Spatial And Temporal Changes Of Vegetation Cover In Heilongjiang Province Based On Google Earth Engine

The change of vegetation cover is directly related to the regional surface ecosystem,and it is also a key index to evaluate the regional ecology.Therefore,accurate acquisition of vegetation cover is an important basis for sustainable development and dynamic monitoring of vegetation resources.The study of spatiotemporal process of vegetation cover change is also the focus of global change research,in which obtaining large-scale and long-time series of change information is the premise of research.Although the improvement of temporal and spatial resolution of remote sensing image provides a reliable data support for the analysis of regional vegetation cover change,it also brings problems such as large amount of data,low efficiency of image interpretation,large demand for human and material resources,and difficult spatialization of large-scale vegetation resource inventory data.Therefore,this paper explores the detection method of vegetation cover change based on Landsat Image time series,and analyzes the impact of these two factors on vegetation cover change from two aspects of climate and social economy.The main work is as follows:1.The process of traditional remote sensing image analysis is data acquisition,preprocessing,information extraction and geo analysis.This process has the disadvantages of difficult data acquisition,large amount of data and low efficiency of interpretation processing.Google Earth engine(GEE)platform stores a large amount of remote sensing image data and has powerful cloud computing capabilities,as well as the advantages of integrating and analyzing remote sensing image data.Therefore,this paper uses GEE platform to analyze the spatial and temporal changes of vegetation cover in Heilongjiang Province from 2003 to 2018,and uses threshold method and linear regression method to analyze the changes of vegetation cover in Heilongjiang Province from 2003 to 2018,and explains the differences of the analysis results.The results showed that the vegetation coverage of Heilongjiang province increased significantly,and the annual NDVI(normalized difference vegetation index)fluctuated slowly and increased slightly.From the perspective of spatial distribution,the vegetation coverage in the surrounding areas of Harbin city is significantly reduced due to the occupation of cultivated land and grassland by urbanization construction;the vegetation coverage in the eastern Wanda mountain and the northwest Daxinganling area is significantly increased.2.As one of the environmental factors of ecosystem.temperature and precipitation have a key impact on vegetation coverage.In this paper,Kriging interpolation method and linear regression method are used to analyze the temporal and spatial changes of temperature and precipitation in the past 16 years.Combined with the results of the study on the change of vegetation cover in Heilongjiang Province in the past 16 years,the spatial correlation analysis method is used to analyze the response of vegetation cover to climate factors on the pixel scale.The experimental results show that:the influence of temperature and precipitation on vegetation cover shows spatial difference,and the positive correlation area of vegetation cover and temperature accounts for 51.48%of the total research area,mainly distributed in Songnen Plain,Sanjiang Plain and Xiaoxing'anling area;the positive correlation area of vegetation cover and precipitation and vegetation cover accounts for 52.69%,mainly distributed in Sanjiang Plain and Wanda mountain area in the East.3.With reference to Google Earth(GE)high-resolution image,the sample data set is established through manual visual interpretation.Based on the GEE platform,the land use status of Heilongjiang in 2003 and 2018 is classified by cart decision tree,and the accuracy of confusion matrix is tested.Based on the results of land cover classification and vegetation cover change,the land cover types converted from vegetation cover change are analyzed.Two public driving factors(social and economic development,agricultural development)that cause land use change are extracted by principal component analysis,and the annual driving intensity is analyzed.Compared with cultivated land and forest land,urban construction land has more obvious influence on social and economic factors,and the driving force of three land types change in Heilongjiang Province is gradually strengthening.