RESULTS OF CUTTING IN THE SIERRA FORESTS. 
Table 5. — Relation of crown length to rate of grotvth in basal area. 
[Basis, 434 trees. Curved.] 
Crown ratio. 
Annual per cent. 
Crown ratio. 
Annual per cent. 
Site I. 
Site II. 
Site III. 
Site I. . 
Site II. 
Site III. 
30 
1.40 
1.50 
1.75 
0.40 
.50 
.65 
0.40 
.40 
.45 
60 . 
2.40 
3.60 
4.90 
1.01 
1.70 
2.50 
0. 55 
40.. 
70... 
.80 
50 
80... 
1.20 
Trees with narrow, long crowns are usually growing more rapidly 
than the average trees of the same size. For yellow pine, probably 
60 per cent of the total height is the most desirable proportion of 
crown for standards of the size usually reserved. Trees with larger 
crowns are too limby, and those with shorter ones are apt to be 
growing slowly. On all the sample plots considered here, the length 
of crown for all size classes averages 65 to 70 per cent of the total 
height. On poor sites, density of stocking being the same, trees of 
a given size carry relatively smaller crowns than on good sites, as is 
shown by Figure 1. 
A significant fact brought out clearly during this study is that the 
ordinary crown classification based on position of trees in the crown 
canopy, when applied to irregular mixed stands of this character, is 
practically valueless as an indication of relative vigor of individual 
trees. Taking trees of the same size and species representing the 
ordinary dominant, codominant, intermediate, and suppressed 
groups as carefully classified in the field, one would expect to find 
a definite relation between crown class and the crown-height ratio, 
and between crown class and rate of growth, increasing from the 
suppressed to dominant trees. This is not found to be true of the 
present data, although it doubtless is true for even-aged stands. 
Taking 318 yellow pines on the Plumas plot classed as dominants 
and segregating them into two groups, the first composed of trees 
with crowns of average size or larger and pointed tops, the second 
with smaller than average crowns and round, flat, or dead tops, it 
was found that the trees of the first group were growing at a rate of 
1.22 per cent annually in basal area, while those of the second group 
were growing at a rate of only 0.42 per cent annually. On the same 
area trees of the same size, called intermediate and suppressed, were 
divided into similar groups. The first of these were growing at the 
rate of 1.37 per cent and the second 0.96 per cent annually, or con- 
siderably faster than dominants of the same character. 
The several important observable factors which contributed to an 
accurate estimate of vigor might be combined into four thrift or t ree 
classes, which would guide in the mental appraisal of each tree 
according to the following standards : 
Class 1. — Dominant, codominant, or isolated trees, with pointed 
tops, well-shaped crowns forming 60 per cent or more of the total 
height; sound, symmetrical trunks; bark characteristic of young 
trees; foliage dense and rich in color. 
('lass 2. — Similar to the above in all respects except with crowns 
of smaller than average size. 
