REPRODUCTION OF WESTERN YELLOW PINE. 



45 



Table 13. — Effect of cutting, herbaceous cover, and grazing upon survival and 

 development of seedlings. 





Basis, 



square 



feet 



Number 1919 seedlings. 



Per cent 

 large. 



Grazing. 



Month and situation. 





Per 

 square 



foot. 





Killed, 

 percent. 



Injured, per cent. 







Total. 



acre. 



Serious. 



Moder- 

 ate. 



August, 1920: 



Open range — 



Stump patches 



Natural areas 



Inclosure— 



Stump patches 



Natural areas 



November, 1920: l 



Open range- 

 Stump patches 



Natural areas 



Inclosure— 



Stump patches 



Natural areas 



August, 1921:i 



Open range- 

 Stump patches 



Natural areas 



Inclosure — 



Stump patches 



Natural areas 



300 

 800 



200 

 400 



700 

 800 



500 

 400 



400 

 900 



400 

 400 



34 

 224 



17 



139 



33 

 147 



43 

 112 



10 

 75 



1 



94 



0.113 

 .280 



.085 

 .347 



.047 

 .184 



.086 

 .280 



.025 

 .083 



.002 

 .235 



4,900 

 12,200 



3,700 

 15,000 



2,000 

 8,000 



3,700 

 12,200 



1,100 

 3,600 



100 

 10,200 



40 

 7 





 14 



58 

 15 



7 

 14 



80 



46 







44 



11 



21 





 



20 



11 













 3 





 



76 

 2 











55 



7 





 



( 3 ) 

 ( 3 ) 





 





 







1 



18 

 11 





 



3 60 

 31 





 3 



i The natural plots are identical throughout, but new plots were selected for each examination in the 

 stump patches. 



2 Although none were classed as dead, most of those classed as severely injured will not survive. 



3 The Aueust record of grazing injury includes all seedlings showing evidence of injurv at that time and 

 probably injuries of the preceding fall and spring. Since this examination was made at the close of a period 

 of vigorous growth, the injuries could not readily be classified as to severity or time of occurrence. 



The mortality from September, 1919, to June 1. 1920, was less than 

 during the much shorter period from June 1 to August 1, 1920. The 

 bulk of the loss during this latter period is known to have occurred 

 during the first two weeks of July, just prior to the beginning of the 

 summer rains, the most critical drought of the year and in fact the 

 only severe drought which the 1919 seedling crop had experienced. 

 The foregoing relationships were repeated in 1921. Comparatively 

 light losses occurred between August and November, 1920. So far 

 the records clearly point to drought as the dominating factor, whether 

 it is associated with clay content of the soil or with root competi- 

 tion. Conclusions as to the ultimate advantages or disadvantages 

 of cultivation can be reached only after longer records are available, 

 and will probably require a detailed analysis of each plot from the 

 standpoint of soil and herbaceous vegetation, as well as seedling 

 survival. 



Denudation by overgrazing. — Regardless of the final outcome with 

 respect to survival, the fact is established that the elimination of 

 ground cover by deep cultivation under the conditions here described 

 is unfavorable to germination. The reason is that on clayey soils 

 the surface tends to pack and dry out more where the natural vege- 

 tation is removed than where it is left undisturbed. These conclu- 



