EFFECT' OF GRAZING UPON ASPEN REPRODUCTION. 
RELATION BETWEEN INTENSITY OP GRAZING AND INJURY TO SPROUTS. 
The character of injury to sprouts will, of course, largely determine 
(1) the subsequent density of the aspen stand, (2) the ultimate form 
of the trees, (3) the subsequent rate of growth, and (4), to a con- 
siderable extent at least, the size of the trees and the commercial 
value of the timber. The removal of the leader or terminal shoots 
of aspen reproduction, for instance, may destroy the symmetry of 
the tree, especially if the leader is removed more than once. The 
injury caused by the destruction of lateral branches is chiefly physio- 
logical, the nutriment on which the specimen may build being 
roughly proportionate to the number of laterals; i. e., to the leaf 
area. 
The extent of browsing of leaders and laterals, or both, the mor- 
tality due to excessive browsing, and the number of sprouts unin- 
jured on the plots in standing timber during 1915 and 1916 are sum- 
marized in Table 3. The greatest number of specimens were under 
observation during these two years. 
Table 3. — Character and extent of injury to sprouts according to intensity of grazing, 
seasons 1915 and 1916. Plots in standing timber. 
Season and grazing intensity. 
Total 
sprouts 
lulled. 
Ungrazed 
sprouts. 
Leaders 
browsed. 
Leaders 
and 
laterals 
browsed. 
1915: 
Lightly grazed 
Moderately grazed 
Heavily grazed — 
1916: 
Lightly grazed 
Moderately grazed 
Heavily grazed — 
Percent. 
15.9 
17.5 
26.1 
13.5 
12.9 
63.2 
Percent. 
39.1 
14.0 
65.9 
54.2 
12.9 
Per cent. 
4.5 
4.3 
21.5 
7.8 
14.6 
4.4 
Per cent. 
2.3 
7.7 
15.1 
7.1 
12.8 
16.7 
Both in 1915 and 1916 the mortality was practically the same on 
lightly grazed and on moderately grazed plots, the average percentage 
being 14.9 (fig. 1 ) . On the heavily grazed plots, however, the mortality 
of sprouts was appreciably greater, being 26.1 per cent of the total in 
1915 and 63.2 per cent in 1916. The percentage of ungrazed sprouts 
in 1916 was more than five times as much on the lightly grazed areas 
and four times as much on the moderately grazed areas as on the 
heavily grazed plots. The general tendency is the same in the 1916 
figures. The averages for 1915 and 1916 on lightly grazed plots was 
52.5 per cent, on the moderately grazed areas 42.4 per cent, and on 
the heavily grazed plots only 13.4 per cent. 
The number of terminal shoots or " leaders" removed was prac- 
tically the same (averaging 4.4 per cent) on lightly and on moderately 
grazed plots in 1915; but on the heavily grazed areas it was consid- 
erably larger, amounting to 21.5 per cent. In 1916 the terminal 
shoots of 7.8 per cent of the specimens were consumed on lightly 
