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Abstract: This chronosequential study focuses on the vegetation succession, pedogenesis, carbon stocks and functionally different carbon pools of post-agrogenic Albeluvisols under self-restoration in the Taiga zone of the European part of Russia. The sites investigated were comparable in terms of climate, soil texture and land-use history, but differed in duration of agricultural abandonment, covering 4, 12, 17 and 68years of self-restoration. During self-restoration, the vegetation showed a development towards a mesophytic spruce forest. Pedogenesis resulted in recovery of morphological and chemical features with a vertical differentiation typical for the undisturbed Albeluvisols. During self-restoration, new organic surface layer (O) and new humic topsoil horizon (Ah) were developed. At the end of the chronosequence, the bottom of the well visible former ploughing horizon showed eluvial characteristics. Simultaneously, leaching caused a pH decrease of about 1.8units, loss of the exchangeable cations, depletion of base saturation from 100% to 18%, and loss of nutrients. A vertical differentiation due to redistribution processes was found for soil organic carbon (SOC) and plant available phosphor and potassium. During self-restoration, the measured carbon stocks did not change substantially in the upper 0.5m, but show a distinct redistribution within different soil layers, causing SOC accumulation from 0.64 to 0.78kgm−2 in the organic surface layers and from 0.75 to 2.64kgm−2 in 0–0.1m, but SOC loss from 3.60 to 1.71kgm−2 in 0.1–0.5m. The simulation results showed also minor alterations for the chronosequence time interval, followed by an increasing SOC sink functioning at long terms of up to 200years. The investigation of functionally different SOC fractions showed a significant enrichment of free particulate organic matter (POM) and occluded POM, hot water extractable carbon (Chwe), and carbon in grain size fractions, significantly following the increase of total SOC during self-restoration. Nevertheless, self-restoration affected the distribution pattern of carbon to functionally different pools, predominantly stimulating SOC sequestration within free POM fraction. Despite all these alterations the study showed no full restoration for the vegetation and the soils within the chronosequential time scale of 68years. [Copyright &y& Elsevier]

This chronosequential study focusses on the vegetation succession, pedogenesis, carbon stocks and different carbon pools of post-agrogenic Calcisol–Solonetz complexes in the dry steppe zone of Russia. The sites were comparable in terms of climate, soil texture and land-use history, but differed in the duration of agricultural abandonment, covering 1, 7, 12, 17 and 42 years of self-restoration. During self-restoration without direct human impact, the vegetation developed towards a steppe with dominance of Artemisia lercheana / pauciflora and Stipa pennata . After 17 years, the abundance of Artemisia pauciflora indicated again the Solonetz locations within the Calcisol–Solonetz complex, which were not visible during arable land use. Pedogenesis resulted in the recovery of the natural soil structure—fine subangular polyhedral for Calcisol and crumble fine platy for Solonetz. The recovery of soil structure of Solonetz was in accordance with a decline of water-stable aggregates from 84% to 68%. The plow features were still well visible after 42 years of self-restoration in both soil groups. Partial integration of Btn materials into the plow layer induced a pH increase during cultivation of the Solonetzes, while slight pH decreases were observed during self-restoration afterwards. Other chemical properties of both soil groups remained unchanged. Post-agrogenic Solonetzes showed an exchange sodium percentage (ESP) below 5.0% and an electrical conductivity (ECe) below 50 mS m − 1 at the topsoil during the period of self-restoration. The development towards natural soils was observed in terms of soil organic carbon (SOC) dynamics. SOC stocks of the Calcisols increased slowly from 2.0 to 3.5 kg m − 2 in the upper 0–0.5 m, comprising 64% of the natural soil. SOC stocks of the Solonetzes grew from 1.7 to 3.1 kg m − 2 in the upper 0–0.5 m and almost reached the level of natural soil already after 12 years of self-restoration. The long-term modelling showed a recovery of SOC stocks almost after 100 years for the Calcisol and the Solonetz chronosequences. The nutrient dynamics traced SOC dynamics during the self-restoration. The investigation of different carbon pools showed a significant organic carbon (OC) enrichment of the density fractions < 1.8 g cm − 3 (free particulate organic material (POM) and occluded POM) and the density fractions > 1.8 g cm − 3 (sand coarse/medium silt, fine silt, clay) following an increase of total SOC during self-restoration. In the Calcisol chronosequence, the dynamics of all fractions was close to the dynamics of total SOC with the exception of free POM showing a moderate accumulation rate in relation to total SOC. Post-agrogenic Solonetzes showed a more intensive accumulation of free POM and a slower OC sequestration in aggregates compared to total SOC. Both chronosequences showed comparable recovery rates for the passive SOC pool and total SOC. Despite all these alterations the study showed no full restoration for many parameters within the chronosequential time scale of 42 years. [ABSTRACT FROM AUTHOR]