Mineralogical Composition of Silt Fractions and Its Transformation under the Impact of Different Cenoses in Model Lysimeters

摘要

A lysimetric experiment has made it possible to trace changes in the fine and medium silt fractions of soils developing from the noncalcareous mantle loam under typical phytocenoses of the southern taiga zone during a 33-year-long period. The silt fractions were separated by the Gorbunov method, and their mineralogical composition was analyzed by X-ray diffractometry. The fine silt fraction consists of quartz, kaolinite, chlorite, hydromica, smectite, and feldspars, The medium silt fraction consistsof quartz, kaolinite, mica, and feldspars. In both fractions, the content of feldspars in the upper horizons has increased in comparison with the initial patent material due to the physical disintegration of coarser fractions. The chemical decompositionof mica has been registered in the layer of 10-30 cm. In lysimeters under artificially planted mixed forest cenoses, acidic hydrolysis may take place at this depth. Cryogenic processes play an important role in the soil formation at the early stages.