The extent of edge effects increases during post-harvesting forest succession

As human activities increase landscape fragmentation, edge effects on ecosystem properties are growing at an unprecedented rate. The influence of logging-induced edges on biodiversity can ultimately jeopardize the long-term sustainability of forest management practices. These effects are difficult to quantify, however, because temporal changes in edge influence on residual forests remain poorly understood. We examined vegetation gradients along 17 transects crossing the boundary between stands harvested 5-66 years ago and old-growth boreal forests. We estimated the magnitude and distance of edge influence (MEI and DEI, respectively) in uncut old-growth forests, and investigated how these attributes of edge influence changed during the regeneration of adjacent logged stands. Analyses indicated that three types of vegetation gradients were necessary to describe the temporal changes of edge influence on vegetation in uncut forests. No temporal changes were detected for MEI during 66 years of forest succession. Conversely, DEI in uncut forests ranged from 0 to 70 m, and increased as the adjacent logged stands regenerated. This edge expansion through time, together with persistent differences in vegetation between logged and old-growth forests for at least 66 years, raise questions as to whether or not forest management involving fast rotations between logging events can maintain biodiversity. In forest ecosystems where edge habitat widens while vegetation has still not recovered to its typical characteristics, the planning of an adequate combination of rotation time, size and perimeter/area ratio of residual forests becomes critical to achieve the objectives of sustainable management, including regional biodiversity preservation.