Establishment And Optimization Of Ecological Security Pattern Based On Connectivity Index

Ecological security pattern can coordinate the contradiction between economic development and ecological protection from the perspective of man-land relationship.It is more and more applied to the study of the system governance and protection of mountains,rivers,forests,fields and lakes.However,the construction method of ecological security pattern is not perfect.There are some technical difficulties to build ecological resistance surface in the construction of ecological security pattern.Under the force of this view,this paper took the Three Gorges Reservoir Area in Chongqing section(TGRAC)as a case study.Based on the land use change data and related ecological data,ecological sources were identified in terms of ecosystem services’importance and ecological sensitivity.The ecological corridors were modified by patch connectivity index.In order to verify the availability of connectivity index,the correction effect of ecological resistance surface was verified by landscape fragmentation,source connectivity,corridor relative resistance,corridor and construction land conflict,corridor land attributes and other indicators.The ecological corridors were identified through using minimum cumulative resistance model and circuit theory.On the basis of the previous research,this paper identified the ecological weak points,barrier areas,important sources and important corridors.All of these constituted the ecological security pattern of the study area.The results showed as follows:1.Compared with the night light index correction situation and the uncorrected situation,the connectivity index has obvious advantages in correcting the ecological resistance surface.This advantage is mainly reflected in the following aspects.1)Compared with the night light index correction situation and the uncorrected situation,the connectivity index correction of the resistance surface can sharpen the high resistance value area,refine the difference between the middle and low resistance value area,so as to optimize the construction effect of ecological resistance surface.2)After the correction of connectivity index,the downward trend of corridor relative resistance is more obvious.After the correction of connectivity index,the relative resistance of 42 corridors decreased,while that of 2 corridors increased slightly.However,after the correction of night light index,the relative resistance of 36 corridors decreased,7 corridors increased significantly,with an increase of more than 2.4,and 1 Ecological Corridor increased slightly.3)After the connectivity index is modified,the corridor land property is obviously optimized.Compared with the uncorrected situation,the proportion of forest and grassland increased,the proportion of farmland decreased significantly,the proportion of garden land decreased slightly,and other land types changed little.But after night light index correction,the proportion of construction land and farmland of corridor increased significantly,the proportion of forest decreased significantly,the proportion of garden land and water increased slightly,and the proportion of grassland changed little.2.The ecological land area of the study area is 28175.82 km~2,accounting for 61.03%of the total area of the TGRAC.And the area of ecological source was 19227.04 km~2,which accounted for 41.65%of the total area of the TGRAC.Among them,there are 3 extremely important ecological sources,accounting for 91.70%of the total source area;8 moderately important ecological sources,accounting for 1.67%of the total source area;23 generally important ecological sources,accounting for 6.63%of the total source area.The ecological source area was mainly composed of forest land in the northeast and central part of the study area,including Wushan County,Wuxi County,Fengjie County,Kaizhou District,Yunyang County,Wanzhou County,Shizhu County,Fengdu County and Wulong county.Wushan mountain,Dalou mountain,Wuling Mountain,Jinyun Mountain,Tongluo mountain and Mingyue Mountain are included in the scope of ecological source,which almost included the main mountains in the study area.And the ecological source area altitude is more than 500 m.3.A total of 53 ecological corridors were extracted from the study area,including 5 natural corridors dominated by the Yangtze River and its important tributaries.The total length of ecological corridor is 1 641.74 km,which including 1 extremely important corridor,6 important corridors and 46 general important corridors.Except for natural corridor,the length of ecological corridor in the study area is less than 100 km,and there is no super long corridor.The average value of the relative resistance of the corridor is 2.87,which can realize the interconnection of more than 90%of the ecological sources.4.The total number of ecological weak points in TGRAC were 43.Among them,there are21 conflict areas with construction land,8 narrow ecological corridor areas,and 14 conflict areas with construction land and narrow ecological corridor areas.The total area of obstacle area in TGRAC was 2 241.15 km~2.The improvement scores of obstacle areas ranged from 0 to122.27.Among them,the high-level improvement area is 108.21 km~2,the middle-level improvement area is 525.72 km~2,and the low-level improvement area is 1607.23 km~2.The improved areas are basically located on both sides of the ecological corridor,and the advanced improved areas are widely distributed in the northeast of Jiangjin County and the north of Yubei county.5.The ecological connectivity of the study area was well,and the existing ecological corridor can ensure that most of the ecological sources are connected with each other.However,corridors and blockage of strategic points were lack in some areas.Therefore,according to the current situation of ecological network in the study area,three optimized corridors are proposed.At the same time,this study suggests that priority should be given to the restoration of No.1and No.2 optimized corridors,so as to realize the interconnection of all ecological sources and ensure the integrity of the ecological network system in the study area.