Appalachian-Blue Ridge Forests

• Category: Forest Biomes.
• Geographic Location: North America.
• Summary: A stretch of forest covering much of the Appalachian Mountain range, this highly diverse and old ecosystem has been largely altered by human use.

Covering about 61,500 square miles (159,284 square kilometers) of northeastern Alabama, Georgia, eastern Tennessee, western North Carolina, Virginia, Maryland, central Pennsylvania, and northwest South Carolina, with small extensions in West Virginia, Kentucky, New Jersey, and New York, the Appalachian-Blue Ridge forests cover the highest parts of the central and southern Appalachian Mountain Range. These forests are delineated as an ecoregion by the World Wildlife Fund, meaning that they are a large stretch of land that contains characteristic, geographically distinct assemblages of natural communities and species. These forests derive their name from the Appalachian–Blue Ridge Mountains, so called because of their bluish color when seen from a distance. The trees on the mountains release isoprene gas into the atmosphere, giving them their characteristic smoky haze and namesake blue color.

The mountains that these forests adorn began forming more than 400 million years ago and were pushed higher when North America and Europe collided about 320 million years ago. The Appalachian Mountains have been heavily eroded over time, giving them a softer, more rolling look than younger, taller mountain ranges. This long evolutionary history, coupled with geologic stability, has helped these forests become some of the world’s richest areas of biodiversity. The habitat is important for many endemic species (those evolved locally and found nowhere else in the world). The area is made up of a large variety of land forms, climates, soil types, and geology, including areas of limestone that have eroded into karst formations, creating vast networks of caves. The long ridges and valleys of the Appalachian Mountains form barriers and corridors that protect species and aid in their movements. The north-to-south alignment of the mountain range has allowed species to shift their habitat range during ice ages and climate shifts.

Tree Species

The Appalachian-Blue Ridge forests are home to 158 species of trees, making them one of the most tree-diverse temperate forest regions in North America. At low elevations, the flora is dominated by deciduous oak forests, transitioning to coniferous spruce-fir forests about 4,000 feet (1,200 meters). Oak and hickory forests account for most of the Appalachian slope forests. Also common are grasses, shrubs, hemlocks, and mixed oak and pine forests. These forests cover the highest summits in the eastern United States, but despite this elevation, the mountaintop climate is still too warm to create an alpine zone; therefore, no tree line is present on the mountaintops. Instead, the forests generally extend all the way to the mountain peaks. The densest areas of forests tend to be stands of spruce and fir trees.

Animal Species

Many large animals call these forests home, including white-tailed deer (Odocoileus virginianus), American black bears (Ursus americanus), bobcats (Lynx rufus), coyotes (Canis latrans), and wild turkeys (Meleagris gallopavo). The forests also harbor many threatened and endangered species, including land snails, snakes, spiders, birds, and the Virginia big-eared bat (Corynorhinus townsendii virginianus), as well as 34 species of lungless plethodontid salamanders that breathe solely through their skin in the moist soils of the mountains.

In fact, the Shenandoah salamander (Plethodon shenandoah) has the most restricted range of any terrestrial vertebrate in North America, living solely on three mountaintops in Shenandoah National Park. Salamanders are likely the most abundant vertebrates in the region and account for the highest level of vertebrate biomass in any given patch of forest; therefore, they are extremely important for ecosystem function and nutrient cycling. The Appalachian-Blue Ridge forests have more species of salamanders than anywhere else in the world, reflecting their role as a global hotspot for plethodontid salamander diversity.

Threats From Human Activity

Many factors have made the Appalachian-Blue Ridge forests a unique ecosystem, but one that is increasingly threatened with alteration by logging, development, and mining. An estimated 83 percent of the Appalachian-Blue Ridge forest habitat has been altered by human activities. Much of it has been logged, cleared for agricultural, urban, and industrial development, or affected by mineral extraction. Valleys and low-elevation areas have been hardest hit, as they are the most accessible and desirable areas for agriculture and residential development.

Only small patches of the original forest biome remain. The largest remnant is in the Great Smoky Mountains National Park, which straddles the border of Tennessee and North Carolina. Many previously altered areas have regrown, such as Shenandoah National Park, which was once almost completely deforested and has since been allowed to regenerate in a largely undisturbed manner. Although these new-growth forests lack many of the large old trees and the historical species diversity of the original forests, they are still important areas for wildlife. Severe fragmentation of habitat in the region threatens species with isolation and increases the risk of inbreeding depression, which can contribute to extinction. Spruce and fir forests were especially heavily logged historically here and have not regenerated in many places. As a result, many mountain summits are covered with low, dense covers of evergreen shrubs; these are called Appalachian bald heaths.

Effects of Introduced Species

Introduced species have also altered the landscape of this forest ecosystem. Lower-elevation forests were historically dominated by a mix of oak and American chestnut trees (Castanea dentata). In the early 1900s, the chestnut blight—a disease caused by a pathogenic fungus (Cryphonectria parasitica) that was accidentally introduced through the importation of Asian chestnut trees—almost wiped out American chestnut populations. This disease changed the makeup of the forest forever, removing the chestnut as an important food source for wildlife and a valuable timber resource for humans.

Other introduced species—such as spongy moths (Lymantria dispar), a foliage-eating pest, and the hemlock woolly adelgid (Adelges tsugae), a sap-sucking insect—threaten the forest stands.

Removal of large predators such as wolves and mountain lions has allowed overpopulation of deer, placing further pressure on the forest through overgrazing. There is great concern about the overconsumption of acorns and oak seedlings by white-tailed deer populations, which are preventing the recruitment of new oak trees in forests. This selective overconsumption may cause a shift in the makeup of affected forests from oak-dominated to maple-dominated within the next few decades.

Other Environmental Stresses

Higher-elevation trees are more exposed to the effects of climate change, acid deposition, and air pollution. Mountain summits are also vulnerable to mountaintop-removal mining—a process in which the upper layers of rock and soil are blasted off to allow access to the underlying seams of coal. The overburden or excess removed soil is then either replaced in an attempt to restore the original contours of the mountain or dumped into neighboring valleys. Although this procedure is perhaps an effort toward developing an economical source of energy that is an alternative to oil, its environmental effects have raised many concerns.

Soil that is dumped into neighboring valleys chokes streams and destroys sensitive ecosystems. In 2010, studies found that nearly 2,000 miles of streams had been damaged from mountaintop removal. Even when soil is replaced on the summit, it is often taken over by nonnative vegetation, and the original biodiversity is unlikely to be restored. There is also concern about the health effects of contaminated stream water, airborne toxins, and dust on humans and wildlife alike.

Conservation Efforts

Much of the remaining land in the Appalachian-Blue Ridge forests has been purchased by state and federal governments and set aside as protected forests and parks. Most of these lands are mandated to be managed under a multiple-use management plan, mixing timber harvest regimes with recreation and wildlife purposes. Many sustainable timber harvest programs help encourage healthy succession in forests. Policy discussions have raised concerns that expanded federal logging initiatives could increase timber harvesting and road construction in portions of the Appalachian region, including areas of the Cherokee National Forest, potentially contributing to forest fragmentation and reduced ecological resilience. Seasonal hunting in forests and parks is also used to control white-tailed deer populations and prevent overgrazing and population-density pressures.

The Appalachian-Blue Ridge forests are traversed by the Appalachian Trail, which begins in Georgia and ends in Maine, giving hikers and campers access to these beautiful forests. Future changes in public demand may steer forest management away from consumptive uses and toward viewsheds, camping, hiking, and biodiversity protection. Conservation initiatives highlight ongoing biodiversity and species-recovery efforts in the Appalachian-Blue Ridge forests, including genomic and breeding programs aimed at restoring the blight-decimated American chestnut, continued protection of the region’s globally significant lungless salamander diversity, and restoration of high-elevation red spruce–Fraser fir ecosystems that provide critical habitat for rare species such as the Carolina northern flying squirrel.

Bibliography

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Frick-Ruppert, Jennifer. Mountain Nature: A Seasonal Natural History of the Southern Appalachians. University of North Carolina Press, 2010.

Hoekstra, J. M., et al., editors. The Atlas of Global Conservation: Changes, Challenges, and Opportunities to Make a Difference. University of California Press, 2010.

Kay, Mike. “Nature Notes: The Diversity of the Appalachian Blue Ridge Forest.” Frederick News, 8 Jan. 2022, www.fredericknewspost.com/places/local/frederick_county/nature-notes-the-diversity-of-the-appalachian-blue-ridge-forests/article_fe1b31a9-223e-5dc0-ba5a-2eb8781f6741.html. Accessed 2 Nov. 2024.

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Spira, Timothy. Wildflowers and Plant Communities of the Southern Appalachian Mountains and Piedmont. University of North Carolina Press, 2011.