ON THE FORESTS OF LA SALLE COUNTY, 

 ILLINOIS. 



Geo. D. Fuller and P. D. Strausbaugh, University of 



Chicago^ 



The forests of La Salle County are of particular inter- 

 est not so much on account of their economic value as be- 

 cause of their intimate relation to soil diversity and 

 stream development. The soils have been carefully sur- 

 veyed, classified and mapped by Hopkins and Mosier^ and 

 it is largely upon their admirable reports and soil maps 

 that the present forest survey is based. 



SOIL CONDITIONS. 



The diversity of soil is due to the situation of the county 

 in the north-central part of the area included in the early 

 Wisconsin glaciation. Five distinct classes are recog- 

 nized, as follows : 



1. Upland prairie soil with gently rolling surface, the 

 relief often being too slight for good natural drainage. — To 

 the depth of 3 to 5 feet this soil consists of loam formed 

 principally from wind blown material. With this is 

 mingled more or less silt and an average of 6 per cent of 

 organic matter resulting from the decay of the roots and 

 stems of the grasses which have been the principal vegeta- 

 tion. The soil varies in color from brown to black and 

 covers about 82 per cent of the 1157 square miles which 

 are contained within the limits of the county. The sub- 

 soil is usually a yellow clayey silt, in places mingled with 

 glacial drift. A prairie vegetation of grasses and herbace- 

 ous plants seems to have been the original cover of this 

 soil, at least within all the areas included in this report, 

 but at present cultivated grains and grasses have very 

 completely replaced the plants of the original prairie turf. 



1 Hopkins, Cyril G.. Mosier, J. G. et al. La Salle County soils. Univ. 111. 

 Agri. Exper. Station. Soil Report No. 5 : pp. 45 pis. 5. maps 4. 1913. 



246 



