A closer look: decoupling the effects of prescribed fire and grazing on vegetation in a ponderosa pine forests

Abstract

Scientists have had little information about how prescribed fire and cattle grazing—common practices in many Western ponderosa pine forests—affects plant abundance and reproduction in the forest understory. Pacific Northwest Research Station scientists began to explore how these practices affect vegetation in a five-year study of postfire vegetation in eastern Oregon ponderosa pine forests where cattle have been routinely pastured from late June or early July through early to mid August. For this area of eastern Oregon, they found that excluding cattle grazing during peak growing season increased native plant cover and grass flowering capability in ungrazed areas compared to grazed areas. Because vegetation was measured prior to releasing cattle on the land, the study's results tend to reflect lasting grazing impacts rather than simple consumption.

Findings indicate that excluding cattle in areas that had been exposed to long-tem grazing had more effect on vegetation than reintroducing fire to the landscape. Neither spring nor fall burning increased native perennial plant cover or the number of plant species present; spring reburns reduced sedge cover and fall reburns promoted early successional plant communities that included invasive species. This study is the first look at vegetation effects; a 10-year evaluation of the same plots is planned for 2012.

Citation

Kerns, Becky K.; Oliver, Marie. 2012. A closer look: decoupling the effects of prescribed fire and grazing on vegetation in a ponderosa pine forests. Science Findings 141. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 6 p.