FORESTRY SURVEY 243 



The presence of the piu oak flats scattered about on the 

 interstream prairie uplands presents an interesting 

 problem. If these small pin oak groves are of recent 

 origin, then the pin oaks and shingle oaks must be more 

 mobile than has been realized. If they are not more 

 mobile than other oaks, then it is probable that these pin 

 oak groves are relics, in the wetter situations, of forest 

 areas elsewhere replaced bv prairie as a consequence of 

 fire. Evidence for both sides of this question is at hand. 

 These two oaks come up freely along fence-rows and 

 ditches along with plainly mobile species, such as elm and 

 choke-cherry. Probably they are more mobile than oaks 

 with larger acorns and may easily be carried by certain 

 birds. Probably, also, they may be mobile only for rela- 

 tively short distances, for hardly a spot in the inter- 

 stream uplands is more than a mile or half-mile from a 

 grove or line of trees or from the forest system of the 

 valleys. The absence of pin oaks and the presence of cot- 

 tonwoods on at least part of the more extensive prairie 

 upland of the western border bears out the notion of their 

 limited mobility^ and indicates a difference from the 

 smaller inter-stream uplands. Possibly the inter-stream 

 uplands may once have been generally forested, while the 

 western border remained treeless and tire-swept. If this 

 is true, then a careful comparison of the remaining prairie 

 floras of the two areas may reveal herbaceous relics of 

 forest over the inter-stream uplands. Such forest herbs 

 do persist among the prairie herbs in parts of Coles 

 county, just to the north. 



Furthermore, evidence is common both that forest has 

 succeeded prairie and that prairie has replaced forest 

 within even the last sixty years. If such radical changes 

 can take place within so short a time, it need not surprise 

 one that inference should call for perhaps a succession of 

 fluctuations between prairie and forest. 



' Since this was written, further evidence appears in the discovery of a 

 single young plant of shingle oak in an elm-hackberry grove. Obviouslv the 

 shingle oak did not get in until the more mobile trees" were established. " This 

 grove, which is six miles northwest of Charleston, is small and probablv of recent 

 origin. It is about two miles distant from the nearest tongue of ordinarv forest, 

 which follows a small stream. Another isolated elm-hackberrv forest known as 

 Round Grove, two or three miles east of the northeast corner of Cumberland 

 county, is larger and older and contains a considerable number of fair sized 

 shingle oaks, which, however, seem to be younger than the large elms and hack- 

 berries. There are other groves with no oaks at all. Shingle oak thus seems to 

 be much less mobile than elms and hackberries. and much more mobile than other 

 oaks and hickories. Pin oak is usually found with shingle oak in the inter-stream 

 uplands of Cumberland county, and is probably of the same order of mobility. 



