||Forest Compositional Change at the Confluence of Illinois and Mississippi River. Long Term Resource Monitoring Program.
Nelson, J. C. ;
Sparks, R. E. ;
||Geological Survey, Onalaska, WI. Environmental Management Technical Center. ;Illinois Natural History Survey, Havana.;Environmental Protection Agency, Washington, DC.;Corps of Engineers, Washington, DC.
Flood plains ;
Illinois River ;
Mississippi River ;
Environmental impacts ;
Man environmental interactions ;
Flood control ;
Species diversity ;
Maple trees ;
Historical aspects ;
||Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy.
Historic and current forest survey data were used to chronicle forest compositional change at a study site located between the Illnois and Mississippi rivers. Tree species importance values (IV) indicate silver maple (Acer saccharinum L.) was a co-dominant species in 1817 (IV=16.1). However, by the time another forest survey was conducted just prior to river impoundment in 1938, silver maple had already become the most dominant species (IV=84.7). Silver maple also increased in IV during the decades following river impoundment (IV=98.2) and again following the great flood of 1993 (IV=110.0). The very successful growth and establishment of silver maple since the arrival of early EuroAmerican settlers is a strong indication that humans have altered one or more of the key natural processes that once favored a more biologically rich forest community. The diversion of Lake Michigan water into the Illinois River valley in the early 1900s and river impoundment in 1938 have probably favored more water tolerant species such as silver maple. Likewise, fire was an important disturbance mechanism affecting some presettlement floodplain plant communities, but today fire is a rare occurrence along the Illinois and Mississippi rivers. Silver maple dominance will likely continue well into the 21st century unless flooding and fire regimes are used to promote a more diverse plant community.