Modeling CO2 and CH4 flux changes in pristine peatlands of Finland under changing climate conditions

This study predicted the spatiotemporal changes in the CO2 and CH4 fluxes in the pristine peatlands throughout Finland during the 21st century based on 10 km × 10 km grids. The predictions are based on a regional carbon (C) model that emphasizes the mire-type differences in ecohydrology and biogeochemistry. The model was validated by field measurements performed at multiple sites in Finland. A sensitivity analysis demonstrated that the CO2 flux was more sensitive to changes in temperature than to changes in precipitation, and this temperature sensitivity is greater in fens than in bogs. Conversely, the CH4 emission from pristine fens is more sensitive to the changes in precipitation and temperature than pristine bogs. The spatiotemporal changes in the CO2 and CH4 fluxes were calculated based on the country-scale patterns of mire properties (i.e., fen-bog types, vegetation, topography and peat texture) and the ACCLIM climate change scenarios. The results indicate a decreasing CO2 sinks in the country-scale peatlands, and such a decrease will be most noticeable from 2060 to 2099. In addition, the annual CO2 sink value and the annual CH4 source value of the peatlands will decrease significantly in the western areas of the raised bog region, and such changes will be greater in the pristine fens than in pristine bogs. A large fraction of the fens in the raised-bog region and the southwestern part of the aapa-mire region has the potential to shift from CO2 sinks into weak CO2 sources (<20 g C m−2 a−1) by the end of the 21st century. The transition of bogs from centurial CO2 sinks to sources is most notable near coastal areas. These bogs would function as CO2 sources at an average rate of over 40 g C m−2 a−1 for the 21st century under the changing climate scenario.