Tidal regime is recognized as a vital hydrological process in the restructuring of saltmarsh vegetation communities, resulting in differing edaphic conditions and ecosystem functions. Ample studies have focused on the context-dependent effects of tidal disturbance on saltmarsh vegetation worldwide, particularly trait-based responses to physical factors; however, to our knowledge, there are few insights into the edaphic conditions and responses of saltmarsh plants as well as plant-soil systems to tidal disturbance gradients in the Yellow River Delta (YRD), a temperate estuary in northern China. Here, we conducted field surveys and experimental fieldwork at four distinct sites that varied with tidal regime. Site-specific effects of tidal disturbance on the annual saltmarsh foundation plant Suaeda salsa, as well as their edaphic surroundings, were analyzed. Our results showed that trait-based responses largely explained the tidal disturbance impacts on S. salsa; moreover, the edaphic environment differed significantly among sites. We found that flooding frequency had a significantly negative relation to S. salsa total biomass, which consisted of above- and belowground biomass, and a significantly positive relation to height. In general, total organic carbon, total nitrogen, and total phosphorus differed among sites, and these differences changed with the soil layers. In addition, there were some correlations between the soil environment and plant traits. Total organic carbon was linearly positively linked to the biomass of S. salsa at each soil depth. The carbon, nitrogen, and phosphorus stoichiometry of the soil had a low correlation with that of the belowground biomass of S. salsa but had a significant correlation with that of the aboveground biomass of S. salsa. Our study suggests that spatial patterns of S. salsa and edaphic conditions in the YRD vary with tidal regime, therefore providing a basis for the context-dependent conservation and restoration of coastal saltmarsh ecosystems, especially in areas with irregular, semidiumal tides. Moreover, our findings highlight the importance of potential interactive effects between plant traits and tidal disturbances in regulating biogeochemical cycles, especially carbon sequestration, in coastal saltmarsh systems.
