22 
BULLETIN 139, U. S. DEPARTMENT OF AGRICULTURE. 
Table 12. — The crown width of dominant trees on basis of diameter breast-high. Itasca 
m County, Minn. 
[Based on 134 measurements.] 
Diameter 
Width of 
Diameter 
Width of 
breast-high 
crown 
breast-high 
crown 
(inches). 
(feet). 
(inches). 
(feet). 
3 
4 
13 
15 
4 

14 
15 

7 
15 
16 
6 
8 
16 
16 
7 
9 
17 
16 
8 
11 
18 
16 
9 
12 
19 
16 
10 
13 
20 
17 « 
17 f 
11 
13 
21 
12 
14 
The crowns of Norway pine trees are remarkably narrow com- 
pared with those of southern and western pines, which makes possible 
a larger number of trees per acre. An idea of the possible approx- 
imate yields which may be obtained under management is given in 
Tables 13 and 14. It can be assumed that with frequent thinnings 
the trees remaining in the stand will grow at the average rate of 
dominant trees and will have the width of crown indicated in Table 
12. Assuming that the average volume of these trees will be that 
shown in Table 10, it is necessary only to know the average number 
of trees per acre in order to ascertain roughly the yield of such stands 
at a specified age. 
The diameter of the average crown was squared in finding the 
number of such trees that could stand on an acre. Since crowns 
are circular, this introduced a factor of safety amounting to a reduc- 
tion of 22 per cent of the number of trees which might otherwise be 
computed as having growing space, and gives a crown density of 78 
per cent instead of 100 per cent. 
Table 13. — Yields per acre of dominant trees, calculated from diameter growth, average 
crown space, and number of trees per acre at different ages. 
Trees per 
Diameter 
breast-high 
(inches). 
Age 
(years). 
Volume of 
tree. 
acre from 
curve, 
based on 
crown 
space. 
Yields per 
acre. 
Board feet. 
Number. 
Board feet. 
8 
49 
23 
302 
8,280 
9 
56 
45 
266 
13,590 
10 
63 
67 
241 
17, 822 
11 
71 
94 
221 
22, 654 
12 
80 
128 
206 
28, 288 
13 
90 
160 
193 
32, 960 
14 
101 
197 
183 
38, 021 
15 
114 
242 
175 
44, 286 
16 
128 
289 
168 
50, 575 
17 
145 
329 
163 
55, 272 
18 
163 
383 
158 
62, 429 
19 
182 
444 
154 
70, 152 
20 
200 
505 
151 
77, 770 
