14 
BULLETIN 790, IT. S. DEPARTMENT OF AGRICULTURE. 
Iii rating the averages for the various age classes x was given the 
valuation of 1, xx of 2, etc. In this manner averages such as 0.32 
and 2.9 were computed (see Table V), indicating the average degree 
of injury. 
Table V.— Relation of injuries to age and to total stand of western white pine 
on sites of the bottom and slope types. 1 
Age class. 
Infection traced tc 
Branch 
stubs. 
Num- 
ber. 
Per 
cent. 
Broken 
tops. 
Num- 
ber. 
Per 
cent. 
Frost 
cracks. 
Num- 
ber. 
Per 
cent. 2 
Fire scars 
and other 
injuries. 
Num- 
ber. 
Per 
cent. 2 
Total trees 
with in- 
juries to 
which 
infection 
was traced. 
Num- 
ber. 
Per 
cent. 3 
De- 
gree 
of 
in- 
jury. 
Total 
num- 
ber 
of 
trees. 
Bottom sites: 
41 to 60 years.. 
61 to 80 years.. 
81 to 100 years., 
101 to 120 years 
121 to 160 years 
161 to 200 years 
201+ years — 
Total 
Slope sites: 
41 to 60 years.., 
61 to 80 years.. 
81 to 100 years., 
101 to 120 years 
121 to 160 vears 
161 to 200 years 
201+ years 
Total 

75.0 
53.5 
70.4 
79.1 
90.3 
84.2 




1.2 

25.0 
46.5 
29.6 
19.7 
6.9 
10.5 

6.5 
17.1 
64.0 
66.7 
.7 
97.4 
0.32 
1.74 
2.09 
2.6 
2.9 
2.6 
3.0 
37 
62 
116 
111 
129 
76 
39 
241 
76. 
21.7 314 
55.0 | 2.4 
570 

3 
15 
26 
137 
47 
67 

75.0 
62.5 
63.4 
78.7 
57.3 
97.1 




.6 
3.6 


25.0 
37.5 
36.6 
20.7 
39.0 
2.9 
295 
74.8 

4 
24 
41 
174 
82 
24.4 
41.0 
74.0 
82.8 
394 
55.3 
.16 
. 7 
1. 41 
2.7 
2.68 
3.77 | 
50 
100 
235 
70 
1.9 
712 
i Percentage of total trees (infected and sound) bearing injuries to total trees in stand = 70. 
2 Percentage based on total number of infected trees. 
3 Percentage based on total number of trees. 
Table V shows certain interesting results. On both types of site 
the infections traced to branch stubs bear the largest percentage 
over infections traced to other injuries, with 77 per cent for the 
bottom sites and 75 per cent for the slope sites. Broken tops as 
sources of original infection were not found, although a considerable 
number of broken-top trees were recorded and some of these trees 
gave eA T idence that a certain amount of infection took place through 
the exposed tip. In nearly every case it was found that infection 
in the lower part of the trunk had taken place some time previous 
to the breakage of the top, as indicated by the difference. in the stage 
of development of the two rotted areas. On the bottom sites ap- 
proximately 2 per cent of the infections were traced to frost cracks 
and 22 per cent to miscellaneous injuries, which latter included fire 
scars, blazes, windfall scars, etc. On the slope sites only 1 per cent 
of the infections were traced to frost cracks and 24 per cent to 
miscellaneous injuries. On the slope sites a larger percentage of 
infection traced to miscellaneous injuries' is found than is recorded 
