Rock-climbing shifts cliff-face vegetation community composition based on site characteristics

Questions What are the effects of rock-climbing on diversity, abundance and composition of cliff-face vegetation along environmental gradients? Does site variability influence cliff vegetation more than the presence of climbing? Location Linville Gorge Wilderness Area, NC, USA. Methods We compared species richness, Shannon's diversity, abundance and species composition of lichens, bryophytes and vascular plants within 334 plots, each 1 m(2). We compared climbed plots with unclimbed plots using Non-metric Multidimensional (Distance) Scaling ordination, means comparison and regression analysis. Results Eighty-five species were observed within 334 m(2) of cliff-face plots, including one North Carolina state (Canoparmelia alabamensis) and 21 Burke County collection records. Climbing altered cliff plant communities: unclimbed cliffs supported more diverse and different species than did climbed cliffs. However, site was more important than was climbing in differentiating cliff community composition. Variation in species composition was driven mostly by variation in cliff aspect and surface heterogeneity. Cliffs with the highest surface heterogeneity had the highest species richness, diversity and abundance of all three vegetation types (lichens, bryophytes and vascular plants). Unclimbed areas had similar richness, diversity and abundance compared with easy climbing routes, whereas harder climbing routes supported lower species richness and abundance of all vegetation types. Conclusions Differences in cliff-face vegetation in Linville Gorge were due more to site variability than to climbing impact. Therefore, management of climbing areas and decisions for future route development should be site-specific and include a thorough biological survey.