Abstract
To ensure the long-term stability of the valuable saltmarsh ecosystem, a comprehensive understanding of saltmarsh plant responses to strong tidal stress is essential. We investigated the effects of sedimentation dynamics and hydrodynamics on saltmarsh morphological traits and biomass allocation during growing seasons in the Yangtze Estuary. Our results showed that: (1) Individuals colonized at the seaward edge of saltmarsh were subjected to stronger hydrodynamic and sediment dynamic disturbance than those at the inner saltmarsh. Specifically, the average water depth, effective wave height, current velocity, bed shear stress and suspended sediment concentration at the low saltmarsh were 4.8, 9, 5.8, 4, 1.78 times higher than that at the inner saltmarsh, respectively. Thus, individuals at the seaward edge of saltmarsh were more resilient. (2) At early and middle growth stages, both aboveground and belowground plant traits showed significantly different growth patterns. (3) Lastly, the shoot/root rate differs significantly between seaward and landward edges, indicating that the optimal allocation of Scirpus mariqueter biomass was approached to cope with external stresses from waves and sediments. We concluded that this phenotypic plasticity of plant traits was a response to the heterogeneity of tidal flat sedimentation processes and increased plants tolerance to the changing environment. These findings may help in developing an appropriate saltmarsh rehabilitation strategy to address the stressors such as hydrodynamics and sedimentation dynamics.