Ridge and Valley Sandstone Blockfield
Blue Ridge Low-elevation Boulderfield (NatureServe 2014)
Eastern Tennessee in Hawkins County, on the mid-slope of Devil's Nose Mountain.
Due to the complete lack of soil, vascular plants are mostly unable to colonize. Vining plants and small shrubs may be able to colonize the outer borders, but only lichens are able to inhabit the open areas.
Blockfield communities are primarily composed of large unassociated rocks, preventing any real soil deposition and plant growth. They occur on Clinch sandstone, in the Southern Sandstone Ridges Level 4 ecoregion, on south-facing slopes. The soil composition of the area is described as Wallen-Rock outcrop complex, with 25 to 60 percent slopes, is somewhat excessively drained, and has a pH of 5.3. The one known example occurs at 634m (2080 ft) elevation and is 0.1 hectares in size.
Historically, blockfield communities are thought to have been formed by periglacial activity during the last ice age. Due to the lack of vascular plant growth, soil deposition is minimal except on the borders with the surrounding forests.
Community Variation Subtypes
The communities consists of main block field body, which is unvegetated and primarily colonized by lichens on the rocks, and the borders which consist of vining plants and small shrubs which are able to take root in the shallow soils there.
Associated Natural Communities
Southern Ridge and Valley Dry Calcareous Forest (Natureserve 2015)
Blue Ridge Quartzite Blockfield
Low-Elevation Boulderfield Forests and Woodlands
Blue Ridge Granite Blockfield
Presettlement Distribution and Size
The community is very rare, only being represented by a single site in Hawkins county.
Hawkins County: Devil's Nose Mountain (34.541653°, -83.011808°)
Due to the location of the community, no major threats are present.
Protection from development and recreational human destruction is the priority for management.
Future Research Needs
NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web
application]. Version 7.1. NatureServe, Arlington, Virginia. Available
http://explorer.natureserve.org. (Accessed: May 29, 2015).
Soil Survey Staff, Natural Resources Conservation Service, United States Department
of Agriculture. Web Soil Survey. Available online at
http://websoilsurvey.nrcs.usda.gov/. Accessed [04/29/2015].