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

International audienceIn the context of global change, tropical forests are increasingly affected by fires. Understanding the ecologicalprocesses 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 treecommunities during forest post-fire recovery in anthropogenic savannas. We used null models to infer the mainassembly processes driving forest succession along three 90-m transects running from an advancing savannaforestedge to forest interior in New Caledonia. We also evaluated if successional changes differed betweenlarge 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, involvingleaf, stem, and architectural traits along transects. Our results indicate stronger environmental filtering and fastertemporal changes in composition of young edge communities. In forest interior, our results suggest slowercompositional changes, with an important role of light limitation in community assembly. These non-randompatterns depended on both the decline of savanna trees and compositional changes among forest species. Wealso found contrasting community patterns depending on tree size, supporting a stronger influence of environmentalfiltering on small trees.Our work emphasized the dominance of deterministic assembly processes driving tropical forest post-firesuccession. Our study suggests that fire and drought drive environmental filtering during early succession atthe forest edge, entailing constraints on multiple functional dimensions. As succession progresses, lightlimitationbecomes a stronger driver of community assembly, and community composition becomes more stablein time. Our study provides insights for a better understanding of the processes guiding tropical forest successionin the particular context of post-fire forest recovery