Studies in Prairie and Woodland 



15 



contrasted in figure 7 in which the xerophilous nature of the 

 prairie soil is again conspicuous. 



In figure 8 the range of moisture content for the three stations 

 at a depth of 12-24 inches indicates that at this depth there is not 

 so great a divergence as in the shallower levels. Even at this depth, 

 however, the prairie is still the driest habitat. Determinations at 

 still lower levels, as 3-4 ft. and 4-5 ft. show that this relation still 



Figure 8. The march of soil moisture in the three stations at Lincoln, 

 1917, at 12-24 inches. 



holds true and that in general there is a more rapidly diminishing 

 water residue in prairie soils at depths of 4 and 5 ft. than in either 

 of the two other stations under investigation. 



These soil moisture studies, now covering three entire seasons 

 of vegetational activity, abundantly prove the importance of seil 

 moisture as a factor in plant succession as between prairies on 

 one hand and forest on the other. All of the data from the three 

 summers' work are in agreement in that the percentages of avail- 



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