scholarly journals Novel applications of carbon isotopes in atmospheric CO<sub>2</sub>: what can atmospheric measurements teach us about processes in the biosphere?

2011 ◽  
Vol 8 (3) ◽  
pp. 4603-4631 ◽  
Author(s):  
A. P. Ballantyne ◽  
J. B. Miller ◽  
I. T. Baker ◽  
P. P. Tans ◽  
J. W. C. White
Keyword(s):  
Stomatal Conductance ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Carbon Isotopes ◽  
Vapor Pressure Deficit ◽  
Global Analysis ◽  
Global Scale ◽  
Atmospheric Measurements ◽  
Ocean Carbon ◽  
Analytical Approaches

Abstract. Conventionally, measurements of carbon isotopes in atmospheric CO2 (δ13CO2) have been used to partition fluxes between terrestrial and ocean carbon pools. However, novel analytical approaches combined with an increase in the spatial extent and frequency of δ13CO2 measurements allow us to conduct a global analysis of δ13CO2 variability to infer the isotopic composition of source CO2 to the atmosphere (δs). This global analysis yields coherent seasonal patterns of isotopic enrichment. Our results indicate that seasonal values of δs are more highly correlated with vapor pressure deficit (r=0.404) than relative humidity (r=0.149). We then evaluate two widely used stomatal conductance models and determine that Leuning Model, which is primarily driven by vapor pressure deficit is more effective globally at predicting δs (RMSE = 1.7 ‰) than the Ball-Berry model, which is driven by relative humidity (RMSE = 2.8) ‰. Thus stomatal conductance on a global scale may be more sensitive to changes in vapor pressure deficit than relative humidity. This approach highlights a new application of using δ13CO2 measurements to test global models.

scholarly journals Novel applications of carbon isotopes in atmospheric CO<sub>2</sub>: what can atmospheric measurements teach us about processes in the biosphere?

2011 ◽  
Vol 8 (10) ◽  
pp. 3093-3106 ◽  
Author(s):  
A. P. Ballantyne ◽  
J. B. Miller ◽  
I. T. Baker ◽  
P. P. Tans ◽  
J. W. C. White
Keyword(s):  
Stomatal Conductance ◽  
Relative Humidity ◽  
Vapor Pressure ◽  
Carbon Isotopes ◽  
Vapor Pressure Deficit ◽  
Global Analysis ◽  
Global Scale ◽  
Atmospheric Measurements ◽  
Ocean Carbon ◽  
Analytical Approaches

Abstract. Conventionally, measurements of carbon isotopes in atmospheric CO2 (δ13CO2) have been used to partition fluxes between terrestrial and ocean carbon pools. However, novel analytical approaches combined with an increase in the spatial extent and frequency of δ13CO2 measurements allow us to conduct a global analysis of δ13CO2 variability to infer the isotopic composition of source CO2 to the atmosphere (δs). This global analysis yields coherent seasonal patterns of isotopic enrichment. Our results indicate that seasonal values of δs are more highly correlated with vapor pressure deficit (r = 0.404) than relative humidity (r = 0.149). We then evaluate two widely used stomatal conductance models and determine that the Leuning Model, which is primarily driven by vapor pressure deficit is more effective globally at predicting δs (RMSE = 1.6‰) than the Ball-Woodrow-Berry model, which is driven by relative humidity (RMSE = 2.7‰). Thus stomatal conductance on a global scale may be more sensitive to changes in vapor pressure deficit than relative humidity. This approach highlights a new application of using δ13CO2 measurements to validate global models.

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.

Effect of Mycorrhizal Fungi on Gas Exchange of Micropropagated Guava Plantlets (Psidium guajava L.) during Acclimatization and Plant Establishment

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 501c-501
Author(s):  
Andrés A. Estrada-Luna ◽  
Jonathan N. Egilla ◽  
Fred T. Davies
Keyword(s):  
Tissue Culture ◽  
Stomatal Conductance ◽  
Gas Exchange ◽  
Vapor Pressure ◽  
Mycorrhizal Fungi ◽  
Vapor Pressure Deficit ◽  
Psidium Guajava ◽  
Glomus Etunicatum ◽  
Plant Establishment ◽  
Use Efficiency

The effect of mycorrhizal fungi on gas exchange of micropropagated guava plantlets (Psidium guajava L.) during acclimatization and plant establishment was determined. Guava plantlets (Psidium guajava L. cv. `Media China') were asexually propagated through tissue culture and acclimatized in a glasshouse for eighteen weeks. Half of the plantlets were inoculated with ZAC-19, which is a mixed isolate containing Glomus etunicatum and an unknown Glomus spp. Plantlets were fertilized with modified Long Ashton nutrient solution containing 11 (g P/ml. Gas exchange measurements included photosynthetic rate (A), stomatal conductance (gs), internal CO2 concentration (Ci), transpiration rate (E), water use efficiency (WUE), and vapor pressure deficit (VPD). Measurements were taken at 2, 4, 8 and 18 weeks after inoculation using a LI-6200 portable photosynthesis system (LI-COR Inc. Lincoln, Neb., USA). Two weeks after inoculation, noninoculated plantlets had greater A compared to mycorrhizal plantlets. However, 4 and 8 weeks after inoculation, mycorrhizal plantlets had greater A, gs, Ci and WUE. At the end of the experiment gas exchange was comparable between noninoculated and mycorrhizal plantlets.

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.

Response of Stomatal Conductance to Vapor Pressure Deficit in Leaves of Four Trees at the Campus of Shandong University

2014 ◽  
Vol 522-524 ◽  
pp. 1055-1058
Author(s):  
Jing Li ◽  
Xiao Guang Wang ◽  
Gui Zhai Zhang ◽  
Xue Wei Hou ◽  
Xiao Ming Li
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Vapor Pressure ◽  
Vapor Pressure Deficit ◽  
Response Pattern ◽  
Populus Deltoides ◽  
Shandong Province ◽  
Populus Euramericana ◽  
Parabolic Curve

Response of gas exchange to VPD in leaves of four trees (Prunus serrulata, Prunus lannesiana, Populus deltoides I-69 (I-69) and Populus × euramericana Neva (I-107)) at the campus of Shandong University in Jinan, Shandong Province were measured. The result showed that: the stomatal conductance increased with increasing VPD, and gs reached gs-max at intermediate VPD, and a steady decline in gs with further increases in VPD. This response pattern was fitted by a parabolic curve (gs=aD2+bD+c, D=VPD, R2>0.52). The gs-max at intermediate VPD with changing VPD showed that there was an optimal VPD (or RH) to plants. Therefore, while VPD (or RH) was higher or lower than the optimal VPD (or RH) of plant, gs would decrease. The response of gs to VPD in I-69 and I-107 were much more sensitive than P. serrulata and P. lannesiana.

Near stream groundwater table fluctuations impact transpiration rates of riparian plants: a field study with stomatal conductance and dendrometry measurements

2021 ◽  
Author(s):  
Stefano Martinetti ◽  
Simone Fatichi ◽  
Marius Floriancic ◽  
Paolo Burlando ◽  
Peter Molnar
Keyword(s):  
Stomatal Conductance ◽  
Vapor Pressure ◽  
Water Table ◽  
Vapor Pressure Deficit ◽  
Growing Season ◽  
Groundwater Table ◽  
Short Term ◽  
Riparian Plants ◽  
Gravel Bed ◽  
Riparian Trees

&lt;p&gt;Vegetation establishment, growth, and succession in riparian ecosystems are linked to river and groundwater dynamics. This is especially true in Alpine gravel-bed rivers with wide floodplains and a strong river-aquifer exchange. Here we provide data evidence of riparian plant response to short-term groundwater table fluctuations in a braided gravel-bed river (Maggia). We used indirect physiological variables for photosynthesis and transpiration &amp;#8211; stomatal conductance g&lt;sub&gt;s&lt;/sub&gt; and daily variation in stem diameter &amp;#916;D&lt;sub&gt;d&lt;/sub&gt; &amp;#8211; which we measured at six mature riparian trees of the Salicaceae family, one Populus nigra and one Alnus incana specimen at two sites during two growing seasons. The site where g&lt;sub&gt;s&lt;/sub&gt; measurements were conducted showed a greater depth to groundwater with higher variability compared to the site were dendrometers were placed.&lt;/p&gt;&lt;p&gt;We analysed the data by means of two different random forest regression algorithms for the two study sites. One with the transpiration-induced daily tree diameter drop during the growing season 2017 as the dependent variable, and one with the raw g&lt;sub&gt;s&lt;/sub&gt; measurement sequence, obtained on 10 days throughout the growing season 2019, as the dependent variable. In both algorithms the independent variables consisted of meteorological measures (locally measured and at valley scale) and of groundwater and river stages near the individual plants. We also separated the g&lt;sub&gt;s&lt;/sub&gt; measurements into low and high groundwater stage conditions observed during the g&lt;sub&gt;s&lt;/sub&gt; field campaign and applied traditional regression analysis of g&lt;sub&gt;s &lt;/sub&gt;on vapor pressure deficit VPD and global radiation r&lt;sub&gt;g&lt;/sub&gt; for the 2 groundwater stage conditions separately.&lt;/p&gt;&lt;p&gt;The data analyses demonstrate that:&lt;/p&gt;&lt;p&gt;(a) short-term variation of the groundwater table affects riparian vegetation: at the site with deeper groundwater, the water table depth was the best predictor of g&lt;sub&gt;s&lt;/sub&gt; variability, while at the site with shallower groundwater, temperature and vapor pressure deficit were the best predictors of &amp;#916;D&lt;sub&gt;d&lt;/sub&gt;&amp;#160; variability;&lt;/p&gt;&lt;p&gt;(b) instantaneous stomatal conductance is related to vapor pressure deficit (VPD), but conditioned by groundwater levels, with higher stomatal conductance for the same radiative input and VPD when the water table was higher.&lt;/p&gt;&lt;p&gt;(c) local micro-climate measured at tree locations had a stronger predictive power for g&lt;sub&gt;s&lt;/sub&gt; than valley scale climate, suggesting local climate may be an important control on vegetated stands on gravel bars.&lt;/p&gt;&lt;p&gt;Even though the considered plants are located in close proximity to the river and could be considered to be unaffected by water stress, our analysis provides evidence of riparian trees undertaking physiological adjustments to transpiration in response to groundwater stage, depending on their riparian floodplain settings. In the heavily regulated Maggia river this has implications on the minimum flow release by dams, as prolonged periods of low water stage in the river will lead to a decrease in groundwater stage, and subsequently in reduced growth of phreatophytic riparian plants on the floodplain. We argue such plant-scale measurements should be helpful for the optimisation of flow release levels in regulated riparian systems.&lt;/p&gt;

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