EFFECT OF GRAZING ON WESTERN YELLOW PINE. 11 
AMOUNT OF FORAGE BY SEASONS. 
The fact that a greater amount of damage occurs during the dry 
period of early summer, when ordinary forage is scarce, than during 
other periods of the grazing season suggests the probability that dur- 
ing a season when feed is unusually abundant the amount of damage 
will be relatively small. This supposition is confirmed by a com- 
parison of the damage done in 1914 with that done in 1913. 
Ordinarily not enough precipitation occurs during May and June 
to support the vegetative growth, and as a result not enough forage is 
produced to meet the needs of stock. This was the case in 1918; but 
in 1914 the dry period was broken in June by sufficient rainfall to 
revive the forage, and. this was followed by abundant rainfall in July 
and August. Since the three months from June to August form the 
main growing period, 1914 was an unusually favorable year for 
the production of forage, and 1913 an unusually poor one. (See 
Table IV.) 
TABLE 1V.—Precipitation during the growing periods of 1913 and 1914.* 
Average for yellow-pine type. May. June. July. Aug. Sept. 
1 The monthly rainfall is an average for the entire yellow-pine type, based upon the records at Fort 
Valley, Flagstaff, and Walnut Canyon. < 
TABLE V.—Comparison of the serious damage caused by grazing during 1913 
and 1914. 
Trees seriously 
damaged. 
Year. 
Per cent 
Number. | of total. 
AO cmmpemmemermae sree ey oak eee ok T5552 Yast Fee MPL eave Bee ob 1,417 15.8 
TOA ee eee onl 2 ctarctay a aysiciscialatatassibis simicinisiaininj aie Sin/ape soe me tea store Mus Maas cise oes 1, 162 13.0 
Table IV indicates that vegetation could not have made any con- 
siderable growth in 1913 before July, and the record of periodic 
damages shows that more than one-half of the total annual damage 
for that year occurred during this dry period. No record of periodic 
damage was kept in 1914, but a summary for the year (see Table V) 
reveals 13 per cent of the entire number of trees seriously damaged, 
as compared ,with 15.8 per cent for 1913. The lower per cent of 
damage for 1914 is believed to be due chiefly to the greater abundance 
of feed during that year, particularly during June and early in July. 
