Climate-Determined Changes of Organic Carbon Stocks in the Arable Chernozem of Kursk Region

Two biogeochemical simulation models describing carbon turnover in soil, the DeNitrification–DeComposition (DNDC) model and the Rothamsted Long-Term Field Experiment Carbon (RothC) model, have been parameterized in accordance with the conditions of arable leached chernozems of Kursk region and validated based on soil СО 2 emission measurement data at Kursk Biosphere Station, Institute of Geography, Russian Academy of Sciences, as a case study on five crops: winter wheat, barley, corn, sunflower, and potato. The modeling has served to reconstruct dynamics of organic carbon content in soil (SOC) over the period of 1990–2018. The RothC model generated the region-specific characteristics of SOC losses, which primarily depend on the weather conditions at an average rate of 342 ± 54 kg С/ha year. The outcomes of the DNDC model are more crop-specific and demonstrate maximal SOC losses under corn (272 kg С/ha year) and maximal accumulation under winter wheat (266 kg С/ha year). The period was characterized by a steady increase in heat supply, including the annual average air temperature (0.68°С/10 years) and growing degree-days (224°С day/10 years). The coefficients of variation of the precipitation and moisture indices in the region exceed 20% over the period. The arable chernozems of Kursk region is characterized by moderate and strong positive correlations between the SOC dynamics and thermal environment conditions including growing degree-days, Selyaninov hydrothermal coefficient, Sapozhnikova moisture index. The contribution of warm-period precipitation is less significant.