High-Elevation Boulderfield Forests and Woodlands
These open forests and woodlands occupy relatively unweathered boulderfields at elevations above 900 m (3,000 ft) in both the Blue Ridge and Ridge and Valley provinces. Communities in this group are known to occur from West Virginia south to northern Georgia. In Virginia, yellow birch (Betula alleghaniensis), American mountain-ash (Sorbus americana), and mountain maple (Acer spicatum) are the typical dominants of boulderfields weathered from granite, metabasalt, rhyolite, quartzite, and sandstone at the highest elevations. These habitats are usually best developed on north-facing slopes, where extreme winter temperatures, high winds, and ice storms strongly influence forest physiognomy. Trees here are typically gnarled and widely spaced because of difficult establishment and repeated damage from wind and ice. Typical shrubs include gooseberries (Ribes cynosbati, Ribes glandulosum, Ribes rotundifolium), hobblebush (Viburnum lantanoides), red raspberry (Rubus idaeus var. strigosus), and red-berried elder (Sambucus racemosus var. pubens , = Sambucus pubens). The high cover of exposed rock in these habitats tends to limit overall species richness and herbaceous density. However, the Appalachian rock polypody (Polypodium appalachianum) is often abundant. Additional herbaceous species such as yellow blue-bead lilly (Clintonia borealis), whorled wood aster (Oclemena acuminata = Aster acuminatus), Appalachian oak fern (Gymnocarpium appalachianum), marbled alumroot (Heuchera pubescens), brownish sedge (Carex brunnescens, and summer sedge (Carex aestivalis) may occur where substrate conditions are suitable. Cool microclimates favor the occurrence of many northern and high mountain species.
The globally rare and federally listed Shenandoah salamander (Plethodon shenandoah) is endemic to three thinly wooded, high-elevation boulderfields on the northern Blue Ridge (Page and Madison Counties).This group is readily distinguished from Low-Elevation Boulderfield Forests and Woodlands by the near-complete dominance of northern and Southern Appalachian species that are confined to microclimatically cool habitats.
References: Fleming and Coulling (2001), Fleming et al. (2007), Johnson and Ware (1982), Rheinhardt and Ware (1984).
Click on the images below to open a larger image in a separate window.
|High-Elevation Boulderfield Forest dominated by ice- and wind-blasted yellow birch (Betula alleghaniensis), on a large-block metabasalt (greenstone) boulderfield near Big Meadows, Page County (Shenandoah National Park). Gary P. Fleming / © DCR Natural Heritage.|
|American mountain-ash (Sorbus americana) on a scrubby metabasalt (greenstone) boulderfield of Stony Man, Page County (Shenandoah National Park). Gary P. Fleming / © DCR Natural Heritage.|
|Gnarled yellow birch (Betula alleghaniensis) on a sandstone boulderfield, north slope of Elliott Knob, Augusta County (George Washington and Jefferson National Forests). Gary P. Fleming / © DCR Natural Heritage.|
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