The effect of vapor pressure deficit on water use efficiency at the subdaily time scale

Zhou, Sha; Yu, Bofu; Huang, Yuefei; Wang, Guangqian

doi:10.1002/2014gl060741

Cited by 154 publications

(174 citation statements)

References 39 publications

(56 reference statements)

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“…Physiological models (e.g., Katul S. Boese et al: The importance of radiation for semiempirical water-use efficiency models et al, 2010) suggest stomatal contraction with increasing VPD, as plants aim to minimize water loss. This was found to be an important factor in the ecosystem scale as shown by Zhou et al (2014) for half-hourly observations and by Zhou et al (2015) for daily observations. In both studies, the response of WUE could be approximated to be proportional to VPD −0.5 .…”

Section: Introductionmentioning

confidence: 87%

“…Corresponding variants were evaluated with ecosystem-scale flux measurements gathered by the FLUXNET 1 in empirical studies (Beer et al, 2009;Zhou et al, 2014Zhou et al, , 2015. The central difference between the existing models is the response of g s or G s to VPD, resulting in different dependencies of WUE on VPD.…”

Section: Introductionmentioning

confidence: 99%

“…Any transpiration resulting from this part of stomatal conductance should be expected to be proportional to the gradient of the partial pressure of water vapor, quantified by the atmospheric VPD observations. In contrast to formulations commonly used in stand, land surface, and vegetation models (de Kauwe et al, 2013), this process is not considered in current ecosystem-scale WUE formulations (Zhou et al, 2014(Zhou et al, , 2015.…”

Section: Introductionmentioning

confidence: 99%

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The importance of radiation for semiempirical water-use efficiency models

et al. 2017

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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 the 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 semiempirical ecosystem WUE formulation indicates that, averaged over all sites, this radiation term accounts for up to half (39-47 %) of transpiration. These empirical findings challenge the current understanding of water-use efficiency on the ecosystem scale.

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Section: Introductionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The importance of radiation for semiempirical water-use efficiency models

et al. 2017

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“…统的碳水耦合特征 (Zhou et al, 2014(Zhou et al, , 2015。另外, Cv, coefficient of variation; r, correlation coefficient. Table 4 k* values of optimal water use efficiency (oWUE) and its correlation coefficient (r) with oWUE and underlying water use efficiency (uWUE) at the hourly and daily scales during 2014-2016 …”

Section: 碳同化和水分蒸腾由植物通过气孔行为控制通常用水分利用效率(Wue 即单位水分消耗量所mentioning

confidence: 99%

Revised algorithm of ecosystem water use efficiency for semi-arid steppe in the Loess Plateau of China

Liu¹,

Qi²,

Yi-Lan³

et al. 2017

Chinese Journal of Plant Ecology

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Aims We evaluated the applicability of different measures of water use efficiency through analyzing the coupled dynamics of GPP and evapotranspiration in the semi-arid steppe in the Loess Plateau of China. Our objective is to explore the applicability of two quantitative measures of ecosystem water use efficiency-inherent water use efficiency (IWUE) and underlying water use efficiency (uWUE) -for the semi-arid steppe and to endeavor necessary modifications. Methods The consistency and stability of three indices of water use efficiency formulations (i.e. WUE, IWUE, uWUE) were calculated and compared at hourly, daily and annual time scales before proposing an optimal water use efficiency (oWUE). These indices were additionally used to quantify their importances in modeling the diel change of gross primary production (GPP). The yielded-accuracy of the prediction was used for justifying their uses. Important findings IWUE and uWUE appeared suitable for examining the coupled water-carbon characteristics of vegetation at hourly and daily scales, whereas WUE was more plausible on the annual and interannual scales. The optimized water use efficiency index did not improve the prediction of the coupled water-carbon characteristics as compared with uWUE, but it improved the prediction of GPP and its dynamics. oWUE and uWUE improved the predictions of GPP in the peak growing period, while WUE predicted the GPP better at the early and late growing season. Interestingly, we found that IWUE was not suitable for predicting GPP and its dynamics. The results will be of great importance in modeling the effects of climate change on the carbon assimilation and water cycle for the future. Key words water use efficiency; inherent water use efficiency; underlying water use efficiency; optimal water use efficiency; predicted gross primary production

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“…At the ecosystem level where direct measurements of A and T are not available, WUE is simply calculated 15 as the ratio of gross primary productivity (GPP) to total evapotranspiration (ET) (Kuglitsch et al, 2008). Further, the effect of vapor pressure deficit (VPD) on stomatal response can be taken into account giving formulations such as iW U E = GP P · V P D ET and uW U E = GP P · √ V P D ET…”

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confidence: 99%

Water stress induced breakdown of carbon-water relations: indicators from diurnal FLUXNET patterns

Nelson¹,

Migliavacca²,

Reichstein³

et al. 2017

Preprint

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Abstract. Understanding of terrestrial carbon and water cycles is currently hampered by an uncertainty in how to capture the large variety of plant responses to drought across climates, ecological strategies, and environments. In FLUXNET, the global network of CO2 and H2O flux observations, many sites do not uniformly report the ancillary variables needed to study drought response physiology such as soil moisture, sap flux, or species composition. In this sense, the use of diurnal energy, water, and carbon flux patterns to derive clues on ecosystem water limitation responses at a daily resolution could 5 prove valuable, if nothing less than a benchmark to test current hypotheses. To this end, we propose two data-driven indicators derived directly from the eddy covariance data and based on theorized physiological responses to hydraulic and non-stomatal limitations. Hydraulic limitations (i.e. intra-plant limitations to water movement) are proxied using the relative diurnal centroid (C * ET ), which measures the degree to which the flux of evapotranspiration (ET) is shifted toward the morning. Non-stomatal limitations (e.g. inhibitions of biochemical reactions, Rubisco activity, and/or mesophyll conductance) are characterized by 10 the Diurnal Water:Carbon Index (DWCI), which measures the degree of coupling between ET and gross primary productivity (GPP) within each day. Globally, we found indications of hydraulic limitations in the form of significantly high frequencies of morning shifted days in dry/Mediterranean climates and savanna/evergreen plant functional types (PFT), whereas high frequencies of decoupling were dominated by dry climates and grassland/savanna PFTs indicating a prevalence of non-stomatal limitations in these ecosystems. Overall, both the diurnal centroid and DWCI were associated with high net radiation and low 15 latent energy typical of drought. Using three water use efficiency (WUE) models, we found the mean differences between expected and observed WUE to be 0.59 to -0.14 umol/mmol and -0.56 to -0.69 umol/mmol for decoupled and morning shifted days respectively compared to mean differences -1.4 to -1.7 umol/mmol in dry conditions. These results suggest that morning shifts/hydraulic responses are associated with an increase in WUE whereas decoupling/non-stomatal limitations are not.

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The effect of vapor pressure deficit on water use efficiency at the subdaily time scale

Cited by 154 publications

References 39 publications

The importance of radiation for semiempirical water-use efficiency models

The importance of radiation for semiempirical water-use efficiency models

Revised algorithm of ecosystem water use efficiency for semi-arid steppe in the Loess Plateau of China

Water stress induced breakdown of carbon-water relations: indicators from diurnal FLUXNET patterns

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