May 31,1924 Cell Sap Density and Environmental Conditions 
853 
The usual relation between altitude and temperature holds in a general way 
in the Wasatch Mountains. Comparisons of temperatures for Salt Lake City 
and Cottonwood Nursery are shown in Table II. It is impossible from the mean 
monthly temperatures to form a clear idea of the relative duration of tempera¬ 
tures suitable or unsuitable for plant growth; that is, the temperatures above or 
below 40° F. Accordingly the average number of hours having temperatures 
above and below 40° F. and the number of hours of freezing temperature for 
June to September inclusive at three different elevations on the Ephraim Can¬ 
yon watershed on the Manti National Forest about 100 miles south of the Big 
Cottonwood watershed for the period from 1913 to 1922, inclusive, were deter¬ 
mined (Table III). 
Table III .—Summation of temperatures with reference to elevation on the Ephraim 
Canyon watershed 
Elevation (feet) 
Type 
Average number of hours 
June-September 
Above 
40° F. 
Below 
40° F. 
Of freez¬ 
ing tem¬ 
perature 
7,100... 
Oak brush____ 
2,786 
142 
39 
8'700.. 
Aspen-fir.__._. 
2; 672 
2,499 
256 
78 
10,000. 
Spruce-fir_ 
426 
126 
Temperature gradients with altitude have been worked out by several inves¬ 
tigators for different mountainous regions in the West. Pearson (99) finds a 
mean altitudinal temperature gradient of 3.68° F. for each 1,000 feet from an 
elevation of 3,300 feet at Kingman in northern Arizona to timber line on the 
San Francisco Mountains at 11,500 feet. Shreve (115) reports a gradient of 
4.11° F. in the Santa Catalina Mountains of southern Arizona. Observations 
on other mountains in the West, according to Hann (43, p. 243-245), have 
resulted in the following gradients: Sierra Nevadas in Placer County, California, 
4.12° F.; Pikes Peak, Colorado, 3.46° F. Air temperatures decrease quite uni¬ 
formly with an increase'in altitude, except for local inversions which are occa¬ 
sionally encountered due to air drainage in canyons and mountain valleys. 
Precipitation in the Wasatch Mountains increases rapidly with altitude up to 
and including the aspen-fir type, as shown in Table IV. From this type to the 
spruce-fir type the increase is less pronounced, but the snowfall in the spruce-fir 
type on the high mountains is considerably heavier. Although not strictly com¬ 
parable because the records for these stations do not cover the same period, they 
are nevertheless significant. They indicate an increase in the annual precipita¬ 
tion of 6.4 inches for each thousand feet. Alter’s (1) study of the relation 
between precipitation and altitude, for practically all groups of adjacent stations 
with simultaneous records, on the western slope of the Wasatch Mountains, shows 
an increase in precipitation of from 15 inches annually at the lower elevation 
-(4,250 feet) to 33 inches at the higher elevation (8,700 feet), or uniformly 4 inches 
per year per 1,000 feet. On the eastern slope on the leeward side of the range 
the precipitation decreases more rapidly with decrease in altitude, being nearly 
5.5 inches for each thousand feet for the composite of all stations studied by 
Alter. 
96039— 241-2 
