Pre-settlement Vegetation of Greene, Jersey and Macoupin Counties along the Prairie/Forest Border in Illinois

The US Federal Government established the Public Land Survey (PLS) to survey federal land before sale to settlers in the early 1800’s. We used a Geographic Information System (GIS) and the PLS to explore the relationship among forests, fire frequency, topography, and soils in Greene, Jersey and Macoupin Counties in Illinois. The PLS data was digitized from microfiche copies of the survey in the Lovejoy Library at Southern Illinois University Edwardsville. The floodplains along the Illinois River supported a fire-intolerant forest of Salix sp., Populus deltoides, Acer spp., and Fraxinus spp. The floodplain is bordered by a line of bluffs which forms a region of broken topography supporting moderately fire tolerant species on alfisols. To the East is a region of mixed prairie and forest. The prairie was on flat mollisols where it was intermixed with the forest on and hillier slopes and alfisols. The forest areas supported highly fire tolerant forest trees with large diameters at large distances from survey points. Non-Metric Multidimensional scaling reveals a close relationship among topography, vegetation and soils. Forests were on hilly land. Prairies were located on level uplands where there were no firebreaks. Floodplains are just as level as prairies. They are also located on mollisols adjacent to the river. They are protected from fire by sloughs, swamps and lakes. The results of our study support the conclusion that topography and moisture is an important control on the geographical distribution of vegetation in the study area. These factors likely operated by controlling fire frequency