GENERAL CONDITIONS 89 



are apparently unfit. But the soil seems to be secondary in 

 importance to the climate. In other words yellow pine is now 

 occupying the foothill region of the Rocky Mountains not 

 because the soil conditions are particularly favorable but because 

 it has been more successful than any other western species in 

 adapting itself to the cKmatic conditions which characterize the 

 foothill region. 



Western yellow pine is so predominant within the type that 

 the other species which sometimes occur with it may be briefly 

 disposed of. On the lower edge of the type where the foothills 

 run out into the plains pinon and juniper advance a short dis- 

 tance into the type. On the upper edge or on north or east slopes 

 within the type Douglas fir, lodgepole pine, western larch, and 

 Alpine fir sometimes occur but all these species are typical of 

 climates cooler and moister than that of the yellow pine t3^e. 

 Hence for the present purpose the t3T)e may be said to be uni- 

 formily pure in composition. The other species are never of 

 great commercial importance. 



Damage is confined to four main causes, fire, insects, fungi and 

 wind. Of these the most active, the most serious, and yet the 

 easiest prevented is fire. The white man has adopted the 

 Indian's habit of frequent burning so that there is scarcely an 

 acre of the type that has not been burnt over at one time or 

 another. The danger is the more insidious because the apparent 

 damage done is small. The mature trees are thick barked, crown 

 fires are rare and a fire seems to merely burn up old grass and use- 

 less Htter. But countless young trees are killed in this way, the 

 soil is impoverished and an investigation reported by T. T. 

 Munger in the Proceedings of the Society of American Foresters 

 for April, 1914, shows conclusively that serious harm is done the 

 mature timber. He concludes that, " each surface fire, no matter 

 how light, kills a merchantable tree to each two or three acres, 

 fire scars 42 per cent of the remaining merchantable trees so that 

 they may fall victims to the next high wind or surface fire, and 

 ' pitches ' the butts of a large proportion of the best trees." 



But more serious in the long run than this direct damage is the 

 indirect loss thru the trees being weakened by fires so that they 



