Evolution Of Landscape Pattern And Construction Of Ecological Security Pat-Tern In Chaohu Lake Basin

The modernization of harmonious coexistence between man and nature is one of the five characteristics of Chinese path to modernization proposed in the report of the 20th National Congress of the Communist Party of China.To achieve this goal,we must adhere to the policy of sustainable development,constantly consolidate the bottom line of ecological environment security,build a more solid ecological security barrier,and promote economic and social development in the green direction.This study takes the Chaohu Lake Basin as the research scope,utilizes LUCC data and landscape pattern models,and with the support of GIS and Fragstates,analyzes the spatiotemporal dynamic evolution of landscape types.Based on natural environment and socio-economic factors,principal component analysis and grey correlation analysis are used to deeply explore the internal driving mechanism of landscape type pattern evolution;With the help of landscape ecology and the theory of "pattern process function",a landscape integrated ecological risk assessment model was constructed by using soil erosion sensitivity index and landscape ecology risk index to reveal the internal texture of landscape pattern and ecological process response;Based on the landscape ecology security assessment,according to the research steps of "ecological sourceresistance surface construction-ecological corridor-ecological node",the security pattern of landscape ecology is constructed by using MSPA,minimum cumulative resistance surface(MCR)model and circuit theory;According to the construction results of landscape ecology security pattern,analyze and identify buffer zones and key areas of ecological restoration,and propose optimization strategies for landscape ecology security pattern from different perspectives.The main conclusions of this study are as follows:(1)The landscape area of Chaohu Lake Basin is cultivated land>construction land>forest land>grassland>water area>unused land;The proportion of arable land is over 60%,mainly distributed in the flat and abundant water network plain area around Chaohu Lake;Forests and grasslands are mainly distributed in the mountainous and hilly areas to the southwest and northeast of Chaohu Lake;The distribution of construction land is relatively scattered,gradually focusing on the jurisdiction of Hefei City,with the largest area growth,mostly from the transfer of arable land.The landscape dominance of Chaohu Lake basin is mainly cultivated land,and the spatial differentiation of landscape pattern indexes is obvious;Over the past 20 years,the degree of landscape fragmentation in the Chaohu Lake Basin has significantly intensified,with strong dispersion and concentration among different landscape types.Except for cultivated land,other landscape patches have developed from dispersion to aggregation,but connectivity has decreased.The evolution of the landscape pattern in the Chaohu Lake Basin is greatly influenced by natural factors,and the proportion of socio-economic factors is gradually increasing.In the future,attention should be paid to socio-economic related factors.(2)The comprehensive ecological risk value of the landscape in the Chaohu Lake Basin gradually increased from 2000 to 2020.Especially in 2020,the high-risk areas and high-risk areas showed a clear expansion trend,mainly due to the impact of heavy rainfall.The Chaohu Lake Basin experienced a "once-in-a-century" flood,which increased the risk of flooding in the basin and caused water levels to rise in some river sections,resulting in flood disasters.From the overall spatial distribution,the high-risk and high-risk areas are expanding from the surrounding areas of the northwest mountain area to the plain area of the water network.In 2020,the area of high-risk areas and high-risk areas in the Chaohu Lake Basin was the largest,followed by medium and low risk areas,and the area of low-risk areas was the smallest;At the county level,except for the municipal jurisdiction,Chaohu City,Shucheng County,and Hanshan County,other districts and counties are mainly high-risk areas,accounting for over 50%of the area.The Moran’s I index of landscape comprehensive ecological risk is low,even negative,showing a trend of first decreasing and then increasing,indicating that the clustering of the Chaohu Lake Basin is weakened first and then strengthened,and the overall clustering is relatively scattered.The spatial distribution of landscape ecology risk accumulation areas is relatively scattered and the law is not obvious.The high-high clustering type is the main type,while the low-low clustering type,high-low clustering type and low-high clustering type are less.(3)The landscape ecology security pattern of Chaohu Lake basin is composed of 15 ecological source areas,34 ecological corridors,12 corridor intersections,26 ecological obstacles and 28 ecological pinch points,showing a rich and complex spatial distribution.The ecological source area is mainly located in the hilly and mountainous areas in the southwest and northeast of Chaohu Lake,mainly due to the lack of forest and grassland in the northern part of the Chaohu Lake basin,which is mainly cultivated and construction land.Ecological obstacle points and pinch points are distributed within the ecological corridor,forming an interconnected network of elements.(4)Based on the minimum cumulative resistance value,a five level ecological buffer zone is constructed to identify the ecological breakpoint area and the key area of ecological restoration.The structural layout of "four cores three zones four belts five corridors" is proposed,and the optimization strategy for the landscape ecology security pattern of the Chaohu Lake basin is proposed.