Southeastern Washington and Adjacent Idaho. 25 



But the soil water reached its non-available point somewhat ear- 

 lier. However, the Agropyron consociation was the first to ex- 

 haust its available supply. 



The enormous strain brought to bear upon these early develop- 

 mental plant communities may be realized when it is noted that 

 after the water of the first 10 inches of soil became unavailable, 

 the evaporation throughout the remainder of the season was very 

 high. Two methods of meeting these adverse conditions are em- 

 ployed by plants of these communities. They either mature early 

 and become dormant upon the approach of drought, or develop 

 very extensive root-systems. But these had best be discussed 

 under structure and development of vegetation. 



The mechanical analyses of these soils show that those of the 

 Agropyron consociation are of a coarser texture than those of 

 the Festuca consociation (Table II). Likewise the humus and 

 volatile matter were found to be lower in the former. 



TABLE II 



MECHANICAL ANALYSES OF SOILS FROM VARIOUS PLANT COMMUNITIES IN 

 SOUTHEASTERN WASHINGTON AND ADJACENT IDAHO 



