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Volume 12, issue 16
Biogeosciences, 12, 4965–4977, 2015
https://doi.org/10.5194/bg-12-4965-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 4965–4977, 2015
https://doi.org/10.5194/bg-12-4965-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Aug 2015

Research article | 20 Aug 2015

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China

L. Olsson1,2, S. Ye3, X. Yu3, M. Wei3, K. W. Krauss4, and H. Brix1 L. Olsson et al.
  • 1Department of Bioscience, Aarhus University, Aarhus, Denmark
  • 2Sino-Danish Centre for Education and Research (SDC), Aarhus, Denmark
  • 3Key Laboratory of Coastal Wetlands, China Geological Survey, Qingdao Institute of Marine Geology, Qingdao, China
  • 4U.S. Geological Survey, National Wetlands Research Center, Lafayette, LA, USA

Abstract. Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, Northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4 sources emitting 1.2–6.1 g CH4 m−2 yr−1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature, soil organic carbon and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m−2 h−1) at soil temperatures < 18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m−2 h−1) probably because methanogens were out-competed by sulphate-reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

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Coastal wetlands vegetated by common reed and rice paddies emit significant amounts of methane to the atmosphere whereas sea-blite marshes are net sinks for atmospheric methane. The main controlling factors for the methane emissions are water table, temperature, soil organic carbon and salinity. The methane emissions from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water.
Coastal wetlands vegetated by common reed and rice paddies emit significant amounts of methane...
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