8 BULLETIN 34, U. S. DEPARTMENT OF AGRICULTURE. 
ally in localities where the stand has previously been weakened 
through drought, is an important factor in connection with reproduc- 
tion. The injury to seedlings due to grazing depends primarily upon 
the class of stock grazed, the season of grazing, and the way in which 
the stock is handled. It can therefore best be discussed in connection 
with the different systems of grazing the range, the relation of each 
system to the maintenance of the stand, and the revegetation of the 
range with the most valuable plants. 
EFFECT OF GRAZING ON THE FORAGE CROP. 
From what has been said about the growth requirements of the 
principal forage plants, it is plain that the most effective system of 
range management from the standpoint of the vegetation alone will 
be the one that interferes least with the growth of the plant up to the 
time of seed maturity, and then aids in planting the seed. Any 
system adopted must be practicable from the standpoint of the stock- 
man. 
Grazing on western range lands may be divided into three more 
or less distinct systems: (1) Yearlong or season-long grazing year 
after year; (2) yearlong or season-long grazing with occasional total 
exclusion of stock during the entire year to give the forage a chance 
to reproduce; and (3) deferred grazing, which aims at a rotation in 
the time of using each portion of the range, allowing the plants on 
one portion to mature their seed each year before they are cropped, 
and then grazing it to avoid loss of forage through nonuse, and to 
assist reproduction by trampling in the seed. 
The following discussion aims to show the comparative merits of 
the three grazing systems from the standpoint of the range plants' 
requirements for growth and reproduction, and to outline the system 
which promises the best results to both the range and the stock 
industry. 
YEARLONG GRAZING. 
Prior to the inclusion of lands in the National Forests stock 
usually had access to, the range before snow was entirely off it, and 
therefore when the earliest growth was appearing in the lower eleva- 
tions. As the season advanced the stock drifted or were driven to 
the highest portions, reaching each portion soon after growth had 
begun. In many localities the range was so crowded that it was 
grazed continuously throughout the season; the only period of rest 
was during the time required for the herbage to grow enough after 
being closely cropped to again permit grazing. Kesults from such 
practices were directly comparable to those from the monthly clip- 
ping experiments cited, and, in addition, the range was damaged a 
