Study On The Identification And Optimization Of Ecological Network In The Plain Area Of The Lower Yangtze River

In the context of rapid urbanization,maintaining regional ecological security has become an important part of sustainable development research.Especially in China,regional ecological security faces ecological problems such as loss of biodiversity,soil erosion and scarcity of water resources.Since the 18 th National Congress of the Communist Party of C hina,as the construction of ecological civilization has become a national strategy,the systematic protection and restoration of ecological space has received high attention.The optimization of national space under ecological protection and restoration has become increasingly important.The identification and optimization of ecological networks is an important research method to guarantee the regional ecological security pattern and to carry out the ecological protection and restoration of land and space.Based on graph theory and landscape ecology theoretical methods,this paper takes Jintan District in the lower Yangtze River Plain as an example,and uses land use data from 2011 and 2018 as the main data source,combined with remote sensing images and POI data,etc.The regional landscape pattern and evolution trend further clarify the important parameters of the ecological network,such as the minimum area threshold and the optimal distance threshold,to identify the ecological network in the study area in a targeted manner.In terms of ecological network optimization,combined with the characteristics of regional landscapes,the identification of "ecological restoration patches-ecological conservation patches-ecological cultivation patches" under the guidance of ecological blind areas was carried out to further optimize ecological nodes to achieve the purpose of eliminating ecological blind areas;changed the threshold of the landscape resistance to optimize the ecological corridor for connecting the patches in the ecological source.Finally,the ecological network performance before and after optimization and the importance of regional habitat patches are evaluated,and corresponding ecological network restoration strategies are proposed.The main results of the study are as follows:(1)In terms of regional landscape pattern analysis,the highest landscape type in Jintan District is cultivated land,followed by water areas and construction land;the dominant landscape type in the landscape is water areas,while grassland and other land landscape types are the lowest,and are greatly affected by human activities.The least number of patches is construction land and water area per unit area,while the number of patches on woodland,grassland and other land areas is larger,and the patches are more fragmented.The patches of water area have the highest complexity,the irregular shape of the patches,and the stronger the edge effect on biodiversity;the spatial distribution of grassland and other land is the most dispersed,while the spatial distribution of cultivated land and water area is more co ncentrated.In terms of time evolution,there are 34 types of conversions between different landscape types.The main types of transfer are conversion of water areas to construction land,cultivated land to construction land,garden land to construction land,construction land to cultivated land,and water area to cultivated land.In terms of spatial evolution,the transformation density of landscape types in Jintan District varies.The areas with higher transfer density are mainly concentrated in the urban construction and surrounding areas of Jintan District,around Changdang Lake in the south,and parts of the western mountainous regions.(2)In terms of ecological network identification and evolution,through the change of regional habitat patches and the proportion of the total area of the ecological source area with the minimum area threshold,the minimum area threshold of the ecological source area in Jintan District during the study period should be set to 0.1 km2.Changes in the number of links through habitat patches(NL),number of landscape components(NC),equivalent overall connectivity index(EC(IIC)),equivalent possible connectivity index(EC(PC))with distance threshold,and the analysis of plaque importance index d LCP,d IIC,d PC determined that the optimal distance thresholds for Jintan District in 2011 and 2018 were all 400 m.In terms of ecological network characteristics,Jintan District has two major landscape components: Maoshan scenic area in the west and Changdang Lake area in the south,but there are still some isolated habitat patches in the area,which are mainly distributed from the mountainous area in the west to the C hangdang Lake landscape group in the south transitional zone.In terms of the evolution of the ecological network,compared with 2011,the connection of landscape components in C hangdang Lake in the south and parts of the east has impro ved,but the phenomenon of separation of landscape components in the marginal areas of the western mountainous areas still exists and further deteriorates.(3)In terms of ecological network optimization and evaluation,by analyzing the spatial distribution of the original ecological blind area in the study area,the ecological network optimization under the guidance of the ecological blind area is carried out.Among them,in the optimization of ecological nodes,after the identification and optimization o f "ecological restoration patches-ecological conservation patches-ecological cultivation patches",ecological dead zones were basically eliminated,the average length of ecological corridors increased by 529.51 m,and the number increased by 790.After the optimization,the connectivity of the ecological network has been greatly enhanced.The Harary index has increased by 10.92 times,the overall connectivity index(IIC)has increased by 43.45%,and the probability connectivity index(PC)has increased by 99.58%.In the assessment of patch importance,the most important patches in the study area are distributed in the southern C hangdang Lake,Q ianzi Lake wetland and their surrounding areas;the more important patches are distributed around the Tianhuang Lake Wetland Reserve,and the important patches are distributed in the west Maoshan,central and southern of Zhulin Town,Beigan River,Tongji River,Xiaxi River and other areas.Generally,the size of important patches is the smallest,scattered scattered in t he original ecological blind area,which serves as a stepping stone for the interconnection of important patches.(4)In terms of regional ecological network restoration strategies,land and space ecological protection and restoration should focus on the remediation of key areas.Different ecological network restoration strategies such as important patches ecological protection,key nodes ecological restoration,and special regional ecological construction can be adopted.Ecological protection strategies should be adopted for regional important habitat patches.Ecological restoration strategies should be adopted for ecological restoration patches and ecological cultivation patches.And special regional ecological construction strategies should be adopted for the spatial distribution of ecological cultivation patches and original ecological blind spots.Through the differentiated ecological network repair strategy,the goal of reducing the waste of resources and maintaining the stability of the ecological network will be achieved.