PROTECTION OF FORESTS FROM FIRE 239 



sects. Thus, in certain conifers insects injure the trunks, 

 causing a local accumulation of pitch. A surface fire 

 later burns the tree at this point and kills one side. 

 The defect called "cat-face" is often caused in this way. 

 insect attacks, moreover, by increasing the number of 

 dead trees in the forest, increase the fire danger. 



In the case of large trees, which are very resistant to 

 fire, a first fire may kill the tissues on one side, and sub- 

 sequent fires may then burn into the dead wood until the 

 trunk is nearly hollow. This result is very commonly 

 seen in large white pines that have a large proportion of 

 the butt gouged out by repeated fires and are still alive. 

 Many of the large trees on the Pacific Coast, like red fir, 

 yellow pine, sugar pine, and bigtree, stand for many 

 years after injury of this character. 



The damage to a tree by killing a part of the trunk 

 or a part of the root depends on its resisting power and a 

 variety of other circumstances. In some cases the tree is 

 so weakened by the burning that it is afterward broken 

 off at the butt. This is verv common in long-leaf pine 

 forests, where old turpentine "boxes" burn out and 

 weaken the tree. 



The injury to the tree usually results in a reduced 

 rate of growth. It is obvious that if a portion of the tree 

 is killed, the whole tree cannot perform its functions 

 so effectively as before. The killing of a part of the 

 crown, stem, or root svstem necessarily reduces the 

 amount of nourishment which the tree can take in and 

 furnish the growing parts. 



