Trends of Soil Organic Matter Turnover in the Salt Marsh of the Yangtze River Estuary
长江口盐沼土壤有机质更新特征的滩面趋势

Soil organic matter (SOM) turnover was studied for the Chongmingdongtan Salt Marsh in the Yangtze River Estuary, based on the analyses of stable carbon isotope (δ13C), grain sizes and contents of particulate organic carbon (POC), total nitrogen (TN) and inorganic carbon (TIC) for three cores excavated from high marsh, middle marsh and bare flat. Results indicated that correlations between soil POC contents and δ13C values of the salt marsh cores were similar to those of the upper soil layers of mountainous soil profiles with different altitudes. SOM of salt marsh was younger than 100 years, and originated mainly from materials of soil erosion in the catchment basin of the Yangtze River. Diagrams of TN-C/N, POC-TIC and POC-δ13C for the cores indicated that turnover degree of SOM from the salt marsh was generally low, and tendencies regarding SOM turnover were clear from bare flat to high marsh. Bare flat showed characteristics of original sediments, with minor SOM turnover. The turnover of SOM was discernable in the high marsh and middle marsh, and the mixing degrees of SOM compartments with different turnover rates increased with evolution of the muddy flat. The exclusive structure of muddy layer and sandy layer originated from dynamic depositional processes on tidal flat made great difficulties for vertical migration of dissolved materials, and SOM turnover was then constrained.