412 
Journal of Agricultural Research 
Vol. I, No. s 
owing to the bright-red color then assumed by the plants. Scattered 
individuals of this species were also observed far out on the otherwise 
bare salt flats. 
CORRELATIONS BETWEEN THE TYPES OF VEGETATION AND THE 
CHARACTER AND PRODUCTIVITY OF THE LAND 
CORRELATIONS WITH PHYSICAL CONDITIONS 
The natural vegetation of Tooele Valley consists of a few easily recog¬ 
nizable plant communities, the distribution of which is largely determined 
by the moisture relations and the salt content of the soil. The areas 
occupied by each community are rather sharply delimited, although 
Fig. 13. —Diagram showing the characteristic root development of the dominant species of each of the 
principal types of vegetation of Tooele Valley, and indicating the average conditions of soil moisture and 
salinity of the corresponding types of land. The double hatching indicates soil containing an excessive 
quantity of salt (more than 0.5 per cent) and containing moisture available for growth (above the wilting 
coefficient) during the summer. The single hatching indicates soil containing more than 0.5 per cent 0/ 
salts and no moisture available for growth during the summer. No hatching indicates soil containing 
less than 0.5 per cent of salts and no moisture available for growth during the summer. A, Artemisia 
tridentata; B, Kochia vestita; C, Atriplex confertifolia; D, Sarcobatus vermiculaius; E, Allenrolfea occiden - 
talis; F, Salicornia utahensis; G, Distichlis spicata. 
along their boundaries, where the soils are of an intermediate character, 
the vegetation is more or less mixed. Where, as a result of the removal 
of the original vegetation by fire or by the plow, secondary plant commu¬ 
nities have developed, the correlations between the vegetation and the 
physical properties of the underlying soils are not always well marked. 
But with these exceptions, which have been sufficiently discussed on 
preceding pages, all important variations in the character of the soil are 
clearly expressed in the appearance and botanical composition of the 
plant covering. In other words, the principal types of vegetation, where 
typically developed, are reliable indicators of the physical conditions of 
the environment. These correlations are stated in Table XVIII, which 
follows, and are graphically represented in figure 13. 
