Southeastern Washington and Adjacent Idaho. 31 



here, as at Colfax, the available water was exhausted somewhat 

 earlier than in the summer of 1913. On July 14, 1914, and when 

 the available moisture of the surface ten inches had been depleted 

 in all habitats, samples were taken as usual at a depth of two 

 feet in the prairie and fir-tamarack communities respectively. 

 These showed that practically no water was available even at this 

 depth. 



The relation of soil moisture to plant succession was likewise 

 determined at the stations already described near Viola, Idaho, 

 during 1913. The results are plotted in Fig. 8. These graphs 



FIG. 8. Graphs showing the march of soil water to a depth of 10 inches 

 in plant communities at Viola, Idaho. 



appear somewhat different from those at Kamiak. This is due 

 in part to the longer intervals between readings. Also the fir- 

 tamarack station was somewhat less mesophytic than that at 

 Kamiak, but like the former, was covered with a second growth 

 of Douglas fir and tamarack. Likewise, the pine community was 

 of a much more open type than that on the sheltered base of 

 Kamiak Mountain. The water holding capacity of the soil at 



