Appalachian mixed mesophytic forests


The Appalachian mixed mesophytic forests is an ecoregion of the temperate broadleaf and mixed forests biome, as defined by the World Wildlife Fund. It consists of mesophytic plants west of the Appalachian Mountains in the Southeastern United States.
This ecoregion consists of the following EPA level III ecoregions:

Setting

This ecoregion is located in the plains and hill country west of the Appalachians in northwest Alabama and east central Tennessee, eastern Kentucky, western North Carolina and Virginia, most of West Virginia, western Maryland, southeastern Ohio and western Pennsylvania. This ecoregion also occurs in scattered disjuncts in the Ozark and Ouachita Mountains of Arkansas, Missouri, and extreme eastern Oklahoma. These forests are known for their rich diversity of plants and animals, which is due to several contributing factors, especially that the area was an unglaciated refugium for many species. It shares species with the high elevation Appalachian-Blue Ridge forests to the east, the hardwood forests to the west, and the mixed hardwood/conifer forests to the south.

Climate

The climate of the Appalachian mixed mesophytic forests varies from humid continental in the northern part of its range with warm to hot, humid summers and cold, snowy winters to humid subtropical in the southern part of its range with summers having long periods of hot, humid conditions with generally mild winters. The forests receive abundant annual precipitation, ranging from 35 to 80 inches, distributed relatively evenly throughout the year.

Flora

They are one of the most biologically diverse temperate forest regions on earth. It has an unusually diverse tree flora, with as many as 30 tree species at a single site including many relics of the ancient forest that once covered North America more widely. Along with the forest there is a rich undergrowth of ferns, fungi, herbaceous plants, shrubs and small trees as well as areas of glade, heath, shale, peat bog and cranberry bog.

Mesophytic forests

Mesophytic forests occur in humid and sheltered coves, hollows, lower slopes, areas near small streams, and river valleys along the Allegheny and Cumberland plateaus. The herb layer is very rich and often has abundant spring ephemerals. In undisturbed areas, the canopy trees can grow very large. Typical trees include sugar maple, beech, tuliptree, basswood, northern red oak, American sycamore, cucumber-tree, bitternut hickory, pawpaw and black walnut. White oak and sprouts of American chestnut are common on slightly drier benches. Other trees typically include eastern hemlock, white ash, sweetgum, black tupelo, sweet birch, river birch, and yellow buckeye.

Dry calcareous forests

The southern Ridge and Valley/Cumberland dry calcareous forests occur on dry to dry-mesic calcareous habitats on low escarpments of the Cumberland Plateau. They are often found on deep soils in a variety landscapes within their range. Trees are mainly oaks and hickories, with other species less abundant. Oaks include white oak, northern red oak, post oak, chinkapin oak, and Shumard oak. Hickories include shagbark hickory. Other trees can be sugar maple, eastern red-cedar, or pines.

Appalachian cove forests

Appalachian cove forests are found in sheltered concave slopes with a moist environment. Characteristic tree include yellow buckeye, sugar maple, white ash, basswood, tuliptree, Carolina silverbell, eastern hemlock, beech, cucumber tree, and Fraser magnolia.

Dry-mesic oak forests

Dry-mesic oak forests cover large areas at lower and middle elevations on flat to gently rolling terrain. Mature stands have a variety of oak and hickory species adapted to dry-mesic conditions. Oaks include northern red oak, white oak, black oak, and scarlet oak ; hickories include mockernut hickory, shagbark hickory, red hickory, and pignut hickory. In addition, red maple, sweet birch, and yellow birch are common; sugar maple is occasional. In areas that have been recently disturbed, white pine, Virginia pine, black locust, or tulip tree can be abundant. Areas of impeded drainage sometimes harbor small wetlands, including non-forested seeps or forested wetlands with red maple, swamp white oak, or black tupelo. Sprouts of American chestnut are common in these forests.

Dry oak forests and woodlands

The Allegheny-Cumberland dry oak forest and woodland forest system is found on acidic soils on the Allegheny and Cumberland plateaus, and ridges in the southern Ridge and Valley. The forests are typically dominated by white oak, southern red oak, northern red oak, chestnut oak, scarlet oak, with lesser amounts of red maple, pignut hickory, and mockernut hickory. A few shortleaf pines or Virginia pines may occur, particularly adjacent to escarpments or following fire. Sprouts of American chestnut can often be found where it was formerly a common tree.

Low-elevation pine forests

Southern Appalachian low-elevation pine forests occur on a variety of topographic and landscape positions, including ridgetops, upper- and mid-slopes, and in lower elevations such as mountain valleys. These forests dominated by shortleaf pine and Virginia pine. Pitch pine may sometimes be present. Hardwoods are sometimes abundant, especially dry-site oaks such as southern red oak, chestnut oak, and scarlet oak, but also pignut hickory, red maple, and others. The shrub layer may be well-developed, with hillside blueberry, black huckleberry, or other acid-tolerant species most characteristic. Herbs are usually sparse but may include narrowleaf silkgrass and Goat-rue.

Montane oak forests

Montane oak forests occur on exposed ridges and on south- to west-facing slopes at middle elevations. Soils are thin and nutrient-poor and trees are often stunted and wind-flagged. Northern red oak and white oak are common, as are sprouts of American chestnut. Winterberry, flame azalea, catawba rhododendron, and great rhododendron are common shrubs.

Hemlock-northern hardwood forests

Hemlock-northern hardwood forests are found at higher elevations. They include yellow birch, mountain maple, sugar maple, beech, and eastern hemlock. Mountain laurel and rhododendron are found in the understory.

Spruce-fir forests

Spruce-fir forests occur at the highest elevations, above. Their environment is cool and wet, with frequent fog and precipitation. Red spruce and Fraser fir dominate the forest canopy.

Bogs

Cranberry bogs harbor species typical of ecoregions found to the north. These species include cranberry and blueberry, bog rosemary, and buckbean. These bogs are relicts that have survived since the last glacial period.

Other habitats

More unique, restricted habitats within these forests include glades, heath barrens, shale barrens, and sphagnum bogs. These often support endemic plants and land snails.

Prehistoric period

During the Last Glacial Maximum about 18,000 years ago, the influence of Arctic air masses and boreal vegetation extended to about 33° N. latitude, the approximate latitude of Birmingham and Atlanta. Forests of the glacial period were dominated by various spruces and jack pine; fir was abundant in some locations. With the exception of the absence of certain prairie elements, the understories of these forests were generally typical of modern spruce-fir forests within and near Canada. Temperate deciduous forests dominated from about 33° to 30° N. latitude, including most of the glacial Gulf Coast from about 84° W. longitude. Regional climate was similar to or slightly drier than modern conditions. Oak, hickory, chestnut, and southern pine species were abundant. Walnuts, beech, sweetgum, alder, birch, tulip poplar, elms, hornbeams, basswoods, and others that are generally common in modern southern deciduous forests were also common then. Grasses, sedges, and sunflowers were also common.

Fauna

The woodlands of the area are rich in wildlife. In particular they are important habitat for migrating birds including wood warblers, vireos, and thrushes. The rivers of the ecoregion have the highest species richness of any freshwater ecosystem. In particular, there are a large number of endemic fish and shellfish species.

Threats

This ecoregion is considered critically endangered with 95% of the habitat degraded or converted to commercial forest. Large areas have been destroyed and fragmented through surface mining, including mountaintop removal. Large areas have also been logged and then converted to plantations of fast-growing tree species, such as Loblolly Pine which are then used to produce wood pulp, which is particularly a problem in the Cumberland Plateau of Tennessee. Another threat to habitats come from growing numbers of deer. Major rivers in the ecoregion, such as the Tennessee River, have been dammed. This has resulted in the threatened or endangered status of many species of native fish, amphibians, and shellfish.

Natural areas

The remaining forest is mostly found in protected areas.