Spatial and Temporal Variation of Seed Rain in a Tropical Lowland Wet Forest

Abstract

Patterns of seed rain were observed at five forest locations in recent treefall gaps and paired understory sites in a tropical wet forest in northeast Costa Rica. Seed rain was dominated by animal-dispersed species. Overall, significantly more wind-dispersed seeds arrived into treefall gaps than into forest understory. Contrary to expectations, understory sites received a greater seed rain than did gap sites during three of four sample periods over the course of one year. Considerable spatial heterogeneity, however, existed among forest locations, with some forest sites receiving up to three times more seed rain input than others. Results from this seed rain study generally matched those from an earlier study at this site in terms of seed rain volume and dominant plant families. Composition of seed rain was more similar among habitat types (i.e., gap, understory) than among forest locations (i.e., paired sites) suggesting that spatial foraging activity and habitat preference of seed dispersers result in non-random patterns of seed rain. If true, then such patterns have implications for evolution of fruit and seed characters that promote survival and establishment of seeds under certain environmental conditions.