Study On Methane Emission From The Mire And Cultivated Mire Soils In Minjiang River Estuary

To estimate the magnitude of methane emission and to understand temporal pattern of methane emission,the fluxes of methane emission and main influencing factors of scirpus mariqueter wetlands and paddy fields were measured in Minjiang River Estuary.methane emission fluxes(seasonal dynamic)from scirpus mariqueter wetland before the tidewater was 0.39～9.08 mg·m^-2·h^-1,average 4.22 mg·m^-2·h^-1;that after the tidewater was 0.95～12.78 mg·m^-2·h^-1,average 5.82 mg·m^-2·h^-1.Methane emission fluxes(seasonal dynamic)from paddy fields(summer)was-0.16～31.89 mg·m^-2·h^-1.The CH₄ emission had a significant seasonal pattern,with three peaks at late tillering,booting-heading and milky stages During the period of measurement,there was a significantly positive correlation between CH₄ flux and soil temperature at 5cm soil depths,No significant correlation was found between CH₄ flux and soil Eh or air. The average methane emission fluxes(seasonal dynamic)from paddy fields(summer)was 14.88 mg·m^-2·h^-1,it is higher than the scirpus mariqueter wetlands.Methane emission fluxes(diurnal dynamic)from scirpus mariqueter wetlands(the season that plant can growth)was 2.42～12.66 mg·m^-2·h^-1,average 5.91 mg·m^-2·h^-1;Methane emission fluxes(diurnal dynamic)from scirpus mariqueter wetlands(the season that plant was dead)was 0.09～1.30 mg·m^-2·h^-1,average 0.63 mg·m^-2·h^-1.Methane emission fluxes(diurnal dynamic)from paddy fields was 1.67～4.12 mg·m^-2·h^-1.The maximum and minimum were at 14 and 6 o'clock,that the corresponding tempreture(soil temperature at 5cm soil depths and air temperature)were the highest and lowest.There was a significantly positive correlation between CH₄ flux and tempreture.The research resulted that:temperature and Eh of soil were the main factors that effect methane emission quantities,other factors can influence it at a certain extent;To paddy fields,the growth phase of paddy maybe the determinant factor that influence methane emission quantities and water depth have a significant correlation with methane emission.Land use change of marsh under human activity can greatly increase methane emission fluxes from wetlands in Estuary.