Climate warming and the carbon cycle in the permafrost zone of the former Soviet Union

Abstract

AbstractThe continuous permafrost zone of the former Soviet Union (FSU) occupies 5% of the land surface area of the earth and stores a significant amount of carbon. Climate warming could disrupt the balance between carbon (C) accumulation and decomposition processes within the permafrost zone. Increased temperatures may accelerate the rate of organic matter decomposition. At the same time, the productivity of vegetation may increase in response to warming. To assess the future carbon cycle within the permafrost zone under a climate‐warming scenario, it is necessary to quantify present carbon pools and fluxes. The present carbon cycle was assessed on the basis of an ecosystem/ecoregion approach. Under the present climate, the phytomass carbon pool was estimated at 17.0 Gt (109 t). The mortmass (coarse woody debris) carbon pool was estimated at 16.1 Gt. The soil carbon pool, including peat‐lands, was 139.4 Gt. The present rate of carbon turnover was 1.6 Gt/yr. Under a warming climate 0.46–0.72 Gt C/yr may be gradually released to the atmosphere, mainly due to the increase in mortmass and litter decomposition. The increased efflux may be concurrently balanced by carbon uptake by vegetation as a result of enhanced productivity and forest migration to the north. However, the possibility exists that a lag between increased carbon efflux and uptake by vegetation may occur. The equilibrium of the carbon cycle may be reestablished, but at a higher rate of carbon turnover. Climate warming may not influence the depth of the active layer in peatlands. The depth of the active layer in mineral soils was comparable with the depth of the organic layer. Consequently, degradation of permafrost may not have a substantial influence on future carbon emissions.