6 BULLETIN 154, U. S. DEPARTMENT OP AGRICULTURE. 



Alpine fir (Abies lasicarpa), while the relatively short growing 

 season at high elevations does not furnish the total amount of heat 

 which loclgepole needs for its growth. The range of the species is 

 thus limited on one hand by lack of moisture and on the other by 

 lack of heat. 



Lodgepole occasionally endures for short periods extremes of tem- 

 perature varying from approximately 100° F. to —55° F. The 

 growing season of the region is short, since killing frosts are likely 

 to occur until about the middle of June and the first autumn frost 

 comes early in September. In the lodgepole zone frost and snow may 

 occur at any time during the growing season. 



May and June are the months of heaviest precipitation, but in the 

 lodgepole zone much of this is in the form of snow, which usually 

 covers the ground until late April or the middle of June, depending 

 upon the elevation and aspect. 



Too much soil moisture is unfavorable to lodgepole, and good 

 drainage is essential. The tree will not stand a water content of 

 more than 35 per cent in a loam soil and only about half as much 

 in gravel or sand. The best water content is between 12 and 15 per 

 cent, though in gravel it may even fall below 5 per cent without 

 effect upon the tree beyond a decrease in its rate of growth. 1 In 

 respect to their moisture requirements the different conifers of the 

 region may be grouped as follows, those demanding the least mois- 

 ture being placed first: Juniper, limber pine (Pinus fleatilis), yellow 

 pine (Pinus ponderosa), Douglas fir, lodgepole, white bark pine 

 (Pinus albicaulis), Alpine fir, and Engelmann spruce. 



Lodgepole is not exacting in its soil requirements, though it does 

 best on deep, fresh, well-drained agricultural land. It is able to 

 make good growth, however, on shallower, poorer soils, provided a 

 reasonable amount of moisture is available. The typical soil of the 

 lodgepole region is gravelly, with a considerable admixture of loam 

 in valley bottoms and open benches, but with little or none on ridges 

 and steep slopes. Unless lightened by a mixture of sand, gravel, or 

 loam, clays are usually not well enough drained, while limestone 

 soils are apt to be too dry to enable the tree to make a normal growth. 

 In the Big Horn Mountains in Wyoming, for example, lodgepole is 

 rarely found on the limestone soils, though granitic soils immedi- 

 ately adjoining show extensive areas of the lodgepole type. 



LIGHT REQUIREMENTS. 



In relation to light, lodgepole pine exhibits three striking char- 

 acteristics — intoler?nce of any considerable degree of overhead shade; 

 ability to survive for long periods in a badly crowded or suppressed 

 condition in pure, even-aged stands ; and ability to recover and make 



1 Forest Service Bulletin 79, The Life History of Lodgepole Burn Forests. 



