Climate and Land Use as Key Factors of the Stability of Organic Matter in Soils

Stocks and biodegradation resistance of organic carbon in soils depend on the combination of external and internal determinants, which control not only the decomposition, but also the stabilization of organic matter (OM). The soil OM stability has been evaluated by (1) specific mineralization rate (SpMinR) for the forest ecosystems located in various climatic zones of Eurasia (temperate, Mediterranean, and tropical) and (2) biological stability index (IBS) determined for the main soil types of European Russia under natural vegetation and agricultural crops. It has been shown that the climate and vegetation type (land use) are the key factors determining the OM stability in soils. For example, close negative correlations of the SpMinR values with the annual precipitation and the mean annual air temperature have been found in soils of the Eurasian transect. It has been revealed that the portion of stable and biologically conserved OM and IBS values in soils under agricultural crops are significantly higher than in soils of natural cenoses.