## 4 Discussion  
### Effectiveness Analysis of Monitoring Station Layout  
In this study, the zoning index system of the GGP was constructed by comprehensively considering the factors such as temperature, moisture, topography, soil, vegetation, and ecological function, and the layout method of monitoring stations was put forward according to the factors such as vegetation restoration characteristics of GGP, the spatial distribution of established ecological stations, and location importance. Then, based on the ecological function monitoring zoning and monitoring station layout method of the GGP, the ecological monitoring system of the GGP was constructed using GIS spatial analysis technology.  
According to this layout system, the full coverage monitoring of the GGP can be realized. The monitoring stations of the GGP are in the areas with high intensity of the GGP, which highlights the close integration of layout and GGP. The layout number of monitoring stations in the ecological function monitoring area of GGP is consistent with the implementation scale of GGP. The layout monitoring stations in southeast China are the most (27), accounting for 27% of the total number of stations. The number of layout monitoring stations in North China ranked second (21), accounting for 21% of the total number of stations. This was followed by the Yunnan-Guizhou Plateau area (11), northeast area (10), southwest alpine canyon area (8), eastern Inner Mongolia forest grassland and grassland area (8), Mongolia-Xinjiang desert semi-desert area (7), South China area (4) and Qinghai-Tibet Plateau grassland meadow and cold desert area (3), accounting for 11%, 10%, 8%, 8%, 7%, 4%, and 3% of the total number of stations.  
Among the ecological function monitoring zoning of the GGP, the most layout monitoring stations were DV(a)18, FV(a)26, GII(c)28, BIII(c)6, BIII(b)6, CV(a)17, and AII(b)4, which are 9, 6, 5, 5, 5, 4, and 4, respectively. This is mainly due to the large area of these ecological function monitoring areas, involving multiple provinces, the implementation intensity of the GGP is high (large area), and the importance of ecological location is high (mostly in ecological fragile areas), so the site layout is more.  
In the layout of the ecological function monitoring station of the GGP, the construction standard of the level-1 station is the highest, and the monitoring ability is the strongest, which has a leading and radiation effect on the surrounding secondary stations. Therefore, from the level of the monitoring station, the number of the level-1 station should be less than that of the level-2 station, which only needs to meet the monitoring requirements of the basic indicators. From the analysis of the type of monitoring station, the number of professional monitoring stations should be higher than that of compatible monitoring stations in theory. In this layout, there are 38 level-1 stations, accounting for 38%, and 61 level-2 stations, accounting for 62%. There are 51 compatible monitoring stations, accounting for 51%, and 48 professional monitoring stations, accounting for 48%. The proportion of the two is close due to giving full play to the monitoring function of the existing ecological stations, maximizing resources, and saving funds. In addition, the proportion of types of NMEPREA, NEFA, NEBA, and NKEFA covered by monitoring is 66.7%, 100%, 100%, and 76%, respectively. Overall, the layout can meet the professional monitoring of the typical ecological areas.