RÉSUMÉ
Changes in soil organic carbon ï¼SOCï¼ are of great importance to the evolution of soil quality. The distribution characteristics of soil organic carbon ï¼SOCï¼, easily oxidizable organic carbon ï¼EOCï¼, dissolved organic carbon ï¼DOCï¼, and particulate organic carbon ï¼POCï¼ were investigated in the 0-50 cm soil layer of the Phragmites australis, Suaeda salsa, and Tamarix chinensis communities of the supratidal zone in the Yellow River Delta as the research subjects. Then, the composition and sources of soil dissolved organic matter ï¼DOMï¼ were analyzed based on the UV-vis spectroscopy, three-dimensional excitation emission matrix spectroscopy, and parallel factor analysis ï¼PARAFACï¼. Finally, the key factors affecting the characteristics of soil organic carbon and DOM fractions of different plant communities were finally revealed in combination with the physicochemical properties of the soil. The results showed thatï¼ â Comparing different communities, the S. salsa community had the highest ωï¼SOCï¼ at 7.53 g·kg-1, the T. chinensis community had the highest ωï¼DOCï¼ at 0.98 g·kg-1, and the P. australis community had significantly higher ωï¼EOCï¼ and ωï¼POCï¼ than those of the S. salsa and T. chinensis communities at 1.47 g·kg-1 and 0.65 g·kg-1, respectively. The vertical distribution showed a tendency to decrease with deeper soil layers, except for POC concentration. â¡ The main components of soil DOM of the P. australis, S. salsa, and T. chinensis communities were humus, protein-like substances, and fulvic acid-like substances, of which exogenous components accounted for 55.80%, 56.41%, and 52.81% in the above communities, respectively. ⢠Comparing different communities, the humification degree of the P. australis community was significantly higher than that of the S. salsa and T. chinensi communities, but its aromaticity and proportion of biological sources were significantly lower than those of the T. chinensi community. On the vertical profile of the soil, DOM aromaticity and humification degree gradually increased with the deepening of the soil layer, and the deeper soils were mainly dominated by small molecular weight DOM with a lower proportion of hydrophobic fraction. ⣠Redundant analysis showed that N ï¼P<0.01ï¼, NO2--N ï¼P<0.01ï¼, and NH4+-N ï¼P<0.05ï¼ were the key factors affecting the changes in soil organic carbon and DOM fractions.