August, 1955 



EvERS: Hii.i. Prairies of Illinois 



.?95 



-tretches of bluff frontage, totaling 25 to 

 .>0 miles, remain hill prairie or are in pari 

 hill prairie. Possibly as much as three 

 times this extent, 75 to 90 miles, or about 

 one-eighth of the blufif frontage on the 

 east sides of the major stream valleys, was 

 prairie in the early nineteenth century, but 

 was converted to pasture or otherwise dis- 

 turbed by the activities of man. The bases 

 for such an estimation are the few scat- 

 tered prairie plants along stretches of 

 bluffs now occupied principally by blue- 

 grass and numerous pasture weeds. Such 

 stretches of bluffs are common along the 

 Mississippi River in Jo Daviess Count\. 

 Doubtless these bluffs were prairie cov- 

 ered in the not distant past. 



Hill prairies have been surprisingly 

 successful in resisting destruction by the 

 grazing of domestic animals and by some 

 of the activities of man. There are no 

 records to show how heavily these prairies 

 were grazed by bison before the arrival of 

 >vhite men in Illinois. It is possible that 

 bison grazed many hill prairies, but that 

 they failed to reach some that were hid- 

 den by surrounding dense forest. Whether 

 or not pastured hill prairies observed for 

 this report are being reduced by overpas- 

 turing is not \et evident. Goat pasturing 

 in one site along the bluffs of the Illinois 

 River south of Rosedale caused complete 

 destruction of the prairie, leaving only 

 bare loess on the slope. The spread of 

 residential and industrial areas has de- 

 stroyed some of the hill prairies. On the 

 other hand, it is evident that fire has not 

 destroyed them ; seemingly, it has per- 

 mitted an earlier and more tender growth 

 of grass. 



What is the probability that hill prairies 

 are now being invaded by forests? Some 

 of the most typical hill prairies are located 

 on brow slopes where the cliffs are so high 

 that they extend above the trees that grow- 

 on the toe slopes : without the shade of 

 the trees, the brow slopes, especially those 

 facing southwest, are exposed to the heat 

 of the sun and to the prevailing winds of 

 summer and are thus too xeric for growth 

 of mesophytic forest and will probably 

 remain 'prairie. The bluff coves, which 

 serve as drainageways on the slopes, are 

 more mesic and, in places, support mixed 

 forest. Such forested coves contain tree 



species that are found in the forests of the 

 basal slopes, ^r^f the slopes of the tributary 

 valle\s parallel to the main valleys, or of 

 the uplands. Where the bluff's are low, or 

 in the few places where the ascent from 

 Hoodplain to upland is continuously of 

 low gradient, trees have long shaded the 

 upper slopes and greatly reduced wind 

 movement. In such situations, forests 

 have been established over entire slopes. 



In years of abundant rainfall, forest 

 seedlings become established on prairie 

 spurs, only to die in years of less abun- 

 dant rainfall or in periods of successive 

 dry \ears, as of the 1930's. Dwarfed 

 trees, as well as dead sumacs and red ce- 

 dars, are reminders of dry years and a 

 contest between forest and prairie. It 

 thus seems probable that a shifting equi- 

 librium was long ago reached between 

 prairie and forest, especially on bluffs 

 with high cliffs. As long as the present 

 topography and climate persist, such hill 

 prairies will remain approximately as the\ 

 are. 



Delimitation and description of the 

 actual stages of succession within hill prai- 

 rie areas cannot be made now, but must 

 await the advent of interested botanists 

 of the future. In the interim, it is im- 

 portant that botanists continue the stud)' 

 of these sites and publish the results of 

 their studies. From such studies, bota- 

 nists will be able to trace actual, not hypo- 

 thetical, paths of succession and also de- 

 duce with a greater amount of accuracy 

 the past vegetational history. 



.ANNOTATED LIST OF HILL 

 PRAIRIES 



The following list of Illinois hill prai- 

 ries includes only those prairies which the 

 writer visited during the field work for 

 this study. The name given to each of 

 the prairies was derived from one of sev- 

 eral sources — the name of the landowner, 

 or of the tenant, or of the farm on which 

 the prairie was found ; the name of that 

 stretch of bluff' occupied by the prairie; 

 or the name of some nearby landmark or 

 community as applied kxrally or found on 

 a quadrangle of the United States Geo- 

 logical Survey topographic map. [voca- 

 tion of each prairie is gi\en according to 



