Ecosystem service trade-offs and ecological functional zoning in the Shiyang River Basin of northwest China

Ecosystem services are fundamental to ecological stability in arid inland river basins, and understanding their dynamics is essential for effective management. This study quantified water provision, soil conservation and carbon storage in the Shiyang River Basin from 2000 to 2022 using multi-source datasets and spatial ecological models, and examined their spatial patterns, temporal trends and interaction structures. The results showed that all three services exhibited clear spatial gradients. Water yield reached its mean maximum of 115.51 mm in 2018, soil conservation peaked at 1.61 × 10⁴ t·km⁻² in 2022, and carbon storage attained up to 13,693.97 t·km⁻² in 2022 within the mountainous areas. In contrast, markedly lower values were observed in the central oasis belt and the downstream desert plain. Trend analysis indicated that water yield exhibited strong regional contrasts, increasing substantially in the mountain areas, where the maximum positive slope reached 20.89 mm·yr⁻¹, but declining in the central and northern oasis–agriculture belt, with minimum values falling to − 18.39 mm·yr⁻¹. Soil conservation showed a basin-wide rising tendency, accompanied by localized declines on steep upper-basin slopes where erosion dynamics intensified. Carbon storage remained comparatively stable, with only minor increases or decreases observed in scattered areas. Trade-off assessment indicated strong synergies between water yield and soil conservation, whereas interactions involving carbon storage were more spatially variable. Interaction intensity, measured by a divergence index, remained low in relatively undisturbed mountain landscapes and higher in human-modified regions. By integrating spatial patterns, temporal behavior and interaction metrics, the study delineated five ecological functional zones that reflect the dominant ecological roles within the Shiyang River Basin. This zoning framework provides a spatially explicit basis for differentiated ecological management and supports coordinated decision-making in arid inland river systems.