Basic Oak - Hickory Forests
The principal habitats for Basic Oak-Hickory Forests in Virginia are submesic to subxeric uplands over basic rocks such as diabase, gabbro, amphibolite, and metabasalt (greenstone). Soils range from moderately acidic to circumneutral and have moderately high levels of calcium, magnesium, manganese, iron, and aluminum. The term "basic," as applied by DCR-DNH ecologists, refers high levels of base cation saturation rather than to soil pH, which analysis has proven to be a less reliable indicator of fertility and parent material. Communities in this group are scattered to locally extensive throughout the Virginia Piedmont and on lower-elevation slopes of the northern Blue Ridge; their distribution in adjacent areas of the state is uncertain. The largest patches of this vegetation occur in the Piedmont Triassic basins; on the more extensive intrusions of mafic and ultramafic formations elsewhere in the Piedmont; and on soils derived from metabasalt (greenstone) in the Blue Ridge and its foothills.
Overstory composition varies regionally, but is generally characterized by mixtures of white oak (Quercus alba), northern red oak (Quercus rubra), black oak (Quercus velutina), chestnut oak (Quercus montana, = Quercus prinus), post oak (Quercus stellata), pignut hickory (Carya glabra), red hickory (Carya ovalis), shagbark hickory (Carya ovata), mockernut hickory (Carya tomentosa), white ash (Fraxinus americana), and tulip-tree (Liriodendron tulipifera). Hickories are especially abundant in these forests and may dominate some stands. Dominance by tulip-tree usually follows heavy logging or other catastrophic disturbances. Eastern redbud (Cercis canadensis var. canadensis), eastern hop-hornbeam (Ostrya virginiana), and flowering dogwood (Cornus florida) are common understory species. Herb layers are typically patchy but species-rich and support diverse mixtures of both mesophytic and dry-site species. In the spring, small geophytes such as cut-leaf toothwort (Cardamine concatenata), rue-anemone (Thalictrum thalictroides), star chickweed (Stellaria pubera), and spring beauty (Claytonia virginica var. virginica) frequently carpet the ground layers of these oak-hickory forests. The summer and fall aspect is dominated by forbs and grasses such as woodland agrimony (Agrimonia rostellata), four-leaf milkweed (Asclepias quadrifolia), curlyheads (Clematis ochroleuca), Bosc's panic grass (Dichanthelium boscii), naked-flowered tick-trefoil (Hylodesmum nudiflorum), bottlebrush grass (Elymus hystrix), bedstraws (particularly Galium circaezans and Galium latifolium), eastern solomon's-plume (Maianthemum racemosum ssp. racemosum), rock muhly (Muhlenbergia sobolifera), goldenrods (particularly Solidago caesia var. caesia and Solidago ulmifolia), yellow pimpernel (Taenidia integerrima), lesser horse-gentian (Triosteum angustifolium), and wood violet (Viola palmata).
Basic Oak-Hickory Forests occupy more fertile soils and have higher species-richness and fewer ericaceous shrubs than do Acidic Oak-Hickory Forests. They are distinguished from Montane Oak-Hickory Forests by their restriction to low-elevation habitats and corresponding composition consisting mostly of species that do not occur at higher elevations. With a distribution in the Piedmont already restricted by limited available habitat, Basic Oak-Hickory Forests have also been reduced considerably by a long history of agriculture, conversion of hardwood forests to intensively managed pine stands, and urban development. Some of the community types in this group can be considered uncommon or rare in the state.References: Farrell and Ware (1991), Fleming (2002a), Fleming (2002b), Fleming and Coulling (2001), Fleming and Patterson (2004), Fleming and Weber (2003), Ware (1991), Ware (1992).
Click on the images below to open a larger image in a separate window.
|Northern Hardpan Basic Oak-Hickory Forest is typical of diabase "flatwoods" in the northern Virginia Culpeper Basin. The grass rock muhly (Muhlenbergia sobolifera) dominates the herb layer. Near Elklick Run, Fairfax County (Fairfax County Park Authority lands).Photo: Gary P. Fleming|
|Southern Piedmont Basic Oak-Hickory Forest dominated by white oak (Quercus alba) and shagbark hickory (Carya ovata), with a diverse herb layer of forest grasses, sedges, and forbs. Near Trents Mill, Cumberland County (Cumberland State Forest). Photo: © Gary P. Fleming.|
This ecological group is very well represented by quantitative data and its division into community types is supported by regional analyses of 140 plot samples (map). Basic Oak-Hickory Forests comprise some of Virginia's most species-rich vegetation, and the units that have been defined are separated largely by geography and subtle floristic differences that can be difficult to distinguish in the field. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer
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