Spatial and Seasonal Variations of Soil Carbon and Nitrogen Content and Stock in a Tidal Salt Marsh with Tamarix chinensis, China

To investigate the spatial and seasonal variations of soil organic carbon (SOC) and total nitrogen (TN) contents and stocks in tidal salt marsh soils, 15 cores to a depth of 40 cm were collected in five sampling sites along a sampling belt during three seasons. Our results showed that higher SOC and TN contents occurred in the surface soils in three sampling seasons. Spatial distributions of SOC and TN showed moderate variability. The C/N ratios were higher in the summer and autumn than in spring. The soil organic carbon density (SOCD) and soil total nitrogen density (TND) ranked in the following order: autumn > spring > summer. And the SOCD values positively correlated with the distances from the tidal creek in summer, while this correlation was negative in autumn and spring. The soil properties, such as the soil moisture, salinity, C/N ratio and C/P ratio, significantly correlated with the SOC and TN contents and stocks. The water and salinity regulation and the alternation of ratios of ecological stoichiometry should be considered to strengthen carbon and nitrogen sequestration in coastal wetlands.