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Knobs-Norman Upland

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About the Knobs-Norman Upland

The Knobs-Norman Upland, sometimes referred to only as the Norman Upland, is an irregularly-shaped region that occupies a large patch in central to south-central Indiana, and then extends in a narrow, squiggly extension south into Kentucky, then curving to the east.

This region is a dissected plateau with high hills and knobs, and numerous narrow ridges and valleys, topography is often quite steep. The limit of glaciation is in the far north of this region; most of it was never glaciated. Throughout the region, a combination of loess, originated from accumulation of wind-blown dust, and sediments eroding from the steep slopes, and stream and river sediments, overlie sedimentary bedrock of siltstone, shale, and sandstone. In the south, there is also limestone dolomite, Pensylvanian sandstone, and conglomerate, and bedrock outcroppings become more common in places. Broader river valleys also have some lake sediments. Soil types vary considerably, from highly leached, calcium-poor ones, to more fertile, nutrient rich ones.

This region has a humid subtropical climate, with precipitation increasing significantly as one moves south. Throughout much of the region, precipitation averages are weakly seasonal, peaking in May, gradually declining until about August, and then declining again in December to be lowest in January and February.

This area was originally covered mostly in oak-hickory forest, with American chestnut (Castanea dentata) common. Forests of American beech (Fagus grandifolia) dominated the valleys in the north. The forest type was more varied towards the south. Mesic uplands in the south featured American beech, white oak (Quercus alba), tuliptree (Liriodendron tulipifera), sugar maple (Acer saccharum), and northern red oak (Quercus rubra). Drier upland sites were a mix of oaks and hickory, with white oak most common. Dry slopes and ridges featured Virginia pine (Pinus virginiana) and shortleaf pine (Pinus echinata), and often had grassy openings. Limestone slopes featured oak-ash forest, and floodplains supported American sweetgum (Liquidambar styraciflua) and pin oak (Quercus palustris).

This area is mostly forested, mainly due to the rugged terrain that is neither easily developed nor traversed except in the valleys. Although the American chestnuts have been eliminated from the forests by the chestnut blight, the forests here are relatively less changed than in many regions. There is a small amount of agriculture throughout, including pasture and cropland, but only in the larger valleys, and more common in the south. Agriculture here produces livestock, hay, burley tobacco, corn, and soybeans. Significant areas of agriculture have been recently abandoned. Abandoned fields initially support an early-successional community of broomsedge bluestem (Andropogon virginicus), eastern redcedar (Juniperus virginiana), and sumac (Rhus sp.), which develops into forests of eastern redcedar and black locust (Robinia pseudoacacia), which are in turn eventually replaced by the more typical forest cover of this region.

In the north, at the limit of glaciation, this region is bordered by the much flatter, heavily agricultural Loamy High Lime Till Plains. In the north, it is bordered to the east by the Pre-Wisconsinan Drift Plains, a region with highly leached glacial drift from an earlier glaciation. Over its entire length, this region is bordered to the west by the much flatter but also unglaciated Mitchell Plain. In the south, in Kentucky, this region is bordererd to the northeast and north by the Outer Bluegrass region, and to the south by the Outer Bluegrass. There is also a small, brief border to the southwest with the Crawford-Mammoth Cave Uplands, to the southeast with the Plateau Escarpment, and to the east by the Knobs-Lower Scioto Dissected Plateau.

References

1. Woods, A.J, Omernik, J.M., Brockman, C.S., Gerber, T.D., Hosteter, W.D., Azevedo, S.H. "Ecoregions of Indiana and Ohio (Poster)", US Geological Survey (1998) Web.

2. Woods, A.J., Omernik, J.M., Martin, W.H., Pond, G.J., Andrews, W.M., Call, S.M, Comstock, J.A., and Taylor, D.D. "Ecoregions of Kentucky (Poster)", U.S. Geological Survey, Reston, VA (2002) Web.