Cumberland Plateau Escarpment Sandstone Outcrop
Southern Appalachian Rocky Summit (NatureServe 2015)
These outcrops are found in East Tennessee along the eastern escarpment of the Cumberland Plateau in the Plateau Escarpment Ecoregion, where they occur mostly on south and southwest facing slopes of Walden Ridge in Anderson and Roane Counties, and Whetstone Mountain in Morgan County. A few occur on the summit, but most are found on the south facing upper side slopes of these low-elevation ridges.
Cumberland Plateau escarpment sandstone outcrops are small patch communities that are surrounded by oak/pine dominated forests. The outcrops themselves are dominated by grasses and small herbs which are only 0.1-1 m (3 feet or less) in height. The vegetation is restricted to the outer edges of the rock outcrops, cracks in the rock, and shallow pockets of soil that develop on the rock surface. The exposed rock of the outcrops are dominated by mosses and lichens, lacking vascular plants.
These outcrops lie within the Level IV Ecoregion known as the Plateau Escarpment. The majority occur on the upper side slopes of Walden Ridge and Whetstone Mountain. With the exception of a couple that occur on the summit of Walden Ridge, they are restricted to rather steep (25-80 % sloping) south and south-west facing hills. The elevation of the outcrops range from approximately 305 – 488 meters (1000-1600 feet). The size and shape vary widely, with the average roughly 16 x 7 meters (52 x 26 feet). The bedrock is Pennsylvanian aged sandstone and sandstone conglomerate. The soil is comprised of both Ramsey-Rock outcrop complex (Anderson County) and Gilpin-Bouldin-Petros complex (Morgan and Roane Counties). It is quite stony, moderately acidic, and well drained.
Developed from erosional processes, these outcrops are weathered by south-winds and rain, which keep the rock surfaces exposed. This limits the amount of soil deposition, keeping it restricted to shallow pockets, edges, and cracks within the rock surface. The exposed rock receives high amounts of solar insolation. All of these factors play a part in maintaining the openness of the outcrops and place restrictions on vascular plant growth.
Due to the lack of floristic survey a dominant plant list is not available.
Amelanchier sanguinea (roundleaf shadbush), Diervilla rivularis (mountain bush-honeysuckle), Fothergilla major (mountain witch-alder), Phemeranthus mengesii (Menge’s fame-flower), Pseudognaphalium helleri (Heller’s catfoot),
At this time, the invasive species present on the outcrops is unknown.
Community Variation and Subtypes
The first subtype of this community is the characteristic exposed rock that is dominated by non-vascular plants like mosses and lichens. A second subtype is the shallow pockets of soil and cracks along the rock surfaces that support small forbs and herbaceous plants. Lastly, the edges of the outcrops, where deeper soil is present, is dominated by larger vascular plants such as shrubs and small trees.
Associated Natural Communities
Cumberland Plateau Dry Sandstone Woodland
Cumberland Thrust Block Sandstone Outcrop
Presettlement Distribution and Size
Cumberland Plateau escarpment sandstone outcrops are likely the same as they were pre-settlement, but may have been more widespread at one time.
These small communities are rare and have a very limited range, occurring only on Walden Ridge and Whetstone Mountain.
Anderson Co., Walden Ridge: (36.047179, -84.318144)
Morgan Co., Whetstone Mountain: (36.005524, -84.485422)
Roane Co., Walden Ridge: (36.908184, -84.628800)
Development of the ridges where they occur is the only known threat to these outcrops.
Outcrops are self-maintained when left undisturbed.
Future Research Needs
Floristic surveys and plot work are needed to determine which species are characteristic, dominant, and invasive to these outcrops. Such work would likely be beneficial to the conservation of this rare community type.
Hardeman, W.D., and others, 1966, Geologic map of Tennessee: Division of Geology, Tennessee Department of Environment and Conservation, scale 1:250,000
NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1 NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org
Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed February/2/2015
Checklist of Plant Species known from this community