James Cook University, Townsville

Alan Petersen

1997

The spread of woody weeds across savanna rangelands is a global problem. In Queensland, A. nilotica (prickly acacia) is a major threat to much of the Mitchell grass downs, a natural ecosystem that encompasses 21.9 million hectares and supports a large pastoral industry.

Approximately seven million hectares are already infested to varying degrees. It was predicted, on the basis of suitability of climate, that the potential distribution of A. nilotica includes the majority of Queensland, the Northern Territory and much of Western Australia.

A. nilotica, with its high nitrogen content, acts as a feed supplement and increases the ability of livestock to consume low-quality grass (Barker 1995). However, the loss of ground cover has repercussions for soil conservation. Most research on A.nilotica focused on chemical, mechanical and biological control methods that are expensive and often ineffective.

Proactive weed management requires knowledge of the responses of weed populations under different environmental conditions before they occur. The quantification of factors that affect recruitment and mortality, such as seed germination and seedling establishment, is essential for the successful performance of any predictive model. This research is contributing to predictive models of population dynamics that are presently being developed by CSIRO.

Supervisors

Dr Joel Bown, University of New Mexico
Dr Joe Holtum, JCU