Spatial and temporal variation in seedling recruitment of nine tree species in a subtropical rain forest
Transition of seed to seedling includes several stages: seed production, seed dispersal, seed emergence, and seedling survival. The perspective roles of these stages in determining the seedling abundance may reveal trade-offs between life-history traits, which have implications for forest dynamics and species coexistence. We monitored the seed rain and seedling dynamics in the Fushan subtropical rain forest, northern Taiwan (24°45’ N, 121°35’ E) for 12 years (2003–2014). In this study, we applied this dataset to investigate the relative importance of seed production, seed dispersal, and habitat conditions in structuring plant populations at seedling stage for nine tree species. For each species, we estimated the seed production and dispersal distance by using a hierarchical Bayesian model incorporating interannual variation in seed production. We also examined the relative importance of seed and of habitat condition in regulating the local seedling density, and quantified the effects of biotic and abiotic factors on seedling survival.
The estimated mean seed production was related to seed size, but the mean dispersal distance was unrelated to seed size or fecundity. Both the seed density and habitat conditions could explain the spatial-temporal variation in recruit abundance, while the habitat conditions exhibited stronger effects than the seed density. We detected the significant effects of biotic and abiotic factors on seedling survival. However, the factors that influenced seedling survival generally were unrelated to the factors that influenced recruit abundance. Though we did not found clear evidence for trade-offs between life-history traits, large temporal and individual variations in seedling recruitment observed may have great consequences for species coexistence in this subtropical rain forest.