Evolution of Ecosystem Service Trade-offs and Synergies in the Tuojiang River Basin Based on Ecosystem Service Bundles

It is important to maintain the stability and sustainability of river basin ecosystems, which requires an understanding of the dynamics of ecosystem services bundles and the trade-off/synergistic relationships within them. In this study, ecosystem services in the Tuojiang River Basin were modelled using InVEST software and a soil loss equation for the years 2010, 2015 and 2020. Ecosystem service bundles were identified through K-means clustering. The dynamic trade-off/synergistic relationships among major ecosystem services within bundles were measured. These relationships and the dynamics of service bundles are discussed. Some regional management approaches for different bundle types are proposed. We found that: (1) the spatial pattern of ecosystem services changed slightly and the changes in each service are different from 2010 to 2020. Specifically, the ecosystem services of habitat quality, water production and carbon sequestration increased, whereas total food production and soil conservation area decreased. High service values in carbon sequestration, soil conservation, and habitat quality were concentrated in the northern and north-central regions of the basin. High service values in water production were concentrated in middle and lower reaches of the basin and decreased from south to north. High service values in food production were mainly concentrated in the central-north and southern cultivated regions of the basin. High service values in culture and entertainment were established in urban areas and had inter-city networked connections. (2) According to clustering analysis, the river basin can be divided into five ecosystem service bundles that have spatiotemporal heterogeneity. A food production bundle accounted for 72.9% of the river basin area, which was dominated by food production activities and water production services. An ecological conservation bundle accounted for 15.2% of the area and was dominated by biodiversity and carbon sequestration services. The culture and entertainment bundle accounted for 6.9% of the area and was dominated by cultural and entertainment services. A multi-functional coupling bundle accounted for 4.4% of the area and was dominated by biodiversity, carbon sequestration, and water and soil conservation services. A water and soil conservation bundle accounted for 0.5% of the area and was dominated by water and soil conservation activities. (3) Within service bundle, there were more synergistic relationships than trade-off ones. However, across the whole river basin, there were more trade-off relationships than synergistic ones. The trade-off and synergistic relationships among ecosystem services had certain similarities and differences across different bundles. The relationships between certain service combinations had different intensities in different bundles. The results provide a reference for ecosystem management and optimization, ecological civilization, and sustainable development of the Tuojiang River Basin.