Abstract: We used land use data of the main urban area of Lanzhou, a city developed in the river valley, in 1995, 2005, and 2015 to analyze the spatial and temporal characteristics of construction land expansion. The CLUE-S model and Markov model were integrated to simulate the growth and spatial distribution of construction land under three different scenarios in 2025. The landscape ecological pattern characteristics were analyzed through landscape principles. The results showed that, from 1995 to 2015, the expansion of construction land was mainly based on the internal filling of urban groups and supplemented by external expansion, and the expansion was significantly affected by the terrain and policies. During 2015 and 2025, the growth rate of construction land under three scenarios in a descent order would be baseline scenario, comprehensive development scenario, ecoconservation scenario. The expansion area mainly includes the north of the Yellow River in Chengguan District, the north of Anning District urban area, and the southern edge of Qilihe District urban area. Because of the intensive expansion of the construction land, the unstable landscape pattern with the simple landscape patch shape and enhanced vulnerability is formed under the baseline scenario and comprehensive development scenario, while the landscape pattern with reasonable patch components, and rich diversity and uniform distribution is formed under the ecoprotection scenario in which the expansion speed of construction land is effectively controlled.

Key words: freeze-thaw cycle, aggregates stability, black soil, Le Bissonnais method, aggregate porosity