Edge effects of three anthropogenic disturbances on spider communities in Alberta’s boreal forest

Abstract

Increasing fragmentation of forests worldwide by timber and industrial development makes it important to understand the edge effects of common anthropogenic disturbances on forest fauna. We collected ground-active spiders along transects across the edge of logging clearcuts, gravel roads and gas pipelines in the boreal forest of Alberta, sampling on the disturbance (10 m from forest edge), and 10, 45, and 200 m into the forest. We asked whether the three disturbances were associated with edge effects on spider communities, and whether the extent of their associated edge effects were equivalent. The spider community at the edges of clearcuts was distinct from interior and on-disturbance communities 10 m into the forest from the clearcut edge, showing an edge effect of between 10 and 45 m from clearcut edges, while no edge effects were apparent at road and pipeline edges. Edge effects therefore differ at linear and non-linear openings in the boreal forest, which suggests that small linear openings may be associated with minimal edge effects compared to large polygonal forest openings. This result has important consequences for forest management, where clearcuts and other non-linear openings are likely to cause edge effects on spider communities that are between 10 and 45 m in their extent. The small size of clearcuts as practiced in the public forests of Canada, and their dense and broad application across the landscape, makes this edge effect of broad spatial significance in protecting biodiversity in managed landscapes.