| This paper takes Xi’an,Shaanxi Province as the study area,and the selected study periods are 2000,2010 and 2020.In order to investigate its land use changes,this paper integrates two analysis methods of land use dynamic attitude and transfer matrix,and studies its land use landscape pattern by landscape index method;adopts remote sensing ecological index(RESI)to evaluate the ecological quality of land in Xi’an.On the basis of the ecological quality grading results,ecological source sites were obtained by screening patches with an area larger than 5 km2,and the ecological resistance surface was constructed by using the minimum cumulative resistance model;based on the circuit theory,the extraction of ecological elements was realized by the Linkage Mapper platform to form an ecological security pattern.Subsequently,the spatial and temporal changes of the ecological security pattern from 2000 to 2020 were analyzed.The main conclusions drawn in this paper are as follows:(1)The results of land use changes in Xi’an show that the largest area change between2000 and 2010 is construction land,whose new area reaches 46.40 km2,and the highest dynamic attitude is also construction land,with a dynamic attitude of 36.69%;between 2010 and 2020,the largest area change is arable land,whose reduced area reaches 206.95 km2,and the highest dynamic attitude is unused During the period of 2000-2020,the largest change in area was in arable land,with a decrease of 450.79km2,and the second largest change in construction land,with an increase of 442.94km2,During 2000-2020,the conversion of arable land,forest land and unused land and the conversion of grassland,water area and construction land in Xi’an mainly took place.During 2000-2020,the fragmentation of arable land and grassland in Xi’an increased,and the fragmentation of forest land,water area,construction land,and unused land decreased;the proportion of the largest patches of arable land and grassland in the overall landscape decreased,and the proportion of the largest patches of forest land,water area,and construction land in the overall landscape increased;the complexity of the surrounding shape of patches of water area and construction land increased,and the complexity of the surrounding shape of patches of arable land and grassland remained the same.The complexity of the surrounding shape of patches of water and construction land increases,the complexity of patches of arable land and grassland remains the same,and the complexity of unused land decreases.The patch density(PD),spreading index(CONTAG),and aggregation degree(AI)of the overall landscape have all decreased,indicating that the fragmentation of the Xi’an landscape has improved during this period;while the Shannon diversity index(SHDI)and Shannon evenness index(SHEI)have improved from 2000 to 2020,indicating that the aggregation degree of the overall landscape has increased and different types of patches are The area distribution is more uniform.(2)In this paper,four ecological indexes,namely,greenness index(NDVI),humidity index(WET),dryness index(NDSI)and surface temperature index(LST),were selected to construct and obtain the remote sensing ecological remote sensing index(RSEI)to evaluate the ecological quality of Xi’an city in three periods.The results of principal component analysis show that the RSEI index can well represent the information of these four indicators.Analysis of the RSEI grading results shows that: from the spatial and temporal distribution,the land area with very poor,poor and medium ecological quality grades in Xi’an City from2000 to 2020 has decreased,the land area with good ecological quality grades has increased,and the land area with very good grades The increase is larger.The ecological quality of the mountainous areas in the Qinling Mountains in the south has improved,while the ecological quality of the areas distributed north of the Qinling Mountains,such as Yanliang and Gaoling in the northeast and Weiyang District in the north-central,has all deteriorated.(3)Based on the ecological quality evaluation grade of land in Xi’an,ecological source sites were identified,and the number of ecological source sites in 2000,2010 and 2020 were22,35 and 12,respectively,with the areas of 1264.43 km2,1661.08 km2 and 3107.67 km2,respectively.The ecological resistance surface was established based on the minimum cumulative resistance model,and the ecological resistance values were graded.Analysis of the graded results showed that the area of areas with low ecological resistance changed less,while the area of areas with high ecological resistance gradually increased,which was closely related to the development of urban construction land.By extracting ecological elements through Linkage Mapper platform,the total number of ecological corridors extracted in 2000 was 43,with a total length of about 335.01 km,a total of 38 ecological pinch points,and a total area of 99.55km2 of ecological barrier areas;the total number of ecological corridors extracted in 2010 was 73,with a total length of about 704.22 km,a total of 45 ecological pinch points,and a total area of ecological barrier areas The total area of ecological barrier zone is217.31km2;in 2020,23 ecological corridors with a total length of 576.79 km and 35 ecological pinch points are extracted,and the total area of ecological barrier zone is reduced to136.31km2.(4)In view of the ecological safety pattern of land in Xi’an,relevant suggestions were made: to expand and improve the quality of ecological source lands;to strengthen the construction of urban greenways and river corridors;to pay attention to the management and improvement of ecological pinch points;to manage ecological safety obstacle areas;and to increase the government’s publicity and education on ecological protection. |
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