The Natural Communities of Virginia
Classification of Ecological Community Groups
SECOND APPROXIMATION (Version 2.2)
Low-Elevation Acidic Outcrop Barrens
The scrub and herbaceous vegetation of this group is characteristic of exposed sandstone, quartzite, and granitic outcrops up to about 975 m (3200 ft) elevation. These communities are scattered over the western Piedmont, Blue Ridge, Cumberland Mountains, and Ridge and Valley strike ridges. Habitats typically have very high cover of exposed bedrock, with vascular plants occupying crevices and locally developed organic mats. Soil environments are minimal and highly oligotrophic. Vegetation is usually a mosaic of shrub thickets, herbaceous patches, and lithophytic lichens. Composition varies to some extent with aspect and elevation. Woody scrub usually consists of scattered, highly stunted trees, bear oak (Quercus ilicifolia), and ericaceous shrub thickets. Herbaceous species, which are characteristically sparse or concentrated in discrete mats, include
silverling (Paronychia argyrocoma), little bluestem (Schizachyrium scoparium), broomsedge
(Andropogon virginicus var. virginicus), Pennsylvania sedge (Carex pensylvanica), poverty oat-grass (Danthonia spicata), and silky oat-grass (Danthonia sericea). A few sites support relatively dense cover of graminoids. Community types in this group are uncommon to rare and poorly inventoried in Virginia. Although many occurrences are in remote locations, degradation from trampling and invasive weeds are serious threats to outcrops located near popular trails and overlooks.
Reference: Rawinski et al. (1996).
Click on the images below to open a larger image in a separate window.
 |
A Low-Elevation Acidic Outcrop Barrens community on massive exposures of biotite granite in
the southern Blue Ridge. Point Lookout Mountain, Grayson County.
Photo: Gary P. Fleming. |
REPRESENTATIVE COMMUNITY TYPES:
Vegetation belonging to this group has been described in field notes from several sites in western Virginia, but no quantitative data have been collected and no associations have been defined.
