Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Response of grassland vegetation on Santa Cruz Island to removal of feral sheep.

Abstract

We measured biomass and frequency of herbaceous species before and 12 years after removal of feral sheep from a grassland on Santa Cruz Island, California. Native grasses, especially Stipa spp., increased dramatically following sheep removal whereas all exotic grasses except Avena spp. decreased, probably reflecting the competitive ability of native grasses as well as differential vulnerability to grazing. Native forbs showed a mixed response, with some species increasing but many decreasing, perhaps because some native forbs benefit from grazing. Almost all exotic forbs decreased, likely because these species benefit from herbivores and their activities. Our results provide encouraging evidence that an island grassland dominated by exotic species has the potential for recovery from severe overgrazing.