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Data from: Shifts in functional group community diversity of threatened mesic forests with changing fire regimes

Paroissien, Ruby12; Tangney, Ryan31; Thomsen, Alexandria1; Offord, Catherine21; Ooi, Mark1

Published Aug 12, 2025 on Dryad. https://doi.org/10.5061/dryad.ngf1vhj59

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Abstract

Changing fire regimes, including increased fire severity, may impact plant community recovery, altering structure and composition, potentially causing a state change. For threatened wet sclerophyll forests, mesic forests which contain both dry sclerophyll and rainforest elements, this could mean a shift to a more fire-prone species composition. We investigate how species and functional group diversity responses differ across a gradient of fire severity and how recovery changes with time since fire in a mesic forest community. We hypothesize that increased fire severity can lead to reduced diversity and altered composition. We surveyed plant species cover and abundance three years post-fire at sites with different fire severities (moderate, high, or extreme) during the 2019/2020 Australian megafires, and sampled adjacent unburnt sites as controls. We calculated species and functional type beta diversity indices across a fire severity gradient. Our data showed a hump-shaped relationship between plant diversity and fire severity three years post-fire. Species richness was highest at moderately burnt sites and lower in unburnt and extremely burnt sites. Species composition also differed, with unburnt sites containing more rainforest-restricted species. Increased fire severity may reduce community-level diversity. The distinct compositional difference between recently burnt and long-unburnt sites suggests how fire regimes may drive shifts in wet sclerophyll forest states. The differences identified three years post-fire indicate that recovery may be slow, with extremely burnt sites potentially taking the longest.