Landscape Ecology Change And Optimization Of Urban Landscape Based On Ecological Flow

Urbanization is the symbol of human civilization and an important social and economic phenomenon in the world today.Population and economic activities continue to gather in cities.Because of the huge resource flows,cities have become ―barely sustainable but paradoxically resilient networks‖.As the growth pole,cities constantly bring the surrounding areas into their own development system,forming the metropolitan area and economic belt.The most obvious characteristic is the sprawl growth of urban space.The expansion of urban space changes the type and pattern of landscape,resulting in the disturbance of ecological functions.The original material circulation and energy flow were blocked in space and time,which caused a series of ecological and environmental problems and reduced the ecosystem service function.Our country advocates sustainable urbanization,and the 18 th national congress of the communist party of China also puts forward that the construction of ecological civilization should be given a prominent position,the study of landscape ecological changes in the process of urbanization and the maintenance of the integrity of urban ecosystem have important theoretical and practical significance.Changchun City is one of the major cities in Northeast China.It is located in the hinterland of Songliao Plain.There are few limiting factors for urban space expansion,and the characteristics of urban space sprawl are obvious.At present,Changchun is still the main area of population migration in Jilin Province.With the development and opening of Changchun-Jilin-Tumen Pilot Area and the construction of Changchun New Area,the urban space of Changchun City will continue to expand,which will greatly change the landscape of surrounding areas.Therefore,this study takes Changchun city as the research object,based on the perspective of ecological flow,to study the changes of landscape ecology and how to maintain the ecological flow through landscape optimization.The landscape type distribution data of Changchun in 1995,2005 and 2015 were obtained through the interpretation of Landsat images as the basic data of the study.Urban fringe area is a region with drastic landscape changes and a key area of ecological flow path.The spatial range of urban fringe areas were identified by using breakpoint method combined with information entropy.The ecological effects of different landscape types and pattern changes were analyzed,and the evaluation methods of landscape fragmentation degree,landscape connectivity and landscape ecological health level were constructed from space.Based on the perspective of ecological flow,this paper adopts the analysis method of landscape ecology,introduced the minimum cumulative resistance model(MCR)and computational fluid dynamics(CFD)model,simulated the potential path of ecological flow,and put forward the landscape optimization plan of changchun city based on the above evaluation results.The main contents and conclusions of the study are as follows:(1)Changchun city landscape change characteristics analysis.The intensity of landscape change from 1995 to 2005 is greater than that from 2005 to 2015.For the total new increment of construction land,the central urban area accounts for 32.64%.The development of urbanization occupies a large number of farmland.The top five types of conversion in the central urban area are: conversion from farmland to construction land,conversion from farmland to woodland,conversion from farmland to wetland,conversion from woodland to construction land,and conversion from wetland to construction land.The area of farmland converted into construction land accounted for 58.80% of the total farmland in 1995,the farmland converted into woodland accounted for 13.02% of the total in the early stage,and the unchanged farmland only accounted for 27.08%.Hot spots with serious ecological landscape degradation in Changchun city are distributed in a "ring + finger" pattern,including urban fringe and areas on both sides of the road.The degradation of ecological landscape in urban fringe weakens the ecological flow.(2)Identification and change analysis of urban fringe areas.From 1995 to 2015,the area of the urban fringe grew rapidly,increasing by 533.13 km2 and reaching a growth rate of 197.66%.Economic development and population growth are the main influencing factors for the expansion.Development zones,urban planning,topography and road network affect the specific expansion direction of urban fringe areas,and urban fringe areas are mainly expanded in the directions of east,southeast and north.From 1995 to 2005 and from 2005 to 2015,the main types of changes were peripheral expansion type and internal filling type respectively,and the changes of internal filling type mainly occurred in the west and southwest directions of the city.Limited by the total amount of space allowed to be built in the city,from 2005 to 2015,mining the available space in the urban fringe has become an important way of urban space development.(3)Landscape ecological changes from the perspective of ecological flow.From 1995 to 2015,urban space expansion resulted in the fragmentation and reduced connectivity of landscape patches,and both patch density(PD)and edge density(ED)showed a change from disorder to orderly development,and the shape of landscape patches tended to be regular.From the perspective of space,the change rate of the landscape index value in the urban fringe area is greater than that in the metropolitan area and the core area,and the degree of aggregation index(AI)in the urban fringe area decreases greatly,indicating that the dispersion of the landscape patches in the urban fringe area increases.The AI index forms three circles: high value area,low value area and high value area from the center.The increase of forest area in the fringe promoted the level of ecological health.However,in terms of time,the ecological health degradation area is concentrated in the urban fringe area and in the Southeast area,including part of Jingyue District and part of Nanguan District.The results show that to improve the landscape ecological health,we should not only enhance the mount of ecological land,but also maintain a good landscape pattern and maintain the natural ecological process.(4)Study on landscape pattern optimization based on ecological flow.The identification of potential ecological corridors is a key problem to be solved in landscape optimization and ecological flow construction.First,the resistance of ecological flow expansion in two-dimensional space was evaluated by using MCR model,and then the wind field characteristics in three-dimensional space in Changchun city were simulated by introducing CFD model to comprehensively represent the circulation path of biological species,substance and energy.The results show that there is strong connectivity in Nanhu Park,Animal and Plant Park,Yitong River and other large ecological spaces within the city.The area below 30 m is also the main scope of human activities.CFD simulation shows that there are potential ecological flow paths in the direction of the dominant wind at 30 m altitude.Finally,based on the simulation results of potential path,ecological landscape degradation area and landscape ecological health degradation area,the landscape layout optimization was put forward,to provide support for the coordination of urban development and ecological protection in Changchun.