Organic matter transformation in post-agrogenic soils of the Middle Taiga zone

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Objective. The purpose is to study the organic matter transformation in Podzols from the middle taiga zone.Methods. The study materials are arable lands from the central regions of the Komi Republic. These lands are not agriculturally used since the early 90-ies of the former century. The soil analyses are done according to the common methods.Results. The study allows for the humus profile structure of Podzols along with the following successive stages as meadow idle land young forest dwarf shrub-green moss spruce forest. It also describes the mechanisms of post-agrogenic humus transformation in agricultural sod Podzols due to the self­ restoring succession.Conclusion. Initially, the post-agrogenic soils normally repeat agrozems by characteristics. The upper soil part forms a thin grey-humus (sod) horizon. It contains large amounts of humus, exchangeable cations, and nutrition elements. The specific synthesis and destruction processes of humic substances at the meadow idle land stage change the qualitative humus composition. In contrast with arable lands, the humus composition is dominated with fulvic acids as being best appropriate to the concerned bioclimatic zone. The humuc-fulvic humus composition holds only in the upper old-arable soil part of the meadow idle land. The appearance of pioneer tree species increases the dominating position of FAs and the Cha/Cfa ratio resembles that for forest soil. The organic matter is poor in nitrogen compounds, especially at the young forest stage. By the C/N ratio, the post-agrogenic soils also gradually get close to naturally formed soils under virgin forest.