906 
Journal of Agricultural Research 
Vol. XXVII, No. n 
The type species of the association is interesting in that it may occur 
sporadically m any other association. Our predecessors (24) have 
shown that m the typical Kochia association the upper foot of soil 
is usually free from injurious quantities of salts but that saline sub¬ 
stances are extremely concentrated in the second, and especially in the 
th ^ d 1 ^ 00 ^? nd at 1 , ower Ievels - Further details are given elsewhere (24). 
Table VI may be consulted for the constants of the species of the 
Kochia association. 
SHADSCAEE ASSOCIATION 
The permanent vegetation of the shadscale association is, practically 
speaking, limited to the single ligneous species A triplex confertitolia, 
which, as a component of vegetation, is one of the most important 
species of the Great Basin. It is abundant on mountains above the 
Bonneville level, and extends below the association of which it is the 
type, to form a prominent element of the greasewood-shadscale associ¬ 
ation on the lower slopes of the valley and on the ridges which are inter¬ 
spersed among the salt flats along the southern shore of the Great Salt 
Lake. 
Where the gradient is so slight that the land appears practically level, 
the shadscale is the only conspicuous ligneous species. The association 
is, however, diversified in places by small washes in which the number 
of woody species is larger. There are also a few ephemeral and per¬ 
ennial herbs. 
In the summary of the investigations on the physical environment of 
this association, we note (24) that it is usually characterized by “(1) a 
soil of finer texture, having a higher moisture equivalent than in sage¬ 
brush land; (2) a deficit in midsummer of moisture available for plant 
growth, (3) a high salt content of the soil below the depth of 1 or 2 feet; 
and (4) as compared with land occupied by the Kochia association, a 
somewhat lighter and more gravelly texture in the first foot and a much 
more uneven surface—conditions which probably result in better pene¬ 
tration and, hence, in a larger seasonal total of water available for plant 
growth than on Kochia land.” 
It has seemed desirable to divide our determinations into two series 
which can not, however, be sharply separated—the typical shadscale 
association and the washes through the shadscale association. 
the typical shadscale association 
The constants for the species of this association appear in Table VII. 
Table VII.— Physicochemical constants for species of the typical shadscale association 
Growth form and species. 
Date. 
Freezing 
point 
depres¬ 
sion, 
A. 
Atmos¬ 
pheres 
osmotic 
concen¬ 
tration, 
P. 
Specific 
electrical 
conduc¬ 
tivity, 
K. 
Ratio, 
conduc¬ 
tivity to 
depres¬ 
sion, 
k/a. 
Chlo- 
rids 
per 
liter, 
Cl. 
HALF SHRUBS 
Atriplex confertifolia (Torr.) Wats.. 
Average. 
1920. 
June 2 
... do. 
July 23 
... do. 
2.74 
2.36 
4.82 
4.65 
3-64 
32-9 
28.3 
57-6 
55-7 
43-6 
0.0586 
•0535 
.0727 
.0700 
.0637 
O.O214 
.0227 
.0150 
.01:50 
.0185 
10.2 
25.O 
17.6 
