Characterization of Plant Community Structure and Abiotic Conditions on Climbed and Unclimbed Cliff Faces in the Obed River Gorge

Walker, Gary; Parisher, Emily; Smith, Peter; Whitlock, David; Kramar, David; Matthes, Uta; Morefield, Leslie

Many rare or endemic species have been found on cliff faces around the world, but most of the world’s cliff ecosystems remain unexplored by biologists and little is known about ecosystem processes on cliffs. There is a growing concern however, that biodiversity on cliffs may be threatened by impacts from recreational rock climbing. Several recent studies have validated this concern. The Obed River Gorge in Tennessee boasts one of the richest floras in the southeastern United States and is also a popular rock climbing destination. Vascular plants, bryophytes, and lichens were sampled on cliff faces, cliff edges and on talus slopes along sixteen climbed and sixteen unclimbed transects in six different cliff areas of the Obed River Gorge and its tributary, Clear Creek. Cliff-face flora was sampled from pairs of 1m2 plots located at three-meter intervals along the transect. Unclimbed transects were paired with and adjacent to climbed transects. Abiotic factors including aspect, slope, surface heterogeneity, and light were measured for each pair of plots. Canonical Correspondence Analysis (CCA) was performed to determine the relative importance of each of these abiotic factors, as well as the impact of rock climbing, in shaping the cliff-face plant communities of the Obed River cliffs. Results indicate some impacts of foot traffic in the talus slopes of climbed areas on vascular and non-vascular species. Habitat and site were the most important variables accounting for variation in the vegetation. In addition, preliminary sectioning of a Juniperus virginiana snag in the talus slopes yielded eight-hundred annual rings.