Twelve sites within a north-south climatological transect in Siberia were investigated to classify the soils and to determine their soil organic carbon stocks in the top 30 cm of the active layer (SSOC 30). There was a distinct arrangement into three groups of increasing SSOC 30 within the transect with decreasing latitude. The greatest SSOC 30, with mean values of 24 ± 9 kg m-2 were identified for the southern group of forest tundra and taiga sites on the ancient Central Siberian Plateau. The soils of the sand-dominated north-western part of the Lena River Delta, the second river terrace, had a SSOC 30 of only 4 ± 2 kg m-2 whereas the delta’s third and first river terraces stored on average 12 ± 3 kg m-2 in the top 30 cm of the active layer. The climatological gradient with changing vegetation productivity and different parent materials result in varying pedogenetic processes and were identified as key controls on the soil organic carbon stocks.