## 1 Introduction
Among the many divisions, the Integrated Natural Zoning of China [37], the Ecogeographic Regional System of China [38], the Forest Zoning of China [39], and the Vegetation Zoning of China [40; 41] are more widely used. At the same time, studies on ecological zoning at different regional scales have sprung up [42; 43; 44; 45], including the ecological zoning of typical areas of the GGP [46], but the ecological function monitoring zoning of the GGP at the national scale has not been reported. The practice of forest ecology research shows that establishing forest ecosystem positioning observation and research stations and forming a forest ecological function monitoring network with reasonable layout, construction standards, monitoring norms, and coordination and efficiency are the most effective means to carry out forest ecological function monitoring [12]. Long-term ecosystem positioning observations have been carried out in many countries worldwide and gradually developed from individual ecological positioning stations to ecosystem positioning observation research networks. For instance, the United States Long-Term Ecological Research [47], the UK Environmental Change Network [48], the Canadian Ecological Monitoring and Assessment Network [49], etc., provide data support for the study of ecology, environmental science, global climate change and impacts, sustainable development, and other essential theories and practices. In the 1950s, China began to conduct long-term ecological positioning observation research. After decades of development, the Chinese Terrestrial Ecosystem Research Network (CTERN)and the Chinese Ecosystem Research Network (CERN) were formed, which integrated forests, wetlands, deserts, bamboo forests, and urban ecosystems [50]. However, the two are long-term positioning observation studies on the national forest ecosystem. Although they overlap with the ecological monitoring of the GGP, they are not a monitoring network of forest ecological function of the GGP with clear orientation. At present, although the monitoring of ecological benefits of the GGP has a good working basis, it is still facing some outstanding problems, especially the insufficient number of monitoring stations. The distribution is not reasonable enough and the monitoring level is uneven and not closely integrated with the project, which makes the scientific, systematic, and comprehensive monitoring and accurate assessment of ecological benefits of the GGP still a major problem. To fully grasp and evaluate the status and dynamic changes of ecological benefits of the GGP, meet the needs of national ecological civilization construction, respond to the needs of regional policies, the decision-making needs of the Party Central Committee, the State Council and the competent authorities, and consolidate the achievements of the GGP and its high-quality development, it is urgent to plan and construct a specific monitoring network for forest ecological functions of the GGP. Remote Sensing (RS), Geographic Information systems (GIS), and Global Positioning systems (GPS) form the \"3S\" technology, which is a comprehensive technology that has been flourishing in recent years [51]. It has powerful advantages in capturing, storing, querying, analyzing, and visualizing spatial data. It can obtain timely, accurate, and dynamic information on the status of resources and their changes, which is widely used in earth sciences [52; 53]. Among \"3S\" technologies, GIS spatial analysis technology is a suitable method for ecogeographic zoning and monitoring station layout, which is of great significance to realizing dynamic monitoring and management, rational planning, and layout of terrestrial ecosystems.