High temporal resolution measurements of CO2, CH4 and N2O in a Norwegian mire ecosystem using automated light-dark chambers

Regeneration of natural hydrology in previously drained peatlands is becoming a widespread practice in nature restoration projects around the world. The drained peatlands are well known for their high emissions of CO₂ caused by increased microbial decomposition rates in these very organic soils when suddenly exposed to higher levels of oxygen availability. Restoring natural water levels reduces again the decomposition rates and CO₂ emissions. It remains uncertain, however, how rates of the much stronger greenhouse gases, CH₄ and N₂O, respond to the restored water table and these fluxes can potentially offset the GHG balance of rewetting peatlands.

 

In a new project in Norway (close to Trysil, Innlandet), we installed five ECO₂flux automated chambers and one eddy flux tower in each of two areas of drained peatlands.  The automatic chambers were placed with different distances to the ditches reflecting variation in water table with greatest water level variability at the edges of the ditches. After two years, the ditches will be filled and the natural water table will be regenerated in one of the areas in order to follow the differences in the fluxes of CO₂, CH₄ and N₂O upon rewetting.

 

We here present an analysis of the first year’s data from the ECO₂flux chambers including the total greenhouse gas budget for the period measured. The fluxes of CO₂ showed only little spatial heterogeneity whereas we observed a significant spatial pattern of higher fluxes of CH₄ in plots where the water table was closer to the surface. The driest plots, i.e. the edges of the drain ditches, showed also the lowest emissions of CH₄. The trend was similar in the two areas. This is an indicating that planned rewetting after two years of the project may lead to enhanced production and emission of CH₄ in the area. So far, we observed no N₂O emissions above the detection limit of the system indicating that CO₂ and CH₄ are the major components of the GHG budget.