ROLE OF FIRE IN CALIFORNIA PINE FORESTS 3 
losses on the future timber supply and on the problem of forest 
management. An intensive study of ‘‘light-burning” experiments 
and some discussion of possible beneficial uses of fire apart from 
light burning is included. On the basis of these observations the 
effort is made to present a workable theory of fire protection in rela- 
tion to forest policy. 
The need for study of the actual physica action of fire was early 
recognized, and by 1911 studies of the fundamental facts of fire 
damage were begun. Some of these investigations have been con- 
tinued up to the present, and include the effect of surface fires in 
reducing hazard, the relation of crown injury to rate of growth, the 
effect of repeated fires on the enlargement of fire scars, the influence 
of fire on the forest type, and the relation of fires to insect epidemics. 
Supplementary to these studies, careful cruises on many large fires 
have been made in the attempt to supply more general figures of the 
average rate of loss by the acre on such fires. As these figures were 
athered a sufficient length of time after the fire to permit determin- 
ing the actual extent of damage, they have been used in this bulletin 
in preference to those in the original fire reports. The writers have 
also had the advantage of observational data collected by themselves 
and other forest officers in this region during the past 12 years, and 
have used freely the material of many others who have made special 
investigations of fire in relation to forest insects, tree diseases, and 
related problems.* 
The result is not claimed to be the final word on this important 
subject. Detailed study by many men for more than a decade, how- 
ever, now permits the drawing of a reasonably complete, accurate, 
and well-balanced picture of the part fire plays. 
FIRE HISTORY OF THE CALIFORNIA PINE REGION 
DATA FROM FIRE SCARS 
The history of the periodic fires in the virgin forests of California 
throughout the past centuries—fires which have largely determined 
the present condition of our forests—is derived in some measure 
from written historical evidence, but mainly from the careful study 
of fire scars on the trees themselves. Fires record themselves on 
living trees by killmg or burning away part of the outer bark, the 
inner bark, and the wood of the bole. en such scars are formed, 
an immediate attempt is made by the tree to cover them over with 
new wood which grows from the living edges of the inner bark 
toward the center of the wound. With no further reopening, the 
wound will eventually heal completely over with wood and bark and 
become a concealed scar. The date of such an injury can years 
afterwards be accurately determined by counting the number of 
annual rings that have formed in the callous growing over the scar, 
plus any rings that may uninterruptedly cover the scar after com- 
plete healing has taken place. Furthermore, because the face of the 
wound is charred, a scar caused by fire can be distinguished with 
certainty from scars of injuries caused by lightning or mechanical 
agencies. 
8In this connection the writers desire to make specific acknowledgment to Swift Berry, Ralph 
Hopping, Duncan Dunning, F. D. Douthitt, and D. K. Noyes. 
