FOEEST CONDITIONS. 21 



The general arrangement and distribution of these species is simple. At 

 elevations of 5,500 to 6,000 feet limber pine, small proportions of yellow pine, and 

 scattered copses of red fir form thin fringes of forest, or, on northern slopes, fairlj- 

 well-stocked stands. From 6,000 to 8,000 feet lodgepole pine forms the great mass 

 of the forest. It occurs either in practically pure growths, generallj^ closely stocked, 

 or mixed with red fir and Engelmann spruce; the red fir is particularly abundant 

 on dry, rocky slopes; the Engelmann spruce is most common along the canyon 

 bottoms, in places with considerable seepage or where the lodgepole pine has 

 attained an age of 150 years and upwards. Above the 7,800-foot level the lodgepole 

 pine thins out and is replaced by white-bark pine, subalpine fir, and Engelmann 

 spruce, which together constitute the subalpine forest zone. The broad-leafed 

 trees — aspen, cotton wood, and arborescent willows — are mostly confined to the 

 canyon bottoms, and are seldom found above the 7,500-foot level. 



The timber line is at an elevation of about from 9,300 feet on northern and 

 western slopes to 9,800 feet on southern exposures. It rises, however, as the eastern 

 edge of the reserve is approached, until in some places along the eastern verge of" 

 Beartooth Plateau it reaches 11,000 feet. Near the timber line Engelmann spruce 

 is found in greater abundance and vigor than any other species. Next comes the 

 white-bark pine, while the subalpine fir generally occurs at lower altitudes. Both 

 the spruce and white-bark pine dwindle rapidly in stature as elevation is attained, 

 until at their uppermost limits they are mere depressed shrubs. 



Within their altitudinal limits the species, except the white pine, are found in 

 the timbered area in all parts of the reserve. Their relative abundance, however, 

 varies greatly. The limber and yellow pines are most common in the foothills in 

 the northern townships; the yellow pine, however, forms in all cases a very small 

 ratio of the timber in any locality and is practically lacking in all of the interior 

 areas. The white pine occurs chiefly in the bottoms of Davis ,Creek, an affluent of 

 West Boulder River, and in the Slough Creek bottoms in T. 10 S., R. V2 E. It is a 

 very rare species in either locality, only scattered trees occurring, set in mixed stands 

 of lodgepole pine, red fir, and Engelmann spruce. The white-bark pine is found 

 throughout the subalpine zone. Usually it forms only a small proportion of the 

 forest, but occasionally, as in the eastern portion of Hell Roaring Creek Basin, it 

 becomes so abundant as to constitute 75 to 85 per cent of the stands. 



The lodgepole pine is very plentiful; it forms fully 75 per cent of the forests 

 below the subalpine zone, and, excluding the lower areas bearing red fir and limber 

 pine, will amount to 90 per cent. It frequently forms nearly or quite pure 

 growths, especially while in the sapling stage, and in mature stands where the 

 forest is beginning to assume its normal composition seldom falls below 36 to 50 per 

 cent. Its relative abundance and preponderance are wholly the result of past fires. 



The red fir extends throughout the lower areas of the reserve. It occurs in 



