18 BULLETIN 741. U. S. DEPARTMENT OF AGRICULTURE. 
HEIGHT AT WHICH REPRODUCTION IS EXEMPT FROM GRAZING 
INJURIES. 
The factor which chiefly determines the time of exemption of the 
reproduction from destructive browsing is the height of the sprouts. 
Observations have shown clearly that as soon as the terminal shoots 
and some of the lateral branches have attained a growth beyond 
which stock generally browse, the reproduction is no longer in danger 
of serious damage. Since sheep are particularly destructive to 
young aspen reproduction, detailed observations as to the height 
at which they browse were recorded both on the open range and on 
controlled plots. The height to which cattle browse was observed 
under range conditions only, 
HEIGHT TO WHICH SHEEP BROWSE. 
The height to which sheep browse depends, of course, upon the 
palat ability of the plants that grow within the reach of the animals, 
as well as upon the particular breed of sheep. Sheep relish woody 
plants, and they browse the aspen reproduction at as great a height 
as other highly palatable species. The sheep under observation 
consisted of about equal numbers of ewes and lambs of the Rani- 
bouillet and merino breeds, chiefly the former. The animals of 
both breeds were of about average size. 
In observing the height of grazing on the range it was necessary to 
adhere almost entirely to reproduction in standing timber, as rela- 
tively little aspen timber on the sheep allotments has as yet been 
clear-cut or heavily thi n ned. For this reason the height of the 
sprouts, the stand ol which was usually quite sparse and scattered, 
was uneven and often considerably below the maximum height at 
which sheep may browse. Accordingly, to determine the height of 
aspen browsed with unquestionable accuracy, and to secure a basis 
for future management of grazing in the aspen type, the obseiwations 
on the range were supplemented by a carefully planned experiment 
on a clear-cut fenced inclosure where the sprouts varied in height 
from 20 to 70 inches, the majority having a height of about 45 inches. 
The plot was one-fourth of an acre in area. Two 5-year old ewes 
and three lambs 3 months old were grazed on the plot as long as 
the feed, consisting of a luxuriant undergrowth of grasses, pea vines- 
a variety of weeds, and some shrubby growth, was sufficient to 
sustain the animals at their original weight. Accordingly, the plot 
was grazed much more closely than would be possible over the range 
generally where the lands are handled on the basis of a sustained 
annual yield. The plot in question was clear-cut late in the autumn 
of 1913 and the sheep were placed on it in August, 1916, so that the 
major portion of the reproduction was about 3 years of age. At 
the time the sheep were turned on there was a stand of 30,056 sprouts 
