ECOSYSTEM SERVICES SUPPLY–DEMAND DYNAMICS AND MULTIDIMENSIONAL RELATIONSHIPS IN THE SHIYANG RIVER BASIN

Arid inland river basins are highly sensitive to climate change and anthropogenic disturbances, and persistent imbalances between the supply and demand of ecosystem services have become a critical constraint on regional sustainable development. Taking the Shiyang River Basin, a typical arid inland river basin in northwestern China, as the study area, this research selected four categories of ecosystem services—food provision, water yield, carbon storage, and windbreak and sand fixation. Using a parameter-calibrated InVEST model and GIS-based spatial analysis, we quantified ecosystem services supply and demand from 2000 to 2020, and evaluated supply–demand relationships across three dimensions: quantity matching, spatial matching, and trade-off/synergy assessment. The results show that: (1) From 2000 to 2020, the average supply of food provision and water yield exhibited an increasing trend, whereas carbon storage and windbreak and sand fixation showed fluctuating changes. High food supply was mainly concentrated in oasis areas, while the supply of water yield, carbon storage, and windbreak and sand fixation decreased from the southwest to the northeast; (2) During 2000–2020, the average demand for food provision and carbon storage continued to increase, while the average demand for water yield and windbreak and sand fixation gradually declined. High-demand areas for food provision, water yield, and carbon storage were primarily located in the main urban areas of the oasis, whereas demand for windbreak and sand fixation was mainly distributed in oasis–desert transition zones and desert regions; (3) In terms of quantity matching, food provision and carbon storage were predominantly surplus-oriented, water yield exhibited comparable proportions of surplus and deficit areas, and windbreak and sand fixation were dominated by deficit conditions. For all ecosystem services, low-low spatial matching and synergistic relationships were dominant, with synergy zones accounting for more than 50% of the basin.