5. Conclusions
The results from this study demonstrate that it is feasible to extract
native and invasive species in the Yellow River Delta region based on
phenological characteristics of vegetation and spectral features of
satellite remote sensing images. May and October are important periods
for extracting the P. australis community and the S.
alterniflora community, respectively, in the Yellow River Delta or in
the coastal wetlands in North China. The landscape characteristics and
spectral characteristics of the two communities are not much different
and are difficult to distinguish.
The accuracy of different vegetation community in this area can be
improved by taking into consideration both the vegetation phenology and
the spectral features of remote sensing images. The Sentinel-2 images
with red edge bands have obvious advantages in vegetation community
extraction as compared to Landsat-8 images. The P. australiscommunity in the study area is the dominant species, and its multi-year
landscape index is stable. The spatial distribution of S. salsais discrete, the degree of aggregation is low, and the area is
decreasing. The landscape index of the S. alterniflora community
showed a trend of increasing year by year, but the degree of
fragmentation decreased, indicating that the expansion pattern of theS. alterniflora community became spatially continuous, more
regularized and aggregated overtime.
The findings from this study advanced understanding of the spatial
distribution and spatiotemporal variation characteristics of native and
invasive plant species, and the expansion mechanism of S.
alterniflora and other species in the study area, and provide a basis
for making scientifically sound decision for management and the controlS. alterniflora invasion. It will contribute to the ecological
restoration and the protection of species diversity of the entire Yellow
River Delta in China. In addition, the research findings have important
theoretical and scientific value for the ecological environment
protection and sustainable development of the worldwide estuary wetland
ecosystem.