Effect of fire retardant application on heathland surface-dwelling invertebrate communities in Victoria

Abstract

Summary The effects of the application of fire retardant at varying rates on surface-dwelling invertebrates at ordinal and sub-ordinal level in heathland communities were assessed over a one-year period from March 2001 to March 2002. The study was conducted at two sites, one in East Gippsland at Mario and the other in the Grampians region of south-western Victoria where a total of 136 190 specimens representing 30 ordinal and sub-ordinal taxa contained in 5400 pitfall trap samples was collected. It was concluded that despite the application of fire retardant at varying rates, there was no significant effect on invertebrate activity at ground level amongst the ordinal groups Acarina and Dermaptera. These ordinal groups appear to form a stable component of the heathland invertebrate community at both sites. Although significant changes were observed in other major taxonomic groups (total taxa, total insects, total non-insects, Araneae, Collembola, Coleoptera and Diptera) these changes were confined to either increased or decreased activity within a single plot and were judged to be not representative of treatment. While a significant change in activity was recorded for Formicidae at both sites, this was also due to single-plot variations in activity across different treatments. Such information indicates that any significant changes observed in invertebrate activity appeared to be due to site-related environmental factors rather than the effects of the retardant itself. When assessed in terms of general diversity, taxon richness and community evenness, ordinal and sub-ordinal taxa were unaffected by retardant application at the Mario site. Significant changes in insect diversity at the Grampians site were again due to site-related factors rather than retardant effects. Further study is required to determine whether this stability is reflected at family, genus and species level, and if there are any seasonal and longer-term effects of retardant application. The combined effect of fire and retardant on invertebrate communities also requires further study.