Vegetation functional diversity along power line rights-of-way in eastern Canadian forests

In forested regions, rights-of-way for power lines modify local environmental conditions, creating three vegetation zones: the corridor, forest edge and adjacent forest. Because corridors undergo regular vegetation maintenance to prevent tree growth, their effects on vegetation functional diversity remain poorly understood. We surveyed the abundance and cover of forbs, shrubs and trees at 18 sites spanning a 750 km north–south climatic gradient in Québec, Canada. For each vegetation stratum and position relative to the right-of-way, we calculated functional diversity metrics (functional richness, divergence, evenness, and dispersion) and the Shannon Weaver index using plant functional traits reflecting ecological strategies, pollinator habitat suitability, and ecosystem functioning. Linear mixed-effects models assessed the effect of position relative to the right-of-way, corridor characteristics, edaphic variables, and climate on each diversity index.Position relative to the right-of-way was the principal driver of vegetation functional diversity, significantly influencing 8 of the 15 models; the strongest model explained 52 % of variation, and the median marginal R2 was 0.33. In contrast, corridor characteristics had fewer effects. Shrub functional diversity was consistently lower in corridors than at forest edges and adjacent forests, while forest edges were similar to adjacent forests. Responses of forb communities were mainly influenced by climatic conditions interacting with position, whereas tree functional diversity showed few responses. Overall, power line rights-of-way primarily altered the functional diversity of understory vegetation, whereas forest edges retained functionally diverse communities comparable to those in adjacent forests. These findings advance understanding of vegetation responses to right-of-way management across broad environmental gradients.