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The effect of vapor pressure deficit on water use efficiency at the subdaily time scale
Author(s) -
Zhou Sha,
Yu Bofu,
Huang Yuefei,
Wang Guangqian
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl060741
Subject(s) - evapotranspiration , vapour pressure deficit , environmental science , atmospheric sciences , primary production , eddy covariance , ecosystem , transpiration , chemistry , ecology , photosynthesis , physics , biochemistry , biology
Water use efficiency is a critical index for describing carbon‐water coupling in terrestrial ecosystems. However, the nonlinear effect of vapor pressure deficit (VPD) on carbon‐water coupling has not been fully considered. To improve the relationship between gross primary production (GPP) and evapotranspiration (ET) at the subdaily time scale, we propose a new underlying water use efficiency (uWUE = GPP · VPD 0.5 /ET) and a hysteresis model to minimize time lags among GPP, ET, and VPD. Half‐hourly data were used to validate uWUE for seven vegetation types from 42 AmeriFlux sites. Correlation analysis shows that the GPP · VPD 0.5 and ET relationship ( r = 0.844) is better than that between GPP · VPD and ET ( r = 0.802). The hysteresis model supports the GPP · VPD 0.5 and ET relationship. As uWUE is related to CO 2 concentration, its use can improve estimates of GPP and ET and help understand the effect of CO 2 fertilization on carbon storage and water loss.