EEPRODUCTTON OF WESTERN YELLOW PINE. 113 



with the principles formulated by recent investigations. Only on 

 rare occasions clo two of the methods occur side by side under 

 comparable conditions. Lopping, though here distinguished from 

 pulling, is but a by-product of the latter method. The conditions 

 created are exceedingly variable, sometimes approaching pulled tops 

 and sometimes scattering. No serious effort has been made to de- 

 termine the merits of lopping in comparison with the other two 

 methods. 



In the 1920 counts of Table 25, only Groups 6 and 8 contain 

 data on lopping and scattering. These methods are not directly 

 comparable with each other or with pulling, because they were 

 applied under varying conditions, and therefore the only means 

 of comparison is through the medium of parallel control plots on 

 natural areas. In Group 6, both lopping and pulling excel the 

 natural or non-brush-covered plots. This is due to the fact that 

 practically no herbaceous vegetation occurs either in the brush or in 

 the open, and thus the seedlings derive the full benefit of the 

 favorable influences of the brush. As a general rule, under such 

 conditions, the seedlings in the brush are larger than those out- 

 side ; but in the case of lopping, the relation is reversed in this par- 

 ticular instance. In point of numbers the difference between lop- 

 ping and pulling, when compared with the respective control plots, 

 is not sufficient to justify any conclusions. In Group 8 scattering 

 shows a distinct superiority over pulling. In this case the grass 

 was closely grazed on the open areas and in the scattered brush, 

 but it was scarcely touched in the tops. 



The coimts made in 1921 furnish a better comparison, although, as 

 in 1920, it was not always feasible to compare the various methods 

 directly. In Group 8 the superiority cf scattered brush over pulled 

 tops is demonstrated even more strikingly than in 1920. In this in- 

 stance the scattering and corresponding controls are represented by 

 the same plots in 1920 and 1921, but in the case of pulling new plots 

 were selected in order to secure more typical conditions. In Group 

 9 pulling appears to have a small margin, over scattering on the bare 

 areas, but on grassy areas there is no pronounced difference. 



In the absence of sufficient data for a direct comparison, the best 

 means of approaching a decision as to the relative merits of the scat- 

 tering, pulling, and lopping is to consider the physical conditions at- 

 tainable under each method. 



Pulling tops creates exceedingly variable conditions. Where the 

 crown is dense, the mass of branches and needles effectively bars the 

 entrance of pine seedlings for at least 10 years. Where the crown is 

 open, the surface of the ground is but little affected. Often both 

 extremes are encountered in different parts of the same top. Usually 

 904°— 23 8 



