126 OUR NATIONAL FORESTS 



the slash that is left after logging and allowing 

 these fires to get beyond control. 



Behavior of Forest Fires. Fires behave differ- 

 ently, once they get started, depending upon the 

 character of the timber, the amount of wind, and 

 the degree of inflammability of the forest cover. 

 Ground fires burn the inflammable dry grass, 

 needles, dead twigs, etc., on the ground ; crown fires 

 are much more severe and, being usually fanned by 

 a heavy wind, run through the tops or crowns of the 

 trees; brush fires burn the bushes and dry shrubs 

 from 5 to 10 feet high; timber fires consume the 

 entire forest — crown, stem, ground cover, and un- 

 dergrowth — and usually occur in timber that stands 

 close together. 



Losses by Forest Fires on the National Forests. 

 The results of forest fires naturally vary with the 

 kind and intensity of the fire. Crown and timber 

 fires do the most damage, and ground and brush 

 fires do less. While the ground fires and brush 

 fires seem to do very little damage to the valuable 

 timber, still they may greatly reduce the productive 

 power of the soil and destroy the watershed cover. 

 Severe ground fires may kill valuable timber by 

 girdling the trees. The great fires of August, 1910, 



