| Land Useand Cover Changes(LUCC)are the concrete manifestations of the interaction between human activities and nature.Human activities will change the spatial pattern of land use to a certain extent.The carbon sequestration capacity of different land use types varies greatly,and LUCC is often affected by human activities and related policies.Human activities affect carbon storage changes by changing land use types,and LUCC is an important cause of carbon storage changes in terrestrial ecosystems.In order to achieve the "3060" double carbon target,it is great significance analyze land use pattern and its impact on carbon stocks under different development scenarios.Xi ’an is the central city in Northwest China.Taking Xi ’an as the research object,this paper analyzes the characteristics of historical land use structure,dynamic attitude,transfer matrix shift of center of gravity in Xi ’an.Moreover,12 driving factors that may have an impact on LUCC were selected,and three development scenarios were set up according to the 14 th Five-Year Development Plan of Xi ’an City:Natural development scenario(Q1),ecological protection scenario(Q2)and urban development scenario(Q3),PLUS model was used to predict and analyze the spatial distribution pattern of land use under different development scenarios in Xi ’an in 2030,and the single factor and interactive factor driving analysis of 12 driving factors were carried out by geographic detector.The modified localized carbon density and the InVEST model were used to calculate the spatio-temporal evolution characteristics of carbon stocks in Xi ’an in 2000,2010 and 2020 as well as in different simulated future development scenarios.The spatial autocorrelation analysis and hot spot analysis were used to reveal the spatial distribution characteristics of carbon stocks.(1)Xi ’an is mainly composed of cultivated land,forest land and construction land.The main feature of land use change is that cultivated land,grassland and other land types are converted into construction land,and single land use dynamic construction is higher than that other land types.The comprehensive land use change degree from 2000 to 2020 is higher than that of the other two periods.From the comprehensive degree of land use,Xincheng District,Lianhu District and Yanta District and other old urban development and utilization degree is higher.It can be seen from the spatial center of gravity transfer of land use types that the center of gravity transfer of construction land and cultivated land is relatively obvious,mainly because the expansion of construction land encroaches on the surrounding cultivated land.(2)The PLUS model has a high accuracy in predicting the land use of Xi ’an City.Kappa coefficient is 0.89,and the correct grid number in the simulation of 2020 accounts for more than 90% of the actual grid number in the proposed 2020,indicating that the model can well simulate the spatial pattern of land use in Xi ’an city.Three different development scenarios are set in PLUS model: Q1 continues the development pattern from2000 to 2020,and the construction land of Q2 is transformed into ecological land such as grassland,cultivated land,forest land and water body,which is more environmentally friendly than Q1.In Q3,the amount of construction land is greatly and disordered without considering the influence of policies,which seriously occupies the ecological land in the study area.The three different scenarios can basically meet the different development demands of Xi ’an city.In the future,certain ecological protection measures should be implemented under Q2 to make t The spatial pattern of regional land use will develop towards a more environmentally friendly and sustainable direction in the future.Q3’s massive expansion of construction land has damaged the regional development balance,and such development trend should be prevented in the future.(3)The factors and interactions of 12 types of driving factors simulating future land use were detected by using geographic detectors.The p values of single factor detection were all less than 0.001.Through the significance test,the driving explanatory power of population and GDP was the largest.From the interaction detection results,the statistics of the interaction factor q are all above 0.70,indicating that the interaction between any two of the 12 selected driving factors will enhance the spatial differentiation effect on land use pattern,among which the population and GDP factors and other factors still play a leading role,and are stronger than the interaction effect among other factors.(4)The revised local carbon density data of Xi ’an was input into the InVEST model to calculate the carbon storage under three different development scenarios in the future.The carbon storage of Q1 was reduced by 373.28 t compared with 2020.The carbon storage in Q2 increased by 564.73 t compared with that in 2020.Q3 carbon storage decreased by734.15 t compared with 2020.The total carbon storage of Q2 is higher than that of the other two scenarios,and certain ecological protection measures make the total carbon storage increase.As Q3 is free from any constraints,the construction land expands sharply,encroachment on woodland,grassland and cultivated land with high carbon sequestration capacity leads to a substantial reduction of the total carbon storage,twice as much as Q1.(5)The global and local spatial autocorrelation analysis and hot spot analysis of carbon storage in Xi ’an were carried out in Arc GIS software.The carbon storage in Xi ’an city has a strong global positive correlation in the whole space,which has a significant agglomeration characteristic.It can be seen from the hot spot analysis that the spatial distribution of hot and cold spots of carbon storage in Xi ’an has obvious regionalization.Hot spots are mainly distributed in the western Qinling Mountains,while cold spots are mainly distributed in the main urban area.In this paper,the coupled PLUS InVEST model was used to evaluate the future spatial pattern of land use and the spatial evolution trend of terrestrial carbon storage in Xi ’an.In the future,some ecological protection measures should be implemented under Q2 scenario,so as to provide some reference for policy making,land use structure adjustment and "dual carbon" goal realization in Xi ’an. |
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