Effects of Abiotic Factors on Plant Community Composition and Functional Traits in the Liaohe Estuary

The composition and functional traits of plant communities and their changes along an environmental gradient are important bases for maintaining the carbon sinks of estuarine wetlands. To clarify the succession pattern of plant community in an estuary along an environmental gradient, this study considered the Liaohe Estuary wetland as the research object and divided the dominant plant community into a Phragmites australis community and high-, medium-, and low-density Suaeda salsa communities. We employed redundancy analysis, variance decomposition, and multiple regression to examine the impact of an environmental gradient on the functional traits and spatial distributions of plant communities in the Liaohe Estuary wetland. The findings revealed that as the elevation decreased, the soil salinity increased and the water content decreased. The distribution of plant communities followed the order of P. australis, high-density S. salsa, medium-density S. salsa, low-density S. salsa, and bare flat areas. When the soil salinity exceeded 21 g/kg and the soil moisture content was below 17%, the conditions were no longer suitable for the growth of S. salsa or P. australis. Soil salinity, total nitrogen content, clay content, and elevation were the most critical environmental factors affecting the functional traits of the plant communities. Soil biochemical characteristics, soil texture, and the physical environment accounted for 28.9%, 23.12%, and 11.51%, respectively, of the variation in the spatial distribution of plant communities. The proportions of the suitable area for the high-, medium-, and low-density S. salsa were 13.1%, 53.78%, and 33.12%, respectively. The results provide a theoretical basis for further elucidating the degradation mechanisms of estuarine wetlands, developing an evaluation index system for estuarine wetland ecological restoration, and optimizing ecological protection and restoration strategies.