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Western Pennyroyal Karst Plain

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About the Western Pennyroyal Karst Plain

The Western Pennyroyal Karst Plain is a large, flat region located mostly in southern Kentucky, extending slightly into northern Tennessee. This area is presently heavily utilized for agriculture.

This region is underlain almost entirely with limestone, mostly covered in thin layers of loess, and in a few areas, calcareous shale. Soils here tend to be fertile and nutrient-rich, but quick to dry out. There is karst topography, with sinkholes, springs, sinking streams, dry valleys, and extensive underground drainage. Surface stream density is low, and most upland surface streams are intermittent or ephemeral. Larger, perennial streams and rivers are fed by groundwater, and tend to be cool.

This area was originally covered mostly by a mosaic of bluestem prairie and oak-hickory forest; there were some swamps in areas where the ground had collapsed into sinkholes. The prairies here were some of the largest natural grasslands in the broader region. Mesic sites supported a mixed deciduous forest, with American beech (Fagus grandifolia) and various oaks. Uplands were dominated by white oak (Quercus alba), along with American beech, white oak (Quercus alba), tuliptree (Liriodendron tulipifera), and pignut hickory (Carya glabra).

Nowadays this area is mostly cleared and utilized for cropland and pastureland, and there are also urban areas and military reservations (particularly Fort Campbell), and some oil and gas extraction. Forest is mostly limited to the most poorly-drained sites, but there are scattered woodlots and small forest fragments throughout. The region produces mostly tobacco and livestock, along with some corn, soybeans, and small grains. Agricultural runoff has degraded waterways with high nitrate levels. This area is moderately populous; Bowling Green, KY is the largest city, followed by Hopkinsville, KY; there are numerous smaller towns and some suburbanization.

Little of the original oak-hickory forest remains. Recently-abandoned fields support a mix of broomsedge bluestem (Andropogon virginicus) and little bluestem (Schizachyrium scoparium). These develop into a mix of broomsedge and sumac (Rhus sp.), which in turn develops into forests of eastern redcedar (Juniperus virginiana) and black locust (Robinia pseudoacacia). There are a few areas of protected bluestem prairie at nature preserves.

This region is bordered to the north by the more rugged, upland Crawford-Mammoth Cave Uplands, to the southwest by the Western Highland Rim, to the east and southeast by the Eastern Highland Rim, and in a very small border to the south with the Outer Nashville Basin.

References

1. 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.

2. Griffith, G.E.; Omernik, J.M.; and Azevedo, S.H. "Ecoregions of Tennessee (Poster)", U.S. Geological Survey, Reston, VA (1998) Web.