Mitigation of greenhouse gas emissions from reed canary grass in paludiculture: effect of groundwater level

Combination of rewetting and wetland crop cultivation (paludiculture) is pursued as a wider carbon dioxide (CO2) mitigation option in drained peatland. However, information on the overall greenhouse gas (GHG) balance for paludiculture is lacking. We investigated the GHG balance of peatlands grown with reed canary grass (RCG) and rewetted to various extents. Gas fluxes of CO2, methane (CH4) and nitrous oxide (N2O) were measured with a static chamber technique for 10 months from mesocosms sown with RCG and manipulated to ground water levels (GWL) of 0, -10, -20, -30 and -40 cm below the soil surface. Gross primary production (GPP) was estimated from the above ground biomass yield. The mean dry biomass yield across all water table treatments was 6 Mg ha(-1) with no significant differences between the treatments. Raising the GWL to the surface decreased both the net ecosystem exchange (NEE) of CO2 and N2O emissions whereas CH4 emissions increased. Total cumulative GHG emissions (for 10 months) corresponded to 0.08, 0.13, 0.61, 0.68 and 0.98 kg CO2 equivalents m(-2) from the GWL treatments at 0, -10, -20, -30 and -40 cm below the soil surface, respectively. The results showed that a reduction in total GHG emission can be achieved without losing the productivity of newly established RCG when GWL is maintained close to the surface. Further studies should address the practical constrains and long-term productivity of RCG cultivation in rewetted peatlands.