Accumulation and Distribution of Soil Organic Carbon in <i>Phragmites communis</i> Wetlands Restored with Ecological Engineering

Soil organic carbon (SOC) is vital for the global carbon cycle and balance. In order to study the factors that affect the changes of SOC at different levels (0 ~ 20 cm, 20 ~ 40 cm) in degraded areas and continuous water supply area (3 years, 5 years, 7 years), Phragmites communis wetland of the Yellow River Delta were sampled. The results showed that the upper soil layer (0-20cm) had more SOC than the lower soil layer (20-40cm) in the restored sites. The SOC increased in the 0-20cm soil layer from 7.710±0.756 g/kg to 16.96±0.213 g/kg. Soil salinity and pH value decreased with the freshwater restoration, while SOC increased with the restoration time. SOC had extremely significantly negative correlation with pH (r = -0.564, P < 0.01). The correlation analysis of soil properties showed that SOC had significantly positive correlation with total nitrogen (TN) and NH4+-N (P <0.01) and had negative correlation with C/N. It suggested that wetland restoration not only increased soil organic carbon content, but also improved the ability of nitrogen mineralization.