Home » Regions » North America » Eastern Temperate Forests » Southeastern USA Plains » Piedmont » Southern Outer Piedmont

Southern Outer Piedmont

Page contents

About the Southern Outer Piedmont

The Southern Outer Piedmont is the largest region in the Piedmont, covering most of the Piedmont's southern portion, except the northwestern regions closest to the Appalachians, and a few isolated areas. This region stretches from a small portion in eastern Alabama, through much of Georgia, much of northwestern South Carolina, and a sizeable portion of North Carolina, where it narrows at its northern end.

This region consists mostly of irregular plains with relatively low, gentle hills. Underlying bedrock is mostly gneiss, schist, and granite, much of which is heavily metamorphosed and deformed. The bedrock is covered in most places by deep, heavily weathered soils, with red clay soil closest to the surface, heavily weathered soils rich in iron but leeched of calcium and other more soluble metals. Soil diversity is greater in the east of this region, which has greater underlying mineral diversity. Some areas have alkaline soils that formed over diabase, diorite, or gabbro. The climate here is humid and subtropical, with precipitation roughly equally distributed throughout the year. Although moisture is sufficient for lush plant growth on most sites, this region is quite sunny and plants on drier sites can experience significant drought stress.

There is much uncertainty about the original vegetation cover here, and the relationship between soil type and plant communities. The area was probably mostly forested, but there were also small, scattered areas of prairies or blackjack oak (Quercus marilandica) savannas.

Presently this region has a mix of forest and cleared land; in some areas the forests are more fragmented than others, and their composition varies considerably. Abandoned fields in earlier stages of succession typically support a mix of shortleaf pine (Pinus echinata), virginia pine (Pinus virginiana), and loblolly pine (Pinus taeda), whereas older forests tend to be dominated by a mix of oaks.

Over most of this region, it is bordered to the northwest by the Southern Inner Piedmont, except in the north where it is bordered instead by the Northern Inner Piedmont. This northwestern border is ill-defined and represents a gradual transition between soil temperature regimes and associated changes in plant communities, but in general the region to the northwest tends to be hillier, more forested, and have higher rainfall and less cropland. In the north, this region is bordered to the southeast by the Carolina Slate Belt, a region underlain by finer-textured rocks; this border is abrupt and well-defined, marked by a geologic shift. Farther south, this region is bordered to the southeast by the Sand Hills, and in Alabama, to the south by the Fall Line Hills; these are sandy, hilly regions that are part of the coastal plain, and these borders are also well-defined geologically and marked by a fall line. In South Carolina there is also an area where this region directly borders a disjoint section of the Atlantic Southern Loam Plains.

References

1. Comstock, J.A.; Griffith, G.E.; Omernik, J.M. "Ecoregions of North Carolina: Regional Descriptions", (2002) Web.

2. Griffith, G.E., Omernik, J.M., Comstock, J.A., Lawrence, S., Martin, G., Goddard, A., Hulcher, V.J., and Foster, T. "Ecoregions of Alabama and Georgia (color poster with map, descriptive text, summary tables, and photographs)", U.S. Geological Survey, Reston, VA (2001) Web.