Feb. 16,1914 Indicator Significance of Vegetation 377 
To recapitulate, the dry, well-drained, nonsaline land in the upper 
part of the valley is occupied chiefly by the sagebrush association; the 
dry saline land near the center is covered with a vegetation of Kochia or 
of shadscale; the land in the lower part of the valley, which is often dry 
on the surface but has a moist subsoil, bears a mixed vegetation of 
greasewood and shadscale; while the lowest areas near the lake shore, 
where the soil is strongly saline to the surface and where during much of 
the year even the first foot is wet, bear the salt-flat type of vegetation. 
The grass flats occupy a moist, moderately saline area lying between the 
two preceding. These relationships are shown in Table XVIII, p. 413, 
and are graphically represented in figure 13 on p. 412. 
In the following pages descriptions are given of the several associations 
and other plant communities, arranged in the order shown in Table III. 
SAGEBRUSH ASSOCIATION 
Topographical Relations 
The sagebrush association is one of the most important types of 
vegetation of the Great Basin region. In Tooele Valley (see map, PI. 
XLII) it occurs chiefly on the bench lands which skirt the mountains. 
The best growth of sagebrush (apart from that on the sand hills as 
described later) is found on the alluvial fans which are situated near the 
mouths of canyons. In such places the moisture received directly as 
precipitation is probably supplemented by water from the hills. This 
type of vegetation extends across the southern end of the valley and 
probably at one time formed a continuous belt, although fire and cultiva¬ 
tion have greatly diminished the area originally occupied, especially on 
the east side. Farther down the valley, below the main area occupied 
by this association, sagebrush is found only on sand hills, along drainage 
channels, and in depressions—places where the moisture conditions are 
more favorable and more of the alkali has been leached out than in the 
surrounding areas. 
Botanical Composition 
This association in its typical form is dominated by Artemisia tridentata 
(PI, XUV) as almost the sole woody plant. In less typical phases two 
or three species of rabbit brush (Chrysothamnus) occur. 1 Many species of 
perennial herbs associate with the sagebrush, especially in those portions 
of the area which lie nearest the foothills. The following list includes 
all shrubs and perennial herbs which were noted as belonging to the 
sagebrush association. 
1 These are never abundant and never attain their maximum size where they occur in the typical sage¬ 
brush association in Tooele Valley. They appear more at home where associated with Artemisia on the 
sand hills, and at roadsides and along ditches in areas which were formerly covered with the sagebrush 
association. 
