Vegetation Responses To Past And Future Climate Extremes In Mid- And High-latitude Asia

Under the background of global warming,the frequency and intensity of extreme events have increased in high latitudes,as the region with the most serious warming,and the impact on their ecosystems has gradually attracted people's attention.However,there is still a lack of research on the prediction of vegetation changes in the middle and high latitudes of Asia and its relationship with extreme climates.Based on the GLOBMAP leaf area index(LAI),CRU Near-Surface Air Temperature(Tas),precipitation(Pr)and ISCCP-FH Surface Downwelling Shortwave Radiation(Rsds),as well as Tas,Pr,and Rsds from CMIP6,this paper systematically analyzed the response of vegetation change to climate drivers in the mid-to-high latitudes of Asia(MHA)during 1982–2020.Based on the two prediction models of Random Forest(RF)and Extremely Randomized Trees(ERT),and using the prediction data of revised CMIP6 under SSP245 and SSP585 scenarios,LAI in the middle and high latitudes of Asia in the future in 2021–2100 was predicted,and the sensitivity of LAI to each forecast factor was discussed.The influence of historical and future extreme drought and wet on vegetation change in the middle and high latitudes of Asia are also discussed.The main conclusions are as follows:(1)In most areas of the MHA,the annual LAI variations in spring were most affected by temperature,while in areas west of Kazakhstan,central Mongolian Plateau and Greater Khingan Mountains,the annual LAI variations were more sensitive to precipitation.In summer,Tas had the greatest influence on the interannual change of LAI only in high latitudes,and the sensitivity of interannual variation of vegetation to Rsds is highest in central and southern Siberia,shandong Peninsula and northeast Plain.Summer LAI was more sensitive to the change of precipitation in the area from Kazakhstan to Mongolia Plateau with relatively arid climate.(2)Among climate variables,Tas contributed the most to LAI,followed by Pr and Rsds,and there is a certain mutual restraint relationship.Their contributions to LAI reached the maximum value when they exceeded 20?,6 mm day^–1and 115 W m^–2,respectively.In the second half of the 21st century,compared with SSP245,LAI of SSP585 scenario was more sensitive to precipitation,but less sensitive to temperature.(3)In the future,drought and wet events,especially extreme drought and wet events,will occur frequently in the MHA region,and the drought and wet cycle will intensify.Severe drought/wet events will change to extreme drought/wet events,and the increase of drought events will be more significant.The sensitivity of vegetation to drought and wet events will decrease in the future.The sensitivity of vegetation to drought events under SSP585 scenario is much lower than that under SSP245 scenario,which is related to the decrease of vegetation sensitivity to temperature under SSP585 scenario,and there is little difference between the sensitivity of vegetation to flood under SSP245 and SSP585 scenario.