Construction Of Ecological Security Pattern In Handan City Based On Complex Network Analysis

Handan is located in the southern part of Hebei Province,at the junction of the four provinces of Jin Ji-Ru-Yu,and is designated as a"regional central city"in the Beijing Jin-Ji Cooperative Development Program and the Central Plains Economic Zone Plan.A major shift in regional development strategy is bound to lead to huge changes in industrial patterns and land use,which will lead to an intensification of contradictions between human society and natural ecological systems and threaten regional ecological security and sustainable social development.Based on this,this thesis takes handan city as the main data source,uses pattern evolution analysis,landscape morphology analysis,eco-spatial network and complex network analysis to study the evolution characteristics of handan city landscape,extracts long-term sequence ecological network,and identifies key points,lines and surfaces of the regional landscape based on cyberspace and topology.The main conclusions are as follows:(1)The cultivated land,grassland and construction land are the main ecosystem types in Handan City.The total area of the three types of land use is about 90%of the total area in the study area.Over 20 years from 1997 to 2020,cultivated land decreased continuously,in particular from 8,554.28 km~2 to 7,917.91 km~2 in the six years from 2004to 2010,with an annual area change rate of-1.24%.In contrast to cultivated land,the area under construction showed a continuous increase,from 983.43 km~2 in 1997 to 2,104.38km~2 in 2020,with an annual change rate of 4.96%;Changes in woodland area occurred mainly between 1997 and 2004,from 1,457.79 km~2 to 254.14 km~2,an annual rate of change of-11.80%,with relatively small changes in other land types.(2)Morphological and spatial analysis of the land use data of Handan city in each year showed that the seven landscape components were reduced in order of core area,voids,edges,branches,roundabouts,isolated islands and connecting areas.In the data of each year,the core area accounted for about 15%of the total area of the study area,mainly in the Taihang foothills on the west side,and decreased rapidly in the east.Core area plaques larger than 1km2 and with a plaque importance index greater than 0.1 were selected as ecological sources.The number of ecological sources in 1997,2004,2010,2015,2020 was 35,56,54,56,54,with areas of 1,853.06 km~2,1,606.12 km~2,1,614.47km~2,1,621.76 km~2,1,606.12 km~2,mainly in the west of the study area.Land use type,elevation,slope,vegetation cover and night light index were selected as resistance factors,and the ecological resistance surface of the study area was obtained by spatial superposition.The results show that the ecological resistance of Handan city in recent decades shows a trend of high in the east and low in the west,and high in the center and low in the periphery.In each year,the maximum resistance was 813 in 1997,followed by a downward trend in the following years,but the area dominated by the higher resistance continued to expand outwards to reach its maximum extent in 2015 and 2020.Based on the circuit theory model,the Linkage Pathways Tool tool in the Linkage Mapper Arc10.3tbx Toolkit was used to identify ecological corridors in the study area.The results showed that there were 22 ecological corridors in 1997,94,99,104 and 93 in 2004,2010,2015and 2020 respectively.In each year,ecological corridors are mainly concentrated in the western part of the study area,while the central and eastern corridors are extremely sparse.The Pinchpoint Mapper tool and the Pinchpoint region of the Fairwise Pattern Recognition Study Area were used to grade the pinchpoints according to the current density of the study area,resulting in 33,61,68,58 and 43 ecological pinchpoints for each year.The ecological pinch points in each year are mainly located in Shixian and Wuan cities,followed by Magnetism and Fengfeng mining areas.(3)Topological characteristics of ecological networks in each year of the study area were analyzed by using and degree distribution,mean path length,clustering coefficient,Page Rank,and other complex network topological indicators.The results showed that the network averaged 2.79,3.48,3.81,3.93 and 4.43 years,respectively,with a significant upward trend;The mean path length was 5.15,4.30,3.81,3.71 and 3.65 respectively,and the network degree distribution was Poisson distribution.The mean clustering coefficients were 0.40,0.48,0.47,0.40 and 0.64,respectively.Network Page Rank had maximum values of 0.69,0.05,0.04,0.04,and 0.04,respectively,with a downward trend followed by a stable trend.The ecological networks in each year of the study area were random networks.The variation of network indexes shows that the ecological network in the study area belongs to the random small world network.Based on topological index analysis,Tyson polygon,gravity model and other methods,the key ecological node extraction,ecological node partitioning and corridor grading were carried out.Finally,the regional ecological safety pattern was formed.The results showed that there were 16primary ecological junctions,16 secondary nodes,19 primary corridors and 19 primary corridors in the study area.