REPRODUCTION OF WESTERN YELLOW PINE. 107 



The above observations agree closely with those pointed out in 

 the chapters on herbaceous vegetation and cutting. There it was 

 found that the seedlings were much larger on stump patches than 

 elsewhere, providing the herbaceous vegetation was grazed down, 

 but that if this vegetation was unchecked it became so luxuriant that 

 the seedlings were far below normal in both size and number. 



The apparent contradiction between results in the 1908 and the 

 1913 experiments is now readily explained. It will be recalled that 

 in the former case brush-covered patches show slightly poorer re- 

 stocking than those on which no brush was scattered, whereas in the 

 latter the brush-covered patches show a decided superiority over 

 the open patches. The difference is accounted for by ground cover. In 

 the 1908 experiment the ground cover, in which rank bunch grasses 

 predominated, was practically undisturbed, but in the 1913 experi- 

 ment it was almost completely eliminated by plowing. In the light 

 of the knowledge gained in 1920, it is evident that if the natural 

 vegetation had not been destroyed in the 1913 experiment, the results 

 would have been similar to those obtained in the earlier experiment. 



Table 25 and Figure 15 also show considerably less grazing dam- 

 age to seedlings in brush than in the open. In fact, practically 

 no damage to the 1919 seedling crop has occurred in the brush up to 

 the end of the year 1921, but in the open spaces an average of from 

 23 to 50 per cent, and in extreme cases 90 per cent, of the seedlings 

 have been recorded as killed or severely injured. On closely or over- 

 grazed areas with no brush cover the damage often approaches com- 

 plete destruction. This explains why reproduction in advanced 

 stages is commonly more abundant along old fallen trees than else- 

 where. In open situations exposed to excessive grazing, practically 

 every seedling is destroyed, but under the protection afforded by 

 the projecting branches of fallen trees a few seedlings have strug- 

 gled through, despite the handicap of competition with grasses. 

 On areas of light ground cover this difference becomes all the more 

 striking. Thus it is found that the beneficial effect that brush has 

 been supposed to bring about is limited mainly to protection against 

 damage by grazing. This protection, however, is only temporary 

 and does not obviate the necessity for grazing control. 



The question naturally arises, " Are the detrimental effects charged 

 against brush and the favorable effects credited to burning perma- 

 nent or only temporary?" An absolute answer to this question 

 can be given only after observations have continued over a long 

 period of years. It should be borne in mind, however, that the 

 1920 data used in Table 25 were secured at the close of the second 

 season or after the period of highest mortality was past (Fig. 1G). 

 Examinations at the end of the third season, October, 1921, show no 



