Hiking trailheads, but not trailsides, associated with higher cover of non-native plants' trail impact on non-native plant cover

Question: Natural areas are commonly managed for multiple purposes, including both conservation and recreational use. Hiking trails are an extremely common feature in natural areas that enable recreational use, but trail construction and use can also facilitate the spread of non-native species by altering trailside conditions, creating disturbances, and acting as a conduit for non-native propagules to be carried into the backcountry.Location: Powdermill Nature Reserve, Southwestern Pennsylvania, USA.Methods: We tested how distance from trailhead and trailside affected the under story plant cover and abundance and light and soil environment by establishing study plots at varying distances from the trailhead along perpendicular transects from the trailside.Results: We found that non-native plant cover decreased with distance from the trail head, with the majority occurring within 1 km of the trailhead, while non-native cover increased by as much as 12% moving away from the trailside and toward the forest interior. Total species richness and diversity decreased with increasing distance from the trailhead and per-species mean cover increased. Total cover decreased in plots with higher light levels.Conclusions: Our results suggest that hiking trails could be acting as a conduit for the spread of non-native plants, with the greatest effect occurring near the trailhead where early detection and future management efforts could be concentrated. The measurable increase in non-native cover moving away from the trailside is potentially a result of trails being constructed in an already-invaded forest, with the effects of trail construction or active management reducing non-native cover at the immediate trailside.