FOREST TYPES IX CENTRAL ROCKY MOUNTAINS. 



39 



These facts evidently do not apply to sites of decided northerly 

 or southerly aspect, where the amount of insolation received may 

 appreciably affect the local mean temperature. (Compare Stations 

 3A and 3G, 2A and 2G, in Table 9.) 



Temperatures at various elevations in the Pikes Peak region. — The 

 control station in this project, the Weather Bureau station at Colo- 

 rado Springs, the Forest Service station at the Monument Nursery, 

 the Weather Bureau cooperative station at Lake Moraine, and the 

 special station at timber line, operated for 17 months, comprise an 



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JAN. FEB. MAR. APR. MAY JUNE JULY AUG. 



OCT 



NOV. DEC. 



Fig. 2.— Monthly mean uemperature for different e.evations in the Pikes Peak region series. 



altitudinal series (Table 8) from which a very definite idea may be 

 obtained of the primary cause of forest zonation, if, indeed, tempera- 

 ture is a cause, as it appears to be. 



In Table 8 the mean temperature of each of these stations, by 

 months, is expressed by the difference between the temperature of the 

 station in question and that of the control station, for the period 

 indicated in column 4. The mean temperatures at the control sta- 

 tion for the period up to April, 1921, are given in the center of the 

 table, so that those for any other station may readily be computed 

 to the same basis. In Figure 2 the absolute temperatures computed 

 in this manner are shown. 



