EESTOCKAGE. 29 



scantiness of the young growth in the subalpine forest is the low ratio of cone 

 and seed production, characteristic of all subalpine trees when growing at high 

 elevations. Some of the species, as the white-bark pine and subalpine fir, do not 

 readily bear cones nor mature their seeds at any altitude in this region, and as most 

 of the subalpine tracts are situated well above the limits of growth for the lodge- 

 pole pine, this tree, with its abundant seed production, does not become a factor in 

 the restockage. The most prolific of the subalpine trees is the spruce, which in 

 time is bound to form the larger proportion of this type of forest, and will be 

 followed by the subalpine fir as taking second rank. The great snow banks, which 

 each season pile up at these altitudes, likewise hinder restockage, as they bend 

 and break multitudes of young trees beyond recovery. 



The uppermost line of forest presents a ragged and wavy line, apparently 

 advancing and receding from time to time, but there are no very definite indications 

 of any change in the altitudinal limits of the general timber line within the life of 

 the present forest. If any changes are now taking place they are wholly in the 

 direction of an upward movement — ^that is, there is a tendency toward higher 

 mean temperatures and less precipitation in the subalpine and alpine areas, with 

 corresponding elevation of the timber line. 



In the great mass of the forest between the low levels occupied by the wood- 

 lands and the subalpine zone reproduction is abundant where not interrupted by 

 repeated fires over the same area. In the veteran stands where the composition of 

 the forest approaches normal — that is, a preponderance of Engelmann spruce at the 

 upper and intermediate levels and of red fir at the lower, young growth is present 

 in sufficient quantities to maintain the density of the stands and their present com- 

 position. In the veteran stands composed of lodgepole pine young spruce and red 

 fir are gradually regaining ground that they formerly occupied. In young and 

 middle-aged stands the lodgepole pines are set so close that there practically can be 

 no additions of any other species. The restockage on ground denuded by fire is 

 nearly always composed of lodgepole pine, unless the tract is situated at low 

 elevations where well-advanced growths of red fir prevailed on adjacent areas and 

 lodgepole pine formed but a small percentage. In such cases the young growth 

 is chiefly red fir. On tracts denuded by logging operations mixed stands composed 

 of red fir, spruce, and lodgepale pine are apt to come in from the first, even if the 

 pine forms the larger proportion of the surrounding forest. In some cases, at 

 the lowest altitudes, aspen comes in and forms extensive and long persistent 

 gi'owths, whether the tract was denuded by fire or cut. The general rule, 

 however, is that where openings are made in the forest either by fire or ax 

 between altitudes of 6,400 and 7^900 feet, the species of inferior value, here the 

 lodgepole pine, will form by far the largest percentage of the restockage, and will 



