PARENT SESSION
Oral Session #99: Grazing.
Presiding: T. Arredondo
Friday, August 9. 9:00 AM to 12:00 PM. Graham Meeting Room, TCC.
Cattle grazing impacts on California coastal prairie and associated wildflowers over a broad geographic range.
Hayes, Grey*,1, Holl, Karen1, 1 University of California, Santa Cruz, CA
ABSTRACT- California coastal prairie evolved with disturbances such as ungulate grazing and fire. In the last 300 years, cattle have become a dominant component of disturbance regimes and non-native species have increasingly dominated these grasslands. In spring of 2000 and 2001, we investigated the impact of cattle grazing on the coastal prairie plant community with a focus on native annual dicots through a survey of 25 paired grazed and ungrazed sites over a 670 km range of the ecosystem. Plant community data were collected using the pin intersect method at one meter intervals along five 50-m transects. Cover of all native annual dicots was measured within one meter wide belt transects centered on line transects. Vegetation height, soil depth, and litter depth were measured along line transects and wherever native annual dicots were encountered. Soil samples from each site were analyzed for texture and major nutrients. Results indicated that native annual dicot species richness and cover were higher in grazed sites, and this effect was concomitant with decreased litter depth and vegetation height. Soil properties explained little of the variation. Non-native annual monocot and dicot cover were higher in grazed sites. Native monocot cover did not differ in grazed and ungrazed sites, but cover of native perennial dicots was lower in grazed sites. These results implicate the need for targeted restoration of disturbance regimes to maintain different guilds of species.
KEY WORDS: cattle grazing, California coastal prairie grassland plant diversity, disturbance ecology, invasive exotic plants