The Effect Of Drought And High Temperature On The Gross Primary Productivity Of Chinese Vegetation

In recent years,global warming has led to frequent extreme weather events such as droughts and high temperatures,which have had a huge impact on the carbon cycle of global ecosystems.The Gross primary productivity of vegetation(GPP)can characterize the quality of terrestrial ecosystems,which is the largest carbon flux in the global carbon cycle,and is extremely sensitive to climate change.Therefore,it is urgent to accurately and effectively assess the impact of extreme weather events on vegetation GPP.China is taken as an example in this paper,the temperature vegetation drought index(TFDI)calculated based on the sun-induced chlorophyll fluorescence(SIF)data is used to define the extreme drought index,and the extreme high temperature index(TX90P)defined by the relative threshold method is used to analyze its effect on the total vegetation of GPP.It mainly analyzes the characteristics of China’s vegetation GPP,extreme drought,extreme high temperature and the temporal and spatial changes of the two extreme events occurring simultaneously from 2010 to 2018,and explores the effects of three extreme weather events on China’s overall vegetation GPP,different vegetation GPP,and vegetation in different seasons.The results show that extreme weather events have a greater impact on China’s vegetation GPP,the major conclusions are as follows:(1)From 2010 to 2018,the average annual frequency of extreme droughts ranged from 1 to 32,with an average of 7.89 times per year,it shows a spatial pattern of high frequency in the northwest and southeast coastal areas and low in the central area;extreme high temperature,whose average annual frequency ranges from 3.33 to14.25,with an average of 6.23 times per year,which shows a high frequency in parts of southwestern China,while a spatial pattern of low frequency in central Xinjiang,most of China’s northeast regions,and some regions in southern area;extreme drought and The simultaneous occurrence of annual average frequency of extreme high temperature is between 1 and 7.5 times,with an average of 1.99 times each year,showing a high frequency of occurrence in China’s northwest and southern area such as Yunnan province,and a lower spatial pattern in the rest of the regions.(2)Extreme drought has a negative impact on the overall vegetation GPP,and the impact on the four types of vegetation is different,and the descending magnitude is in the order of grassland> cultivated land> woodland> desert;extreme high temperature has a positive impact on the overall vegetation GPP,and the impact on the four types of vegetation is different,The increasing range is grassland> desert> woodland>cultivated land;the simultaneous occurrence of extreme drought and extreme high temperature has a negative impact on the overall vegetation GPP,and the impact on the four types of vegetation is different,and the descending range is forestland> cultivated land> grassland> desert.(3)Extreme drought led to a decline in vegetation GPP in most areas in the 4seasons,with the greatest impact in summer,followed by autumn,and the smallest in spring and winter;extreme high temperature caused an increase in vegetation GPP in most areas during the 4 seasons,with the greatest impact in spring,Followed by winter and the smallest in autumn;extreme drought and extreme high temperature synergistically led to a decline in vegetation GPP in most areas in the four seasons,which had the greatest impact in spring,followed by summer,and the smallest in autumn and winter.