Study on the Urban Expansion of Typical Tibetan Plateau Valley Cities and Changes in Their Ecological Service Value: A Case Study of Xining, China

Abstract

The accelerated urbanization process drives urban spatial expansion, making it essential to clarify the driving factors of this expansion and the corresponding ecosystem service value (ESV) response for effective regional urban planning. We selected Xining City, a typical plateau valley city with a spatial layout constrained by mountainous and riverine topography, as our study area. We analyzed land changes in Xining City over the past 20 years using the land transfer matrix and the PLUS model, and predicted land use changes under different scenarios for 2030. By combining these analyses with the improved unit area equivalent factor method, we quantitatively assessed the drivers of urban expansion in the main urban area of Xining City from 2000 to 2030 and estimated the ESV. The results showed that: (1) Over the past two decades, Xining City has experienced notable urban expansion, particularly along the Huangshui River, Beichuan River, and Nanchuan River. The urban construction land is mainly converted from cropland and grassland, and the simulation results under different scenarios in the future of 2030 show that the area of cropland and grassland continues to decrease. (2) The spatial expansion of urban areas in Xining City is primarily influenced by topographical factors, with urban transportation planning exerting a secondary influence. Distinct levels of roads exhibit varying degrees of impact on the expansion of constructed areas, with tertiary roads demonstrating the most widespread and substantial influence. Conversely, factors such as population density, GDP, and proximity to government have lesser influence on urban expansion. (3) The ecosystem service value (ESV) of Xining City exhibits a general decline from 2000 to 2030, marked by a significant loss of arable land and grassland and substantial shifts in ESV. Simulated ESV outcomes under diverse scenarios for 2030 consistently underscore that, irrespective of policy orientations, urban expansion and development, despite guarantees for urban, cropland, and ecological preservation, inevitably engender diminishing ecosystem service functionalities.