Post-fire succession during the long-term absence of fire in coastal heathland and a test of the chronosequence survey method

Post-fire vegetation succession in long-unburnt heathland in south-east Australia is not well understood. In the present study we investigated temporal change in vegetation along a 37-year post-fire chronosequence in coastal heathland in the Gippsland Lakes Coastal Park, Victoria, Australia. Fourteen sites were surveyed for vegetation characteristics approximately 10 years after an initial chronosequence survey, enabling an extension of the chronosequence to cover a longer fire-free interval as well as testing predictions of declining species richness and diversity from the initial chronosequence study. Total species richness, mean species richness, mean diversity and mean evenness declined with time since fire across the 14 sites. However, only diversity (H) and evenness (E) decreased within sites as predicted in the original chronosequence study. No decrease in species richness within sites was observed. The chronosequence correctly predicted changes in species abundance but not the number of species present. Tree cover also increased, suggesting that the heathland was becoming a woodland in the long-term absence of fire. Fire history, which is an uncontrolled historical factor, provides the most likely explanation for why species richness did not decrease as predicted by the initial chronosequence. This study advocates caution in using the chronosequence method to predict species richness during post-fire succession.