EUSSIAN SOIL INVESTIGATIONS. 813 



general absence of structure of the upper horizon contri))ute,s to its 

 pulverization in plowing, resulting- iu an increased capacity for 

 humidity and decreased permeability. 



The su])clays of the wooded steppes occupy in all respects an inter- 

 mediate position between the chernozem and the ''forests" subclaj^s 

 proper, approaching first one then the other in character. By a study 

 of the distri])ution of the forest subclays and the subclays of the 

 wooded steppes in the territory of the chernozems Dokouchayev was 

 able to determine the areas which have been in the past occupied by 

 forests, but which are now under cultivation. Tantil3"ev has latel}- 

 prepared a map of the prehistoric steppes of P]uropean Russia. 

 Wooded steppes and true forest soils extend into Siberia. Soils iden- 

 tical with or very closely resembling them are also found on the plains 

 of western Europe, namely, in Galicia. Hiuigaiy, and in central Ger- 

 man}'. There is little doubt that this type of soils occurs on the 

 American continent where the prairies begin to be replaced by forests. 



Sod and j>odz<>l so'ils. — The Russian term " podzol " very nearly 

 corresponds with the German '" Bleisand" (lead sand), with this differ- 

 erence, however, that the term is applied not only to sandy but also 

 to more stick}-, clayey soils if they have been affected to a marked 

 degree l)y chemical leaching processes under the influence of the sol- 

 vent action of humus acids. In the regions where podzol soils occur 

 the climatic and other conditions are especially fav^orable to the 

 decomposition and leaching of the soil conjstituents by the solvent and 

 reducing action of th« hunms. 



The upper horizon of the podzol is light gray or gray, frequently 

 with a light cinnamon tint, and 1 to \\ dcm. in depth. It has no 

 marked structure, and its coherence varies with the content of clay, 

 sand, and humus. 



The underlying horizon is much lighter, sometimes almost white, 

 sometimes with a yellowish or pale-blue tint. This is the podzol 

 proper. It presents a mass of fine particles, flour-like in a dry state, 

 sticky in a wet state, very rich in silica. The thickness (depth) of the 

 podzol layer varies from a few centimeters to over 4 decimeters. The 

 subsoil or the parent rock is most frequently red-brown sandy morainic 

 clay with pockets of podzol, or argillaceous sand, but the subsoils may 

 also l)e pebbly clays, feebly coherent and friable sands, clay or loamy 

 yielding rocks, or even loess-like deposits. 



When the second horizon is near the surface the whole soil is called 

 podzol; when it is not individualized, indistinct, or entirely absent, a 

 sod or peat soil results. Between the flrst and the second there exist 

 in nature gradual transitions, as can be seen in northern Russia on 

 every cultivated field and under every forest. 



Concretions are ordinarily found in podzol soils in the form of bullet- 

 like grains, small veins, or continuous layers in the lower part of the 



