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Article Dans Une Revue Science Advances Année : 2022

Critical soil moisture thresholds of plant water stress in terrestrial ecosystems

Résumé

Plant water stress occurs at the point when soil moisture (SM) limits transpiration, defining a critical SM threshold ( crit). Knowledge of the spatial distribution of  crit is crucial for future projections of climate and water resources. Here, we use global eddy covariance observations to quantify  crit and evaporative fraction (EF) regimes. Three canonical variables describe how EF is controlled by SM: the maximum EF (EF max),  crit , and slope (S) between EF and SM. We find systematic differences of these three variables across biomes. Variation in  crit , S, and EF max is mostly explained by soil texture, vapor pressure deficit, and precipitation, respectively, as well as vegetation structure. Dryland ecosystems tend to operate at low  crit and show adaptation to water deficits. The negative relationship between  crit and S indicates that dryland ecosystems minimize  crit through mechanisms of sustained SM extraction and transport by xylem. Our results further suggest an optimal adaptation of local EF-SM response that maximizes growing-season evapotranspiration and photosynthesis.
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Dates et versions

hal-04050797 , version 1 (29-03-2023)

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Paternité - Pas d'utilisation commerciale

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Zheng Fu, Philippe Ciais, Andrew F Feldman, Pierre Gentine, David Makowski, et al.. Critical soil moisture thresholds of plant water stress in terrestrial ecosystems. Science Advances , 2022, 8 (44), pp.eabq7827. ⟨10.1126/sciadv.abq7827⟩. ⟨hal-04050797⟩
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