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Northern Shawnee Hills

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About the Northern Shawnee Hills

The Northern Shawnee Hills is a rugged, forested region located entirely within southern Illinois, extending east-west from the Mississippi River to the Ohio River.

This region consists of a high, south-facing escarpment, and numerous cliffs, bluffs, ravines, and canyons. The area is underlain by a mixture of erosion-resistant sandstone, and more easily-eroded siltstone and shale. Most of the region was never glaciated, although the northernmost end of this region came close to the glacial limit during one of the earlier glacial periods. There are loess deposits on top of the bedrock in much of the area. Soils here are mostly formed either on loess or residuum formed from decomposition of the bedrock. These soils have long-since been leached of soluble nutrients, and often have fragipans, lower horizons that hinder drainage and root penetration. The combination of poor drainage, low nutrients, and steep topography lead this region being poorly suited for Western agriculture, and also restrict and shape what wild plants can grow here.

Before European settlement, this region was almost entirely forested. The forests here were mostly cleared, although small areas of old growth remain, including 3,300 acres at the The Garden of the Gods Wilderness Area, mostly of post oak (Quercus stellata) and blackjack oak (Quercus marilandica). Following the clearing of the forests, agriculture was attempted, but much of the region proved ill-suited to agriculture, and the farmland quickly became depleted, and soil erosion became a major problem throughout the region. In the 1930's and 40's, there were attempts to restore this area by planting pines. Since then there have been various gradual attempts to restore the biodiversity here.

Nowadays, the region still has significant areas of forest, but there is also pastureland, hayland, and some cropland. The forest type differs considerably with changing slope aspect. Uplands are dominated by white oak (Quercus alba), black oak (Quercus velutina), and shagbark hickory (Carya ovata). Cool, shaded ravines support forests of northern red oak (Quercus rubra), American beech (Fagus grandifolia), and sugar maple (Acer saccharum), as well as numerous other more northerly species. Floodplains and bottomlands have forests of American sycamore (Platanus occidentalis), eastern black walnut (Juglans nigra), kentucky coffeetree (Gymnocladus dioicus), sugarberry (Celtis laevigata), and honeylocust (Gleditsia triacanthos).

A large portion of this region consists of public, protected lands, mostly in Shawnee National Forest, but there is also some state land, including Ferne Clyffe State Park and Giant City State Park. This region is sparsely populated, but there are a few very small towns, the largest of which is Makanda.

This region is bordered to the south by the Southern Shawnee Hills, a lower, less-rugged region with carbonate-rich rocks and karst topography. At its western end, this region borders the Southern Ozarkian River Bluffs, descending to the Mississippi river, and to the east and to the north at its eastern end, it borders the Wabash-Ohio Bottomlands along the Ohio river. In the rest of the region, it is bordered by the low, flat Southern Illinoian Till Plain.

References

1. Woods, A.J., Omernik, J.M., Pederson, C.L., Moran, B.C. "Level III and Level IV Ecoregions of Illinois", U.S. Environmental Protection Agency, Washington, DC (2006) Web.