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A comparison of methane emissions following rice paddies conversion to crab-fish farming wetlands in southeast China
- Hu, Zhiqiang, Wu, Shuang, Ji, Cheng, Zou, Jianwen, Zhou, Quansuo, Liu, Shuwei
- Environmental science and pollution research international 2016 v.23 no.2 pp. 1505-1515
- aquaculture, aquatic plants, dissolved organic carbon, dissolved oxygen, ecosystems, farming systems, field experimentation, greenhouse gas emissions, methane, paddies, rice, sediments, wetlands, China
- Rice paddies and aquaculture wetlands are typical agricultural wetlands that constitute one of the important sources of atmospheric methane (CH₄). Traditional transplanted rice paddies have been experiencing conversion to pond aquaculture wetlands for pursuing higher economic benefits over the past decades in southeast China. A parallel field experiment was carried out to compare CH₄ emissions from a transplanted rice paddy and its converted crab-fish farming wetland in southeast China. Over the rice-growing season, CH₄ fluxes averaged 1.86 mg m⁻² h⁻¹ from rice paddies, and 1.14 and 0.50 mg m⁻² h⁻¹ for the treatments with or without aquatic vegetation present in the crab-fish farming wetlands, respectively. When averaged across the treatments, seasonal CH₄ emissions from crab-fish framing wetlands were 52 % lower than those from rice paddies. The CH₄ fluxes were negatively related to water dissolved oxygen (DO) concentration but positively related to soil/sediment dissolved organic carbon (DOC) content in crab-fish farming wetlands. Dependence of CH₄ fluxes on DO or DOC was intensified by the aquatic vegetation presence. By extrapolating the present CH₄ emission rate with the current rice paddy-converted aquaculture cultivation area, the seasonal CH₄ emissions from inland aquaculture wetlands during the critical farming stage (20 June to 18 October) were estimated to be 33.6 Gg ha⁻¹ in southeast China in 2012. Rice paddies conversion to crab-fish farming wetlands might have reduced CH₄ emissions by 22–54 % in mainland China. Results of this study suggest that the conversion of transplanted rice paddies to crab-fish aquaculture wetlands for higher economic benefits would also lead to a lower ecosystem CH₄ release rate.