PROTECTION OF KORKSTS 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 causeci \n this \va)'. 

 Insect attacks, moreo\'er, b\' increasing the number of 

 dead trees in the forest, increase the fire danger. 



In the case of large trees, which are \'ery 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 

 trLuik is nearly hollow. This result is very commonix' 

 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 man\ 

 years after injury of this character. 



The damage to a tree b\ killing a part of the trunk 

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

 variety of other circumstances. Jn some cases the tree is 

 so weakened by the burning that it is afterward broken 

 ofT at the butt. This is very 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 ftmctions 

 so efTectiveh' as before. The killing of a part of the 

 crown, stem, or root s\stem necessarily reduces the 

 amount of nourishment which the tree can take in and 

 furnish the growing parts. 



