Effect of surrounding vegetation on edge-related tree mortality in Amazonian forest fragments

Little is known about factors that cause spatial variability in edge effect s, the diverse physical and biotic changes associated with the abrupt bound aries of fragmented forests. We examined the influence of three types of su rrounding vegetation (cattle pastures. Cecropia-dominated regrowth, and Vis mia-dominated regrowth). on edge-related tree mortality in Amazonian rainfo rest fragments. An ANCOVA revealed that the type of surrounding vegetation and distance to edge both had significant effects on tree mortality. Differ ences among vegetation types were greatest within 0-20 m of fragment edges; with edges bordered by cattle pastures having higher mortality than those bordered by Cecropia- and Vismia-dominated regrowth. Edge effects appeared to penetrate further into pasture-bordered edges (ca. 60-100 m) than those bordered by regrowth forest (ca. 40-60 m), but this difference was nonsigni ficant because of considerable patchiness in tree mortality. Overall, our r esults suggest that edge effects in forest fragments are significantly infl uenced by the structure of surrounding vegetation, and that the capacity of different regrowth forests to buffer edge effects can be predicted from th e growth form and stand features of the dominant tree species. Management o f surrounding vegetation can ameliorate the negative effects of edge creati on on small forest fragments. (C) 1999 Elsevier Science Ltd. All rights res erved.