Stomatal response to decreased relative humidity constrains the acceleration of terrestrial evapotranspiration

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Xiao , M , Yu , Z , Kong , D , Gu , X , Mammarella , I , Montagnani , L , Arain , M A , Merbold , L , Magliulo , V , Lohila , A , Buchmann , N , Wolf , S , Gharun , M , Hörtnagl , L , Beringer , J & Gioli , B 2020 , ' Stomatal response to decreased relative humidity constrains the acceleration of terrestrial evapotranspiration ' , Environmental Research Letters , vol. 15 , no. 9 , 094066 . https://doi.org/10.1088/1748-9326/ab9967

Title: Stomatal response to decreased relative humidity constrains the acceleration of terrestrial evapotranspiration
Author: Xiao, Mingzhong; Yu, Zhongbo; Kong, Dongdong; Gu, Xihui; Mammarella, Ivan; Montagnani, Leonardo; Arain, M. Altaf; Merbold, Lutz; Magliulo, Vincenzo; Lohila, Annalea; Buchmann, Nina; Wolf, Sebastian; Gharun, Mana; Hörtnagl, Lukas; Beringer, Jason; Gioli, Beniamino
Contributor: University of Helsinki, Staff Services
University of Helsinki, Finnish Meteorol Inst FMI, Finnish Meteorological Institute, Climate Syst Res
Date: 2020-09
Language: eng
Number of pages: 11
Belongs to series: Environmental Research Letters
ISSN: 1748-9326
URI: http://hdl.handle.net/10138/324390
Abstract: Terrestrial evapotranspiration (ET) is thermodynamically expected to increase with increasing atmospheric temperature; however, the actual constraints on the intensification of ET remain uncertain due to a lack of direct observations. Based on the FLUXNET2015 Dataset, we found that relative humidity (RH) is a more important driver of ET than temperature. While actual ET decrease at reduced RH, potential ET increases, consistently with the complementary relationship (CR) framework stating that the fraction of energy not used for actual ET is dissipated as increased sensible heat flux that in turn increases potential ET. In this study, we proposed an improved CR formulation requiring no parameter calibration and assessed its reliability in estimating ET both at site-level with the FLUXNET2015 Dataset and at basin-level. Using the ERA-Interim meteorological dataset for 1979-2017 to calculate ET, we found that the global terrestrial ET showed an increasing trend until 1998, while the trend started to decline afterwards. Such decline was largely associated with a reduced RH, inducing water stress conditions that triggered stomatal closure to conserve water. For the first time, this study quantified the global-scale implications of changes in RH on terrestrial ET, indicating that the temperature-driven acceleration of the terrestrial water cycle will be likely constrained by terrestrial vegetation feedbacks.
Subject: terrestrial evapotranspiration
relative humidity
global warming
stomata regulation
SOIL-MOISTURE
COMPLEMENTARY RELATIONSHIP
RECENT DECLINE
LAND
EVAPORATION
WATER
TREND
CO2
PHOTOSYNTHESIS
VARIABILITY
1172 Environmental sciences
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