VO-i JOURNAL OF FORESTRY 



two previous seasons and is, for the most part, eliminated shortly after 

 its appearance by adverse climatic factors, chiefly frost. 



"A surprisingly large proportion of the reproduction produced, even 

 on the most favorable sites, is killed during the first three years of its 

 growth by causes other than grazing. Frost and bark-eating mammals, 

 notably gophers, field mice, and rabbits, are mainly responsible for such 

 mortality. 



"The average maximum height at which sheep browse is approxi- 

 mately 42 inches. Sprouts averaging 45 inches in height are found to 

 be exempt from destructive browsing by sheep, and, since the annual 

 rate of height increment of the aspen reproduction averages about 15 

 inches, sprouts three years of age are exempt from serious injury by 

 sheep, and those from 4 to 5 years of age are free from serious injury 

 by cattle. 



"Aspen is practically unable to reproduce under its own shade, and 

 the best means of obtaining vigorous and dense reproduction, and at 

 the same time of harvesting the timber economically, is to clear-cut the 

 lands or to thin the stand heavily." 



A new method is proposed to dispose of the brush in logging, namely, 

 to place the unlopped tops around the stumps so as to protect the 

 sprouts. 



"In three or four years, when the reproduction is practically exempt 

 from serious browsing, the brush is for the most part decayed and out 

 of the way. Furthermore, such a disposition of the brush does not 

 make the danger from fire any greater." 



The practical deductions from this study for the management of 

 grazing in aspen type to secure best results for the two objects, meat 

 and wood, are to adopt a clear-cutting system and to permit cattle 

 rather moderately, but to exclude sheep entirely for the first three 

 seasons after logging or at least graze only lightly. "But the sheepman 

 who will graze his sheep very lightly over the choicest of forage, such 

 as invariably becomes established on clear-cut or heavily thinned aspen 

 lands, has not yet been discovered." 



B. E. F. 



