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Ozark, Oauchita-Appalachian Forests

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Map Legend & Subregion List

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NameColor on MapCEC Code*
Ouachita Mountains8.4.8
Arkansas Valley8.4.7
Boston Mountains8.4.6
Ozark Highlands8.4.5
Blue Ridge8.4.4
Ridge and Valley8.4.1
Southwestern Appalachians8.4.9
Central Appalachians8.4.2
Western Allegheny Plateau8.4.3

* This code refers to the CEC's Level 3 ecoregion codes for North America, see here.

About the Ozark, Oauchita-Appalachian Forests

The Ozark, Oauchita-Appalachian Forests region includes two discontinuous blocks. The Ozark and Ouachita portion, sometimes referred to as the U.S. Interior Highlands, is located in northern Arkansas, southern Missouri, and eastern Oklahoma. To the east, separated by about 250mi / 400km, a large region of similar topography and climate occur in the Appalachians, stretching from northern Alabama, northeast through Tennessee, Georgia, western Virginia and North Carolina, West Virginia, eastern Kentucky, Southeast Ohio, and into much of Pennsylvania. This region includes all but the northernmost portions of the Appalachians, which are instead considered part of the Atlantic Highlands, owing to their considerable ecological differences, sharing more in common with other northern or boreal forests.

The Appalachians are an ancient mountain range, being formed about 480 million years ago, and now severely eroded and at a small fraction of their original height.

This region is mountainous, but elevations are low relative to mountains of western North America. The highest point is Mount Mitchell, at 6,684 ft (2,037m); there is no tree line anywhere in the region, and there are only modest differences in precipitation and temperature. Unlike in the west, where moisture primarily arrives from the Pacific ocean, precipitation here can also arrive from the east (Atlantic ocean) and south (Gulf coast), with east-facing slopes receiving more rainfall in many areas. Moisture is abundant, and there is never enough rain shadow to produce areas dry enough to appreciably change the cover type.

The climate ranges from humid subtropical at lower elevations to a subtropical highland (oceanic) climate at the highest altitudes. The climate here shares something in common with the coastal regions of the Pacific northwest, but is more variable and extreme. Forest cover is extensive, with mostly hardwood forests at lower altitudes, moving into mixed and coniferous forests as one ascends. This area is high in plant biodiversity due in part to the range of climate and altitude; many cold-loving species reach their southernmost limit in this region, but there are also many species from warmer regions that extend into the milder parts of this region. The island-like nature of the high elevation regions has led many species to be threatened by global warming and climate change.

This region is less populated and developed than its surroundings. The population is mostly rural and there is significant poverty. Agriculture is important here, and farming is diversified, with no clear dominant crops. This region has been heavily used for coal mining, in recent years often utilizing environmentally-damaging practices of strip mining and mountaintop removal. Extensive damming for hydroelectric power, especially through the Tennessee Valley Authority, has also altered the region. Although there are many environmental problems in this region, forest cover remains high, owing to the steeper topography, lower population, and lack of large-scale agriculture.

Most of this region is surrounded by the flatter, warmer, and somewhat drier Southeastern USA Plains. At the north end, the mountainous regions border the Atlantic Highlands, a mountainous region with a different geologic history. To the northwest, mainly in Ohio, this region has two small borders with the Central USA Plains and the Mixed Wood Plains.

Most of this region is bordered to the southeast by the Ridge and Valley region, and to the northwest by the much flatter Interior plateau. The southwestern end is bordered to the west by the Southeastern Plains. These borders are all abrupt and marked by clear geologic features. To the northeast, there is a more gradual transition corresponding to the climate cooling, leading to a more gradual transition into the Central Appalachians and the Western Allegheny Plateau. These borders are more arbitrary and less well-defined.