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G. A. PEARSON 



The forest is typical of burned areas at this altitude. It is 

 probably more than 25 years since the last fire occurred. Aspen 

 thickets cover about two-thirds of the area and are separated by 

 openings varying in diameter from 20 to 100 meters. Douglas 

 fir, western yellow pine and limber pine occur singly or in groups 

 in sufficient numbers to seed up the area, but nevertheless repro- 

 duction of these species is very meagre. Herbaceous growth 



Fig. 1. A typical opening in tin aspen stand. A Piche evaporinieter, anemom- 

 eter, and thermograph are shown in the foreground. 



is fairly abundant. Among the more conspicuous plants are 

 Frasera scahra, Pteridium aquilinum, and Verbascum sp. Shrubby 

 undergrowth is practically limited to occasional clumps of elder. 



In selecting the planting plots for a comparison of results in 

 aspen thickets and openings, particular pains were taken to 

 secure uniformity with respect to all physical conditions except- 



