Comparing greenhouse gas balances from three paludiculture crops after rewetting peat: Typha latifolia, Typha angustifolia and Azolla filiculoides

Abstract

With the increasing demand to reduce greenhouse gas (GHG) emissions to meet the climate goals, rewetting of peatlands has gained attention as a promising measure. To reduce or stop peat oxidation, peat should be brought in anoxic conditions again by elevating the groundwater table. With this action, land becomes less suitable for traditional agriculture. Paludiculture would be a form in which wetland plants are grown and biomass is commercially used.In a field experiment, we studied the effect on GHG emissions from three different paludiculture species: Typha latifolia, Typha angustifolia and Azolla filiculoides. In this presentation we will focus on the following research questions: 1) Can CO2 emission reduction compensate increased CH4 emission when peatland is rewetted for paludiculture purposes? 2) What is contribution of ebullition and diffusive fluxes to the total CH4 flux of the different crop types? 3) What is the contribution of CO2 and CH4 to the total GHG balance with different crop types?From our results we show that all paludiculture crops reduce GHG emission compared to a drained peat meadow, with highest reduction for Azolla and lowest for Typha latifolia. CH4 emission in CO2-eq is as high or higher than the CO2 emission from drained peatland, but is compensated by net CO2 uptake. Typha roots in the sediment (resulting in plant mediated gas transport), which leads to lower contribution of ebullition to the total CH4 flux. Azolla had the highest ebullition rate, but has nevertheless the lowest total CH4 emission. Most probably because Azolla is a floating plant without roots in the soil. This means that less easily degradable carbon is brought into the soil by e.g. root exudates, and that there is also no CH4 transport through the plants.