6 BULLETIN 1294, U. S. DEPARTMENT OF AGRICULTURE 
As the early placer diggings were worked out and quartz and hydraulic 
mining became an important pursuit, prospecting extended in all di- 
rections. There is evidence that these early prospectors found them- 
selves hampered by brush and young growth, and adopted the practice 
of setting fire to the woods in order to facilitate their search for gold- 
bearing outcrops. Whether or not the early miners did actuaily 
= fires, it is certain that they had little mterest in controlling 
res, 
Certainly, the earliest reports of forest fires in California, those by 
Hough (1/2) and the California State Board of Forestry (5), make it 
clear that fires caused by white men were both common and exten- 
sive, and even in the eighties gave much concern to thoughtful 
observers. In the scanty forestry literature of the last quarter of 
the nineteenth century, comparatively little mention is made of the 
red men as being responsible for fires. Later history points to suc- 
cessive industrial developments such as grazing, railroading, and 
lumbering as causative agents in forest fires. 
It is clear that fires have occurred periodically as far back as the 
record is traceable. ‘The pine forests of California have thus been 
subjected to a cumulative process of attrition by fire, a process that 
is still at work in the forests and which is examined in detail in this 
study. 
FIRES IN THE VIRGIN FOREST 
INJURY FROM FIRE SCARS 
The virgin forest is characterized by the prevalence of fire-scarred 
trees, including particularly the oldest and largest individuals which 
have been longest exposed to fires. How such scars are started is 
easily explained by examining any forest area. On slopes the fire 
scars are invariably on the uphill side of the trees, where masses of 
litter, twigs, limbs, and similar material naturally accumulate, show- 
ing that fire scars originate usually from the burning of a mass of 
material against the bole of the tree. Nor does the amount of ma- 
terial necessary to start a scar need to be very great. 
FORMATION OF SCARS 
Study has shown (15) that the first stage in the formation of a scar 
is frequently no more than the killing of the living inner bark with- 
out burning away the outer bark, which at first remains closely 
adhering to the sapwood. Such a hidden scar, as shown in Plate I, 
may give no surface indications of its existence for many years. In 
the healing process, however, callouses form beneath the bark around 
the edges of the killed area of inner bark and, gradually growing in 
from the sides, force the bark away from the dead sapwood. This 
bulging growth of the callouses causes the dried bark to crack and 
split, and to drop away in pieces until finally the sapwood is exposed. 
Subsequent fires have direct access to the wood and are enabled to 
burn into the base of the tree, forming cavities in the butt. 
On an experimenta! light-burning plot‘ on Snake Lake 321 
trees were tagged and described in detail before the area was burned 
4 ‘Light burning,’’ as advocated by certain timberland owners, is a method of intentional, supposedly 
controlled burning of forest litter at comparatively safe seasons, with the object of reducing fire danger 
by decreasing the quantity of fuel on the forest floor. 
