Year

2004

Degree Name

Master of Science - Research

Department

School of Biological Sciences

Abstract

Temperate grassy woodlands throughout the world have suffered the effects of changed disturbance regimes, in particular, fire and grazing, due to human activities. Since European settlement fire and tree clearing has been used to modify grassy woodland vegetation for livestock grazing and agriculture. As a consequence some species, particularly shrubs and trees, have been reduced or eliminated and both native and introduced grasses have become more dominant. It is important to understand how disturbance regimes are affecting grassy woodlands to ensure long-term survival and diversity of the community.

The Cumberland Plain Woodlands are a good example of the magnitude of destruction endured by a typical grassy woodland community. They are found in small remnants within the western Sydney region and are severely fragmented and disturbed with approximately only 6 % remaining. The Cumberland Plain Woodlands are listed as an endangered ecological community under the Threatened Species Conservation Act, 1995 and the Environment Protection and Biodiversity Conservation Act, 1999. This listing is a consequence of widespread destruction and fragmentation of the community due to tree clearing, agriculture and urbanisation. Little is known of the effect of changed disturbance regimes on the Cumberland Plain Woodland remnants and other vulnerable communities growing upon shale in western Sydney with most research focussing on the vegetation communities growing upon Hawkesbury Sandstone, which initiated this research.

The study area was located within one of the largest remnants of Cumberland Plain Woodlands, which is found at Holsworthy Military Area, western Sydney. Holsworthy has been part of the army training area for the last 100 years and therefore is isolated from growing urbanisation, agriculture and livestock grazing. The impact of frequent fire is of concern in this area as past management practices were to burn the area regularly to remove vegetation and create an open understorey able to be used for army training activities. Also, small firearms training activities often ignite fires in the woodland due to bullets missing targets and igniting the vegetation. Fires in the area are generally left to burn out without any intervention due to the danger of explosion of unexploded ordnances throughout the training area. High fire frequency and the cessation of livestock grazing at Holsworthy highlighted the necessity to answer the following questions: (i) How do plant species in the Cumberland Plain Woodlands respond to different fire regimes? (ii) How do these plant species respond to grazing by animals other than domestic livestock, such as macropods and rabbits? And (iii) what effect does the heat and smoke from fire have on grass germination?

An exclosure experiment using various fire and grazing treatments was used to answer these questions and determine if the richness and abundance of species changed over a five-year period. Also, a laboratory germination experiment was used to determine how 22 grass species from the Cumberland Plain Woodlands respond to heat and smoke treatments designed to simulate the process of fire.

This study found that (i) past fires affected plant community composition in the Cumberland Plain Woodlands at Holsworthy Military Area, generally reducing the abundance of shrubs relative to grasses, although some particular shrub species were not reduced in abundance, (ii) community composition did not appear to be strongly affected by grazing, and (iii) germination of some grass species was stimulated by heat and/or smoke but germination of others was reduced.

This research indicates that fire is an important and frequent disturbance in the Cumberland Plain Woodlands at Holsworthy Military Area. Understanding the current fire regime is necessary to determine appropriate management strategies to ensure the survival of the Cumberland Plain Woodlands and other grassy woodland communities. This project enhances the research and monitoring component of the Plan of Management for the recovery of the Cumberland Plain Woodlands, Holsworthy Military Area. It highlights the need for landscape heterogeneity to maintain survival and diversity of the community and increases the knowledge of the effect of heat and smoke from fire on the germination of grasses in grassy woodlands.

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