24 BULLETIN 141,. U. S. DEPARTMENT OF AGRICULTURE. 



under its own shade,, Light thinnings are of some value, but a very 

 large percentage of the sprouts soon succumb because of insufficient 

 sunjight. The surviving sprouts are forced into intensive competi- 

 tion with various shade-enduring, aggressive, shrubby, and herba- 

 ceous species. This, coupled with inadequate light, renders the 

 sprouts weak and not uncommonly diseased. If the slender speci- 

 mens are not killed outright by fungous attacks, sooner or later 

 they fall easy victims to the wind. 



The average stand of prop timber, the diameter breast-high of which 

 does not exceed 10 inches, consists of about 480 trees per acre. To 

 insure a stand of this number of trees at the average rate of mortality 

 of the sprouts, a stand of 2,500 specimens per acre the third year 

 after cutting is sufficient, even though the lands are moderately 

 grazed by cattle or sheep after the terminal shoots are no longer 

 subject to browsing. In practically any type of aspen properly 

 protected from stock, the stand following clear-cutting will generally 

 be 2,500 specimens per acre. Thus in the case of the plot pictured 

 in figure 2 of Plate V, representing the sprouting capacity following 

 the clear-cutting of an 80-year old stand, there are more than 30,000 

 specimens at the end of the third year. The sprouting appears to 

 be quite as vigorous when younger stands are clear-cut. 



METHODS OF BRUSH DISPOSAL. 



Various methods of disposing of the brush are in practice, some 

 of which tend to expose the sprouts unduly and others to protect 

 them. Piling and burning the brush is the most popular; but this 

 method, owing to the complete opening up of the lands, is responsible 

 for highly destructive browsing, especially by sheep, the result being 

 that the stand is materially thinned and correspondingly mutilated. 

 The method appears to endanger the establishment of the stand 

 approximately in proportion to the number of spaces burned. 



Experiments have been made in scattering the brush over the cut- 

 ting without lopping the nonmerchantable parts. The method which 

 has given the best results, and which at the same time lends itself to 

 general field practice, is that of scattering the unlopped ones about 

 the stumps, the butts of the discarded portions being placed next 

 to the stumps in such a manner as to have the branches extend out 

 in all directions from the stump. Since the major portion of the 

 reproduction originates from superficial roots near the parent plant, 

 the tops are located where they will afford the greatest possible 

 protection to the new sprouts. 



This light screen of unlopped branches, arranged as described, is 

 surprisingly effective against repeated visitations by sheep during 

 the first three seasons after the cutting, which is the most critical 

 period. While, to be sure, there is usually not a sufficient supply of 



