Edge Effects on Vegetation in Rights-of-Way

Jacques Brisson, Alain Meilleur, Marie-Josée Fortin, and André Bouchard

As a result of an increasing use of ecological methods for the control of vegetation in rights-of-way, it has become necessary to understand the natural processes that are likely to facilitate or hinder management objectives. Several factors may influence species composition within corridors, but edge effects of the vegetation immediately adjacent to the right-of-way is one of the most important. To better measure and understand edge effects, we studied the spatial distribution of vegetation types on test right-of-way sites located in southern Quebec. Sampling was done along 133 transects located perpendicular to the right-of-way, with a distance of 50 m between transects. Each transect consisted of seven quadrats covering the vegetation within the corridor and two quadrats outside of the corridor. The results show that there is a strong edge effect on plant composition in the right-of-way corridor, especially when it is bordered by a forest. The edge effects result in a greater dominance of tree species and to a lesser extent a greater number of shrubs. Besides species richness, the species composition is also different at the edge of the right-of-way, with several species more likely to be found at the edge, while others occur more often in the central zone. There was little significant difference between north-facing and south-facing edges. Seed dispersal is assumed to be the main factor responsible for edge effects on plant composition. These results have implications on vegetation management in right-of-way corridors.

Keywords: Edge effects, corridor, right-of-way, spatial analysis, vegetation management