title: Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach.
abstract: Quantifying landscape-scale methane (CH4 ) fluxes from boreal and arctic regions, and determining how they are controlled, is critical for predicting the magnitude of any CH4 emission feedback to climate change. Furthermore, there remains uncertainty regarding the relative importance of small areas of strong methanogenic activity, vs. larger areas with net CH4 uptake, in controlling landscape-level fluxes. We measured CH4 fluxes from multiple microtopographical subunits (sedge-dominated lawns, interhummocks and hummocks) within an aapa mire in subarctic Finland, as well as in drier ecosystems present in the wider landscape, lichen heath and mountain birch forest. An intercomparison was carried out between fluxes measured using static chambers, up-scaled using a high-resolution landcover map derived from aerial photography and eddy covariance. Strong agreement was observed between the two methodologies, with emission rates greatest in lawns. CH4 fluxes from lawns were strongly related to seasonal fluctuations in temperature, but their floating nature meant that water-table depth was not a key factor in controlling CH4 release. In contrast, chamber measurements identified net CH4 uptake in birch forest soils. An intercomparison between the aerial photography and satellite remote sensing demonstrated that quantifying the distribution of the key CH4 emitting and consuming plant communities was possible from satellite, allowing fluxes to be scaled up to a 100 km(2) area. For the full growing season (May to October), ~ 1.1-1.4 g CH4  m(-2) was released across the 100 km(2) area. This was based on up-scaled lawn emissions of 1.2-1.5 g CH4  m(-2) , vs. an up-scaled uptake of 0.07-0.15 g CH4  m(-2) by the wider landscape. Given the strong temperature sensitivity of the dominant lawn fluxes, and the fact that lawns are unlikely to dry out, climate warming may substantially increase CH4 emissions in northern Finland, and in aapa mire regions in general.
authors.affiliation: Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4RJ, UK.
authors.forename: Iain P
authors.initials: IP
authors.lastname: Hartley
authors.affiliation: Department of Earth and Environmental Science, University of St Andrews, St Andrews, KY16 9AL, UK.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Hill
authors.affiliation: School of Geosciences, University of Edinburgh, Edinburgh, EH3 3JN, UK.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Wade
authors.affiliation: School of Geosciences, University of Edinburgh, Edinburgh, EH3 3JN, UK.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Clement
authors.affiliation: School of Geosciences, University of Edinburgh, Edinburgh, EH3 3JN, UK.
authors.forename: John B
authors.initials: JB
authors.lastname: Moncrieff
authors.affiliation: Department of Geography, University College London, London, WC1E 6BT, UK.
authors.forename: Ana
authors.initials: A
authors.lastname: Prieto-Blanco
authors.affiliation: Department of Geography, University College London, London, WC1E 6BT, UK.|NERC National Centre for Earth Observation (NCEO).
authors.forename: Mathias I
authors.initials: MI
authors.lastname: Disney
authors.affiliation: NERC National Centre for Earth Observation (NCEO).|School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE, UK.
authors.forename: Brian
authors.initials: B
authors.lastname: Huntley
authors.affiliation: School of Geosciences, University of Edinburgh, Edinburgh, EH3 3JN, UK.|NERC National Centre for Earth Observation (NCEO).
authors.forename: Mathew
authors.initials: M
authors.lastname: Williams
authors.affiliation: Queen's School of Engineering, University of Bristol, Bristol, BS8 1RJ, UK.
authors.forename: Nicholas J K
authors.initials: NJ
authors.lastname: Howden
authors.affiliation: School of Life Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Wookey
authors.affiliation: School of Biological and Biomedical Sciences, University of Durham, Durham, DH1 3LE, UK.
authors.forename: Robert
authors.initials: R
authors.lastname: Baxter
mesh_terms: D001110:Arctic Regions; D057231:Climate Change; D005387:Finland; D065928:Forests; D008697:Methane / Q000378:metabolism*; D053833:Wetlands
chemical_list: D008697:Methane
keywords: Aapa mire; Arctic; climate change; eddy covariance; methane oxidation; methanogenesis; remote sensing; static chambers