Eva Tamargo López, Elis Martinelli, Tobias Müller, David A. Donoso, María-José Endara, Nico Blüthgen, Sybille B. Unsicker, Katrin Heer, Nina Farwig

Tropical rainforests are highly threatened by deforestation, yet they have the potential to regrow naturally when left abandoned. To understand natural recruitment, it is essential to explore the recovery of tree-seedlings and their traits within the community assembly of secondary forests. Here, we studied the taxonomic and functional diversity as well as the composition of tree seedling communities in 39 plots along a chronosequence of forest recovery, ranging from 0 - 38 years after cacao production or pasture abandonment. We measured leaf traits related to the life strategy (acquisitive or conservative) of all tree-seedling species and determined the surrounding forest cover within a 500 m radius around each plot. Our results showed that the abundance, species diversity, and functional diversity of tree seedlings were increasing, and that the seedling composition was becoming more similar to old-growth forests with increasing time since the onset of recovery, even if it was nowhere near the composition of primary rainforests. The abundance of tree seedlings and their species diversity increased with increasing forest cover. Remarkably, the functional composition of the communities on plots formerly used for pasture was characterized by acquisitive traits, while former cacao plots and old-growth plots were associated with conservative traits, highlighting the role of prior land use in seedling recruitment.
Synthesis: Our study showed that forest recovery is a complex and multifactorial process. Forest cover is a key factor accelerating natural forest recovery, while prior land use may limit functional recovery, potentially affecting ecosystem functioning.