Land Land Use Simulation And Land Patch Trade-off Under Multiple Scenarios ——A Case Research Of Wenchuan Earthquake Disaster Area

Land use change is a long-term process,and Wenchuan earthquake hard-hit area is a typical interwoven region with high ecological component and backward development,so it has important significance to study its land use change.Therefore,we took the law of land use change as the breakthrough point,to study this typical mountain-plain transition region,thus to promote the coordinated development of social economy and ecological protection.This article considered both economic and ecological benefit,so it can provide theoretical reference for the parallel development of economic development and ecological protection in similar mountain-rim basin regions.Based on land use data in 2000,2005,2010,2015 and 2018,we used GIS platform,Markov chain,Sensitivity-PressureResilience model(SPR),FLUS and other models.Firstly,we analyzed land use change in the study area from 2000 to 2018 and conducted driving force analysis.Secondly,the importance of ecosystem service function and ecological vulnerability in the study area were comprehensively evaluated,and the land use restriction conversion areas under different scenarios were divided based on this.Then,after verifying the simulation accuracy of FLUS model,we simulate the land use situation of the study area in 2030 in three scenarios.Based on the multi-scenario simulation results,we carry out multi-scenario patch tradeoff judgment and comprehensive integration,and propose a comprehensive integration scheme of land use based on the multi-scenario simulation results.The main results are as follows:(1)From 2000 to 2018,the cultivated land showed an overall decreasing trend,with a decrease of 682.5km~2,2.54%;The increase of forestland was 543.5km~2,1.54%;Grassland decreased by 920.75km~2,3.18%;The water area increased by 203km~2,33.39%;Construction land increased the most from 820.5km~2 to 1,527.75km~2,with an increase of 86.2%;The unused land increased by 122.75km~2,66.89%.In terms of land transfer,the largest amount of transfer is woodland,with an area of 3,987km~2.Construction land had the highest transfer rate,and it transferred out 139.5 km~2,accounting for 17% of the total,most of which mainly transferred to cultivated land.(2)The results of ecological comprehensive evaluation showed that the overall ecological protection demand degree of the study area was high,and the areas with medium or above demands were 71,790.25km~2,accounting for 79.5% of the total area of the study area.The general demand area is 17,101km~2,and the extreme demand area is 38,478.5km~2,both of which are concentrated in the west of the Longmen Mountain Fault zone.The land use types of these area are mainly forestland and grassland with strong ecological function.The general demand area with lower grades and comparative demand area are mainly distributed in the eastern plain area of the study area,with a total area of 18,515km~2,accounting for20.5%.(3)Multi-scenario land use simulation results show that: Under the natural scenario,land use change followed the law of land use change from 2015 to 2018.The area of cultivated land,grassland and unused land showed a decreasing trend,while the area of forestland,water area and construction land showed an expanding trend,with cultivated land decreasing most and construction land increasing most;Under the planning constraint scenario,the reduction of cultivated land was significantly controlled,and the area of forestland increased further,indicating that under the planning constraint scenario,both cultivated land and forestland were well protected,and the expansion of construction land in the study area was significantly controlled.Under the ecological protection scenario,forestland increased further and grassland reduction was controlled,indicating that forestland and grassland were well protected under the ecological protection scenario.From the perspective of spatial distribution,there is little difference in the overall spatial distribution pattern of all land types under the three scenarios: cultivated land is mainly concentrated in the southeast flat area;The forestland is mainly distributed in the central Longmen Mountain area.The grassland is mainly distributed in the western plateau and high mountain area.Construction land is mainly distributed in the east of Longmen Mountain area and Chengdu plain area,concentrated in Dayi County,Pengzhou city,Mianzhu City,Chongzhou City,Shifang City,Guanghan city and other counties.(4)Conflicting patches of 7,290.5km~2 are extracted according to the simulation results of three scenarios.According to the level of ecological protection demand,slope,current land type,forest line distribution,and major functional zone,we carried out multi-level tradeoff and judgment for the conflicting patches,and proposed an integrated scheme based on multiscenario land use simulation tradeoff result.Compared with the simulation results of the three scenarios,the cultivated land,forestland and grassland are better protected,and the construction land can also be better developed.Therefore,reasonable tradeoffs and judgments play an optimized role,and can better consider the demands of ecological protection and economic development in the future land use planning.