THE RED SPRUCE. 



57 



Table 20. — Yield from stands thinned for production of superior quality lumber, based 

 on the cutting of dominant (including codominant) and intermediate trees only. Mini- 

 mum merchantable size, 7 inches in diameter at breastheight and 6 inches in diameter 

 outside bark in the top. 





Number of dominant and interme- 

 diate trees only. 



Propor- 

 tion of 

 trees 

 removed. 



Merchant- 

 able volume 

 of trees 

 removed. 



Final 

 yield. 



Total 

 yield. 



Equivalent 



Age of 

 stand. 



In fully 



stocked. 



unthinned 



stands. 



To be left 



after 

 thinning. 



To be 

 removed in 

 thinning. 



mean 

 annual 

 growth. 



1 



2 



3 



4 



5 



6 



7 ' 



8 



9 



years. 

 45 



1,316 



S90 

 697 

 605 



1,053 



263 



s 



B&.ft. 



Ed. ft. 



Bd.ft. 



Bd.ft. 









55 



514 



129 



\ 



3,870 











so;;:;:::::; 



551 





I 









516 

 492 



472 



463 





i 1 







105 



347 



116 i | 7,775 







115 











! 

 1 





25,630 





120 



11,645 



37,275 31(1 









i 







It has been assumed in this case that at the time of removal of 

 the hardwood cover, in the forty-fifth year, the understory of spruce 

 would have a development parallel to that of a 25-year-old stand 

 which had started in the open. Thus by adding 20 years to the dif- 

 ferent ages given in Table 17 the equivalent yields in unthinned 

 stands up to 120 years are obtained. 



The first thinning is indicated to be light and unremunerative, but 

 there would doubtless be yielded at least a small amount of cord- 

 wood, which would be the class of material chiefly yielded by the cover 

 crop of aspen, birch, and other hardwoods taken out at this cutting. 

 The cut, as a whole, should therefore "show a fair profit. This thin- 

 ning would reduce the number of dominant and intermediate trees 

 in the stand to a spacing of about 7 by 6 feet or that found in a nor- 

 mal unthinned stand seven years older, although the cover would 

 doubtless entirely close in five years or less. The relief from compe- 

 tition should, however, occasion such an acceleration in growth for 

 the 20-year period before the next thinning as to gain 5 years over 

 the unthinned stand. Thus the stand at the next thinning, in the 

 sixty-fifth year, would have the development shown for 70-y car-old 

 mithinned stands, or 643 dominant and intermediate trees to the acre. 



From the sixty-fifth year on to the one hundred and fifth year, 

 when the third thinning would take place, the reduction in numbers 

 in natural unthinned stands is very gradual, 54 between the seven- 

 tieth and seventy-fifth years, and but 11 between the one hundredth 

 and one hundred and fifth years. The removal of one tree in 

 five from the dominant and intermediate crown classes at the sixty- 

 fifth year would consequently reduce the number of stems to that 



