| California's grasslands have been dramatically altered over the past 250 years as a result of domestic livestock grazing, the introduction of exotic plant species, suppression of grassland fires, and conversion of grassland for agricultural and commercial development. Although the precise community composition of the pre-European native grassland is not known, there is speculation that native grasses were an important component of the grassland ecosystem. Grassland restoration efforts in California's Central Valley have focused on the restoration of native perennial grasses into the grassland. Grazing and prescribed fire are management tools often used to promote and restore native species in these grasslands.; The influence of reduced competition (herbicide spraying) and various intensities of cattle grazing on a restored population of purple needlegrass or Nassella pulchra (Hitchc.) Barkworth were studied in the field at Beale Air Force Base (BAFB), Yuba County, CA. Spraying increased the size and reproductive output of N. pulchra regardless of grazing intensity while grazing decreased the reproductive output of the grasses. Although all reproductive bunchgrasses produced viable seed each year, only two seedling recruits were found around parent plants at the end of the experiment. Because native grasses like N. pulchra are long-lived, successful seedling establishment every year may not be necessary for long-term population viability.; The effects of various intensities of cattle grazing and late-spring burning on a grassland plant community including a remnant population of N. pulchra were also studied at a field site on Beale AFB. Burning significantly increased mortality of N. pulchra adults while grazing reduced the height and reproduction of the bunchgrasses. All measured bunchgrass variables peaked in 1998. This was attributed to above average rainfall and below average temperatures experienced late in the growing season in that year.; Grazing and burning strongly affected the species composition in this community. Late spring burning increased species richness across all functional groups, but the significance and magnitude of the increase was scale-dependent. This study supports the use of late-spring burning as a tool for increasing native species cover and richness in grasslands. Grazing at the levels used in this study had a neutral effect on species composition. |
