Vegetation recovery on abandoned road segments of Highway 16 in northwestern British Columbia

Vegetation recovery on abandoned road segments of Highway 16 in northwestern British Columbia were examined across a climate gradient. The time since road abandonment ranged from 16 to 57 years on sites sampled. Plant cover on asphalt roads was compared with that found on gravel road shoulders using paired t-tests. Plant cover by growth form was further evaluated in response to climate and other environmental predictor variables using multiple regression ‘best fit’ models. Plant community ordination analysis using nonmetric multidimensional scaling was conducted to describe patterns across study sites in species space along environmental gradients. Key drivers of current plant community composition include time since road abandonment, road substrate type, and several different annual climate variables. The best predictor of vascular plant cover and total plant cover was time since road abandonment, but plant community composition was strongly driven by the coastto-interior climate gradient. Non-vascular cover was more abundant on asphalt roads compared to gravel substrates. Woody plant cover was greatest on gravel shoulders compared to gravel or asphalt road centers. Exotic plant cover was negatively correlated with mean annual relative humidity. Plant diversity and species richness were not driven by the climate gradient but instead reflected more site-specific environmental variables. Primary succession on abandoned roads in this study area may be constrained by continued anthropogenic disturbance post-abandonment.