Does neutral theory explain community composition in the Guiana Shield forests?

Download or read book Does neutral theory explain community composition in the Guiana Shield forests? written by Olaf Bánki Sicco and published by . This book was released on 2010 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent years have seen a fierce debate about the causes of beta-diversity, the change in species composition over landscapes, in tropical rainforests. The introduction of neutral models has spurred this debate, by assuming that species composition changes randomly over landscapes with dispersal limitation as the driving ecological process. In this study the interaction between local and regional diversity of trees is investigated. We inventoried 61 1-ha plots in forests on brown and white sands, and on bauxite mountains in Guyana and Suriname. These data combined with earlier data led to the first biogeographical study on a species level involving 156 forest plots ranging from Venezuela to French Guiana. Forest composition changed dramatically between forest types, and at geographical distances. In general, forest composition followed geological patterns in the Guianas. Differences in plant attributes between the forest groups revealed a spectrum in covariation. On the one end of this spectrum a high dominance of trees with large seeds in dry fruits was combined with high wood densities in several forest types. On the other end a high dominance of trees and species with smaller seeds in fleshy fruits was combined with relatively low community averaged wood density. This spectrum could reflect different colonizing strategies of trees in the forest types, and could have an effect on potential dispersers. With neutral-like dynamical community models, different hypotheses on the low diversity of the white sand forest were evaluated. Forests on white and brown sands draw their species from different regional species pools. We provide strong evidence that asymmetric environmental filtering and a lower regional diversity (possibly due to the smaller size of the white sand area) could influence the lower diversity found in white sand forests compared with neighboring brown sand.