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.