May 24 ,1924 Significance of the Southwestern Desert Vegetation 771 
Salinity 
The average amount of salt in the first foot of this type of land of all the sam¬ 
ples in Coachella Valley is more than per cent (Table XXXIV). The aver¬ 
age for the second foot is over per cent, and for the third and fourth 
about per cent. The decrease in salinity is probably due to the light 
texture of the soil underlying the upper 2 feet and to the constant addition of 
water that is only slightly saline. 
Summary of Physical Conditions 
Arrowweed and saltbush land in Coachella Valley are characterized by (1) 
a soil, the upper 2 feet of which is quite comparable to that of the pickleweed 
land, but underlying which there is a much coarser soil; (2) a high water-table 
making moisture available, at least below the surface foot, all the year round; 
and (3) usually a high salt content in the surface foot, considerably less so in 
the second, and moderate amounts in the third and fourth feet. 
ADAPTATIONS TO PHYSICAL CONDITIONS 
In Coachella Valley, the arrowweed and saltbush are usually mixed, especially 
on lands that have been disturbed or have become saturated from flooding or 
seepage. On flooded lands these plants remain only until the water is exhausted 
and then give way to the desert-sage or more drought-resistant shrubs. 
In seepage or constantly flooded areas, if the supply of moisture remains suf¬ 
ficient, the plants develop to their fullest and form the thickets mentioned. 
Though the soil requirements of these two plants are alike to a great extent, the 
arrowweed can endure much drier soil conditions, while the saltbush can with¬ 
stand soils that are much more saline. 
Table XXIII.— Soil conditions in September and October in areas of saltbush f 
mixed areas of saltbush and arrowweed , and in areas of arrowweed , Indio , Calif. f 
1914 a 
Item 
Depth of soil 
Saltbush 
Saltbush and 
arrowweed 
Arrowweed 
Average 
Date of 
collection 
Average 
j 
Date of 
collection 
Average 
1 
Date of collection 
Sept. 29, sample 
No. 50 
Oct. 15, sample 
No. 91 
Oct. 14, sample 
No. 82 
Oct. 14, sample 
No. 83 
Sept. 15, sample 
No. 18 
Sept. 6, sample 
No. 60 
Oct. 7, sample 1 
No. 65 
Oct. 7, sample 
No. 68 
Oct. 7, sample 
No. 69 
Oct. 7, sample 
No. 70 
Feet 
Salt content. 
1 
>2.50 
>2.50 
>2.50 
2.10 
0.28 
1.19 
0.07 
0.23 
0.26 
>2.50 
0.43 
0.36 
0.64 
2 
.19 
.68 
.44 
.21 
1.10 
.66 
.06 
.19 
.24 
1.20 
.22 
.24 
.33 
3 
.24 
.19 
.22 
.22 
1.10 
.66 
.02 
.18 
.21 
.96 
.22 
.20 
.30 
4 
.11 
.12 
.12 
.11 
1.28 
.70 
.12 
.22 
.18 
.82 
.20 
.20 
.29 
Water content_ 
1 
6 w 
w 
sa 
w 
nd 
d 
d 
w 
d 
d 
2 
w 
w 
sa 
w 
sm 
sm 
sm 
w 
d 
sm 
3 
w 
w 
sa 
w 
sm 
sm 
sm 
w 
sm 
m 
4 
w 
w 
sa 
w 
sm 
sm 
m 
w 
m 
m 
Soil type.. 
1 
c si 
fsl 
fsl 
fsl 
fsl 
si 
fsl 
si 
fsl 
fsl 
2 
si 
fsl 
fsl 
fsl 
fsl 
si 
fsl 
si 
fsl 
fsl 
3 
si 
fsl 
fsl 
fsl 
fsl 
si 
fsl 
si 
fsl 
fs 
4 
si 
fsl 
si 
si 
fsl 
c 
fsl 
si 
fsl 
fs 
a No soil moisture or moisture equivalent determinations were made on the 1914 soil samples. The data 
given are the field notes on the soil samples. Salt content data are stated in percentages of the dry weight 
of the soil. 
L b fcd=dry soil; nd=nearly dry soil; m=moist soil; sm=slightly moist soil; w=wetsoil; sa=saturated soil. 
c s=sand or sandy; l=loam; fsl*=fine sandy loam; c=clay. 
