8 



BULLETIN 741, U. S. DEPARTMENT OF AGRICULTURE. 



ness so long as the branches are within reach of the sheep. Further- 

 more, the sprouts listed in Table 5 which have the least height growth, 

 viz, those "less than one season old" and those "below 6 inches, one 

 season old," are undoubtedly protected from grazing by the rather 

 luxuriant cover of herbaceous vegetation which characteristically 

 occurs in the aspen type after about August 1 and hides much of the 

 reproduction from view. The sprouts in these classes show a con- 

 siderably smaller percentage of grazing than those of greater height. 

 However, the loss chargeable to grazing is considerable, and owing 

 to the succulence of the entire aerial parts during the first season 

 of growth there were numerous individual sample plots representing 

 large areas where on account both of the climatic conditions and of 

 browsing the greatest injury to sprouts was inflicted during the initial 

 season of growth. 



In view of the mortality of 1 -year-old sprouts due to browsing 

 and causes other than browsing, it may be concluded that even light 

 cropping of the lands is sure to have a determining effect on the ulti- 

 mate timber stand. The extent to which the land should be grazed 

 when the sprouts are just beginning to appear, therefore, should be 

 determined by the timber stand ultimately desired. 



Table 5. — Injuries to sprouts 1% feet or less in height according to varying intensities 

 of grating; data grouped by seasons and height classes and according to intensity of 

 grazing. Plots in standing timber. 





Lightly grazed. 



Moderately grazed. 



Heavily grazed. 



Total 

 num- 

 ber 

 grazed 



all 

 inten- 

 sities. 



Per 

 cent 

 grazed 



all 

 inten- 

 sities. 



Season and height 

 class. 



Total 

 num- 

 ber. 



Num- 

 ber 

 grazed. 



Per 



cent 

 grazed. 



Total 

 num- 

 ber. 



Num- 

 ber 

 grazed. 



Per 



cent 



grazed. 



Total 

 num- 

 ber. 



Num- 

 ber 

 grazed. 



Per 



cent 



grazed. 



1912 



98 

 899 

 783 

 386 

 216 







122 



871 



1,826 



1,405 



924 



5 



262 

 737 

 261 

 248 



4.09 



30.08 

 40.36 

 18.56 

 26. 80 



154 



458 



2,150 



2,192 



848 



16 



224 



1,462 



1,363 



88 



10.38 

 48.90 

 68.00 

 62.18 

 10.30 



21 

 773 



2,498 



1,678 



366 



5.61 



1913 



287 

 299 

 54 

 30 



31.92 

 38.18 

 13.98 

 13.90 



34.69 



1914 



52.48 



1915 



42.00 



1910 



18.40 







Total 



2,382 



670 



28.19 



19.4 

 20.9 



23.4 

 39.9 



5,148 



1,513 



29.38 



21.3 

 18.3 



33.0 



36.2 



5,802 



3,153 



54.34 



52.8 

 51.5 



37.8 

 73.7 



5,336 



1,455 

 1,088 



797 

 1,867 





Average 



40.02 



Height class: 



Sprouts less than 1 



season old 



1-year-old sprouts 



1 tol.Steet 



Sprouts below 6 in- 



inches (1 season 



old) 



551 

 315 



625 

 891 



107 

 66 



146 

 355 



1,711 

 1,103 



991 

 1,343 



305 

 202 



328 



486 



1,861 

 1,592 



854 

 1,395 



983 

 820 



323 

 1,026 



35.2 

 26.0 



32.1 



6 inches to 1.5 feet 

 (1 season old) 



51.4 



SUMMAEY. 



The effect of sheep browsing in standing aspen timber may be 

 summarized as follows : 



(1) Of the total number of sprouts examined during 1912 and 1913, 

 inclusive, the percentage of seriously injured and killed sprouts was 



