Iowa DNR
River & Stream Biological Monitoring
Fish and Benthic Macroinvertebrate Surveys
Physical Habitat Assessments

Ecoregion 52b : Paleozoic Plateau (Driftless Area)

Ecoregion Map
Ecoregion Characteristics
Landform Description
Open hills, irregular plains. Elevation 700-1200 ft.
Surficial Materials
Thin loess and patches of drift over bedrock.
Alfisols (Hapludalfs) {Fayette-Dubuque-Stonyland}
Annual precipitation 32-34 in. Freeze free: 140-155 days.
Potential Vegetation
Maple-basswood forest
Predominant Land Use
Cropland and pasture, deciduous forest
The bedrock-dominated terrain of the Paleozoic Plateau ecoregion is strikingly different from the rest of Iowa. Steep slopes and bluffs, higher relief, sedimentary rock outcrops, dense forests, and unique boreal microhabitats differentiate this ecoregion from the Western Cornbelt Plains to the west. The Silurian Escarpment, a prominent physiographic feature that helps define the southern and western boundary this ecoregion, separates the mostly cropland area of the west from the mixed land use of the Driftless Area. Dissolution of the limestone and dolomite rocks results in karst features such as sinkholes, caves, and springs, and makes groundwater vulnerable to contamination. The streams in the Iowa portion of this region occupy entrenched valleys, and have cool waters with high gradients flowing over rocky substrates. The fish communities found here reflect this preference for cool clear water with relative consistency of flow.