Spatiotemporal Dynamics Of Land Use/Cover Change (LUCC) And Landscape Ecological Risk Assessment In The Qilian Mountains

Land use/cover change(LUCC)reflects the impact of multiple ecological process changes on landscape patterns.In recent years,human activities,especially land development,have significantly altered surface landscape patterns and brought about a series of ecological and environmental problems,ultimately leading to increased ecological risks.As the most important water conservation area and green barrier area in the arid and semi-arid zone of northwest China,the Qilian Mountains are important for maintaining the ecological balance of the Tibetan Plateau and securing the recharge of inland river runoff in the Hexi Corridor.However,local ecological damage in the Qilian Mountains is serious and the regional ecological risk is increasing due to the impact of rough exploitation of mineral resources,tourism development and overgrazing.Therefore,scientific landscape ecological risk assessment(LERA)in the Qilian Mountains helps to establish an early warning mechanism for its ecological security and achieve sustainable management of the regional ecosystem.This study uses a cellular automata-Markov chain(CA-Markov)model to predict LUCC in the Qilian Mountains region in 2026 and 2034 based on five periods of land use/cover data in 1980,1990,2000,2010,and 2018,and analyzes the spatiotemporal dynamics of LUCC from 1980 to 2034;constructs a LERA model to systematically analyze the spatial and temporal changes of landscape ecological risk(LER)in the region from 1980 to 2034,comprehensively describes its topographic gradient effect,and quantifies the influence of drivers on LER.This study can provide a new framework for the study of LER in the Qilian Mountains and may serve as a reference for the development of ecological risk mitigation strategies in other arid and semi-arid mountainous regions around the world.The results of LUCC show that grassland and unused land are the most dominant land use/cover categories in the Qilian Mountains from 1980 to 2018;the projected land use/cover patterns in 2026 and 2034 are largely consistent with those in 2018.The land use/cover in the Qilian Mountains has the most dramatic changes in area transfer from2000 to 2018 and the transfer occurred mainly among grassland,water and unused land;the transfer changes of grassland and unused land still dominate from 2018 to 2034,similar to the transfer characteristics from 1980 to 2018.During the study period,the landscape fragmentation and landscape separation of forest are higher than the rest of the land use/cover types,which is due to the fact that forest is mainly scattered in areas with higher elevation and steeper slope;water has the greatest degree of landscape loss and shows an increasing trend,mainly due to its large number of patches and small area,which is the most vulnerable to human disturbance and natural influence among the landscape components;the unused land has a larger area and the highest vulnerability,and the landscape loss is second only to water,with an overall increasing trend.During the forecast period,compared to 2018,all landscape pattern indices show a dramatic downward trend,except for landscape dominance,which remains stable.The results of LERA show that there is a slow decline in LER in the Qilian Mountains from 1980 to 2018,and it will continue to decline during the forecast period,showing an overall spatial pattern of low in the southeast and high in the northwest.There are significant positive spatial correlations and clustering of LER in the study area for both 1980-2018 and predicted scenarios,and the high-high and low-low clustering patterns are dominant,with spatial heterogeneity mainly influenced by natural factors(topography,precipitation,NDVI,drought index,potential evapotranspiration,temperature)and anthropogenic interference(HI).The study area was dominated by ecologically stable areas from 1980 to 2000 and 2010 to 2018;the area of ecologically improved and ecologically deteriorated areas expanded in the central and northwestern parts from 2000 to 2010 and 2018 to 2036,which was closely related to the transfer of unused land to grassland and water,and grassland to unused land.The level of landscape fragmentation,separation and vulnerability is higher in topographic flat areas and mid to high altitude areas,which are dominated by natural landscapes such as bare land and snow,with relatively fragile ecological conditions,making the area more likely to be at high ecological risk.Therefore,we should focus on zoning,make reasonable land use planning base local conditions,and establish a long-term regulatory mechanism in the process of regional ecological risk management.