Abandonment of croplands is happening on 220 million ha worldwide and ca. 1/4 of this area is located in Russia. The most massive cropland abandonment in Russian Federation was caused by the collapse of the farming system in the early 1990s. The cessation of cropland cultivation leads to the natural vegetation recovery and contributes strongly to soil restoration by improvement of degraded properties and medium- and long-term carbon (C) sequestration in post-agricultural ecosystems. Succession of natural vegetation and processes of soil recovery after cropland abandonment specific for the local climate. We investigated how the abandonment of arable soils in various bio-climatic regions of Russia affects (i) accumulation of SOC, its composition, stability, and turnover, (ii) soil structure, (iii) microbial and enzymatic activity during the postagricultural restoration of soils. We concluded that the soil type as well as intrinsic pedogenic processes and time since abandonment determine the C sequestration dynamics and the SOC properties. The pattern of SOC sequestration and its stability during post-agricultural restoration are governed by initial SOC stocks in former arable soils, the biochemical composition of above-/belowground inputs, the chemical properties of soils, and the environmental conditions, mainly by aridity. The succession of natural vegetation on the abandoned agricultural lands was accompanied by a clear trend of increasing activity and diversity of microbial functioning and by the specialization of enzymes for the broader chemical composition of C input into the soil as leaf litter. Therefore, the cropland abandonment provides undeniable environmental benefits which include improvement of soil health, increase in plant biodiversity, and climate change mitigation owing to the intensive process of C sequestration in former agricultural lands.
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