CLIMATE AND PLANT GROWTH. 



33 



Table 10. — Monthly wind movement in the spruce-fir and in the aspen-fir type 



station. 



Month. 



Year. 



Aspen-fir. 



Spruce-fir. 





/1915. . . 

 \1916... 

 /1915... 

 \1916... 

 /1915... 

 \1916... 

 /1915... 

 \1916... 



/1915. . . 

 \1916. . . 



Miles. 

 3,081 

 3,020 

 3,055 

 3,697 

 3,339 

 3,198 

 3,008 

 3,080 



Miles. 

 6,501 



July 



7,119 



6,807 





5,505 

 4,836 





5,116 

 7,632 





6,873 



Total 



12, 483 

 12, 995 



25, 776 





24, 613 



Fig. 16.- 



-View of atmometers and evaporating pan used in measuring the evaporating 

 power of the air. 



The above figures show that the wind movement during the 

 growing seasons of 1915 and 1916 was greater by approximately 100 

 per cent in the heart of the spruce-fir type than in the aspen-fir asso- 

 ciation 1,300 feet lower. In summarizing the wind movement by 

 10-day periods the velocity is found to exceed by 200 per cent that in 

 the aspen-fir type for certain periods. Obviously, the gales over the 

 elevated, sparsely vegetated plateaus have a profound effect on the 

 evaporation and to some extent at least on the transpiration rate of 

 the vegetation. 



56866°— 18— Bull. 700 3 



