Species enrichment in tropical dry forest recovery: Successional patterns of seed rain attributes

Propagule availability limits the successional recovery of tropical dry forest (TDF). Despite high resprouting potential in these regrowing forests, the floristic enrichment of communities with reduced seed banks largely depends on seeds of species absent from the site (i.e., allochthonous component). Successional development of vegetation structure and composition potentially shapes seed rain attributes by modifying attractiveness to dispersers or the dispersal of anemochorous seeds. We examined the successional and seasonal variation in seed rain richness and abundance across two contrasting components (autochthonous vs. allochthonous) and for subsets defined by dispersal mode, growth form, and successional guild. Monthly seed rain samples were collected over one year in a successional chronosequence (1–60 years). We used a Bayesian approach to model the responses of seed rain richness and abundance to age and season (wet vs. dry) by fitting generalized additive models, and a detrended correspondence analysis to assess the spatial autocorrelation of seed rain composition. Community-level seed rain abundance decreased as succession progressed, while community and autochthonous species richness increased. The allochthonous component of the seed rain responded to season, rather than age, with higher values in the dry season, as observed for most plant groups in the seed rain subsets. Dispersal modes shifted from anemochory to endozoochory, and from seeds of non-woody to seeds of woody species in later stages. The composition of seed rain exhibited strong spatial autocorrelation. The interplay of succession, seasonality, and landscape context shapes seed rain, thus confirming its important role in species enrichment during TDF regeneration.