| Under the condition of unreasonable utilization of land resources,how to make intensive and efficient use of limited land resources,promote the coordination of ecological and economic benefits,and attain a harmonious relationship between human and land has become a popular and difficult problem in the optimal land allocation,and an important topic of geography research.The Nansi Lake basin is an important ecological security barrier in Shandong Province,which also plays a vital role in the eastern route of south-to-north water transfer project.In recent years,with the growth of population and the expansion of urban scale in the Nansi Lake basin,the phenomenon of land resource scarcity in the basin was particularly prominent,and the water environment and ecological security could not be guaranteed.Taking the Nansi Lake basin as the study area,this study firstly analyzed the spatial-temporal changes of land use types from 1990 to 2020 in terms of both land use quantity and spatial structure based on the current land use data of seven periods in 1990,1995,2000,2005,2010,2015 and 2020;Secondly,considering the actual situation and data availability of the Nansi Lake basin,12 driving factors of land use change were selected from three aspects:natural environment,socio-economic factors and geographical accessibility,and the binary logistic regression results were tested and analyzed by using ROC curves;Furthermore,the spatial distribution structure of land use in 2020 was simulated based on the Geo SOS-FLUS model,and the credibility of the simulation results was tested with the land use data in 2020.The Geo SOS-FLUS model was used to simulate the situation of each land use type under different scenarios in 2035,and then used the 2020as the research base period,and the demand scale of land use types estimated by the Markov model was taken as the target image of land use in 2035,and the Geo SOS-FLUS model was applied to simulate the situation of each land use type under different scenarios in 2035.Finally,the landscape pattern index was selected to compare and analyze the different characteristics of land use landscape patterns under three different scenarios.The main findings were as follows:(1)The land use structure underwent significant spatio-temporal changes during1990-2020.On the one hand,the areas of cultivated land,forest land,grassland,and unused land all have different decreasing trends,decreasing by 1181.33 km~2,263.04km~2,394.52 km~2 and 606.75 km~2,respectively,among which the area of forest land had a small climbing trend after 2015;On the other hand,construction land and water area have increased to different degrees,among which construction land has been in a period of high expansion,with an area of 1822.03 km~2.From the magnitude of change of each land use type and the dynamic attitude of land use,the active degree of of each land use type in the Nansi Lake basin from 1990 to 2020 was high.The analysis of the change of land use degree showed that the comprehensive degree index of land use was greater than 297 and increasing from 1990 to 2020,which indicated that the depth and breadth of land use in the Nansi Lake basin have gradually increased in the past 30 years.and there were frequent transformation processes between land use types,among which,cultivated land was the main contributor to the area transferred to construction land,and the transfer of cultivated land to construction land occurred in the areas around the towns in the county and urban areas,with an overall trend of expansion to the southwest and northwest of the basin.In conclusion,the dynamic degree of land use in the Nansi Lake basin was high from 1990 to 2020.(2)Considering the principle of selecting driving factors comprehensively,12driving factors that meet the requirements were selected,and then the correlation between land use change and the influencing factors was tested by the binary logistic regression analysis method.The study results showed that the values of ROC curves of the six land use types were all greater than 0.75,indicating that the selected driving factors had a strong explanatory power and good correlation for land use patterns.Therefore,the driving factors could be used to model and predict the probability of occurrence of land use types in the Nansi Lake basin.(3)Through the overlay analysis with the actual land use data in 2020,the overall accuracy of the correct raster number of the land use raster map simulated by the Geo SOS-FLUS model reached 89.97%,the value of the Kappa coefficient was 0.8629,and the overall accuracy reached 0.9341,indicating that this simulation was effective and the relevant model parameters were set reasonably,and the simulation results of this model could meet the needs of the future land use simulation and prediction in the Nansi Lake basin.(4)The changes of land use types in the Nansi Lakes basin in 2035 under the natural development scenario,cultivated land protection scenario,and ecological constraint scenario were consistent,but the magnitude of changes and spatial distribution varied greatly.Under the natural development scenario,the interaction between various land uses becomes more obvious,the fragmentation of the landscape in the basin would be higher,the area of cultivated land would still have a significant decrease,while the area of construction land would have a significant upward trend,and there was a tendency for the spatial layout of construction land to expand to the surrounding cultivated land,grassland and forest land on the basis of the original urban areas of counties and cities;Compared with the natural development scenario,the area of cultivated land transferred under the cultivated land protection scenario was reduced by 335.94 km~2,while the expansion of construction land was effectively curbed,and the spatial aggregation of the landscape pattern in the basin was higher,so that the quantity of concentrated and high-quality farmland was guaranteed,which was conducive to improving land productivity;Under the ecological constraint scenario,the area transfer out of forest land,grassland,and water area were reduced,resulting the area of ecological land was further protected,and the stability of the ecosystem in the basin was better,which could improve the ability to resist external disturbance factors such as non-point source pollution.The comparison results of the three different scenarios showed that all types of land under the ecological constraint scenario got balanced changes,and the landscape layout was more reasonable,indicating that this scenario was conducive to promoting the sustainable development of the ecosystem in the Nansi Lake basin.Meanwhile,the simulation results of different land use types under the ecological constraint scenario are highly consistent with the ecological spatial restoration layout in the special plan for ecological protection and restoration of the Nansi Lake basin(2021-2035),which further verified the reasonableness of the ecological constraint scenario setting.Therefore,the application of Geo SOS-FLUS model for simulation and optimization of land use structure to achieve intensive use and reasonable allocation of land resources in the basin was proven to be effective. |
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