$title="Physical Environment - Soils"; include "/local/php/ismsite/midewin/header.php"; ?>
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prairies developed in a wide variety of soils. The topography and
soils at Midewin support many of the major prairie types native to
Illinois. Dolomite prairie, one of the rarest prairie types, is
present at Drummond Dolomite Prairie on the western side of Midewin
National Tallgrass Prairie. Areas of outwash sand near the Kankakee
River support a xerophytic (dry loving) sand prairie. Typical of
the Grand Prairie, many of the soils of Midewin are poorly drained,
supporting wet prairie and marshes.
The soils at Midewin are developed from glacial till, outwash sand, proglacial lake sediments, and dolomite bedrock in the area. Prairie soils (mollisols) are widespread. The surface horizon is thick (at least 10 inches), dark colored, and rich in organic matter. Decomposed roots from prairie sod and charcoal from prairie fires contribute to the color and organic matter. Forest soils (alfisols) are present in the groves and upland forests. The forest litter promotes leaching of organic matter from the surface horizons, which are consequently light colored. These soils indicate a long residence time for the groves or forest vegetation upon them. Prairie-forest transition soils also occur in areas where forest has more recently invaded prairie. Shallow, dolomitic soils occur in Drummond Dolomite Prairie. Sandy soils exist in the outwash areas near the Kankakee. Gravelly, well-drained soils occur in scattered locations.
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