FluxWIN – The role of non-growing season processes in the methane and nitrous oxide budgets in pristine northern ecosystems

The importance of non-growing season greenhouse gas fluxes to annual budgets in pristine northern terrestrial ecosystems is growing in awareness. Greenhouse gas (GHG) fluxes during the non-growing season and freeze-thaw dynamics are still underrepresented and may be a reason why current process-based models underestimate annual methane (CH4) and nitrous oxide (N2O) budgets. The FluxWIN project investigates ecological and biogeochemical processes in global carbon (C) and nitrogen (N) cycles during the non-growing and shoulder seasons by combining high-frequency greenhouse gas measurements, biogeochemical monitoring and process-based modeling. A new automated chamber system was established in 2021 to obtain soil-atmosphere CO2, CH4 and N2O exchange in real time. Additional soil gases and biogeochemical and physical parameters are monitored year-round. We control for climatic variability and quantify differences in non-growing season emissions across the landscape by using a moisture gradient from well-drained upland soils to adjacent wetland ecosystems. The use of these automated high-frequency GHG measurements in combination with biogeochemical monitoring maximizes the likelihood of capturing episodic emissions and their drivers, which are hypothesized to be particularly important during fall freeze and spring thaw periods. The gained information on cold season biogeochemical cycles will improve feedback estimates to climate change by including non-growing season processes in global-scale process-based models