FORESTRY 423 



more wood, but it is poorer in quality because the lower 

 limbs are allowed to develop and the wood is full of knots. 



130. Protection of forests. The protection of forests is 

 one of the most difficult problems of forestry, for it involves 

 the passing of laws and their enforcement, and the hearty 

 cooperation of communities. This is especially true of pro- 

 tection against fire, which is the greatest enemy of the 

 American forest, and is mostly the result of ignorance, care- 

 lessness, or indifference. The fierce fires in the white pine 

 regions of Michigan, Wisconsin, and Minnesota have become 

 familiar, and sometimes they involve extensive destruction 

 not only of valuable trees, but also of human lives. In the 

 great Minnesota fire of 1904 it is reported that 600 lives 

 were lost. An investigation of the causes of these recurring 

 forest fires has shown that sparks from passing locomotives 

 are the chief cause. It is evident that this cause of fires 

 can be controlled if public sentiment becomes strong enough. 

 Another prolific cause of fires comes from the carelessness 

 of campers and hunters, a cause that is troublesome to check. 

 Farmers often " clear the land " by fire, and carelessness or 

 lack of judgment may result in permitting the fire to extend 

 into the adjacent forest. The effect of a fire differs in its 

 destructiveness. It may involve only the canopy ; it may 

 run over the surface of the soil ; or it may be fierce enough 

 to burn the humus of the soil. In any case, the forest is 

 crippled, and in the last case not only are the trees destroyed, 

 but the soil is no longer fit for forest growth. 



The danger of hard freezing is also to be considered, for 

 it may kill the buds, crack the stems, and upheave the 

 young plants. Frost cracks in lumber show that damage 

 from this cause is often serious. The trees cannot be pro- 

 tected from such a danger completely, but a dense canopy 

 reduces it, and a thick litter of decaying leaves (humus) on 

 the forest floor is still further protection. Damage is also 

 done by violent winds, hail storms, sleet, and snow, but 



