Appalachian High Elevation Oak Forest

This generally oak-dominated system is found in the central and southern Appalachian Mountains. These high-elevation deciduous forests occur on exposed sites, including ridgecrests and south- to west-facing slopes, mostly between 915 and 1372 m (3000-4500 feet) elevation, less commonly ranging up to 1680 m (5500 feet). In most associations attributed to this system, the soils are thin, weathered, nutrient-poor, low in organic matter, and acidic. The forests are dominated by Quercus spp. (most commonly Quercus rubra and Quercus alba), with the individual trees in high-elevation red oak examples often stunted or wind-flagged. Castanea dentata sprouts are also common, but the importance of chestnut in these forests has been dramatically altered by chestnut blight. Ilex montana, Hamamelis virginiana, and Rhododendron prinophyllum (in Virginia and West Virginia) are characteristic shrubs.

Examples of this system may be dominated by Quercus rubra in some cases, and by Quercus alba and/or Quercus montana (= Quercus prinus) in others. The trees may be stunted, or at least not as tall as they would be in other systems farther downslope. Species richness is low to moderate. Tree associates include Prunus serotina, Acer rubrum, Betula lenta, and Betula alleghaniensis. Typical small trees and shrubs include Ilex montana, Hamamelis virginiana, Acer pensylvanicum, Menziesia pilosa, Rhododendron prinophyllum, Vaccinium pallidum, Corylus cornuta var. cornuta, and sprouts of Castanea dentata. The understory is usually dominated by ericaceous shrubs, but some communities are dominated by graminoid species or ferns. Dennstaedtia punctilobula, Carex pensylvanica, and Deschampsia flexuosa are common. Only rarely are the communities dominated by other herbs.

The habitat for this system includes high ridgelines and exposed upper slopes, primarily on south- to west-facing aspects, mostly between 915 and 1372 m (3000-4500 feet) elevation, and less commonly ranging up to 1680 m (5500 feet).It generally occurs as a transition between Southern Appalachian Oak Forest (CES202.886) and more mesic Southern Appalachian Northern Hardwood Forest (CES202.029) that occurs on less-exposed ridgetops and cooler, moister upper slopes (e.g., north- and east-facing aspects). At high elevations (e.g., above 1372 m [4500 feet]), this system is generally less common than Southern Appalachian Northern Hardwood Forest (CES202.029), since the habitat on most slopes at this elevation tends to favor those species adapted to a more mesic environment. Rockslides occur periodically due to the steep slopes, and severe rockslides can cause stand replacement. Ice storms occur frequently and cause extensive damage to older dwarfed trees. Fire occurs at moderate frequency and probably needed in the long run to promote growth of fire tolerant Quercus and maintain their dominance. Some rare examples may be too rocky to burn, and even these have mostly closed canopies and produce a substantial leaf litter layer in most places (M. Schafale pers. comm. 2013).

The communities of this system occur on exposed high ridges in the Appalachians. They are subject to frequent ice in winter, wind storms in the summer and high winds throughout the year. Natural old-growth forest examples have trees reproducing in small to medium-sized canopy gaps created by the death of individual or small groups of trees. Wind and ice storms are the main cause of tree mortality. Breakage of trees and of branches by ice storms can additionally produce partial canopy opening over large areas (M. Schafale pers. comm.). In addition, lightning-caused fires may create surface fires that change the understory composition and inhibit some ericaceous shrub species in some areas. Fire is naturally at moderate or low frequency, but appears to be important in structuring the vegetation. In many locations, fire exclusion and competing understory vegetation are factors in poor oak regeneration, with replacement by more mesophytic species such as Acer saccharum (Fleming et al. 2005). Fire likely was crucial for reducing the competitive advantage of these species. Presettlement forests are likely to have experienced lightning-caused fires every 40-60 years (Fleming et al. 2005). Fires likely were more frequent than this farther south. Rockslides cause severe disturbance in occasional locations, initiating a primary succession that may last many years. Despite the high elevation, Castanea dentata had been a fairly substantial component of this system and can still be seen as rotting stumps in the forest.

The most evident threat to this system is the decline and subsequent mortality of the dominant and characteristic canopy Quercus species, particularly Quercus rubra (Greenberg et al. 2011). High oak mortality rates and widespread oak regeneration failure threaten the long-term survival of these forests. Oak decline will continue to be a forest health problem, particularly on national forest lands. Oaks will not be eliminated from affected areas, but their numbers and diversity will be reduced. Red maple, blackgum, and other relatively shade-tolerant species are likely to replace the oaks (Southern Group of State Foresters 2013). Oak decline results from a number of stress factors, including the low-quality site conditions (rocky and shallow soils), drought (intensified by climate change), defoliation by insect pests, root diseases, unusual late frosts (again perhaps made more frequent by climate change), and stand disturbances (Greenberg et al. 2011). In the Northern Blue Ridge, Spongy Moth (Lymantria dispar) infestations have caused widespread tree mortality and pose a threat to these systems (Fleming et al. 2005). This threat is likely to continue spreading southward and is a potential threat throughout the range of this system. These are higher elevation forests where development and fragmentation pressures are less than at moderate to low elevations. Climate change is likely somewhat of a threat. Warmer temperatures are likely to cause vegetation zones to shift upward in elevation, which will reduce the area of available habitat for this system in many places.

This system is found at higher elevations of the central and southern Appalachian Mountains, Virginia and West Virginia to Georgia. In Kentucky, this system is restricted to the Cumberland Mountains in the extreme southeastern corner of that state. In West Virginia, this system is found in the Ridge and Valley.