Micro-Topography Manipulations Facilitate Suaeda Salsa Marsh Restoration along the Lateral Gradient of a Tidal Creek

Topographic heterogeneity provides a potential opportunity for seedling recruitment in the disturbance-dynamic ecosystem. Micro-topography manipulation is the typical way to imitate or recover the natural topographic heterogeneity for the degraded salt marsh restoration. However, it is still not clear how different micro-topographic structures work along the lateral gradient of a tidal creek. In this study, we performed three micro-topographic treatments, i.e., hollow topography, fine and coarse biotic grille structures, to restore the degraded Suaeda salsa wetlands. The results showed that the effectiveness of micro-topography restorations varied with structures and elevation levels. The hollow topography performed well in high marshes by relieving salinity stress and enhancing seeds retention. Moreover, in middle and low marshes, fine biotic grille structure improved the seeds retention and soil conditions better, including soil salinity and moisture, which were critical physico-chemical factors for Suaeda salsa biomass restoration according to redundancy analysis. In contrast, coarse biotic grille structure showed little significance on Suaeda salsa restoration. The findings of this work emphasized that seeds retention and post local soil conditions were significant aspects for salt marsh restoration. Meanwhile, it provided an alternative design for micro-topographic structures by native biotic materials in the complex and dynamic salt marshes.