Ecological stoichiometry characteristics in surface sediments of Sonneratia apetala plantation of different ages in Qinzhou bay

Ecological stoichiometry is an efficient tool to explore the balance and cycling of coupled elements, this study aims to provide a theoretical basis for the scientific management of alien plants by investigating the contents of key elements and their ecological stoichiometric characteristics in the surface sediments of Sonneratia apetala plantations of different ages.

The study focused on three artificially established S. apetala forests of different ages (10, 15, and 20 years) in the Qinzhou bay coastal wetland. Three plots of 20 m × 20 m were set up in each forest age group. Surface sediment samples were collected within each plot using a zigzag pattern to a depth of 0-20 cm. Samples were analyzed to determine the contents of total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), available phosphorus (AP), total sulfur(TS), available sulfur (AS), total potassium(TK), available potassium (AK) and so on. The ecological stoichiometric characteristics of C, N, P and other elements in surface sediments and their influencing factors were studied.

1) The age of S. apetala forests had a significant influence on the physicochemical properties that included TOC, TN, TP, TS and AS, as well as the ecological stoichiometry that contained C/N, C/P, C/S, C/K, N/S, P/S, P/K, and S/K in sediments; 2) The average C/N values of sediments in the study area (20.41) were slightly higher than those of Chinese wetland soils (18.22). Conversely, the mean C/P values (64.91) and N/P values (3.19) were much lower than those of Chinese wetland soils(245.22 and 13.6, respectively). The average C∶N∶P ratio of 20.3 fell within the range of 7.08 to 41.44 that was observed in Chinese wetland soils. (3) Correlation analysis and redundancy analysis revealed that TOC, TN, and TP were the key factors influencing the variation in ecological stoichiometry of surface sediments.

The sediments in the study area were characterized by rich C and P but less N, with a higher mineralization capacity of sedimentary phosphorus. The growth of S. apetala requires a large amount of phosphorus while being limited by nitrogen. During the management process of S. apetala plantations, the diffusion rate of S. apetala can be slowed down by scientifically regulating the sediment organic carbon content and reducing the influx of nitrogen and phosphorus into the estuary, thus reducing ecological risks.