TABLE 1. — Number of trees and basal area per acre for three stand densities, 
before and after thinning 
Basal area left 
Before thinning at age 35 
ae after each Basal area at site index 
thinning 50 60 
Square feet Number Square feet 
T.ow 90 165 180 
Medium 120 180 195 
High 150 195 210 
density; and high initial stocking thinned to a 
high basal area density. These approximate 
the range of current stand density manage- 
ment practices in the Lake States. 
As figure 1 shows, by keeping a stand at 
a low rather than a high density, the forest 
manager can produce trees of a given diam- 
eter at an earlier age, or he can produce 
larger diameter trees at any given age. For 
example, if he wishes to grow 15-inch trees 
on site-index-60 land, he will get them at age 
75 with low-density management, at age 105 
with medium-density management, and at 
age 165 with high-density management. Or, 
at age 95 he will have 20-inch, 13-inch, or 
10-inch trees depending upon whether he 
chooses to manage his stands at a low, medi- 
um, or high density. It also follows that at a 
25 
(inches) 
ia) 
fe) 
a 
BREAST HIGH 
° 
DIAMETER 
25 45 65 85 105 
STAND AGE (years) 
given age the trees removed in thinning will 
be larger in low-density stands than in high. 
Larger diameter trees can be grown at 
earlier ages on better sites. For example, by 
age 95 with low-density management, site- 
index-60 land will produce trees averaging 
3% inches larger than those on site-index-50 
land. This difference in diameters is especial- 
ly large at older ages and low densities. Of 
course the trees will also be taller on the bet- 
ter sites, thus increasing the difference in in-. 
dividual tree volume. 
The combined influence of stand density 
and site on diameter growth rates is large 
(table 2). In low-density stands on site-index- 
60 land, diameter growth is rapid, with never 
more than 10 annual rings per inch after age 
45. At the other extreme, in high-density 
Low Density 7low 
Medium 
~ «Medium 
FicuRE 1. — Expected 
diameter of the tree 
of average basal area 
in red pine stands 
managed at iow, 
medium, and _ high 
densities. 
High 
Site Index 60 
e2eae Site Index 50 
145 165 
