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NATURAL HERITAGE

THE NATURAL COMMUNITIES OF VIRGINIA
CLASSIFICATION OF ECOLOGICAL COMMUNITY GROUPS


Second Approximation (Version 2.6)
Information current as of July, 2013



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 are often steeply sloping pavements with warm aspects. They 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), cliff saxifrage (Hydatica petiolaris), little bluestem (Schizachyrium scoparium var. scoparium), broomsedge (Andropogon virginicus var. virginicus), Pennsylvania sedge (Carex pensylvanica), poverty oatgrass (Danthonia spicata), and silky oatgrass (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. Gary P. Fleming / © DCR Natural Heritage.

REPRESENTATIVE COMMUNITY TYPES:

Vegetation belonging to this group has been described in field notes from several sites in western Virginia, but only two plots have been sampled. At least some of our occurrences fit reasonably well into the broadly defined USNVC community type below. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.


  • Hydatica petiolaris Herbaceous Vegetation
    Appalachian Low-Elevation Acidic Outcrop Barren (Cliff Saxifrage Type)
    USNVC: = CEGL004524
    Global/State Ranks: G3?/S2?


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