Regradational changes in the chemical properties of postagrogenic soils (review)

This review summarizes information about the properties of postagrogenic soils with a focus on the composition of soil organic matter (SOM) during the natural self-revegetation. Within one landscape zone, from the chronoseries of the plowed horizon with the poorest substrate to the richest, the contrast in changes in acidity, content and reserves of SOM, and its enrichment in N decreases. This trend is also typical for the series of postagrogenic soils “sandy and sandy loam in (sub)taiga – loamy in (sub)taiga – loamy in (forest-)steppe.” In the previously plowed horizon, with the natural self-revegetation, the pH value and the content of mobile K decreases in the (sub)taiga and remains unchanged in the (forest)steppe. The content of mobile P and exchangeable Ca and Mg decreases slightly in the sandy soils of the (sub)taiga and is constant in the loamy soils of the (sub)taiga and (forest)steppe. For the content of SOM and total N, multidirectional trends were noted in the sandy soils at the (sub)taiga and at the loamy soils, an increase or uniform distribution during the self-revegetation in (sub)taiga and (forest)steppe. The mobile fractions of transition metals and Ca as well as active forms of O play an important but not fully understood role in the stabilization and destruction of SOM. In the context of postagrogenic regradative changes in soils, only pilot assessments of the transformation of SOM composition have been carried out.