oF BULLETIN 1294, U. S. DEPARTMENT OF AGRICULTURE 
Similar evidence has been obtained from 12 acres of mature timber, 
comprising 445 trees of 12 inches diameter breast high, in what is 
known as the Moffitt Creek area. Fires are known to have occurred 
here in 1822 and 1850, with present day results as follows: 
Of 353 yellow pines 76 are scarred, or 21.5 per cent. 
Of 10 sugar pines 4 are scarred, or 40 per cent. 
Of 65 Douglas firs 4 are scarred, or 6.2 per cent. 
Of 17 incense cedars 4 are scarred, or 23.5 per cent. i 
Of the 445 trees, 88 in all were scarred, or 19.8 per cent, and the 
distribution of this injury indicates again that Douglas fir is less sus- 
ceptible than yellow pine to fire scarring. 
BURNING DOWN OF SCARRED TREES 
In studying the action of present day fires a careful observer can 
not fail to note that one inevitable result is the burning down of pre- 
viously scarred trees. Nearly everywhere in the virgin forest these 
scarred trees, usually the oldest and largest individuals in the stand, 
are evidence that fires have taken their toll, and that the forests of 
the present have been markedly influenced by the action of centuries 
of repeated fires. 
The final step in burning down is a purely mechanical process. The 
repeated fires, gradually eating into the base of the tree, destroy so 
much wood that the tree is unable to withstand mechanical strain 
placed upon it. Thisin part explains why the very large trees, which 
contain a high percentage of upper grades of lumber, are so suscepti- 
ble to this form of loss, though they are ordinarily fairly immune to 
other forms of heat injury. Table 1 shows that this kind of loss has 
occurred in every one of the large timber fires in this region of which 
an accurate appraisal of damage has beenmade. (PI. II, figs. 1 and 2.) 
The prevalence of burning down is perhaps the most striking 
feature of this table, but a pomt of almost equal interest is the 
relatively constant amount of loss that has occurred on burned areas 
where the fires were of widely varyimg intensity. For example, in 
comparing a fire with an extremely high intensity of heat, such as 
the Howard fire, to one of only a moderate intensity, as the White 
Horse fire, it is found that loss from burning down is less variable 
than might be expected. Likewise, on the Snake Lake fire, which is 
an experimental, early spring light burn of as low intensity as pos- 
sible, the loss per acre from burning down is of about the same mag- 
eee as on the Ham Station fire, which was a hot and destructive 
all fire. 
Without intimate knowledge of the forests of the California pine 
region and of the nature of forest fires, the reason for the striking 
uniformity of the damage from burning down and the prevalence of 
this form of loss might he difficult to isolate. On trees of several of 
the important species in this region, such as western yellow pine, 
sugar pine, and Douglas fir, once an open scar is started a heavy flow 
of pitch is put forth which covers the surface of the wound. With 
this highly inflammable coating, it is only necessary for a fire to 
reach the base of the tree to cause an enlargement of the scar, since 
the pitch on the surface and the pitch-impregnated wood of the 
wound burn fiercely for minutes and often hours after the main fire 
traveling on the forest floor has passed. 
