10 BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 
be present in Douglas fir stands in the future, no matter how well 
regulated. Consequently, the reduction in the quantity of rot in 
Douglas fir by a reduction in the scars caused by controllable 
mechanical injuries can amount to little. 
Table 9. —Infection court of combined decays in Douglas fir. 
Infections. 
Percentage of total. 
Infection court. 
Number, 
basis. 
Volume. 
nvciago v uiuuiv. 
Number. 
Board 
feet. 
Cubic 
feet. 
Board 
feet. 
Cubic 
feet. 
Knots . 
123 
43.3 
89.2 
89.2 
664 
63.9- 
Fire scars. 
67 
23.6 
4.2 
4.2 
57 
5.5 
Falling-tree scars. 
18 
6.3 
2.2 
1.7 
114 
8.2 
Lightning scars... 
19 
6.7 
2.5 
2.4 
123 
11.5 
Dead tops . .. . 
30 
10.6 
.6 
1.0 
19 
2.8 
Roots. 
19 
6.7 
.5 
.6 
25 
2.6 
Unknown scars. 
8 
2.8 
.8 
.7 
88 
8.0 
While it is true that infection courts resulting from all mechanical 
injuries are of little importance in the total volume of decay produced 
as compared to knots or branch stubs, it is of academic interest to 
determine the kind of scar most susceptible to infection in the trees 
studied. This is brought out in Table 10. 
Table 10. —Susceptibility to infection of various scars in Douglas fir . 
Type of scar. 
Number 
of scars. 
Scars infected. 
Type of scar. 
Number 
of scars. 
Scars infected. 
Number. 
Per cent. 
Number. 
Per cent. 
Fire scars 
280 
67 
23.9 
Spike tops. 
* 
30 
44.1 
Falling-tree scars.. 
86 
18 
20.9 
Broken, tops. 
> 68 
Lightning scars ... 
49 
19 
38.8 
Unknown scars.... 
7 
7 
100 
Sapsucker scars ... 
10 
0 
0 
Blaze scars. 
1 
0 
0 
Total. 
5C8 
141 
28.0 
Frost cracks. 
7 
0 
0 
Dead tops, which include spike-tops and broken tops, followed 
by lightning scars, were most susceptible to infection, according to 
Table 10. 
INDICATIONS OF DECAY IN LIVING TREES. 
Recognition of the indications of decay in standing Douglas fir or 
in logs is of the greatest importance from a practical standpoint. 
A comparison of the cruise and actual cut on many operations in 
overmature decadent timber brings this out forcibly. At present 
there is a great deal of confusion and misinformation among foresters 
and lumbermen in regard to the detection of decay in living trees, 
and the specter of “hidden defect” assumes unnecessary proportions. 
In fact, decay in Douglas fir is more easily detected than in most 
species subject to a large amount of rot. 
