THE EFFECT OF FOREST FIRES IN MAKING A FOREST OPEN AND BROKEN 



A forest of yellow pine in California. Every fire kills some trees, and, if continued, 

 finally destroys the forest. This forest has been opened up and has only a relatively small 

 yield of timber as a direct result of past repeated fires. 



trees die as the result of each fire, and, 

 as the young growth is also killed, the 

 forest becomes more and more open and 

 broken. This explains why in many re- 

 mote forests, where there has never 

 been any cutting at all, the trees stand 

 far apart and the yield in valuable mate- 

 rial is small. Frequently in a virgin 

 forest the yield is not over one-fifth to 

 one-tenth of what it would have been if 

 fires had not occurred. 



In some regions, particularly in the 

 North, there is in the forest a deep layer 

 of decayed vegetable mold, or humus, 

 frequently one to three feet deep. When 

 this becomes thoroughly dry a fire burns 

 slowly and persistently through it, kill- 

 ing the roots of the trees. These are 

 called ground fires and are exceedingly 

 difficult to extinguish. They have been 

 known to smoulder for long periods 

 imder the snow (see photo, page 667). 



The most destructive fires are those 

 which not only burn over the ground. 



but sweep up into the tops and actually 

 consume the crowns of the trees. These 

 are called crown fires. They are com- 

 mon in forests composed of coniferous 

 trees, as the forests of the East and the 

 Lake States and the coniferous forests 

 of the far West. The crown fire usually 

 starts as a surface fire ; but, under the 

 influence of a strong wind or when 

 burning in a mass of old, dry tops or 

 other debris, the flames are carried into 

 the crowns. With conditions just right 

 ihe green crowns are ignited, and a con- 

 flagration develops which sweeps every- 

 thing before it. 



TERRIFIC FIRES WHICH KILLED HUNDREDS 

 OF PEOPLE 



There have been a number of great 

 fires which have attained historic impor- 

 tance. One of these occurred in New 

 Brunswick, in the fall of 1825, on the 

 Miramichi River, during a season of 

 great drought. Many fires of greater or 



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