Integrated Approach to Spatial Assessment of Soil Organic Carbon in the Russian Federation

An approach was developed and tested to spatial assessment of soil organic carbon stock in uniform groups of mineral and organic (litters, peat deposits, and peaty horizons of semihydromorphic soils) soil horizons. Estimation algorithm allowed us to utilize various datasets with different scales, both spatially and attributive sparse data of different veracities, which complemented each other. A series of maps of different accuracies and scales, including coarse-scale maps covering the entire country and more detailed maps for regions well covered with field measurements. Using these maps, the total organic carbon amount and its distribution over different pools in the 30-cm topsoil layer for the entire Russia and for three administrative regions of European Russia (more detailed) were estimated. The soil organic carbon pool of mineral soil horizons was estimated at 101 Gt C, which corresponded to 62% of the total organic carbon stock within the layer of 0–30 cm; 38% is allocated in organic horizons, including 9% in litter horizons (in rapidly decomposing organic pool) and 29% in peat deposit and peaty horizons of semihydromorphic soils. The organic carbon stocks in the 30-cm soil layer gradually increase from the north to the south: from 87 t/ha in Vologda oblast to 91 t/ha in Moscow oblast and 109 t/ha in Rostov oblast. The share of organic horizons in the total carbon stock decreases from the north to the south. Information on the size and structure of organic carbon pools may facilitate more reliable assessments of soil tolerance toward natural and anthropogenic changes and the development of regionally specific land use strategies.