Temperature and the boreal-subarctic maximum in soil organic carbon

On the plains of central North America and western Siberia, soil carbon sto rage and cover by organic soils are highest in the region with mean annual soil temperatures near 0 degreesC, and generally decrease to the north and south. The location of this large soil carbon sink in the boreal and subarc tic is probably due in part to the low heat availability in the soil as com pared to the air in these regions. The thermal advantage of the air environ ment gives green plants a metabolic advantage over decomposers in the soil, which favors soil carbon accumulation. The thermal advantage of the air en vironment relative to the soil is greatest where mean annual soil temperatu res are near or a few degrees below the lower limit of biological activity for cold-adapted soil organisms and plants, i.e. near 0 degreesC.