36 
BCLLETIX 544, Y. S. DEPARTMENT OF AGBICULTTTRE. 
For purposes of comparison Table 13, giving diameter growth of 
Norway spruce {Pice a excel sa^ is included. 
Table 13. — Diameter growth of Norway spruce. 1 
[crRVED.] 
Average 
Age. 
diameter 
breast high 
of stand. 
Years. 
Indie*. 
5 
1.0 
10 
2.8 
15 
4.4 
20 
5.7 
25 
6.S 
30 
7. 7 
35 
<4 
40 
9.0 
45 
9.6 
.50 
10.2 
55 
10.8 
60 
11.4 
1 Based on the measurement of all trees in 11 plantations (8 Qualities I and 3 Qualitv II) 24-55 vears 
old, made by Messrs. Tillotson, Barrows, and Williamson in 1911, in Rhode Island, Connecticut, Illinois, 
and Iowa. 
Even more than with height comparisons it is necessary to bear 
in mind the influence of soil, spacing, and cultural methods on the 
diameter growth of volunteer stands and plantations when drawing 
conclusions from the foregoing figures as to the relative growing 
qualities of red and Xorway spruce. 
SECTIONAL AREA GROWTH. 
The growth in sectional area, or the increase in the superficial 
area of a given cross section, is effective as a means of comparison 
for even-aged stands of different ages or of the same age but of 
different site qualities. Either the total basal area of the stand at 
a definite height from the ground, usually at breastheight, or the 
basal area of the average tree, may be employed. Table 14, covering 
second-growth, even-aged spruce stands of the old pasture type 
shows the relative average total basal area of stands of different 
ages and site quality based (1) on all green trees; (2) on green trees 
6 inches and over; (3) on all dominant trees; and (4) on all domi- 
nant and intermediate trees. 
