The fire regime can be considered as the combination of fire type, frequency, intensity, and season of burning through time. In fire-prone ecosystems, plant species exhibit a range of traits which allow them to persist under certain fire regimes. Two important fire-response traits are resprouting and regeneration from seed. Resprouters and seeders coexist within plant communities, but their relative proportion varies. The community composition of fire-response types can be altered by changes to the fire regime which promote or reduce species with particular traits. However, other factors also influence the success of species with certain traits, and the relative importance of the fire regime remains unclear. This research aimed to investigate the relative importance of fire regimes, habitat characteristics and resource gradients in determining plant community composition across a mountainous ecosystem of south-eastern Australia. Community composition was calculated as the proportion of species with particular fire-response traits, including resprouting ability, post-fire seed regeneration and seed bank characteristics. Trait data was collated from five different sets of pre-existing post-fire monitoring surveys. The relationships between the proportion of different fire-response types and the local fire regime, habitat characteristics and resource gradients were investigated using logistic regression.
Results/Conclusions
The final models unexpectedly showed that the proportion of fire-response types depended on the collector of the original trait data, as some traits were over- or under-represented in the different surveys. Overall, several seeder types were in higher proportion on rock outcrops and at sites burned with one short inter-fire interval of under 6 years, and were negatively associated with understorey cover. Many resprouting types were in higher proportion at sites without permanent water. Woody resprouters increased at sites that had experienced no short intervals. The results depended on the particular combination of traits chosen; for instance, whether or not seed bank traits were included. The differences between the trait data sources suggest that improved standardisation of species’ fire-response classifications may be needed. The influence of the fire regime was mostly limited to the interaction between short intervals and woody species, with other factors often of greater significance. Less clear are the mechanisms driving these patterns, particularly as resource availability and habitat characteristics are often intertwined with the fire regime. At least three mechanistic models can be invoked to explain these patterns. Further elucidation of these mechanisms will improve both our understanding of trait-environment relationships and management of fire-prone vegetation.
