Long-Term Net Effect of Permafrost Thaw on the Carbon Balance of Boreal Peatlands: Evidence from Several Complementary Approaches
Abstract
Boreal peatlands are historically important ecosystems in global carbon (C) cycling as they are one of the largest stores of soil C as well as a significant source of methane. Increasing temperatures at northern latitudes are accelerating permafrost thaw, threatening the stability of C stores found in peatlands underlain by permafrost. The net effect of thaw on a peatlands C balance occurs on the decadal to century timescale making it difficult to assess. Measured C stocks indicate the net impact of thawing on C balances but do not provide any information on processes; short-term C balances are monitored via surface greenhouse gas (GHG) flux measurements; estimating the age (14C) of respired C determines the contribution of old C to GHG emissions; and observing enzymatic activity may be indicative of controls on decomposition post-thaw. Here we present evidence from these four approaches performed at a single site in boreal western Canada, providing a comprehensive understanding of the C balance in a thawing peatland complex. We observed net losses of 170 - 2 g C m-2 yr-1, the majority of losses occurred in the initial decades post-thaw. Modelled GHG fluxes for a two-year period indicate recently thawed areas have greater net losses via surface GHG exchange. 14C dating of respired C suggests minimal contribution of old C to surface emissions post-thaw. Measured rates of enzymatic activity suggest the majority of microbial decomposition occurs in the upper layers of recently thawed areas, despite waterlogged conditions. Previous research shows that large C stores found in permafrost peatlands are susceptible to losses post-thaw. However, our results suggest that it may only be C accumulated post permafrost aggradation that is vulnerable to loss and C which accumulated prior to this is unaffected, an important factor when considering the contribution of thawing peatlands to the permafrost C feedback.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B12C..05H
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 1640 Remote sensing;
- GLOBAL CHANGE