Spatio-temporal variations and trade-offs/synergies of typical ecosystem services in Ordos City.

Ordos City is located within the Yellow River 'Ji Zi Bend'. Clarifying the spatio-temporal variations and trade-offs/synergies of ecosystem services is of great significance for ecological protection and high-quality development of the Yellow River Basin. Based on the InVEST model and remote sensing data, we evaluated the ecosystem services of soil conservation, carbon storage, water conservation, and net primary productivity (NPP) in Ordos City from 2000 to 2020, and analyzed their spatio-temporal variations. We used correlation analysis to explore the trade-offs/synergies relationship among the four ecosystem services, and further revealed the trade-off/synergy intensity and its driving factors by combing the trade-off/synergy index and random forest model. The results showed that the typical ecosystem services in Ordos City showed an overall upward trend from 2000 to 2020. Total soil conservation increased by 3.47×10 t. Carbon storage increased by 0.28×10 t. Water conservation increased by 0.76×10 m. The annual average NPP increased by 349.54 g C·m. Among all the land use types, grassland and cultivated land had the greatest positive effect on the improvement of regional ecosystem services. Except for the uncorrelated relationships between carbon storage and soil conservation and NPP, the relationships among other ecosystem ser-vices were significantly synergistic. There were trade-offs between soil conservation, NPP, and water conservation in some areas. The main factors driving the intensity of trade-offs/synergies among ecosystem services in Ordos City were rainfall, temperature, slope, and population density. In general, the four typical ecosystem services in Ordos City showed favorable development trends. Based on the spatio-temporal heterogeneity of ecosystem services and the driving factors of tradeoff/synergy intensity, more appropriate strategies for continuous improvement of ecosystem services should be formulated in the future.