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Zhaoning Gong

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The native and invasive species in the Yellow River Delta were examined for their spatiotemporal characteristics and succession pattern. First, the appropriate Sentinel-2 and Landsat-8 images from 2018 were selected according to phenological characteristics. A random forest algorithm was used to verify the image spectral band significance and separability using selected images to determine the native and invasive species. Then, the spatiotemporal variation of habitat structure of native and invasive species is discussed in depth from the perspective of landscape ecology. Finally, the expansion direction and expansion mode of S. alterniflora were further analyzed, and main results were obtained as follows. (1) At the medium-high resolution multi-spectral image level, the accuracy of different vegetation community extractions can be improved by taking into consideration both the vegetation phenology and the spectral features of remote sensing images. (2) Sentinel-2 images with red edge bands have obvious advantages in vegetation community extraction as compared to Landsat-8 images (Sentinel-2, OA=82.86%, Kappa coefficient=0.79; Landsat-8, OA=78.77%, Kappa coefficient=0.74). (3) The expansion pattern of the S. alterniflora community became spatially continuous, more regularized and aggregated overtime. (4) The expansion in the north shore mainly faces to the sea, and the south bank mainly faces to the land, and this phenomena is closely related to the sedimentation of the Yellow River Delta. Marginal and external expansion both occurred, but marginal expansion predominated. The results from this study have important theoretical and scientific value for the environmental protection and sustainable development of the entire Yellow River Delta.