Divergence in a Neotropical forest during 33years of succession following clear-cutting

Questions: Are vegetation recovery trajectories converging or diverging during succession following clear-cutting? Are the trajectories approaching the species composition of surrounding old-growth forests? Location: Atlantic forest, Vale Natural Reserve, Linhares, southeast Brazil. Methods: A forest management experiment was established in an old-growth forest using 0.5-ha plots arranged in a randomized block design with five replicates. We analysed data collected from two treatments: plots that were clear-cut in 1980 without burning or tree stump removal, and control plots with old-growth forest that was left unmanaged. We analysed species abundance data (DBH10cm) recorded for both treatments between 6 and 33yr after clear-cutting. We computed mean multidimensional compositional distance of stands of the same successional age, and compared different ages to test whether trajectories during succession were divergent or convergent. Furthermore, we explored successional trajectories using ordination. Results: Regenerating stands were more similar to each other at 6yr than at 33yr after clear-cutting. Trajectories of the five recovering stands showed nearly monotonic divergence during succession and gradually approached the composition of surrounding old-growth stands. Furthermore, pioneer and non-pioneer species colonized the stands throughout the successional trajectory. Species recruitment occurred at different times and the species composition changed substantially during the 33yr after clear-cutting. As expected, species richness increased over time. Our findings suggest that successional trajectories have their own attractors: the surrounding old-growth stands towards which the composition of the regenerating community tends to return. Even so, 33yr after clear-cutting, regenerating stands had distinctly different communities from surrounding old-growth forest. Conclusions: Secondary succession in the Atlantic forest shows that multiple, divergent trajectories which started with more similar species composition were directly influenced by their surrounding vegetation and gradually increased their similarities to the surrounding old-growth forest.