Responses of CH₄ emissions to nitrogen addition and Spartina alterniflora invasion in Minjiang River estuary, southeast of China
2014
Mou, Xiaojie | Liu, Xingtu | Tong, Chuan | Sun, Zhigao
The nitrogen (N) input and Spartina alterniflora invasion in the tidal marsh of the southeast of China are increasingly serious. To evaluate CH₄ emissions in the tidal marsh as affected by the N inputs and S. alterniflora invasion, we measured CH₄ emissions from plots with vegetated S. alterniflora and native Cyperus malaccensis, and fertilized with exogenous N at the rate of 0 (N0), 21 (N1) and 42 (N2) g N/(m²·yr), respectively, in the Shanyutan marsh in the Minjiang River estuary, the southeast of China. The average CH₄ fluxes during the experiment in the C. malaccensis and S. alterniflora plots without N addition were 3.67 mg CH₄/(m²·h) and 7.79 mg CH₄/(m²·h), respectively, suggesting that the invasion of S. alterniflora into the Minjiang River estuary stimulated CH₄ emission. Exogenous N had positive effects on CH₄ fluxes both in native and in invaded tidal marsh. The mean CH₄ fluxes of N1 and N2 treatments increased by 31.05% and 123.50% in the C. malaccensis marsh, and 63.88% and 7.55% in the S. alterniflora marsh, respectively, compared to that of N0 treatment. The CH₄ fluxes in the two marshes were positively correlated with temperature and pH, and negatively correlated with electrical conductivity and redox potential (Eh) at different N addition treatments. While the relationships between CH₄ fluxes and environmental variables (especially soil temperature, pH and Eh at different depths) tended to decrease with N additions. Significant temporal variability in CH₄ fluxes were observed as the N was gradually added to the native and invaded marshes. In order to better assess the global climatic role of tidal marshes as affected by N addition, much more attention should be paid to the short-term temporal variability in CH₄ emission.
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