May 24, U 24 Significance of the Southwestern Desert Vegetation 
761 
Table XYI .—Soil conditions in an area of narrowleaf saltbush mixed with a poor 
growth of creosote bush , Casa Grande , Ariz., 1915 a > b 
Item 
Depth 
of soil 
Date of 
collection 
Oct. 11, 
sample 
No. 4 
Moisture equivalent. 
Feet 
1 
31.4 
2 
22.2 
3 
35.7 
4 
32.2 
Wilting coefficient... 
1 
17.1 
2 
17.5 
3 
19.4 
4 
17.5 
Moisture content above or below wilt- 
1 
e d 
ing coefficient. 
2 
d 
3 
d 
4 
d 
Salt content... 
1 
.11 
2 
.20 
3 
.24 
4 
.36 
a All data in percentages of the dry weight of the soil. 
b The creosote bush measured from 1 to 2 % feet high. 
c d=dry soil. 
ADAPTATIONS TO PHYSICAL CONDITIONS 
Narrowleaf saltbush has a very shallow root system limiting itself to the upper 
layer of loose soil. More leaves are retained than in the case of the desert-sage, 
and the fruits here are not produced in as great quantities. 
SALTGRASS ASSOCIATION 
TOPOGRAPHICAL RELATIONS 
Large saltgrass areas are not as common in the Southwestern desert region 
as they are in the Great Basin. 
In the Gila Valley the saltgrass areas are insignificant, occurring only as 
scattered small meadows along the river. In Coachella Valley the pure areas 
of saltgrass, that is, the meadows, are small, rarely several acres in extent, and 
are scattered throughout the flat and poorly drained land, the area covered by 
the pickle weed, the saltbush, and the arrow weed. Saltgrass also occurs in all 
parts of the valley around springs, flowing wells, and reservoirs. 
BOTANICAL COMPOSITION 
The saltgrass meadows are usually a sod of pure Distichlis spicata L. Greene, 
but sometimes there are scattered plants of Cressa truxillensis H. B. K. Allen - 
rolfea occidentalis (S. Wats.) Kuntze, Dondia torreyana (S. Wats.) Standi., 
Dondia intermedia (S. Wats.) Heller, Pluchea sericea (Nutt.) Coville, or Atriplex 
lentiformis (Torr.) S. Wats, may be mixed in at the outer edge, according to 
which of the plant groups border the meadow. 
APPEARANCE 
The meadows show a very uniform growth of saltgrass, practically excluding 
all other plants (PL 8, A.) 
In late winter and early spring (January, February, and March) the meadows 
have a “cured grass” color, the saltgrass having made but little growth. Later 
in the season, however, and until late fall the color is fresh green. 
96038—24t-4 
