The functional dependence of canopy conductance on water vapor pressure deficit revisited

2018 ◽  
Vol 62 (7) ◽  
pp. 1211-1220 ◽  
Author(s):  
Marcel Fuchs ◽  
Cecilia Stanghellini
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Functional Dependence ◽  
Water Vapor Pressure ◽  
Canopy Conductance ◽  
Water Vapor Pressure Deficit

scholarly journals Water Vapor Pressure Deficit in Portugal and Implications for the Development of the Invasive African Citrus Psyllid Trioza erytreae

Insects ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 229 ◽  
Author(s):  
Paulo Eduardo Branco Paiva ◽  
Tânia Cota ◽  
Luís Neto ◽  
Celestino Soares ◽  
José Carlos Tomás ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Control Measures ◽  
Effective Control ◽  
First Instar ◽  
Trioza Erytreae ◽  
Water Vapor Pressure Deficit

African citrus psyllid (Trioza erytreae (Del Guercio)) is a vector insect of the bacterium Candidatus Liberibacter africanus, the putative causal agent of Huanglongbing, the most devastating citrus disease in the world. The insect was found on the island of Madeira in 1994 and in mainland Portugal in 2015. Present in the north and center of the country, it is a threat to Algarve, the main citrus-producing region. Trioza erytreae eggs and first instar nymphs are sensitive to the combination of high temperatures and low relative humidity. Daily maximum air temperature and minimum relative humidity data from 18 weather stations were used to calculate the water vapor pressure deficit (vpd) from 2004 to 2018 at various locations. Based on the mean vpd and the number of unfavorable days (vpd < 34.5 and vpd < 56 mbar) of two time periods (February to May and June to September), less favorable zones for T. erytreae were identified. The zones with thermal and water conditions like those observed in the Castelo Branco and Portalegre (Center), Beja (Alentejo), Alte, and Norinha (Algarve) stations showed climatic restrictions to the development of eggs and first instar nymphs of African citrus psyllid. Effective control measures, such as the introduction and mass release of Tamarixia dryi (Waterson), a specific parasitoid, and chemical control are necessary in favorable periods for T. erytreae development, such as in spring and in areas with limited or no climate restrictions.

Physical and visual properties of grape rachis as affected by water vapor pressure deficit

2011 ◽  
Vol 59 (1) ◽  
pp. 25-33 ◽  
Author(s):  
A. Lichter ◽  
T. Kaplunov ◽  
Y. Zutahy ◽  
A. Daus ◽  
V. Alchanatis ◽  
...  
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Water Vapor Pressure Deficit ◽  
Visual Properties

scholarly journals Modeling the Response of Canopy Stomatal Conductance to Humidity

2009 ◽  
Vol 10 (2) ◽  
pp. 521-532 ◽  
Author(s):  
Shusen Wang ◽  
Yan Yang ◽  
Alexander P. Trishchenko ◽  
Alan G. Barr ◽  
T. A. Black ◽  
...  
Keyword(s):  
Water Vapor ◽  
Stomatal Conductance ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Power Function ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Nonlinear Function ◽  
Environmental Variable ◽  
Water Vapor Pressure Deficit

Abstract Humidity of air is a key environmental variable in controlling the stomatal conductance (g) of plant leaves. The stomatal conductance–humidity relationships employed in the Ball–Woodrow–Berry (BWB) model and the Leuning model have been widely used in the last decade. Results of independent evaluations of the two models vary greatly. In this study, the authors develop a new diagnostic parameter that is based on canopy water vapor and CO2 fluxes to assess the response of canopy g to humidity. Using eddy-covariance flux measurements at three boreal forest sites in Canada, they critically examine the performance of the BWB and the Leuning models. The results show that the BWB model, which employs a linear relationship between g and relative humidity (hs), leads to large underestimates of g when the air is wet. The Leuning model, which employs a nonlinear function of water vapor pressure deficit (Ds), reduced this bias, but it still could not adequately capture the significant increase of g under the wet conditions. New models are proposed to improve the prediction of canopy g to humidity. The best performance was obtained by the model that employs a power function of Ds, followed by the model that employs a power function of relative humidity deficit (1 − hs). The results also indicate that models based on water vapor pressure deficit generally performed better than those based on relative humidity. This is consistent with the hypothesis that the stomatal aperture responds to leaf water loss because water vapor pressure deficit rather than relative humidity directly affects the transpiration rate of canopy leaves.

HUMIDITY AND SOIL WATER INFLUENCE THE TRANSPIRATION RESPONSE OF MAIZE TO CO2 ENRICHMENT

1990 ◽  
Vol 70 (4) ◽  
pp. 941-948 ◽  
Author(s):  
ALAN G. BARR ◽  
K. M. KING ◽  
G. W. THURTELL ◽  
M. E. D. GRAHAM
Keyword(s):  
Vapor Pressure ◽  
Soil Water ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Period Doubling ◽  
Co2 Enrichment ◽  
Leaf Conductance ◽  
High Vapor ◽  
Water Vapor Pressure Deficit ◽  
The Impact

The impact of increasing atmospheric CO2 on the productivity of C4 crops may vary with soil water availability. This study investigates the hypothesis that elevating CO2 in Zea mays L. reduces the degree to which transpiration is limited by soil water at high vapor pressure deficits or low soil water contents. Plants growing in controlled environments at 300 and 600 μmol mol−1 CO2 were exposed daily to five levels of vapor pressure deficit as water was withheld and the soil dried over an 8-d period. Doubling CO2 caused an overall reduction of 23% in the transpiration rate and 34% in the leaf conductance, but the effect of CO2 on transpiration and leaf conductance was greatest at high soil water content and low vapor pressure deficit, when soil water least limited transpiration. Implications for the productivity of C4 crops in the field are discussed.Key words: Maize, transpiration, carbon dioxide, soil water, vapor pressure deficit, controlled environment

scholarly journals Improving the LPJmL4-SPITFIRE vegetation–fire model for South America using satellite data

2019 ◽  
Vol 12 (12) ◽  
pp. 5029-5054 ◽  
Author(s):  
Markus Drüke ◽  
Matthias Forkel ◽  
Werner von Bloh ◽  
Boris Sakschewski ◽  
Manoel Cardoso ◽  
...  
Keyword(s):  
Water Vapor ◽  
South America ◽  
Ecosystem Functioning ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Fire Danger ◽  
Burned Area ◽  
Model Data ◽  
Water Vapor Pressure Deficit ◽  
Global Vegetation

Abstract. Vegetation fires influence global vegetation distribution, ecosystem functioning, and global carbon cycling. Specifically in South America, changes in fire occurrence together with land-use change accelerate ecosystem fragmentation and increase the vulnerability of tropical forests and savannas to climate change. Dynamic global vegetation models (DGVMs) are valuable tools to estimate the effects of fire on ecosystem functioning and carbon cycling under future climate changes. However, most fire-enabled DGVMs have problems in capturing the magnitude, spatial patterns, and temporal dynamics of burned area as observed by satellites. As fire is controlled by the interplay of weather conditions, vegetation properties, and human activities, fire modules in DGVMs can be improved in various aspects. In this study we focus on improving the controls of climate and hence fuel moisture content on fire danger in the LPJmL4-SPITFIRE DGVM in South America, especially for the Brazilian fire-prone biomes of Caatinga and Cerrado. We therefore test two alternative model formulations (standard Nesterov Index and a newly implemented water vapor pressure deficit) for climate effects on fire danger within a formal model–data integration setup where we estimate model parameters against satellite datasets of burned area (GFED4) and aboveground biomass of trees. Our results show that the optimized model improves the representation of spatial patterns and the seasonal to interannual dynamics of burned area especially in the Cerrado and Caatinga regions. In addition, the model improves the simulation of aboveground biomass and the spatial distribution of plant functional types (PFTs). We obtained the best results by using the water vapor pressure deficit (VPD) for the calculation of fire danger. The VPD includes, in comparison to the Nesterov Index, a representation of the air humidity and the vegetation density. This work shows the successful application of a systematic model–data integration setup, as well as the integration of a new fire danger formulation, in order to optimize a process-based fire-enabled DGVM. It further highlights the potential of this approach to achieve a new level of accuracy in comprehensive global fire modeling and prediction.

scholarly journals Stomatal behavior of different grapevine cultivars in response to soil water status and air water vapor pressure deficit

OENO One ◽  
2010 ◽  
Vol 44 (1) ◽  
pp. 9 ◽  
Author(s):  
Jorge A. Prieto ◽  
Éric Lebon ◽  
Hernán Ojeda
Keyword(s):  
Water Vapor ◽  
Gas Exchange ◽  
Soil Water ◽  
Vapor Pressure Deficit ◽  
Leaf Gas Exchange ◽  
Water Status ◽  
Water Vapor Pressure ◽  
Leaf Water ◽  
Stomatal Response ◽  
Water Vapor Pressure Deficit

<p style="text-align: justify;"><strong>Aims</strong>: Genetic variability in grapevine cultivars may influence their strategy to cope with drought through stomatal regulation of transpiration rate. The aim of the present study was to evaluate the stomatal sensitivity of five cultivars (Ekigaïna, Grenache, Marselan, Mourvèdre, and Syrah) to soil water status and air water vapor pressure deficit (VPD).</p><p style="text-align: justify;"><strong>Methods and results</strong>: Leaf gas exchange and canopy light interception efficiency (ε<sub>i</sub>) were evaluated through a wide range of predawn leaf water potential (Ψ<sub>PD</sub>) measurements in a field experiment in Southern France. Additionally, greenhouse experiments were carried out to monitor stomatal response to increasing VPD levels. Ekigaïna showed a strong isohydric behavior with the highest decrease in leaf gas exchange in response to soil water stress and VPD. Mourvèdre and Grenache showed a similar but relatively less extreme behavior. These three cultivars showed a constant leaf water status during the day through stomatal regulation and a strong decrease in ε<sub>i</sub>. In contrast, Syrah and Marselan displayed anisohydric behavior as they presented a less sensitive stomatal control. Both cultivars showed fluctuating midday leaf water potential and Marselan was the least affected in terms of ε<sub>i</sub>.</p><p style="text-align: justify;"><strong>Conclusion</strong>: This study demonstrated that grape cultivars differed in their stomatal response to soil water deficit and VPD. For a given cultivar, a similar stomatal behavior was found in response to both Ψ<sub>PD</sub> and VPD.</p><p style="text-align: justify;"><strong>Significance and impact of the results</strong>: Adaptation to drought and viticulture viability in hot and dry environments could be achieved by identifying and breeding cultivars with drought tolerance traits.</p>

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