Studies in Prairie and Woodland 27 



growth at Peru is shown in the much more luxuriant develop- 

 ment of many of the prairie species growing at both of our prairie 

 stations. For example, at Peru Andropogon furcatus extends to 

 the very crests of the steepest ridges where it grows to a height 

 of 5 or 6 feet, while its roots extend to a depth of over 9 feet into 

 the moist loess soil. The excellent growth made by other prairie 

 species even upon the drier ridges indicates conditions very 

 favorable for chaparral growth, and indeed, thickets of Corylus 

 americana, Rhus glabra, and Symphoricarpos spp. are very fre- 

 quent in the grassland. Nor is it uncommon to find the seedlings 

 of elm and oak near the edges of these thickets. Except for fires, 

 grazing or other disturbance much of this subclimax grassland 

 would undoubtedly pass through a scrub stage in succession and 

 culminate in forest while Still other extensive areas would prob- 

 ably remain covered with chaparral. It will be shown that habitat 

 conditions are actually much less xerophilous as regards both 

 moisture of the air and soil than at the Lincoln station. While 

 the precipitation at Lincoln is only 28 inches, that at Peru is 34 

 inches. 



While the flood plain forest station at Lincoln represents, as 

 already pointed out, the " bur oak-elm-walnut formation " of 

 Clements and Pound, the forests about Peru are of the more 

 mesophytic " red oak-hickory type." Quercus rubra, Hicoria 

 ovata, Ulmns americana, Fraxiniis lanceolata, Juglans nigra and 

 Tilia americana are all dominants in the best developed forests, 

 although many other trees play important roles in the various 

 stages of succession. Among those occupying the drier soils and 

 with the chaparral, under favorable conditions gradually en- 

 croaching upon the prairie, are such species as Quercus macro- 

 car pa and Quercus velutina. On the other extreme, such species 

 as Platanus occidentalis, Gleditsia triacanthos and Gymnocladus 

 dioicus occupy the rich moist soils of the ravines as well as the 

 slopes of the blufifs. Indeed a large number of eastern trees of 

 considerable frequence but limited abundance are striking fea- 

 tures of these rich woodlands. Many of these, having entered the 

 state from the southeast along the Missouri, soon reach their 

 westward limit and drop out as one proceeds northward or west- 



33 



