FOREST SUCCESSION IN THE CENTRAL ROCKY MOUNTAINS 591 



In the southern part of Colorado lodgepole pine has not invaded 

 this formation. Apparently, the conditions are not suited to the pine. 

 Perhaps also the fires have been less recurrent. At any rate, the prob- 

 lem is different. There occur in the remaining Douglas fir forests 

 usually a few specimens of yellow pine, limber pine, and Engelmann 

 spruce, and in some localities blue spruce. Aspen is almost always 

 present as a subdominant, and after a destructive fire this broadleaf, by 

 reason of its ability to produce root suckers, almost immediately takes 

 possession of the ground. In the course of a few years seedlings of 

 Douglas fir and its associates begin to appear, and these without diffi- 

 culty develop under the cover of the aspen. Douglas fir will usually 

 predominate at the completion of the sere, simply by reason of its 

 perfect adaptation to the conditions. When this development is to occur 

 after a heavy or complete cutting of the forest, the forester is, of course, 

 concerned with eliminating the inferior associates as far as possible and 

 with reducing the retarding influence of the aspen subclimax. In one 

 case which has been quite carefully studied the following facts have 

 been noted : 



In the second year after the cutting a very good crop of all conif- 

 erous seedlings was secured. Douglas fir was in preponderance on 

 areas where the cutting was moderate ; where no cutting had been done 

 Douglas fir and Engelmann spruce occurred in about equal numbers ; 

 where all the trees had been removed limber pine reproduction was 

 nearly as abundant as that of Douglas fir. In this clear-cut area aspen 

 sprouts were very numerous and vigorous, but there were very few of 

 them in the half-cut forest. In all areas there was a larger crop of 

 seedlings during the third than during the second season after cutting, 

 although the latter had not been a seed year. These facts point to the 

 following: (a) The seeding of a clear-cut area is evidently not, in the 

 main, from the side. The large number of limber pine seedlings occur- 

 ring in groups indicates that the seeds are either brought in by birds and 

 cached or cached by mice or birds before the cutting was done. In 

 view of Dr. Hoffman's findings with Douglas fir in the Northwest, I 

 incline to the belief that much seed must be stored in the forest floor, 

 and that it is ready to germinate within a year or two after the proper 

 conditions have been created, (b) It is evident that clear cutting gives 

 a great advantage to aspen sprouts, (c) The question of the elimina- 

 tion of inferior associates, limber pine in particular, is not solved by 

 removing the limber pine seed trees. It may be that we shall find that 



