198 Forestry Quarterly. 



in this respect than most of the oaks. Character of the wood is 

 one of the lesser considerations of initial resistance but of great 

 importance in subsequent and continued resistance. 



The sum of these factors of resistance for a species or indi- 

 vidual comprise what we may call its Initial Resistance ; that is, 

 the resistance which a sound tree offers to the first fire which 

 attacks it, at the time of the attack. No species surpasses all 

 others in all resisting qualities, but some average more resistance 

 than others. Thickness of bark, character of wood and of root 

 system are more especially specific characters and vary more with 

 the species, the others with individuals and seasons. 



//. THB AFTER EFFECTS OF A SINGLE FIRE. 



The effects of a fire do not cease as soon as the ashes cool, but 

 are felt through many years. The damage may be increased by 

 other agencies, or be wholly or partly repaired by growth. 



In the after history there are two distinct factors to be con- 

 sidered: (i) The resistance of the tree to subsequent agencies, 

 (2) Its recovery power exhibited by the healing of its wounds. 



Resistance to Subsequent Agencies: It is known that nearly all 

 decay of woody tissue is due to the action of fungi. Fungi to at- 

 tack a tree must generally find some opening in its bark, and they 

 seem to grow better on trees weakened in some way. Consequent- 

 ly fire by exposing the wood and reducing the vitality of the tree, 

 sets up a condition favoring their growth. 



Fungous attacks following injury by fire are of various kinds, 

 dependant upon the character of the fungus. Infection may be 

 by one attacking only dead wood as Polystictus pergamenus so 

 frequently found on fire injured Red Oak and other deciduous 

 trees. According to Von Schrenk,* this fungus can destroy only 

 as much wood as has already been killed. Other fungi which fol- 

 low fire can grow from the dead into the living wood or attack it 

 directly. They are consequently more to be dreaded. Those 

 fungi which attack only heartwood follow a fire only when it has 

 been severe enough to expose this. Another group is the bark 

 fungi which attack the bark and the cambium beneath. These 

 may be more deadly than those operating in the wood although 

 they do not destroy the wood of the trees they kill. Diaporthe 



♦"Diseases of Deciduous Trees," Bulletin 149, Bureau of Plant Industry. 



