Impact of fire on invertebrate communities in mallee-heath shrublands of southwestern Australia

Abstract

A three-year study (1989?92) of the responses of invertebrates to fire was carried out in mallee-heath shrublands in the Stirling Range National Park, Western Australia. Abundances were measured at the Order level for major groups, and at the morphospecies level for Coleoptera. Changes in floristics and vegetation structure were monitored over the same period. At the Order level, variation in abundances was attributable more to locality, seasonal and year-to-year effects than to fire. Responses of beetles at the morphospecies level, however, reflected changes due to fire as well those attributable to season and year. Coleoptera and Diptera were most abundant 40 years after fire, Hemiptera and Orthoptera peaked in earlier seral stages, while Hymenoptera and Araneae showed relatively few fire-related trends. Coleoptera and Diptera best reflected changes due to season, year and fire, and together with some Araneae such as mygalomorph spiders, would most likely be suitable groups to consider in future studies. Multivariate analyses indicated that classification to morphospecies level is essential to elucidate changes due to fire. These analyses also indicated that changes in invertebrate abundance and composition did not accord with changes in floristics or vegetation structure. Each set of data therefore represents different facets of change over time, including those due to fire. Comparing our data with contemporaneous information collected in upland areas of the Park indicates that there is a clear dichotomy in the fire sensitivity of species inhabiting the wet gullies and thickets of the mountains and those occupying the seasonally dry lowland mallee-heaths. Fire management strategies need to take account of this dichotomy by protecting relictual fire sensitive species and habitats.