Permafrost thaw causes large carbon loss in boreal peatlands while changes to peat quality are limited

Rapid, ongoing permafrost thaw of peatlands in the discontinuous permafrost zone is exposing a globally significant store of soil carbon (C) to microbial processes. Mineralisation and release of this peat C to the atmosphere as greenhouse gases is a potentially important feedback to climate change. Here we investigated the effects of permafrost thaw on peat C at a peatland complex in western Canada. We collected 15 complete peat cores (between 2.7 abd 4.5 m deep) along four chronosequences, from elevated permafrost plateaus to saturated thermokarst bogs that thawed up to 600 years ago. The peat cores were analysed for peat C storage and peat quality, as indicated by decomposition proxies (FTIR and C/N ratios) and potential decomposability using a 200-day aerobic incubation. Our results suggest net C loss following thaw, with average total peat C stocks decreasing by ~19.3 +/- 7.2 kg C m-2 over 40 cm below surface) C is lost following thaw (average 26 +/- 7.9 kg C m-2 over