Document: JAY-3-64-39

The effects of burning and grazing on a California grassland plant community.

MARTY, J.*

University of California, Davis, CA 95616 ¹

Abstract:
Prescribed burning and livestock grazing are two management tools often used to maintain species diversity in California's grasslands. These two forms of disturbance are expected to decrease the cover of non-native annual species while promoting native grass and forb species richness and cover. In the field, I studied the effects of prescribed burning and various cattle grazing intensities on a California grassland plant community. In July 1998, a prescribed burn was applied to half of the treatment plots in this experiment. From January through May 1999, cattle grazed the treatment plots at 4 different intensities (ungrazed, heavy rotational, light rotational and continuous grazed). In general, the burn treatment had a much stronger effect on the plant community variables than any of the grazing treatments. Species richness was significantly higher (p < 0.001) in the burned versus unburned treatment plots where the burned plots had an average of 3 more species than the unburned plots. This difference was only detectable at the 400m² scale and not at the 0.0625m² scale. Burning also significantly increased (p = 0.02) average forb cover in the plots. Certain individual species such as Bromus hordeaceus, Trifolium hirtum, Navarretia pubescens and Vicia sp. had higher cover in burned plots versus unburned plots. The burn treatment had an overall detrimental effect on the remnant native bunchgrass (Nassella pulchra) population at the site, causing a significant (p < 0.001) increase in bunchgrass mortality. Species richness was not significantly different among the grazing treatments. Continuous grazing produced a significant decrease in average non-native species cover (p = 0.05), with continuous grazed plots averaging 4% cover of non-native species versus approximately 5% cover for all other grazing treatments. In particular, non-native grass cover was most significantly reduced (p = 0.025) in the continuous grazing plots versus all other grazing treatments.

Keywords: California grassland, diversity, grazing, burning, species richness

This abstract is being presented at: 10:30 AM in session:
Poster Session #12: Disturbance Ecology.