Exploring the driving factors of trade-offs and synergies among ecological functional zones based on ecosystem service bundles

In karst mountainous area, the strong spatial heterogeneity of the natural geography and the complexity of the human activities have led to significant variability and uncertainty in the process of ecosystem services (ESs). The trade-offs/synergies of ESs and its driving forces change with space significantly, which are not only related to the natural environment but also affected by socioeconomic factors. Clarifying the spatial distribution and compositional structure of the ecological functional zone and understanding the main driving factors of the trade-offs and synergies among multiple ESs are essential for scientific management and restoration of karst ecosystems. The objective of this study was to explore the driving forces of the trade-offs/synergies for each ecosystem service bundle (ESB) and to develop differentiated ecological management strategies based on the ecological characteristics. In this study, six ESs (i.e., water yield (WY), soil conservation (SC), net primary productivity (NPP), habitat quality (HQ), recreation services (RS), and food production (FP)) were quantified in the Wujiang Basin. Based on this, the spatial distribution and land use types of the coldspots/hotspots were analyzed. Then, the K-means algorithm was used to identify the ESBs. According to the ecological structural characteristics of the ESBs, the ecological functional zones were divided. Furthermore, the trade-offs/synergies and their driving factors among the ESs in each ESB were analyzed using Pearson correlation analysis and geographical detector. The results showed that the land use types significantly affected the spatial distribution of multiple ES coldspots/hotspots. The ES hotspots were mainly concentrated in the forest areas, while the coldspots were concentrated in the urban and farmland areas. Based on the spatial distributions and ecological features of the ESBs, the Wujiang Basin was divided into food supply area, habitat transition area, cultural recreation area, and ecological balance area. There were synergistic relationships between the SC and WY and between the SC and NPP in every functional zone. Precipitation and its interactions with other factors were the main driving forces that influenced the trade-off between the WY and FP in both the food supply area and the habitat transition area. The normalized difference vegetation index (NDVI) was the dominant factor that affected the spatial pattern of the trade-off between the FP and NPP in the cultural recreation area. This deeper understanding of the trade-offs/synergies in each functional zone provides a scientific basis for territorial spatial planning and ES optimization in the karst mountainous area.