Spring soil CO2 and CH4 emissions in the Yellow River Delta wetland, China

Climate change has become a global concern. Coastal wetlands play an important role in the global carbon cycle and significantly contribute to the emission and absorption of the greenhouse gases CO2 and CH4. In this study, the temporal and spatial variations of soil CO2 and CH4 emission fluxes, soil total carbon, total organic carbon, and carbon and nitrogen stable isotopes of four vegetation areas (Suaeda salsa, Phragmites australis, Tamarix chinensis, and farmland) and a bare beach in the Yellow River Delta wetland were observed in the spring of 2011-2013. Soil organic carbon delta 13C ranged from -25.43--23.69 parts per thousand and soil organic carbon content from 0.311 to 1.42%, and the two were significantly negatively correlated, indicating a low decomposition degree of soil organic matter. The soil CO2 emission fluxes in the study period were carbon emissions. In the area with mainly Tamarix chinensis, the 3-year average CO2 emission flux was the highest, in the area with predominantly Phragmites australisthe lowest. The soil CH4 emission flux in the spring of 2011 was a carbon absorption, whereas it was a carbon emission in the spring of 2012 and 2013. Its 3-year average was the highest in the bare beach area and the lowest in the Tamarix ramosissima area. Based on Pearson correlation analysis combined with RDA and multiple linear regression analysis, we found that the main factors affecting soil CO2 and CH4 emission fluxes may be the fast decomposition rate of soil organic matter, the content of soil carbon and organic carbon, and the low degree of soil organic matter decomposition.