Changes of Soil Organic Carbon Density and Stock in the Minjiang River Estuarine Wetland under Natural Salinity Gradient
In order to investigate the characteristics of organic carbon density and storage in soil profiles of the Minjiang River estuarine wetlands under different salinity conditions,four natural wetlands,the Tajiaozhou wetland(0.172 mS/cm),the Daoqingzhou wetland(0.175 mS/cm),the Bianfuzhou wetland(0.962 mS/cm)and the Shanyutan wetland(1.392 mS/cm)were selected as the study sites according to the natural salinity gradient.Soil profiles of 100 cm depth were drilled in the four sites,respectively.Soil pH,bulk weight,water content,and total organic carbon content were determined at 2 cm intervals to reveal the variation characteristics of organic carbon density and stock in soil profiles of different wetlands and their influencing factors.The results showed that the organic carbon densities in the soil profiles were 91.16 kg/m2,92.71 kg/m2,63.21 kg/m2 and 98.30 kg/m2 in the Tajiaozhou wetland,the Daoqingzhou wetland,the Bianfuzhou wetland and the Shanyutan wetland,respectively.Soil organic carbon contents in the surface layers of the four wetlands were higher than those in the deeper layers.However,organic carbon densities in deeper layers were significantly higher than those in the surface soils,and organic carbon density increased with the increase of soil depths.The organic carbon stocks in 0～100 cm soil profiles in the Tajiaozhou wetland,the Daoqingzhou wetland,the Bianfuzhou wetland and the Shanyutan wetland,were 455.80 t/hm2,463.55 t/hm2,316.03 t/hm2 and 491.52 t/hm2,respectively.With the increase of local salinity,organic carbon stocks in soil profiles increased,and organic carbon stocks in the deeper layers were higher than those in the surface soil.With the increase of soil bulk density,salinity and depth,soil organic carbon density and stock increased gradually.However,the differences in local environmental characteristics of different wetlands resulted in varying responses of soil organic carbon density and storage to soil water content.We suggest that vegetation types,seasonal hydrothermal variations and human activities are important factors affecting soil organic carbon stocks in wetlands of the Minjiang River estuary.Comparing with other regions in China,the Minjiang River estuarine wetlands have higher soil carbon stocks,and soil types and regional depositional environments are important factors influencing soil organic carbon stocks in different regions.
natural salinity gradientthe Minjiang River estuarine wetlandsoil profileorganic carboncarbon stocks
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