PLANT SUCCESSION AND BANGE MANAGEMENT. 
9 
The rather strict line of demarcation in the habitat requirements 
of the two forms may be explained in two ways — (1) by the differ- 
ence in the distribution of the available moisture of the soil and (2) 
by the depth to which the roots of the two grass forms extend. 
* 
Fig. 2. — Relative height and character of root system of typical wheat grasses of the 
bunched and of the turfed habit of growth. A, Blue bunch wheat grass (Agropyron 
spicatum) : Ad, Small wheat grass (Agropyron dasystachyum) ; AT, Slender wheat 
grass (Agropyron tenerum). 
By far the greater portion of the absorbing surface of small wheat 
grass is confined to the upper 8 inches of soil, the average maximum 
depth of individual roots not exceeding about 15 inches (fig. 2). 
Because of the densely matted sod on areas where small wheat grass 
