Abstract In fire‐prone ecosystems, reintroducing fire following long‐term exclusion can restore ecosystem function and biodiversity. In some situations, repeated burning might be necessary to reduce invasive species and promote native plant re‐establishment, but this strategy rests on the assumption that residual seedbanks persist following fire. We assessed the impact of a low‐intensity prescribed fire on the below‐ground germinable seedbank, relative to the above‐ground plant community in subtropical grassy woodlands of southeast Queensland, Australia. Nine months after fire, we surveyed groundcover species along 10 transects (five burnt, five unburnt), each with three 1 m 2 quadrats (30 total). Soil samples were collected from three adjacent 1 m 2 quadrats (30 total) and species in the soil seedbank were identified during a 5‐month greenhouse emergence trial, concluding when new germination slowed. We analysed species richness (α diversity), community uniqueness (β diversity) and community composition in 13 trait groups (based on origin, life span, growth form and N fixation) in response to ‘fire’ (burnt vs. control) and ‘position’ (above‐ vs. below‐ground). There were no effects of fire on species richness of any group, either above‐ or below‐ground. There were significant effects of position on richness in all functional groups except exotic grasses. Below‐ground seedbanks had more than double the number of species, compared to above‐ground vegetation (e.g. an average of 27 vs. 11 species per m 2 on unburnt sites). Above‐ground vegetation had higher levels of uniqueness than below‐ground seedbanks, and there were no notable effects of fire on β diversity in any functional group. Partitioning β diversity showed that above‐ground communities were structured by species replacement and below‐ground seedbanks by richness agreement. Seedbanks were compositionally dissimilar to above‐ground plant communities (effect of position on one Principal Component (PC1), p < 0.001) and composition was unaffected by fire. Policy implications : Seedbanks in this grassy woodland provide a rich biodiversity reservoir which persisted after low‐intensity fire. Patterns of species replacement suggest that activities which diminish above‐ground plant diversity (such as overgrazing or conversion to forest) will impact biodiversity at larger spatial scales, while soil seedbanks are likely more robust to localised disruptions. Read the free Plain Language Summary for this article on the Journal blog.
Gaskell et al. (Fri,) studied this question.