r 

 I 



1907] YOUNG— FOREST FORMATIONS OF COLORADO 347 



its lower part, at an approximate altitude of 3150^. The slope was 

 gentle, the exposure southeast* The second point, which I shall 

 designate as Station B, was in this same canon at an approximate 

 altitude of 3300^, on a steep south slope. 



Temperatures 



Observations —22.$^^ — ii.25«°» o«n* 4-7.5*"* -f-o.p* 



Station A* . . June 20, 7 p. m. 4?6 8?7 8°7 



June 21, 6 A, M. 3?2 2?5 2?2 



Station B September 22, 4 p. m. 7?25 8?25 14775 



* The observations at this station were made while many snowdrifts still lay in the forest. 



ri i ; 



i J I ; . Relative hiimidity 



fl Observations +7.5^™ +0.9'" 



Station A June 20, 7 p. m. 40 per cent. 40 per cent 



lJ June 21, 6 a. m. 100 per cent. 96 per cent, 



Water content 



I 



Observations 11.25*='^ 22.5—11.25*^'" 



Station A .... June 20, 7 p. M. 227 per cent. per cent. 



Station B September 22, 4 p. m. 20.9 per cent. 20.9 per cent. 



Light value 

 For light value, refer to Apinus formation. 



(8) THE ASPEN SOCIETY {fig. g) 



I have already stated my reasons for not considering the groves of 

 aspens as a distinct formation. They have an mdividuality as a 

 society, however, among the other forest formations which entitles 

 them to separate consideration at this point. 



This society occurs within the limits of the other formations. It 

 usually occurs as a distinct society, but occasionally loses its individu- 

 ality, mingling intimately with the trees of the other forests. It is 

 distributed throughout the mountains from 1800"^ to 3150™, being 

 confined in the lower part of its range to the north slopes, but in the 

 higher mountains being distributed indifferently over both north and 

 south slopes. It may occur either as a scattered grove of trees, exer- 

 cising but little if any control upon the lower layers of the vegetation; 

 or it may form a forest with the trees growing within a few feet of 

 each other, in which case it does exercise a decided control upon the 

 lower layers. 



The physical conditions in such a forest are intermediate between 

 those in the dense spruce and fir timber of the canon bottoms and 



