scholarly journals Long-term fluxes of carbonyl sulfide and their seasonality and interannual variability in a boreal forest

2021 ◽  
Author(s):  
Timo Vesala ◽  
Kukka-Maaria Kohonen ◽  
Arnaud P. Praplan ◽  
Linda M. J. Kooijmans ◽  
Lenka Foltýnová ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Interannual Variability ◽  
Air Temperature ◽  
Vapor Pressure Deficit ◽  
Water Vapor Pressure ◽  
Carbonyl Sulfide ◽  
Area Index ◽  
Net Uptake ◽  
Water Vapor Pressure Deficit

Abstract. The seasonality and interannual variability of terrestrial carbonyl sulfide (COS) flux are poorly constrained. We present the first easy-to-use parameterization for net COS forest sink based on the longest eddy covariance record from a boreal pine forest, covering 32 months over 5 years. Fluxes from hourly to yearly scales are reported, with the aim of revealing controlling factors and the level of interannual variability. The parameterization is based on the photosynthetically active radiation, vapor pressure deficit, air temperature, and leaf area index. The spring recovery of the flux after the winter dormancy period was mostly governed by air temperature, and the onset of the uptake varied by 2 weeks. For the first time, we report a significant reduction of ecosystem-scale COS flux under large water vapor pressure deficit in summer. The maximum monthly and weekly median COS uptake varied 26 and 20 % between years, respectively. The timing of the latter varied by 6 weeks. The fraction of the nocturnal uptake remained below 21 % of the total COS uptake. We observed the growing season (April–August) average net uptake of COS totaling −58.0 gS ha−1 with 37 % interannual variability. The long-term flux observations were scaled up to evergreen needleleaf forests (ENFs) in the whole boreal region by the Simple Biosphere Model Version 4 (SiB4). The observations were reparameterized by using SiB4 meteorological drivers and phenology. The total COS uptake by boreal ENF was in line with a missing COS sink at high latitudes pointed out in earlier studies.

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

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