Seed rain variation across a tropical humid forest chronosequence

Chronosequences provide space-for-time substitutions to study ecological succession and guide restoration efforts. We evaluated seed rain dynamics across a tropical forest chronosequence in the lowland mountain landscape of Caquetá, Colombia, using monthly seed trap data collected from September 2017 to August 2018 in 18 plots (50 × 50 m) classified into early-secondary, intermediate-secondary, and old-growth forest. Seed morphospecies richness and mean seed mass increased with stand age, while total seed abundance declined, suggesting a transition from small-seeded pioneer species to larger-seeded, late-successional species. Despite differences in richness and abundance, species composition did not differ among stand age groups, likely due to the limitations of morphospecies identification. Seed rain positively correlated with precipitation with a lag time of 3 months, suggesting that heavy rainfall is a prerequisite for fruit production. Seed rain peaks were dominated by Eugenia sp. and Piptocoma discolor, the latter contributing most seeds in early- and intermediate-secondary forests. Correlations between morphospecies richness and seed abundance with basal area (m²/ha), species richness, and species diversity are likely explained by resources associated with structural variables (e.g., fruit abundance, canopy cover, and microhabitat diversity) that influence seed disperser behavior. Additionally, successional stage may play a role, as older or more structurally complex forests tend to support more plant species that may contribute to higher seed rain diversity and abundance. Early-secondary forests in this landscape are unlikely to be dispersal-limited, indicating potential for unassisted restoration, though isolated patches may require connectivity interventions such as plantings or living fences to overcome seed input constraints. Further studies are required to evaluate disperser movements across the fragmented landscape as well as plant recruitment, prior to making recommendations on ecological intervention strategies.