6 
BULLETIN 1163, U. S. DEPARTMENT OF AGRICULTURE. 
Wounds in Douglas fir, though quite common, are mostly super- 
ficial and heal rather rapidly. Rapid healing is particularly the 
case in younger trees. Wounds as a rule callus very irregularly, and 
as a result it is usually difficult or impossible to determine the exact 
dates when scars were made and callused over by counting the annual 
rings. In this respect Douglas fir differs strikingly from the clear- 
cut, regular calluses characteristic of incense cedar and white fir. 
Furthermore, injuries in Douglas fir frequently result in the formation 
of prominent burls. 
Of the trees studied, only 11 were entirely free from scars. The 
remaining 158 trees had 508 scars, open and healed over, an average 
of 3.2 wounds per tree. Table 3 shows the relative frequency of the 
various types of scars 
Table 3. — Scars in Douglas fir. 
Number of scars, basis. 
Per- 
cent- 
age of 
total 
scars. 
Type of scar. 
Open. 
Healed 
over. 
Total. 
Fire scars 
43 
25 
11 
1 
1 

237 
61 
38 
9 

7 
280 
86 
49 
10 
1 
55.1 
16.9 
9.6 
2.0 
.2 
Falling-tree scars. . . 
Lightning scars 
Sapsucker scars.. 
Blaze scars 
Frost cracks 
7 1.4 
Type of scar. 
Spike tops 
Broken tops 
Unknown scars. 
Total 
Number of scars, basis. 
Open. 
Healed 
Total. 
Per- 
cent- 
age of 
total 
2.0 
11.4 
1.4 
In Table 3 the healed-over, closed, or occluded scars are greatly in 
the majority. This indicates that the wounds were mostly superficial 
and that this tree species heals rapidly after wounding. 
The predominance of fire scars is striking. While it was not pos- 
sible to determine the years in which the fires occurred, for the reason 
stated previously, it was noticeable that most of the injuries of this 
nature had happened when the trees w T ere relatively young — that is, 
below 20 inches diameter breast high, more or less. This coincides 
with our knowledge of fires in the Douglas fir region. In young 
stands fires which run over the surface of the ground injuring but 
not killing the trees are common, while in mature or overmature 
timber fires have a tendency to run through the crowns, killing all but * 
scattered individuals outright. 
Burls may form as the result of lire scars, but more common are 
swollen, or churn, butts as the result of severe scars. These churn 
butts extend usually from the ground level up the trunk slightly 
higher than the limit of the fire scar. Even though a fire scar has 
been healed over for a long time and there is no churn butt or burl 
to indicate its presence, it can often be detected by the variation 
in the appearance of the bark over the healed wound. This appear- 
ance is hard to describe, but not difficult to judge after a little 
experience. 
Next in numerical importance to fire scars were wounds caused by 
falling trees. These, of course, are more common in mature and 
overmature stands than in second growth. Trees may die and ulti- 
mately the snags will fall, or again large trees with butt-rot are 
quite subject to windfall. Such trees on their way down strike 
others, breaking off the tops or limbs or bruising the trunks and 
knocking off pieces of bark. Falling-tree scars rarely extend deeply 
into the tree. 
