Grass response to shrub removal in two semi-arid vegetation communities.

The control of woody weeds in the mulga lands of south-west Queensland is commonly regarded as essential for restoration of degraded systems. However, these shrubs have become a dominant and stable component of many mulga land ecosystems, and their removal may have unknown ecosystem impacts. This paper reports an experiment to determine the effect of woody weeds and grazing pressure on grass recruitment, cover and diversity in two vegetation communities in Queensland's mulga lands. Both factors influence grass recruitment, cover and diversity, but the response differs between the two vegetation communities investigated. The overall grass cover is consistently greater in sites where woody weeds were removed, and where grazing pressure was lowest. However, in the Dunefields community the cover and frequency of grass plants responded more to the removal of woody weeds than in the Mulga Sandplain community. In contrast, in the Mulga Sandplain community the grasses responded more to reducing or removing grazing pressure. Results suggest that subtle differences between systems influence grass dynamics, highlighting the need for community-specific research and management. Key words: shrub removal, semi-arid vegetation, vegetation communities, woody weeds