Feb. i6» 1914 
Indicator Significance of Vegetation 
397 
An 8-foot boring made in a portion of the shadscale area where Kochia 
vestita was also abundant gave interesting results as regards the salinity 
of the soil at greater depths than were reached by any of the borings 
included in Tables IX and X. The percentage of salt contents at the 
successive i-foot depths were 0.10, 0.79, 1.02, 0.98, 0.92, 0.88, 0.94, and 
1.02, which indicates a very uniform condition as regards salt content of 
the soil below the second foot and to an unknown depth. 
The differences in the averages for each physical factor as given in 
Tables IX and X scarcely seem of sufficient magnitude to explain the 
separate occurrence of A triplex confertifolia and Kochia vestita in distinct 
associations alternating over large areas, especially when we note that 
some of the borings in typical portions of each association show almost 
identical physical conditions. It is not surprising therefore that the line 
of contact between the two associations is a vague one and that the two 
species mingle on equal terms over areas of considerable extent. Yet 
there is a possible explanation for the alternation of these two types 
which is not brought out by the data given in these tables. In Kochia 
land, because of the less favorable conditions for penetration, the sea¬ 
sonal total of available moisture may not be sufficient to support a stand 
of shadscale in competition with Kochia. 
The distribution of A triplex confertifolia appears to be limited toward 
the upper end of the valley by the occurrence of light, easily permeable 
soil which is free from an excess of salts to a depth of 3 feet or more. In 
such land shadscale can not compete with sagebrush. Toward Great 
Salt Lake it is confined to the drier, better drained land of the hummocks 
and ridges and is excluded from the flats where the soil is excessively 
saline and is wet to the surface during much of the year. 
Areas of very limited extent are found here and there in which the 
shadscale plants are much larger than the average and have a green, 
thrifty appearance, with a notable absence of dead wood. In such spots— 
generally obvious depressions—the soil conditions are more favorable 
than in most of the shadscale area, the salt content being lower and the 
moisture content higher. The results of a boring in one such spot, made 
on July 13, are given in Table XI. 
Table) XI .—Salt content and moisture conditions of the soil in a spot where Atriplex 
confertifolia was exceptionally large and healthy . 1 
Depth (feet). 
Salt content. 
Wilting coeffi¬ 
cient. 
Moisture con¬ 
tent above or 
below wilting 
coefficient. 
1 
0. 06 
20. 5 
— 10. 1 
2 
•05 
17.4 
— 2 . O 
3 
.09 
18.3 
+ 2.8 
4 
.09 
18. I 
0 . 0 
1 All data in percentages of the dry weight of the soil. 
