Natural Communities of Virginia - Terrestrial System - High Elevation Mountain Communities: Southern Appalachian Shrub and Grass Balds

The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)

Southern Appalachian Shrub and Grass Balds
Balds constitute a group of globally rare communities restricted to high-elevation (> 1,500 m [5,000 ft]) summits and upper slopes in the southern Blue Ridge, from Virginia south to northern Georgia. Dense, shrub-dominated balds are confined in Virginia to high rocky summits in the Mount Rogers – Whitetop Mountain area of Grayson, Smyth, and Washington Counties. At least three vegetation types are present: an evergreen shrubland dominated by Catawba rhododendron (Rhododendron catawbiense); a deciduous shrubland dominated by American mountain-ash (Sorbus americana), minniebush (Menziesia pilosa), and southern mountain-cranberry (Vaccinium erythrocarpum); and a deciduous shrubland dominated by Smooth Blackberry (Rubus canadensis). Very rocky, cold, windswept habitats probably contribute heavily to the creation and maintenance of shrub balds. At least some may have originated after catastrophic logging and fire disturbances almost a century ago, but even in these there is little or no evidence of tree reproduction.

In Virginia, Southern Appalachian Grassy Balds are represented by a single occurrence covering approximately 80 ha (200 ac) near the summit of Whitetop Mountain at the convergence of Grayson, Smyth, and Washington Counties. Vegetation of this site is dominated by mountain oat-grass (Danthonia compressa), sedges (Carex brunnescens ssp. sphaerostachya , Carex debilis var. rudgei , Carex pensylvanica), and forbs such as three-toothed cinquefoil (Sibbaldiopsis tridentata) and Blue Ridge St. Johns-wort (Hypericum mitchellianum); several state-rare and globally rare species are present. The ecological dynamics that created and maintain this habitat are debatable, but probably include shallow rocky soils, fires, grazing, and microclimatic impacts such as frequent high-velocity winds and ice storms. Moreover, it is possible that the Whitetop bald represents a relict of true alpine vegetation that was more widely distributed at high elevations in the southern Appalachians during the Pleistocene.

Reference: Fleming and Coulling (2001), Weigl and Knowles (1999).

Click on the images below to open a larger image in a separate window.

	Southern Appalachian Grassy Bald on the upper south slope of Whitetop (George Washington and Jefferson National Forests). Photo: Gary P. Fleming.
	Trees encroaching on grassy bald around Buzzard Rock, on a southwest-facing spur of Whitetop, Smyth and Washington Counties (George Washington and Jefferson National Forests). Photo Gary P. Fleming.
	Shrub bald dominated by Catawba rhododendron (Rhododendron catawbiense) on Wilburn Ridge, Grayson Highlands State Park. Photo: Gary P. Fleming.

REPRESENTATIVE COMMUNITY TYPES:
The few examples of this group in Virginia have been well-sampled and their classification is relatively robust. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.

Danthonia compressa – Carex brunnescens

sphaerostachya – Sibbaldiopsis tridentata

CEGL004242

Rhododendron catawbiense – Menziesia pilosa Shrubland
Southern Appalachian Catawba Rhododendron Heath Bald
USNVC: = CEGL003818, in part
Global/State Ranks: G2/S1
Rubus canadensis Shrubland (PROVISIONAL)
Southern Appalachian Blackberry Bald
USNVC: ~CEGL003892
State/Global Ranks: GNA/SNA
Sorbus americana / Menziesia pilosa – Vaccinium erythrocarpum – Rubus canadensis Shrubland
Southern Appalachian Deciduous Heath Bald
USNVC: = CEGL003818, in part
Global/State Ranks: G2/S1

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The Natural Communities of Virginia Classification of Ecological Community Groups SECOND APPROXIMATION (Version 2.2)

The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)