[pp.15-20 in Terwilliger, K. and Tate, Jr. 1995. A Guide to Endangered and Threatened Species in Virginia (Blacksburg: The McDonald & Woodward Publishing Company). Copyright 1994: Virginia Department of Game and Inland Fisheries.]
A temperate broadleaf deciduous forest covers most of Virginia, reflecting its humid subtropical climate. Various types of this forest may be found from northern New England to southern Florida, from the Mississippi River to the Atlantic Ocean. In Virginia, the forest is generally characterized by four layers, each rich in species. The canopy, dominated by mast-producing oaks and hickories, is 60 to 100 feet above the forest floor. Below it lies an understory of smaller trees such as dogwood and redbud; a shrub layer frequently dominated by heaths such as rhododendron, azalea, and mountain laurel; and an herb layer of diverse perennial forbs, mosses, lichens, and clubmosses. Woody vines are conspicuous in moister habitats; most common are wild grape, Virginia creeper, and poison ivy.
Virginia's broadleaf deciduous forest may be differentiated into four basic types: mixed mesophytic, oak-chestnut, oak-pine, and southeastern evergreen forests. Most diverse is the mixed mesophytic forest found in the Appalachian Plateaus Province. Although the member tree species tend to segregate into a mosaic of stands, more than 20 species are considered to share dominance in this forest type. The species include American beech, sugar maple, eastern hemlock, red oak, white basswood, tulip tree, yellow buckeye, and various hickories, ashes, and magnolias. Outliers of this forest type, known as cove forests, occur in cool, damp, deep valleys in the Allegheny Mountains and Blue Ridge.
The most widespread forest type in Virginia is the oak-chestnut forest, which covers most of the Ridge and Valley, Blue Ridge, and northern Piedmont Plateau provinces. Three oak species are most frequent: white oak, chestnut oak, and red oak. Hickories are also important components. The American chestnut, once the largest and perhaps most important tree in the forest, has been extinct as a canopy species since the 1930s.
In the Blue Ridge and the Ridge and Valley, the oak-chestnut forest varies with increasing elevation. A subtle altitudinal zonation can be discerned between 4000 and 4500 feet asl as oaks and hickories yield dominance to American beech, sugar maple, and yellow birch, northern hardwoods more typical in the northeastern US. Above 4500 feet, most notably on Beartown Mountain (Russell County), Whitetop, and Mount Rogers, the broadleaf forest gives way entirely to a needleleaf evergreen forest. In this uppermost (boreal or Canadian) zone, red spruce usually dominates, but on Mount Rogers a southern Appalachian endemic, Fraser fir, covers the summit.
On the southern Piedmont and the peninsulas of the Coastal Plain, pines become more abundant and black oak replaces red oak as the principal co-dominant with white oak in the region's oak-pine forest. Virginia pine and shortleaf pine are common. On the Coastal Plain and the eastern edge of the Piedmont, these two short-needled pines are joined by the long-needled loblolly pine. Pines occur primarily as members of early successional communities on abandoned farmland, but on dry sites and on soils with low nutrient content—such as those exhausted from poor agricultural practices, pines may persist.
The southeastern evergreen forest occurs on the Coastal Plain south of the James and is the northernmost extension of a vegetation type in which long-needled pines dominate. This forest stretches southward and westward from Virginia to eastern Texas. Longleaf pine is characteristic but generally confined to sandy uplands, where it is maintained by low nutrient, well drained sandy soils and periodic fire. Where drainage is poor, loblolly pine and pond pine join longleaf pine in a savanna with an herb layer of grasses, sedges, and flowering forbs. On heavier, alluvial soils along rivers and in Great Dismal Swamp, a swamp forest characterized by bald cypress and dominated by tupelo, red maple, and black gum occurs. At maritime sites such as Seashore State Park, cypress may be accompanied by live oaks heavily festooned with Spanish moss.
Within Virginia, there are several unique, localized communities more strongly influenced by local microclimates and substrate than by the regional climate. Most often it is in such habitats that Virginia's rarest and most vulnerable plant and animal species are found.
The cooler temperatures and higher humidities of high elevations permit mountain summits to serve as refuges for species which had much broader distributions in Virginia during the Pleistocene, species with boreal and even arctic affinities. Two high elevation habitats, boreal forests and bogs, are particularly significant in harboring northern species.
The boreal forest is exemplified by the red spruce-Fraser fir forest atop Mount Rogers. Fraser fir occurs in no other boreal stands in Virginia (although it is widely planted for Christmas trees). Elsewhere at high elevations red spruce is the dominant. In the spruce forests there is often a dense understory of rhododendrons. Within some communities may be found the endangered snowshoe hare and northern flying squirrel.
Bogs are cool, acidic, and extremely small wetlands that occur in areas of impeded drainage at high elevations. They have microenvironments similar to the true bog or muskeg found farther north in glaciated parts of North America. Virginia's bogs occur primarily in the New River drainage section of the Blue Ridge and on Massanutten, Clinch, and Salt Pond mountains in the Ridge and Valley. Sphagnum moss is characteristic of these wetlands. Rushes, sedges, grasses, and various forbs and subshrubs make up the rest of the community. Virginia's bogs, unlike true muskeg, contain not only species of northern affinities but also species of southern affinity and some disjunct coastal species. The endangered bog turtle may be found in some bogs of the southern Blue Ridge.
Virginia has only two natural lakes, Mountain Lake in Giles County and Lake Drummond in the Great Dismal Swamp. Neither is inhabited by listed species. However, Virginia's streams, pools, ponds, and swamps provide critical habitat for a host of rare species, among them plants, mollusks, arthropods, fishes, amphibians, and even a few mammals.
Any drainage system includes diverse microenvironments ranging from fast, cool upland headwaters to slower, deeper lowland stretches near the mouth. Differing substrates over which waters flow further contribute to the diversity of microhabitats.
Freshwater swamps are habitats where woody vegetation grows in standing water for all or much of the year. Swamps may be found in all the physiographic provinces, and each one is a critical habitat. The largest swamp in Virginia is the Great Dismal Swamp, which spreads over some 750 square miles atop impermeable clays on the Coastal Plain of southeastern Virginia and northeastern North Carolina. It is critical habitat for several vulnerable mammals, including the threatened Dismal Swamp subspecies of southeastern shrew.
Another significant but restricted freshwater habitat is the evergreen shrub bog or pocosin. Pocosins occur on sandy or peaty soils on flat, poorly drained ridges. Pond pine dominates an open-canopy tree layer that rises above a dense shrub layer of swamp magnolia, loblolly bay, holly, and red bay. Many of the shrubs are flammable and fire helps maintain the pocosin. The endangered canebrake rattlesnake occurs in this habitat.
A unique ephemeral freshwater habitat occurs in sinkhole ponds in karstic areas of several counties in the upper Shenandoah Valley. Sinkhole ponds here lie above the limestones which have dissolved away at depth to form the pits that the ponds fill. The pond margins are actually an acidic environment supporting wetlands conducive to the survival of both northern and coastal plant species. Among listed species, northeastern bulrush and Virginia sneezeweed are members of the unique community of plants that grow in this habitat. Swamp pink occurs near some of them.
In the Ridge and Valley Province, the nature of the substrate can have profound influence on the plant and animal communities developed on or within it. Particularly significant are carbonate bedrock and south-facing shale outcrops.
The dissolution of carbonate rocks has created more than 2300 natural caves in Virginia. Many are home to a specialized and extremely localized fauna. Aquatic invertebrates, especially amphipods and isopods, have adapted to the cave environments, and several species of bats utilize caves for hibernacula and nurseries.
Steeply sloping (20 or more) shale outcrops, particularly when undercut by a stream, produce a very unstable surface of thin flakes of shale. Gravity continually pulls the flakes downslope and prevents the establishment of large trees. South-facing outcrops receive the most intense rays of the summer sun, adding high temperatures and high evaporation rates as limitations to plant growth. Such hot, dry exposures are known as shale barrens and upon them a sparse, shrubby pine-oak community is characteristic. Shale barrens are restricted to the Ridge and Valley Province and extend only from Virginia and West Virginia through Maryland to southeastern Pennsylvania. The few plant species which survive the harsh conditions are frequently endemic to the shale barrens or represent widely disjunct populations of primarily midwestern or southwestern species. The endangered Millboro leatherflower is an example of a shale barren endemic.
Virginia has two coastal regions, the Atlantic Coast proper and the Chesapeake Bay. Where the land meets the Atlantic head on, the actions of waves and wind create dynamic landscapes that can change overnight with the onslaught of a winter storm or a late summer hurricane. The shoreline of the Bay, on the other hand, is shaped primarily by stream action from the great rivers which empty into it.
On the Atlantic Coast, barrier islands provide a broad zone of interface between land and open sea down the length of the Eastern Shore; but along the coast of Virginia Beach, the boundary is abrupt. Sandy beach and dune habitats exist in both locations. In Accomack and Northampton counties on the Eastern Shore, the dynamic but fragile areas of sand are nesting sites critical to the survival of several of Virginia's rarest birds, including piping plover, Wilson's plover, and gull-billed tern. The loggerhead turtle uses the barrier island beaches and those of Virginia Beach for nest sites. And the beaches of Mathews County on the Chesapeake shoreline are home to the state's four populations of the northeastern beach tiger beetle.
Virginia's coastal wetlands grade from saltmarshes secured behind the barrier islands to brackish marshes bordering Chesapeake Bay and edging the estuarine stretches of streams entering the Bay, to upstream freshwater marshes still influenced by the ebb and flow of the tides. Two communities are distinguished within the saltmarsh. High marsh is flooded only irregularly, during the highest tides of the year. Here grow saltmeadow hay, blackneedle rush, and salt grass. Low marsh is flooded daily at high tide and is dominated by saltmarsh cordgrass. Glassworts and sea lavenders also occur in the low marsh.
Considerable quantities of decaying vegetation accumulate in the saltmarsh and support a rich community of detritus-feeding invertebrates and their predators. The low marsh and its tidal streams also provide habitat for larval stages of insects and for mollusks, crustaceans, and fishes and thus are important habitat for a variety of terrestrial animals that come to the marsh to feed.
Tidal freshwater marshes occur along Coastal Plain rivers near the Fall Line; major freshwater marshes also fringe Back Bay and extend up North Landing River. Cattails, chairmaker's rush, Olney's three-square, and big cordgrass are significant members of the plant community. Tidal freshwater marshes in many places lie adjacent to the spawning grounds of estuarine and oceanic fishes such as shad, river herring, striped bass, and the Atlantic sturgeon.
At the edge of the land, below the low tide mark, in shallow brackish waters is a community of rooted grasses rich in marine invertebrates, the seagrass meadow. Eelgrass and associated plants trap nutrients and plankton circulating in the currents and provide food for diverse isopods, amphipods, snails, and sea slugs. The seagrass meadow also provides shelter for young fishes and for molting crabs. Eelgrass is consumed by the endangered Atlantic green and loggerhead sea turtles and by numerous migratory waterfowl which winter in the Chesapeake Bay area. The sea grass meadows are vital not only to Virginia's species but to others which breed or spend much of their adult lives far beyond Virginia's borders.
People first arrived in Virginia no later than 12,000 years ago, when an open spruce and pine forest covered most of the land area. Along with the climatic and vegetational changes associated with the retreat of the continental ice sheets to the north, Paleo-Indians were part of the great environmental revolution which resulted in the extinction or extirpation of Virginia's large Pleistocene mammals: mammoths and mastodons, musk oxen and caribou, ground sloths and horses.
With the demise of the largest game species, a warming climate, and re-establishment of the broadleaf forest, aboriginal populations apparently came to exploit a wider range of natural products from forest, stream and estuary as part of a generalized hunting and gathering economy that persisted throughout Virginia from roughly 9000 to 3000 years ago.
The widespread adoption of agriculture began about 3000 years ago in Virginia. People cultivated maize, beans, and squashes. Agriculture was especially important to the tribes of Virginia's Coastal Plain, where by 1600 AD a relatively dense population lived in more than a hundred villages distributed along the major rivers. These people used fire to clear small plots of forests for croplands and apparently also regularly burned the forests to create meadows attractive to large game such as deer and elk and possibly bison. Fire was used to drive deer during the fall hunt. Repeayed burning had opened the forest to the degree that the seventeenth century accounts by Europeans described woods through which one could easily ride a horse.
It is difficult to measure the true impact of Native Americans of Virginia's ecosystems. Peoples who came across the Atlantic—from Europe and Africa—created a new culture and a new landscape, obliterating the record of Indian environmental change. To the Europeans, Virginia was a vast wilderness to be tamed and civilized—"Europeanized"—and that meant converting forest to farmland. In the process of taming the American landscape, they overharvested game and furbearers, exterminated predators, and cut down forests.
Widespread clearing of the forest marked the progression of European agriculture and people from the Coastal Plain onto the Piedmont during the first two centuries of settlement. Tobacco, which rapidly withdrew nutrients from the topsoil, was grown in a slash-and burn system not unlike that of the Native Americans. While land was abundant and cheap, it was easy to move on when the soils were exhausted and clear new lands, leaving behind an untidy landscape of abandoned fields, frequently invaded by stunted pines.
Animal husbandry practices probably were responsible for modification of the forest. Cattle and hogs roamed the woods, left to forage for themselves. Both livestock species must have altered the amount of cover and relative abundance of plants in the shrub and herb layers.
As the human population grew, lumbering increased. Wood was the primary construction material and fuel. Soap-making, glass-making, tanning, and wool-cleaning all required wood too. Fencing—to keep livestock out of cultivated plots—consumed considerable timber: the movable, self-supporting worm or Virginia fence was typically 6 to 10 rails high.
In the 1700s, attracted by rich soils and cheap land, Scotch-Irish and German-speaking peoples moved southward out of Pennsylvania into the Valley of Virginia and began clearing the forests west of the Blue Ridge for their farms. Early industrial development in the Ridge and Valley also depleted forests; iron furnaces demanded charcoal and tanneries demanded oak and chestnut bark. Only the most inaccessible areas of the Blue Ridge and Alleghenies escaped the axe.
It is safe to say that virtually all of the broadleaf deciduous forest in Virginia today is secondary growth, much of it less than 100 years old. Major periods of farm abandonment occurred in the northern Valley and northern Piedmont during the Civil War and in the southern Piedmont, Blue Ridge, Ridge and Valley and Appalachian Plateaus during the Depression. The few, small areas of boreal forest that remain probably were never cleared; secondary succession in the spruce forest seems to lead to a forest of northern hardwoods in today's environment.
Clearing of forests obviously means outright loss of habitat for the species that inhabit it. However, clearing usually proceeds in a patchwork fashion that first fragments the forest. For many animals, habitat fragmentation means increased expenditure of time and energy in locating food, increased difficulty in finding mates, and perhaps greater vulnerability to predation when passing through cleared lands. For plants, fragmentation may mean an increase in light and evaporation rates, a decrease in pollinators and dispersers, and/or an increase in predation. Any or all of these factors can translate into population decline and increased vulnerability to extirpation.
What may mean decline or extinction for forest species, however, may be a boon to those that require edge or open habitats. White-tail deer, for example, are probably much more numerous in Virginia today than when colonists first arrived (although they first had to be saved from the brink of extinction by reintroductions and enlightened game management practices). Red fox and coyote, both of which prefer open woods, edges, or fields, have moved into Virginia since the Europeanization of the landscape.
Extreme habitat modification accompanies urban development, which frequently destroys natural habitats altogether, replacing them with artificial ones. The new environments are by no means devoid of life, but they generally support neither the same kinds nor the same diversity of species that the former natural habitats did. A distinct fauna and flora develops in towns and cities. Introduced species abound in tended gardens and untended back lots: Japanese honeysuckle, dandelion, pigeon, house sparrow, starling, Norway rat, house mouse. But native species also adapt: blue jay, opossum, raccoon, to name just a few.
Farming, urbanization, and industrialization also have affected aquatic habitats. Our waters are polluted with nutrients and toxins, and siltation rates have increased. The excessive sediments suffocate bottom-dwelling organisms in streams and estuaries.
In the Appalachian Plateaus Province, drainage from coal mines and from coal storage heaps is highly acidic. Water reacts with the sulfur in the coal to produce sulfuric acid which, when it enters drainage systems, acidifies streams beyond the point at which many forms of life can exist. Siltation from eroded hillsides and from coal fines or dust blowing from trucks and rail cars is also a major problem. The Big Sandy River tributaries are totally devoid of native mollusk species, and the upper Powell River has lost nearly all its native mollusks as a result of siltation and acid mine drainage.
Throughout the Commonwealth, swamps, marshes, and bogs have been drained and converted to more "productive" land uses in human-dominated ecosystems. Drainage of wetlands began early in Virginia's history with a major project focusing on Great Dismal Swamp to reclaim land for agriculture.
Humans have influenced the nature of Virginia for at least 12,000 years. Sometimes we have accelerated natural processes; sometimes we have interrupted them. As a consequence of human activity, species have been lost from Virginia's flora and fauna; but species have also been added. Our landscapes today record the cultural and economic history of Virginia's people as much as they record natural history. Our values and needs and our understanding (or lack of understanding) of how our actions change our environment dictate which other species will continue to share the human habitat with us.
Based on "The Nature of Virginia" by Susan L. Woodward and Richard L. Hoffman, pp. 21–41 in Virginia's Endangered Species, coordinated by Karen Terwilliger, 1991 (Blacksburg, VA: The McDonald & Woodward Publishing Company).
