In the FluxWIN project, we investigated the seasonal variability fluxes of CO2, CH4, and N2O at a boreal bog and adjacent upland site in Finland. We instrumented a new automated chamber measurement site in the boreal bog, transitional dry bog, and upland forest, with 12 chamberss to measure CO2, CH4, and N2O fluxes and key ancillary data. These measurements ran from 2021 through the end of the project in 2025, although there are data gaps due to instrument failures and other difficulties. Data processing and quality control of this high-frequency chamber and environmental data were completed; data are archived on Pangaea.de. In addition, we measured CH4 fluxes using manual chambers in 2021 and 2022 from vegetation removal experiments to determine seasonal differences in methane (CH4) production, oxidation and plant transport in a boreal bog and effect on net CH4 emissions. Stable isotopes of CO2 and CH4 were also measured using both manual and automated chambers to better understand the processes resulting in methane emissions and as a proof of concept.
Capturing the spatial variability in CH4 fluxes and relative differences in CH4 production, oxidation, and transport was also a significant area of work during the project. We measured CH4 and CO2 fluxes on multiple field campaigns and expeditions, including Alaska 2021, Western Alaska 2023, Western Alaska 2024, Finnish Lapland 2022, mainly using both manual chambers. These measurements showed the spatial variability in CH4 emissions at many wetland sites, including ones affected by permafrost thaw. We also assessed the potential CH4 production across many different soils, including ones sampled in the expeditions, our boreal bog site, and earlier samples from Siberia by developing the instrumentation and protocol for soil incubations during the FluxWIN project. We applied this technique to look at interactions between carbon and nitrogen, the temperature response of respiration in the Sphagnum mosses, and how these affected CO2 and CH4 production under aerobic and anaerobic conditions. We looked more broadly at spatial variability in CH4 production, in well- and poorly- drained soils in Siberia, floodplains, permafrost soils on the north slope of Alaska, and finally a permafrost peatland thaw chronosequence in Finnish Lapland. To better interpret these data, we also used advanced microbial techniques (metagenomic sequencing) and to analyze functional metabolic pathway potentials as well as methanogen and methanotoph abundance from qPCR analysis.
In addition to the scientific insights generated with the chamber work, this FluxWIN work also formed the basis for technological developments. We tested several novel CH4 sensors for application in wetland conditions, including their sensitivity to temperature, methane, and biogenic VOCs in synergetic activities with other EU and ERC projects. We developed a software tool for the processing and quality control of automated chamber data as well as gap-filling methodology and developed methodology to upscale our plot-level chamber measurements to the landscape scale using UAS-derived land cover classifications. Finally, using our developed expertise in chamber methods and measurements from Siikaneva, we conducted a survey of experts to assess researchers implementation of chamber methods and quantify the effects of researchers decisions during data processing on flux data. These showed strong variation among researchers that can contribute substantially to difficulties comparing CH4 flux values among different research groups.
Together, these achievements showed important insights into the seasonality of CH4 cycling in boreal wetland ecosystems. We also developed insights into landscape-scale controls on methane and CO2 cycling following permafrost thaw using experimental incubations, field measurements, and data synthesis and review.
