DMS and CH4 Fluxes Along an Elevational Gradient of a Coastal Salt Marsh, East China: Positive Correlations

The fluxes of methane (CH₄) and dimethylsulfide (DMS) were seasonally measured using static flux chambers over an annual cycle along an elevational gradient of a eastern Chinese coastal salt marsh. To estimate the contribution of higher plants to the fluxes, plant aboveground biomass was experimentally removed and the flux differences between the treatment and the intact were examined. The salt marsh generally functioned as a source for CH₄ and DMS, with the maximum occurring at the cordgrass (Spartina alterniflora) marsh. The mean annual emission rates of CH₄ and DMS were 0.70 plusmn 0.24 mM m^-2d^-1 and 4.59 plusmn 0.97 muM m^-2 d^-1 at the cordgrass marsh (positive for emission and negative for consumption), respectively. CH₄ emission rates were positively correlated to those of DMS, indicating a possible coupling between sulphur and carbon cycles in the study marsh. Comparative analyses showed that higher plants were present as an important source of CH₄, DMS, and accounting for 57.19% and 23.07% of their total emission rates at the cordgrass marsh, respectively. However, the mechanism underlying plant emissions is not clear.