235 



An absolute essential to good soil is the presence of humus. It not 

 only increases the amount of available plant food, but also affects the 

 physical condition beneficially. Surface fires burn out this humus and 

 destroy the leaf mulch from which it is formed. The results of this 

 are worst on limestone and sandy soils, that are naturally hot and dry 

 and become sterile, and on clays, which harden and bake. In every 

 case the fertility and capacity to retain moisture are reduced. This 

 damage to the soil will always show in a decrease in the vitality and 

 rate of growth of the trees. 



The damage to reproduction is very great; in fact so great that 

 where fires are prevalent reproduction is entirely lacking. Not only 

 are the many seeds lying on the ground destroyed, but the small seed- 

 lings, often unnoticed by the casual observer, are burned beyond re- 

 covery. If the seedlings are large enough and the fire light, the roots 

 may survive and send up many small sprouts, which are often weak 

 and are not a good basis for a thrifty stand. 



Young growth of three or four inches in diameter or over, is seldom 

 killed outright by light surface fires but is usually injured to some 

 extent, especially at the base of the trees. Even large trees are grad- 

 ually hollowed out at their bases by constantly recurring fires. Then, 

 too, a dead log or a pile of brush around the base of a big tree will often 

 cause such a hot fire that even the thickest bark will be burned through. 

 These scars not only w^eaken the tree mechanically but also form an 

 easy entrance to insects and rot-producing fungi. These infested trees 

 then serve as places for the propagation of various tree-enemies which 

 in time may spread to the healthy specimens. All forms of disease and 

 insects are more prevalent in forests where the vitality of the trees has 

 been lowered by frequent fires. 



The benefits that are sometimes supposed to be derived from surface 

 fires are of at least very doubtful value. The woods are often burned 

 over with the idea of improving the grazing. By burning every year 

 the brush may undoubtedly be kept small, but it will be increased in 

 quantity, for where one small tree is killed five to ten sprouts take its 

 place. With succeeding fires, the sprouts continue to decrease in qual- 

 ity and increase in numbers. Many weeds and bushes also come in 

 readily on burned soil, and the quality of grass that thrives under these 

 conditions is inferior. If it is thought necessary to convert a woodlot 

 to pasture land with scattered trees, the result can better be accom- 

 plished by clearing with the ax and grazing a large number of cattle 

 on a small area until the brush is killed. 



Accidental fires are started by sparks from railroad locomotives and 

 by hunters, campers, smokers, and others who are careless in the use of 

 fire in the woods. They also sometimes spread from fires started by 



