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Southern Shawnee Hills

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About the Southern Shawnee Hills

The Southern Shawnee Hills is a hilly region located entirely within Illinois, oriented east-west and stretching between the Mississippi river in the west to the Ohio River in the east. Although most of the region is contiguous, there is a small discontinuous piece to the southeast of the main section.

This region is underlain mostly by a mix of limestone and sandstone, which leads to irregular karst topography, with abundant caves, sinkholes, and springs. The topography averages lower and flatter than areas to the north, but is markedly hillier than the bottomlands along the rivers to the east and south. There are some small streams with intermittent or seasonal flow, but most streams are spring-fed and cold in summer.

At the time of European settlement, this area was mostly forested, but there were probably small areas of limestone glades and dry prairies. The location of this area, combined with its topographic diversity, leads it to be high in plant biodiversity. Species from the Appalachians, Ozarks, Great Plains, and Mississippi Alluvial Plain can all be found here. Most of the original forests here were cleared, but there are a few small remnants of old growth. Agriculture was initiated here, and the flatter topography and limestone-derived soils led to less depletion of the agricultural land than the areas to the north, so while some of the land was abandoned, more of it is still farmed.

Presently, this area still has extensive forest, as well as many limestone glades, but there are considerable areas of pastureland, hayland, and some cropland. Dry uplands feature blackjack oak (Quercus marilandica), post oak (Quercus stellata), scarlet oak (Quercus coccinea), pignut hickory (Carya glabra), and white oak (Quercus alba). Cooler, shaded ravines support more forests with a more northerly character, including northern red oak (Quercus rubra), American beech (Fagus grandifolia), and sugar maple (Acer saccharum). There are also floodplain forests in the bottomland areas. Limestone glades support little bluestem (Schizachyrium scoparium) and side-oats grama (Bouteloua curtipendula), along with other more southerly plants.

There is some public protected land here, including part of Shawnee National Forest, which mostly covers the region to the north but includes significant portions of this region as well. There is also significant state-owned protected land, including the three large, contiguous areas of Heron Pond Preserve, Little Black Slough Nature Preserve, and Cave Creek Glade Nature Preserve. This region is mostly rural, but has some towns, the largest of which is Anna, followed by is neighbor Jonesboro, and the other town of Vienna. There are numerous smaller towns.

This region is bordered to the north by the Northern Shawnee Hills, which is much more rugged and lacks limestone and karst. It is borered to the east and south by the Wabash-Ohio Bottomlands, a low, flat region along the Ohio river; this region also separates the main portion of this region from the other small section. To the west this region is bordered by the Southern Ozarkian River Bluffs, which descend to the Mississippi Alluvial 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.