The Mixed Mesophytic Forest ecoregion represents one of the most biologically diverse temperate regions of the world. Forest communities often support more than 30 canopy tree species at a single site, and rich understories of ferns, fungi, perennial and annual herbaceous plants, shrubs, small trees, and diverse animal communities. Songbirds, salamanders, land snails, and beetles are examples of some particularly diverse taxa. Indeed, the ecoregion harbors some of the richest and most endemic land snail, amphibian, and herbaceous plant biotas in the U.S. and Canada. The ecoregion’s freshwater communities are the richest temperate freshwater ecosystems in the world, with globally high richness and endemism in mussels, fish, crayfish, and other invertebrates.
The Lower elevation forests contain a variety of forest types with magnolias (Magnolia spp.), oaks (Quercus spp.), hickories (Carya spp.), walnuts (Juglans spp.), elms (Ulmus spp.), birches (Betula spp.), ashes (Fraxinus spp.), basswoods (Tilia spp.), maples (Acer spp.), locusts (Robinia spp.), and pines (Pinus spp.). The grand tulip poplar (Liriodendron tulipifera), blackgum (Nyssa sylvatica), eastern hemlock (Tsuga canadensis), black cherry (Prunus serotina), sweetgum (Liquidambar styraciflua), American beech (Fagus grandifolia), and yellow buckeye (Aesculus octandra). The American chestnut (Castanea dentata) was a dominant canopy species, but was extirpated at the turn of the century by the introduced chestnut blight fungus (Cryphonectria parasitica). Some endemic species include the Allegheny plum (Prunus alleghaniensis) and the Black mountain salamander (Desmognathus welten).
Higher elevation forests towards the east have yellow birch, mountain maple, sugar maple, beech, and eastern hemlock with extensive understories of mountain laurel (Kalmia latifolia) and rhododendron (Rhododendron spp.). A variety of restricted habitats occur within the forests including glades, heath barrens, shale barrens, and spaghnum bogs. Many of these communities support endemic plants and land snails. Cranberry bogs harbor a range of species that are normally associated with more northerly ecoregions such as cranberry (Vaccinium spp.), blueberry (Vaccinium spp.), bog rosemary (Andromeda glaucophylla), buckbean (Menyanthes trifoliata), northern goshawk (Accipiter gentilis), fisher (Martes pennanti), and black-billed magpie (Pica pica). Such bogs and glades are relicts that have survived with their disjunct populations of cool-adapted species since cooler glacial epochs. Surrounding high elevation forests also support disjunct northern species such as the Canada yew (Taxus canadensis), eastern larch (Larix laricina), red pine (Pinus resinosa), and balsam fir (Abies balsamea).
Over 95 percent of this habitat, perhaps more, has been converted or degraded at some point in the last 200 years. Only a few very small and scattered fragments of undisturbed or old-growth forests still remain, most less than a few hectares in size (Davis 1993). Forests were converted for agriculture, coal mining, logging for charcoal, dams, and road building. Most of the agricultural lands have subsequently failed and are being abandoned, with an increase in the growth of secondary, or pioneer, forests. These regrowing forests lack many of the features and much of the diversity of undisturbed, or old-growth forests, namely large trees, variable age classes of trees, structural complexity such as multiple canopy layers, and diverse and abundant wildflowers, salamanders, fungi, land snails, and other invertebrate taxa. Because of the intensity and broad extent of clearing of forests over the last two centuries, many forest-specialist species appear to have been extirpated over large portions of the landscape. If source populations in undisturbed forest fragments are not imbedded in or adjacent to regrowing tracts, large areas of secondary forests may remain depauperate into the future.
Secondary forests have the capacity to conserve a great deal of biodiversity and represent, in combination with the last fragments of undisturbed forest, the best opportunity to conserve the region’s biodiversity over the long-term. Larger, unroaded blocks of forest can also act as source pools for breeding migratory songbirds that are experiencing negative reproductive rates due to cowbird parasitism and nest predation by meso-predators in the mosaic of smaller forest fragments across the landscape. Trees within secondary forests are beginning to attain sizes that are attractive to logging interests. A landscape-scale conservation strategy for conserving large, interconnected blocks of mature forests urgently needs to be developed and implemented.
Remaining Blocks of Intact Habitat
Few remaining patches of undisturbed forest remain, although older pioneer forests (i.e., forests that have regrown from previously cleared land) can be relatively large. The larger habitat blocks that do exist are found primarily on public lands. Some of the larger extant blocks of relatively intact habitat can be found within the following areas:
•Daniel Boone National Forest - east-central and southeastern Kentucky
•Shawnee State Forest - southern Ohio
•Wayne National Forest - southern Ohio
•Big South Fork National Recreational Area - north-central Tennessee
•Savage Gulf State Natural Area - south-central Tennessee (Grundy County)
•Cranberry Wilderness - southeastern West Virginia
•Monongahela National Forest - eastern West Virginia
•Frozen Head State Natural Area - east-central Tennessee
•Cumberland Gap - southeastern Kentucky
•Pine Mountain - southeastern Kentucky (Letcher County)
•Blanton Forest - southeastern Kentucky (Harlan County)
•Sipsey Wilderness - north-central Alabama
•Talladega National Forest - east-central Alabama
•Scott State Forest - northeastern Tennessee
Degree of Fragmentation
Much of the existing forest, whether old growth or regrowth forests, is still distributed in a highly fragmented mosaic throughout the region, broken by agriculture, roads, power lines, towns, and other forms of development. However, when one considers regrowth forests, the Appalachian Mixed Mesophytic Forests ecoregion has lower levels of fragmentation relative to other East Coast ecoregions. Fragmentation is highest in the northern part of the ecoregion, primarily in southwestern Pennsylvania and Ohio. The southern section of the ecoregion is comparatively less fragmented and has better potential for restoration into larger blocks within the context of a conservation strategy.
Degree of Protection
Most larger blocks of forest presently occur in federal and state forests, wilderness areas, and state natural areas. However, the management plans for federal forest lands do not strictly protect the forests, but reflect the multi-use management policy of the Forest Service. Present federal and state policies dictate intensive harvest of timber from National Forests, usually accompanied by road building, fire suppression, thinning, application of herbicides and pesticides, and other ecologically-damaging management practices. No effective formal process of identifying and protecting rare, distinctive, representative, or otherwise important communities, species, or ecosystems has been developed by federal or state agencies. Some small, but highly distinctive or rare communities, such as bogs and glades, have been protected by private organizations such as The Nature Conservancy. Several landscape-level conservation systems have been proposed for this ecoregion and the adjacent Appalachian ecoregion, consisting of a network of core protected areas, corridors and linkage zones, and buffer zones (Mueller 1992, Leverett 1993).
Types and Severity of Threats
A primary threat is the increasing conversion and fragmentation of forests through logging and development. Hardwood forests are increasingly being exploited throughout the region as maturing forests become attractive to timber exploiters and production in West Coast forests declines. Both multinational timber industries as well as local chip mills in Kentucky and Tennessee create demand for increased harvests on public and private lands.
Coal, copper, and ore mining in this ecoregion are a major cause of air and water pollution, causing widespread degradation and poisoning of ecosystems. The globally outstanding freshwater biodiversity of the ecoregion is highly imperiled from toxic pollution, acid runoff from mines, pesticides and herbicides, sedimentation, eutrophication from excess nutrient runoff, dams, dredging, channelization, and introduced species such as the zebra mussel. Acid rain deposition, from industrial and urban sources, continues to be a major problem in many sensitive ecosystems, particularly in higher elevation forest communities.
Highways continue to cause high mortality in wildlife and are barriers to dispersal for many species. Numerous proposed highways, roads, and power lines cut across many of the larger blocks of forest in the ecoregion, particularly in the Monongahela National Forest (e.g., "Corridor H", transmission lines in the proposed Cherry River Wilderness). Road building into larger blocks of forests should be curtailed to reduce fragmentation and loss of source pool breeding sites for migratory songbirds. Off-road vehicle use and road building has severely degraded riparian communities and rare bogs and glades in many areas.
Abundant populations of deer, resulting from the eradication of large predators and poorly-managed hunting programs, have been implicated in the extirpation and reduction of many understory plant species and the alteration of community structure (Alverson et al. 1988). The nearly extirpated Canada yew (Taxus canadensis) of Monogahela National Forest is a classic example of this problem, although not even recognized by the agency as a sensitive species (Mueller 1992).
Many wild herbs and other plants are harvested for commercial purposes, and some, like wild ginseng, are threatened with extirpation over large areas of their range because of unregulated and illegal poaching. Large numbers of black bears are poached for their gall bladders for the Asian medicinal trade. Freshwater mussels are legally and illegally harvested for their shells to be used as nuclei for cultured pearls in Asia. A number of endangered species, including many plants and freshwater mussels and fish, occur within the ecoregion.
Suite of Priority Activities to Enhance Biodiversity Conservation
•Identification and protection of large core areas of forest, linkage zones, and buffer zones, building upon existing protected sites. Examples include the proposed Cherry River Wilderness, Cranberry Wilderness expansion, Cheat Bridge corridor, Canaan Mountain Wilderness, Laurel Fork Wilderness, Kentucky River corridor, Cumberland River corridor, and the Gauley Mountain Wilderness (Mueller 1992, Leverett 1993).
•Identification, restoration, and protection of large blocks of unfragmented forest habitat that can act as source pools for breeding migratory songbirds. Populations that breed in landscapes with only small, fragmented forest patches generally have negative reproductive rates because of cowbird parasitism and predation by raccoons, crows, opossums, and other meso-predators. Recent studies suggest that the few remaining very large blocks of forest are maintaining populations of songbirds over vast regions. Protection and expansion of existing large blocks and restoration of additional blocks distributed across the landscape is a top priority conservation activity. Conserving migratory songbirds will only occur if state and federal agencies can be persuaded to stop building roads and power line corridors and to begin to close existing roads to restore large contiguous blocks of forest. Plans to conserve larger blocks of forest for songbird conservation need to be implemented immediately before logging interests obtain concessions throughout the regions as regrowing forests becomes more lucrative.
•Implementation of plans to increase the connectivity of public and conserved private lands, particularly in Wayne State Forest and the Cumberland Plateau of Tennessee.
•Reduction and control of acid precipitation, gypsy moths, woolly adelgids, and zebra mussels.
•Control of poaching of black bears and other wildlife, and commercially harvested herbs.
•Reevaluation of fire suppression and management practices in light of maintaining native communities.
•Increase in heritage inventories of the ecoregion to identify additional areas and species populations in need of protection and conservation action.
•Development of hunting management plans that would prevent over-abundant deer populations from causing irreversible ecological damage. Reintroduction of cougars and gray wolves, and better management of existing populations of black bear and mustellids, would help reestablish ecological interactions that were sustainable and less damaging to the ecosystem than existing conditions.
•Alabama Natural Heritage Program
•Alabama Wilderness Association
•Cumberland Gap Friends of the Bankhead
•Georgia Natural Heritage Program
•Kentucky Natural Heritage Program
•The Nature Conservancy
•The Nature Conservancy - Southeast Regional Office
•The Nature Conservancy of Alabama
•The Nature Conservancy of Georgia
•The Nature Conservancy of Kentucky
•The Nature Conservancy of Ohio
•The Nature Conservancy of Pennsylvania
•The Nature Conservancy of Tennessee
•The Nature Conservancy of West Virginia
•Ohio Natural Heritage Data Base
•Tennessee Division of Natural Heritage US Fish and Wildlife Service
•USDA Forest Service
•West Virginia Highlands Conservancy
•West VirginiaNatural Heritage Program
•Western Pennsylvania Conservancy
Relationship to other classification schemes
The Mixed Mesophytic Forests ecoregion was based on an aggregation of several of Omernik's level III ecoregions. Due to similarities in biodiversity characteristics and dynamics, Omernik's ecoregions that were combined into our Mixed Mesophytic Forests ecoregion were Western Allegheny Plateau (70), Central Appalachians (69), Southwestern Appalachians (68), and the extreme southwest portion of the Interior Plateau (71) that lies within Alabama. In relation to Küchler's ecoregions, it covers a majority of the Mixed Mesophytic Forest as well as portions of the Oak-Hickory-Pine ecoregion in the south and the Appalachian Oak forest in southwestern Pennsylvania. This ecoregion roughly corresponds to Bailey's Southern Unglaciated Allegheny Plateau section (221E), Northern Cumberland Plateau section (221H), Southern Cumberland Plateau section (231C), and portions of the Southern Ridge and Valley section (231D).
Prepared by: C. Loucks, D. Olson, E. Dinerstein, A. Weakley, R. Noss, J. Stritholt, K. Wolfe.