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

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.