Study On The Impact Of CO₂ Concentration Changes On The Quality Of Grassland Ecosystem In The Qinghai-Tibet Platea

The impact of climate change on ecosystems has become a global environmental issue.Since the industrial revolution,the excessive use of fossil fuels has triggered a rapid increase in global atmospheric CO₂ concentration,resulting in climate change that has caused significant negative impacts on global ecosystems.The Qinghai-Tibet Plateau is an important ecological security barrier and water-conserving strategic area in China,and the grassland ecosystem,which accounts for the largest area among many ecosystem types on the plateau,and its stability have long been affected by climate change and human activities.The scientific and objective assessment and analysis of the spatial and temporal distribution and changes of CO₂concentration and grassland ecosystem quality in the Qinghai-Tibet Plateau,and the investigation of the impact of CO₂ concentration changes on the quality of grassland ecosystems in the Qinghai-Tibet Plateau,can help to understand the spatial and temporal patterns of changes in regional ecosystem conditions and the response of the Qinghai-Tibet Plateau to climate change.It also has important reference significance for the construction of ecological civilization and the realization of the"double carbon"target.This paper takes the grassland ecosystem of the Tibetan Plateau as the research object,and analyzes the spatial distribution and spatial-temporal variation of atmospheric CO₂concentration data on the Tibetan Plateau by interpolating the GOSAT satellite data using the empirical Bayesian kriging method;based on the newly released national ecosystem quality assessment method,we combine the remote sensing ecological parameters（LAI,FVC,GPP）from 2010-2019 to The EQI values characterizing ecosystem quality were calculated and graded according to EQI;the impact of CO₂ concentration changes on the quality of grassland ecosystems on the Tibetan Plateau and the driving factors affecting the spatial distribution of grassland ecosystem quality on the Tibetan Plateau was focused on using the geodetector model.The main conclusions are as follows.（1）There are more significant temporal variations and spatial differences in atmospheric CO₂ concentrations on the Tibetan Plateau.Temporally,the CO₂ concentration on the Tibetan Plateau shows a fluctuating increase over time,from 386.6 ppm in 2010 to 410.4 ppm in 2019,with an average annual growth rate of 2.4 ppm yr-1,which is higher than the global average growth rate and basically the same as the national average growth rate,and has the characteristics of seasonal changes of high in spring and winter and low in summer and autumn;spatially,it shows a spatial distribution of high in the east and west and low in the south The CO₂ concentration in the central and northern regions of Haixi,Hainan,Yushu and Guoluo Provinces in Qinghai Province and the southern regions of Ali,Nagqu,and Shigatse in Tibet Autonomous Region is significantly lower than that in the eastern regions of Ganzi and Aba Provinces in Sichuan Province and the western regions of Kashgar and Hotan in Xinjiang Autonomous Region.（2）The quality of grassland ecosystems on the Qinghai-Tibet Plateau is characterized by"overall stability and local scattered small changes".In terms of time,the EQI of grassland on the Qinghai-Tibet Plateau increased from 36.37 in 2010 to 36.47 in 2019,with an average annual growth rate of 0.01,and the EQI remained stable overall;in terms of space,the overall spatial distribution pattern of grassland ecosystem quality was"poor in the northwest and excellent in the southeast",from Zhangye City in Gansu Province From Zhangye City,Gansu Province,to the southwest to Shigatse City,Tibet Autonomous Region,an ecosystem quality demarcation zone was formed,and the quality of grassland ecosystems in most areas to the east of the demarcation zone was above medium;to the west of the demarcation zone,the quality of grassland ecosystems in most areas was below medium;and the quality of grassland ecosystems within the demarcation zone was mainly medium.In terms of EQI level changes,the decreasing type of EQI level changes from"low to poor"and"medium to low",mainly in the western and central parts of the Qinghai-Tibet Plateau,while the increasing type of EQI changes from"poor to low"and"medium to low".（2）The change in EQI level is more stable in the region with excellent EQI levels,and the percentage of change is the lowest in the study period.（3）Atmospheric CO₂ concentration and annual precipitation are the main driving factors affecting the spatial distribution of grassland ecosystem quality on the Tibetan Plateau,with annual precipitation and atmospheric CO₂ concentration having strong explanatory power,exceeding 58%and 45%,respectively.Meanwhile,the variation of grassland ecosystem quality on the Tibetan Plateau was also closely related to human activities and near-surface relative humidity,and the explanatory power of human footprint and near-surface relative humidity on the spatial distribution of grassland ecosystem quality on the Tibetan Plateau were both above30%.The explanatory power of near-surface air pressure,topographic distribution,and near-surface air temperature on the spatial distribution of grassland ecosystem quality on the Tibetan Plateau did not exceed 30%,and they were less influential and were secondary drivers.The explanatory power of near-surface wind speed on the spatial distribution of grassland ecosystem quality on the Tibetan Plateau was less than 20%,and the influence on the quality of the grassland ecosystem on the Tibetan Plateau was relatively weak.The interaction between CO₂concentration and annual precipitation has an explanatory power of more than 66%,and the interaction with other drivers is more than 50%,showing a strong interaction power.The atmospheric CO₂ concentration pair is significantly different from the Tibetan Plateau elevation factor and the anthropogenic footprint factor,and not significantly different from the near-surface pressure.