The Cove Topography and the Mixed Mesophytic Forest
On a mid-December morning, my commuter plane en route from Washington, D.C., to Charleston, West Virginia, traverses in a matter of minutes Virginia's historic Piedmont. Gaining altitude, the plane bisects the ridge and valley of the Shenandoah, where the Skyline Drive meanders south toward the Blue Ridge Parkway. Soon after, the horizon opens onto the great Allegheny and Cumberland plateaus, a crumpled terrain of lower elevation ridges, coves, and hollows, cloaked in a forest bristling skyward without leaves. On this forest, the world's oldest and biologically richest temperate zone hardwood system, the pioneering ecologist E. Lucy Braun conferred the name "mixed mesophytic."
Centered in southern West Virginia, the mesophytic has issued for more than a hundred million years from the black, unglaciated loam of the Central Appalachian coves. Studying the virgin forest in 1916, Braun theorized that these coves are the likely ancestral source of most temperate-zone forest species in the eastern United States. Ecologists are calling it the "mother forest."
Whereas most forest types are dominated by two or three species, the mixed mesophytic harbors eighty woody species in its canopy and understory. Among them are beech, yellow poplar, basswood, sugar maple, chestnut, sweet buckeye, red oak, white oak, yellow locust, birch, black cherry, cucumber tree, white ash, red maple, sour gum, black walnut, and various kinds of hickory. Yet the coherence of this forest region remains one of America's better kept secrets.1
In the 1950s, Braun returned to the Central Appalachian coves to examine a second-growth forest that remained "mixed mesophytic." In the 1990s, however, ecologists are warning that airborne nitrogen, sulfates, and ozone from the Kanawha, Ohio, and Tennessee river basins may be dealing the forest a fatal blow.2 Within the troubled eastern deciduous forests, the crisis of the mixed mesophytic poses a special case. If, as Braun argued, the central Appalachian coves sheltered biodiversity against the extreme cold that interrupted the evolution of surrounding forests, it follows that the same coves could again become banks of species diversity, sustaining heat-intolerant plants in a period of global warming.
[Detail] Mixed mesophytic cove topography in winter, Whitesville, WV. Alpine Images photograph by Jenny Hager. Used with permission.
[Detail] E. Lucy Braun, the pioneering ecologist who identified the mixed mesophytic forest as a coherent system. Mary Hufford. 1994/10/20. Library of Congress American Folklife Center.
[Detail] Autumn colors of forest canopy with morning fog. Alpine Images photograph by Jenny Hager. Used with permission.
[Detail] Standing dead tightbark hickory tree snag, Rock Creek. Alpine Images photograph by Jenny Hager. Used with permission.