THE BED SPRUCE. 
55 
be noted. This would ordinarily vary between 25 and 40 per cent, 
depending on whether maximum solid volume or board-foot volume 
was the desired object. However, the response to thinnings made 
in spruce having an average crown length of less than 25 per cent of 
the height will be exceedingly slow and for that reason of doubtful 
financial value. 
In Table 19 an attempt is made to predict the yield due to accel- 
erated growth to be obtained by thinnings made at different ages and 
with varying degrees of severity. 
Table 19. — Yield from stands of average quality thinned for maximum volume production 
of pulpwood (unpeeled cords) based on the cutting of dominant (including codominant) 
and intermediate trees only. Minimum merchantable size, 6 inches in diameter at 
breastheight and 5 inches in diameter outside bark in the top. 
4 THINNINGS. 
Age of 
stand. 
Number of dominant and in- 
termediate trees. 
Propor- 
tion of 
trees re- 
moved. 
Mer- 
chantable 
volume 
of trees 
removed. 
Final 
yield. 
Total 
yield. 
Equiva- 
lent mean 
annual 
growth. 
In fully 
stocked 
un- 
th inned 
stands. 
To be 
left after 
thinning. 
To be re- 
moved in 
thinning. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
Years. 
25 
30 
35 
40 
45 
1,316 
1,062 
890 
774 
605 
1,097 
014 
762 
635 
220 
183 
152 
127 
i 
§ 
1 
Cords. 
Cords. 
Cords. 
Cords. 
4.9 
5.6 
7.4 
44 
61.9 
1.37 
682 
17.9 
THINNINGS. 
25 
35 
45 
50 
1,316 
890 
697 
605 
1,054 
791 
593 
263 
263 
198 
1 
7.1 
9.5 
16.6 
44 
60.6 
1.21 
724 
2 THINNINGS. 
30 
40 
50 
1,062 
774 
605 
849 
637 
212 
212 
1 
10.2 
44 
54.2 
1.10 
424 
10.2 
The basic values are taken from Table 17, giving the yields for 
unthinned, fully stocked, old-field spruce stands of second quality. 
The volume production of these stands reaches a maximum in the 
fifty-fifth year and is 44 cords per acre. The assumption is made in 
Table 19 that 4 thinnings will reduce the natural rotation 10 years; 
