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Southern Hilly Gulf Coastal Plain

↑About the Southern Hilly Gulf Coastal Plain

The Southern Hilly Gulf Coastal Plain is a portion of the Southeastern Plains extending from a small portion of western Georgia through large portions of Alabama and Mississippi. The region has a broad crescent shape, oriented east-west in its eastern end, but broadening in the west and also curving to the north.

This region consists of dissected, irregular plains and low, rolling hills. Asymmetrical ridges are common here, with broad tops, and gentle south- and west-facing slopes but steeper north- and east-facing slopes. There are also some broad floodplains and adjacent broad terraces. Streams are mostly low to moderate gradient. This region is underlain mostly by long bands of sand, clay, and marl, a carbonate-rich mudstone, and there is also some limestone and lignite (brown coal.) These bands follow the shape of the region, east-west in the east, and curving to eventually run north-south in the northwestern part of the region. The diversity of substrates leads to diversity in soil texture and fertility, with a mix of clayey, loamy, and sandy soils; the soils tend to be reddish in color, lighter than in the bordering flatwoods and blackland prairie regions.

This area was originally mostly covered in oak-hickory-pine forest, more common in the north, southern mixed forest more in the south, some pine forest in the south, and southern floodplain forest on the bottomlands. However, the mild subtropical climate, combined with diversity of soil and topography leads this area to be exceptionally high in plant biodiversity. The oak-hickory-pine forest was dominated by post oak (Quercus stellata), blackjack oak (Quercus marilandica), southern red oak (Quercus falcata), shortleaf pine (Pinus echinata), pignut hickory (Carya glabra), and mockernut hickory (Carya tomentosa). The pine forest supported mostly longleaf pine (Pinus palustris) with some shortleaf pine, blackjack oak, sand post oak (Quercus margaretta), and bluejack oak (Quercus incana). Southern floodplain forest supported cypress and tupelo on the wettest sites, and bottomland hardwoods and loblolly pine (Pinus taeda) on slightly better-drained sites.

This region currently has a mix of land use, but a significant portion of it remains as wild forest. There are also pine plantations and some areas of pasture, hayfields, and cropland. The region produces cattle, poultry (mostly in the southwest), hay, cotton, peanuts, corn, and soybeans. There are also a few areas of oil and gas extraction in the southwest. There are some areas of protected public lands, most notably Tombigbee, Bienville, and De Soto National Forests in Mississippi.

Over most of its length, this region is bordered inland, to the north and northeast, by the lower, much flatter Flatwoods/Blackland Prairie Margins. There is an area in the east where it directly borders the Blackland Prairie to the north, a region in which fine-textured soils that expand and contract limit plant growth. This region is interrupted by the Southeastern Floodplains and Low Terraces along floodplains of major rivers. Most of this region is bordered to the south by the Southern Pine Plains and Hills, a fire-prone area with droughtier soils. However the middle of this region is bordered to the south by the highly rugged and mostly forested Buhrstone/Lime Hills. The western portion of this region is also interrupted by the Jackson Prairie. The northwest of this region is bordered to the north by the Northern Hilly Gulf Coastal Plain, in an arbitrary border that corresponds to a change in climate and forest type rather than underyling geology. This region is bordered to the west by the Loess Plains, except at its southernmost end where it is bordered to the west by the Southern Rolling Plains.

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↑References

1. 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.