Dimensions of Niche Differentiation Within the Barro Colorado Island Pioneer Tree Community

Pioneers are a guild of tree species dependent on recruitment in canopy gaps for their regeneration. They account for a significant fraction of Barro Colorado Island (BCI) tree species and exhibit wide variation in the traits influencing gap colonization, juvenile growth and survival, soil nutrient requirements, and adult longevity and size. Research on BCI has uncovered many trait relationships that either promote coexistence by equalizing recruitment success among species, or contribute to maintaining diversity through density-dependent seed mortality, or by partitioning habitats according to soil fertility, gap size, or adult persistence and timing of reproduction. Several features of pioneers, including high and predictable seed production, rapid growth, and manageable diversity, make them a good model system for understanding how biotic and abiotic interactions affect recruitment success and species coexistence. Furthermore, the future contribution of tropical forest to carbon storage will be strongly influenced by the relative contribution of pioneers to tropical tree communities.