scholarly journals The importance of radiation for semi-empirical water-use efficiency models

2017 ◽  
Author(s):  
Sven Boese ◽  
Martin Jung ◽  
Nuno Carvalhais ◽  
Markus Reichstein
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Vapor Pressure Deficit ◽  
Global Radiation ◽  
Model Performance ◽  
Fundamental Property ◽  
Improve Model ◽  
Model Predictions ◽  
Use Efficiency ◽  
Semi Empirical

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.

scholarly journals The importance of radiation for semiempirical water-use efficiency models

2017 ◽  
Vol 14 (12) ◽  
pp. 3015-3026 ◽  
Author(s):  
Sven Boese ◽  
Martin Jung ◽  
Nuno Carvalhais ◽  
Markus Reichstein
Keyword(s):  
Water Use Efficiency ◽  
Water Use ◽  
Primary Productivity ◽  
Vapor Pressure Deficit ◽  
Global Radiation ◽  
Model Performance ◽  
Fundamental Property ◽  
Improve Model ◽  
Model Predictions ◽  
Use Efficiency

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.

scholarly journals Interannual and Seasonal Variations in Ecosystem Transpiration and Water Use Efficiency in a Tropical Rainforest

Forests ◽  
2018 ◽  
Vol 10 (1) ◽  
pp. 14 ◽  
Author(s):  
Maricar Aguilos ◽  
Clément Stahl ◽  
Benoit Burban ◽  
Bruno Hérault ◽  
Elodie Courtois ◽  
...  
Keyword(s):  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Seasonal Variations ◽  
Radiation Effects ◽  
Global Radiation ◽  
Climate Conditions ◽  
Carbon Cycles ◽  
Use Efficiency ◽  
The Impact

Warmer and drier climates over Amazonia have been predicted for the next century with expected changes in regional water and carbon cycles. We examined the impact of interannual and seasonal variations in climate conditions on ecosystem-level evapotranspiration (ET) and water use efficiency (WUE) to determine key climatic drivers and anticipate the response of these ecosystems to climate change. We used daily climate and eddyflux data recorded at the Guyaflux site in French Guiana from 2004 to 2014. ET and WUE exhibited weak interannual variability. The main climatic driver of ET and WUE was global radiation (Rg), but relative extractable water (REW) and soil temperature (Ts) did also contribute. At the seasonal scale, ET and WUE showed a modal pattern driven by Rg, with maximum values for ET in July and August and for WUE at the beginning of the year. By removing radiation effects during water depleted periods, we showed that soil water stress strongly reduced ET. In contrast, drought conditions enhanced radiation-normalized WUE in almost all the years, suggesting that the lack of soil water had a more severe effect on ecosystem evapotranspiration than on photosynthesis. Our results are of major concern for tropical ecosystem modeling because they suggest that under future climate conditions, tropical forest ecosystems will be able to simultaneously adjust CO2 and H2O fluxes. Yet, for tropical forests under future conditions, the direction of change in WUE at the ecosystem scale is hard to predict, since the impact of radiation on WUE is counterbalanced by adjustments to soil water limitations. Developing mechanistic models that fully integrate the processes associated with CO2 and H2O flux control should help researchers understand and simulate future functional adjustments in these ecosystems.

scholarly journals Consistent Differences in Field Leaf Water-Use Efficiency among Soybean Cultivars

Plants ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 123 ◽  
Author(s):  
James Bunce
Keyword(s):  
Water Use Efficiency ◽  
Carbon Isotope ◽  
Water Use ◽  
Vapor Pressure Deficit ◽  
Cultivar Differences ◽  
Stomatal Response ◽  
Soybean Cultivars ◽  
Air Temperatures ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency

High intrinsic water-use efficiency (WUEi), the ratio of leaf photosynthesis to stomatal conductance, may be a useful trait in adapting crops to water-limited environments. In soybean, cultivar differences in stomatal response to vapor pressure deficit have not consistently translated into differences in WUEi in the field. In this study, six cultivars of soybeans previously shown to differ in WUEi in indoor experiments were grown in the field in Beltsville, Maryland, and tested for mid-day WUEi on nine clear days during the mid-seasons of two years. Measurement dates were chosen for diverse temperatures, and air temperatures ranged from 21 to 34 °C on the different dates. Air saturation deficits for water vapor ranged from 0.9 to 2.2 kPa. Corrected carbon isotope delta values for 13C (CID) were determined on mature, upper canopy leaves harvested during early pod filling each year. WUEi differed among cultivars in both years and the differences were consistent across measurement dates. Correlations between mean WUEi and CID were not significant in either year. It is concluded that consistent cultivar differences in WUEi exist in these soybean cultivars under field conditions, but that carbon isotope ratios may not be useful in identifying them because of cultivar differences in mesophyll conductance.

scholarly journals Transpiration and water use efficiency of maize in different soil moisture conditions

2021 ◽  
Vol 24 (2) ◽  
pp. 105-109
Author(s):  
Jana Klimešová ◽  
Hana Středová ◽  
Agnieszka Klimek-Kopyra ◽  
Tomáš Středa
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Content ◽  
Water Use ◽  
Global Radiation ◽  
Corn Cobs ◽  
Horticultural Crops ◽  
Use Efficiency ◽  
Moisture Conditions ◽  
The Impact

Abstract Globally, agriculture accounts for 80–90% of the fresh water used by humans, and in many crop production systems; this water use is unsustainable. Irrigation of large areas of field and horticultural crops is impossible. Studies of the impact of drought on important field and horticultural crops are necessary to estimate dimensions of adaptation and mitigation measures to climate change. For this purpose, maize was monitored as a model crop in this study. In a three-year experiment (i) using the sap flow measurement method, the transpiration of maize was evaluated during flowering and grain filling, (ii) water use efficiency (WUE) was evaluated in four soil moisture conditions. The intensity of transpiration was closely correlated with the values of global radiation and vapor pressure deficit. However, soil water content was a major factor influencing transpiration under drought stress. The transpiration decreased when water content in the soil reached 28% of available water holding capacity (AWHC), but the yield of corn cobs decreased only under stress of 25% AWHC. Thus, the yield reacted less sensitively to lower water availability than transpiration. WUE increased with decreasing transpiration. Statistically significantly higher WUE was already observed at a water content of 42% AWHC, however, a higher WUE did not lead to a higher yield of corn cobs.

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

2014 ◽  
Vol 41 (14) ◽  
pp. 5005-5013 ◽  
Author(s):  
Sha Zhou ◽  
Bofu Yu ◽  
Yuefei Huang ◽  
Guangqian Wang
Keyword(s):  
Vapor Pressure ◽  
Water Use Efficiency ◽  
Water Use ◽  
Time Scale ◽  
Vapor Pressure Deficit ◽  
Use Efficiency

Drought Resistance and Water Use Efficiency in Acacia saligna

1999 ◽  
Vol 47 (4) ◽  
pp. 577 ◽  
Author(s):  
Rotem Nativ ◽  
Jhonathan E. Ephrath ◽  
Pedro R. Berliner ◽  
Yehoshua Saranga
Keyword(s):  
Water Use Efficiency ◽  
Chlorophyll Content ◽  
Water Use ◽  
Drought Resistance ◽  
Vapor Pressure Deficit ◽  
Acacia Saligna ◽  
Drought Conditions ◽  
Use Efficiency ◽  
Demand Control ◽  
Air Vapor Pressure Deficit

Acacia saligna (Labill.) H.Wendl, a potential crop for forage and wood production, is considered highly drought-resistant. The aim of this study was to characterise some of the physiological traits contributing to drought resistance in A. saligna. Two experiments were conducted: (i) 4-year-old A. saligna were grown in the field under dryland and irrigated treatments and (ii) 6-month-old A. saligna were grown in pots and irrigated to replenish 100% of the transpiration demand (control), or 75% 50% or 25% of the control. Soil-water deficits in the field elicited an increase in osmotic potential in phyllodes. Stomatal conductance was negatively correlated with air vapor pressure deficit under drought conditions in both experiments, whereas under irrigation in the field it was correlated with solar radiation. In the field, dry matter (DM) production under irrigation was only 14% greater (not significant) than under dryland. In the pot experiment, DM production was significantly reduced, and water use efficiency (WUE) and chlorophyll content increased with reduced availability of water. The greater WUE induced by drought could have resulted from stomatal regulation and increased chlorophyll content. Carbon isotope ratios were correlated with the WUE, and may be utilised for selection to further improve the WUE of A. saligna under drought conditions.

scholarly journals Protected Fresh Grapefruit Cultivation Systems: Antipsyllid Screen Effects on Plant Growth and Leaf Transpiration, Vapor Pressure Deficit, and Nutrition

2017 ◽  
Vol 27 (5) ◽  
pp. 666-674 ◽  
Author(s):  
Rhuanito S. Ferrarezi ◽  
Alan L. Wright ◽  
Brian J. Boman ◽  
Arnold W. Schumann ◽  
Fred G. Gmitter ◽  
...  
Keyword(s):  
Plant Growth ◽  
Vapor Pressure ◽  
Water Use Efficiency ◽  
Surface Area ◽  
Water Use ◽  
Vapor Pressure Deficit ◽  
Nitrogen Concentration ◽  
Area Index ◽  
Young Tree ◽  
Use Efficiency

Completely enclosed screen houses can physically exclude contact between the asian citrus psyllid [ACP (Diaphorina citri)] and young, healthy citrus (Citrus sp.) trees and prevent huanglongbing (HLB) disease development. The current study investigated the use of antipsyllid screen houses on plant growth and physiological parameters of young ‘Ray Ruby’ grapefruit (Citrus ×paradisi) trees. We tested two coverings [enclosed screen house and open-air (control)] and two planting systems (in-ground and container-grown), with four replications arranged in a split-plot experimental design. Trees grown inside screen houses developed larger canopy surface area, canopy surface area water use efficiency (CWUE), leaf area index (LAI) and LAI water use efficiency (LAIWUE) relative to trees grown in open-air plots (P < 0.01). Leaf water transpiration increased and leaf vapor pressure deficit (VPD) decreased in trees grown inside screen houses compared with trees grown in the open-air plots. CWUE was negatively related to leaf VPD (P < 0.01). Monthly leaf nitrogen concentration was consistently greater in container-grown trees in the open-air compared with trees grown in-ground and inside the screen houses. However, trees grown in-ground and inside the screen houses did not experience any severe leaf N deficiencies and were the largest trees, presenting the highest canopy surface area and LAI at the end of the study. The screen houses described here provided a better growing environment for in-ground grapefruit because the protective structures accelerated young tree growth compared with open-air plantings while protecting trees from HLB infection.

scholarly journals Divergent gas-exchange and chlorophyll fluorescence in F1 hybrids driving habitat differentiation compared to their parents in Buddleja

2019 ◽  
Author(s):  
Weichang Gong ◽  
Yaqing Chen ◽  
Jian Wang ◽  
Han Yuan
Keyword(s):  
Chlorophyll Fluorescence ◽  
Gas Exchange ◽  
Vapor Pressure ◽  
Water Use Efficiency ◽  
Growth Performance ◽  
Water Use ◽  
Vapor Pressure Deficit ◽  
F1 Hybrids ◽  
Photochemical Quenching ◽  
Use Efficiency

Abstract Background Inter-specific hybridizations were common and can easily take place in Buddleja , and it was an important way for evolution and rapid speciation. The F1 hybrid in this study was a newly identified inter-specific hybridization between B. crispa and B. offic inalis in Sino-Himalayan region. In the natural hybrid zones, F1 hybrids always occupy different habitats from their parents. The objective of this study was to explore environmental acclimatization of F1 hybrids and their parents at physiological and biochemical levels.Results The results showed that F1 hybrids performed as an intermediate in adaptation to their parents, with divergent gas-exchange and chlorophyll fluorescence features. F1 hybrids showed the parallel light compensation point and light saturation point with their parents, but low utilization efficiency to low-light density. They synthesized the greatest total chlorophyll content (10.41 ± 0.56 mg•g -1 ) in leaves than their parents. During the diurnal variation of photosynthesis, F1 hybrids markedly decreased and preserved the stomatal conductance and leaf transpiration rate at a low level. However, they kept high carbon assimilation rate and water-use efficiency with markedly increased vapor pressure deficit. In F1 hybrids, the maximum net photosynthetic rate, maximum water-use efficiency and maximum vapor pressure deficit were 10.48 ± 0.50 mmol CO 2 •mmol -1 photo, 21.52 ± 2.20 µmol•mmol -1 and 4.18 ± 0.55 kPa, respectively. In addition, all Buddleja species performed well and grow healthy with high level of the maximum photochemical efficiency of PSII and low non-photochemical quenching, 0.83 ± 0.004 - 0.85 ± 0.004, and 1.22 ± 0.15 - 1.97 ± 0.08, respectively. In F1 hybrids, they showed great photochemical activity compared to their parental species with high photochemical quenching. Furthermore, the effective quantum yield and electron transport rate presented a similar behavior.Conclusions The results indicated that F1 hybrids have great photochemical activities and growth acclimatization compared to their parents. Associated with the growth performance of F1 hybrids in the homogenous garden, our results suggested that the divergent gas-exchange and chlorophyll fluorescence patterns may facilitate F1 hybrids to respond to different habitats, and to improve growth performance.

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