EFFECT. OF GRAZING UPON ASPEN REPRODUCTION. 



15 



80 



10 



GO 



50 



EFFECT OF CATTLE BROWSING. 



Injury to reproduction on clear-cut aspen plots chargeable to 

 browsing, trampling, and rubbing by cattle was observed during the 

 seasons of 1915 and 1916 in the same detail as in the case of the 

 plots located on the sheep allotments. Early in the spring of 1915 

 two representative areas located at an elevation of approximately 

 8,800 feet were cleared of timber, and sample plots and quadrats were 

 established, by means of which the rate of sprouting and the exact 

 character of damage caused exclusively by cattle were noted. The 

 clear-cut areas were 

 comparable in every 

 way, except that one 

 was subject to normal 

 grazing while the 

 other was fenced 

 against stock. 



In recording the 

 damage to the repro- 

 duction, account was 

 taken of the injury 

 and mortality due 

 both to the presence 

 of cattle and to 

 causes other than 

 grazing. The data 

 were grouped accord- 

 ing to grazing inten- 

 sity. The results are 

 summarized in Table 

 7, and for purposes of 

 ready comparison the 



>5 



§ 40 



30 



20 



10 





















/ 



/ 

 / 





/ 

 / 

 / 

 / 





/ / 



-T=— 





Lightly Grazed Moderately Grazed Heavily Grazed 



urecl By Grazing 

 n eat By Grazing 



_ _ _ Sprouts Uninj 



Sprouts Inj 



Sprouts Killed By Grazina 



Fig. 5. — Relation of cattle grazing to number of uninjured and 

 killed sprouts, season 1915. 



data recorded in 1915, which are practically the same as for 1916, 

 are shown graphically in figure 5. 



In 1915 the number of uninjured sprouts was highest on the lightly 

 and moderately grazed plots (72.7 and 74.4 per cent, respectively) 

 and notably lower on the heavily grazed areas (40 per cent). In 1916 

 the relation was similar. There was practically no difference in the 

 per cent of injured and killed sprouts on the lightly grazed and on 

 the moderately grazed plots, while on those heavily grazed there 

 was an appreciable increase in the percentage of both injured and 

 killed sprouts. 



A considerable proportion of the sprouts on these plots, as in the 

 case of sprouts on plots previously reported on sheep range, were 

 injured or killed by causes other than grazing. Eight per cent of 

 the sprouts died and 5.9 per cent were injured by causes other than 



