EFFECT OF GRAZING UPON ASPEN REPRODUCTION. 7 



in the case of the immher of killed sprouts, the percentages being 12.3, 

 14.5, and 16.9 on the corresponding plots. On the lightly grazed areas 

 the average per cent of uninjured sprouts was 46.2, while on the 

 moderately and heavily grazed plots it was 27.1 and 9.1, respectively. 



RELATION BETWEEN INTENSITY OF GRAZING AND INJURY TO SPROUTS OP DIFFERENT 



HEIGHT CLASSES. 



The extent of injury to reproduction of different height classes 

 varies considerably. There appears to be no constant relation, how- 

 ever, between the different height classes of reproduction and the 

 percentage of injured or killed sprouts. In Table 4 the sprouts under 

 observation during the 5-year period have been grouped into height 

 classes and assembled according to intensity of grazing. 



Table 4. — Extent of injury to sprouts in standing timber, according to height classes 



and grazing intensities. 



Grazing intensity. 



Height 

 class of 

 reproduc- 

 tion. 



Total 

 number 



of 

 sprouts. 



Uninjured. 



Sprouts 

 killed by 

 grazing. 



Sprouts 



injured by 



grazing. 





Feet. 

 0.5 to 1.5 

 1.5 to 2.5 

 2.5 to 3.5 

 3.5 to 4.5 



891 

 235 

 193 

 173 



Num- 

 ber. 

 535 

 96 



68 

 84 



Per 

 cent. 

 60.1 

 40.9 

 35.2 

 48.6 



Num- 

 ber. 

 44 

 31 

 36 

 22 



Per 



cent. 



4.9 



13.2 



18.7 

 12.7 



Num- 

 ber. 

 272 

 43 

 10 

 5 



Per 



cent. 



30.3 



Do. 



18.3 

 5.2 



Do. 



2.9 















46.2 





12.3 





14.1 















.5 to 1.5 

 1.5 to 2.5 

 2.5 to 3.5 

 3.5 to 4.5 



1,451 

 709 

 416 

 280 



653 



217 



59 



53 



45.0 

 30.6 

 14.2 

 18.9 



200 



123 



73 



26 



13.7 

 17.4 

 17.5 

 9.3 



290 



206 



142 



46 



20.0 





29.1 



Do. 



34.1 



Do 



16.5 















27.1 





14.5 





24.9 















.5 to 1.5 

 1.5 to 2.5 

 2.5 to 3.5 

 3.5 to 4.5 



1,395 

 628 

 241 

 109 



246. 



26 



23 



6 



17.6 

 4.1 

 9.5 

 5.5 



318 



131 



21 



17 



22.8 



20.8 



8.7 



15.6 



665 

 373 

 159 



43 



47.7 



Do 



59.4 



Do. 



66.0 



Do. 



39.5 















9.1 





16.9 





53.1 













The number of specimens remaining on the plots decreases with 

 the increase in height class. Thus in the 3| to 4^- foot class is found 

 the sparsest stand of reproduction examined, all intensities of grazing 

 considered. This is accounted for by the number of sprouts killed 

 by adverse climatic conditions and by rodents, as well as by the 

 number killed by browsing. 



The shoots of the first year's sprouts (6-inch to 1^-foot class) are 

 more succulent than those of sprouts of greater age, but the new 

 twigs and branches produced each season by the older specimens 

 are quite as palatable as are the shoots of younger sprouts. Hence, 

 while the terminal shoot is less liable to injury in the case of the 

 taller and older sprouts than sprouts 1£ feet or less in height, the 

 taller specimens are nevertheless subject to injury of varying serious- 



