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Synonyms

Southern Appalachian Montane Cliff and Talus (NatureServe 2015)

 

Distribution

Southeastern Tennessee (Polk County) in the Ocoee River Gorge (ORG), the Hiwassee River Gorge and the Tallassee River Gorge

Vegetation Description

This is a small patch community dominated by lichens and mosses and vegetation reaches a maximum height at well under a meter in most cases.  Occurring within forests or woodlands, the outcrops themselves are sparsely vegetated.  In crevices where soil development occurs there may be a number of herbaceous species, ferns, and stunted shrubs.  Trees, primarily Virginia pine ( Pinus virginiana ), are not prevalent on the outcrops themselves but are mostly limited to adjacent deeper-soiled areas.  

 

Physical Characterization

Blue Ridge xeric acidic phyllite outcrops are restricted to the Southern Metasedimentary Mountains EPA level IV ecoregion (Griffith et. al 1998). This system includes those dry-acid outcrops which tend to occur on mid to high slopes at an elevation of 400-450 meters on steep, exposed south-facing slopes that receive direct sun most of the day.  Those lower on the slope tend to support calciphiles and are presumably associated with base-rich geologic veins.  Phyllite outcrops occur within the Walden formation, which is bordered on the west by the Alaculsey Valley Fault and on the east by the Greenbrier Fault.  The rocks are progressively more metamorphosed from west to east.  Within this zone they are strongly angled and consist of large projections, promontories, and ledges of acidic phyllite bedrock.  Soil is absent or restricted to small cracks in the rock surface.


Natural Processes

This community is edaphically maintained.  Fire occurs and is thought to play a part in the ecology, especially of the surrounding woodlands.  Because of the instability of the phyllite bedrock, landslides are also probably important in modifying the quality and extent of outcrop habitat.

 

Dominant Plants  

Herbs

Eupatorium aff. semiserratum (thoroughwort sp.), Hypericum gentianoides (orangegrass), Packera anonyma (Small’s ragwort)

Graminoids

Bulbostylis capillaris   (densetuft hairsedge)


Characteristic Plants

NA

 

Restricted Plants

NA

 

Invasive Species  

NA

 

Community Variation and Subtypes

1)     Barren-outcrop edge: dominated by graminoids w/ a community of spring ephemerals 2) deep-soil fissures: may be occupied by woodland species, including tree species like Pinus virginiana 3) pavement outcrop: dominated by foliose lichens, mosses and a few small xerophytic herbs

 

Associated Natural Communities

Southern Appalachian Oak Forest, Southern Appalachian Low-Elevation Pine Forest

 

Similar Communities

NA

Presettlement Distribution and Size  

Habitat distribution and total size for this system has likely remained fairly stable hisorically

 

Present Status

Plans by the Tennesse Department of Transportation to construct a highway corridor through the ORG could potentially impact this system.  These xeric acidic phyllite outcrops are very limited in their range and occur on only a few ridges in southeastern Tennessee.

 

Representative Sites

Polk Co.: Ocoee River Gorge ( 35° 4'53.03"N,   84°30'20.40"W), Hiwassee River, Big Island ( 35°11'6.61"N,  84°28'56.44"W)

 

Threats

Xeric outcrops are probably not threatened by disturbance to surrounding woodlands.  However, plans by the Tennessee Department of Transportation to construct a highway corridor through the ORG have proposed alternative routes that would possibly result in the degredation of phyllite outcrops by removal and grading of promontories. 

 

Management Considerations

Outcrops are likely fairly protected from problems of succession and disturbance of matrix habitat.  The first priority of management should be the prevention of development directly on outcrop sites.  Prescribed burning of the surrounding woodlands should improve habitat for open communities.

 

Future Research Needs

Plot work needs to be done on this community.  Areas outside of the Ocoee River Gorge on the Hiwassee need to be investigated for harboring equivalent habitat.

 

Previous Studies

Shaw and Estes (2012) have been the only botanists to characterize this system.

 

References

Griffith G, Omernik J, Azevedo S.  1998. Ecoregions of Tennessee (color poster with map, descriptive text, summary tables, and photographs): Reston, VA., U.S. Geological Survey (map scale 1:1,000,000).

Hardeman, W.D., and others, 1966, Geologic map of Tennessee: Division of Geology, Tennessee Department of Environment and Conservation, scale 1:250,000

NatureServe. 2015. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed:  March 27, 2015 ).

Shaw, J. and D. Estes. 2012. Botanical Survey and Ecological Systems Mapping of the Ocoee River Gorge, Polk County, Tennessee.  Report submitted for the Tennessee Department of Transportation for the Corridor K Environmental Impact Assessment.

 

Checklist of Plant Species known from this community 

NA