Scale Effects And Construction Of Ecological Networks In Luohe City

The accelerated urbanization has resulted in a severe fragmentation in the urban landscape.Landscape ecology,as an interdisciplinary science that integrates landscape spatial patterns and ecological processes,is of great significance to reveal change characteristics and ecological processes in the landscape patterns and to solve ecological problems in the process of urbanization.The scale effects on landscape patterns and the construction of ecological network have also been major issues in landscape ecology research.Unmanned aerial vehicle(UAV)imagery has great potential for the study of scale effects on urban landscape patterns because of its high spatial resolution,versatility,and remarkable operational improvements in recent years.In this study,the landscape classes of urban land use were extracted from UAV imagery of Luohe central city with 0.09 m spatial resolution based on Geographic Information System(GIS)techniques and principles of landscape ecology.The scale effects on landscape patterns are analyzed quantitatively by using FRAGSTATS 4.2.And then this paper analyzes the landscape pattern and extracts potential ecological corridors under optimal grain size by using minimal cumulative resistance model and gravity model,evaluates ecological networks by using the ecological network connectivity indexes α,β,γ and cost ratio.The results were as follows:(1)The landscape patterns in downtown area of Luohe City have obvious grain size effect and extent effect.(2)The smaller the spatial grain size is,the more stable the change trend of the landscape indexes is,which usually brought more realistic processes of ecology in the landscape patterns;the grain size effect on landscape patterns at the landscape level is mainly caused by the changes of landscape dominance,fragmentation,and aggregation of buildings,roads,and green land;35 m is the largest threshold of spatial grain size,whereas 3m is the optimal spatial grain size during the study of grain size effect.(3)The landscape dominance,fragmentation,and contagion decrease,whereas the landscape complexity and aggregation increase with the increase in spatial extent;the landscape patterns has obvious spatial gradient distribution characteristics,with the transition from impermeable soil surfaces in the central city to the permeable soil surfaces in the outside city;the aggregation of buildings and roads is higher in the central city area,whereas the fragmentation of green land is higher in the city,and all of these factors lead to the gradient change in the landscape patterns at the landscape level;the stability of the landscape components is related to the city scale.(4)The fragmentation is higher at the landscape level under 3 m grain size.At the class level,as types of ecological sources,the green land landscape has a higher fragmentation,a more complex shape,and a lower aggregation;whereas the water landscape has a lower fragmentation,a simpler shape,and a higher aggregation.(5)The ecological sources mainly distribute in the Sha-Li River landscape belt.The potential ecological corridors with theoretical values distribute equally.However,the ecological corridors passing through construction land distribute less.According to the types of networks,the study constructs optimized ecological network,circuit ecological network and branching ecological network;The order of connectivity indexes of the three types of ecological networks from the largest to the smallest is ranked as follows: optimized ecological network> circular ecological network> branching ecological network,and the optimized ecological network is the optimal ecological network in the study area;the first-level ecological network is basic anastomotic with the direction of the Sha-Li River,thus the study constructs a multi-level ecological network as the core of Sha-Li River landscape belt,and constructs a multi-level ecological node based on the multi-level ecological network,integrates the green space resources of Luohe City.(6)The UAV survey technology could generate urban landscape ecological information with accuracy and efficiency,reveal the response characteristics of the scale effects on landscape patterns,provide a scientific basis for the optimization of landscape patterns and the planning of the urban-rural landscape,construct the urban ecological network system with accuracy,and provide theoretical and technical support for the urban green land systems’ planning in Luohe city.