388 
Journal of Agricultural Research 
Vol. I, No. 5 
Table VII.— Sand-hill mixed association: Moisture conditions and salt content of 
the soil in a typical area . 1 
Moisture 
content 
Depth 
Moisture 
Wilting 
above or 
Salt 
(feet). 
equivalent. 
coefficient. 
below the 
content. 
wilting 
coefficient. 
I 
9.2 
5*0 
— 0. 1 
0.03 
2 
9*7 
5 - 3 
+0. 7 
•03 
3 
6. 2 
3*4 
+ 1.1 
•03 
4 
5-8 
3 * 1 
+ 1*3 
.04 
c 
. 01 
6 
. 01 
1 All data are in percentages of the dry weight of the soil. 
If the data given in Table VII may be taken as representative, land 
occupied by this association is characterized by the following soil con¬ 
ditions: (i) A low moisture-holding capacity, as indicated by the low 
moisture equivalents, (2) available moisture present, at least during the 
fore part of the summer, at a depth attainable by the more deeply pene¬ 
trating roots, and (3) a very low salt content. 
Adaptations to the Physical Conditions 
The soil-moisture conditions of the sand hills are obviously such as to 
favor plants with deeply penetrating roots, and, accordingly, large woody 
plants are predominant in this association. Sagebrush, the most abun¬ 
dant woody species, is noteworthy for the great depth reached by its tap¬ 
root when the conditions are favorable. Of the herbaceous species of this 
association, some have a well-developed taproot, while others produce an 
abundance of superficial roots. The shallow-rooted herbs, being de¬ 
pendent upon the moisture of the surface soil, mostly complete their 
growth and ripen seed early in the summer. Certain of the perennial 
herbs, notably Psoralea lanceolata , spread by slender, creeping rootstocks 
and can therefore withstand frequent burial. This plant is excellently 
adapted to colonizing the blow-outs and may be regarded as the pioneer 
plant of the moving sands. 
KOCHIA ASSOCIATION 1 
Topographical Relations 
The Kochia association (PI. XLVI) occupies a narrow and nearly con¬ 
tinuous belt which extends across the valley along the lower boundary of 
the sagebrush area and lies between the latter and the shadscale area. 
(See map, PI. XLII.) This type of vegetation likewise occurs as islands 
of greater or less extent scattered through the sagebrush zone well 
1 While this plant association is one of the most important in Tooele Valley, it appears to be a much less 
prominent feature of the vegetation in other portions of central and western Utah. 
