Supporting Information

1.Characteristics of invasive species

The spatial and temporal distribution of wetland vegetation communities are affected by various factors, such as climate, hydrology, soil, topography, and the biological characteristics of vegetation itself. The distribution and growth situation of typical dominant communities in the Yellow River Delta wetland are as follows:
S. salsa (Fig. 1d) is a poly-salt and annual herbaceous plant with a flowering and fruiting period from July to October, and the entire plant turns red in summer and autumn. Because of its bubbles used for storing salt, it has strong salt tolerance and is the main coastal halophyte that is distributed in beach areas, without associated species. The height of the plant is in the range of 15–80 cm. Due to the influence of soil salinity and groundwater depth, the vegetation coverage of the community is significantly different.
P. australis (Fig. 1e) is a perennial herbaceous plant that is mainly propagated by rhizomes. In early and mid-April, P. australis sprouts from underground rhizomes, with intense growth from April–July. The flowering and fruiting period is from August to September, and then the plant becomes dry and withered in October. The ecological range of P. australis is extremely wide, being distributed in the inland fresh water, coastal salt water, and brackish water interaction areas of the Yellow River Delta. With more than 50% coverage, the height of P. australis ranges from 0.5 to 3.0 m, with some plants exceeding 4 m.
S. alterniflora (Fig. 1f) is a perennial herbaceous plant that is salt-tolerant and resistant to wind and waves, is mainly distributed in the intertidal zone. The seeds can spread with the wind and waves. The roots are developed and often densely distributed in the soil layer to a depth of 30 cm. One plant can reproduce and yield dozens or even hundreds of plants within one year. The growth period of S. alterniflora is related to its geographical distribution. The jointing period of S. alterniflora in the study area is in early May, and the flowering period is from mid-August to early September. The seeds mature in mid- to late October, with the plant then entering the late growth stage and finally dying in November. With the height generally between 0.6–2.0 m and more than 90% coverage, the community composition of S. alterniflora is extremely simple, and it is an important invasive species in the Yellow River Delta Nature Reserve (Shi et al. 2009).

2.Data introduction

The Landsat-8 data and Sentinel-2 data used in this study were downloaded from the US Geological Survey official website (https://glovis.usgs.gov/) and the European Space Agency data sharing website (https://scihub.copernicus.eu/), respectively. The Landsat-8 image consisted of 8 bands at 30 m spatial resolution (Fig.S1). The area under study was covered by a single Landsat-8 image with path and row of 121/34. Atmospheric correction was performed for the Landsat-8 OLI image using the Fast Line-of-sight Atmospheric Analysis of Spectral Hypercube (FLAASH) model and Environment for Visualizing Images (ENVI) software (Shoko et al. 2017). The Sentinel-2 mission carries a multispectral instrument (MSI) with 13 spectral bands spanning from the visible spectrum (VIS) and near-infrared (NIR) to shortwave infrared (SWIR) at spatial resolutions of 10, 20, and 60 m (Yang et al. 2017; Yang et al. 2018) (Fig. 2). The Sentinel-2 dataset we downloaded was the standard product of the top of atmosphere (TOA) reflectance. Therefore, the atmospheric correction was preprocessed by the Sen2Cor model, which was utilized to transfer the TOA reflectance values to the bottom of atmosphere (BOA) reflectance values in the official software Sentinel Application Platform (SNAP) (Erinjery et al. 2018). After atmospheric correction, 20-m resolution bands, including bands 2-7, 8A, 11, and 12, were adopted for later extraction of native and invasive species.