JERALD J. DOSCH, CHRIS J. PETERSON, AND BRUCE L. HAINES. 2006. Seed rain during initial colonization of replicate abandoned pastures in the premontane wet forest zone of southern Costa Rica. Journal of Tropical Ecology, in press.

Abstract

Understanding tropical succession requires explaining not only similarities but differences in composition. Yet causes of compositional differences among postagricultural succession sites have seldom been examined. We monitored seed rain for 14 months in five abandoned pastures in southern Costa Rica, collecting seeds from 20 September 1996 to 17 November 1997. 1,140,688 seeds of 165 morphospecies were collected. The majority of seeds (80.1 %) arrived during the wet season and 96.9 % were Melastomataceae. Total seed rain density was greatest at the forest/pasture edge and decreased drastically just a few meters into pastures. Species richness was highest in the wet season and greater in forest than in pasture. Seed rain shifted from domination by the family Melastomataceae in forest and interface samples to Marcgraviaceae and Asteraceae in pasture samples and also varied greatly by site. The overall seed rain density varied by over 3-fold between sites and broadly mirrored among-site variation in early woody plant colonization density. However, seed rain and woody plant colonists were rather dissimilar in composition, suggesting that while propagule availability is necessary for early woody plant establishment, it is a poor predictor of successional trajectory.