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, and on a few caprock promontories of the Iron Mountains and Clinch Mountain. Four vegetation types are present: an evergreen shrubland dominated by Catawba rhododendron (Rhododendron catawbiense); a mixed shrubland of Catawba rhododendron, mountain laurel (Kalmia latifolia), black huckleberry (Gaylussacia baccata), and other species; 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 oatgrass (Danthonia compressa), sedges (Carex brunnescens, Carex flexuosa, Carex pensylvanica), and forbs such as three-toothed cinquefoil (Sibbaldia 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). Gary P. Fleming / © DCR Natural Heritage.||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. Gary P. Fleming / © DCR Natural Heritage.|
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