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GRAZING RANGES IN SOUTHERN ARIZONA. Sl 
To understand these possibilities it is only necessary to call atten- 
| tion to two or three factors which would affect the result. If for 
any reason a pasture were understocked there would be excess feed 
on it, but the figures for average monthly and yearly numbers car- 
ried, as well as the average carrying capacity, would be lowered. 
Such a condition might arise if the stock-water supply should 
diminish or fail, a condition that did obtain for some time on the 
Ruelas place during 1913 and part of 1914. 
If, because of exceptionally high prices, a man should sell a large 
part of his stock and not restock at once, or if, for any reason, he 
should be forced to sell or was unable to buy whenever his pasture 
warranted it, the number of animals on the pasture would be less 
AVERAGE NUMBER OF ANIMALS CARRIED: By Month =\—-— By Year —=x=—— /NDICATED CARRYING CAPACITY: Number of onimals per Section 
Tic. 5.—Curves showing variations in the rate of stocking on those parts of the reserve 
that have carried stock for the past six years. The curves numbered 1 show the 
average number of mature animals (cattle, horses, or burros) carried on each pasture, 
by months, for the full period. Curves numbered 2 show the same data by years, 
Curves numbered 3 show the average carrying capacity in acres per head per year for 
9 
each pasture during the period of observation. Curves numbered 3 rest upon the 
assumption that the pastures have been stocked to their legitimate limit each year. 
_ than it could carry, and all the figures relating to numbers carried 
_ and carrying capacity would again be below what the feed in the 
pasture might warrant. 
| Again, if the user should overestimate the capacity of his range 
and put on more stock than it could properly carry, the result would 
be an increase in all the figures, at least for a time, and a noticeable 
drop ata later period. Seasonal climatic variations of marked degree 
also would tend to decrease all values if unfavorable and to increase 
them if favorable to the growth of forage, though such variations 
would tend to counteract each other during a series of years. 
