Alison O'Donnell - PhD student

School of Plant Biology (M090) 
University of Western Australia
35 Stirling Highway
Crawley WA 6009
AUSTRALIA

telephone:  +61 8 6488 7923
fax:           +61 8 6488 7925
email:         odonnell@graduate.uwa.edu.au 

B.Sc. (Botany and Geography), Hons. (Botany)

PhD Thesis:  Fire and vegetation patterns in semi-arid southern Western Australia

Supervisors: Dr Pauline Grierson (UWA), Dr Lachie McCaw (DEC), Dr Matthias Boer (UWA), Dr Li Shu (DEC)
Funding: Bushfire CRC Programs B1.1 and B4.2
Commenced: February 2006

Extensive areas of semi-arid woodland and shrubland occur in a relatively undisturbed state at the eastern margins of the southern Wheatbelt in southern Western Australia. Much of this land is unallocated Crown Land and is subject to only minimal intervention for fire management. Anecdotal evidence suggests that the incidence of human-caused fires in this area is low, however, lightning storms are common during the summer months, and extensive wildfires are known to occur every few years. Wildfires have been observed to burn for months at a time with their spread largely dictated by previous burn history, vegetation distribution, natural barriers such as salt lakes, and limited chaining and back-burning along the interface with farming properties. Frequent fires in these areas are thought to be responsible for apparent structural changes in areas of Eucalyptus woodland from single-stemmed woodlands to mallee-like shrublands. Very little is known of the fire history and its biological consequences within the semi-arid woodlands of southern Western Australia.

This project will focus on understanding the spatial heterogeneity created by wildfire within the Lake Johnston area in southern Western Australia by re-constructing the historical fire regime, examining mechanisms that control fire boundaries and in turn, examining the role of fire in determining vegetation type boundaries, and assessing impacts of repeated wildfires on the structure of Eucalyptus woodlands.

Objectives

• Determine the fire history (i.e. fire boundaries and frequencies) within the Lake Johnston area since the ~1950s using aerial photographs and satellite images.

• Examine the distribution and age structure of Callitris spp. stands to confirm the occurrence of fires and their associated boundaries.

• Assess whether fire boundaries coincide with landscape features and / or changes in vegetation type and whether there are differences in floristic characteristics between long unburnt and frequently burnt areas.

• Investigate the hypothesis that frequent fires may change single-stemmed Eucalyptus woodlands to mallee-form woodlands.

Significance

Very little is known of the fire ecology of the Lake Johnston area, hence, this project will provide critical fire history information for this area. This project will also contribute knowledge of landscape-scale fire disturbance which will provide a basis for investigating impacts of fragmentation on fire regimes in adjacent areas of the wheatbelt. The data and conclusions drawn from this project will enhance the knowledge base, and contribute towards the development of scientific expertise relevant to fire management in semi-arid landscapes.

Presentations

O’Donnell, A., McCaw, L., Boer, M. and Grierson, P. 2007 Reconstructing the fire history of an unmanaged semi-arid landscape using remote sensing and dendrochronology, The joint AFAC / Bushfire CRC Conference, Hobart, Tasmania, 19-21st  September 2007

O’Donnell A, McCaw JL, Boer MM, Li S, Grierson PF 2007. Reconstructing the fire history of an unmanaged semi-arid landscape: Lake Johnston Region, WA. Ecological Society of Australia. Adapting to Change: Society - Environment - Science. Perth, 25-30 November 2007.  Oral Presentation (Australian Flora Award for Best Oral Paper Presentation by a student).

Related Links

Bushfire CRC
Department of Environment and Conservation