SOIL TEXTURE AND FOREST STRATA RELATIONSHIPS OF THE CENTRAL FLOODPLAIN FOREST, 
LOWER KASKASKIA RIVER, ILLINOIS

Susan P. Romano1, James J. Zaczek2, Karl Williard2, David J. Gibson3, Loretta L. 
Battaglia3, and Sara G. Baer3.
1Department of Biological Sciences, Western Illinois University, Macomb, 
Illinois  61455. 2Department of Forestry, Southern Illinois University, 
Carbondale, Illinois  62901. 3Department of Plant Biology, Southern Illinois 
University, Carbondale, Illinois.

Soil texture has been shown to be an important factor in forest community 
development for the silver maple – American elm (Acer saccharinum – Ulmus 
americana) central floodplain forest.  A southern Illinois floodplain study 
suggested that inundation, soil drainage, and aeration were the most important 
factors in floodplain forest community development. Other studies indicated that 
soil may be the most important environmental factor for the overstory species, 
and less important in other forest strata.  The purpose of this study is to 
determine if the proportions of sand, silt, and clay are related to species 
importance in the floodplain forest community of the Lower Kaskaskia River, a 
tributary of the Mississippi River, located in Illinois east of St. Louis, 
Missouri.

Three sites were sampled near Posey, Venedy, and Fayetteville, Illinois.  
Regressions of importance values of tree species in overstory positions and 
percent sand indicated that A. saccharinum decreased in importance when the sand 
content of the soil increased at Posey (p<0.001, r2=0.379) and Venedy (p=0.031, 
r2=0.187).  At Posey, greater sand content was also related to a decrease in the 
importance of Acer negundo (p=0.01, r2=0.227) and Fraxinus pennsylvanica 
(p<0.001, r2=0.438).  Only one species increased in importance with increased 
sand, Celtis occidentalis (p=0.025, r2=0.193), and only at Fayetteville. Soils 
with a greater silt component at Posey were significantly related to an increase 
in the importance of A. negundo (p=0.010, r2=0.227), and F. pennsylvanica 
(p=0.006, r2=0.246) in the overstory.  Greater amounts of clay increased the 
importance of A. saccharinum (p<0.001, r2=0.411) and F. pennsylvanica (p=0.001, 
r2=0.338) at Posey, and U. Americana (p=0.045, r2=0.186) at Venedy.  At the 
Fayetteville site, increasing clay in the soil was significantly related to the 
increase in importance of A. negundo (p=0.022, r2=0.186) in the overstory. The 
importance values of tree species in understory positions were only occasionally 
related to soil texture content.

Keywords:  Kaskaskia River, Acer saccharinum, Ulmus americana, soil texture, 
floodplain.