Spatiotemporal Changes Of Ecological Quality And Its Influencing Factors Of The Qinghai-Tibetan Plateau From 2000 To 2020

The Qinghai-Tibetan Plateau(QTP),an important water conservation area,various rare wild animals and plants,and an indicator of global climate change,is ecological barrier and national security hub in China.Complex topography,harsh natural conditions,and sensitive and fragile ecosystems characterize the QTP.Recently,with the rapid change of climate and the expansion and intensification of human activities,the QTP has experienced tremendous pressure to coordinate the fragile environment and economic development.Therefore,it is of great significance to assess the ecological quality of the QTP,reveal the spatiotemporal changes of ecological quality and its response to natural factors and human activities to boost the harmonious coexistence between man and nature,and promote the sustainable development of the QTP.The Improved Remote Sensing Ecological Index(IRSEI)for the QTP is constructed based on multiple remote sensing data sets.The data used in this study includes multiple remote sensing data sets,the meteorological,topographical,hydrological data,social statistics,residential areas,roads and other data.This paper analyzes the spatiotemporal changes of the ecological quality of the QTP from 2000to 2020.Based on coefficient of variation,Sen-Mann Kendall method,spatial autocorrelation,gravity migration model,correlation analysis and so on.The effects of temperature,precipitation,topography,population,economy,meat yield and grazing activities on ecological quality were revealed.Main conclusions are as follows.(1)The IRSEI which introduced Gross Primary Productivity(GPP)has improved the accuracy of ecological quality assessment on the QTP,and the R~2between its value and the aboveground biomass of grassland(AGB)has increased from 0.085 to0.235.(2)The ecological quality(IRSEI)of is low with a spatial pattern of high in the southeast and low in the northwest in the QTP.The IRSEI decreased first and then increased in the past 20 years.The ecological quality of 79.73%of the QTP is increased,especailly in the Qaidam montane desert zone.The deterioration of the IRSEI occurred mainly in the south slope of the eastern Himalayas.The IRSEI center of gravity has shifted from the west to east and south to the north in the past 20 years.(3)The IRSEI negatively correlated with temperature over the QTP in the past 20years,and the negative correlation area(50.16%)was mainly distributed in the Qaidam montane desert zone,while the positive correlation area was located primarily in the Golog-nagqu alpine shrub meadow zone.The IRSEI positively correlated with precipitation,and the positive correlation area(73.42%)was mainly distributed in the eastern Qinghai-Qilian montane grassland zone,while the negative correlation subareas were located in the south slope of the eastern Himalayas.(4)The elevation and slope significantly influenced ecological quality of the QTP.The IRSEI negatively correlated with altitude and positively correlated with slope.The most significant decrease of the ecological quality is in the subregions which the height is smaller than 2500m and the slope is abrupt or steep,situated in the south slope of the eastern Himalayas.At the elevation of 2500～3500m and the flat slope,the rise is most obvious,and is mainly distributed in the eastern Qinghai-Qilian montane grassland zone.The IRSEI on flat land was the worst,and the rise was apparent.(5)The IRSEI was positively correlated with the population density and GDP per capita on the QTP in the past 20 years.The positive correlation areas were in the eastern Qinghai-Qilian montane grassland zone and the Qaidam montane desert zone.The negative correlation regions are in the south slope of the eastern Himalayas.The IRSEI has positively correlated with per capita meat consumption,but the positive and negative correlation areas were similar.The positive correlation areas were mainly distributed in the Qaidam montane desert zone,while the negative correlation areas were mainly located in the southern Qinghai Alpine Meadow Grassland Zone.(6)There was a significant negative correlation between IRSEI and livestock density on the QTP in the past 20 years;the correlation coefficient was-0.589.Among them,the livestock density of the Tibet Autonomous Region(TAR)and grazing intensity of the River and Lake Headwaters Region(RLHR)were negatively correlated with the IRSEI.The significant negative correlation area of TAR and RLHR accounted respectively for 32.26%and 71.07%,located in the northwest of the TAR,the west of Zhongba County,and the northeast of Geji of the RLHR.(7)The ecological quality in different geographical regions of the QTP were affected by various factors.Some specific suggestions are put forward based on the actural situation of each subarea for ecological protection and restoration.