Unraveling the mechanism of 3D auxiliary structures in plant seedlings protection: Optimizing salt marsh restoration in coastal zone

Salt marshes ecosystems, located between the sea and land, provide various valuable ecosystem services and constitute a sustainable nature-based coastal protection. However, these vegetated ecosystems have suffered extensive loss  or severe degradation globally, primarily due to anthropogenic disturbances and climate change. This has led to a decline in ecosystem services and a reduction in ecological functions. To reverse this degradation, numerous efforts have been carried out worldwide to conserve and restore these coastal vegetated ecosystems, thereby providing nature-based solutions to mitigate climate change. Biodegradable 3D auxiliary structures have been widely implemented as a nature-based solution to facilitate the salt marsh plant establishment, enhance sedimentation process, and promote natural recovery process. However, the mechanisms by which 3D auxiliary structures protect saltmarsh seedlings remain underexplored, with limited targeted designs and comparative studies across various substrates. Here, we mimic key emergent traits that locally suppress physical stress by using biodegradable establishment structures. We then conduct a flume experiment designed to measure detailed hydrodynamic and sediment key parameters in order to study the mechanism of 3D auxiliary structures in plant seedlings protection. Our process-based analyses indicated that aboveground 3D structures protect seedlings by reducing flow velocities, thereby decreasing plant bending angles. Meanwhile, belowground 3D auxiliary structures stabilizes substrates by increasing incipient velocities and reducing erosion rates. This study highlight the importance of considering and facilitating bio-abiotic interactions in salt marsh restoration, as well as understanding the specific conditions at the restoration site. It not only enhance our understanding of salt marsh restoration mechanisms but also bridges a critical gap between ecological engineering and climate adaptation strategies.