THE MONTANE ZONE lo<* 



providing good drainage but where there is sufficient moisture 

 during the growing season. Unlike the spruce it seems to shun 

 the wetter soils. Groves of the alpine fir often shelter snow 

 drifts until August or even through the entire year. 



This fir endures the most rigorous climate. Its temperature 

 range must extend from -60 to over 100 degrees for short periods, 

 with the prevailing summer temperatures between 30 and 85 

 at 6,000 feet elevation. It is the temperature which appears to 

 be the special controlling factor in the distribution of the alpine 

 fir, both local and general. Moisture likewise is influential but 

 is likely never to be absent during the growing season in the 

 zone where this species reaches its best development. 



The alpine fir seldom grows in dense stands, but appears 

 more or less scattered and in groups. Its tolerance, however, 

 makes possible a dense forest which here and there is realized 

 over small areas. The foliage of the crowns is dense, especially 

 in older trees where it is sometimes almost impenetrable, and fre- 

 quently descending to the ground. Young trees may endure 

 shade for years and recover with rapid growth when the dom- 

 inating influence is removed. 



Abies lasiocarpa finds conditions favorable for its growth 

 throughout the Rocky Mountain region from Alaska to Arizona 

 and to some extent in the Cascades and coast ranges. In the 

 southernmost parts of its range its lower limit in altitude is 

 about 9,000 feet. 



Another species forming a large part of the mountain for- 

 ests is the whitebark pine (Pinus albicaulis). It forms some- 

 times pure forests at 7,000 to 8,000 feet in clear orchard-like 

 stands of trees of medium size a foot, more or less, in diameter 

 and about 40 to 50 feet in height. Sometimes the trees of this 

 species in more favored situations between 6,000 and 7,000 feet 

 may reach a diameter of 5 feet or more, but such are rare. Trunk 

 diameters of two to three feet, however, are not uncommon. On 

 exposed, wind-swept situation at all altitudes within its range 

 it assumes a stunted and spreading habit, usually of 5 or 6 feet 

 in height. The white bark pine is the usual companion of the 

 alpine fir and Engelmann spruce, and its characteristically 

 branching tops can be recognized far and near. It enjoys a 

 natural range from British Columbia to southern California and 



