Post-thaw carbon stock variation in a permafrost peatland of the boreal zone.

The current acceleration of permafrost thaw in the discontinuous permafrost of the boreal zone induces large uncertainties regarding the fate of soil carbon. Peatlands are believed to contain about 277 Pg of the total 1670 Pg stored in permafrost soils. In the discontinuous permafrost zone, the thawing of permafrost causes thermokarst features, leading to a succession from forested peat plateaus to non-forested sphagnum bogs. The changes in organic matter accumulation and deep carbon decomposition rates following thaw in permafrost peatlands could have an important impact on the climate system. We measured the total carbon content of peat cores along a thaw chronosequence from forested permafrost peat plateau to collapse-scar bogs. Four transect of four cores each were collected to expose the variations in carbon content at the collapse-scar feature scale as well as at the catchment scale. Loss on ignition, bulk density, carbon content of the organic matter and radiocarbon dating data reveal variability in the response of the total carbon content with time. Contrary to previous studies of this type, preliminary results do not seem to indicate an initial raise in total carbon stock following thaw. The increase in surface peat accumulation of this peatland seems to be largely offset by an increase in deep carbon loss from anaerobic decomposition.