Research on Land Use Pattern and Ecological Risk of Lanzhou-Xining Urban Agglomeration from the Perspective of Terrain Gradient

At the intersection of the Qinghai-Tibet Plateau and Loess Plateau, topographic factors often profoundly affect the evolution of the regional land use pattern and ecological risk. This paper takes the Lanzhou-Xining urban agglomeration as the research area, divides the topographic gradient based on the topographic index, analyzes the characteristics of the land use pattern using the land use transfer matrix model, dynamic attitude and state degree model, and analyzes the influence of topographic factors on the land use pattern using the distribution model. At the same time, an ecological risk evaluation index system is constructed, the spatial principal component method is used to evaluate the ecological risk, and the influence of topography on the regional ecological risk is discussed. The results show that from 1990 to 2020, the area of construction land in the study area increased by 1045.807 km(2) and the area of ecological land increased by 587.41 km(2), with the most significant changes occurring in the attitude and state of construction land and unused land. It is found that cultivated land, water area and construction land are dominant in low terrain, while woodland, grassland and unused land are mainly distributed in middle and high terrain. During the study period, the ecological risk in the midwest and southeast of the Lanzhou-Xining urban agglomeration decreased, while the ecological risk in the northeast increased first and then decreased, although generally there was an increasing trend. Moran's I varied from 0.942 to 0.955 from 1990 to 2020, indicating that the ecological risk index in the study area was highly positively correlated in space, while the spatial aggregation effect of the ecological risk was obvious. Low and moderately low risk areas are mainly distributed in high terrain, while high and moderately high risk areas are dominant in low terrain. The research results of this paper can make a lot of sense for ecological protection, land resource utilization and sustainable development of the Lanzhou-Xining urban agglomeration.