12 
BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. 
and the average tree on each, of 14 other sample areas, or a total of 
559 trees. All the trees of the three crown classes in the stand and 
on the different qualities of site are represented. Under the influence 
of all these different factors, which are considered variables in mat- 
ters of tree growth and volume increment, the size of both diameter 
and crown spread have been found to vary uniformly and in the same 
direction. This intimate relationship between tree diameter and 
crown spread is apparently an expression primarily of tolerance or 
relative demand of the species for light. 
Table 4 gives the average crown spread in feet of each breast-high 
diameter class from 5 to 16 inches. It shows a perfect regularity 
between the size of the tree and the space occupied by its crown, 
irrespective of age and vigor. 
The table shows that for each increase of 1 inch in tree diameter the 
crown spread increases 1.4 feet in Arkansas and 1.75 feet in New 
Jersey. This difference in rate is probably due to the effect of differ- 
ent climatic conditions upon the tolerance of the species. During 
earlier life up to about 15 years the relation appears- to be in the 
ratio of 1 foot of crown spread to each inch in tree diameter. 
This law of growth finds practical application in determining for 
any specified diameter class the total number of trees that can most 
profitably be grown per acre in a well-stocked stand. Since diameter 
is a direct function of age in any given quality of situation, the tree 
density on the ground at any desired age can likewise be ascertained. 
Knowledge of this sort is fundamental in working out problems of 
thinning, cutting, and final yields of timber. 
Table 4. — Relation of tree diameter and crown diameter for shortleaf pine trees in fully 
stocked stands for all ages from 20 to 80 years — Contrast of regional difference for 
Arkansas and New Jersey. 
Crown diameter. 
Favorable region (Arkansas), j ^^f^™ (New 
Tree diameter breast high (inches). 
Crown 
diameter. 
Amount 
of 
increase. 
Differ- 
ence in 
crown 
diameter 
and tree 
diameter. 
Crown 
diameter. 
Amount 
of 
increase. 
Differ- 
ence in 
crown 
diameter 
and tree 
diameter. 
Feet. 
5.2 
6.6 
8 
Feet. 
------ 
1.4 
1.4 
1.4 
1.4 
1.4 
1.4 
1.4 
1.4 
1.4 
1.4 
Feet. 
4.8 
6.1 
7.4 
8.7 
10.05 
11.4 
12.7 
14 
15.3 
16.6 
17.95 
19.3 
Feet. 
3.25 
5 
6.75 
8.50 
10.25 
12 
13.75 
15.50 
Feet. 
Feet. 
2 85 
6 
1.75 
1.75 
1.75 
1.75 
1.75 
1.75 
1.75 
4.5 
6.15 
8 
9 
10 
11 
12 
13 
9.4 
10.8 
12.2 
13.6 
15 
16.4 
17.8 
19.2 
7.8 
9.5 
11.21 
12.85 
14.5 
14 
15 
16 
20.6 
