Appalachian–Blue Ridge forests


The Appalachian–Blue Ridge forests are an ecoregion in the Temperate broadleaf and mixed forests Biome, in the Eastern United States. The ecoregion is located in the central and southern Appalachian Mountains, including the Ridge-and-Valley Appalachians and the Blue Ridge Mountains. It covers an area of about in: northeast Alabama and Georgia, northwest South Carolina, eastern Tennessee, western North Carolina, Virginia, Maryland, and central West Virginia and Pennsylvania; and small extensions into Kentucky, New Jersey, and New York.
They are one of the world's richest temperate deciduous forests in terms of biodiversity; there are an unusually high number of species of both flora and fauna, as well as a high number of endemic species. The reasons for this are the long-term geologic stability of the region, its long ridges and valleys which serve both as barrier and corridors, and their general north-south alignment which allowed habitats to shift southward during ice ages. The mountains also contain a large variety of diverse landscapes, microclimates and soils all constituting microhabitats allowing many refugia areas and relict species to survive and thrive.

Climate

The climate varies from humid continental in the north to humid subtropical in the south. Summers are hot at lower elevations, warm at higher elevations. Winters are cold at higher elevations and cool at lower elevations.

Flora

In terms of biodiversity, the only comparable temperate deciduous forest regions in the world are in central China, Japan and in the Caucasus Mountains. Both the Appalachians and central China contain relict habitats of an ancient forest that was once widespread over the Northern Hemisphere. There are species, genera, and families of plants that occur only in these two locations. The Great Smoky Mountains are particularly rich in biodiversity.
The Appalachians are home to 158 different species of tree, more than anywhere else in North America. There are two main types of forest; deciduous oak forest at low elevations, and coniferous spruce-fir forest above that. Until the 1930s the oaks were mixed with American chestnut but these were largely wiped out by the chestnut blight fungus in the early 1900s.

Cove forests

occur in coves and on low north- and east-facing slopes in the southern Blue Ridge and central Appalachian Mountains. They are among the most biologically diverse ecosystems in the country. Typical trees of these forests are sugar maple, American beech, eastern hemlock, Carolina silverbell, tulip poplar, red maple, white oak, northern red oak, yellow birch, yellow buckeye, and basswood. Oaks gain numbers on drier sites.

Low-elevation pine forests

s 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 are 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.

Oak forests

Southern Appalachian oak forests, widespread in the southeastern United States, occur on dry, upland sites on southern and western aspects and ridgetops. The composition of these forests varies throughout their range but often includes chestnut oak, northern red oak, eastern black oak, white oak,, and scarlet oak. Hickories such as bitternut, shagbark, and mockernut, are found here, as are black tupelo, red maple, white pine, and white ash.

Dry calcareous forests

The Southern Ridge and Valley/Cumberland dry calcareous forests occur on dry to dry–mesic calcareous habitats in the southern Ridge-and-Valley Appalachians. 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.

Dry oak forests and woodlands

The Allegheny-Cumberland dry oak forest and woodland forest system is found on ridges in the southern Ridge and Valley. The forests are typically dominated by white oak, southern 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 chestnut can often be found where it was formerly a common tree.
, North Carolina.

Dry oak–pine forests

s occur on dry sites with loamy to sandy soils. A mix of oak and pine tree species dominate the canopy, typically chestnut oak, Virginia pine, and white pine, but sometimes white oak or scarlet oak. Varying amounts of oaks and pines can result in oak forests, mixed oak–pine forests, or small pine forests. Flowering dogwood, sourwood, sassafras, and blackgum live in the midstory and hillside blueberry, black huckleberry, and mountain laurel are common in the understory, where they can form a dense layer.

Dry–mesic oak forests

s cover large areas at low and middle elevations, typically on flat to gently rolling terrain. Red oak, white oak, and black oak are common oaks in this habitat. Other trees include hickories, red maple, sugar maple, white ash, tulip tree, American beech, black cherry, black birch, black tupelo, and American elm. Flowering dogwood is a common understory tree.

Pine-oak rocky woodland

s occur on lower-elevation hilltops, outcrops, and rocky slopes and have a patchy or open aspect. Pitch pine and Virginia pine are common within their respective ranges. These pines are often mixed with dry-site oaks such as chestnut oak, bear oak, northern red oak, and scarlet oak. Sprouts of chestnut can also be found. In the northeast, eastern red-cedar or hophornbeam are sometimes important. In the understory, some areas have a fairly well-developed heath shrub layer, others a graminoid layer, the latter particularly common under deciduous trees such as oaks.

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.

Montane pine forests and woodlands

These forests and woodlands are found on exposed ridges, clifftops, and south- and west-facing slopes. They occur at elevations between on often rocky ground. The underlying rock is acidic and sedimentary or metasedimentary. The soil is shallow, arid, and infertile. Dead wood, ericaceous shrubs, and a thick layer of poorly decomposed plant litter make this habitat very fire-prone. Most examples are dominated by table mountain pine, often with pitch pine or Virginia pine, and occasionally with Carolina hemlock and chestnut oak. This habitat takes the form of patchy to open woodlands, although closed-canopy may also be found.

Northern hardwood forests

s occur in cool, mesic habitats found above on north- and east-facing slopes of the southern Appalachians. Oak forests are often found nearby, either at lower elevations or in more exposed areas. Sugar maple, beech, yellow birch, and yellow buckeye dominate but are sometimes joined by the conifers eastern hemlock, eastern white pine, and red spruce. Black cherry and white basswood are occasionally abundant. Red oak may be present but is not dominant. Areas where beech is dominant are known as beech gaps.

Hemlock–northern hardwood forests

are found in deep coves, moist flats, and ravines from Virginia and West Virginia northward. They include yellow birch, mountain maple, sugar maple, and beech. These trees are sometimes joined by hemlock or white pine.

Spruce-fir forests

Uncommon but significant are montane and allied spruce and southern Appalachian spruce-fir forests. These occur only on the highest peaks and ridges, where the soils are poor, the growing season short, and moisture comes from rain, snow, and fog. Red spruce, Fraser fir, yellow birch, mountain ash, and mountain maple identify these forests, while hobblebush and bearberry occur in the understory.

Balds

are areas covered by native grasses or dense shrubs that occur only on some high-elevation summits and slopes.

Bogs

are boreal ecosystems, which occur in many places in the Appalachians, particularly the Allegheny and Blue Ridge subranges. Though popularly called bogs, many of them are technically fens.

Sods

is a term used in the Allegheny Mountains of eastern West Virginia for a mountaintop meadow or bog, in an area that is otherwise generally forested. The term is similar to that of an Appalachian bald.

Fauna

Endangered or threatened species of the Appalachians include some snails and salamanders, the red-shouldered hawk, loggerhead shrike, Virginia big-eared bat, the red wolf and the spruce-fir moss spider. The limestone caves of the Appalachians are important habitat for bats, invertebrates, fish and salamanders including 34 species of lungless salamander, more than anywhere else on earth.

Threats

The forests have been altered by logging and clearance for agriculture, urban and industrial development with only small patches of original forest remaining, the largest of which is in the Great Smoky Mountains; nearly all of Shenandoah National Park, for example, is regrown forest but still vital habitat for wildlife. The spruce and fir forests of the highlands have been logged particularly intensively and in many cases have not regenerated leaving areas of Appalachian balds heath. Also, as large predators such as wolves and cougars have been removed, the forests are now being overgrazed by deer. Plants and animals are also threatened by introduced species including the gypsy moth, spruce budworm, hemlock woolly adelgid, balsam woolly adelgid and the Discula destructiva that affects dogwoods and is similar to chestnut blight.

Areas of intact habitat

Areas of intact forest, mostly in public ownership, include: