256 PLANT SOCIOLOGY 



atmospheric moisture, and evaporation are the cardinal cHmatic 

 factors in soil formation (see also Meyer, 1926). 

 These climatic factors affect : 



1. The rate and kind of mineral weathering. 



2. The rate and kind of decomposition of organic matter and the accumulation 

 and distribution of humus in various layers. 



3. The transfer of substances from one layer to another and the removal of 

 substances from the soil. 



Compared to the climatic factors, the nature of the organic sub- 

 stratum plays only a minor role in soil formation. The production of 

 organic matter and the kind and intensity of its effects are, like the 

 soil-forming processes themselves, subject to the cHmate. 



Climatic Classification of Soils. — The climatic classification of soils 

 had its origin in Russia, the land of boundless steppes, with uniform 

 conditions of relief and vegetation. 



Next to Dokutschajev and Sibirzev, GHnka has done most to 

 advance the climatic classification of soils. Ramann, Stremme, and 

 Lang have followed him in Germany; Treitz in Hungary; Wiegner and 

 his collaborators in Switzerland; and Marbut (1928) and Shaw (1928) 

 in America. 



Glinka's division of soils upon a genetic basis forms the starting 

 point of modern soil classification. According to him (1914), two 

 genetically different primary soil forms are to be distinguished : 



1. Ectodynamomorphic soil; in which soil formation is predominantly condi- 

 tioned by the climate and the resulting vegetation. 



2. Endodynamomorphic soils; in which soil formation is chiefly conditioned 

 by the character of the underlying rock. 



The ectodynamomorphic, climatically conditioned soils are, like the 

 climax regions of vegetation, more or less geographically arranged. 

 They are in an advanced stage of maturity and greatly predominate. 



The endodynamomorphic soils are either limited to desert and 

 mountain regions with sparse vegetation or they are to be considered 

 merely as early stages of development of the ectodynamomorphic 

 climax soils. 



According to their moisture and humus content, which depends 

 upon climate, these soils can be brought under three main groups.^ 

 The classification of the soil types of the earth thus broadly conceived 

 is based therefore entirely upon the ectodynamomorphic soils : 



1 Instead of three main types, Glinka (1914, 1927) distinguishes five: laterite, 

 podsol, tschernosem, solonetz, and soils of swamps, which he divides into numerous 

 subtypes. 



