16 



BULLETIN' 141, U. S. DEPARTMENT OF AGRIQULTURE. 



grazing, while only 2.6 per cent were killed and 5.7 per cent injured 

 by grazing. 



Table 7. — Summary of aspen sprouts killed and injured by cattle grazing on clear-cut 



plots. 



Grazing intensity and year of 

 examination. 



Total 

 number 

 sprouts. 



Uninjured 

 sprouts. 



Killed by 

 grazing. 



Injured by 

 grazing. 



Total num- 

 ber dead 



sprouts not 

 killed by 

 grazing. 



Injury not 

 due to 

 grazing. 



Lightly grazed: 



1915 



150 

 166 



379 

 311 



40 

 36 



Num- 

 ber. 

 109 

 140 



282 

 274 



16 

 21 



Per 

 cent. 

 72.7 

 84.4 



74.4 

 88.1 



40.0 

 58.3 



Num- 

 ber. 

 7 



Per 



cent. 



4.6 



Num- 

 ber. 



Per 

 cent. 



Num- 

 ber. 

 20 

 4 



46 

 13 



1 



2 



Per 



cent. 



13.3 



2.4 



12.2 



4.2 



2.5 

 5.6 



Num- 

 ber. 

 14 

 16 



24 

 10 



Per 

 cent. 

 9.4 



1916 



6 



15 

 14 



15 

 12 



3.6 



3.9 

 4.5 



37.5 

 33.3 



9.6 



Moderately grazed: 

 1915 



12 



3.2 



6.3 



1916 



3.2 



Heavily grazed: 

 1915 



8 

 1 



20.0 

 2.8 





1916 













Total 



1,082 



842 



77.8 



28 



2.6 



62 



5.7 



86 



8.0 



64 







5.9 











COMPARATIVE INJURY TO ASPEN SPROUTS BY SHEEP AND CATTLE. 



The damage to reproduction on sheep range, on the plots estab- 

 lished both in standing timber and on clear-cut lands, was consider- 

 ably different in character and extent from that on cattle range. 

 This difference in the degree of damage was evident in all localities 

 where the study was conducted, and especially where plots had been 

 grazed to practically the same degree of intensity. 



On plots in standing timber the comparative damage by sheep and 

 by cattle may be summarized as follows (data given in Tables 1, 2, 

 and 6) : 



(1) The average per cent of reproduction injured by sheep grazing 

 from 1912 to 1916, inclusive, was 27.3, and from 1915 to 1916, in- 

 clusive, 19.9. During the latter period the average per cent of injury 

 on cattle range, where the forage had been cropped to practically 

 the same extent, was but 3.97. 



(2.) The average per cent of reproduction killed on the plots scat- 

 tered over the sheep allotments from 1912 to 1916, inclusive, was 17.1, 

 and during 1915 and 1916, 24.8. During 1915 and 1916 less than 0.5 

 per cent of the reproduction on the plots grazed by cattle was killed 

 by browsing. 



On the clear-cut plot's the damage to reproduction by sheep as 

 compared with that by cattle is proportionately much more serious 

 than on plots in standing timber. The seriousness of normal sheep 

 grazing on clear-cut aspen lands may be summarized in the statement 

 that in the third year following the removal of the standing timber 

 it may be expected that no sprouts whatsoever will be found on the 

 lands. If any sprouts remain, they are usually so mutilated as either 

 to die after a season or two or so deformed as to produce timber of 



