DESERT CLIMAXES. 233 



include 13 coming on in 1908; these were quickly reduced to 4 species two years 

 later, when secondary introductions began, of which Pluchea sericea and 

 Isocoma have played an important part. The last named may be regarded 

 as a plant which would be suitable for endurance of the final conditions of the 

 desiccated slopes of this locality. 



"ancient strands. 



"The strands of the Travertine Terraces were on the crest of an arched 

 slope or bajada, which would ultimately be subjected to the maximum action 

 of the wind, which is the more important meteoric feature in this region. In 

 consequence of its action it was not possible to find the ancient beach ridges 

 or the edges of terraces which would correspond in position to the vertical 

 banks wHch marked the mid-winter level of the Salton during the recent 

 period of the lake. But a number of well-marked strands were to be recog- 

 nized, lying at various levels within 100 feet of the level of the ancient high 

 beach-line. These beaches owe their preservation to the fact that they were 

 formed on the concave part of the slope and in places sheltered from the pre- 

 vailing wind and with no run-off. These were well marked to the southward 

 of Travertine Rock and also to the westward. The character of these strands 

 is such that they may not be safely taken for seasonally formed strands, but 

 each one might be considered as marking the maximmn level of the lake at 

 some previous filling. This assumption is supported by the fact that such 

 well-marked beach ridges were not found anywhere near the present level of 

 the lake. 



"Ancient strands of well-marked structure are to be seen on the steep slopes 

 westward of Salton Slough, where a hiU rises to such a height that its siunmit 

 was covered at the highest level of Blake Sea; 83 well-marked beach ridges 

 were seen on the slopes of this hill in 1910. 



"An examination of a strand south of Travertine Rock was made in October 

 1912, and a photograph was taken. The plants marking its position was a 

 comparatively dense desert formation inclusive of Atriplex canescens, Coldenia 

 palmeria, Franseria dumosa, Hymenochloa salsola, Parosela emoryi, and Petal- 

 onyx thurberi, all of which were restricted to a band or zone which varied from 

 12 to 18 feet in width. A second examination of another strand in February 

 1913 included the above except Atriplex canescens. 



"It is notable that Parosela and Atriplex, which are members of this forma- 

 tion, which dates the beginning of its development back for at least a century 

 or two, also appear on similar strands on Obsidian Island and elsewhere shortly 

 after emersion." 



Shantz^ (1916) gives the following summary of plant succession in Tooele 

 VaUey, Utah: 



"The principal plant communities and their relation to the conditions of 

 soil moisture and salinity are presented in the accompanying table compiled 

 from a published account of the vegetation of this valley. To this publican 

 tion' the reader is referred for a detailed account of the vegetation of the valley 

 and of the conditions of moisture and salinity correlated with each type of 

 vegetation. 



'This account is due to the kindness of Dr. H. L. Shantz, Plant Physiologist, Alkali and Drought 

 Resistant Plant Investigations, Bureau of Plant Industry. It is published with the permission 

 of the Secretary of Agriculture. 



T. H. Kearney, L. J. Briggs, H. L. Shantz, J. W. McLane, and R. L. Piemeisel: "Indicator 

 Significance of Vegetation in Tooele Valley, Utah." U. S. Department of Agriculture Jour 

 Agr. Res., Vol. I, No. 5, pp. 365-418. 1914. 



