| General Description |
The cove forests of the Southern Appalachians are some of the most biodiverse habitats in the Temperate Zone. Their cool, moist climates favor the growth of complex, multi-story plant communities; thick, rich litter layers; deeply-shaded rock faces and crevices; and multitudes of perennial springs and cool, clear-flowing streams. These habitats, moreover, have persisted in place for hundreds of millions of years. They survived unglaciated through the Ice Age and their steep slopes have largely protected them from permanent conversion to human uses. They provide refuges for many relicts of otherwise long-vanished floras and faunas. They are also centers of endemism in their own right, with new species being discovered on a regular basis.
Although there are few areas that still support virgin forests, these habitats continue to serve these functions during the Age of Man largely due to their steep slopes, which have resisted cultivation and large-scale development. In North Carolina, in particular, the lack of coal and other extensive mineral deposits have spared these communities from the massive strip mining and mountain-top removals that have taken place in other parts of the Appalachians. Today, these habitats are the most extensive of our remaining natural areas and retain the greatest amount of their pre-Colonial species diversity.
The habitat described here includes species that are associated with the most generalized features of the cove forests, particularly their deeply-shaded, cool, moist microclimates. It is similar, in this regard, to the General Mesic Hardwood Forests habitat, but comprises species that are restricted to the Mountains in North Carolina. Within the Mountains, however, these species occupy a wide altitudinal range, extending from the foothills of the Blue Ridge up into the areas covered with stands of Northern Hardwoods. Although the majority of these habitats occur within the steep, montane "coves" proper, higher ridgetops are also included where they are regularly swept by clouds and rain and support populations of the same mesophilic species that are more confined to ravines at lower elevations. The Determining Species of this habitat occur in both rich and acidic coves; those that are more tightly associated with either of these types are treated in other, more specifically-defined habitats.
The plant species that are restricted to this habitat are relatively few in number, with more species found only in either the rich or acidic varieties of cove forests or more widely in mesic habitats outside the mountains. They include some of the most characteristic tree species of cove forests per se, Yellow Birch and Fraser Magnolia, as well as Red Ramps, the herbaceous species made famous in the Southern Appalachians by Ramp festivals. American Ginseng -- another species famously exploited in the cove forests -- is, on the other hand, more typical of the species that may show a concentration in the mountains but that also occur more generally in mesic habitats all the way across to the eastern edge of the Coastal Plain.
Specialized herbivores are likewise few in number, consisting primarily of species associated with Sugar Maples or montane birches. Much more numerous are more generalized herbivores that feed on a variety of plant species -- most not confined to cove forests -- but which themselves have requirements for cool, moist, forests that restrict them to these habitats. Virtually all of these generalized herbivores have their center of geographic distribution located in the northern states or in Canada. The same is true for some of the predatory species of animals belonging to this habitat, particularly the birds and mammals, all of which are much more common farther north.
For the least vagile species associated with the forest floor, on the other hand, the cove forests of the Southern Appalachians are major centers of their diversity. These species are so highly dependent on specific temperature, moisture, and forest floor conditions that many of them are not only confined to the Southern Appalachians but are endemic to particular mountain massifs within this region. Although their ancestors were able to occupy much wider areas under colder, wetter climate conditions -- as prevailed in the Pleistocene -- their descendants became isolated in much smaller areas when warmer, drier habitats developed in the lowlands between these massifs (in some cases, the rivers in these valleys also act as effective barriers).
The best known of these species are the Plethodontid Salamanders, of which only the most terrestrial species -- members of the genus Plethodon -- are included in this habitat. Currently (and likely to increase), there are sixteen Determining Species for this habitat, out of the twenty that have been recorded in North Carolina. Members of this group in particular have evolved in close association with the cool, wet forest floor conditions that have allowed them to free themselves from the aquatic habitats needed by other amphibians for breeding and larval development: all members of this genus lay their eggs in underground burrows where the high soil moisture keeps them from drying out. This allows them to range freely across the forest floor, independent of surface waters, unlike most of the other members of this family (e.g., Eurycea and Desmognathus species) that are treated in habitats that contain surface waters as important features.
As described by Thomas and Hedin (2008), a number of invertebrate groups associated with the forest floors of mountain coves show similar centers of diversity in Southern Appalachian coves. These include the Xystodesmid Millipedes (Shelley and Whitehead, 1986; Marek and Bond, 2006), Phalangodid Opilionids (Thomas, 2007), Hypochilus and Nesticus spiders (Catley 1994; Hedin, 1997). Certain groups of land snails and ground beetles could also be added, along with probably many other groups of understudied invertebrates. Species that are associated with the forest floor itself are considered Determining Species of this habitat but those that are tightly associated with mesic rock faces are treated separately.
Arguably the most spectacular, if also the most obscure and solitary, is the species that Thomas and Hedin highlight in their paper, Fumontana deprehendor. This tiny, highly weird-looking Harvestman is found only in the cove forests of the Southern Appalachians, is the sole member of its genus, and appears to be most closely related to species that are now restricted to South Africa and South America. It thus appears to be a relict of a Gondwanan fauna that was once widespread in the Paleozoic, with the implication that it has been an inhabitant of the Southern Appalachian region for hundreds of millions of years. As such it would provide a striking confirmation of the stability of the ecosystems of this region, particularly its mesic forests.
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