| Land is the basic element and important carrier of human survival and social and economic development.With the rapid advancement of industrialization and urbanization,a series of problems caused by land use transformation,such as imbalance of land function structure,deterioration of ecological environment and sharp decline of resources,have seriously affected the sustainability of ecological environment and the high-quality development of human society,and have become the core of global change research.Jiuquan City is located in the western end of the Hexi Corridor in Gansu Province.It is an important part of the Hexi Oasis.It is also a carrier for the poor population in the arid and semi-arid regions of Northwest China to achieve poverty alleviation and ecological migration.Therefore,it is of great theoretical and practical significance to analyze and discuss the characteristics of land use function transformation and its ecological effects in Jiuquan City to improve the quality of oasis ecological environment,promote the sustainable development of regional land use and the green development and construction of ecological civilization.In this paper,the remote sensing images of land use in Jiuquan City in 1985,1991,1997,2003,2009,2015 and 2021 were used as data sources.Based on the classification system of"production-living-ecological"land use,the land was divided into living,ecological and production land.The dynamic changes of dominant transformation and recessive transformation of“production-living-ecological”land use in Jiuquan City were analyzed by using land use dynamic degree,transfer matrix and recessive morphological index.The ecosystem service value(ESV),value profit and loss index,landscape ecological risk index and elasticity coefficient were used to quantitatively analyze the ecological effects of“production-living-ecological”land transformation.The main conclusions are as follows:(1)From 1985 to 2021,the land use structure of“production-living-ecological”land use in Jiuquan City is mainly ecological land,accounting for 97.68%of the total land area,2.18%of the production land,and the living land is the least,accounting for only 0.14%.The single dynamic degree showed that the expansion rate of living land was the fastest(86.72%),followed by ecological land(10.23%)and production land(3.86%).The transformation of“production-living-ecological”land use has obvious stage characteristics.Taking 2003 as the boundary,the previous period is mainly the mutual conversion between production and ecological land,and there is mutual transfer between land types in the latter period.(2)In 1985,1991,1997,2003,2009,2015 and 2021,the recessive morphological index values of“production-living-ecological”land use in Jiuquan City were0.1,0.15,0.22,0.24,0.39,0.67 and 0.83,respectively,showing a significant upward trend,and the utilization efficiency of“production-living-ecological”land use was continuously improved.In the past 37 years,the change rate of the recessive morphological index of“production-living-ecological”land use is between 292.17%and 665.81%,and the change rate of different districts/counties is different.Among them,Dunhuang City has the largest change rate and Yumen City has the smallest change rate.(3)In the past 37 years,the total ecosystem service value of Jiuquan City has increased by 409.95×10~8 yuan.Among them,the ESV of ecological land increased by417.17×10~8 yuan,which was the main body of ESV in Jiuquan City.The ESV of production land increased by only 10.67×10~8yuan,while the ESV of living land decreased by 17.89×10~8 yuan,with obvious negative effects.The spatial distribution of ESV in Jiuquan City is roughly characterized by“high in the south and low in the north”.The high-value areas are mainly distributed in Subei Mongolian Autonomous County and Aksay Kazak Autonomous County in the south of the study area,and the low-value areas are mainly distributed in the middle and north of the study area.From the perspective of grade change,from 1985 to 2021,the area with unchanged ESV grade accounted for 66.58%,the rising area accounted for 19.51%,and the falling area accounted for 13.91%.The transformation of production-living-ecological land leads to the overall increase of ESV flow in Jiuquan City.Among them,the conversion of unused land,production land and living land to grassland,forest land and water ecological land causes the increase of ESV flow,and vice versa.(4)In the past 37 years,the spatial pattern of ecological risk in Jiuquan City showed the distribution characteristics of’high in southwest and low in northeast’.The high-value areas were mainly distributed in Dunhuang City,Aksay Kazak Autonomous County and Subei Mongolian Autonomous County in the south,and the low-value areas were distributed in Subei Mongolian Autonomous County,Yumen City,Guazhou County and Jinta County in the north.The overall ecological risk is mainly medium.Ecological risk transfer has obvious stage characteristics.The three periods of 1985-1991,1997-2003 and 2009-2015 are dominated by low-level to high-level ecological risk transfer,while the three periods of 1991-1997,2003-2009 and 2015-2021 are opposite.There is a significant negative correlation between ecological risk and“production-living-ecological”land use transformation,indicating that“production-living-ecological”land use transformation is conducive to reducing its ecological risk. |
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