Southern Appalachian Low-Elevation Pine Forest

This ecological system consists of Pinus echinata- and Pinus virginiana-dominated forests in the lower elevation Southern Appalachians and adjacent Piedmont and Cumberland Plateau, extending into the Interior Low Plateau of Indiana, Kentucky and Tennessee. Examples can occur on a variety of topographic and landscape positions, including ridgetops, upper and midslopes, as well as lower elevations (generally below 700 m [2300 feet]) in the Southern Appalachians such as mountain valleys. Examples occur on a variety of acidic bedrock types. Frequent, low-intensity fires coupled with severe fires may have been the sole factor favoring the occurrence of this system instead of hardwood forests in the absence of fire. Under current conditions, stands are dominated by Pinus echinata or Pinus virginiana. Pinus rigida may sometimes be present. Hardwoods are sometimes abundant, especially dry-site oaks such as Quercus falcata, Quercus montana, and Quercus coccinea, but also Carya glabra, Acer rubrum, and others. The shrub layer may be well-developed, with Gaylussacia baccata, Kalmia latifolia, Rhododendron minus, Vaccinium pallidum, or other acid-tolerant species most characteristic. Herbs are usually sparse but may include Pityopsis graminifolia and Tephrosia virginiana.

Vegetation consists of closed to open forests or woodlands dominated by Pinus echinata or Pinus virginiana. Pinus rigida may sometimes be present. Hardwoods are sometimes abundant, especially dry-site oaks such as Quercus falcata, Quercus montana (= Quercus prinus), and Quercus coccinea, but also Carya glabra, Acer rubrum, and others. An extensive hardwood component may partly be the result of fire suppression. The shrub layer may be well-developed, with Vaccinium pallidum, Gaylussacia baccata, or other acid-tolerant species most characteristic. Herbs are usually sparse but may include Pityopsis graminifolia and Tephrosia virginiana. Herbs probably were more abundant and shrubs less dense when fires occurred more frequently, and the communities of this system may have been grassy under more natural conditions, with Schizachyrium scoparium being a typical component, possibly with Danthonia sp.

This system occurs on ridgetops, upper and midslopes, in mountain valleys and the lower ranges. It is found on south- and southwest-facing slopes (Whittaker 1956). Bedrock may be a variety of types, but the system may be limited to acidic substrates. Fire is undoubtedly a very important and necessary influence.

Fire is clearly an important influence on the dynamics of this ecological system, and frequent, low-intensity fires coupled with occasional severe fires (Harrod and White 1999, Fesenmyer and Christenson 2010) are thought to have been the primary factor leading to the occurrence of this system rather than hardwood forests on dry sites in the absence of fire. Fires probably were frequent and of low intensity, or a mix of low and higher intensity. Over many decades, accumulation of dead biomass can predispose these forests to catastrophic fire. However, even in the absence of fire, successional changes are normally restricted (possibly ending with oak domination) because most sites are infertile and dry (Murphy and Nowacki 1997). Fire probably is important for determining the dominance of pine species, the component of hardwoods, and the overall vegetation structure. Pinus echinata is fairly resilient to fire once mature, while Pinus virginiana individuals are fairly susceptible to fire but well-adapted to establishing in areas opened by intense fire.

Southern pine beetles (Dendroctonus frontalis) are an important disturbance and threat in this system, at least under present conditions and severe outbreaks can kill all the pines without creating the conditions for the pines to regenerate. Effects of logging and past clearing as well as lack of fire make understanding of this system's natural character and dynamics difficult. An extensive hardwood component may partly be the result of lack of fire. Some pine-dominated areas appear to be successional stands established in former hardwood forests after logging or cultivation, and would not be expected to have the same dynamics or ecosystem characteristics as natural pine forests maintained by fire. In natural pine forests, with adequate seed and seedlings, logging may allow pines to regenerate or, without adequate seedlings and with lack of fire may lead to a change in composition to hardwoods. This might also alter canopy composition as well as structure. In many cases, several prescribed fires or a combination of fire and thinning treatments will be necessary to restore these ecosystems (Elliott and Vose 2005).

Southern pine beetles (Dendroctonus frontalis) are an important disturbance and threat in this system, especially to the Pinus echinata trees, at least under present conditions. Lack of fire has contributed to the loss of this ecological system. Without fire, the development of a closed forest canopy can lead to declines in the native herbaceous ground cover vegetation. Clearcut logging of Pinus echinata and forest succession by hardwood trees, Pinus virginiana and/or Pinus taeda are threats to the very limited extent of Pinus echinata forests. Pinus echinata woodlands have declined due to conversion to intensively managed pine plantations, especially on the Cumberland Plateau. Often sites have been replanted with Pinus taeda, and are then no longer burned for forest management.

This system is found primarily in the Appalachian regions of Kentucky and the Southern Blue Ridge in northern Georgia, western North Carolina, southeastern Tennessee, the Cumberlands of Alabama, parts of the Interior Low Plateau (e.g., the Knobs Region of Kentucky and southern Indiana and the western Highland Rim of Tennessee), and southwestern Virginia. Any possible stands in the Piedmont would be found in the western foothills portions adjacent to the mountains.