Mountain / Piedmont Acidic Cliffs
This group contains sparse woodland, scrub, and herbaceous vegetation of very steep to precipitous sandstone, acidic shale, and quartzite outcrops, cliffs, and rocky escarpments. These communities are scattered throughout the mountain and western Piedmont foothill regions of Virginia, but are poorly inventoried and documented at present. Acidic cliffs occur under several geomorphic conditions, especially on slopes undercut by large streams or rivers and on resistant caprock exposed by differential weathering of weaker underlying strata. Habitats vary with aspect and other environmental conditions. Local zones of ephemeral seepage may be present. The vegetation is generally dominated by lichens, with the umbilicate "rock tripe" species of Umbilicaria and Lasallia especially prominent. Vascular plants are confined to crevices and humus-covered shelves. On drier, south- to west-facing cliffs, vascular species may be very sparse and consist of stunted pines (Pinus virginiana, Pinus pungens, and/or Pinus rigida) ericaceous shrubs, and occasional herbaceous lithophytes such as mountain spleenwort (Asplenium montanum), silverling (Paronychia argyrocoma), and wild bleeding heart (Dicentra eximia). Sheltered, north- to east-facing cliffs often support more diverse shrub and herbaceous flora. Characteristic species include stunted eastern hemlock (Tsuga canadensis), evergreen rhododendrons (Rhododendron maximum and Rhododendron catawbiense), rock polypodies (Polypodium appalachianum and Polypodium virginianum), cliff saxifrage (Hydatica petiolaris), rock alumroot (Heuchera villosa var. villosa), and wavy hairgrass (Avenella flexuosa). Shaded grottoes and "rock houses" on cliffs of the Cumberland Mountains in southwestern Virginia support colonies of small-flowered alumroot (Heuchera parviflora) and round-leaf catchfly (Silene rotundifolia). There are few threats to acidic cliffs, except for local damage by rock climbers.
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|Massive cliff of Antietam quartzite on North Fork Mountain in Pendleton County, West Virginia. Similar exposures are characteristic of the Central Appalachian Ridge and Valley province from western Virginia and eastern West Virginia to Pennsylvania.
Photo © Gary P. Fleming.
|Xeric sandstone cliff on Pickem Mountain in the Cumberland Mountains, Wise County (George Washington and Jefferson National Forests). Photo: Tom Rawinski.|
|Weathered quartzite cliff on Bull Run Mountain, a Piedmont monadnock in Fauquier County. The umbilicate lichen Lasallia pensylvanica abundantly covers the exposed rock faces. Photo © Gary P. Fleming.|
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