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Blue Ridge High Elevation Gabbro Outcrop

Synonyms

Southern Appalachian Rocky Summit Ecological System (NatureServe 2015)

High Elevation Rocky Summit (typic, high peak, little bluestem basic, ninebark basic and high peak lichen subtypes) (Schafale 2012)

Distribution

Northeastern Tennessee (Unicoi and Carter Counties), where restricted to gabbro exposures above 5000 ft. in the Southern Igneous Ridges and Mountains level IV ecoregion (Comer et al. 2003).

Vegetation Description

This small patch community is an herbaceous-dominated outcrop of short herbs, mosses, lichens, and the occasional shrub ranging from 0.1-1.0 m in height.

Physical Characterization

This community occurs in the Southern Igneous Ridges and Mountains level IV ecoregion on a variety of aspects due to their situations on mountaintops and mountainflanks of mountain slopes and ranges in elevation from 1550-1760 m (5100-5800 ft). This community occurs as discrete patches of flat, gently sloping, steeply sloping (8 to 30 percent slopes), and vertical outcropping bedrock in open grass and shrub balds. Most outcrops are small and range from 0.0001-0.04 ha. Bedrock and boulders that comprise the substrate of this community are Precambrian-aged gabbro that are dark and porophytic (TN geology layer). Soils, usually windswept and poorly-developed are haplumbrepts of the Wayah-Burton and Burton-Craggey complexes. These soils are well- to somewhat excessively-drained, stony to bouldery loams and gravelly loams derived from loamy residuum and/or creep deposits weathered from igneous and metamorphic rock with a relative pH of 4.8.

Natural Processes

This community is maintained by edaphic factors, such as shallow soils and exposed bedrock, and the harsh climate of high-elevations, such as cooler average temperatures, high moisture, high winds, and a short growing-season.

Dominant Plants

Wiser et al. (1996) studied rock outcrops in the Roan Mountain Massif and the North Carolina Heritage Program (Schafale 2011) has studied many of the high-elevation outcrops in adjacent North Carolina. Shrubs: Sorbus americana (mountain ash), Vaccinium corymbosum (highbush blueberry); Herbs: Carex misera (wretched sedge), Micranthes petiolaris (Michaux’s saxifrage).

Characteristic Plants

Houstonia montana (Roan Mountain bluet), Minuartia groenlandica (mountain sandwort), Paronychia argyrocoma (silvery nailwort), Potentilla tridentata (three-toothed cinquefoil), Solidago spithamea (Blue Ridge goldenrod), Trichophorum caespitosum (tufted club rush) (Schafale 2012; Wiser et al. 1996).

Restricted Plants

Carex misera (wretched sedge), Geum radiatum (spreading avens), Houstonia montana (Roan Mountain bluet), Minuartia groenlandica (mountain sandwort), Paronychia argyrocoma (silvery nailwort), Potentilla tridentata (three-toothed cinquefoil) Solidago spithamea (Blue Ridge goldenrod), Trichophorum caespitosum (tufted club rush).

Invasive Species

There are no known invasive species in this community.

Community Variation and Subtypes

Saxifraga michauxii - Carex misera - Oclemena acuminata - Solidago glomerata Herbaceous Vegetation (CEGL004277)

Associated Natural Communities

Blue Ridge Grass Bald (northern type), Blue Ridge Heath Bald, Blue Ridge Northern Hardwood Forest, Blue Ridge Spruce-Fir Forest

Similar Communities

Blue Ridge Low Elevation Granite Outcrop, Blue Ridge Granite Cliff

Presettlement Distribution and Size

Current distribution and size is estimated to be the same as that during presettlement.

Present Status

The extent to which fire may have maintained rock outcrops, and fire suppression may have diminished present status of the community is unknown. Otherwise, the present status is intact and secure.

Representative Sites

Carter Co.: Round Bald and gap leading to Jane Bald, on the TN and NC sides of the border (34.673452°, -86.938771°)”

Threats

Some examples are threatened by trampling from hikers at scenic vistas.

Management Considerations

Protection from trampling is recommended.

Future Research Needs

There is a need for mapping and baseline data collection of examples in Tennessee, as well as what maintains the open nature of these communities.

Previous Studies

Wiser et al. (1996) conducted a community ecology study of high-elevation rock outcrops in the Southern Appalachians, of which only several sites concern this community. Schafale (2012) gives community descriptions for this community and similar rock outcrops from adjacent North Carolina.

References

Comer, P., D. Faber-Langendoen, R. Evans, S. Gawler, C. Josse, G. Kittel, S. Menard, M. Pyne, M. Reid, K. Schulz, K. Snow, and J. Teague. 2003. Ecological Systems of the United States: A Working Classification of U.S. Terrestrial Systems. NatureServe, Arlington, Virginia.

Geology available at Tennesse Spatial Data Server which can be found at http://www.tngis.org/geology.html which links to a USGS Water Resources Division site: http://water.usgs.gov/lookup/getspatial?geo250k Tennessee Spatial Data Server site notes: Thanks goes to Jim Julian for researching this improved geology layer from the Tennessee Division of Geology. **Note** - The Tennessee Division of Geology does not endorse this coverage, stating this version is still incomplete and not fit for distribution.

NatureServe. 2014. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed: March 26, 2015).

Schafale, M. P. 2012. Classification of the natural communities of North Carolina, 4th Approximation. North Carolina Department of Environment, Health, and Natural Resources, Division of Parks and Recreation, Natural Heritage Program, Raleigh.

Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed [03/26/2015].

Wiser, S. K., R. K. Peet, and P. S. White. 1996. High-elevation rock outcrop vegetation of the Southern Appalachian Mountains. Journal of Vegetation Science 7: 703-722.

Page created by Devin Rodgers and Dwayne Estes on 29 April 2015.

Suggested citation:

Rodgers, D. M. and D. Estes. 2015. Blue Ridge High Elevation Gabbro Outcrop. Tennessee Plant Communities Database, Austin Peay State University, Tennessee.