Drivers of tree community assembly during tropical forest post-fire succession in anthropogenic savannas

In the context of global change, tropical forests are increasingly affected by fires. Understanding the ecological processes driving forest recovery in fire-modified landscapes is a critical issue. We analyzed spatial and temporal (8 years) changes in functional and phylogenetic composition of tree communities during forest post-fire recovery in anthropogenic savannas. We used null models to infer the main assembly processes driving forest succession along three 90-m transects running from an advancing savanna forest edge to forest interior in New Caledonia. We also evaluated if successional changes differed between large and small trees, or depended on the demography of remnant savanna trees. We found coordinated shifts from drought-and fire-resistance towards shade-tolerance strategies, involving leaf, stem, and architectural traits along transects. Our results indicate stronger environmental filtering and faster temporal changes in composition of young edge communities. In forest interior, our results suggest slower compositional changes, with an important role of light limitation in community assembly. These non-random patterns depended on both the decline of savanna trees and compositional changes among forest species. We also found contrasting community patterns depending on tree size, supporting a stronger influence of environmental filtering on small trees. Our work emphasized the dominance of deterministic assembly processes driving tropical forest post-fire succession. Our study suggests that fire and drought drive environmental filtering during early succession at the forest edge, entailing constraints on multiple functional dimensions. As succession progresses, light limitation becomes a stronger driver of community assembly, and community composition becomes more stable in time. Our study provides insights for a better understanding of the processes guiding tropical forest succession in the particular context of post-fire forest recovery.

Automated summary

In the context of global change, this study analyzed the ecological processes driving forest recovery in fire-modified landscapes by studying changes in functional and phylogenetic composition over 8 years. Environmental filtering and light limitation were found to be major drivers of community assembly, with faster changes at the forest edge compared to the interior. The study highlighted deterministic assembly processes in tropical forest post-fire succession, with fire and drought driving environmental filtering during early succession.