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Savanna Section

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About the Savanna Section

The Savanna Section is a section of the Driftless Area, an area that escaped glaciation, located in northwestern Illinois and southwestern Wisconsin.

This region has somewhat varied topography, with flat plateau remnants, broad, relatively level ridgetops, narrow, steep-walled valleys along smaller streams, some broad, flat bottomlands along larger streams and rivers, and isolated buttes (locally referred to as "mounds") capped by dolomite. Relative to the blufflands to the west and north, this region has more surface streams but fewer lakes. The bedrock here consists of limestone, dolomite, and shale, mostly heavily weathered into residuum. Throughout most of the region, however, this is covered by loess, fine, wind-blown deposits; except on the steepest slopes, where soil formed on residuum, most soils here formed on loess, and are well-drained and silty.

In the early 19th century, this region was mostly covered in dry to mesic prairies, with little bluestem (Schizachyrium scoparium) and side-oats grama (Bouteloua curtipendula), and oak savanna, primarily bur oak (Quercus macrocarpa). Fire was important in maintaining these ecosystems. The steeper slopes supported hardwood forests of sugar maple (Acer saccharum), American basswood (Tilia americana), and oak. These forests were sheltered from fire, and in them, windthrow and ice storms were the most important disturbances.

Most of the flatter uplands have been cleared for agriculture, mostly pastureland and dairy farming. Bottomlands have a mix of woodland and agriculture, and the steeper slopes remain forested; overall agriculture here is higher than in the rest of the Driftless Area. As such, few of the natural prairies and savannas remain, but more of the hardwood forests have been preserved. Historically, this region was used for lead and zinc mining. Platteville, WI, is the largest city here, but is quite small; besides that there are several smaller towns, but the area as a whole is rural and sparsely populated.

This area is surrounded to the north, west, and south by the Blufflands and Coulees of the Driftless Area. To the east, it is bordered by glaciated regions: over most of its length, the Rock River Drift Plain, although there are also small borders to the northeast with the Southeastern Wisconsin Savannah and Till Plain and to the southeast with the Rock River Hills.

References

1. Albert, Dennis A. "Regional landscape ecosystems of Michigan, Minnesota, and Wisconsin: a working map and classification.", General Technical Report NC-178, U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station, St. Paul, MN (1995) Web.

2. 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.

3. Omernik, J.M.; Chapman, S.S.; Lillie, R.A.; Dumke, R.T. "Level III and IV Ecoregions of Wisconsin (Poster)", (2000) Web.