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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



High-Elevation Outcrop Barrens

Communities in this group include scrub and herbaceous vegetation of exposed, metamorphic, igneous, and sedimentary outcrops in the Blue Ridge and, very locally, the Ridge and Valley province. The lower-elevation limit of these barrens is about 975 m (3,200 ft) in northern Virginia, increasing to about 1,200 m (4,000 ft) in the southern Blue Ridge. The full range of environmental and compositional variation in this group, especially in the southern Blue Ridge and Ridge and Valley occurrences, has not been documented. In the northern Blue Ridge, high-elevation outcrop barrens occupy granitic and metabasaltic outcrops of mostly west- to north-facing upper slopes and summits. Known examples in the southern Blue Ridge occur on amphibolite (Buffalo Mountain, Floyd Co.) and rhyolite (Mount Rogers area). While bedrock chemistry no doubt exerts some influence on floristics, geologically heterogeneous habitats share similar microclimatic and edaphic stresses. The habitats are wind-blasted and subject to severe winter temperatures and ice, while oligotrophic soils consist of very thin, local veneers of organic matter, gravel, or silt.

Vegetation is usually a patchwork of shrub thickets, herbaceous mats, and lithophytic lichens. Characteristic shrubs are American mountain-ash (Sorbus americana), red chokeberry (Aronia melanocarpa), black huckleberry (Gaylussacia baccata), pin cherry (Prunus pensylvanica), northern bush-honeysuckle (Diervilla lonicera), common ninebark (Physocarpus opulifolius var. opulifolius, on mafic outcrops), mountain laurel (Kalmia latifolia), and severely stunted yellow birch (Betula alleghaniensis). Typical herbs are cliff saxifrage (Hydatica petiolaris), Rand's goldenrod (Solidago randii), mountain sandwort (Minuartia groenlandica), Allegheny stonecrop (Hylotelephium telephioides), three-toothed cinquefoil (Sibbaldia tridentata), silverling (Paronychia argyrocoma), wavy hairgrass (Avenella flexuosa), Pennsylvania sedge (Carex pensylvanica), and Appalachian rock polypody (Polypodium appalachianum).

A number of remarkable, long-range boreal disjuncts, e.g., highland rush (Juncus trifidus), Appalachian fir clubmoss (Huperzia appressa), hemlock parsley (Conioselinum chinense), and narrow false-oats (Trisetum spicatum), are associated with these outcrops. Community types in this group are considered very rare in Virginia and globally. Threats include trampling and destruction of fragile vegetation mats and invasive introduced weeds such as flat-stemmed bluegrass (Poa compressa) and sheep-sorrel (Rumex acetosella).

References: Coulling and Rawinski (1999), Fleming and Coulling (2001), Fleming et al. (2007), Rawinski and Wieboldt (1993).



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

This link opens a new browser window to display a larger photo High-Elevation Acidic Heath Barren / Pavement on granite at the summit of Old Rag Mountain, Madison County (Shenandoah National Park). This vegetation type is characterized by patches of dwarfed ericaceous shrubs such as black huckleberry (Gaylussacia baccata) and mountain laurel (Kalmia latifolia). Photo © Gary P. Fleming.
This link opens a new browser window to display a larger photo High-elevation metabasalt (greenstone) barren on western flank of the Blue Ridge near Crescent Rocks, Page County (Shenandoah National Park). Photo: © Gary P. Fleming.
This link opens a new browser window to display a larger photo Outcrop barren dominated by mountain sandwort (Minuartia groenlandica, in flower), common hairsedge (Bulbostylis capillaris), and silverling (Paronychia argyrocoma), on the exfoliating granitic (leucocharnockite) dome of Spy Rock in Nelson County (George Washington and Jefferson National Forests). Gary P. Fleming / © DCR Natural Heritage.

REPRESENTATIVE COMMUNITY TYPES:

Five community types in this group are supported by analysis and classification of 42 plot samples (map). Representatives on igneous and metamorphic rocks of the northern Blue Ridge have been well documented. More work is needed to locate, sample, and classify high-elevation barrens of the southern Blue Ridge and Ridge and Valley. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.

  • Kalmia latifolia - Gaylussacia baccata - Vaccinium (angustifolium, pallidum) - Menziesia pilosa Shrubland
    Central Appalachian High-Elevation Heath Barren / Pavement
    USNVC: = CEGL003939
    Global/State Ranks: G2/S1

  • Minuartia groenlandica - Paronychia argyrocoma - Hydatica petiolaris Herbaceous Vegetation
    High-Elevation Outcrop Barren (Greenland Stitchwort Igneous / Metamorphic Type)
    USNVC: = CEGL008509
    Global/State Ranks: G1/S1

  • Aronia melanocarpa - Gaylussacia baccata / Carex pensylvanica Shrubland
    High-Elevation Outcrop Barren (Black Chokeberry Igneous / Metamorphic Type)
    USNVC: = CEGL008508
    Global/State Ranks: G1?/S1

  • Diervilla lonicera - Solidago randii - Avenella flexuosa - Hylotelephium telephioides - Hydatica petiolaris Herbaceous Vegetation
    High-Elevation Greenstone Barren
    USNVC: = CEGL008536
    Global/State Ranks: G1/S1

  • Salix occidentalis / Schizachyrium scoparium - Sibbaldia tridentata - Crocanthemum bicknellii - Rhynchospora globularis Shrub Herbaceous Vegetation
    Southern Blue Ridge High-Elevation Mafic Barren
    USNVC: = CEGL004238
    Global/State Ranks: G1/S1


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