LAND CLASSIFICATION. 241 



In the West, the climax which serves as the best indicator of crop produc- 

 tion is naturally grassland. As the most extensive of all the formations con- 

 cerned, its various associations serve also to indicate all the types of farming 

 from humid and semi-arid on the east to dry-farming and irrigation farming 

 in the west. While the alpine meadow climax has many points of resemblance 

 to the grassland, it is a clear-cut indicator of grazing land, since neither trees 

 nor crops can thrive in it. The various scrub climaxes, sagebrush, desert 

 scrub, and chaparral, as well as tree and scrub savannah, are primarily indi- 

 cators of grazing land, unless irrigation is resorted to. Dry-farming is pos- 

 sible in certain areas in them, but these are usually in the transition to other 

 formations or in the serai habitats. A notable exception occurs in the 

 Co stal chaparral, in which the winter rainfall makes certain crops possible 

 by evasion of the drought period of summer. The woodland climax is pri- 

 ma dy an indicator of combined forest and grazing land. It has some agri- 

 cultural possibilities, but these are rarely to be realized except under irrigation. 

 Of the three forest climaxes, the Coast forest is a distinct indicator of crop 

 prod rction, and the subalpine forest is just as distinctly an indicator of non- 

 agricultural land. The montane forest in general is like the subalpine in 

 indicating forest-grazing land, but this depends upon the consociation and 

 topography. The yellow pine consociation often indicates agricultural land, 

 but the indication of the community must be checked by the nature of the 

 topography and soil. 



In the case of all climaxes, the relations of formation, association, consoci- 

 ation, and society to each other he at the basis of the indicator correlations of 

 the various communities. The indicator value of an association must be 

 understood with reference to its formation, and that of the consociation with 

 reference to its association. In general, these will be consistent with each 

 other md hence they serve to denote smaller and smaller areas, and particular 

 crops and methods rather than types of practice. This is especially true of 

 the many local groupings of dominants and subdominants. The societies 

 formed by the latter are particularly sensitive indicators of local variations in 

 climax conditions (Shantz, 1911). 



Soi 1 indicators. — The significance of soil indicators is local, as well as sub- 

 ordin? 3 to that of climax or climatic indicators. The soil is especially im- 

 porta , in the actual practice of land classification, since it is more tangible 

 than climate and is subject to much greater local variations. Consequently, 

 in any particular region climax indicators should be employed for general 

 climatic values, while soil indicators should be used for the special values which 

 will determine the proper classification of a particular area. In view of the 

 paramount importance of water-content in arid and semi-arid regions, the 

 genaral correspondence between rainfall and water-content from east to west 

 becc mes especially helpful. While texture and topography will cause soils 

 to va cy much locally in their water-content, the water-content of tillable soils 

 decn ases more or less steadily to the westward or south west ward. This 

 relation of climate and soil is readily seen in the soil regions of the West as 

 recognized by the Bureau of Soils, namely, Great Plains, Rocky Mountain, 

 Southwest Arid, Great Basin, Northwest Intermountain, and Pacific Coast. 

 As would be expected, these regions also show more or less correlation with the 

 climax formations. 



