Wildfire or mosaic fires? Impacts on beetles in South-West Australia

Paul Van Heurck *1

1 Curtin University of Technology, Department of Environment and Agriculture, Perth, Australia.

In March 2003 an intense wildfire burnt approximately 20,000 ha of southern jarrah forest and heathland plains, near the south coast of Western Australia. The rapid southward spread of the fire was largely halted at the northern boundary of London forest block, patchily prescribed burnt in the spring of 2002. In 2004 a study was established to compare fire impacts on the beetle (Coleoptera) species representing roughly 20% of invertebrate richness. My PhD tested standardized  metrics for monitoring changes in beetle biodiversity  using a protocol which: 1) collected an inventory of  460 morphospecies over six years; 2) determined spatial autocorrelation effects of  pitfall-trapping, with lower beetle richness in single forest patches; 3) compared fire impacts on the distinctiveness of the beetle fauna of the litter microhabitat; 4) used pitfall-trapped sites to compare the complementarity of beetles in these fire regimes; and 5) quantified the  productivity of beetle trophic guilds. Total study richness is partitioned amongst 232 common beetle species and 228 singleton or rare species, of which 105 only occurred in patchily, mosaic burnt sites, while 68 species were exclusive to wildfire burnt sites. This ratio of complementarity within the rare beetle fauna reinforces the need to use mosaic fire at landscape scales to establish heterogeneity of post-fire ages at a fine-grained scale within individual forest and vegetation patches in southern Western Australia.

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