Jianbu Wang, Zhaoyang Lin, Yuanqing Ma, Guangbo Ren, Zijun Xu, Xiukai Song, Yi Ma, Andong Wang, Yajie Zhao. Distribution and invasion of Spartina alterniflora within the Jiaozhou Bay monitored by remote sensing image[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1907-y
Citation:
Jianbu Wang, Zhaoyang Lin, Yuanqing Ma, Guangbo Ren, Zijun Xu, Xiukai Song, Yi Ma, Andong Wang, Yajie Zhao. Distribution and invasion of Spartina alterniflora within the Jiaozhou Bay monitored by remote sensing image[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1907-y
Jianbu Wang, Zhaoyang Lin, Yuanqing Ma, Guangbo Ren, Zijun Xu, Xiukai Song, Yi Ma, Andong Wang, Yajie Zhao. Distribution and invasion of Spartina alterniflora within the Jiaozhou Bay monitored by remote sensing image[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1907-y
Citation:
Jianbu Wang, Zhaoyang Lin, Yuanqing Ma, Guangbo Ren, Zijun Xu, Xiukai Song, Yi Ma, Andong Wang, Yajie Zhao. Distribution and invasion of Spartina alterniflora within the Jiaozhou Bay monitored by remote sensing image[J]. Acta Oceanologica Sinica. doi: 10.1007/s13131-021-1907-y
Laboratory of Marine Physics and Remote Sensing, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China
2.
School of Information and Electrics, Beijing Institute of Technology, Beijing 100081, China
3.
Shandong Marine Resources and Environment Research Institute, Shandong Provincial Key Laboratory of Restoration for Marine Ecology, Yantai 264006, China
4.
North China Sea Environmental Monitoring Center, State Oceanic Administration, Qindgao 266033, China
5.
Shandong Yellow River Delta National Nature Reserve Administration Committee, Dongying 257091, China
Funds:
The National Natural Science Foundation of China under contract Nos 42076189, 41206172 and 61601133; the Natural Science Foundation of Beijing under contract No. JQ20021; the Remote Sensing Monitoring Project of Geographical Elements in Shandong Yellow River Delta National Nature Reserve—the Remote Sensing Monitoring Technology Project of S. alterniflora in Shandong Province in 2020.
Spartinaalterniflora as an alien invasive plant, poses a serious threat to the ecological functions of the coastal wetland of the Jiaozhou Bay. As of 2019, the distribution area of S. alterniflora in the Jiaozhou Bay has reached more than 500 hm2. For this reason, combined with field surveys, remote sensing monitoring of the invasion S. alterniflora in the Jiaozhou Bay has been carried out. To accurately identify S. alterniflora within the Jiaozhou Bay coastal wetland, we used a new method which is an implement of deep convolutional neural network, and by which we got a higher accuracy than the traditional method. Based on distribution of S. alterniflora extracted by the proposed method, the temporal and spatial distribution characteristics of S. alterniflora were analyzed. And then combined with environmental factors, the invasion mechanism of S. alterniflora in the Jiaozhou Bay was analyzed in detail. From the monitoring results, it can be seen that S. alterniflora in Jiaozhou Bay is mainly distributed in the beaches near the Yang River Estuary and its southern side, the Dagu River Estuary and the Nvgukou. S. alterniflora first broke out near the Yang River Estuary and gradually spread to the tidal flats near the Nvgukou. The Dagu River Estuary is dominated by Spartina anglica, whose area has not changed much over the years, and a small amount of S. alterniflora has invaded later.
Figure 1. Study area in the Jiaozhou Bay, Shandong Peninsula, China. Area A is Nvgukou, including the Moshui River Estuary, Baisha River Estuary and tidal flat on the east side of Hongdao; Area B is the Dagu River Estuary; Area C is the Yang River Estuary; and Area D is the Lianwan River Estuary.
Figure 2. Field survey sites (a–b; green dots) and vegetation photographs (c–g). c. dense growth of Spartina alterniflora on the tidal flat; d. Spartina anglica mixed with S. alterniflora, which is mainly distributed in the Dagu River Estuary; e. densely distributed S. alterniflora blocking the river channel; f. S. alterniflora occupying the growing area of Phragmites australis; g. Suaeda salsa near S. alterniflora, mainly in the Yang River Estuary and the Moshui River Estuary.
Figure 3. Data preparation and experimental process.
Figure 4. Network structure of the deep convolutional neural network
Figure 5. Remote sensing monitoring results of Spartina alterniflora over time in the Jiaozhou Bay. a. S. alterniflora distribution in the Yang River Estuary and Dagu River Estuary in 2002, 2012, 2014 and 2019; b. S. alterniflora distribution in Nvgukou in 2013, 2015, 2017 and 2019; c. S. alterniflora distribution in the Lianwan River Estuary in 1988, 2013 and 2015 and 2019.
Figure 6. Bar chart of changes in the area of Spartina alterniflora in the Jiaozhou Bay, 1988–2019. The gray color shows intermittent monitoring before 2019. The blue color shows annual monitoring after 2012.
Figure 7. Bar chart of Spartina alterniflora area in different distribution areas in the Jiaozhou Bay. Green shows the area of S. alterniflora each year in the Yang River Estuary; black shows the area of S. alterniflora near Nvgukou; blue and red represent the area of S. alterniflora and S. anglica in the Dagu River Estuary and Lianwan River Estuary, respectively.
Figure 8. Spartina alterniflora distribution from the Gaofen-1 WFV image and field pictures near the western end of Jiaozhou Bay Bridge. The red features in the image are S. alterniflora. The site conditions of the beach at A and B are shown on the right.
Figure 9. Invasion process of S. alterniflora on the east tidal flat of Hongdao. a. the invasion of Spartina alterniflora through seed. The initial stage shows scattered S. alterniflora seedlings. b. S. alterniflora starts root propagation after the seed invasion and forms a large number of patches. The patches are almost circular and spaced apart from each other. c. S. alterniflora multiplies through seeds and roots to connect the patches and finally completes the occupation of the tidal flat.
Figure 10. Scattered Spartina anglica at the Dagu River Estuary and S. alterniflora invading in the S. anglica growing area. a. the Gaofen-1 WFV satellite image and the photographs of S. anglica invaded by S. alterniflora. b. a mixed area of S. anglica and S. alterniflora taken at the scene. The taller plants are S. alterniflora, the smaller plants are S. anglica.
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