20 
BULLETIX 139, U. S. DEPARTMENT OF AGRICULTURE. 
with a table in volumes for trees of different diameters and heights. 
The table indicates that Xorway pine grows in volume at a uniform 
rate to an advanced age. 
Table 10. — Growth in volume, on basis of age, of average dominant trees, Cass County, 
3f in n . 
Age 
(years). 
Diameter. 
Height. 
Volume. 
Scribner 
rule. 
Periodic growth for 
10-year periods. 
Mean annual growth. 
Inches. 
Feet. 
Cubic feet. 
Board feet. 
Cubicfeet. 
Board feet. 
Cubicfeet. 
Board feet. 
10 
O.S 
8 
20 
2.8 
4.9 
6.6 
8.2 
21 
35 
47 
58 
30 
2.3" 
5.3 
10.1 
6." 77" 
.133 
.202 
40 
3.6 
4.8 
50 
27" 
"6.54 
60 
9.6 
66 
15.8 
57 
5.7 
30" 
.263 
.96 
70 
10.9 
72 
21.1 
90 
5.3 
33 
.301 
1.29 
80 
12.0 
76 
27.4 
128 
6.3 
38 
.343 
1.60 
90 
13.0 
80 
34.0 
160 
6.6 
32 
.355 
1.77 
100 
13.9 
83 
40.6 
193 
6.6 
33 
.406 
1.93 
110 
14.7 
85 
46.3 
228 
5.7 
35 
.421 
2.08 
120 
15. 5 
87 
53.8 
263 
6.5 
35 
.448 
2.19 
130 
16.1 
88 
59.0 
• 2S6 
5.2 
33 
.454 
2.20 
140 
16.7 
89 
63.6 
314 
4.6 
28 
.454 
2.25 
150 
17.3 
90 
69.4 
345 
5.8 
31 
.463 
2.30 
160 
17.8 
91 
74.4 
374 
5.0 
29 
.465 
2.34 
170 
18.4 
91 
79.3 
405 
4.9 
31 
.465 
2.39 
180 
18.9 
92 
84. 4 
437 
5.1 
32 
.469 
2.43 
190 
19.5 
92 
89.3 
470 
4.9 
33 
.470 
2.47 
200 
20.0 
93 
94. 6 
505 
5.3 
35 
.473 
2.52 
YIELD. 
The growth in diameter, height, and volume of individual Xorway 
pine trees is of little aid in determining the yield per acre. Yields of 
stands of different ages are best found by actual measurements of 
stands of the age to be recorded. The yield of even-aged stands is 
then determined by multiplying the volume of the average tree by 
the number of trees on the area. The sample plots upon which 
Table 11 is based were located in Cass and Itasca Counties, Minn. 
The plots selected for measurement were completely stocked with 
pine. A mature and fully stocked Norway pine stand forms a prac- 
tically complete crown cover. The crowns themselves are not dense 
nor is the shade deep, though it is usually sufficient to exclude from 
the dry and sandy forest floor practically all underbrush, leaving only 
a carpet of needles. At the age of 150 years, however, the stand 
begins to thin out, and by 200 years the canopy will be broken, with 
many blanks caused by the death of trees. The yield per acre at 
this time is actually less than at an earlier age. 
The method followed in constructing Table 11 was to plot the 
yield of each sample plot on cross-section paper, on the basis of age. 
The space between the maximum and minimum curves was then 
divided into three parts, representing good, medium, and poor yields. 
These coincide roughly with the three qualities of soils upon which 
the plots were taken. A curve was then drawn through the center 
of each space representing the qualities, from which the yields for each 
age were read. In applying this table it should be remembered that 
the figures represent a theoretically perfect stand. Actual yields on 
