The Cumberland Plateau contains one of the largest tracts of temperate hardwood forest in the world, housing a remarkable variety of aquatic and terrestrial species. Cumberland Plateau forests are some of the most diverse in the United States, on par with the California Redwoods and tropical forests of Hawaii.

Although logging between 1880 and 1930 removed much of the original tree cover, forests on the Plateau have gone through a second growth period and most soils retain soil structure capable of supporting healthy forests. The combination of original forest fragments and areas of healthy second growth provide essential habitat to larger animals like elk and black bear and smaller animals like songbirds and bats.

The Cumberland Plateau is roughly 1000 feet higher in elevation than the Eastern Highland Rim to the west (near Nashville, TN) and the ridge and valley area to the east (near Knoxville, TN).  This elevation difference provides a variety of conditions under which diverse forest types can flourish.  Most of the north-facing slopes on the escarpment (sides of the Plateau) and upland depressions are comprised of mixed mesophytic forest containing beech, sugar maple, tulip poplar, and ash. Hemlock is also present. On drier south-facing slopes of the escarpment and south-facing, upland ridges red and white oaks become more prevalent, mixed with shortleaf and Virginia pines and other hardwoods. Beneath the forest canopy lie rhododendron, wild azalea, and mountain laurel. The Cumberland Mountains, tower beside the plateau, reaching an elevation of 4,145 feet above sea level at their highest point, Fort Knob. The Cumberland mountains, on the eastern side of the plateau by the intersection of Tennessee, Kentucky and Virginia, are covered by mixed mesophytic forests among other forest types.

Current Forest Health Challenges

Before 1900, 40-50% of the trees in of many southeastern forests were American Chestnuts. The Cumberland Plateau is in the heart of the Chestnut tree’s historic range. Chestnut blight cankers were first reported in the United States in 1904 in New York City. By 1926, the fungus (Cryphonectria parasitica) had expanded to the full range of the American chestnut, effectively eliminating it from American forests, including the Plateau. The blight fungus enters through wounds, grows in and under the bark, and eventually kills live wood all the way around the twig, branch, or trunk. Although the loss will take generations to reverse, two efforts show promise for the restoration of chestnut trees in Appalachian forests.  American and Chinese chestnuts (which is resistant to the blight) have been hybridized to develop trees that retain characteristics of American chestnut with blight resistance.  A second approach is the use of an imported parasite, a hypovirulent (less lethal) version of the blight fungus, which competes with the blight fungus and controls the disease.  Inoculation of infected trees with this hypovirulent fungus has resulted in healing of previously infected bark tissue.  Research on chestnut restoration is ongoing.  Through these efforts, chestnut trees may again become a significant species in Plateau forests.  In March of 2009, 100 blight American chestnut seedlings were planted in the North Cumberland Wildlife Management Area.  Visit the American Chestnut Foundation for the latest information about chestnut reintroduction efforts.

Another pest that threatens Cumberland Plateau forests is the Hemlock Woolly Adelgid (HWA; Adeleges tsugae).  Eastern hemlock form stands of dense shade in riparian forests (areas along streams and rivers), providing unique habitat for rare mammals, birds, fish, and aquatic species. Native to Japan, the HWA was first found in the US in the 1920s in the Pacific Northwest, and found its way into eastern forests in the 1950s. The adelgid is a small insect that extracts sap from the base of hemlock needles, causing them to fall from the branch, starving the tree over time.  Within a few years of contact with the HWA, an affected hemlock can be completely destroyed. HWAs reproduce asexually, and eggs from a single individual can produce up to 90,000 new adelgids per year.

Three methods are recommended by resource managers to counter adelgid infestations: pesticide injections, insecticidal soaps, and biological control. The most successful biological control has been the release of the LN Beetle (Laricobuius nigrinus) and the Pt Beetle (Pseudoscymnus tsugae). Each beetle feeds exclusively on hemlock woolly adelgids. Most recently, a native fungus that infects the HWA is being studied as a control of the adelgid in the Cumberland Mountains. The Tennessee Division of Forestry, Tennessee Wildlife Resources Agency, Tennessee State Parks, agencies from neighboring states, and partners in the scientific community are conducting research to enhance the effectiveness of these biological control methods. The hope is to treat hemlock stands on state land to ward off expansion of woolly adelgid infestation and help save hemlocks from the fate of the chestnut.