| Land use change profoundly affects the structure and function of ecosystems.Located on the eastern edge of the Tibetan Plateau,the high plateau region of western Sichuan is a special and important ecological zone,and is an important ecological security barrier in the Yangtze and Yellow River basins.The ecological environment of the region is more fragile and sensitive,the economic level is also relatively backward,and the economic and social development has not yet fundamentally achieved a comprehensive green transformation.The combination of the natural environment and human activities has led to a growing conflict between socio-economic development and ecological protection in the region.In-depth exploration of the laws of land use change in the region and accounting for its ecological service value can steadily improve the quality and stability of the region’s ecosystem,build a firm ecological security barrier in the upper reaches of the Yangtze River and Yellow River,and realize a virtuous cycle of the ecosystem in which mountains,water,forests,fields,lakes,grasses,sand and ice are integrated.Therefore,this study takes the high mountain plateau region of Sichuan（Aba Tibetan and Qiang Autonomous Prefecture,Ganzi Tibetan Autonomous Prefecture,Liangshan Yi Autonomous Prefecture,and Panzhihua City）as the research object.Firstly,analyzing the spatial and temporal evolution characteristics of the current land use based on land use data and analyze the driving factors of land use change using Geodetector;secondly,simulating the land use change of natural development scenario and policy constraint scenario using Markov chain and FLUS model;then,using the modified ecological service value estimation model to explore the spatial and temporal variation characteristics of the current and future ecological service value.The main conclusions obtained from the study are as follows.（1）Land use structure and changes are relatively stable,with the level of economic development being the main driver.The area of forest and grassland accounts for about88.60% of the study area,and the area of unused land,cultivated land,water and building land all account for less than 10%.From 2000-2015,the area of grassland decreased the most（3411.97 km2）,the area of forest land increased the most（2873.20 km2）,and the area of building land changed the most,with an increase of 85.54%.Comprehensive land use dynamics show an increase followed by a decrease,with the dynamics of construction land being much higher than other land types.Conversion between forest land and grassland is the main type of land conversion.Socioeconomic factors have a greater influence on land use change in the study area.The dominant drivers differed among regions,and in general GDP,elevation and population density had stronger explanatory power.（2）The total value of ecological services in the study area increased by a net 13.858 billion yuan,and the quality of the ecological environment has generally developed for the better.Forestland and grassland contribute 88.40% to the ecological environment,while the remaining land types provide no more than 5% of the value of ecological service functions.The magnitude of the role of individual ecological service functions remained constant across time,with hydrological regulation > climate regulation > soil conservation > maintenance of biodiversity > gas regulation > purification of the environment > provision of aesthetic landscapes > production of raw materials > food production > water supply > maintenance of nutrient cycles.The overall ecological service value of the region is low,but the spatial differentiation is obvious and stable,basically showing a trend of high in the southeast and low in the northwest,with the worst ecosystem quality in Shiqu County and the best in Miyi County.During 15 years,30 counties in the region belonged to the type of ecological environment quality improvement,mainly concentrated in the plateau area and high mountain valley area in the northeast of the study area,among which Luding County had the highest change rate;12 counties belonged to the type of ecological environment quality degradation,mainly distributed in the plateau area,high mountain valley area and the western part of the mountain area,among which Derong County had the most decrease.（3）The policy-oriented scenario has optimized the layout of land use,and the quality of the ecological environment has been significantly improved.The policy scenario guarantees about 6,379.59km2 of high-quality cultivated land and 1,447.69km2 of ecologically important areas on top of the restrictions on land changes in nature reserves and national park areas.Significantly increased the area of forest and grassland,effectively controlling the potential trend of wild expansion of building land and driving the expansion of building land in a way that occupies lower quality cultivated land and a small amount of grassland.The quality of ecological environment has been greatly improved,the value of ecological services has increased by 281.399 billion yuan,and all ecological service functions are basically in a benig n development trend.The study of the impact of different land use scenarios on ecological service values in the high mountain plateau region of Sichuan can formulate scientific and reasonable land use development and ecological protection policies for adapting to the new development stage,which is conducive to exploring the realization path of regional nature conservation and coordinated socio-economic development and enhancing the ecological barrier function of the Tibetan plateau. |
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