150 



PRINCIPLES OF AMERICAN FORESTRY. 



weatlier, they are unusually destructive, and leave very 

 little humus in the top soil. For some reason, land that 

 has been burned over in this way is a long time in recover- 

 ing from its injuries. Besides the injuries already cited, 

 all forest fires kill or drive out much of the game in our 

 forests. 



Fig. 55. — A Fire Fall. Roots burned off and trees blown 

 down in great confusion. 



Spring Fires are very injurious to trees, and especially 

 tender seedlings, for trees in the spring of the year are 

 full of sap, and can endure but little heat. 



Summer and Autumn Fires generally run deep into 

 the ground, and if the soil is very dry and of a peaty nature 

 burn off the roots of the trees. The result of this is that 

 the trees are blown down in great confusion, and form 

 what are known as "fire falls." Where a tluck growth 



