29 



a coast fir TO feet high would measure only 9 inches in diameter and 

 would yield but 50 board feet. In pure forests the Rocky Mountain 

 form does not produce such dense stands nor clean, straight boles as 

 the coast fir, but because of its slower growth it forms for a given 

 average diameter a much more open and stunted stand, and for a 

 given age a forest of much smaller trees than does the coast fir. 



RATE OF GROWTH. 



The coast form greatly exceeds the mountain form in rapidity of 

 height growth. In Europe it has exhibited a more rapid growth in 

 favorable situations than any of the native coniferous timber trees. 

 It attains this rapidity both by the actual rate at which it grows and 

 by the long duration of the growth period, due to its characteristic 

 of putting out a second " leader," or terminal shoot, in the fall, after 

 the growth of the mountain form has ceased for the year. The sus- 

 ceptibility of the unripened green shoots to early frosts, which in 

 exposed situations are very apt to kill back this portion of the 

 growth, has led to a considerable difference of opinion among the 

 European foresters who advocate the extensive planting of Douglas 

 fir as to whether the rapid-growing coast form or the slow-grow- 

 ing but more hardy Rocky Mountain form should be used. The con- 

 sensus of opinion now seems to be in favor of the former, since in 

 protected situations it is able to resist all but the most severe Euro- 

 pean conditions, and its other qualities place it far in the lead of the 

 mountain form. 



The table of height and diameter growth here given illustrates the 

 difference in rate of growth between the two forms when the}^ groAV 

 in virgin forests. They are averages read from curves, and were 

 obtained from ring counts along the average diameters of the stumps 

 and the ends of the logs of mature felled trees. Diameters are at 

 breastheight except those for western Washington, Avhich are at 

 stump height. On account of the height to Avhich stumps are cut in 

 this region, these figures are comparable to breastheight measure- 

 ments in other regions. The figures showing height growth in the 

 Targhee National Forest represent only partial analyses; that is, 

 they were derived from stump counts of the total age combined with 

 measurements of the total heights of the trees. The measurements 

 on the Uinta National Forest represent average conditions, and were 

 taken from merchantable trees grown under optimum conditions, as 

 well as in second-class situations. The figures from the San Juan 

 National Forest are from merchantable trees in a mixed stand of 

 Douglas fir, Engelmann spruce, and alpine fir near the upper alti- 

 tudinal limit of Douglas fir at an elevation of 10,300 feet. 



[Cir. 150] 



