Organic carbon stocks in the Russian Chernozem

Chernozems (Mollisols) play an important role in the global carbon cycle, but their contribution to the global carbon stock is often underestimated. We have estimated stocks of organic carbon in the upper 2 m in the Russian Chernozem (Haplic Chernozem) under four management regimes: a native grassland (not cultivated for at least 300 years), an adjacent continuous fallow field, a yearly-cut meadow and an arable field in the Kursk region of Russia. The organic carbon stored in the top 2 m was 462 t ha(-1) for the grassland, 451 t ha(-1) for the yearly-cut meadow, 387 t ha(-1) for the arable field and 349 t ha(-1) for the continuous fallow. From 18 to 26% of the total organic C in the top 2 m was between 1 and 2 m in all four regimes. Vertical distribution of organic C was modelled by an exponential function for which the R-2 values lay in the range 0.89-0.95, depending on the regime. This exponential function was used to predict organic C below 2 m in the Haplic Chernozem. Model estimates showed that if we include organic C stored in the Russian Chernozem between 1 and 3 m we shall increase our estimates of C stored by 27-30%.