| Since the idea of ecological civilization construction was put forward,the state has taken a series of ecological protection measures in order to maintain the ecological security pattern and realize the sustainable development of the ecology,such as desertification prevention and control,returning farmland to forest and grassland,building ecological shelter forest and so on,which have achieved certain stage results.As an important urban agglomeration in northwest China,Lanxi urban agglomeration is facing increasingly serious regional ecological environment problems due to its fragile background ecological environment.The Development Plan of Lanzhou-Xining Urban Agglomeration clearly states that the primary task of urban agglomeration is to protect the ecological environment.With the development of remote sensing technology,in order to assess the quality of ecological environment,long-term monitoring has been carried out in the study area.At present,there are many means to assess the ecological environment,but they are mainly concentrated in some small-scale areas,and data acquisition is relatively difficult.How to analyze the ecological environment of Lanxi urban agglomeration is a problem that must be paid attention to in the development planning and construction of Lanxi urban agglomeration.Therefore,this study takes Lanxi Urban Agglomeration as the research object,analyzes the Landsat image data in2000,2005,2010,2015 and 2020,selects 9 indicators such as LPI,AREA-MN,MESH and COHESION,and calculates them using the software Fragstats 4.This paper analyzes the spatiotemporal evolution of various landscape types,expounds the dynamic evolution characteristics of the landscape pattern,and carries out the spatiotemporal pattern and dynamic monitoring analysis of the ecological environment of the Lanxi urban agglomeration through the construction of the RSEI model.Finally,the Pearson correlation coefficient method is used to analyze the response of urban construction land expansion to ecological security.The research results can provide a basis for the ecological environment protection of the study area.The main conclusions of this paper are as follows:(1)From 2000 to 2020,the land use type of Lanxi urban agglomeration was mainly grassland,followed by cultivated land and construction land.In the past 20years,the area of forest land,grassland and water body increased,the area of cultivated land and unused land decreased,and the construction land showed a continuous expansion trend,from 178.56km~2 in 2000 to 282.35km~2in 2020.(2)From 2000 to 2020,the overall construction land area of the Lanxi urban agglomeration showed a trend of increasing year by year.The growth area of construction land in Gansu Province within the scope of Lanxi urban agglomeration is higher than that in Qinghai Province,and the provincial capital cities are higher than prefectural and county level cities.(3)From the perspective of various types of landscape pattern index,the largest patch index of grassland rose from 16.68%to 33.90%,with an increase of 17.22%,ranking first;The change trend of average patch area of cultivated land is consistent with that of forest land;The variation trend of the effective particle size of the water body is consistent with that of the grassland,but it decreased by 38.18 from 2000 to2005;Construction land and increasing patch aggregation.(4)From 2000 to 2020,the ecological index of each county showed an increasing trend.Among them,the ecological environment quality of Anding District,Lintao County,and Ping’an District showed high values during the study period,indicating that these areas had the greatest efforts to improve the ecological environment quality,while the index of other areas showed a fluctuating trend during the study period.However,overall,the remote sensing ecological index increased and the environmental quality gradually improved.(5)From 2000 to 2020,there was a significant negative correlation between UD and F-MESH,W-MESH,and G-MESH indices,indicating that the growth of construction land area was closely related to the fragmentation of cultivated land,forest land,and grassland;There is a significant positive correlation between U-MESH and PD index,indicating that with the increase of construction land patches,the patch density in the entire landscape also increases.U-MESH has a significant negative correlation with the CONTAG and PAFRC indexes,indicating that the fragmentation of construction land increases,resulting in a decrease in the degree of aggregation and extension trend of different patch types within the landscape;There is a significant negative correlation between UEI and(35)RSEI,which shows that the lower the expansion intensity index,the more conducive to the optimization and protection of the ecological environment of the Lanxi urban agglomeration. |
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