Herbaceous Responses to Livestock Grazing in Californian Oak Woodlands: A Review for Habitat Improvement and Conservation Potential

Livestock grazing effects on herbaceous vegetation diversity and ecosystem function are summarized from peer-reviewed literature. Ecosystem responses are linked to grazing management via residual dry matter (RDM), which is alternatively called litter or mulch. Residual dry matter is the dead herbaceous aboveground biomass remaining on a site at the time of autumn germination in annual grassland and oak woodlands. RDM is known to play an important role in nutrient cycling, soil erosion prevention, and herbaceous species production and composition the following year. Minimum RDM guidelines are used to ensure forage sustainability and protect ecosystem resources. Recent work has indicated that maximum RDM standards may be necessary to meet wildlife habitat requirements at both site (for example, burrowing owls) and landscape (for example, kit fox) scales and may be useful for fire-fuels management. Livestock grazing can be a useful conservation tool because managers can control the type, abundance, and spatial and temporal distribution of grazers to meet desired goals. Furthermore, political and economic considerations are rendering prescribed fire, hand mowing, and large native herbivore reintroduction increasingly difficult tools to apply. We review herbaceous vegetation responses to grazing management so that they might be translated to advantages and disadvantages for specific ecosystem and habitat conservation goals on a case-by-case basis.