Recruitment Limitation, Resource-Based Niches, and the Maintenance of Tropical Tree Diversity

Michigan State University, East Lansing MI

Investigators

Abstract

0075472 Kobe This proposal presents an integrated set of field experiments and model analyses to evaluate the relative influences of recruitment limitation and resource-based niches on the maintenance of tree species diversity in wet tropical forests. A particular focus of this proposal is soil resources (water and mineral nutrients), because strong indirect evidence warrants an examination of their role in the dynamics of tropical forest communities. The proposed addresses two sets of mechanisms that could enable the maintenance of high species diversity. First, to what extent are tropical tree species recruitment limited? Do species differ in recruitment limitation? Second, do tropical tree species partition gradients of resource availability? Specifically, what is the influence of soil resource and light availability on species-specific seedling survivorship and growth? Is there a trade-off among species in the ability to survive under low soil resources versus rapid growth under high soil resources. Is there a trade-off among species in colonization potential (fecundity and dispersal) versus competitive ability (resource based growth and survivorship), which underlies the maintenance of diversity? To address these questions, species-specific sub-models of seedling production and dispersal, and seedling growth and survival will be developed from field and experimental studies at La Selva Biological Station in Costa Rica. This study will contribute to understanding the mechanisms that lead to high tree species diversity in tropical forests. It will characterize offspring recruitment in terms of seedling production and dispersion, which in comparison to seed trap studies, is less biased against animal dispersed species and provides more robust sample sizes to rigorously test recruitment potential. The study also tests the influence of soil resources and light availability on species-specific seedling survivorship and growth. Finally, the research will integrate empirical results to assess the relative importance of recruitment limitation versus resource-based niches to the maintenance of tropical tree diversity.