EFFECT OF GRAZING UPON ASPEN REPRODUCTION. 21 
The height of browsing increases gradually with the increase in 
the height classes of the reproduction up to the fifth class; i. e., from 
21 to 41.1 inches. From this point on up to the ninth class the height 
of the browsing varies slightly above or below the 40-inch mark. 
In the ninth class occurs the maximum average height of 41.8 inches. 
The average height at which the 69 grazed sprouts in the transect 
were grazed was 38.1. This is about the height of the top of the 
heads of mature Rambouillet and merino sheep. 
Sprouts the terminal shoots of which have attained a height of 
40 inches or so are apt to suffer only slight permanent injury, and 
extensive observations on the range and on the various check plots 
have shown that reproduction having an average height of 45 inches 
is practically exempt from serious injury. Hence lands supporting 
reproduction averaging 45 inches in height may be grazed with 
practically no injury to the terminal shoots. Moderate browsing of 
some of the lateral branches will occur, of course, as long as they are 
easily within the reach of sheep, but the effect of such browsing is 
insignificant so far as concerns the development and health of the 
specimen. 
HEIGHT TO WHICH CATTLE BROWSE. 
It has been pointed out that reproduction only a few inches or so 
in height is subject to about the same degree of browsing by cattle 
as is reproduction of greater heights. Thus, contrary to what might 
be expected, sprouts two or three feet high which by virtue of their 
greater conspicuousness might be presumed to afford more con- 
venient browsing than the shorter specimens are nevertheless dam- 
aged as little as any of their younger associates. 
Considerable variation is observed in the height of the browsing 
by cattle. Isolated instances have been recorded of the removal of 
leafage to a height of about 70 inches, but browsing at such a height 
is exceptional and o,f little economic significance. Damage of greater 
severity occurs between heights of 55 and 60 inches, the latter figure, 
however, being about the minimum at which twigs and stems are 
eaten. Thus in localities where cattle are apt to drift and linger 
and where it is desired to reforest the lands fully the reproduction 
should be permitted to attain a growth of not less than 5 feet prior 
to heavy stocking. Obviously, then, lands which are to be reforested 
should not be used as salting grounds until a sufficient portion of the 
reproduction has attained a height beyond which destructive brows- 
ing is likely to occur. 
RATE OF GROWTH OF ASPEN REPRODUCTION. 
In the management of grazing on cut-over lands it is necessary to 
know, in order to make the most judicious use of the knowledge of 
the height which aspen reproduction must attain to be exempt from 
