Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach

Area of Science:

• Environmental Science
• Climate Science
• Biogeochemistry

Background:

• Quantifying landscape-scale methane (CH4) fluxes in boreal and arctic regions is crucial for predicting climate change feedbacks.
• Uncertainty exists regarding the relative contribution of high-emission areas versus CH4-consuming areas to landscape-level fluxes.

Purpose of the Study:

• To measure and upscale CH4 fluxes from various microtopographical units in subarctic Finland.
• To compare different methodologies for flux measurement and landcover mapping.
• To assess the impact of climate warming on CH4 emissions in aapa mire regions.

Main Methods:

• CH4 fluxes were measured using static chambers across different microtopographical subunits (lawns, interhummocks, hummocks) and drier ecosystems (lichen heath, birch forest).
• Fluxes were up-scaled using high-resolution landcover maps derived from aerial photography and compared with eddy covariance data.
• Satellite remote sensing was used to quantify the distribution of CH4-emitting and consuming plant communities over a 100 km² area.

Main Results:

• Static chambers and eddy covariance methods showed strong agreement, with the highest emission rates from sedge-dominated lawns.
• Lawn CH4 fluxes correlated strongly with temperature, while water-table depth was not a significant factor.
• Birch forest soils exhibited net CH4 uptake, and satellite data successfully mapped key plant communities for flux up-scaling.

Conclusions:

• The study estimated a total growing season CH4 release of 1.1–1.4 g CH4 m⁻² across the 100 km² area, dominated by lawn emissions.
• Given the temperature sensitivity of lawns and their resistance to drying, climate warming is predicted to significantly increase CH4 emissions in northern Finland and similar aapa mire regions.