Description & Physiography
The piedmont or foothills of the Appalachian Mountains is the oldest and most eroded part of the original Appalachian orogeny. It is bounded by the coastal plain to the east and the Southern Appalachians to the west. Elevations range from approximately 600 to 1,500 foot. Rolling hills with broad ridges that are irregularly and frequently dissected by drainages are typical for the piedmont. Rivers and drainages typically run southeastward in relatively narrow floodplains. While the piedmont ecoregion does not support as much biodiversity as adjacent regions such as the Southern Blue Ridge and Atlantic Coastal Plain, it is a key link between ecoregions and supports several endemic species and communities. Human population growth threatens biodiversity on one hand but on the other hand, also provides funding opportunities and multiple partners for conservation.
There are two distinct divisions to the piedmont rocks; one a set of Late Proterozoic and Paleozoic igneous and metamorphic rocks, and a second of lower Mesozoic (Triassic) sedimentary rocks which were deposited in graben basins faulted into the igneous and metamorphic rocks. These distinct divisions were used to stratify the piedmont ecoregion into subunits to account for the climatic and geologic range of factors shaping the biotic communities of the piedmont.
High grade metamorphic rocks such as schist, amphibolites, gneisses and migmatities, and igneous rocks like granite. Isolated granitic plutons like Stone Mountain in GA and Pilot Mountain in NC rise above the piedmont landscape. Occasional granitic flatrocks are found in the central and southern piedmont. A noteworthy feature in the piedmont is the Carolina slate belt, which contains gold deposits. The discovery of a 18 pound gold nugget in Cabarrus County, NC created the first Gold rush in the New World in the early 19th century. The Brevard Fault zone runs SW to NE cuts across the piedmont as a major feature whose true nature remains enigmatic.
Annual average precipitation in the piedmont ranges from 44 inches per year in Virginia to 58 inches per year in Alabama. The precipitation is more evenly distributed in the northern part of the piedmont with average seasonal high precipitation of just over 5 inches in July, average annual lows of 2.8 inches in November. The average highest monthly precipitation (6.8 inches) in the southern piedmont is in March, while the lowest precipitation (2.8 inches) is in January and February based on data form the Southeast Regional Climate center.
Plants & Animals
Introductions of exotic species have also taken a heavy toll on Piedmont Natural Areas leading to a simplification of ecosystems. More recently, outbreaks of new exotic pests have emerged such as: dogwood anthracnose, beech bark disease, gypsy moth, and hemlock wooly adelgid. As well, native pests such as the southern pine beetle have devastated both natural and planted stands of pine. Exotic forest pests and pathogens that could threaten forests in the piedmont if they spread from sites in North America where they are already present: Sudden Oak Death Syndrome – Phytophthora ramorum, Emerald Ash Borer – Agrilus planipennis.
Humans & History
The Piedmont has undergone many human-induced changes over the past few centuries. Extensive, open Oak Hickory Pine forests with isolated prairies and grasslands are believed to have occupied the vast majority of the region; hence they are considered the ecological ‘matrix’ vegetation across the bulk of the ecoregion. Tornadoes, ice storms and hurricanes, droughts and floods, lightening and anthropogenic fires have shaped and disturbed these forests. These forests have been heavily worked prior to and since the arrival of European settlers. Native Americans cleared forests for agriculture and the Europeans continued to clear large tracts of forestland for agriculture, home sites, industry, and other uses.
The Piedmont is heavily impacted by development, transportation corridors, urbanization, and urban sprawl. The U.S. Census identifies over 140 urban and urban clusters impacting the ecoregion. From the 2000 Census the total population of the Piedmont was 15,244,105 (density/square mile of 1,673). At that time the Census Bureau projected the 2004 population to be 16,808,305 (density/square mile of 1,766) for the area. Urban areas accounted for over ten million of the Piedmont 2000 population.