Variability: Variability of soil organic carbon after freshwater restoration in degraded wetlands of the Yellow River Delta, China

Background/Question/Methods and Results/Conclusions

The lackage of water is one of the reasons of the wetlands degradation. Changing the supply of freshwater supply is one of the important methods to restore degraded wetlands. To evaluate the effects of restoration on the changes of soil organic carbon (SOC), soil samples were collected from both restored wetland sites and adjacent unrestored wetland sites located in the Yellow River Delta, P.R. China, seven years after the beginning of freshwater restoration. The results indicated that SOC was significantly increased in all restored wetland sites of three plant communities. Principal component analysis showed that the restored sites had more soil organic carbon, total nitrogen, and water, while the unrestored sites had higher pH and salinity. The differences between the restored and unrestored sites varied among plant communities and soil depths. In general, the upper soil layer (0 – 20 cm) had larger amounts of organic carbon than the lower soil layer (20 – 40 cm). The increasing of SOC was higer in Suaeda salsa community (6.89±0.63g.kg^-1 ) and Phragmites communis community ( 4.11±0.12 g.kg^-1) than in Tamarix chinensis community (1.40±0.31 g.kg^-1 ) in the upper soil layer after restoration. The differences were strongly significant between restored and refernce wetlands for SOC and TN in the Phragmites communis communities.The relationships between SOC and other soil characteristics changed after the restoration. Soil total nitrogen had significant positive correlations with SOC. The C:N ratio of the soil significantly increased between restored and reference wetlands for Suaeda salsa community. Although C:N ratioes of soil increased after restoration, they were all lower than 25 in the study sites. Biomass significantly increased in the Suaeda salsa community and Tamarix chinensis community after restoration. Our results provided important information on the factors affecting SOC after the freshwater restoration in degraded wetlands of the Yellow River Delta, China.