THE BED SPBUCE. 
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. 
Age of 
stand. 
Number of 
d 
In fully 
stocked 
unthinned 
stands. 
dominant a 
ate trees onl 
To be left 
after 
thinning. 
ad interme- 
y. 
To be 
removed in 
thinning. 
Propor- 
tion of 
trees 
removed. 
Merchant- 
able volume 
of trees 
removed. 
Final 
yield. 
Total 
yield. 
Equivalent 
mean 
annual 
growth. 
1 
2 
3 
4 
6 
i 
8 
9 
Years. 
15 
1, 316 
SQO 
697 
605 
551 
516 
492 
472 
463 
1,053 
263 i | 
Bd.ft. 
Bd.ft. 
Bd.ft. 
Bd.ft. 
;:::::::::: 
514 
129 i 
3,870 
85 
95 
1 __ l 
ior> 
347 
116 
Tl 
7,775 
115 

25, 630 
37, 275 
120 
11, 645 
310 

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 gam 5 years over 
the unthinned stand. Thus the stand at the next thinning, hi the 
sixty-fifth year, would have the development shown for 70-year-old 
unthinned 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 1 1 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 
