Spatial-Temporal Evolution Characteristics and Mechanism Analysis of Urban Space in China's Three-River-Source Region: A Land Classification Governance Framework Based on "Three Zone Space"

In China's new era with a territorial spatial governance framework, the delineation of the "Three Zones and Three Lines" is a crucial step in establishing a comprehensive and vertically integrated spatial control system. The changes in the "Three Zone Space," including ecological space, production space and living space, derived from land use abstractions, reflect the extent and manner of the impact of human activities. It serves as an important link between the macroscale (main functional zones) and the microscale (land use planning). The Three-River-Source Region is an important ecological security barrier and a demonstration area for ecological civilization in China. It is also considered one of the least suitable areas for human habitation in China. This region encompasses extensive protected natural areas, and human settlement space is scarce and valuable. The urban space, as an important spatial component of human habitation, often gives rise to significant conflicts between human activities and the environment during the implementation of development and conservation policies for remote areas in China. However, there is currently insufficient attention given to the human settlement space in this area. Therefore, it is necessary to study the evolution and driving mechanisms of urban spatial development from the perspective of the holistic and systematic nature of the "Three Zone Space". To achieve this, the article first analyzes the characteristics of urban spatial changes from 1992 to 2020. Then, it utilizes the optimized parameter Geodetector to analyze the driving mechanisms behind these changes. The results show that: (1) urban spatial expansion has continued to grow over the past 30 years, with an increase of 774.56%; (2) agricultural space is the main source of conversion for urban spatial expansion; (3) natural factors have limited influence on urban spatial expansion, while human factors play a significant role with evident spatiotemporal heterogeneity. This study is significant for the governance and protection of river sources, the conservation of ecosystems in ecologically fragile areas, and the sustainable development of cities. It can also provide scientific references for decision-making in ecological environmental protection and the formulation of land use and spatial planning at various levels in pastoral areas.