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 c ommonly regarded as essential for restoration of degraded systems. However, these shrubs have become a dominant and stable component of many mulga lan d ecosystems, and their removal may have unknown ecosystem impacts. This pa per reports an experiment to determine the effect of woody weeds and grazin g pressure on grass recruitment, cover and diversity in two vegetation comm unities in Queensland's mulga lands. Both factors influence grass recruitme nt, cover and diversity, but the response differs between the two vegetatio n communities investigated. The overall grass cover is consistently greater in sites where woody weeds were removed, and where grazing pressure was lo west. However, in the Dunefields community the cover and frequency of grass plants responded mon to the removal of woody weeds than in the Mulga Sandp lain community. In contrast, in the Mulga Sandplain community the grasses r esponded more to reducing or removing grazing pressure. Results suggest tha t subtle differences between systems influence grass dynamics, highlighting the need for community-specific research and management.