Date of Award

Summer 2021


Access is available to all users

Document Type


Degree Name

Master of Science (MS) in Biology




Saxicolous lichens and bryophytes dominate cliff communities of Eastern Washington State. A recent rise in the outdoor recreation of rock climbing has caused major concerns over its potential negative impacts on cliff-dwelling biodiversity. To better understand how rock climbing is impacting lichen, bryophyte and vascular plant communities in Spokane, WA, I surveyed two sites: McLellan Rocks and Rocks of Sharon, for the abundance, richness and diversity of lichens, bryophytes and vascular plants. Sixteen paired transects consisting of a climbed route and the unclimbed adjacent cliff face, with eight plots per transect for a total of 256, 0.5m2 plots were surveyed for this study. Climbed and unclimbed communities overlapped, but were significantly different from one another. Overall, cover was significantly lower in climbed transects compared to unclimbed transects. Rock climbing routes at McLellan Rocks had reduced plant cover, richness and diversity. Climbing also decreased lichen cover, richness, and diversity, however, it was site specific: lichen cover and diversity decreasing at Rocks of Sharon, while lichen richness decreased at McLellan Rocks. Lichen morphogroups were differentially impacted. Crustose and endolithic lichen cover and richness exhibited a positive response to climbing pressure at McLellan Rocks, and crustose lichen richness was also higher in climbed vs. unclimbed areas at Rocks of Sharon. The remaining morphogroups decreased in cover, richness, and diversity in response to rock climbing. Specifically, foliose cover, fruticose cover, umbilicate cover, richness, and diversity, and leprose cover at Rocks of Sharon were lower on climbed routes, as was fruticose lichen cover at McLellan Rocks. In addition to climbed status, route age, route popularity, approach distance, slope, rock heterogeneity, plot height, and canopy cover significantly influenced community composition. I found 118 lichen, 29 bryophyte and two vascular plant species. The most common species were crustose lichens within the genus Rhizocarpon, and the most diverse lichen groups were the foliose genus Xanthoparmelia and the umbilicate lichen genus Umbilicaria. At the McLellan Rocks site, bryophytes were extremely diverse and abundant, species included the mosses Grimmia trichophylla, Antitrichia californica, and Syntrichia ruralis as well as the liverwort Porella cordaeana. Based on my results, I conclude that rock climbing mainly impacts cliff-dwelling lichen, bryophyte and vascular plant communities at my studies sites in decreasing cover, richness, and diversity. However, different patterns of impacts were observed at the two sites surveyed here, suggesting that unique management plans must be developed for each climbing area.