The Origin of the Desert Climax and Climate 123 



slope of the Sierra Nevada to determine the times of Pleistocene 

 glaciation and has constructed a tentative table of glacial stages 

 in the western United States, in which the four recognized in 

 the Sierran region, namely, McGee, Sherwin, Tahoe, and Tioga, 

 are correlated respectively with the Nebraskan, Kansan, lowan, 

 and Wisconsin of the Middle West. 



Reconstruction of the Clisere or Series of Climaxes 



Methods. — The concepts and methods of paleo-ecology were 

 first developed in Plant Succession (1916:344-362) and were re- 

 capitulated in Scope and Significance of Paleo-ecology (1918). 

 They have been consistently applied by Chaney and his asso- 

 ciates with striking results in a noteworthy series of monographs 

 on western fossil floras, particularly the Bridge Creek, Mascall, 

 and Goshen (Chaney, 1925, 1933). As for the methods employed, 

 the foremost is that of causal sequence, which involves the basic 

 relation of habitat, plant, and animal, and which may be illus- 

 trated by the presence of Stipa in the Florissant Miocene. This 

 suggests not only the existence of prairie but likewise of a grass- 

 land climate and a grazing population. A similar but even more 

 fundamental sequence begins with deformation and finds suc- 

 cessive expression in gradation, climate, and the biome of plants 

 and animals, the latter regularly exhibiting the final effect. Both 

 sequences are concerned in the method of community bonds in 

 which the reactions and coactions of the component species in 

 the complex organism are intimate enough to serve as the essen- 

 tial basis for reconstruction and interpretation. An important 

 corollary of this is seen in the method of succession, especially in 

 the form of the clisere or succession of climaxes in which climatic 

 changes are at work. The essential feature of this is mass migra- 

 tion, with evolution, which yields the method of phylogeny. 



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