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Government Land Office (GLO) survey records were used to reconstruct the presettlement floodplain landscape at the confluence of the Illinois and Mississippi rivers. Presettlement prairie and forest land covers were determined by digitizing GLO plat maps using a computerized geographic information system (GIS). A case history of land cover change was determined by comparing this presettlement map to GIS land cover maps for 1903, 1935, and 1975. Data from witness trees and current forest samples were used to compare presettlement and present forest composition and structure. Results indicate that approximately 56% of the presettlement floodplain was forested, while 41% was prairie. The presettlement forests were...
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Data from the original General Land Office (GLO) survey (1815) of the 5th Principal Meridian were used to evaluate presettlement vegetation patterns in eastern Missouri and Arkansas. Data were divided into three physiographic sections: Mississippi Alluvial Plain, Ozark Plateau, and Dissected Till Plain. Distances to bearing trees and diameters were used to estimate tree density and to evaluate the relative structure and composition of presettlement vegetation. The Mississippi Alluvial Plain was the most densely timbered physiographic section. White oak (Quercus alba), black oak (Q. velutina), sweet gum (Liquidambar styraciflua), and hickory (Carya spp.) had high importance values. Significantly lower tree densities...
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Distribution and frequency of submersed aquatic vegetation in the Upper Mississippi River System are monitored as part of the Long Term Resource Monitoring Program. This report summarizes results of sampling aquatic vegetation along fixed transects in Navigation Pools 4, 8, 13, and 26 in the Upper Mississippi River and La Grange Pool in the Illinois River in 1996. Plants were sampled at regular intervals along fixed transects using a modified rake technique. Sampling was conducted twice during the growing season (spring and summer). Twenty-four submersed and rooted floating-leaved species were found. Most species were found in Pools 4, 8, and 13. Pool 26 had the fewest (3) number of species and Pool 4 had the greatest...
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The natural Upper Mississippi River (UMR) and its tributaries flowed and meandered freely across large floodplain landscapes. Processes such as flooding, erosion, and sedimentation were powerful natural forces that shaped and maintained some floodplain forest communities. Beginning in the early nineteenth century, the UMR and its floodplain have been modified by navigation structures and agriculture. As a consequence of human modifications, a large portion of the UMR floodplain is no longer periodically inundated and the hydrologic patterns in the river, as well as on the floodplain, have changed. In general, agriculture and urban development have greatly reduced floodplain forest acres, especially in river reaches...
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