May 24,1924 Significance of the Southwestern Desert Vegetation 745 
the desert-sage land (Table IX). Where the creosote bush is small, dwarfed, 
and scattered this is particularly true, but where the creosote bush is abundant 
and well developed, the salt content is negligible and the texture of the soil 
lighter. Where the growth of both creosote bush and desert-sage is good in this 
mixed area the land is among the best in this region. Its texture is somewhat 
lighter than typical desert-sage land, making cultivation easier and affording 
better drainage. The land is richer than creosote bush land and, compared to 
desert-sage land, there is less danger of its becoming saline. Its location makes 
irrigation possible where creosote bush land usually is too high. 
Table IX.— Comparison of spring and fall soil conditions at the same station in 
areas where creosote bush was mixed with desert-sage, Chandler , Ariz ., 1915 a 
Date of collection 
Average 
Item 
Depth 
of soil 
March 20, 
sample 
No. 8 
October 5, 
sample 
No. 8 
March 28, 
sample 
No. 27 
October 5, 
sample 
No. 27 
Spring 
FaU 
Moisture equivalent. 
Feet 
1 
6.9 
6.4 
10.0 
11.2 
8.5 
8.8 
2 
14.3 
9.1 
15.6 
15.6 
15.0 
12.4 
3 
20.0 
15.7 
16.0 
16.8 
18.0 
16.3 
4 
12.0 
9.5 
12.9 
17.0 
12.5 
13.3 
Wilting coefficient... 
1 
3.8 
3.5 
5.4 
6.1 
4.6 
4.8 
2 
7.8 
4.9 
8.5 
8.5 
8.2 
6.7 
3 
10.9 
8.5 
8.7 
9.1 
9.8 
8.8 
4 
6.5 
5.2 
7.0 
9.2 
6.8 
7.2 
Moisture content above or below 
wilting coefficient.. 
1 
+1.1 
-2.1 
-1.3 
-3.9 
-0.1 
-3.0 
2 
+5.4 
-1.4 
+2.6 
-3.1 
+4.0 
-2.3 
3 
+4.8 
-4.0 
+0.7 
-2.6 
+2.8 
-3.3 
4 
+3.2 
-2.7 
-0.3 
-2.8 
+1.5 
-2.8 
Salt content... 
1 
.02 
.02 
.06 
.02 
.04 
.02 
2 
.06 
.02 
.19 
.12 
.13 
.07 
3 
.27 
.02 
.46 
.27 
.37 
.15 
4 
.37 
.06 
.46 
.32 
.42 
.19 
a AH data in this table are stated in percentages of the dry weight of the soU. 
DESERT-SAGE ASSOCIATION 
TOPOGRAPHICAL RELATIONS 
The desert-sage association is one of the most important types of vegetation 
in the Southwestern deserts, but is not as wide in range as the creosote bush 
association. It is confined to southern Arizona and California, occurring only 
in the warmest valleys having a low altitude. In the Coachella and Gila Valleys 
it formerly covered larger areas than any other type of vegetation (figs. 2 and 3). 
At the present time much of the desert-sage land is under cultivation. It forms 
practically a continuous belt between the creosote bush area above and either the 
seepweed area or the saltbush and arrowweed area below. The best growth of 
desert-sage is found on the slightly sloping lands that are covered at certain 
times of the year by the flood waters from the adjoining hills. Wherever the 
slope of the land from foothills to valley floor is gradual, the change of soil con¬ 
ditions is also gradual, resulting in alternations and mixtures of the two types of 
vegetation. This gradual change also occurs at the lower edge of the desert-sage 
area where it frequently mixes with seepweed, mesquite thicket or narrowleaf 
saltbush. 
