Oak / Heath Forests
This group of oak-dominated forests is prominent on xeric, infertile upland sites in every physiographic province of Virginia, and is wide-ranging in the Appalachians and adjacent provinces outside of the Commonwealth. In some cases, particularly in the mountains and foothills, these communities have replaced former mixed oak - American chestnut (Castanea dentata) forests following the decimation of chestnut overstory trees by an introduced fungal blight (Cryphonectria parasitica) early in the twentieth century. Habitats are variable, ranging from sterile, low-elevation "flatwoods" to steep, rocky mountainsides. All have soils with a distinctly oligotrophic nutrient regime, i.e ., strongly acidic, with low base cation levels and relatively high levels of iron. Accumulations of thick duff and high biomass of inflammable shrubs in these forests make them susceptible to periodic fires, which in turn favors recruitment of oaks. Regionally varying mixtures of white oak (Quercus alba), chestnut oak (Quercus montana, = Quercus prinus), scarlet oak (Quercus coccinea), black oak (Quercus velutina), northern red oak (Quercus rubra), southern red oak (Quercus falcata), and post oak (Quercus stellata) compose the overstories of these forests. Bigtooth aspen (Populus grandidentata) and pines - including pitch pine (Pinus rigida) in the mountains, shortleaf and Virginia pines (Pinus echinata and Pinus virginiana) in the Piedmont, and loblolly pine (Pinus taeda) in the Coastal Plain - are common associates that usually indicate past disturbance. Hickories (Carya spp.) are generally unimportant and mostly restricted to the understory.
Forests overwhelmingly dominated by chestnut oak (Quercus montana, = Quercus prinus) are widespread on sandstone or quartzite ridges in the mountains, but occur locally on monadnocks, foothills, and rocky or gravelly bluffs throughout the Piedmont and inner Coastal Plain. Blackgum (Nyssa sylvatica) and sourwood (Oxydendrum arboreum) are frequent overstory associates and abundant understory trees, along with sassafras (Sassafras albidum) and downy serviceberry (Amelanchier arborea var. arborea). Decades of fire suppression or exclusion has led to a general abundance of the fire-intolerant red maple (Acer rubrum) in oak / heath forest understories. Ericaceous (heath-family) plants, including mountain-laurel (Kalmia latifolia), black huckleberry (Gaylussacia baccata), wild azalea (Rhododendron periclymenoides), and blueberries (Vaccinium spp.), form dense colonies in the shrub and herb layers. Evergreen rhododendrons (Rhododendron maximum and Rhododendron catawbiense) and flame azalea (Rhododendron calendulaceum) are locally prevalent members of the ericaceous shrub complex in the mountains, while dangleberry (Gaylussacia frondosa) is a prominent ericad in the Coastal Plain. The ericaceous sub-shrubs trailing arbutus (Epigaea repens) and wintergreen (Gaultheria procumbens) may also be abundant, especially in the mountains. The density of ericaceous species may be closely tied to land-use and disturbance history. True herbaceous species are sparse, but may include scattered individuals or colonies of xerophytes such as galax (Galax urceolata), yellow wild-indigo (Baptisia tinctoria), pink lady's-slipper (Cypripedium acaule), dwarf iris (Iris verna), large whorled pogonia (Isotria verticillata), one-flower cancer-root (Orobanche uniflora), gay-wing milkwort (Polygala paucifolia), bracken fern (Pteridium aquilinum var. latiusculum), and goat's-rue (Tephrosia virginiana).
Community types in this group constitute a widespread element of large-patch vegetation in Virginia's landscape. Although still relatively extensive, they are subject to multiple disturbances, including clear-cutting, conversion to pine plantation silvicultures, gypsy moth infestation, fire suppression, and destruction by development. However, a number of chestnut oak-dominated stands on dry mountain ridges in Virginia have escaped cutting because of the stunted growth and poor form of the overstory trees.References: Abrams et al . (1997), Adams and Stephenson (1983), Allard and Leonard (1943), Clark and Ware (1980), Cole and Ware (1997), Coulling and Rawinski (1999), Crouch (1990), Farrell and Ware (1988), Fleming (2002a), Fleming (2002b), Fleming (2007), Fleming and Coulling (2001), Fleming and Moorhead (1996), Fleming and Moorhead (2000), Fleming and Weber (2003), Gemborys (1974), Harrison et al . (1989), Johnson and Ware (1982), Martin et al . (1982), McCoy and Fleming (2000), McEvoy et al . (1980), Olson and Hupp (1986), Orwig and Abrams (1994), Rawinski et al . (1994), Rawinski et al . (1996), Rhoades (1992), Rhoades (1995), Rhoades (2002), Stephenson (1974), Stephenson (1982a), Stephenson and Adams (1991), Stephenson and Fortney (1998), Vanderhorst (2000), Walton et al. (2001), Ware (1991).
Click on the images below to open a larger image in a separate window.
|A typical montane oak/heath forest with an overstory of chestnut oak (Quercus montana) and a low shrub layer of black huckleberry (Gaylussacia baccata). The multiple-stem growth form of the oaks is the result of stump-sprouting following logging. Kennedy Peak, Massanutten Mountains, Page County (George Washington and Jefferson National Forests). Photo: © Gary P. Fleming|
|Oak/heath forest with chestnut oak (Quercus montana, turning yellow), scarlet oak Quercus coccinea , turning red), mountain laurel (Kalmia latifolia), and deciduous ericads. Near Turk Gap, Albemarle County (Shenandoah National Park). Photo (c) Gary P. Fleming.|
|Scarlet oak (Quercus coccinea) and mountain-laurel (Kalmia latifolia)-dominated oak / heath forest with a history of fire and cutting. Great Falls Park, Fairfax County. Gary P. Fleming / © DCR Natural Heritage.||The brilliant fall color of black huckleberry (Gaylussacia baccata) suffuses the shrub layer of a central Piedmont oak/heath forest in Fluvanna County. Photo: © Gary P. Fleming|
More than 300 plots of this vegetation have been sampled in Virginia (map), and nine community types classified in the course of several regional analyses. Most of these finer-level units are clearly distinguished by strong geographic/elevational gradients and associated floristic differences. However, the putative separation of "Central Appalachian" and "Southern Appalachian" units is particularly problematic in western Virginia, where the floras of these biogeographic regions often merge insensibly. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.
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