82 SURVEYS OF FOREST RESERVES. 



by rugged ridges with abrupt slopes. The soil is unfit to raise any- 

 thing but grass or trees, for the severe climate precludes agriculture 

 altogether. This region has hitherto made little or no contribution to 

 the settlements eastward except in the matter of railroad ties, con- 

 siderable numbers of which have been cut from the Xorth Fork of Sun 

 Eiver, and driven down it for the use of a branch of the Great Northern 

 Railroad. 



THE FOREST, BASTBKX SLOPE. 



The forest on the eastern slope consists principally of Douglas tir (red 

 flr), Eugelmann spruce, and lodge-pole pine. It is generally open, and 

 in places is broken by the bnrns of very extensive fires. In the valley 

 of the North Fork, lodge-pole pine, with a mixture of spruce in the 

 moister situations and of alpine flr higher up, constitutes the bulk of 

 the forest, which in many places is comparatively dense and uninjured 

 by fire. 



The lodge-pole pine, which has furnished the larger number of ties 

 cut from this region, reaches the following average measurements: 

 Height, 70 feet; diameter, 10 inches; length of clear trunk, 20 feet. 

 This tree probably owes its wide distribution here as elsewhere to the 

 prevalence of fires in the past. It is slow of growth, with admirable 

 reproductive powers, and forms by far the greater portion of the forest. 



The spruce is found both on high and low ground, and owes its dis- 

 tribution to moisture and not to altitude. It has average measure- 

 ments as follows: Height, 80 feet; diameter, 18 inches; length of clear 

 trunk, none. Valuable as a lumber tree because better material is 

 lacking, the spruce occurs in restricted numbers compared with the 

 lodge-pole pine, although the total amount of it in the watershed of 

 Sun Eiver is large. 



Alpine fir lives normally at high altitudes, but in places follows the 

 streams to comparatively low situations. At great elevations it usually 

 forms the bulk of the forest, and often exceeds in numbers all other 

 species even at moderate heights. Its average dimensions are : height, 

 50 feet; diameter, 12 inches; length of clear trunk, none. 



FIRE, EASTERN SLOPE. 



The eastern slopes of the main range in the northern . part of this 

 reserve, and of the spur which bounds the watershed of the Xorth 

 Pork of Sun River farther south, have been practically cleared of tim- 

 ber by fire over the greater portion of their extent. The contrast 

 between the present condition of this unprotected area and the un- 

 burned forests of the same slope of the Rockies farther north, where 

 the Blackfoot Indian Reservation has hitherto tended to prevent the 

 general access of prospectors and hunters, is as striking as it is in- 

 structive. 



In the broad and comparatively iiat valley of the North Fork the 

 original forests have been driven from the more level lands, for 12 

 miles above the junction with the South Fork, by the ravages of ancient 

 fires. To a less extent, on the Middle Fork, open grass lands have 

 been produced in the same way. Otherwise these valleys are well tim- 

 bered. The prevailing character of their forests has been determined 

 here, as in many other places, almost exclusively by fire and the amount 

 of rain. 



Throughout the larger part of the area under discussion the body of 

 decaying vegetable material under the trees is slight, and except for 



