-grouse, sage sparrow, sage thrasher, Brewer’s sparrow, and green-tailed towhee. Research has shown that these birds need approximately 20-36% sagebrush cover – that is, the percentage of area covered by sage plants when viewed from directly overhead – in the plant community. Some research has shown that sage-grouse prefer areas with up to 50% sagebrush cover. Pygmy rabbits and sagebrush voles, mammals dependent on sagebrush habitats, also seem to prefer up to 50% sagebrush cover. While these animals need sagebrush to survive, they also depend on other plants found in these ecosystems. For example, adult sage-grouse eat large amounts of sagebrush, but sage-grouse chicks require other foods, such as understory plants and insects. A balanced plant community of sagebrush and other native plants provides the best habitat for wildlife.
Currently, there is a lack of information to answer the question, “What is the best amount percentage of sagebrush cover?” SageSTEP research will provide more information to answer this question by studying land management options, such as prescribed fire, mechanical thinning, and herbicide application to change the amount of sagebrush cover and observe the effects.
This research will help answer questions like:
- When trees are removed from sagebrush ecosystems, do sagebrush and native grasses increase and create better habitat for birds?
- Does thinning of thick sagebrush encourage growth of native understory plants and make it harder for cheatgrass to invade the area?
SageSTEP Project Co-coordinator
Department of Fisheries and Wildlife
Oregon State University
Corvallis, OR 97330