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Journal Article

The importance of radiation for semiempirical water-use efficiency models

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Boese,  Sven
Model-Data Integration, Dr. Nuno Carvalhais, Department Biogeochemical Integration, Dr. M. Reichstein, Max Planck Institute for Biogeochemistry, Max Planck Society;
IMPRS International Max Planck Research School for Global Biogeochemical Cycles, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Jung,  Martin
Global Diagnostic Modelling, Dr. Martin Jung, Department Biogeochemical Integration, Dr. M. Reichstein, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Carvalhais,  Nuno
Model-Data Integration, Dr. Nuno Carvalhais, Department Biogeochemical Integration, Dr. M. Reichstein, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Reichstein,  Markus
Department Biogeochemical Integration, Dr. M. Reichstein, Max Planck Institute for Biogeochemistry, Max Planck Society;

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Fulltext (public)

BGC2574D.pdf
(Publisher version), 824KB

BGC2574.pdf
(Publisher version), 2MB

Supplementary Material (public)

BGC2574s1.pdf
(Supplementary material), 247KB

Citation

Boese, S., Jung, M., Carvalhais, N., & Reichstein, M. (2017). The importance of radiation for semiempirical water-use efficiency models. Biogeosciences, 14(12), 3015-3026. doi:10.5194/bg-14-3015-2017.


Cite as: http://hdl.handle.net/11858/00-001M-0000-002C-34C7-9
Abstract
Water-use efficiency (WUE) is a fundamental property for the coupling of carbon and water cycles in plants and ecosystems. Existing model formulations predicting this variable differ in the type of response of WUE to the atmospheric vapor pressure deficit of water (VPD). We tested a representative WUE model on ecosystem scale at 110 eddy-covariance sites of the FLUXNET initiative by predicting evapotranspiration (ET) based on gross primary productivity (GPP) and VPD. We found that introducing an intercept term in the formulation increases model performance considerably, indicating that an additional factor needs to be considered. We demonstrate that this intercept term varies seasonally and we subsequently associate it with radiation. Replacing the constant intercept term with a linear function of global radiation was found to further improve model predictions of ET. Our new semi-empirical ecosystem WUE formulation indicates that, averaged over all sites, this radiation term accounts for up to half (40–49 %) of transpiration. These empirical findings challenge the current understanding of water-use efficiency on ecosystem-scale.