Influence of Wetland Intervention Strategies on Typical Biogenic Elements Distribution of Coastal Zone Soils in the Yellow River Delta

Wetland restoration has led to land-use changes of coastal zone and also effected on soil nutrient distribution and dynamics. To characterize the differences of typical biogenic elements (C, N and P) distribution and trends of soil induced by wetland restoration policy, we studied two intervention strategies which covered woodland or cropland converted into wetland from four wetland use conditions (ash grove (AG), permanent wetland (PW), wheat field (WF) and seasonal wetland (SW)) in the Yellow River Delta (YRD). The results demonstrated that conversion to permanent wetland showed a more or less significant increase in concentrations and stoichiometric ratios of soil C, N and P, while reclamation of seasonal wetland increased soil N and soil P and the ratio of soil N:P (RNP). We observed the mean soil C concentrations of PW and SW increased by 31.1% and 6.3% in the 0-50cm soil profile separately, compared to their former wetland use, confirming powerful C sequestration of coastal wetlands. PW after 25 years of conversion of woodland to wetland showed an increase in soil C:N (RCN, 25.7%) and C:P (RCP, 30.0%) and SW after 12 years of returning cropland to wetland showed an increase by 17.6% in RCN throughout the soil profile, while similar differences of soil in top 5 cm layers turned out to be even apparent in the studied four wetland use conditions, suggesting the varying of different wetland intervention strategies and implementation period. The underlying changes in nutrient distribution and stoichiometric ratio dynamics are mainly due to C sequestration of wetland and N/P fertilization of reclamation. This brings new insights and helps to increase the knowledge the long-term effect of wetland restoration on soil nutrient distribution and trends in YRD. Understanding these effects can provide sensible policymaking for the conservation and management of coastal wetlands, which is helpful to realize ecological functionality of coastal wetland and achieve carbon neutrality in China.