EFFECT OF GRAZING ON WESTERN YELLOW PINE. Pal 
TABLE IX.—Comparative growth of protected and unprotected saplings. 
Average growth 
during 3 years. 
Height classes. 
I Outside 
u of 
pastures. pastures. 
Feet. Feet. Feet. 
1 Seana ees We 0.8 0.2 
Ds Cee PS ey epee iil «3 
BRE Seon ee eee 12 a4 
Facharags ebay ss 1.4 «4 
| Average.-..:- lanl 32 
The results show that the growth of the protected saplings is more 
than three times as rapid as that of the unprotected ones and indi- 
cate a marked ability of young pines when protected to recover from 
injuries. This conclusion is substantiated by the results of measure- 
ments of trees previously injured within the fenced plots and of 
’ trees outside subject to continued injury (p. 18). As stated in that 
case, the ratio of growth between protected and unprotected trees 
was as 7 to 2. 
Even though protection against severe grazing may enable seri- 
ously injured saplings to recover, such protection may not be advis- 
able unless the loss of young trees on unprotected areas is excessive. 
_ Reference to Table I shows that an average of only 0.9 per cent of 
the total number of trees were found dead during the three years 
covered by the study. While this loss probably represents the aver- 
age mortality from grazing over the Forest as a whole, yet it does 
not adequately express the seriousness of the losses in certain impor- 
tant parts of the Forest. Areas exist where more than 50 per cent 
of the total number of young pines have been killed. Such areas 
include many sections of the bunchgrass type south and west of 
Lake Mary, the edges of parks, bedgrounds, driveways, the vicinity 
_ of headquarter ranches and water holes, and range areas that have 
been overgrazed for a long period. 
It is estimated from a comparison of the age and height of 265 
trees that a yellow pine will ordinarily, if uninjured, reach a height 
of 4.5 feet—above which it can withstand severe grazing injuries— 
when 15 years old, but that if it is subject to repeated grazing injuries 
it may require 35 years to reach this height. If it may be assumed 
that under average conditions which prevail over the Forest it re- 
quires 17 years for reproduction ‘to reach a height of 4.5 feet, and 
that, as shown in Table I, 0.9 per cent of all trees observed die an- 
nually as a result of grazing injuries, it-is safe to conclude that the 
loss of trees during the period when they are subject to severe grazing 
is approximately 15 per cent of the stand, or nearly as many as are 
