Changes in Wa...betan Plateau_Binghao JIA.pdf

Changes in Water Use Efficiency Caused by Climate Change,CO2Fertilization,and Land Use Changes on the Tibetan PlateauBinghao JIA1,2,Xin LUO1,Longhuan WANG*1,3,4,and Xin LAI51State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China2Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science&Technology,Nanjing 210044,China3Key Lab of Virtual Geographic Environment(Nanjing Normal University),Ministry of Education,Nanjing 210023,China4Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application,Nanjing 210023,China5Plateau Atmosphere and Environment Key Laboratory of Sichuan Province,Chengdu University of Information Technology,Chengdu 610225,China(Received 22 June 2022;revised 18 August 2022;accepted 24 August 2022)ABSTRACTTerrestrial ecosystem water use efficiency(WUE)is an important indicator for coupling plant photosynthesis andtranspiration,and is also a key factor linking the carbon and water cycles between the land and atmosphere.However,under the combination of climate change and human intervention,the change in WUE is still unclear,especially on theTibetan Plateau(TP).Therefore,satellite remote sensing data and process-based terrestrial biosphere models(TBMs)areused in this study to investigate the spatiotemporal variations of WUE over the TP from 2001 to 2010.Then,the effects ofland use and land cover change(LULCC)and CO2 fertilization on WUE from 19812010 are assessed using TBMs.Results show that climate change is the leading contributor to the change in WUE on the TP,and temperature is the mostimportant factor.LULCC makes a negative contribution to WUE(20.63%),which is greater than the positive contributionof CO2 fertilization(11.65%).In addition,CO2 fertilization can effectively improve ecosystem resilience on the TP.On thenorthwest plateau,the effects of LULCC and CO2 fertilization on WUE are more pronounced during the driest years thanthe annual average.These findings can help researchers understand the response of WUE to climate change and humanactivity and the coupling of the carbon and water cycles over the TP.Key words:water use efficiency,gross primary productivity,evapotranspiration,Tibetan Plateau,carbon and water cycleCitation:Jia,B.H.,X.Luo,L.H.Wang,and X.Lai,2023:Changes in water use efficiency caused by climate change,CO2fertilization,and land use changes on the Tibetan Plateau.Adv.Atmos.Sci.,40(1),144154,https:/doi.org/10.1007/s00376-022-2172-5.Article Highlights:The contributions of CO2 fertilization and land use land cover change(LULCC)to water use efficiency(WUE)arequantitatively assessed.Land use land cover change(LULCC)makes a negative contribution to water use efficiency(WUE),while there is anopposite effect from CO2 fertilization.Temperature is the most important climate factor in determining the changes of water use efficiency(WUE).1.IntroductionPlants play an important role in terrestrial ecosystems.On one hand,vegetation releases its own water into the atmo-sphere through transpiration;on the other hand,it absorbsCO2 from the atmosphere through photosynthesis and synthe-sizes organic carbon to remain in the vegetation itself(Yanget al.,2016;Liu et al.,2020).At the ecosystem level,the car-bon-water coupling between the land and the atmosphere isoften characterized by the ratio of gross primary productivity(GPP)to evapotranspiration(ET)and is called water use effi-*Corresponding author:Longhuan WANGEmail:ADVANCES IN ATMOSPHERIC SCIENCES,VOL.40,JANUARY 2023,144154 Original Paper Institute of Atmospheric Physics/Chinese Academy of Sciences,and Science Press and Springer-Verlag GmbH Germany,part of Springer Nature 2023ciency(WUE;Huang et al.,2015).In addition,WUE is animportant parameter to describe the water adaptation strategyof plants in different growth environments.High WUE repre-sents the performance of vegetation in adapting to the environ-ment by closing stomata and reducing ET under drought con-ditions,while low WUE indicates sufficient water or weak-ened vegetation growth(Guo et al.,2019).The Tibetan Plateau (TP),the highest plateau in theworld,is known as the Asian water tower and is also animportant ecological barrier and water conservation area forChina and Asia(Yao et al.,2017).As one of the most sensitiveareas responding to climate change,the fragile ecosystemon the TP has undergone tremendous changes(Zhang et al.,2014;Lamsal et al.,2017).Drought is one of the most seriousimpacts of climate change,affecting the carbon and watercycles of terrestrial ecosystems on a global and regionalscale(Zhao and Running,2010;Sheffield et al.,2012;Yu etal.,2014).Water stress caused by long-term inadequatewater supply inhibits the normal growth of vegetation andreduces carbon sink,which can lead to a series of disasterssuch as gr