Results/Conclusions: Our field experiments showed that high hydrodynamic disturbance intensity (i.e., HDI) of the margin of main tidal channels (i.e., MMC) wasn’t beneficial to cordgrass invasion, whereas, low HDI created windows of opportunity for cordgrass invasion to the margin of secondary anabranches (i.e. MSA) by facilitating the survival, growth, and stability of cordgrass seedlings. The presence of high HDI predominantly reduced the survival and total biomass of cordgrass, whereas root biomass allocation of cordgrass was increased significantly to resist dislodgment and toppling. Moreover, field investigations showed that soil salinity and moisture in the margin of tidal channels were not the limited factors affecting the seedling establishment of cordgrass. However, higher propagule pressure combined with suitable salinity-moisture conditions of soil (i.e., low salinity and high moisture) laid a firm foundation for favoring the seedling establishment. These findings comprehensively reveal the vital mechanisms of cordgrass invasion to the tidal channel margins. Our results highlight the importance of hydrodynamic disturbance as a dominated driver regulating seedling establishment of cordgrass in the margins of tidal channels, and potential implications to control cordgrass invasion.
