Research On Multi-scenario Simulation Of Urban Construction Land Expansion Under The Constraint Of Ecological Network

In rapidly urbanizing areas,human factors such as intensive use of land,changes in land use patterns,and narrow concepts have led to drastic changes in land use and cover,disorderly expansion of construction land,a large reduction in suitable habitats,and increased fragmentation.my country’s "14th Five-Year Plan" proposes to adhere to the new development concept and achieve high-quality development,among which we must adhere to the "green" development concept.The document requires us to change the development model and abandon the previous development model that destroys the environment and consumes resources.Defining the boundaries of urban construction land expansion and pursuing the harmonious coexistence of man and nature is manifested in maintaining the integrity and stability of landscape,species diversity and ecosystems.The ecological network has the function of restricting the expansion of construction land,strengthening the connectivity of the landscape,and maintaining the diversity of landscapes and species.Therefore,this paper introduces the ecological network into the expansion of urban construction land,analyzes the characteristics of the expansion of urban construction land under the ecological network constraint,and draws a conclusion.There have been studies on ecological networks and urban construction land expansion at home and abroad,but both of these studies have limitations.For example,in terms of ecological networks,existing domestic and foreign researches mainly focus on the identification,construction,optimization and evaluation of key elements of single-scale or multi-scale ecological networks,and lack of ecological network optimization based on temporal and spatial scales;in the study of urban construction land simulation,Most of the existing research methods in China focus on the optimization of the quantity and structure of urban construction land,which are not really implemented in space,lack of scientific and reasonable spatial optimization allocation methods,and most scholars carry out the spatial allocation of urban construction land from the ecological level.,There is almost no optimization of the layout of urban construction land by constructing an ecological network for typical species.As a result,there are relatively few research cases on the comparison of urban land space expansion simulation before and after ecological network constraints.Aiming at the above shortcomings,this paper innovatively combines the optimization of ecological network based on the time-space scale and the simulation of urban construction land expansion,and proposes a topic for the simulation of urban construction land expansion based on the constraints of the ecological network.This paper firstly optimizes the current ecological network of Suzhou,Wuxi and Changzhou in 2015 based on the perspective of space-time scale optimization.The ecological network with the highest optimization benefit is the optimized ecological network,and the Markov-ANN-CA model is used to implement the ecological network without ecological network constraints and the current ecological network constraints.And the multi-scenario simulation of the expansion of urban construction land under the constraints of the optimized ecological network,analyze whether there are ecological network constraints and the impact of the ecological network constraints on the expansion of urban construction land before and after optimization,and compare and analyze the results.Specifically,it can be divided into two parts.The first part is to set different time and space scale scenarios for sub-regional/cross-regional and one-time investment/phased investment,and select the rapid development stage of Suzhou,Wuxi,and Changzhou as the research area,which has a migratory habit.The protected species egret is the focal species.The minimum cumulative resistance model(MCR)is used to establish an ecological network.Under the constraints of quantitative and equal investment in conservation funds,the optimization order of habitat patches is determined,and the changes in the ecological network structure index under different scenarios are compared to judge At the same time,consider whether the time-space-scale optimization scenario can improve the efficiency of ecological network optimization.The second part is to analyze and determine the driving factors for the expansion of urban construction land based on the five scenarios,build a Markov-ANN-CA composite model,and use the ANN-CA simulation plug-in in Arc GIS software to simulate the expansion of urban construction land.Based on the simulation results under the scenarios,conclusions are drawn and relevant policy recommendations are made by analyzing differences in land use transfer changes under different scenarios,differences in landscape safety pattern indexes,and differences in the distribution of newly added construction land in different habitat quality zones.The conclusions drawn are as follows:(1)The ecological network optimization benefit under the spatio-temporal optimization scenario is the highest,and the ecological network optimization performance of the time optimization scenario(ie cross-regional protection scenario)and spatial optimization scenario(ie one-time investment protection scenario)are considered at the same time.Produce synergy.Under the limit of equal protection cost,the network structure index under the one-time investment scenario in Suzhou,Wuxi,and Changzhou is more than the cumulative network structure index α under the cross-regional secondary and fifth successive investment scenarios and the sub-regional primary,secondary,and fifth successive investment scenarios.The average increase is 39.46%,the network structure index β has an average increase of 30.55%,and the network structure index γ has an average increase of 39.42%.(2)On the whole,from the land use transfer matrix,it can be seen that the scale of construction land has increased the most,and the scale of cultivated land has decreased the most;the reduction of woodland,grassland and water area has a positive correlation with the speed of urban development;it has a positive correlation with the current ecology Compared with the network constraint scenario,the optimized ecological network can increase the area of grassland,water area and unused land and restrain the growth of cultivated land,woodland and construction land.Compared with the current ecological network constraint scenario,under the optimized ecological network constraint scenario,grassland increased by 23.49 hectares,water area increased by1622.43 hectares,unused land increased by 34.02 hectares,cultivated land decreased by1551.15 hectares,woodland decreased by 119.07 hectares,and construction land A reduction of 9.72 hectares.(3)With the acceleration of urban development,the fragmentation of urban construction land has decreased,the rules of landscape patches tend to be regular,and the connectivity of patches has increased;after optimization,the ecological network landscape types have more regular patches,higher connectivity,and more balanced landscape types,Which is conducive to exerting the scale effect of land use,protecting animal migration corridors,reducing the impact of ecological isolation,and improving biodiversity and ecosystem stability.Compared with the current ecological network constraint scenario,the number of patches(NP)and patch density(PD)under the optimized ecological network constraint scenario are 11991 and 0.4157 per square kilometer,respectively,which are smaller than the current ecological network constraint scenario,while Shannon The diversity index(SHDI),Shannon evenness index(SHEI)and aggregation index(AI)were 1.4322,0.7360,and 94.6504,respectively,which were all larger than the current ecological network scenario.(4)High-speed development is not conducive to ecological protection and is likely to cause landscape degradation.The optimization of ecological network in the context of ecological network constraints after optimization will protect the quality of the habitat and improve the landscape safety pattern.With the acceleration of urban development,the new construction land occupies a larger area of medium and high-grade habitat quality zones;under the optimized ecological network constraint scenario,the scale and proportion of new urban construction land occupied by high-grade habitat quality zones are 5412.42 hectares and 1.02%,respectively;The scale and proportion of the occupied intermediate habitat quality zone are 73784.52 hectares and 13.91% respectively,which are lower than the corresponding indicators of the current ecological network constraint scenario.Under the optimized ecological network scenario,the newly-added urban construction land occupies a total of 79196.94 hectares and 14.93% of the middle and high-level habitat quality zones and proportions,which are lower than the corresponding indicators under the medium-speed development model.