32 



THE SALTON SEA. 



than abstracted by their submergence. In time it is to be expected that rain will restore 

 these over-alkaline soils to substantially their condition before submergence, but the rains 

 of the Cahuilla Basin are not only infrequent but are commonly torrential and run off so 

 quickly that they have little action on alkali other than the washing of the soil surface. 

 Their leaching action will be very slow. 



It must be realized, of course, that all this applies only to silty soils or other soils 

 the texture of which is fine enough to permit significant capillary rise of the soil-water. 

 In sandy soils there is no opportunity for the shoreward seepage, capillary rise, and evapo- 

 ration of the lake water, and there is therefore no tendency for the accumulation of soil 

 alkali shoreward from the retreating water-line. Furthermore, sandy soils are so much 

 more easily penetrated and leached by rain-water that even a very slight or very rapid 

 rain is sufficient to remove their excess alkali. 



From the viewpoint of this volume, the most important matter relating to the soils 

 is their influence upon the distribution of the vegetation. This seems surprisingly slight. 

 The detailed soil study of the Imperial Junction beach was undertaken especially from this 

 point of view and led to the conclusion that no influence of the soil upon the local distribu- 

 tion of the vegetation was discernible. On this beach the vegetation offers two distinctive 

 features: a repeated banding parallel to the water-line, and a thickening in and near the 

 channels of small dry washes coming from the hills. Both of these matters are fully de- 

 scribed in Dr. MacDougal's contribution. It was quite impossible to correlate either of 

 these distribution features with any variation of soil or soil alkali. As a whole the soil 

 was quite uniform both in its physical properties and its alkali-content, but such variations 

 as did exist had absolutely no relation to the presence or absence of vegetal cover. This 

 is shown by the data of tables 3 and 4. Table 3 gives the mechanical analyses, according 

 to the method of the Bureau of Soils, 'U.S. Dept. of Agriculture, of soils taken from the plant- 

 bearing and plantless portions of the beach, respectively. It will be noted that the variations 

 between different samples in the plantless area are greater than the difference between the 

 soils of the two areas. Table 4 gives similar data for alkali content and leads to similar 

 conclusions. The actual causes of the distribution of vegetation as noted relate to water 

 supply and to the position of the shore-line, and are elsewhere fully discussed by Dr. 

 MacDougal. 



Table 4. — Alkali content of soils from plantless and plantrcovered zones, 

 Imperial Junction beach. 2 



1 U. S. Dept. of Agr., Bureau of Soils, Bulletin 84, 1912. 



'The analyses on which tables 2 to 4 were based were made by L. D. Elliott and by the Bureau ol boils. 



