30 BIG SPRING PRAIRIE. 



This tree is situated in a low woods, adjoining the prai- 

 rie and at the junction of a shallow drainage valley 

 from West Ridge. It is about two rods distant from 

 the ditch draining southern part of prairie. The tree 

 is 59 inches in circumference just above the exposed 

 roots. The amount of settling indicated is about 2^ 

 feet. Figure 3 shows another tree 36 inches in cir- 

 cumference. It is situated in same woods, but a short 

 distance up the slope of this natural drainage valley. 

 The amount of settling at this point is about 24 inches. 

 Considerable of this settling was due to the last deepen- 

 ing of the outlet of this prairie ditch in 1897. 



Several wooded areas of this prairie, whose princi- 

 pal genera are Ulmus, Fraxinus, and Acer exhibit a like 

 tendency to prominent or exposed roots. Whenever 

 the roots of trees are imbedded in a solid clay subsoil, 

 and the soil settles, it will leave the upper roots ex- 

 posed as illustrated in figures 2 and 3. Thus, in part, 

 we can read the history of the past of such areas by 

 the present conditions. 



Since the settling of the soil tends to cause a rever- 

 sion of the plant societies, it is of considerable interest 

 to further investigate the subject of drainage and its ef- 

 fects; especially as prairie fires which burn the soil as 

 well as the vegetation upon it are, upon this prairie, a 

 direct result of artificial drainage. Before artificial 

 drainage was introduced, the burning of the soil did 

 not occur, as the muck was surcharged with water. 

 The enclosing ridges and the solid rock bed underlying 

 the prairie renders this a peculiar kind of prairie. The 

 edge of the prairie is lined by a number of springs, the 

 natural outlets of the subterranean drainage of the 

 ridges; the rock strata of these ridges, as before ex- 

 plained, dipping toward the low ground and hence in 

 this region toward the prairie, the subterranean water 

 must rise in prairie muck until it rises sufficiently high 

 to be drained off by the prairie ditches. For this reason. 



