The Spatial Variability Of Soil Organic Carbon Of Cixi Reclamation Area At South Hangzhou Bay

Greenhouse gases emission has caused extensive concern of international community with global warming becoming severe. Soil organic carbon acts as the largest carbon source/sink of atmospheric CO2, which has an enormous impact on the global carbon cycle, thereby causing global climate and ecosystem changes. The activity of reclamation of the coastal wetland significantly changed the physical and chemical properties of soil and impacted the carbon reservoir fiercely. Thus, it is necessary to study the trend and the impact factors of soil organic carbon after reclamation for the further understanding of global atmospheric carbon cycle.In the present study, we tried to clarify the changes of soil organic carbon(SOC) content under different landuse types and reclamation history in Cixi reclamation area at South Hangzhou Bay, which has a long history of reclamation since 1047 and provides a good and special case to study the effect on SOC after reclamation, long-term land use types, such as paddy field, vegetable field and woodland, were involved:(1) During the early period of reclamation, SOC content increased significantly because the input rate of organic fertilizer roots, straw and litter were greater than the output rate of decomposition and mineralization. Then after a long period of reclamation, continuous cultivation exhausted the organic matter in the soil.Therefore, the SOC content decreased. In this progress, TN and TOC showed the same fluctuation trend; (2) Different land use types may have different impact on the SOC content and the order of the magnitude of SOC was expressed as paddy field>vegetable field>woodland>tidal flat>wasteland>reed field. Thus, paddy field can fix carbon more efficient;(3) Surface SOC was more obviously affected by the landuse types and the reclamation years. SOC content showed decrease trend with the soil depth increase for the organic matter difficult to reach the bottom; (4) Correlation analysis showed that there was a significant correlation between total organic carbon content of heavy metals and ratio of carbon to nitrogen,which can affect the activity of soil microhial,thus influence the decomposition of organic carbon and indirectly change the soil organic carbon storageThe physical and chemical properties of soil changes significantly after reclamation.Therefore, it is suggested that site-specific agricultural activities should be adopted to accelerate the desalination and reduce the loss of soil organic carbon.