12 



The Botanical Survey of Nebraska 



corded on the graph show also that there was little moisture avail- 

 able at the 3-4 ft. and 4-5 ft. levels in this prairie station. 



On the whole our data indicate that the prairie was a consider- 

 ably drier habitat, in so far as soil moisture is concerned, during 

 the summer of 1917 than in 1916. The after-summer period was 



APRIL 



AAAY 



June: 



OULY 



AUGUST 



25 



20 



15 



yo 



y 



/ 



^ 



/" 





/ 



/ 



y 



/ 



X 



<y^ 



^y 



12-24 



^ \ 

 \ 

 \ 



V 



\ 



\ 

 \ 



/ 



\ 



/ 



0-12 



\ \ 



/ ^ 



/ 



/ 



\ \\ 



17 



A 



^y 



\ 



\ 



V 



Figure 5. Soil moisture at 0-6 in., 6-12 in., 12-24 in. in the prairie station, 



Lincoln, 1917. 



particularly dry in all three of the stations and this condition was 

 strikingly indicated by the relatively early maturation of aestival 

 and serotinal species, especially upon the prairie. 



Figure 6 shows the march of soil moisture at the 0-6 in. depth 

 in all three of the stations for 1917. The wilting coefficients of 

 the soils for the different stations are indicated by the horizontal 

 lines. The xerophytism of the prairies is nicely illustrated in this 



18 



