oy ee 
EFFECT OF GRAZING ON WESTERN YELLOW PINE. 19 
average growth of 0.7 foot for the three-year period, 1912-1914. 
Measurements of a similar number of trees growing in the check 
plots just outside these fenced areas showed an average height growth 
of 0.2 foot for the three-year period. 
The rate of growth of 46 badly grazed saplings at Fort Valley, 9 
miles northwest of Flagstaff, and 59 uninjured: saplings of the same 
age in a pasture on Observatory Hilk, just outside of Flagstaff, the 
two sites being very similar, are given in Table VIII. 
Taste VIII.— Comparative growth of trees in pasture and on overgrazed range. 
Average 
ne Number | Average | Average 8 
Location. . annual 
of trees. age. height. growth. 
. Years. Feet. Feet. 
LUD DE SDI IRAE SE Ro ae trad STALE eee os See ee eee 59 17. 2 5.2 0. 36 
ONORET AZ COR ATIE Cetera ea 874 SG Beas yee a aaah ata ae | 46 17.0 2.1 12 
The foregoing comparisons, which are believed to be representa- 
tive, indicate that grazing injuries decrease the rate of growth of 
young trees from one-half to two-thirds. 
From the standpoint of the production of a crop of timber this 
check in the growth of reproduction is not a serious matter, provided 
the trees have a chance to outgrow the injuries before their vitality 
is destroyed. The addition of 20 or 30 years to the period of rota- 
tion is not in itself a vital consideration in the management of yel- 
low pine. Retarded growth is a serious matter, however, when it 
is considered that grazing conditions are generally stable and that 
where severe damage occurs the trees have no opportunity to out- 
grow their injuries, but are slowly killed. 
FORM OF TREE. 
It is generally thought that the bole of a young tree that is severely 
injured is likely to become crooked or forked. This belief appears 
to have little basis in fact. The probable cause of crooked boles in 
nearly all instances is that the trees have at some time been over- 
topped or suppressed and in that condition have grown at an angle 
toward the strongest light, later becoming dominant or codominant 
and attempting to grow upright. Forked boles serious enough to be 
objectionable are formed at a height above that affected by grazing. 
Observations of a great many young trees recovering from severe 
injuries revealed no deformities that promised to be at all prominent 
when the trees mature. Nearly all grazing injuries occur at a height 
of less than 44 feet, and the trees, when protected, very quickly de- 
velop a leader which gradually outstrips all others. The laterals of 
