NOKWAY PINE IN THE LAKE STATES. 
21 
sand barrens where there are small openings may, even in the case of 
plantations, be from three-fourths to one-fourth of these amounts. 
Table 11 is based 6n 85 sample plots from 40 to 200 years old. 
Table 11. — Yield per acre of fully stocked even-aged stands according to three quality 
classes. 
Yield per acn 
.Age 
(years). 
Quality I. 
Quality II. 
Quality III. 
Board ft. 
Board ft. 
Board ft. 
40 
4,100 
2,000 
50 
9,400 
6,100 
"2, 800 
60 
15, 100 
10, 200 
5,300 
70 
20, 900 
14,300 
7,900 
80 
26, 500 
18,600 
10, 700 
90 
32,300 
22, 900 
13, 700 
100 
38, 500 
27, 400 
16, 900 
110 
44, 700 
32, 000 
20, 100 
120 
50, 800 
36, 700 
23, 100 
130 
56, 800 
41, 200 
25, 800 
140 
60, 500 
43, 900 
27, 900 
150 
62, 300 
45, 700 
29, 500 
160 
63,300 
46,900 
30, 600 
170 
63, 700 
47, 500 
31, 100 
180 
63, 700 
47, 700 
31,300 
190 
63,000 
47,300 
31,300 
200 
61, 800 
46, 500 
31,000 
The mean annual growth in board feet culminates on all the quali- 
ties of site at about 140 years. There is a slight further increase in 
volume until 170 years on Quality I, and to 180 years on Qualities II 
and III, but the mean annual growth per acre falls off, and soon 
the stand itself begins to lose in volume from windfalls, old age, and 
fire. The maximum mean annual yield on good soils hardly exceeds 
400 per year, and on Quality III sites 200 feet. These yields are for 
natural Norway pine sites, whose quality is at best much below that 
of soils occupied by white pine and hardwoods. Since Norway pine 
will grow on any well-drained soil, if started in full sunlight, yields 
from plantations, even when unthinned, on the richer soils may 
amount to from 500 to 800 board feet per acre per year. Since Nor- 
way pine can form fully stocked stands only under ideal conditions 
of light and moisture, which are seldom met with in nature, the aver- 
age stand per acre of pine, either Norway or white, actually comes 
nearer to being 5,000 or 10,000 feet, instead of the 40,000 or 60,000 
feet yielded by fully stocked areas. 
The openings in ordinary stands of Norway pine are occupied by 
poplar, birch, and scrub oaks, although none of these species do as 
well as Norway pine on sandy soils. Even if these inferior species 
could be utilized, nothing like the returns can be secured as from fully 
stocked stands of Norway pine. It is safe to say that with complete 
stocking the average production of large areas can be increased five- 
fold. 
The number of trees on fully stocked areas depends in part on the 
width and shape of the crown. Table 12 gives an idea of the average 
width of crowns of trees of different diameters. 
