Effects of fragmentation on tree species diversity in a lowland tropical forest area of the andean foothills of Colombia.

Objective: To evaluate the effects of fragmentation on tree species diversity at a regional scale. Scope: A procedure based on floristic similarity was developed to evaluate the effects of deforestation, and its resultant forest fragmentation, on tree species diversity at a regional scale. Methodology: Floristic similarity among twelve forest patches of different areal extents, assessed using rarefaction curves and distance decay, was utilized to evaluate the effects of forest fragmentation on tree species diversity in a lowland tropical moist forest region located in the Andean foothills, Department of Casanare, Colombia. Main results: As fragmentation may reduce biodiversity at local scales while homogenize it at regional scales, a regional homogenization of tree species composition of the study area was expected. In contrast, inter-patch floristic similarity was low suggesting that pre-fragmentation tree species composition may still be maintained. Nevertheless, several of the tree species sampled could be prone to regional extinction, particularly if fragmentation is maintained or increased. Our results suggest that the analysis of inter-patch floristic similarity constitutes a practical way to evaluate the effects of fragmentation on regional tree species composition and distribution. This constitutes an analytical tool useful for the design of programs to conserve biodiversity at regional scales.