[Spatio-temporal Evolution and Trade-off/Synergy Analysis of Ecosystem Services in Regions of Rapid Urbanization： A Case Study of the Lower Yellow River Region].

As the forefront of implementing China's "Yellow River Major National Strategy," the lower Yellow River area has caused irreversible "constructive destruction" to the regional natural ecosystem and ecological functions while accelerating the process of urbanization and has become an area of sharp contradiction between ecological protection and high-quality development of the river basin. Therefore, based on ArcGIS and MATLAB software, this study used the InVEST and RUSLE models to quantitatively assess water yield, habitat quality, and soil conservation services of the lower Yellow River Region from 1990 to 2020 and analyzed the spatial and temporal characteristics and their interaction relationships of various ecosystem services. The results showed that： ① In the period from 1990 to 2020, the land urbanization process accelerated significantly, with the expansion of construction land increasing by 39.89%, whereas the area of other major land types had declined to varying degrees. ② From 1990 to 2020, the distribution patterns on the county scale and grid-scale in the lower Yellow River Region were relatively consistent. The water yield and soil conservation experienced a changing trend of first decreasing and then increasing, and the spatial distribution pattern of water yield gradually shifted to more in the east and less in the west. The spatial distribution patterns of soil conservation and habitat quality remained unchanged throughout the period, with the high values distributed in the hilly or mountainous regions of the higher terrain and the low values mainly in the plains of the gentle terrain. ③ At both the grid scale and county scale, the interaction relationships between various ecosystem services had been dominated by synergy and showed significant spatial heterogeneity. Especially at the county level, strong trade-offs were occurring in a few counties. For example, the relationship between water yields and habitat quality was a significant and strong trade-off between Weishan County and Huaiyin District. The study quantified the spatial and temporal evolution characteristics of ecosystem services in the lower Yellow River Region and clarified the trade-off synergistic relationships between ecosystem services, which can provide a scientific basis for ecological protection and watershed management under the rapid urbanization process.