Long term effect of fire, flood and grazing on invertebrates in Australia’s arid zone: Collembola and Formicidae

An extensive fire followed almost immediately by a large scale flood occurred in the semi-arid/arid Olary Creek area in southwest New South Wales. In order to monitor the short and long term effect of these extreme events on vegetation, replicate paired plots were established in the flooded, burnt, and both flooded and burnt landscapes. The plots were 25 m square and one pair of each plot was fenced to exclude grazing animals. We report here on the long-term effect of this disturbance on terrestrial and arboreal invertebrates thirteen years after the events, using Formicidae and Collembola as exemplars. Our results showed that abundance and species richness of both Formicidae and Collembola were more affected by vegetation on the plots and only indirectly by impacts, while the vegetation was determined by the impact history on different land units. Perennial native grasses were favoured by the flooding and rainfall resulting in a high abundance of species in the genus Corynephoria (Collembola: Symphypleona) mainly on swales, while Formicidae species were trapped in highest numbers where the dune vegetation of hummock grassland (Triodia scariosa) was abundant on control plots and plots affected by fire. Grazing had little effect on these invertebrates. These results suggest that optimal management of invertebrate biodiversity in the region needs a mosaic of strategies with both fire and flood providing benefits.