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Southern Limestone/Dolomite Valleys and Low Rolling Hills

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About the Southern Limestone/Dolomite Valleys and Low Rolling Hills

The Southern Limestone/Dolomite Valleys and Low Rolling Hills are a region of the Ridge & Valley portion of the Appalachians, that can be seen as the southern counterpart to the Northern Limestone/Dolomite Valleys. This region stretches northeast-southwest from about Roanoke, Virginia, barely into West Virginia, south through Tennessee and into northwestern Georgia and northern Alabama. Although irregular in dimensions, it tends to be one of the widest parts of the Ridge and Valley region and makes up the largest total portion of this region in the south.

This lowland region consists of low ridges and broad valleys underlain mostly by limestone and dolomite, with small amounts of interbedded shale and other rocks. Due to the solubility of these minerals, the region has karst topography, with sinkholes and underground streams. The presence of small amounts of impermeable but more easily-eroded shale imparts some diversity to the topography and soil types here. The region has fewer surface streams, and those that exist tend to have stable year-round flow, more neutral pH, and gentle gradients. The soils here tend to be nutrient-rich and ideal for western agriculture.

The climate is humid and subtropical. As this region stretches far in the north-south direction, the north of this region is significantly cooler than the south at all times of year, with average temperature differences as large as 5°F (2.8°C) from the northernmost and southernmost ends. The average frost-free growing season varies from 175 days in the north to 225 days in the south. The southern end of this region has the warmest climate of anywhere in the Appalachians.

This region was originally almost entirely forested, with Appalachian oak forest and mixed oak forest on drier upland sites, mesophytic forests on more mesic sites, and bottomland oak forests in lower, wetter areas. There were also some cedar barrens in areas with exposed limestone outcroppings. In the far south end, the hotter climate led to some Oak-Hickory-Pine forest on drier sites.

Nowadays there is a mix of land use here. Areas with fertile soil are extensively farmed, with both cropland and pasture. Crop production here is diverse, varying a lot by both soil type and climate. There is production of corn, soybeans, hay, beef, pigs, and poultry, and in the far south, also cotton. The northernmost portions of this region are heavily farmed, with little forest cover remaining. There are some pine plantations, particularly in the south. There is also significant urban and suburban development, particularly around the three largest cities of this region: Chattanooga, TN, Knoxville, TN, and Roanoke, VA. All three of these metro areas extend outside this region, but are mostly located within this region. There is also significant rural residential development, and even the less populous parts of this region are more populated than the more rugged ridges of the Appalachians farther southeast and northwest.

This region is irregularly interspersed with other regions of the Ridge & Valley system. The most widespread border is with the Southern Shale Valleys, another low-lying region that tends to have less fertile soils. It also borders the more rugged, higher-elevation, forested regions of the Southern Sandstone Ridges and the Southern Dissected Ridges and Knobs. Outside the Ridge and Valley region, to the southeast this region borders two different sections of the Blue Ridge: the Southern Sedimentary Ridges, in most places, and in some places the Southern Metasedimentary Mountains. To the northwest, it borders various regions of the Central Appalachians in the north, and the Southwestern Appalachians in the south.

References

1. Woods, A.J, Omernik, J.M., Brown, D.D. "Level III and IV Ecoregions of Delaware, Maryland, Pennsylvania, Virginia, and West Virginia", U.S. Environmental Protection Agency: National Health and Environmental Effects Research Laboratory, Corvallis, OR (1999) Web.

2. Griffith, G.E.; Omernik, J.M.; and Azevedo, S.H. "Ecoregions of Tennessee (Poster)", U.S. Geological Survey, Reston, VA (1998) Web.

3. 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.