30 



BULLETIN *700, U. S. DEPARTMENT OF AGRICULTURE. 



The smallest number of heat units above 40° F. and the largest 

 number below 40° F., as shown in figure 4, occur in June and Sep- 

 tember, near the beginning and ending of growth in the two lower 

 types represented.^ One of the most significant facts brought out 

 in Table 9 is the absence of temperatures below 40° F. for Auo-ust 



JJU 





1916 1916 



RABBIT BRUSH 



































1 



1 





i 



1916 

 OAK- BRUSH 



1915 





1916 

 ASPEN-FIR 



1915 1916 



SPRUCE-FIR 

 MONTHLY AND. ANNUAL PRECIPITATION 





JUNE 



[JULY AUSUST 



SEPT. 



\rOTAL 







RABBIT BRUSH 

 OAK-BRUSH 

 ASPEN-FIR 

 SPRUCE-FIR 



1 

 1 





SJ* 





ssr 



- 







■■ 







' 



MONTHLY PRECIPITATION DURING BROWING SEASON 1916 

 Fig. 14. — Precipitation record, 1915-1916. 



in the oak-brush type. All types considered, July and August are 

 the most favorable months for growth, in so far as it is determined 

 by temperature. 



^ Growth begins in the oak-brush type approximately June 1. In the aspen-fir type 

 the leaves begin to unfold about two weeks later. In the spruce-fir type growth begins 

 between 3 and 4 weeks later than in the oak-brush type. 



