Temporal variation in seed densities and their influence on seedling survival are evident in various forests. Southeast Asian forests, renowned for the phenomenon of general flowering (GF), exhibit great degrees of temporal variation in seed density due to the intermittent synchronized plant reproduction. High seed density may enhance seed survival via predator satiation yet creates great competition in early seedling stages. Seed additions during general flowering events therefore have dual impacts to forest diversity. To understand whether strength of density dependence differs between different early life stages and between various seed production magnitudes, we monitored seed rain and seedlings in the Pasoh forest for during and between GF events. Temporal variation of seed rain was examined with 336 passive seed traps. Additionally, this study monitored seedling dynamics in more than 1000 1x1 m plots near the seed traps. We used the data to evaluate density dependence on seed-to-seedling and seedling-to-yearling transitions for frequent and supra annual flowering species.
Results/Conclusions
We found negative density dependence in both transitions with a stronger effect for seed-to-seedling transition than for that of seedling survival. Strength of density dependence exhibited high within-group variation for frequent and supra annual flowering species. We found lower initial diversity of seedling from cohorts of non GF years than that from GF years. Quickest decrease of diversity was found in the cohort from the largest GF event, followed by two cohorts from non GF years and then cohorts from weaker GF events. However, longer-term diversity did not follow the same trend. We discussed elements for the decrease of diversity in the study.
