Fire and grazing in a shrub-invaded arid grassland community: independent or interactive ecological effects?

This study examined the response of summer and winter annuals and perennial s in a shrub-invaded arid plant community to combinations of fire and grazi ng by cattle to determine their effects on individual abundances, species r ichness and diversity. Thirteen species differed significantly in abundance across the burn treatment while nine differed significantly across the gra zing treatment. Summer and winter annual plants were significantly more abu ndant, and summer annual plant species richness and diversity were signific antly higher on burn plots. Most species were affected either by burning or grazing indicating that these disturbances affect this plant community rel atively independently. (C) 1999 Academic Press.