GENESIS AND GEOGRAPHY OF SOILS--CHANGES IN THE HUMUS STATUS OF FOREST SOILS IN THE EUROPEAN TERRITORY AND SIBERIA AFTER THEIR ABANDONMENT

摘要

For a long period of time here have been several opinions as to the nature and direction of changes that occur in the properties of soils in the course of their development. Some of these opinions were just the reverse: (1) in the soils of dry meadowsherbaceous vegetation causes a total and irreversible replacement of the podzolization process by the sod-forming one [1]; (2) after cutting trees and subsequent cultivation of soils, the soil becomes still more depleted in nutrients and organic matter[2]. Such polar opinions are in many respects due to the fact that there is no clear-cut distinction between the concepts "development" and "cultivation" and also that soil properties of flood-plain meadows are extrapolated to the soils of dry meadows appearing at the site of a former forest. Changes in the status of organic matter and other soil properties in the soils of a forest zone resulting from their agricultural development and subsequent abandonment depend on different factors, including such combinations of these factors as the amount of organic matter in the original forest soil, hydrothermic conditions under a meadow (presence or absence of groundwater inflow from below), herbage composition, and, finally, the nature of cultivation [3].