| The continuous expansion of human activities not only destroys the land ecosystem,but also threatens the sustainable development of land.Grasping the law of land use change,coordinating urban expansion with ecological environment security,and predicting the direction of land use change can provide a certain reference for urban planning.Taking Nanning City as the research area,according to the land use classification standard,the land use types of Nanning City in 2005,2010,2015 and 2018 were divided into six land types,namely,cultivated land,woodland,grassland,construction land,water body and unused land.From three aspects of land use quantity change speed,the condition of transfer of land use and land use degree composite index,the land use change characteristics and regularity were analyzed from 2005 to 2018.Combined with the situation of land use change in Nanning City,nine driving factors including nature,social economy and accessibility were selected.Logistic regression analysis and ROC curve were used to verify the driving factors.Based on the comprehensive evaluation of land ecological security in Nanning City,selecting eight factors such as topography,ecological value,ecological function,landscape types,ecological sensitivityas resistance factors,the minimum cumulative resistance model was used to delimit land ecological security zone.The Markov-Flus model was comprehensively used to predict the land use in 2018,and its validity was tested.The land use pattern of the study area in 2026 was simulated under the natural development scenario,ecological security scenario and ecological optimization scenario,and the comparative analysis was carried out.Finally,the corresponding countermeasures and suggestions were put forward according to the land use situation of Nanning city.The main research conclusions are as follows:(1)From 2005 to 2018,the change speed of construction land in Nanning increased year by year,the construction land increased by 29,025.63hm~2,and the cultivated land decreased by17,858.97hm~2.Through the analysis of land use transfer,it can be found that the mutual transfer of cultivated land,woodland and construction land was obvious from 2005 to 2018,and the transfer amount of cultivated land was the largest,with a total of 41068.23hm~2,of which 34.58%was converted to woodland and 54.92%to construction land.The comprehensive index of land use in Nanning shows a rising trend year by year,indicating that the proportion of construction expansion is getting higher and higher,and the urban expansion trend is obvious.Combination of Nanning city land use change situation,nature,social economy and the accessibility of a total of nine factors driving,Logistic regression analysis was carried out on the driving factors of different grid scales,and the results showed that slope direction and the effects of a population density of every class were negligible,when the grid size is 75m×75m,ROC has the highest value and is greater than 0.7,shows that choice of seven driving factors can explain the characteristics of land use change in Nanning.(2)Using the environment-society-economy method to evaluate the land ecological security in Nanning city,it can be found that the comprehensive index of land ecological security in Nanning city increases year by year,which indicates that the land ecological security in Nanning is getting higher and higher.According to the principle of"source-sink",the ecological source and construction source were selected,and eight resistance factors were selected from five aspects,including landform,ecological value,ecological function,landscape type and ecological sensitivity.Using the minimum cumulative resistance model to define the ecological security control area,the area of prohibited development zone is 172853.84hm~2,restricted development zone is 1111859.74hm~2,optimized development zone is 742597.24hm~2and key development zone is 180227.62hm~2.It is forbidden to develop zones with complex terrain and high water conservation function and ecological value.Restricting development zones to focus on restoring ecological functions;As a buffer zone between ecological protection and urban construction,the optimized development zone is relatively stable and suitable for optimized development.The key development zones are located on flat ground,which are less disturbed by human activities and are suitable for construction land.(3)Based on the 2010 land use data,the Markov-Flus composite model was used to simulate the land use layout in 2018,the results of cultivated land,forest land,grassland,water area,construction land and unused land simulation accuracy was 88.12%,90.45%,85.95%,86.11%,92.64%,86.33%respectively,all higher than 85%,the Kappa coefficient is 0.89,greater than 0.75.Model simulation effect is ideal,can be used to simulate the situation of land utilization in 2026.Under the three scenarios of natural development,ecological security and ecological optimization,land use changes in quantity and space are different.Under the natural development scenario,the area changes of woodland,cultivated land and construction land are very obvious,and the construction land spread to all sides.Under the ecological security scenario,the proportion of ecological land increased significantly,and the expansion of construction land was limited to a certain extent.In the ecological optimization scenario,the growth rate of construction land decreased and the proportion of ecological land increased.Compared with the previous two scenarios,the structure and layout of various land uses were further optimized. |
