Annual precipitation 34-36 in. Freeze free: 165-175 days.
Predominant Land Use
Cropland, deciduous forest, forested wetlands
A small portion of the Upper Mississippi Alluvial Plain is found in Missouri, with most of the ecoregion occurring in Illinois and Iowa. The smooth to irregular alluvial plain and the river channel have undergone drastic changes in the last 100 years. Large reaches of the river have been channelized and numerous low dams with locks have been constructed upstream of St. Louis. The potential natural vegetation of oak-hickory forest, northern floodplain forest, and tallgrass prairie has all but been replaced by agriculture. Soils are deep, silty, and clayey alluvium and support extensive cropland. The Mississippi River is generally less turbid than in the Missouri portions of the region.