IV 



FIRE AND WIND 



The worst enemy of the Pennsylvania wood- 

 lands, and especially of the coniferous forests, 

 is fire. Very few of the Pine woods visited in 

 the course of this investigation were without 

 traces of it. Although many of the fires run 

 only upon the surface and do no direct harm 

 to the timber itself, the indirect injury which 

 results from burning the humus layer and dry- 

 ing out the soil is very serious, and should not 

 be overlooked. Such fires are often followed 

 by a decrease in the rate of annual growth from 

 which it may take the trees several years to re- 

 cover. In very many other cases the injury to 

 the tree is both direct and important. Often 

 the bark of the butt is scorched or burned, and 

 the cambium layer below it killed by heat. Then 

 the bark loosens or drops away, and decay sets 

 in soon afterward. 



When exposed to fire the young growth, with 

 its delicate bark and foliage, is killed at once. 

 Later on, when the trees have reached an age 

 of forty to sixty years, and have formed thick 



3 33 



