Southeastern USA Plains
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Ecoregion Data
| 8.3 - Southeastern USA Plains | |
| Region | |
|---|---|
| USA North America Northeastern USA Southeastern USA Midwest | |
| Parent Ecoregions | |
| Eastern Temperate Forests | |
| Child Ecoregions | |
| Piedmont Southeastern Plains Interior Plateau | |
| Geography | |
| Blue Ridge Mountains St. Lawrence Valley Appalachian Plateaus | |
| Hydrography | |
| Blue Ridge Mountains St. Lawrence Valley Appalachian Plateaus | |
Description
Ecoregion 8.3 of the US Environmental Protection Agency (EPA) framework lies within the broader Eastern Temperate Forest realm. It encompasses rolling uplands, plateaus, and dissected low mountains of the central and eastern United States, formerly dominated by mixed hardwood forests, and now a mosaic of forest, agriculture and urban land uses. Soils are relatively fertile, and the region has a humid climate with well-defined seasons.
Physical Setting
Ecoregion 8.3 occupies the central portion of the Eastern Temperate Forests, extending across rolling uplands, dissected plateaus, and broad valleys of the eastern and central United States. Elevations generally range from low plains near major rivers to moderately high ridges and hills, seldom exceeding 600 m. The terrain is a mix of gently undulating farmland and wooded slopes, reflecting the region’s sedimentary bedrock and long history of weathering and erosion.
Biological Setting
Within Ecoregion 8.3, natural vegetation historically included extensive oak–hickory forests (white oak, red oak, post oak, hickories) and, in more mesic or sheltered ravines, mixed mesophytic forest elements such as beech, basswood, sugar maple, ash and yellow-poplar. Undergrowth layers of shrubs, vines and herbaceous plants were rich, and the faunal communities included a variety of mammals (white‐tailed deer, raccoon, gray fox), birds (ruffed grouse, woodpeckers, ovenbird) and amphibians (dusky salamander, northern water snake) adapted to the forested uplands and valley bottoms. Many low-lying bottomland sites supported deciduous floodplain forests of species like silver maple, sycamore, green ash, and swamp chestnut oak, though many of these areas have been converted to agriculture or development. Because of the region’s favourable soils and moderate climate, human land-use change (cropping, pasture, urbanization) has been substantial, which means that remnant forest patches, edge habitats and semi-natural corridors are increasingly important biodiversity refugia. Ecoregion 8.3 is characterized by a terrain of rolling hills, dissected plateaus, and broad valley bottoms, lying between the more rugged Appalachian uplands to the east and the flatter plains or alluvial regions to the west. The underlying geology generally comprises Paleozoic sedimentary rocks (limestones, sandstones, siltstones, shales) often with a mantle of loess, glacial till (in parts) or saprolite cover. Soils are commonly Alfisols and Inceptisols (and in more weathered zones Ultisols) under a mesic soil-temperature regime and a udic (moist) soil-moisture regime. Streams vary from moderate to high gradient in upland settings to low-gradient meandering rivers and terraces in valley bottoms, and alluvial deposits and terraces are common in the lower relief areas. The physical setting therefore provides a heterogeneous mix of upland forest, valley bottom wetlands or floodplains, and agricultural plains.
Climate
The climate of Ecoregion 8.3 is a humid mid‐latitude regime, where summers tend to be warm to hot and winters cold, with a relatively even distribution of precipitation through the year. Frost‐free periods typically range from ~130 to 230 days depending on latitude and elevation. Mean annual temperatures vary across the region (for example roughly 7°C in the cooler portions to ~14°C or more in warmer portions). Annual precipitation is often in the range of ~900 to 1,300 mm (though varies by local topography and latitude). The moderate climate, combined with relatively fertile soils and seasonally available water, has supported both natural hardwood forests and significant agricultural development. From a resource‐extraction and environmental-health perspective, the region’s climate means that disturbances (e.g., deforestation, extraction of minerals, land-cover change) have strong potential to affect hydrology, soil erosion and ecosystem resilience due to the active seasonal growth and decomposition cycles.