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

Abstract

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.

Keywords

• azolla
• greenhouse gases
• nutrient loading
• typha
• water table depth