Edge effects on plant communities along power line clearings

1. Power line clearings are edge-creating disturbances in landscapes world-wide, but there have been few studies on their bordering vegetation. Our aim was to quantify edge effects on plant communities along such clearings in Norway and to identify factors that influence these edge effects. 2. We surveyed understorey plant communities on either side of the power line clearing–forest edge at 51 sites, along four parallel transects at each site. Each transect had four plots located, respectively, in the clearing centre, clearing edge, forest edge and forest. We quantified the magnitude of edge effects (MEE) on either side by comparing edges with their corresponding ‘non-edge’ reference habitats. We also measured differences in species composition across the edge (clearing edge vs. forest edge). Habitat characteristics were sampled at plot and site level and from digital maps. 3. Differences in species composition were greater between clearing centres and clearing edges than between forest...