592 JOURNAL OF FORESTRY 



a very light cutting will cause the Douglas fir seed to germinate without 

 allowing sufficient light and heat for the more exacting limber pine. 

 This is a very neat problem, on which a great deal of work must be 

 done. 



Now a brief word about our Engelmann spruce. In part, its his- 

 tory is very similar to that of the Douglas fir formation, in that after 

 repeated burnings the lodgepole pine subclimax succeeds, and after less 

 severe burning the aspen. This is not true, however, of the higher or 

 strictly subalpine zone of the spruce formation. Here in the primary 

 succession Engelmann spruce is preceded by either a Pinus-flexilis or 

 Pimis-aristata subclimax. Similarly, in the subsere, after severe burn- 

 ing, it is usually one of these two remarkably wind-resistant pines 

 which begins the succession of trees. These come in one by one until 

 all age classes are represented. The nature of the invasion leads me to 

 believe that the seed, which for both trees is quite heavy, is transported 

 mainly by jays, perhaps in part by rodents. With any of these sub- 

 climax species Engelmann spruce, because of its tolerance, can compete 

 readily whenever the conditions necessary for the final stage of succes- 

 sion have been created. 



In the subsere brought about by cutting an entirely different situa- 

 tion exists. The climax formation is typically a mixture of spruce and 

 alpine fir, the latter varying, according to site, from an insignificant clan 

 to an important society. So nearly the same are the requirements of 

 the spruce and fir that there is much doubt as to whether the latter is 

 favored by a little more moisture or will simply tolerate a little more 

 shade, a little more soil acidity, and a little less heat. Be that as it may. 

 we find where the fir exists at all that after a very light cutting its 

 seedlings preponderate in the reproduction. Generally a heavier cut- 

 ting seems at least to give the spruce equal chances. Because of the 

 great value of spruce forests for protection, it is not always, however, 

 allowable to cut as heavily as might be desired for the immediate re- 

 turn of the spruce. I think you will see, therefore, that here again the 

 forester is confronted with a problem whose correct solution depends 

 upon a detailed analysis of the factors which control the composition 

 of the plant community. There is here little chance for the develop- 

 ment of a subclimax formation, but there is great possibility, if the 

 denudation in cutting does not go quite far enough, that the more 

 valuable spruce will be replaced for a generation by the much less 

 valuable alpine fir. 



