FOREST SUCCESSION IN THE CENTRAL ROCKY MOUNTAINS 589 



cases and in many similar ones, however, the direct seeding of forest 

 trees has been an absolute failure. The only habitats in which success 

 has resulted from direct seeding, namely, the Douglas fir type of the 

 Arapaho Forest and the yellow pine forest of the Black Hills, were 

 areas from which the climax forest had been removed by lire but a few 

 years before, and on which the soil conditions had undergone little, if 

 any, change. So I think it should be evident that the forester, when 

 contemplating artificial forestation, must have a clear conception of the 

 developmental stage of the site. This is summed up in our general 

 instructions by the very simple statement that the site proposed for 

 reforestation work should show clear evidence of having borne a forest 

 at some time in the not too distant past. 



Now, as I have stated, the forester is primarily concerned with 

 subseres, or short-lived successions, in which there is involved no great 

 change from the conditions which produced the climax forest. Any 

 one who has given this matter a moment's thought, however, knows 

 that an almost imperceptible change in the conditions induces a new, 

 or at least changed, society of the herbaceous layer. The grasses, 

 herbs, and shrubs, and even some trees which we most particularly do 

 not want, are waiting like flies on a screen door, and the moment that 

 door is opened in they rush. In considering some of the problems 

 which this situation presents to the forester, it will be well to take up 

 tlie various climax associations separately. 



We may dismiss the Juniperus-Pinus formation with the simple 

 statement that, owing to its xerophilous character, this association 

 never has the character of a true forest. The shrub and herbaceous 

 societies within the formation are always prominent, and it is doubtful 

 if the amount of cutting which we are likely to do in this formation, or 

 even iires, which would injure the dominant species least of all, will 

 materially alter the nature of the formation. Changes occur very 

 slowly in such a formation as this, and there has not been time to 

 determine what trend they will ordinarily take after systematic cutting. 



In the yellow pine forest there is a distinct problem of succession 

 following each fire or cutting, which creates a new subsere. Fortu- 

 nately, fires rarely, and cutting never, entirely destroy the climax 

 formation over large areas. There is, therefore, usually no question as 

 to the availability of seed of the yellow pine. Either of these methods 

 of partial denudation, however, may be destructive of much of the 

 young growth of pine, and releases from shade and from competition 



