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Chinese Journal of Applied Ecology ›› 2023, Vol. 34 ›› Issue (8): 2142-2152.doi: 10.13287/j.1001-9332.202308.001

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Impacts of reclamation marsh restoration on greenhouse gas emission in the Sanjiang Plain, China

ZHAO Yueqin1, MA Xiujing1, ZHAO Wanjing2,3, ZHANG Zhijun2, SUN Xiaoxin1,3*   

  1. 1Ministry of Education Key Laboratory of Sustainable Forest Ecosystem Management, School of Forestry, Northeast Forestry University, Harbin 150040, China;
    2Heilongjiang Sanjiang National Nature Reserve Administration, Fuyuan 156500, Heilongjiang, China;
    3Heilongjiang Sanjiang Plain Wetland Ecosystem Research Station, Fuyuan 156500, Heilongjiang, China
  • Received:2023-04-13 Accepted:2023-05-26 Online:2023-08-15 Published:2024-02-15

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Abstract: To understand the variations in greenhouse gas fluxes during the process of returning cropland to wetland in the Sanjiang Plain, we selected naturally restored wetlands of 4, 7, 11, 16 and 20 years as research objects to compare with a cultivated site (soybean plantation for 13 years) and an uncultivated marsh dominated by Deyeuxia purpurea and Carex schmidtii. We measured carbon dioxide (CO2) and methane (CH4) fluxes using a static chamber-gas chromatography and explored the main influencing factors. The results showed that there were seasonal variations in growing-season CO2 and CH4 fluxes of the restored wetlands, with the seasonal trends in greenhouse gases becoming gradually similar to that of natural marsh with increasing restoration time. The mean growing-season CO2 fluxes increased during the early stage of restoration, but then decreased during the late stage, which decreased from 893.4 mg·m-2·h-1 to 494.0 mg·m-2·h-1 in the 4-year and 20-year sites, respectively. Mean CH4 fluxes increased with restoration time, ranging from a weak CH4 sink (soybean fields, -0.6 mg·m-2·h-1) to a CH4 source of 87.8 mg·m-2·h-1(20-year restored site). The CH4 fluxes of experimental plots were consistently lower than that of natural marsh (96.4 mg·m-2·h-1). Increases in water level and soil conductivity resulting from restoration were the main driving factors for the decrease in CO2 fluxes. The increases in water level and soil dissolved organic carbon resulting from restoration were the primary drivers for the increase of CH4 fluxes in the restored wetlands. The global warming potentials increased with restoration time, ranging from 27.8 t·CO2-eq·hm-2(soybean fields) to 130.8 t·CO2-eq·hm-2(plot of 20-year restoration), which gradually approached that of natural marsh (156.3 t·CO2-eq·hm-2). The emission of GHGs from restored wetlands in the Sanjiang Plain gradually approached those of natural marsh. Further monitoring is required to identify the maturity of restored wetlands for achieving greenhouse gas emissions equivalent to that of natural marshland.

Key words: returning cropland to wetland, CO2 flux, CH4 flux, global warming potential, Sanjiang Plain.