Limited influence from edges and topography on plant structural and taxonomic diversity in fragments of Atlantic Forest

Abstract

AbstractAlthough Atlantic Forest is very diverse and heavily fragmented, little is known about the impact of created edges on forest structure and plant diversity within its forest remnants. We aimed to determine the distance of edge influence on vegetation in forest fragments in the Atlantic Forest; to compare the effects of edge influence, topography and their interaction on vegetation structure; and to assess patterns of structural and taxonomic diversity. We collected data on forest structure, plant functional groups, plant families and vertical vegetation structure in 2 m x 2 m contiguous quadrats along 250 m transects across the edges of 24 fragments approx. 70 km west of São Paulo. We used randomization tests to estimate the magnitude and distance of edge influence, generalized linear mixed model to assess the effect of topography, and wavelet analysis to evaluate spatial patterns. We found evidence of edge degradation (lower diversity and cover of most plant groups compared to interior forest) and edge sealing (abrupt changes at the edge particularly for leafy vertical structural diversity), but edge influence did not extend very far into forest with a distance of edge influence or less than 20 m for most variables. Less extensive edge influence compared to other tropical forests was not explained by topography (slope) but could be due to more extensive fragmentation and land use history. The use of multiple approaches to studying forest edges provided complementary information to improve our understanding of the structure of anthropogenic edges in Atlantic Forest.