Current Literature. 233 



comparatively free from branches and they can furnish a larger 

 proportion of clear lumber than the trees of the other sites. 



The steeper slopes above Site II, where the dryness and thin- 

 ness of the soil, and other factors, make the production of mer- 

 chantable timber impossible, or very limited in extent, are classed 

 as Site III. The forest for the most part consists of even-aged, 

 very dense stands of Lodgepole Pine with only the largest and 

 best trees over ten inches in diameter. On the northern and east- 

 ern exposures, however, mixed stands of pine, spruce and Alpine 

 Fir frequently occur. The latter species is the commonest asso- 

 ciate of the pine and its reproduction forms the largest propor- 

 tion of the volunteer growth under all of the stands. 



As stated above, three-quarters of the forest area of the Rocky 

 Mountains Reserve has been burned one or more times and is 

 now occupied by second growth, over 90 per cent, of which is 

 Lodgepole Pine of various age classes, the remainder being 

 mostly Engelmann Spruce, or in the foothills, poplar. The pre- 

 dominance of pine reproduction after fire is due to the persistence 

 of its cones, coupled with the long continuance of the germinat- 

 ing capacity of the seeds, thus leading to an accumulation of 

 seeds for the seedbed which the fire prepares. The fire also acts 

 directly by accelerating the opening of the cones. In general, 

 the heavier the fires, the more rapid and denser the reproduction, 

 since the seeds are brought to the ground more quickly and the 

 soil is more completely exposed. In the case of spruce, on the 

 other hand, the fire kills the seed both on the tree and on the 

 ground, and the seed-producing tree is more readily killed than 

 the pine- The spruce reproduction takes place on the moist 

 humus covered sites, which escaped the full effects of fire from 

 seed trees left alive, or from seed blown in from an adjacent 

 green forest. When a fire in a pure spruce stand kills all of the 

 seed trees, and when no pine seed trees are present, the grass 

 which temporarily occupies all burned over areas becomes perma- 

 nent and a meadow is formed. 



In regard to silvicultural methods in the mature forest, the 

 author suggests for the pure spruce stands the strip system and 

 the selection system. The present regulation of cutting nothing 

 below the ten inch stump-diameter limit, even when observed, 

 does not leave enough trees effectively to seed up the area, and 

 those left are usually wind-thrown. In many cases where cut- 



