| 摘要: |
| 以西沙群岛海域赵述岛礁坪为研究区域，应用2010年的WorldView-2和2015年的GF-2两期高分辨率卫星遥感影像数据，结合现场水下珊瑚礁照片和视频资料，建立了赵述岛礁坪底质类型遥感分类体系，分别构建了针对WorldView-2遥感影像和GF-2遥感影像的珊瑚礁底质分类决策树模型，并通过对两期遥感影像的底质类型提取结果的变化分析，完成了赵述岛礁坪退化区域的提取。结果表明：（1） WorldView-2影像的分类决策树具有91%的总体分类精度和0.89的Kappa系数，GF-2影像的分类决策树具有更高的分类精度；（2）6年期间研究区大约1/4的珊瑚礁分布区发生了退化；（3）最突出的自然变化是礁前区大面积的珊瑚丛生区转变成藻脊，结合相关资料认为东北季风、热带气旋和温度上升的综合影响是驱动因素；（4）赵述岛西侧的藻脊、珊瑚沉积区大面积转化为珊瑚砂和深水区域，原因是航道和码头的开发活动。研究分析了6年间赵述岛礁坪底质的退化状况，并分析原因，为珊瑚礁底质分类提供方法，并为西沙群岛的珊瑚礁监测和保护提供了有效资料和手段。 |
| 关键词: 珊瑚礁|遥感|决策树|退化 |
| DOI：10.11759/hykx20190103001 |
| 分类号:TP79 |
| 基金项目:国家重点研发计划项目（2017YFC1405600）；国家自然科学基金（51839002）；高分海岸带遥感监测与应用示范 |
|
| Study on substrate changes of Zhaoshu reef flat based on WorldView-2 and GF-2 remote sensing images |
|
WAN Jia-xin1,2, REN Guang-bo2, MA Yi2
|
|
1.School of Geosciences, China University of Petroleum, Qingdao 266580, China;2.First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China
|
| Abstract: |
| Coral reefs are one of the most biologically diverse ecosystems in the ocean with primary productivity. Under the dual pressures of natural and human factors, coral reefs are facing a huge risk of disease and degradation. In this paper, the Zhaoshu Island coral reef flat in the Xisha Island waters was considered as the research area. Based on high-resolution WorldView-2 and GF-2 satellite remote sensing image data obtained in 2010 and 2015 combined with underwater coral reef photographs and video data, a remote sensing classification system for the Zhaoshu Island reef flat substrate types was established. The decision-tree model of coral reef substrate classification based on WorldView-2 and GF-2 remote sensing image was established. The change of coral reef substrate type at the Zhaoshu Island was analyzed using a two-stage change detection method, and the degradation region was analyzed. The results show that (1) the decision tree of the WorldView-2 image has 91% overall classification accuracy with 0.89 Kappa coefficient and that of the GF-2 image has higher classification accuracy; (2) about 25% of the coral reef distribution area under study has been degraded during the six-year period; (3) the most prominent natural change is observed in the large area of reef-clumping to algal ridge in front of the reef flat. The combined relevant data indicates that the driving factors are the effects of the northeast monsoon, tropical cyclones, and temperature rise; (4) algal ridge and reef-deposition area on the west side of the Zhaoshu Island have been transformed into large coral sand and deep-water areas due to the development of waterways and wharfs. The study analyzed the reasons for the degradation of the reef substrates at the Zhaoshu Island over the past six years to provide methods for the classification of coral reefs and effective information and means for the monitoring and protection of coral reefs in the Xisha Islands. |
| Key words: coral reef remote sensing decision tree degradation |
