Like seepage swamps, communities of this group occupy flat to gently sloping zones of groundwater discharge along valley floors and headwaters streams in the mountain region of Virginia. Stand physiognomy, however, is more open and characterized by saturated woodland, shrubland, and herbaceous vegetation with a dense graminoid component. Appalachian Bogs are scattered in the Central and Southern Appalachians, from Pennsylvania and western Maryland, south to Georgia and west into Kentucky. In Virginia, habitats supporting bogs are usually less than 0.4 ha (1 ac) in size, but rarely range up to 4 ha (10 ac) in the southern Blue Ridge (Mount Rogers area) and southwest Ridge and Valley region. Fewer than twenty occurrences have been documented in the state. Soils, which vary from wholly mineral in composition to superficial or deep peat, are extremely acidic and support thick growths of Sphagnum and other mosses. The term "bog," as applied to these wetlands, is a technical misnomer, since not all of these habitats are true peatlands and none is an ombrotrophic system. This term, however, is now so widely used in the southeastern United States as a descriptor for open, acidic seepage wetlands (particularly those with abundant Sphagnum) that we have adopted it here for consistency (see Weakley and Schafale (1994) for additional discussion). The ecological dynamics of these naturally rare communities are not well understood, and many examples are currently suffering from shrub and tree invasions. Factors that may have been responsible for creating and maintaining open bogs include fire, grazing, beavers, and deep deposition of unstable soils.
Bog vegetation is frequently a mosaic of tree or shrub patches and herbaceous openings. Several compositional variants associated with geography and elevation have been documented in Virginia. Species common to most variants include great rhododendron (Rhododendron maximum), Catawba rhododendron (Rhododendron catawbiense), silky willow (Salix sericea), smooth alder (Alnus serrulata), cinnamon fern (Osmundastrum cinnamomeum var. cinnamomeum), tawny cottongrass (Eriophorum virginicum), prickly bog sedge (Carex atlantica), Fraser's marsh St. Johns-wort (Hypericum fraseri) , and brownish beaksedge (Rhynchospora capitellata). Species more restricted to low-elevation (below 900 m [3000 ft]) bogs of the Ridge and Valley and Cumberland Mountains include pitch pine (Pinus rigida), round-leaved sundew (Drosera rotundifolia var. rotundifolia), bushy bluestem (Andropogon glomeratus var. glomeratus), tussock sedge (Carex stricta), tuberous grass-pink (Calopogon tuberosus), yellow fringed orchid (Platanthera ciliaris), and Nuttall's reed-grass (Calamagrostis cinnoides). Species more restricted to higher-elevation (mostly above 900 m [3000 ft]) bogs of the southern Blue Ridge, Allegheny Mountains, and/or the highest mountains of the Ridge and Valley include stunted red spruce (Picea rubens), long-stalked holly (Ilex collina), northern wild raisin (Viburnum cassinioides), Carolina laurel (Kalmia carolina), cranberry (Vaccinium macrocarpon), rough-leaved goldenrod (Solidago patula var. patula), Cuthbert's turtlehead (Chelone cuthbertii), bog goldenrod (Solidago uliginosa var. uliginosa), star sedge (Carex echinata ssp. echinata), narrow-leaf bur-reed (Sparganium emersum), bog willow-herb (Epilobium leptophyllum), narrow-panicled rush (Juncus brevicaudatus), three-seeded sedge (Carex trisperma), Ruth's sedge (Carex ruthii), and thyme-leaf bluets (Houstonia serpyllifolia).References: Chappell (1972), Fleming and Coulling (2001), Musselman (1970), Ogle (1982), Fleming and Moorhead (1996).
Click on the images below to open a larger image in a separate window.
|Central Appalachian Pitch Pine Bog along North Fork of Stony Creek near Kire, Giles County (George Washington and Jefferson National Forests). Gary P. Fleming / © DCR Natural Heritage.|
|Tawny cottongrass (Eriophorum virginicum) fruiting in a high-elevation, Southern Appalachian shrub bog. Headwaters of Big Wilson Creek, Grayson County (Grayson Highlands State Park). Photo: Gary Fleming.|
|High-elevation bog at the headwaters of Buck Run on Allegheny Mountain in Highland County (George Washington and Jefferson National Forests). Dominants include northern lowbush blueberry (Vaccinium angustifolium), three-seeded sedge (Carex trisperma), and bog goldenrod (Solidago uliginosa var. uliginosa, flowering). Photo: Gary Fleming.|
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