Forb responses to grazing and rest management in a critically endangered Australian native grassland ecosystem

Abstract

Worldwide, temperate grasslands have been extensively cleared for agriculture and urban expansion and the ‘Natural Temperate Grassland of the Victorian Volcanic Plain’ in south-eastern Australia has recently been listed as critically endangered. Because of land clearing, these grasslands now occupy <1% of their original distribution and much of the remaining grassland continues to be grazed by livestock. Although forbs (wildflowers) constitute most of the floristic richness in natural grasslands, few experimental studies have focused on their responses to strategic livestock grazing and rest. This paper reports on the outcomes of five grazing and rest management regimes imposed for 4 years at three sites on the Victorian Volcanic Plain. Seasonal grazing and rest management regimes resulted in significantly different native and exotic forb frequencies, but not richness. Native perennial and exotic annual forb frequency was higher when management incorporated grazing and rest periods (14 and 16% deviance explained), particularly with spring rest from grazing. However, the most important influence on native perennial and exotic annual and perennial forb frequency (46, 58 and 41% deviance explained) and native perennial and exotic annual species richness (62 and 35% deviance explained) was site. Differences among the three sites included soil, rainfall, size of remnant, presence of small burrowing mammals, management history and consequent species assemblages. Despite differences among sites, the results indicate that native perennial forb frequency may be increased using management regimes that incorporate both grazing and rest. However, targeted management may be necessary to reduce exotic annual forbs, also promoted by grazing with seasonal rest.