PINE TREES OF ROCKY MOUNTAIN REGION. 41 



coast form is rather heavy, being about 36^ pounds, while wood of 

 the Rocky Mountain form weighs about 25^ pounds per cubic foot. 

 Tangentially ("bastard") cut boards have a distinctly pebbled 

 appearance when planed. 



In the Rocky Mountain region the wood of this tree is becoming 

 more and more valuable for commercial purposes, which include 

 construction lumber, much used locally, and railway ties. It is also 

 used for corral poles, house logs, and fuel. In the Pacific region it 

 is used principally for these latter purposes. 



OCCURRENCE AND HABITS. 



In the Rockies Pinus contorta occurs on high plateaus and benches 

 in the vicinity of streams, mountain meadows, and lakes, on broad 

 ridges, and on long gentle slopes and bottoms of stream-watered 

 basins at elevations between 7,000 and 11,500 (Map No. 13). North 

 and east slopes are more favorable than west slopes, while south 

 slopes, except in sheltered coves, are least favorable for the growth 

 of this pine. It avoids limestone, but is adapted to dry gravelly 

 soils, seeming to prefer sandy moist ones of gentle slopes, depres- 

 sions, and plateaus, where the largest growth occurs. Stunted forms 

 grow persistently, however, in crevices of solid rock. It forms ex- 

 tensive pure forests, particularly about meadows; on higher, rocky, 

 rough ground it is sometimes associated with Engelmann spruce, 

 aspen, Douglas fir, and alpine fir. 



The lodgepole pine is very intolerant of shade, especially when 

 young, but is able to maintain itself for a long time (from 20 to 50 or 

 more years, or for a longer period) in very dense stands, after which, 

 if wholly relieved from overhead shade, it recovers and grows rapidly - 

 It grows best, however, in full enjoyment of light. Even-aged, 

 dense stands with full top light, such as commonly follow complete 

 destruction of the preceding growth by fire, may thrive for 50 or 60 

 years with little natural thinning out. But the prompt natural 

 thinning out of overtopped trees at earlier stages in uneven- aged 

 stands is proof that this pine is unable to endure longer continued 

 shade. 



This species is usually a prolific annual seeder, bearing large num- 

 bers of cones. The seed has a high rate of germination and persistent 

 vitality. Fertile seeds are often borne by trees only from 6 to 10 

 years of age when growing in the open. In crowded stands cones 

 are borne by trees from 15 to 20 years old. The small light seed is 

 widely disseminated by wind, sometimes being carried 200 yards 

 from the mother trees. Squirrels and birds destroy great numbers of 

 the seeds, but the effect on reproduction appears to be inappreciable. 

 Extension by natural seeding on unburned areas is ordinarily slow, 



