CORVALLIS, Ore. A new study suggests that overgrazing and other factors increase the severity of cheatgrass invasion in sagebrush steppe, one of North America's most endangered ecosystems.
The research found that overgrazed land loses the mechanisms that can resist invasion. This includes degradation of once-abundant native bunchgrasses and trampling that disturbs biological soil crusts. The work was published today in the Journal of Applied Ecology by researchers from Oregon State University, Augustana College and the U.S. Geological Survey.
"We think there are ways to assess the risks these lands face to reduce the impact of cheatgrass invasion," said Paul Doescher, professor and head of the OSU Department of Forest Ecosystems and Society, and co-author on the study.
"In the future we should work cooperatively with ranchers and land managers to promote a diverse sagebrush and bunchgrass ecosystem," Doescher said. "That type of community will protect the native plant and wildlife species and benefit sustainable rangeland use at the same time."
Researchers suggested that one of the most effective restoration approaches would be to minimize the cumulative impact of grazing, by better managing the timing, frequency of grazing and number of animals.
The researchers also determined that, contrary to some previous suggestions, grazing does not reduce cheatgrass abundance. Cheatgrass was found by this study to be extremely tolerant of even intensive grazing, and the findings "raise serious concern" about proposals to use cattle grazing to help control its spread in areas where native bunchgrasses still persist.
The study outlines the complex ecological processes that can promote cheatgrass invasion and the indirect role overgrazing plays in that process. Increasing gaps and connection of gaps between once-abundant native bunchgrasses allow "a dramatic increase" in cheatgrass invasion, the study concluded.
|Contact: Paul Doescher|
Oregon State University