This project represents the first national study of tree decline caused by reduced frequency or absence of fire. In NSW, Victoria, WA and Tasmania there are large tracts of native moist to dry forest in advanced stages of decline. In some instances there is strong evidence linking this decline to change in fire management, from historically frequent low intensity burns to a current management of fire exclusion. The project will concentrate on testing the following hypothesis:

• Exclusion of fire from regrowth forests is leading to dense understorey and litter development, which changes soil and microclimatic conditions.
• The decline efficiency of eucalypt roots in altered surface soil conditions below a dense understorey is associated with elevated nitrogen status and altered microbial communities (particularly mycorrhizal associations).
• Declining root vigour induces stress as water demand increases with increasing transpirational capacity of the forest. Resulting changes in physiology and nutrition increase the susceptibility of trees to pathogens and pests.
• Any adverse factor such as drought, fungal infection or other pest attack reinforces the physiological changes and contributes to their irretrievable decline. Paradoxically, unhealthy trees become more susceptible to drought stress than corresponding understoreys that are favoured by fire exclusion.

Suitable study sites have been identified in NSW, WA and Tasmania where the same forest type occurs as long unburnt stands adjacent to sites where there are good records of frequent burning.

Research is lead by Dr Neil Davidson from the University of Tasmania in partnership with State Forests NSW, University of NSW, Conservation and Land Management WA, Murdock University WA, Tasmanian Fire Service, Forestry Tasmania, Department of Tourism, Parks, Heritage and the Arts Tasmania, and University of Melbourne.

Contact: Dr Neil Davidson Private Bag 55, Hobart 7001 Tasmania, email Neil.Davidson@utas.edu.au