TIMBER GROWING AND LOGGING PRACTICE IN CALIFORNIA 69 
The highest yields and highest rate of growth after logging can 
be looked for in the sugar pine-white fir type, which is on the 
best sites and has the two species with the greatest potentiality for 
growth. The only requisite is that the timber be cut rationally, 
especially that decadent and defective white firs be removed. 
Two controllable factors influence to a pronounced degree the rate 
of growth attained after logging. These are the crown character- 
istics of the trees and their distribution. 
INFLUENCE OF CROWN FORM ON GROWTH RATE 
The importance of selecting trees with good crowns is well il- 
lustrated in Table 8, which uses yellow pine 12 to 30 inches in di- 
ameter to illustrate the annual growth rate percentage, for trees 
with crowns making up different proportions of the total height of 
tree. 
Table 8. 
-Relation of crown length to rate of growth in "basal area of yellow 
pine"^ 
Crown 
length 
on the 
basis of 
total 
height 
of tree 
Yearly growth for three sites 
Crown 
length 
on the 
basis of 
total 
height 
of tree 
Yearly growth for three sites 
Site I 
Site II 
Site III 
Site I 
Site II 
Site III 
Per cent 
30 
40 
50 
Per cent 
1.40 
1.50 
L75 
Per cent 
0.40 
.60 
.65 
Per cent 
0.40 
.40 
.45 
Per cent 
60 
70 
80 
Per cent 
2.40 
3.60 
4.90 
Per cent 
LOl 
L70 
2.50 
Per cent 
0.55 
.80 
L20 
1 Basis, 434 trees curved. 
As the relative length of the crown increases, the trees show more 
and more rapid growth. Naturally, the better the quality of the 
land, the higher is the growth rate, though the influence of crown 
length is important on all the sites studied. 
For yellow pine about 60 per cent of the total height is the most 
desirable proportion of crown for trees of the size usually reserved; 
trees with longer crowns are scarce in the forest and make little 
clear lumber. 
On an area of medium-quality forest, the trees of a given size 
were classed in two groups, the first composed of trees with crowns 
of average or larger size 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. 
EFFECT OF DISTRIBUTION OF TREES ON GROWTH RATE 
Study of trees on cut-over areas shows clearly that to obtain the 
maximum response to cutting, trees must be released, and that trees 
left in groups do not respond. This is well illustrated in Table 9. 
