Species-dependent methane emissions in a Dutch peatland during paludiculture establishment

Paludiculture (crop cultivation on wet peatlands) is an effective means to reduce carbon emissions and nutrient losses from formerly drained peatlands. However, methane (CH₄) emissions and associated pathways may vary substantially between paludicultures, depending on the cultivated paludicrop. Whereas many studies have investigated diffusive CH₄ emissions from paludicrops, large uncertainties exist in relation to the importance of CH₄ ebullition, species-specific differences and seasonal dynamics. In this study we aimed to quantify CH₄ emissions from stands of three paludicrop species, namely Typha latifolia, Typha angustifolia and Azolla filiculoides. CH₄ diffusive fluxes-including plant-mediated emissions-and ebullitive fluxes were studied year-round on a rewetted former agricultural peatland in The Netherlands. Additionally, we tested the effect of irrigation strategy (water table depth) and nutrient loading on CH₄ emissions from stands of both Typha species. Diffusive CH₄ emissions were lowest from A. filiculoides stands (average 15.4 ± 6.6 mg m^-2 d^-1), followed by open water (36.4 ± 6.0 mg m^-2 d^-1). Substantially higher diffusive emissions were measured for both Typha species, with the highest emissions in T. latifolia (187.0 ± 29.4 mg m^-2 d^-1). Ebullitive fluxes were generally low (< 100 mg m^-2 d^-1), but the highest ebullitive fluxes occurred in the A. filiculoides stand, contributing 79 % on average to its total CH₄ emissions. A water table just below the peat surface substantially reduced Typha CH₄ emissions, but also led to lower biomass production, compared to a flooded (+20 cm) water table. Nutrient loading increased biomass production and did not affect diffusive CH₄ emissions. Our results underline that species choice substantially affects paludiculture carbon dynamics in the first phase after establishment. Quantifying both diffusive and ebullitive fluxes is of paramount importance in adequately assessing paludiculture CH₄ fluxes.