Plant-mediated methane and nitrous oxide fluxes from a carex meadow in Poyang Lake during drawdown periods

Abstract

Plants have been suggested to have significant effects on methane (CH4) and nitrous oxide (N2O) fluxes from littoral wetlands, but it remains unclear in subtropical lakes. We conducted in situ measurement of CH4 and N2O fluxes for two years. To distinguish between the effects of shoots and roots, three treatments (i.e., intact plants as control, shoot clipping, and root exclusion) were used. Effects of plant biomass, temperature, and soil moisture on CH4 and N2O fluxes were analyzed. The mean ecosystem CH4 emission rate was 36 μg CH4 m−2 h−1 for drying periods, but 8219 μg CH4 m−2 h−1 for drying-wetting transition periods. CH4 fluxes were positively correlated with below-ground and total biomass, but not with above-ground biomass. Clipping did not significantly alter CH4 flux rate, but root exclusion decreased the CH4 flux by 116 % as compared to the control. N2O emissions were similar for both the drying and drying-wetting transition periods, with a mean rate of 20 μg N2O m−2 h−1. Both clipping and root exclusion significantly increased N2O fluxes as compared to the control. There was no significant correlation between CH4 and N2O fluxes. Roots dominated plant-mediated enhancement in CH4 fluxes, but played almost an equal role as shoots in plant-regulated suppression on N2O fluxes in this Carex meadow during drawdown periods.