26 BULLETIN 741, U. S. DEPARTMENT OF AGRICULTURE. 
large proportion of the nonbrowsed sprouts are killed by causes other 
than grazing. In standing timber on cattle range also the injury 
varied according to grazing intensity, but was less than on the sheep 
range. During 1915 and 1916 the average percentage of injured and 
killed sprouts by cattle browsing was 1.6, 2.4, and 26.8 on lightly, 
moderately, and heavily grazed plots, respectively. 
(5) On clear-cut lands, where the reproduction is conspicuous and 
the stand even, the annual mortality due to sheep grazing is exceed- 
ingly heavy. As a rule three years of successive sheep grazing on 
such lands results in the destruction of the entire stand. Some injury 
is also caused by cattle on clear-cut areas, but unless the range is 
stocked with cattle beyond its normal carrying capacity there is little 
danger of the reproduction being destroyed beyond the requirements 
necessary for the establishment of a full commercial stand. 
(6) Only slight difference is recorded in extent and character of 
browsing either by sheep or by cattle on different height classes of 
reproduction, so long as the total height growth of the sprouts has 
not passed the limit at which stock find the food accessible. 
(7) A comparison of the character and intensity of browsing shows 
that a notably greater proportion of the woody stems is consumed 
by sheep than by cattle. Even in the autumn after the leaves have 
dropped sheep devour a considerable quantity of the stems of a single 
season's growth regardless of the presence of an abundance of choice 
forage. In the case of cattle, however, the naked stems are practi- 
cally untouched. 
(8) Aspen sprouts are not necessarily permanently injured, nor 
will the mature tree be lacking in form or symmetry as a result of the 
removal once or twice of the terminal shoot. Nearly any one of the 
lateral branches which grow near the terminal shoot appears to be a 
potential terminal and may readily assume the function of the ter- 
minal itself. The destroyed leader is very commonly and promptly 
replaced by shoots originating from adventitious buds near the ter- 
minal. On the other hand, the removal of both the lateral branches 
and the terminal shoot to such an extent as to interfere appreciably 
with photosynthesis and the nutrition of the specimen readily weak- 
ens and decreases its subsequent rate of growth materially. If the 
normal leaf surface is not readily replaced and then maintained, death 
is the inevitable result. 
(9) On lands protected from grazing aspen sprouts are produced 
only during the first two seasons after cutting. On grazed lands a 
considerable number of sprouts are sent up for three successive sea- 
sons following the removal of the timber. The third year's repro- 
duction, however, appears from two to fixe weeks later than that 
produced in the two previous seasons and is, for the most part, 
