852 
Journal of Agricultural Research 
Vol. XXVIII, No. 9 
the absence of Engelmann spruce from the higher elevations on the Taylor 
Canyon watershed. Engelmann spruce is not found on the west slopes of the 
Wasatch Range immediately overlooking the large valley which was originally 
the Great Salt Lake Desert. Its absence is probably caused by the exposure of 
this side of the range to the full sweep of the prevailing southwesterly winds 
which blow across the desert and cause excessive evaporation both summer and 
winter. During the winter they also pile the snow in deep drifts on the leeward 
side, exposing the bare ground on the slopes to the windward and thus favoring 
winterkilling there. 
In the Wasatch Mountains the study covered a range of 5,500 feet, from the 
bottom of the valley at an elevation of 4,500 feet where the sagebrush (Artemisia 
tridentata) is characteristic, through the juniper, chaparral, and aspen-fir types 
to the spruce-fir (Picea engelmanni-Abies lasiocarpa) type at 10,000 feet above 
sea level. The Wasatch Plateau series of observations covered a similar range 
in altitude from the greasewood-shadscale (Sarcobatus vermiculatus-Atriplex sp.) 
type at 5,500 feet, through the sagebrush, pinon-juniper, oakbrush, (Quercus 
utahensis) and aspen-fir to the spruce-fir type at 10,000 feet elevation. Each 
of the major plant associations is practically identical with definite vegetative 
types or life zones, such as those proposed by Merriam (93). Utah juniper is 
found from 4,500 to 7,000 feet in the Wasatch Mountains and the Rocky Moun¬ 
tain juniper (Juniperus scopulorum) from 6,000 to 8,500 feet (7,500-9,000 feet 
on the Wasatch Plateau). Douglas fir (Pseudotsuga taxifolia) occurs from 5,500 
feet on northern aspects to 10,000 feet on southern aspects (7,500-9,000 feet on 
the Wasatch Plateau), while white fir (Abies concolor) is found from 5,500 feet 
on northern aspects to about 8,500 feet on southern aspects (7,500-9,000 feet 
on the Wasatch Plateau). Engelmann spruce occurs from 7,000 feet along 
streams to 10,000 feet, while alpine fir is found from 7,500 feet on northern 
aspects to 10,500 feet. On the Wasatch Plateau these two species range from 
about 8,500-11,000 feet. Blue spruce (Picea parryana) has a limited natural 
range extending from 7,000 to 8,000 feet along stream courses in the canyon 
bottoms (6,500-8,500 feet on the Wasatch Plateau). Limber pine (Pinus 
flexilis) occurs from 7,500 feet on northern aspects to timber line (10,500-11,000 
feet). Aspen extends from about 6,800 feet in canyon bottoms up through the 
Douglas fir and spruce-fir types to an elevation of 10,000 feet. Narrowleaf 
cottonwood (Populus angustifolia) and other broadleaved species are found along 
stream courses from the lower valleys to about 7,500 feet. 
Table II .—Comparison of mean maximum , mean minimum , and mean tempera¬ 
tures by months in degrees F. for Salt Lake City , and Cottonwood Nursery , Utah a 
Stations and temperatures 
January 
February 
March 
April 
May 
June 
July 
1 
1 
September 
October 
November 
December 
Average, May- 
October 
Annual 
Salt Lake City {4,408 feet'above sea 
level; 45 years record): 
Mean maximum. 
36.6 
41.0 
50.9 59.9 
68.2 
79.1 
87.9 
86.6 
76.2 
62.9 
49.7 
39.2 
76.8 
61.5 
Mean minimum.. 
21.7 
25.8 
32.739.9 
46.6 
55.1 
63.2 
62.5 
52.6 
42.1 
32.1 
25.0 
53.7 
41.6 
Mean.. 
29.2 
33.4 
41.8 
49.9 
57.4 
67.1 
75.6 
74.6 
64.4 
52.5 
40.9 
32.1 
65.2 
51.6 
1916 
1916 
1916 
1915 
1915 
1915-17 
Cottonwood Nursery (7,450 feet above 
and 
to 
to 
to 
to 
and 
sea level): 
1918 
1919 
1920 
1920 
1920 
1919-20 
Mean maximum_ 
56.0 
72.6 
80.6 
78.3 
67.5 
53.1 
68.0 
Mean minimum_ 
29.0 
37.7 
44.3 
41.6 
36.0 
25.9 
35.8 
Mean. 
42.5 
55.2 
62.4 
60.0 
51.8 
39.5 
51.9 
—- 
Data furnished by J. Cecil Alter either in manuscript or published form (/, £). 
