ASPEN REPRODUCTION AND MANAGEMENT 397 



the first three years following the cutting, after which the lands may be 

 utilized by sheep without serious injury to the aspen stand. Three 

 years after cutting, over 90 per cent of the terminal shoots of the 

 sprouts are beyond the reach of sheep, and while the laterals are grazed 

 more or less the subsequent growth and establishment of the sprouts 

 are not seriously impaired. 



Destruction of Sprouts by Rodents 



A large proportion of the sprouts may be killed or more or less se- 

 riously injured by causes other than grazing. Bark-eating mammals — 

 chiefly rabbits, gophers, and field mice, — are responsible for the de- 

 struction of as much as 10 per cent of the stand in some instances in 

 a single season. Much of the bark removal is done under the snow 

 and practically all injury of this kind is inflicted during the first five 

 years of growth of the sprouts. 



CONCIvUSIONS 



It is apparent from the foregoing evidence that reproduction by root 

 suckers is practically the only means by which aspen stands are re- 

 generated in this region. As conditions of climate and other factors 

 that would influence reproduction are practically the same now as they 

 have been for the last few centuries, it seems improbable that seed 

 reproduction has been active for a very long time. That vegetative 

 reproduction should still remain so vigorous is remarkable, when the 

 usual rapid deterioration of coppice of other species is considered. It 

 sems improbable, therefore, that any immediate deterioration in vigor 

 of reproduction is to be expected. 



This being granted, the management of aspen becomes very simple. 

 Since practically all the reproduction is by sprouts, the silvicultural 

 system is obviously clear-cutting, since this gives rise to the maximum 

 number of sprouts. In uneven-aged stands, where the merchantable 

 trees comprise only a portion of the total stands, every eflfort should be 

 made to have a cutting of maximum intensity, since the sprouts are 

 very intolerant and tend to form short crooked flat topped trees 

 which will never become valuable under even moderate shade. 

 Unlike the case of most species managed as coppice there is 

 little choice of the season of cutting. This may safely be left 

 to the desires of the operator since sprouting is fully satisfactory at 

 every season of the year. The rotation under which the stands are 

 to be managed ma\ be determined solel\- ujion the basis of the kind of 



