Grazing effects on plant cover, soil and microclimate in fragmented woodlands in south-western Australia: implications for restoration

This study investigated the impacts of livestock grazing on native plant sp ecies cover, litter cover, soil surface condition, surface soil physical an d chemical properties, surface soil hydrology, and near ground and soil mic roclimate in remnant Eucalyptus salmonophloia F. Muell woodlands. Vegetatio n and soil surveys were undertaken in three woodlands with a history of reg ular grazing and in three woodlands with a history of little or no grazing. Livestock grazing was associated with a decline in native perennial cover and an increase in exotic annual cover, reduced litter cover, reduced soil cryptogam cover, loss of surface soil microtopography, increased erosion, c hanges in the concentrations of soil nutrients, degradation of surface soil structure, reduced soil water infiltration rates and changes in near groun d and soil microclimate. The results suggest that livestock grazing changes woodland conditions and disrupts the resource regulatory processes that ma intain the natural biological array in E. salmonophloia woodlands. Conseque ntly the conditions and resources in many remnant woodlands may be above or below critical thresholds for many species. The implications of these find ings for restoration of plant species diversity and community structure are discussed. Simply removing livestock from degraded woodlands is unlikely t o result in the restoration of plant species diversity and community struct ure. Restoration will require strategies that capture resources, increase t heir retention and improve microclimate.