The effects of forest type, harvesting and stand refinement on early seedling recruitment in a tropical rain forest

Maintenance of high plant diversity in tropical rain forests has been hypot hesized to be related to intense seed predation, and studies have shown tha t the impact of seed-eaters varies according to seed size, forest type and level of disturbance. The hypothesis that seed survival and seedling recrui tment depending on seed size, are related to forest type and the intensity of harvesting and stand refinement was therefore tested at Paracou, French Guiana, for three animal-dispersed tree species. Two forest areas, correspo nding to two forest types, were selected based on the occurrence of a domin ant species, Eperua falcata (Caesalpiniaceae). Two factors were tested: for est type (E. falcata-rich and E. falcata-poor) and level of harvesting (unl ogged, low intensity of logging, low intensity of logging and thinning libe ration by tree-poison girdling) within each forest type. Overall, there was no effect of species nor of logging treatment within forest type after 6 w k. There was only a significant effect of forest type on seed survival in t he large-seeded Carapa procera, a rodent-dispersed species in the Meliaccae . In the two medium-sized seed species, Pradosia cochlearia and Manilkara b identata, two frugivore-dispersed Sapotaceae, the effect of treatment was o verall significant but was also highly variable between plots within treatm ents. After 1 y, C. procera showed little seedling recruitment due to low s eed removal and dispersal, and high seed-seedling predation under all condi tions. Neither forest type,. nor treatment nested within forest type, affec ted seedling recruitment in P. cochlearia whereas M. bidentata seedlings we re favoured in unlogged conditions at the E. falcata-poor forest type. Thes e results suggest that species characteristics (such as seed size and palat ability), or local tree diversity and resources for granivores select for c ontrasting patterns in tree recruitment between forest type in the rodent-d ispersed tree species, and these interact vith level of tree harvesting and stand refinement in the other frugivore-dispersed tree species.