Estimation Of Land Use Change In Tianshan Mountainous Area Under RCPs

With the rapid development of the social economy and global warming,the type of land use has also undergone corresponding changes.Land use change is closely related to human life.The Tianshan Mountainous is located in the arid northwestern region,whose climate change and human activities have led to changes in future land use types,which has a significant impact on local socio-economic development.The future land use change in Tianshan Mountainous under different scenarios is estimated,which will provide the government with some reference of the improvement of the ecological environment in Tianshan Mountainous,the prevention and control of natural disasters and the sustainable use of land resources,etc,and will alleviate the contradiction between people,the land and the environment to some extent at the same time,will make the allocation of land resources in the Tianshan Mountainous gradually reasonable and perfect and the sustainable development in the future more scientific.This paper analyzes the climate change of future Representative Concentration Pathways in the Tianshan Mountainous based on climate,natural topography,location conditions and social economy.The Future Land Use Simulation model is used to calibrate and verificate,the status of land use change in Tianshan Mountain area from 2010 to 2017 is analyzed.Based on the FLUS model,the land use changes in the Tianshan Mountainous in 2050 under the three scenarios of RCP2.6,RCP4.5 and RCP8.5 are estimated,and the land use structure and land use transfer are analyzed.The main conclusions are summarized as follows:(1)The Kappa coefficients of the FLUS model calibration and verification period are respectively 0.71 and 0.74,respectively,and the overall accuracy is respectively 0.83 and 0.84.It is shown that the simulation results of the FLUS model are similar to the current land use map,and the distribution of the land use types is consistent.The model can be used to estimate the future land use change in the Tianshan Mountainous.(2)Delta downscaling of the CMIP5 global climate model set data from 1970 to 1999 is conducted.After downscaling,the multi-year average of the baseline period is similar to the measured value.The annual average temperature error is about 0.15°C,and the relative error of annual cumulative precipitation is 1%-5%.The climate data is calibrated and verificated.The results show that the CMIP5 multi-mode set has higher simulation accuracy for the annual average temperature,and the simulation effect is better;the simulation accuracy of the annual cumulative precipitation is general.In the three scenarios,the annual average temperature and the average annual cumulative precipitation in the Tianshan Mountainous in 2050 increase compared with the baseline period.In some years,precipitation decreasescompared with the baseline period,but the overall trend shows an increasing trend.(3)Under the RCPs scenario,the land structure has undergone major changes in 2050,and the land use structure is different from 2017.The proportion of forest land in the three RCPs scenarios is the smallest.For the first time in the RCP8.5 scenario,the total area of the city exceeds the area of ice,snow and water.However,grassland and unused land are still the two main types of land use in the Tianshan Mountainous.The sum of grassland and unused land accounts for more than 86%.(4)Under the influence of external factors,the stability of each land use type indicates the degree of difficulty of its affected state and the conversion to other land use types.The comprehensive land use dynamics from large to small are RCP4.5,RCP2.6 and RCP8.5 scenario.In the RCP4.5 scenario,the land use types change most actively,and the transfer areas are the most;those in the RCP2.6 scenario follow,and the land use types are inactive and the change areas are the least in the RCP8.5.Under the three scenarios,the stability of grassland,urban and unused land are better than 88%,the stability of water and forest land are better than 75%,and the stability of ice and snow is poor,both above 58%.(5)Compared with the measured land use in 2017,human activities and climate change have led to different results in the 2050 RCP2.6,RCP4.5,and RCP8.5 scenarios.In 2050,the snow and ice land in the Tianshan Mountainous has been reduced and converted to grassland or unused land,which decreases by 29.2%,34.6%,and 38.4%,respectively in the three scenarios.The urban land area will increase less some of the cultivated land will convert into urban land and grassland,and the forest land area will increase slightly under RCP2.6 and RCP4.5 in 2050.The area of urban land area under the RCP8.5 scenario will be nearly three times of that in 2017.And part of the forest land will convert into grassland.In the 2050 RCP2.6,RCP4.5,and RCP8.5,scenarios the total area of the water body will slight increase and the unused land will be with a decreasing trend,and the RCP4.5 scenario decreases the most.