Analysis Of Temporal And Spatial Variation Characteristics And Driving Factors Of Land Use In Zhengzhou City Based On GEE

Land use and cover change is the result of the interaction between human activities and the natural environment,and plays a very important role in the process of global change.With the rapid development of the global economy,the transformation of nature by human activities are becoming more and more frequent,especially in the cities with rapid economic development.The land use and cover status has changed significantly,and land conflicts and environmental problems have become increasingly prominent.Therefore,research on the change of land use and its driving factors is of great significance for the rational planning and sustainable utilization of land resources.By taking Zhengzhou as the research area,and based on the new remote sensing cloud computing platform Google Earth Engine(GEE),we studied the temporal and spatial changing characteristics of land use in Zhengzhou from 2000 to 2020 in this paper.We solved the problem of low efficiency of traditional methods in processing large-scale long-term remote sensing data.The Landsat data of the minimum cloud cover in the target year in the study area are obtained by GEE,with the obtained images being classified by the method of random forest.According to the classification results,the temporal and spatial variation characteristics of land use types are analyzed from five aspects: land use structure,dynamic degree,degree,types of transformation and spatial distribution.Finally,the differential and factor detection,interaction detection and risk detection in the geographic detector are used to quantitatively analyze the impact of each driving factor on land use change in Zhengzhou.The main research conclusions are as follows:(1)This paper proposes an adaptive parameter adjustment strategy based on grid search(Grid Search CV)to improve the random forest algorithm,which can select the optimal parameters according to different sample data and conditions of the study area.Compared with the unoptimized random forest algorithm,CART decision trees algorithm and support vector machine algorithm(SVM),the results show that the optimized random forest algorithm has good classification accuracy.The optimized random forest algorithm is used to classify the remote sensing image of each target year in the study area.The overall accuracy and Kappa coefficient of the classification results for each target year were above 0.90 and above 0.86,respectively.(2)Through the analysis of the classification results,the spatial-temporal variation characteristics of land use in Zhengzhou from 2000 to 2020 are obtained.From the perspective of time,in terms of changes in land use structure,forests and grasslands,cultivated land,and construction land in Zhengzhou City accounted for a large proportion in each year,while water areas and unused land accounted for a small proportion.In terms of land use dynamic degree,the single dynamic degree of cultivated land in the past 20 years has been negative,indicating that the cultivated land area has been decreasing state,the single dynamic degree of construction land is positive,indicating that the area of construction land has been increasing,and the single dynamic degree of other land types is positive or negative,indicating that the area has increased or decreased;In the past 20 years,the comprehensive index of land use degree in Zhengzhou has increased year by year,indicating that Zhengzhou’s land use has been in a state of development;in terms of land use type transfer,the most cultivated land has been transferred out in the past 20 years,mainly converted into construction land and forest grassland,while the area of construction land has been transferred the most,mainly from cultivated land.From the perspective of space,the overall location of forest and grassland has not changed significantly;cultivated land has been greatly reduced in the main urban area,Xinzheng and Zhongmu,and a small reduction in Gongyi,Dengfeng and Xinmi;construction land is from the main urban area and surrounding counties and cities.Large-scale expansion,in which the eastern region and the main urban area are spatially connected.(3)From the results of the geographic detector,it can be seen that the terrain factor is the main factor affecting the change of land use degree in Zhengzhou,and the level of influence is basically stable;population density,GDP and night light brightness have important influence on the change of land use degree in Zhengzhou and the level of influence continues to increase,which shows that with the development of the economy,social and economic factors play a stronger and stronger role in the degree of land use.The influence of the interaction between the driving factors is greater than that of a single factor,and the effect type is two-factor enhancement,indicating that the interaction between the factors further promotes the change of land use degree in Zhengzhou.The difference of land use degree within each driving factor classification is obvious,and the change trend is also different with the increase of the driving factor level.The degree of land use in Zhengzhou is negatively correlated with the factors of elevation,slope and traffic location;The degree of land use in Zhengzhou is positively correlated with the average annual temperature,population density,GDP and nighttime light brightness.