£LANT SUCCESSION AND RANGE MANAGEMENT. 
11 
Table 1. — Precipitation in the heart of the tvheat-grass formation, 10,000 feet 
elevation, Manti National Forest, 191^-1917, inclusive. 
Year. 
June. 
July. 
Aug. 
Sept. 
1914 
Inches. 
0.35 
2.12 
.18 
4.78 
Inches. 
0.97 
1.84 
1.77 
3.73 
Inches. 
1.54 
.30 
1.81 
.50 
Inches. 
1.23 
1.67 
.39 
.30 
1915... 
191(3 
1917.... 
Average. . . 
1.86 
2.08 
1.04 
.90 
The average precipitation for the month as well as for the season 
varies widely. The greatest variation since 1914 in rainfall in June 
was 4.6 inches, the maximum being 
4.78 inches in 1917, and the mini- 
mum 0.18 inch in 1916. In July the 
variation was 2.76 inches, the maxi- 
mum being 3.73 inches in 1917 and 
the minimum 0.97 inch in 1914. 
Nearly 40 per cent of the 0.18 inch 
of precipitation recorded in June, 
1916, fell during the first half of the 
month, while nearly 68 per cent of 
the 0.97 of an inch recorded in July, 
1914, fell after July 20. Since only 
0.35 of an inch of rain was recorded 
in June, 1914, the soil was far below 
the average in water content. Ob- 
servations indicated that the un- 
questionable slowing down of growth 
noted after the first week in July, 
1914, was due to an inadequate 
water supply. 
Owing to the exceptionally low 
water requirements for the sur- 
vival of both the bunched and the 
turfed species of wheat grass, pro- 
longed periods of soil desiccation, 
covering critical periods of one or 
more seasons, seem to have little effect on well-established plants 
other than to decrease temporarily the aerial growth and the repro- 
duction. However, young stands of turfed species usually suffer ap- 
preciably less injury from soil desiccation than stands of bunch grass 
of similar age. This is accounted for by the fact that reproduction 
in the case of the turfed species is largely by extensive rootstocks 
which have little or no tendency to shoot out until the plant is per- 
/s n - J 
Fig. 4. — Small wheat grass (Agropy- 
ron dasystachyum). 
