Methane oxidation in contrasting soil types: responses to experimental warming with implication for landscape-integrated CH sub(4) budget

• Published in: Global change biology Vol. 23; no. 2; pp. 966 - 976
• Main Authors: D'Imperio, Ludovica, Nielsen, Cecilie Skov, Westergaard-Nielsen, Andreas, Michelsen, Anders, Elberling, Bo
• Format: Journal Article
• Language: English
• Published: 01.02.2017
• Subjects: PN, Arctic; Greenland, Disko I; AN, Greenland
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.13400

Arctic ecosystems are characterized by a wide range of soil moisture conditions and thermal regimes and contribute differently to the net methane (CH sub(4)) budget. Yet, it is unclear how climate change will affect the capacity of those systems to act as a net source or sink of CH sub(4). Here, we present results of in situ CH sub(4) flux measurements made during the growing season 2014 on Disko Island (west Greenland) and quantify the contribution of contrasting soil and landscape types to the net CH sub(4) budget and responses to summer warming. We compared gas flux measurements from a bare soil and a dry heath, at ambient conditions and increased air temperature, using open-top chambers (OTCs). Throughout the growing season, bare soil consumed 0.22 plus or minus 0.03 g CH sub(4)-C m super(-2) (8.1 plus or minus 1.2 g CO sub(2)-eq m super(-2)) at ambient conditions, while the dry heath consumed 0.10 plus or minus 0.02 g CH sub(4)-C m super(-2) (3.9 plus or minus 0.6 g CO sub(2)-eq m super(-2)). These uptake rates were subsequently scaled to the entire study area of 0.15 km super(2), a landscape also consisting of wetlands with a seasonally integrated methane release of 0.10 plus or minus 0.01 g CH sub(4)-C m super(-2) (3.7 plus or minus 1.2 g CO sub(2)-eq m super(-2)). The result was a net landscape sink of 12.71 kg CH sub(4)-C (0.48 tonne CO sub(2)-eq) during the growing season. A nonsignificant trend was noticed in seasonal CH sub(4) uptake rates with experimental warming, corresponding to a 2% reduction at the bare soil, and 33% increase at the dry heath. This was due to the indirect effect of OTCs on soil moisture, which exerted the main control on CH sub(4) fluxes. Overall, the net landscape sink of CH sub(4) tended to increase by 20% with OTCs. Bare and dry tundra ecosystems should be considered in the net CH sub(4) budget of the Arctic due to their potential role in counterbalancing CH sub(4) emissions from wetlands - not the least when taking the future climatic scenarios of the Arctic into account.