Floristic Composition and Edge-Induced Homogenization in Tree Communities in the Fragmented Atlantic Rainforest of Rio De Janeiro, Brazil

Abstract

This study investigates the changes of tree species composition and diversity along the gradient from fragment edge to interior, and between edge and interior habitats, on a regional scale, in nine Atlantic forest fragments (6–120 ha), in southeastern Brazil. A total of 1980 trees (dbh ≥ 5 cm) comprising 252 species, 156 genera and 57 families were surveyed using the point-centered quarter method. From the fragment edge towards the interior the proportion of shade-tolerant trees increased continuously. The majority of all trees within the first 100 m from the edge belonged to the pioneer-guild. Floristic dissimilarity was found to be higher among interior habitats of different fragments than among the corresponding edge areas or among different small fragments. Species diversity increased along the edge-interior gradient 1.5 times within the first 250 m. Our results support previous findings that the establishment of edge-affected habitats leads to tree species impoverishment and homogenization via the dominance and proliferation of pioneer species in the forest edges of severely fragmented tropical landscapes. We argue that conservation strategies which include the creation of buffer zones between forest edges and the matrix will be more efficient than the establishment of narrow corridors to connect fragments and protected areas.