236 THE PRINCIPLES OF HANDLING WOODLANDS 



the foliage of coniferous trees is completely consumed. 

 Hardwood trees in mixture are generally so badly scorched 

 that the buds, leaves, and living tissues in other finer 

 parts of the tree are killed, if not consumed, by the heat. 

 Sometimes, however, where the fire burns somewhat 

 irregularly as, for example, where there are a good 

 many hardwoods in mixture or the fire is broken by 

 irregularities in topography many single trees or groups 

 of trees escape injury. 



Ground fires, also, usually kill all trees in their way, 

 for although they burn very slowly, they generate a great 

 volume of heat and kill the living tissues of the roots. 

 Sometimes the injury is not apparent above ground at 

 all, but the trees die and, after a time, are blown over, 

 because the roots have been killed and weakened. 



Surface fires kill seedlings and young trees with ten- 

 der bark, but in a great many cases do not kill outright 

 the larger trees. Nevertheless, a very severe surface fire 

 may kill everything in its path, and, not uncommonly, 

 hardwood forests are entirely destroyed by fires which do 

 not at any time assume the character and proportions of 

 crown fires. 



Some species have much greater power of resisting 

 surface fire than have others. This is usually due to the 

 character and thickness of the bark. Trees with delicate, 

 thin bark are killed much more readily than those with 

 thick, corky bark. Young trees are killed more readily 

 than old ones, because the bark is thin, and there has not 

 been developed the layer of cork, which increases in 



