Acidic Oak - Hickory Forests
Forests in this group are similar to those of the Basic Oak-Hickory Forests, but occupy submesic to subxeric upland sites over subacidic rocks such as siltstone, metasiltstone, shale, and certain granites. These forests are widely distributed throughout the Piedmont, inner Coastal Plain, mountain valleys, and lower mountain slopes of both the Blue Ridge and Ridge and Valley, up to about 600 m (2,000 ft) elevation. Hickories (Carya spp.) are less abundant than in the Basic Oak-Hickory Forests group but are nevertheless prominent, often primarily as understory trees. Dominant oaks include white oak (Quercus alba), black oak (Quercus velutina), scarlet oak (Quercus coccinea), southern red oak (Quercus falcata), and chestnut oak (Quercus montana, = Quercus prinus). Flowering dogwood (Cornus florida) is a characteristic, often abundant understory tree, although its numbers have been greatly reduced in recent decades by the fungal pathogen dogwood anthracnose (Discula destructiva). Deciduous ericads, especially lowbush blueberry (Vaccinium pallidum) and deerberry (Vaccinium stamineum), are usually present but patchy in the shrub layer, along with maple-leaved viburnum (Viburnum acerifolium). Herbaceous diversity is somewhat less than in Basic Oak-Hickory Forests but considerably greater than in Oak/Heath Forests. Typical herbs of these communities include plaintain-leaved pussytoes (Antennaria plantaginifolia), Pennsylvania sedge (Carex pensylvanica), whorled coreopsis (Coreopsis verticillata), poverty oatgrass (Danthonia spicata), common dittany (Cunila origanoides), rattlesnake weed (Hieracium venosum), large summer bluets (Houstonia purpurea), low St. Andrew's cross (Hypericum stragulum), whorled loosestrife (Lysimachia quadrifolia), violet woodsorrel (Oxalis violacea), gray beard-tongue (Penstemon canescens), solomon's-seal (Polygonatum biflorum var. biflorum), lion's foot (Nabalus serpentarius), wild pink (Silene caroliniana var. pensylvanica), silverrod (Solidago bicolor), wavy-leaved aster (Symphyotrichum undulatum, = Aster undulatus), and wood vetch (Vicia caroliniana).
Acidic Oak-Hickory Forests are ecologically intermediate between species-rich Basic Oak-Hickory Forests and floristically depauperate Oak/Heath Forests. They occupy less fertile soils and have lower species-richness and more ericaceous shrubs than do Basic Oak-Hickory Forests. They are distinguished from Montane Oak-Hickory Forests by their restriction to low-elevation or submontane habitats and corresponding composition consisting mostly of species that do not occur at higher elevations. Many contemporary stands of Acidic Oak-Hickory Forests are suffering from the effects of fire exclusion, including poor oak recruitment and the invasion of understories by fire-intolerant mesophytic species such as red maple (Acer rubrum), American beech (Fagus grandifolia), and blackgum (Nyssa sylvatica).References: Fleming (2002b), Fleming (2007), Fleming and Coulling (2001), Fleming and Moorhead (2000), Fleming and Patterson (2004), Gemborys (1974), Olson and Hupp (1986).
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White oak (Quercus alba), flowering dogwood (Cornus florida), and a patchy, graminoid-dominated herb layer are characteristic of many acidic oak-hickory forests. Great Falls Park, Fairfax County. Gary P. Fleming / © DCR Natural Heritage.
Large-diameter black oak (Quercus velutina) in a southern Piedmont acidic oak-hickory forest. Near Union Hill, Buckingham County (Cumberland State Forest). Gary P. Fleming / © DCR Natural Heritage.
DCR-DNH ecologists collecting plot data in a mature acidic oak-hickory forest near South Fork Quantico Creek, Prince William Forest Park, Prince William County. Gary P. Fleming / © DCR Natural Heritage.