Coastal wetland restoration based on hydrogeomorphic space units ——Taking the coastal wetland of Yancheng, Jiangsu as an example

As an important indicator of wetland hydrology, hydrogeomorphic conditions clearly indicate the coupling relationships between hydrology, landscape, and habitat. Aiming at problems of small-scale recovery and lack of systematic guidance in current coastal wetland restoration research, this study put forward a coastal wetland restoration system based on the hydrogeomorphic spatial unit. The spatial units of the hydrogeomorphic model were defined according to the regional background in Yancheng coastal wetland, and the changes in land cover patterns from 1980 to 2019 were analyzed. Then, based on the importance and potential for restoration, the key restoration areas were determined and then the dynamics change characteristic of S. salsa salt marsh boundary at the natural state was summarized. It showed that the ecosystem function in the region was basically stable from 1980 to 1998, and the boundary of the S. salsa salt marsh in each key restoration area showed dynamic stability or expansion to the sea. By 2019, with the construction of reclamation and coastal engineering, the hydrogeomorphic conditions in the region changed significantly. In addition to the continuous expansion of S. alterniflora marshes, other natural wetland types almost disappeared and transformed into aquaculture ponds or farmland. Based on those above, the study discusses the overall restoration modes of different hydrogeomorphic spatial units from two aspects of active restoration and passive restoration and puts forward systematic restoration measures in combination with the current characteristics of key restoration areas, forming a technical framework for coastal wetland restoration with practical guiding significance.