The Origin of the Desert CUmax and CUmate 



By Frederic E. Clements 



IN THE POPULAR MIND, the word "desert"calls to memory a vast 

 sandy waste, typified by a picture o£ the Sahara in the first 

 book of geography. The idea has been further confused by 

 the earher misconceptions concerning the "Great American Des- 

 ert" of the Missouri Valley, which was actually a grassland cUmax 

 (where an unrivaled agricultural development has taken place), 

 and the Great Salt Lake Desert, an alkaline expanse left by the 

 retreat of the lake after glacial times. It is evident that these 

 regions have little in common, apart from the quality of vastness 

 and desolation in human terms. The scientist's usage has natur- 

 ally been more definite, basing itself in part at least upon the 

 physical factors of rainfall and temperature, but even he has 

 sometimes been misled by climatic relicts that have assumed a 

 new role as indicators of disturbance. Cacti in particular have 

 contributed to this result, because they bear the impress of the 

 true desert, but they are often found far beyond its present cli- 

 matic limits. Extensive areas of grassland badly denuded by 

 overgrazing have also been called desert, such as the Red Desert 

 of Wyoming and the southern San Joaquin Valley. However, 

 the latter does have the warrant of a cover of flowery annuals, 

 found likewise in the neighboring Mohave Desert. 



The popular usage finds some justification in the original 

 meaning of the word as "abandoned" and hence uninhabited or 

 uninhabitable. In geographic parlance a desert is a region which 

 has little or no vegetation because of a scarcity of rainfall, and 

 thus is relatively unpopulated; while in ecological terms it is 

 an area marked by a peculiar vegetation or, in places or at times, j 



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