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Plants and Animals:
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prairies in Illinois are on thick, layers of sediment deposited by
glaciers and glacial streams. However the Drummond Dolomite
Prairie, located on the western edge of Midewin, occurs on thin
soils overlying dolomite bedrock. Because these soils were not
particularly suitable for agricultural purposes, the dolomite
prairie is one of the best-preserved natural communities on the
site. The dolomite, which is a calcium magnesium carbonate, lies
within a meter of the surface. As a consequence, the thin overlying
soils are alkaline and have a high magnesium content an important
Because the bedrock impedes drainage, the soils are frequently saturated in the spring, but because the thin soils have a low water holding capacity, they dry out more quickly during dry seasons. In some places a dolomite pavement occurs with no soil whatsoever. Drummond Dolomite Prairie contains a mix of wet, mesic, and dry prairie, which intergrade into each other.
The wet dolomite prairie includes tufted hair grass (Deschampsia caespitosa var. glauca), blue-joint grass (Calamagrostis canadensis), prairie cord grass (Spartina pectinata), and swamp milkweed (Asclepius incarnata). Riddells goldenrod (Solidago riddellii) occurs on soils that are less wet, along with Crawes sedge (Carex crawei), a threatened species in Illinois, which prefers a calcareous environment. Other Illinois endangered and threatened plants that occur in the wet to wet-mesic dolomite prairie are hairy marsh yellow cress (Rorippa islandica var. hispida) and slender sandwort (Arenaria patula). Butlers quillwort (Isoëtes butleri), another endangered plant in Illinois, also occurs in the adjacent Des Plaines Conservation area and may occur in the wet parts of Drummond Dolomite Prairie (Glass, 1994).
The dry and dry mesic dolomite prairies at Midewin contain two state and federally endangered and threatened plant species, hairy false mallow (Malvastrum hispidum), and leafy prairie clover (Dalea foliosum). Other plants characteristic of the dry dolomite prairie are side-oats grama (Bouteloua curtipendula), which also exists at mesic sites, prairie dropseed, nodding wild onion (Alium cernuum), low calamint (Satureja arkansna), hairy beard-tongue (Penstemom hirsutis), and round-fruited St. Johns-wort (Hypericum sphaerocarpum).
On thin, gravelly, dry soils and on exposed dolomite pavement, only a very patchy covering of drought tolerant species occurs. Prickly pear cactus (Opuntia humifusa) and side-oats grama grass occur at such sites. Lichens and mosses grow on the exposed dolomite and the soils adjacent to it. The lichen (Catapyrenum lechneum) grows in soil pockets between the dolomitic pavement, and the lichen Dermatocarpon miniatum grows directly on exposed bedrock.
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