Scaling effects of ecosystem service trade-off and synergy in arid inland river basins: A case study of the Manas River Basin of Xinjiang, China

• Explore the spatial differentiation patterns of trade-off/synergy relationships at multiple scales. • Identify the nonlinear dominant factors influencing trade-off/synergy relationships at different scales. • Visualize the nonlinear interactions between trade-off/synergy relationships and key drivers. • Find optimal values for specific scales and suggest ecological regulation measures. The study of trade-off and synergy relationships (TOS) among ecosystem services (ESs) and the scale effects of their driving mechanisms is an important breakthrough for the integrated promotion of synergistic ecosystem-environmental governance and regional sustainable development. In this paper, we used the InVEST model to quantitatively assess the four types of service functions and spatial patterns of water supply, soil conservation, habitat quality, and carbon storage in the Manas River Basin in 2022, explored the spatial differentiation patterns of TOS at different scales by spatial superposition method, and mined the mechanisms of the natural background and socioeconomics of the TOS at different scales using the random forest model. The main conclusions are as follows: (1) All four typical ESs in the Manas River Basin showed significant spatial heterogeneity. (2) There is a scale effect in the spatial evolution pattern of TOS, and 1 km × 1 km, 10 km × 10 km, and sub-watershed scales are the “inflection points” of TOS changes. (3) The response of TOS to natural and social factors varies at different scales. (4) The correlation between TOS and the driving factors is nonlinear, and the difference in the response of TOS to the influencing factors is more obvious at the sub-watershed scale than among the raster scales.