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

Ecoregion 40a : Loess Flats and Till Plains

Ecoregion Map

Ecoregion Characteristics

Landform Description
Irregular plains, open low hills. Elevation 700-1200 ft.
Surficial Materials
Moderate loess over loamy till and clay loam till.
Soils
Mollisols (Argiudolls){Shelby-Grundy-Haig, Shelby-Seymour-Edina}
Climate
Annual precipitation 32-36 in. Freeze free: 170-180 days
Potential Vegetation
Mosaic of bluestem prairie and oak-hickory forest
Predominant Land Use
Cropland and pasture, deciduous forest
Deep to moderate loess deposits over glacial till and dark, shallow soils are characteristic of the Loess Flats and Till Plains ecoregion. Loess deposits generally increase to the south, especially near the Missouri River. Several streams have headwaters in this region, and the topography varies from flat to moderately hilly. Valley sides are not steep, with slopes generally less than 10%. The Chariton River area is a more dissected and hilly area within this region. It lacks glacial till in many places and has a greater drainage density and more woody vegetation in stream reaches than in other parts of the ecoregion. Natural wetlands occur along the Grand River and several other rivers in the region. Soils are inherently fertile, but use can be limited due to severe erosion. Land use includes areas of cropland, pasture in the valleys and on upland slopes, and bands of woodland. Corn and soybeans are the major crops.