To analyze the spatial and temporal variation of the leading edge of Spartina alterniflora in Yancheng Wetland National Reserve, Jiangsu Province, an improved window of opportunity model based on Spartina alterniflora reproduction mode and minimum disturbance-free time of remote sensing inversion was proposed, and the evolution pattern of Spartina alterniflora leading edge and its driving mechanism were analyzed through the correlation analysis and mean absolute error to verify the accuracy of the model. The results showed that from 1998 to 2010, the front of Spartina alterniflora advanced to the sea. From 2010 to 2020, the foreedge presents a W-shape trend of siltation-erosion-siltation-erosion-siltation from north to south. In 2020 and 2021, the Spartina alterniflora front continued to erode and retreat in the north, remained relatively stable in the middle, and moved seaward in the south.

Based on MIKE 21 model and Holland typhoon wind field model, the wind field and pressure field during No. 1909 Typhoon Lekima and No. 0509 Typhoon Matsa are constructed, and the corresponding storm surge process is simulated. The results show that the increase of water near the typhoon center changes significantly and the storm surge in the northeast of Zhejiang Province is greater during the typhoon landing. Affected by the typhoon intensity, the high value area of storm surge during Typhoon Lekima is larger, and the maximum difference of storm surge during two typhoons in some sea areas is close to 1. 0 m. The large value of tidal Euler residual current is mainly distributed in the sea area within a depth of 100 m and a velocity of more than 20 cm/s. Meanwhile, the Euler residual circulation exists in the coastal sea areas of Jiangsu Province and the northeastern sea areas of Taiwan Province. The value of Stokes residual current in the offshore during Typhoon Lekima is generally lower than that during Typhoon Matsa. The Stokes residual current term plays a certain leading role in the short-term transport process of net material in the coastal shallow water areas such as the Yangtze River Estuary, Zhejiang Province and Fujian Province during the typhoon. The empirical mode decomposition (EMD) method and Hilbert transform are used to analyze the characteristics of storm tide level at typical stations. It is found that the IMF1 mode at stations is in good agreement with the astronomical tide level. The water depth and the maximum power spectral density of IMF3 mode show a high correlation, and with the increase of water depth, the maximum power spectral density of IMF3 mode gradually increases.

To investigate the spatial and temporal evolution of salt marsh vegetation in Jiangsu Yancheng Wetland Rare Bird National Nature Reserve, a phenological feature composite method was used to invert the area of four types of salt marsh vegetation (Spartina alterniflora, Phragmites australis, Suaeda salsa and Imperata cylindrica) in the core area of the Reserve from 1984-2021, and to analyze its spatial and temporal evolution and driving mechanism. The results showed that the total area of salt marsh vegetation in the core area increased from 11113.2 hm² to 16528.14 hm², with a compound annual growth rate of 1.11%, mainly due to the ability of Spartina alterniflora to preserve the beach and promote siltation. Spartina alterniflora and Phragmites australis, by occupying a large number of Suaeda salsa beach, Phragmites australis beach and light beach, the area increased by 4968.62 hm² and 8806.95 hm², with compound annual growth rates of 26.67% and 6.88%, respectively. The areas of Suaeda salsa and Imperata cylindrica decreased by 3494.25 hm² and 4867.38hm² respectively by the superimposed effects of natural factors such as ecological niche competition and artificial disturbances such as aquaculture bases, with a compound annual growth rate of -3.14% and -8.11%, resulting in the severe fragmentation of the suitable habitats.