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Seasonal and spatial variations of methane emissions from coastal marshes in the northern Yellow River estuary, China

Sun, Zhigao, Jiang, Huanhuan, Wang, Lingling, Mou, Xiaojie, Sun, Wanlong
Plant and soil 2013 v.369 no.1-2 pp. 317-333
Suaeda, autumn, emissions, environmental factors, estuaries, inventories, marshes, methane, nitrogen, salinity, sediments, soil water, spring, summer, temperature, temporal variation, vegetation, winter, China, Yellow River
Aims and methods: To evaluate the seasonal and spatial variations of methane (CH4) emissions and understand the controlling factors, we measured CH4 fluxes and their environmental variables for the first time by a static chamber technique in high Suaeda salsa marsh (HSM), middle S. salsa marsh (MSM), low S. salsa marsh (LSM) and bare flat (BF) in the northern Yellow River estuary throughout a year. Results: CH4 emissions from coastal marsh varied throughout different times of the day and significant differences were observed in some sampling periods (p < 0.05). Over all sampling periods, CH4 fluxes averaged between -0.392 mgCH4 m-2 h-1 and 0.495 mgCH4 m-2 h-1, and emissions occurred during spring (0.008 mgCH4 m-2 h-1) and autumn (0.068 mgCH4 m-2 h-1) while sinks were observed during summer (-0.110 mgCH4 m-2 h-1) and winter (-0.009 mgCH4 m-2 h-1). CH4 fluxes from the four marshes were not significantly different (p > 0.05), and emissions occurred in LSM (0.026 mgCH4 m-2 h-1) and BF (0.055 mgCH4 m-2 h-1) while sinks were observed in HSM (-0.035 mgCH4 m-2 h-1) and MSM (-0.022 mgCH4 m-2 h-1). The annual average CH4 flux from the intertidal zone was 0.002 mgCH4 m-2 h-1, indicating that coastal marsh acted as a weak CH4 source. Temporal variations of CH4 emission were related to the interactions of abiotic factors (temperatures, soil moisture and salinity) and the variations of limited C and mineral N in sediments, while spatial variations were mainly affected by the vegetation composition at spatial scale. Conclusions: This study observed a large spatial variation of CH4 fluxes across the coastal marsh of the Yellow River estuary (CV = 7856.25 %), suggesting that the need to increase the spatial replicates at fine scales before the regional CH4 budget was evaluated precisely. With increasing exogenous nitrogen loading to the Yellow River estuary, the magnitude of CH4 emission might be enhanced, which should also be paid more attentions as the annual CH4 inventory was assessed accurately. © 2013 The Author(s).