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Southern Ozarkian River Bluffs

Ecoregion in Shawnee NF in IL, MO

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The Southern Ozarkian River Bluffs ecoregion is composed of rugged, loess-capped bluffs and ravines that flank the Mississippi River in southwestern Illinois. It is part of a nearly continuous, forested river corridor that promotes the northward dispersal of southern fauna. Today, considerable forest remains in The Southern Ozarkian River Bluffs ecoregion, mostly within the Shawnee National Forest; prevailing land use and associated environmental issues are distinct from those in nearby, agriculturally-dominated regions such as the Middle Mississippi Alluvial Plain (72e). Scattered loess hill prairie occurs on bluff tops and some slopes, but is much less common than in Ecoregion 72l (Schwegman, 1973, p. 25). The upland forests of The Southern Ozarkian River Bluffs ecoregion are species-rich, and contain oaks, sugar maple, bitternut hickory, and basswood. Floodplain forests contain American elm, cottonwood, white oak, red oak, sycamore, and river birch. Plants adapted to acidic soil, including shortleaf pine and azalea, are found on steep, cherty slopes; they are absent from Ecoregion 72l, where acidic soils are generally lacking (Schwegman, 1973, p. 6). The Southern Ozarkian River Bluffs (72g) is underlain by Paleozoic cherty limestone that is more resistant to erosion and groundwater solution than the limestone of the Karstic Northern Ozarkian River Bluffs (72l); as a result, The Southern Ozarkian River Bluffs ecoregion is more rugged, has more surface drainage, and has much less karst than Ecoregion 72l (Schwegman, 1973, p. 24). Soils in The Southern Ozarkian River Bluffs ecoregion are usually Alfisols. they developed from thick loess on bluff tops, and thin loess, acidic residuum, or colluvium on steep slopes (Natural Resources Conservation Service, various dates). The Southern Ozarkian River Bluffs ecoregion is driftless unlike Ecoregion 72l which is partly mantled by Illinoian till (Lineback, 1979). Distinctive amphibian and reptile species occur, and are characterized by Ozarkian and southern flora that are absent from the River Hills (72f) (Schwegman, 1973, p. 24; Smith, 1961, p. 12-13). In Illinois, the scarlet snake is known to occur only in The Southern Ozarkian River Bluffs ecoregion, and the spring cavefish is limited to a few areas in southern Illinois including The Southern Ozarkian River Bluffs ecoregion. The flat-headed snake is listed as threatened in Illinois, and occurs in both Ecoregions 72 and 72g; it is found nowhere else in the state (Schwegman, 1973, p. 25; Illinois Natural History Survey, on-line resource).

— EPA

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Ecoregion