May 24 ,1924 Significance of the Southwestern Desert Vegetation 
799 
Table XXXIV, 
-Salt content of the soils occupied by the principal plant com 
munities of the Southwestern Desert a 
Creosote bush 
(Corillea glutinosa) 
Desert-sage ( Atriplex 
polycarpa ) 
Seepweed ( Dondia 
torreyana and D. 
intermedia) 
Mesquite and chami- 
so ( Prosopis glandulo- 
sa-Atriplex canescens) 
Depth of 
soil 
Indio, 1915,10 
samples 
Chandler, 11 
samples 
Casa Grande, 
4 samples 
Average 
Indio, 1914, 26 
samples 
Indio, 1915, 10 
samples 
Chandler, 16 
samples 
Casa Grande, 
3 samples 
Average 
Indio, 1914, 9 
samples 
1 Indio, 1915, 6 
samples 
Casa Grande, 
1 sample 
Average 
Indio, 1915,10 
samples 
Chandler, 8 
samples 
St. George, 1 
sample 
Average 
Feet 
1 __. 
0.01 
0.05 
0.02 
0.03 
0.30 
0.26 
0.06 
0.04 
0.17 
1. 55 
1.04 
0.25 
0.95 
0.01 
0.02 
0.12 
0.05 
2__ 
.01 
.04 
.02 
.02 
.45 
.55 
.23 
.07 
.33 
1.25 
.87 
. 50 
.87 
.01 
.06 
.12 
.06 
3___. 
.01 
.05 
.03 
.03 
.33 
.27 
.35 
.08 
.26 
.89 
.73 
1. 04 
.89 
.02 
.08 
.14 
.08 
4.. 
.01 
.08 
.05 
.05 
.31 
.24 
.42 
. 14 
.28 
.77 
.77 
.70 
.75 
.03 
.16 
.19 
.13 
Average_ 
.01 
.06 
.03 
.03 
.35 
.33 
.27 
.08 
.26 
1.12 
.87 
.62 
.90 
.02 
.08 
.14 
.08 
Saltbush and ar¬ 
row-weed ( Atriplex 
lentiformis-Plu- 
chea sericea) 
Saltbush 
(Atriplex lenti- 
formis) 
Pickleweed 
(Allenrolfea 
occidentalis) 
Saltgrass 
(Distichli8 
spicata) 
Depth of soil 
Indio, 1914, 2 
samples 
1 Indio, 1915, 6 
samples 
Average 
Indio, 1914, 2 
samples 
Chandler, 6 
samples 
Average 
Indio, 1914, 7 
samples 
Indio, 1915, 6 
samples 
Average 
Indio, 1914, 3 
samples 
Indio, 1915, 4 
samples 
Average 
Feel 
1... 
1.19 
2.32 
1.76 
>2.50 
0.76 
1.63 
1.78 
2.50 
2.14 
1.80 
2.27 
2.04 
2... 
.66 
.99 
.83 
.44 
.62 
.53 
1.46 
1.64 
1.55 
1.23 
1.30 
1.27 
2... 
.66 
.39 
.53 
.22 
.47 
.35 
1. 21 
1.05 
1.13 
.94 
.70 
.82 
4__.. 
.70 
.35 
.53 
.12 
.61 
.37 
.78 
.46 
.62 
.69 
.37 
.53 
Average... 
.80 
1. 01 
.91 
.82 
.62 
.72 
1.31 
1.41 
1.38 
1.17 
1.16 
1.17 
a All data in this table are stated in percentages of the dry weight of the soil. 
DESERT-SAGE (ATRIPLEX POLYCARPA (TORR.) S. WATS.) 
Probably the largest part of the land now under irrigation in the Coachella 
and Gila Valleys is desert-sage land. While this land is usually slightly saline, 
with irrigation the amount of salt is not prohibitive. Here, as in the case of 
creosote bush land, the condition of the desert-sage means much. Where there 
is a pure good growth of desert-sage the soil is a nonsaline sandy loam, consider¬ 
ably above the water table. Where the growth is poor, however, the salinity 
increases considerably and, in some cases, there is a hardpan. Though the 
saline content is rarely high enough to be serious, yet the silty layers of soil, or 
sometimes the hardpan, may make it difficult to remove the salts by leaching. 
Both fruits and alfalfa are grown on this type of land to a large extent. 
SEEPWEED (DONDIA TORREYANA (S. WATS.) STANDL.) AND DONDIA INTERMEDIA 
(S. WATS.) HELLER 
Seepweed is an almost infallible indicator of alkali. Occasionally land is 
found that is covered with it but is not saline, in which case the growth is weedy, 
coming in on abandoned land where the original vegetation had been destroyed. 
Land covered with a pure growth of it is strongly saline. Even where there are 
other plants and only scattered plants of the seepweed, the soil is usually quite 
strongly saline. If covered with a rank growth of the seepweed the water table 
is sure to be high. Seepweed land requires considerable leaching and often 
draining before it can be used profitably for farming. 
