76 PRACTICAL FORESTRY IN 



sents is 125 high at 50 years and its average 50-year-tree is 

 14 inches in diameter, little investigation is necessary to 

 determine whether in any given locality the growth falls far 

 above or below that. 



An attempt to reproduce here any considerable number 

 of growth and yield tables would be of doubtful use without 

 more space than is allowed to explain how they are made and 

 used. There are many technicalities, both mathematical and 

 silvicultural, and unfortunately most of the available figures 

 for the Northwest, obtained by the Forest Service, have not 

 been generalized enough for wide popular value. This is par- 

 ticularly true of yield tables which necessarily require assum- 

 ing standards of merchantability. While the best western 

 white pine table assumes that by the time a new crop is cut 

 7-inch white pine will be salable, the best fir table was worked 

 upon a 12-inch diameter basis. Obviously this would show 

 an unfairly greater yield of a pine forest containing trees 

 between 7 and 12 inches and be very misleading in calculat- 

 ing financial results at the same age and stumpage rates; yet 

 without the original data there is no way of reducing both 

 tables to the same basis. As an example, however, to indicate 

 how the financial possibilities of second growth can be arrived 

 at if a systematic study is made, let us take the Douglas fir 

 figures referred to. 



DOUGLAS FIR 



These are exceedingly reliable. Measurements were taken 

 by the Forest Service of practically pure fir on about 400 

 areas in thirty-five different age stands from 10 to 140 years 

 old, ranging along the western Cascade foothills from the 

 Canadian line to central Oregon. Since reforestation invest- 

 ment is likely to be confined mainly to the more promising 

 opportunities, only such growth was measured as gave an 

 average representation of the better class of the two should 

 all the general territory covered be graded in two quality 

 classes of all around ability to produce forests. On the other 



