Abstract: Landscape connectivity determines the smoothness of species migration and material flow among patches. Urban landscape connectivity is of great significance for the ecological health and stability of high-density artificial constructions. Currently, viaducts are widely used to construct high-speed rail in China in order to reduce the negative impact on ecology and land as well as meet the requirements of engineering construction. However, the high-speed railway corridor still affects the landscape connectivity and ecological pattern of the traversing area to different degrees due to multiple factors, including damage during the construction, vibration and interference after operation, and bridge shadow space. Further, it produces a large negative space with a single habitat, which is difficult to be used and optimised comprehensively. The targeted ecological value optimisation and promotion of key ecological spatial nodes under the viaducts contribute to improved urban landscape connectivity and optimised urban ecology.
　　Based on the characteristics of high-speed railway viaducts, a spatial model based on key ecological nodes under the high-speed railway viaducts in built-up area in Chengdu City was constructed using ecological network analysis in key steps, including landscape types and ecological sources, screening of important potential corridors, and different layers. Based on morphological spatial pattern, the key ecological nodes in the space under the high-speed railway viaducts, such as patch type, corridor type and edge type, were identified. The corresponding strategies for optimisation for each type were proposed.
　　Based on analysis, 17 ecological sources, 63 important potential corridors, and 73 general corridors were identified in the built-up areas of Chengdu. The proportion of construction land in the corridor was minor, while the ecological land accounted for nearly 90%. A total of 91 key ecological nodes were identified in the space under high-speed railway viaducts in built-up areas of Chengdu, including 38 patches, 35 corridors, and 18 edges. The number of patches was the largest, representing basic sites of local ecological stability and improved quality of overall spatial habitat under the high-speed railway viaducts. A relatively large number of corridors, representing the key sites for improvement of regional landscape connectivity and decreasing the risk of species migration across the high-speed railway, were found. Besides, several key ecological nodes were concentrated on the Chengmianle Intercity Railway Corridor, Chengdu-Chongqing High-speed Railway Corridor, and the East Ring Road Corridor of the Sanhuan Railway. Among them, 23 key ecological nodes under Chengmianle Intercity Railway Corridor, accounting for 25% of all ecological nodes. They include prominent high-speed railway corridors for ecological optimisation and design. The intersecting hub areas of several high-speed railway corridors represent concentrated distribution of key ecological nodes. The combinations and spatial relationships are diverse and complex, thereby hindering habitat construction. The basic and key ecological nodes for improvement of regional connectivity require attention for improved ecological function. Corresponding optimisation strategies, such as habitat improvement, corridor improvement, interference relieving, urban reaction, are needed based on established spatial ecological nodes and characteristics under the high-speed railway viaducts.
　　The methodology can be widely utilised to identify key ecological nodes in the space under railways, highways and other traffic corridors. The findings provide a standard of reference to improve the ecological value of space under urban traffic viaducts for urban safety.

Key words: high-speed railway corridor, space under bridges, ecological network, ecological node identification, landscape connectivity

摘要： 针对高铁廊道桥下空间关键节点进行生态价值优化与提升，有助于提高城市景观连通性、优化城市生态格局。以成都市建成区高铁廊道为例，基于生态网络分析方法，通过识别景观类型与生态源地、筛选重要潜在廊道、分层叠置分析等关键步骤，构建高铁廊道桥下空间关键生态节点识别模型。最终识别出高铁廊道桥下空间关键生态节点共计91个，包括斑块类38个、廊道类35个、边缘类18个，并根据生态节点类型及特征，从提升生境质量、改善连通性等方面提出优化策略。研究结果可为城市交通廊道桥下空间生态价值提升及城市生态安全建设提供参考。

关键词: 高铁廊道, 桥下空间, 生态网络, 生态节点识别, 景观连通性