232 Forestry Quarterly. 



furnished mostly by three species, namely Lodgepole Pine, form- 

 ing about 60 per cent, of the stands; Englemann Spruce, forming 

 35 per cent. ; and Douglas Fir, forming 5 per cent. About one- 

 half of the mature forest is composed of mixed stands of these 

 three species. The remaining half is made up of approximately 

 pure stands in which Lodgepole Pine covers three-fifths and 

 Engelmann Spruce two-fifths of their area. 



The author divides the mature forest into three site classes. 

 Site I includes the smooth slopes on the border of the prairies, 

 the bottoms of the valleys, and the lower gentler slopes in the 

 mountains. The soils are comparatively deep and well drained. 

 Formerly more or less extensive stands of Douglas Fir existed 

 along the margins of the prairies, but, having been subjected 

 to repeated fires, they are now much reduced and are not of rela- 

 tively great commercial importance. The stands here are usually 

 open and park-like, but the volunteer growth is fairly good when 

 not kept down by fire or grazing. In most valleys of the foothills 

 and farther up in the mountains, Site I is occupied by pure stands 

 of Engelmann Spruce, frequently interspersed by scattered Lodge- 

 pole Pine, Douglas Fir, Balsam Poplar, and Alpine Fir. The 

 spruce stands are occasionally replaced by those of pine, but this 

 can be traced to the influence of fire- The crown cover of the 

 spruce stands is usually rather dense, casting a heavy shade and 

 consequently the woody undergrowth is sparse, but the large 

 amount of soil moisture leads to a luxuriant growth of Sphagnum 

 and other mosses. The volunteer growth of the spruce is found 

 chiefly in the more open places in the stands. 



Site IT includes the slopes above Site I, and it extends as high 

 up the slopes as the soil remains moderately deep. The ground 

 is drier than in Site I and the more open character of the crown 

 cover, especially where pine predominates, leads to a better de- 

 composition of the humus, and thus reduces the raw soil condi- 

 tion prevailing in the Alpine habitats of Site I. This site class 

 apparently occupies the largest area of the mature forest. In this 

 site mixed stands of pine and spruce or pure stands of each 

 species are in control. Douglas Fir is a more frequent associate 

 of the spruce here than in Site I. The Alpine Fir, of inferior 

 quality and size, is regularly mixed in with all of the stands. The 

 forest as a whole is even-aged and uniform in character, doubt- 

 less originating from fire. The boles of the trees are slender and 



