Limited release of previously-frozen C and increased new peat formation after thaw in permafrost peatlands

Estop-Aragonés, Cristian, Cooper, Mark D A, Fisher, James P, Thierry, Aaron, Garnett, Mark H, Charman, Dan J, Murton, Julian, Phoenix, Gareth K, Treharne, Rachael, Sanderson, Nicole K, Burn, Christopher R, Kokelj, Steve V, Wolfe, Stephen A, Lewkowiczi, Antoni G, Williams, Mathew and Hartley, Iain P (2017) Limited release of previously-frozen C and increased new peat formation after thaw in permafrost peatlands. Soil Biology and Biochemistry, 118. pp. 115-129. ISSN 0038-0717

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Abstract

Permafrost stores globally significant amounts of carbon (C) which may start to decompose and be released to
the atmosphere in form of carbon dioxide (CO2) and methane (CH4) as global warming promotes extensive thaw.
This permafrost carbon feedback to climate is currently considered to be the most important carbon-cycle
feedback missing from climate models. Predicting the magnitude of the feedback requires a better understanding
of how differences in environmental conditions post-thaw, particularly hydrological conditions, control the rate
at which C is released to the atmosphere. In the sporadic and discontinuous permafrost regions of north-west
Canada, we measured the rates and sources of C released from relatively undisturbed ecosystems, and compared
these with forests experiencing thaw following wildfire (well-drained, oxic conditions) and collapsing peat
plateau sites (water-logged, anoxic conditions). Using radiocarbon analyses, we detected substantial contributions
of deep soil layers and/or previously-frozen sources in our well-drained sites. In contrast, no loss of previously-
frozen C as CO2 was detected on average from collapsed peat plateaus regardless of time since thaw and
despite the much larger stores of available C that were exposed. Furthermore, greater rates of new peat formation
resulted in these soils becoming stronger C sinks and this greater rate of uptake appeared to compensate
for a large proportion of the increase in CH4 emissions from the collapse wetlands. We conclude that in the
ecosystems we studied, changes in soil moisture and oxygen availability may be even more important than
previously predicted in determining the effect of permafrost thaw on ecosystem C balance and, thus, it is essential
to monitor, and simulate accurately, regional changes in surface wetness.

Item Type: Article
Schools and Departments: School of Global Studies > Geography
Depositing User: Sharon Krummel
Date Deposited: 04 Jan 2018 14:06
Last Modified: 04 Jan 2018 14:07
URI: http://sro.sussex.ac.uk/id/eprint/72589

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Project NameSussex Project NumberFunderFunder Ref
Carbon Cycling Linkages of Permafrost Systems (CYCLOPS)G0937NERC-NATURAL ENVIRONMENT RESEARCH COUNCILNE/K000241/1