534 
modified by pasturing and are dominated by Andropogon furcatus or its 
ecological equivalents. 
The data in Figure 2 were obtained from a 220-acre field along 
the Illinois River five miles west of Morris, in Grundy county. The 
trend of associations on the unpastured portion are practically identical 
with those along the Mississippi. 
It is important to note that the data in Figure 2 also show the effect 
of grazing upon the natural prairie flora. Practically every one of 
the dominant species occurring under natural conditions is replaced by 
some other species. Scirpus fluviatilis is replaced by Typha latifolia; 
Spartina Michauxiana and Calamagrostis canadensis, partly by Carex 
and Juncus but mostly by Agrostis alba; Panicum virgatum, partly by 
Andropogon furcatus __. ...22 2-2... 22-2 ene eee eee eee aeons 3, Poa pratensis 
Spartina Michauxiana - - + 
A 
Carex vesicaria _.___ - 
Scirpus fluviatilis ------~ an re cree em eee eee ceeeneeneee =a Typha latifolia 
Unpastured Pastured 
Flood-plain and moraine 
Fic. 2. Diagram showing the successions of the plant associations on 
pastured and unpastured areas on the flood-plain of the Illinois 
River in Grundy county. The dotted lines indicate the successions 
brought about by grazing. 
Agrostis alba and partly by Poa pratensis; and Andropogon furcatus, 
entirely by Poa pratensis. Not only are these primary species destroyed 
by grazing, but practically all of the secondary species are likewise 
eliminated. It may readily be seen that areas not subjected to intense 
grazing or areas that had been pastured in the past and then allowed 
‘ 
