| With the accelerated urbanisation process,massive encroachment of construction land on ecological land,which has led to various ecological and environmental problems such as the degradation of regional ecosystem services and the decrease of biological diversity,posing a threat to the ecological and environment security of the region.Urban agglomerations are areas where urbanization activities are concentrated and significantly affected by human activities,and the integrity and connectivity of their ecosystems are compromised.Landscape patterns can be used to characterize the temporal and spatial variability of a landscape and are a method for assessing ecosystems.Ecological network is an organic network constructed according to the principles of landscape ecology,with the research objectives of functionality,stability and consistency of ecological processes in the region,and the construction of ecological network is an effective measure to cope with the ecological and environmental impacts caused by urbanization.Therefore,this paper takes Harbin–Changchun urban agglomeration as the research area,and analyzes the spatial and temporal changes of landscape types and landscape pattern changes from 1990 to2020,the landscape pattern is used to characterize the temporal and spatial changes of the landscape,which is a method to assess the ecosystem,and constructs the landscape ecological network with the methods of hotspot change and circuit theory,and follows the steps of"source identification-resistance surface construction-corridor extraction-pinch point and obstacle point identification-construct ecological network-propose restoration strategy"are used to The ecological network of Harbin–Changchun urban agglomeration is constructed,and the restoration strategy of landscape ecological security of Harbin–Changchun urban agglomeration is proposed.The main conclusions of this paper are as follows:(1)From 1990 to 2020,the landscape types in the study area were always dominated by farmland land and forest;in the past 30 years,the areas of farmland and forest increased by 2,475.34 km~2and 1,417.25 km~2,respectively;the areas of grassland and wetland decreased by 2,504.26 km~2and 1654.62 km~2,respectively,and the area of construction land increased by 1,867.48 km~2,and the overall range of hot spots of ecological land reduction gradually decreased.(2)The PD indices of the landscape of Harbin–Changchun urban agglomeration shows an overall change characteristic of decreasing first and then increasing,with the smallest value in 2010 and the lowest degree of landscape fragmentation.The MPS indices shows an overall trend of increasing first and then decreasing,which indicates that the degree of landscape fragmentation increases between 2010 and 2020.The COHESION indices and AI indices of Harbin–Changchun urban agglomeration are basically unchanged,indicating that there are well-connected patches in the landscape,the landscape is more aggregated.In the built-up area of Changchun and the area along the Harbin–Changchun railroad,the degree of fragmentation increases,while Daqing has many increased hotspots,indicating that the ecological function of the region has improved.(3)The results of the ecological network of the Harbin–Changchun urban agglomeration constructed based on circuit theory show that there are 26 ecological source sites within the Harbin–Changchun urban agglomeration,with a total area of108,580.52 km~2,accounting for 33.71%of the study area.There are 86 ecological corridors with a total length of 55353.09 km,mostly in Daqing City.There are 153ecological pinch points with a total area of 23,429.18 km~2.372 ecological obstacle points in the Harbin–Changchun urban agglomeration with a total area of 42,838.65km~2,of which Changchun is the most widely distributed.The area of ecological land increase hotspots is 3614.51 km~2;the area of ecological land decrease hotspots is1941.27 km~2.(4)Based on ecological corridors,ecological pinch points,ecological barrier points,ecological land increase hotspots and ecological land decrease hotspots,key areas,protection areas,restoration areas,improvement areas and protection corridors are delineated.There are 51 key areas with a total area of 1723.49 km~2;114improvement areas with a total area of 15705.81 km~2;83 restoration areas with a total area of 10601.83 km~2;26 protected areas with a total area of 112195.03 km~2;and 67conservation corridors with a total length of 17091.76 km.(5)Ecosystems near non-urban centers and water sources are more intact,more conducive to biotic migration and have a higher degree of landscape connectivity.It is suggested to strengthen the ecological source areas around and within cities,among which Changchun should be a key restoration area due to more arable land,and Daqing should be a key protection area due to more wetlands and lakes and obvious ecological fragmentation. |
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