Abstract: The ecological environment of arid inland river basins is extremely sensitive and delicate. Clarifying the relationships between different ecosystem services in inland river basins from various spatial scales can offer scientific references for ecological restoration and socio-economic sustainable development of river basins. Considering the Taolai River basin as an example, seven typical ecosystem services, including climate regulation services, biodiversity maintenance services, soil conservation services, water resource supply services, availability of aesthetic landscape services, wind prevention and sand fixation services, and food supply services during 2000-2018 were analyzed. The trade-offs and synergies between watershed ecosystem services were assessed from grid-scale, watershed scale, administrative area scale, and service cluster scale, and their spatial distribution characteristics were discussed. Spatial superposition method, superposition analysis method, and Pearson correlation coefficient method as well as self-organizing feature mapping (SOFM) neural network method were employed to assess the trade-offs and synergies between watershed ecosystem services from grid-scale, watershed scale, and administrative district scale, and service cluster scale. Furthermore, their spatial distribution characteristics were explored. The following are the conclusions of this study. (1) On grid-scale, the ecosystem services of most grid units in the research area switched from synergies to trade-off relationships from 2000 to 2018. (2) At the watershed scale, the relationships among the seven ecosystem services are primarily synergistic, whereas the relationship between soil conservation system service, and both the water resource supply service, and the wind prevention and sand fixation service are primarily trade-offs. (3) At the administrative district scale, the ecosystem services of the counties and districts primarily had various degrees of synergies. The highest synergistic relationship was found between climate regulation service and food supply service. (4) At the service cluster scale, the supply capacity of the seven ecosystem services had been substantially improved. The relationships among most of the ecosystem services in the cluster switched from trade-offs to synergies. This study can offer a scientific foundation for decision-makers to develop suitable ecological-economic coordinated development techniques at various spatial scales.

Key words: ecosystem service, trade-off and synergy, InVEST model, SOFM algorithm, Taolai River basin