Biodiversity of the Southern Appalachians
The southern Appalachian Mountains are one of the most biologically diverse regions in the temperate world. Biodiversity is extremely high in terms of both the variety of different species and the abundance of each species. Nearly 10,000 species are already known to exist here, with more discovered each year, some of which are new to science!
Some kinds of organisms, such as salamanders and fungi, reach their highest levels of diversity in the Southern Appalachians. Other diverse groups include trees, mosses, millipedes, spiders, moths, beetles, and snails. Many of these species are endemic to this region, found here and nowhere else in the world.
Northern relic species contribute to the biodiversity of the region. Animals such the pygmy shrew, red squirrel, and saw-whet owl, as well as plants such as skunk cabbage and ground juniper, can persist well south of their main range along the cool, moist, high elevation forests of the Southern Appalachians.
Ice Age Glaciers
During the Pleistocene Epoch (about 11,000 years ago), much of North America was covered by ice. Northern species that were forced southward by advancing glaciers found refuge in the Southern Appalachians. When the glaciers finally retreated, many of these species remained.
A wide range in elevation mimics changes in latitude, only over a shorter geographic distance. This results in an overlap of southern and northern species. Deep river gorges provide comparatively stable microclimates for many species. Isolated mountain peaks may serve as habitat islands, and result in genetic diversification of species.
Temperatures in the region are cool and mild, with a mean annual low of 40° F and a high of 61° F. The Highlands Plateau has an average annual rainfall of more than 87 inches, but occasionally receives more than 100 inches, which qualifies it as a temperate rainforest.
Arachnids include spiders, ticks, and mites. More than 460 different species have been observed in the Southern Appalachians, but as many as 800 are believed to exist.
Over 100 species of mollusks are known from the Southern Appalachians. The majority of these species are land snails.
The moist leaf litter and rich soils of the forest floor provide ideal habitats for a variety of millipede species. Millipedes reach record diversity in the Southern Appalachians with over 230 different species known to exist.
More species of salamanders exist in the southern Appalachian Mountains than anywhere else in the world, and nowhere are they more abundant. The Great Smoky Mountains National Park alone has 30 species, and many more occur in other parts of western North Carolina. Several classic studies of salamanders have been conducted here at the Highlands Biological Station.
Most Southern Appalachian salamanders lack lungs and respire through their skin. Consequently, individuals must keep moist to avoid desiccation. The region’s cool, wet climate provides an ideal environment for the survival of these amphibians.
Salamanders need cool, wet environments in which to live and reproduce. The southern Appalachian Mountains are frequently blanketed in fog. Forests have numerous seeps and streams. Moist forest floor leaf litter and rotten logs provide ideal microclimates for many salamander species and their invertebrate prey.
Salamander species are often separated into finely divided niches to reduce competition and predation. Habitat segregation is usually determined by body size. For example, a streamside community frequently consists of a large aquatic species, a medium semi-aquatic species, and a smaller terrestrial species.
A short video created by Joe Milmoe, George Mason University:
More than 100 native trees, 1,400 other flowering plants, and 500 moss and fern species are found in the Southern Appalachians. Nearly 60 kinds of trees and shrubs may grow in diverse cove hardwood forests. Spruce-fir forests occur at elevations above 5000 feet, northern hardwood and pine-oak forests occur at lower elevations, and hemlock forests occupy moist, streamside habitats.
The southern Appalachian Mountains are also famous for their high diversity of fungi. Mushrooms, molds, and sac fungi thrive in the wet mountain environments. Nearly 2,300 species have already been identified, but scientists estimate that there may be as many as 20,000.