PARENT SESSION
Contributed Oral Session 138: Fire and Vegetation Dynamics
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 519 B, Level 5, Palais des congrès de Montréal
A metapopulation model analysis for the fire-killed shrub, Banksia hookeriana, in SW Australia.
Groeneveld, Juergen1, Enright, Neal*,2, Lamont, Byron3, 1 Centre for Environmental Research, Leipzig-Halle GmbH, Germany2 University of Melbourne, Melbourne, Australia3 Curtin University of Technology, Perth, Australia
ABSTRACT- Banksia hookeriana is a fire-killed serotinous shrub restricted to the crests of low sandy dunes in Mediterranean climate type shrublands of the Eneabba Sandplain, South-western Australia. If the time between consecutive fires is too short for populations to produce a sufficient number of seeds for self replacement, or if fire does not recur within the lifetime of the plants, it may go locally extinct. Following local extinction, vacant dunes must be recolonised by long distance dispersal of seeds from populations on other dunes after fires which affect both locations in the same event. We report the results of a metapopulation simulation model that describes the population dynamics and resultant population viability of B. hookeriana in relation to fire regime. The key model processes concern the local extinction and colonization rates in B. hookeriana for a metapopulation comprising 39 dune populations within an area of approximately 12 km2. The local extinction risk is varied within ranges determined from demographic studies and recent reconstructions of the regional fire history using grass trees (Xanthorrhoea species) that propose a controversially high fire frequency regime prior to European settlement of SW Australia which seems incompatible with survival of many fire sensitive woody species. The estimation of colonisation rates is based on the results of genetic analyses of populations from an area on the Eneabba sandplain of the same size as that modelled here. We explore the effect of changes in fire regime (frequency, extent and spatial correlation) on population viability and extinction probability. Long distance colonization allows metapopulation persistence across a broad range of fire intervals. Mean fire interval per dune determines the persistence of the metapopulation rather than the mean fire interval across the whole system due to a positive correlation between the mode of the distribution of fire intervals and the mean size of fires. Nevertheless, results do not support persistence under the pre-European frequent fire scenario proposed by the grasstree fire history.
Key words: metapopulation model, fire frequency, shrublands, Banksia hookeriana