G8 BOTANICAL SURVEY OF THE CfEUR d'alENE MOUNTAINS. 



Ill the majority of instances these are not burned, they are simply 

 cooked, and the lower portion of the trunk, which is always more or less 

 buried in a mass of dead and decaying- pine needles, suffers the same 

 fate. Only when a tree is reached having pitchy roots or gum cracks 

 does it burn up, and then seldom completely. 



The fire resisting power of the trees, both in species and individuals, 

 varies greatly. The factors of safety lie in a thick, nonresinous bark 

 and in roots which penetrate deeper than the lower limit of the humus. 

 Among the trees that occur in the White Pine belt the Douglas spruce 

 resists fire the longest and Mertens's hemlock the least. 



The fires in the Yellow Pine Zone spread with greater rapidity than 

 in any of the other sections. The country is open and the ground 

 more or less covered with grass, through which the fire runs. As the 

 growth of grass is thin, the duration of the fire in any locality is short, 

 and neither the yellow pine nor the Douglas spruce suffers very much 

 the first few times. Where dense groves of black pine and tamarack 

 exist there is a thick layer of pine needles, ami the effects of the fires 

 on them are much the same as in the White Pine belt. When the fires 

 occur among the subalpine firs or along the crest line of the ridges, 

 there is commonly a strong breeze accompanying them and fanning 

 the flames. A clean sweep is pretty apt to be made in such cases. 

 The subalpine fir does not well resist the lire, as the resin vesicles in 

 the bark burn readily and cook the wood. 



The after results of a fire on the timber are various. In the White 

 Pine belt every tree that has been exposed to a fair contact with the 

 smoldering, redhot humus dies. In the Yellow Pine section the tam- 

 arack and Douglas spruce trees that survive are almost certain to 

 develop gum cracks, which unfit large portions of the tree, if not the 

 whole, for use. The yellow pine develops pitch streaks and spots 

 where the fire has touched the bark most severely, but in general this 

 tree, owing to its very thick and nonresinous bark, suffers less than 

 any other species. The gum cracks and pitch streaks which come as 

 the after effects of the tires, even if the tree is not killed, pave the way 

 for a burning of the individuals so affected at the next conflagration. 



The trees in the White Pine belt soon begin to decay after the fire 

 has passed through. The hemlocks always rot first at or closely 

 below the lower portion of the crown of the mature trees, the others 

 at the root. Two or three years after a fire the tops of the hemlocks 

 begin to drop off ami the tall, dead spires of white pine, spruce, fir, 

 etc., begin to fall down. In six or seven years from the time the fire 

 first swept through there is a sufficiency of debris on the ground to 

 furnish material for a fresh conflagration. In the meantime a growth 

 of saplings has sprung up, and the forest has become so dense with 

 the mass of uprooted trees and vigorously growing saplings as to be 

 quite impassable. For the second time fire is applied. There is now 

 no humus, only woody litter. The fire, fanned by the free access of 



