EFFECT OF GRAZING UPON ASPEN REPRODUCTION. 7 
in the case of the number 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 OF 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 
1)0 
18.3 
Do. 
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 
Do - 
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 3J to 4J 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 lj-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- 
