The magnitude and extent of edge effects on vascular epiphytes across the Brazilian Atlantic Forest

Edicson Parra-Sanchez,Cristina Banks-Leite

doi:10.1038/s41598-020-75970-1

Abstract

Edge effects are ubiquitous landscape processes influencing over 70% of forest cover worldwide. However, little is known about how edge effects influence the vertical stratification of communities in forest fragments. We combined a spatially implicit and a spatially explicit approach to quantify the magnitude and extent of edge effects on canopy and understorey epiphytic plants in the Brazilian Atlantic Forest. Within the human-modified landscape, species richness, species abundance and community composition remained practically unchanged along the interior-edge gradient, pointing to severe biotic homogenisation at all strata. This is because the extent of edge effects reached at least 500 m, potentially leaving just 0.24% of the studied landscape unaffected by edges. We extrapolated our findings to the entire Atlantic Forest and found that just 19.4% of the total existing area is likely unaffected by edge effects and provide suitable habitat conditions for forest-dependent epiphytes. Our results suggest that the resources provided by the current forest cover might be insufficient to support the future of epiphyte communities. Preserving large continuous ‘intact’ forests is probably the only effective conservation strategy for vascular epiphytes.

Highlights

Edge effects are ubiquitous landscape processes influencing over 70% of forest cover worldwide
Our results provide evidence that (i) canopy and understorey strata respond to edge effects, (ii) the magnitude of edge effects within fragments is low in both strata and (iii) edge effects extend far into forest interiors (> 500 m), leaving only 0.24% of the studied human-modified landscape ‘free of edge effects’
These results suggest that there is a high degree of biotic homogenisation across the human-modified landscape and that the majority of the Brazilian Atlantic Forest (BAF) is under this influence, as it has only 3.3 Mha (19.4% of the total BAF) of habitat further than 500 m from an edge

Summary

Introduction

Edge effects are ubiquitous landscape processes influencing over 70% of forest cover worldwide. Within the human-modified landscape, species richness, species abundance and community composition remained practically unchanged along the interior-edge gradient, pointing to severe biotic homogenisation at all strata. This is because the extent of edge effects reached at least 500 m, potentially leaving just 0.24% of the studied landscape unaffected by edges. Lefebvre et al.[24] developed a novel approach to quantify and map the magnitude and extent of edge effects on species abundances across landscapes This approach incorporates a spatially explicit model to integrate the potential spill-over effects from different habitats, distance from nearby edges, and how these effects are modulated by habitat quality.

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