PARENT SESSION
Oral Session # 55: Resource Management II: Terrestrial Systems.
Presiding: E Latty
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 106.
A population model of a perennial shrub threatened by disease and adverse fire regime.
Regan, Helen*,1, Keith, David2, Tozer, Mark2, 1 San Diego State University, San Diego, CA, USA2 New South Wales National Parks and Wildlife Service, Hurstville, NSW, Australia
ABSTRACT- Xanthorrhoea resinifera is a long-lived plant occurring on the south-east coast of Australia. Like many perennial Australian shrubs, X. resinifera has a complex relationship with fire. Fire reduces the chance of survival of plants whilst triggering flowering and seed production. Populations of X. resinifera are subject to a range of threatening processes. While Xanthorrhoea may survive bushfires, such survival is highly structured in relation to plant size and fire intensity and frequency. Furthermore, Xanthorrhoea species are susceptible to the root pathogen Phytophthora cinnamomi which reduces survival of established plants. The long-term effects of these threats is poorly understood. We constructed a stochastic, individual-based model using 10 years of demographic data to investigate the effects of an altered fire regime and disease on the long-term persistence of sub-populations of X. resinifera. We included density-dependent processes with con-specific neighbors as well as shading by neighboring Banksia plants. We demonstrate that the chance of long-term persistence depends on the timing of fire and the extent of disease. We show that, even though fire does not eradicate the pathogen, the increased seed production and recruitment following a fire may somewhat alleviate the increase in mortality due to disease. In this way, fire could be an important management tool for this species.
Key words: individual-based model, population viability analysis, disease, fire