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Ozone uptake modelling and flux-response relationships—an assessment of ozone-induced yield loss in spring wheat
AbstractMeasurements of stomatal conductance on field grown spring wheat (Triticum aestivum L.) from two experiments conducted in southwest Sweden were combined to validate and adjust the Jarvis type of multiplicative stomatal conductance model presented by Emberson et al. (Environ. Pollut. 109 (2000) 403). The adjusted model (Östad model) and the Emberson model are based on the boundary line technique. The aging of the flag leaf became important for stomatal conductance at about 500 degrees days after anthesis, on average 30 days after anthesis. Elevated ozone concentrations were assumed to influence the stomatal conductance in relation to the effect on the leaf life span. During the hours after noon the stomata tended to close to an extent that could not be explained by the combined effects of leaf temperature, leaf-to-air vapour pressure difference (VPDLA) or solar radiation. For these reasons factors describing the reduction of stomatal conductance caused by ozone and time of day were introduced in the calibration of the Östad stomatal conductance model. VPDLA induced closure of stomata at ≈1.5kPa. In elevated carbon dioxide concentration (680μmolmol−1) the stomatal conductance was reduced by approximately 60%. Test with the data from Östad showed that the Östad multiplicative model had an r2-value of 0.59 for the relationship between calculated and observed conductance. The Östad as well as the Emberson models were used to estimate the cumulated uptake of ozone (CUO) by the wheat flag leaves. The relationship between CUO based on the Östad model cumulated from anthesis to harvest, with a threshold for the uptake rate of 5nmolm−2s−1 and relative yield loss, resulted in a higher r2-value (0.90) than any other CUO model or relationships based on the accumulated ozone exposure over 40nmolmol−1 (AOT40). The corresponding relationships between relative yield and CUO based on the Emberson model and with AOT40 were however also statistically significant.
Ozone uptake modelling and flux-response relationships—an assessment of ozone-induced yield loss in spring wheat
AbstractMeasurements of stomatal conductance on field grown spring wheat (Triticum aestivum L.) from two experiments conducted in southwest Sweden were combined to validate and adjust the Jarvis type of multiplicative stomatal conductance model presented by Emberson et al. (Environ. Pollut. 109 (2000) 403). The adjusted model (Östad model) and the Emberson model are based on the boundary line technique. The aging of the flag leaf became important for stomatal conductance at about 500 degrees days after anthesis, on average 30 days after anthesis. Elevated ozone concentrations were assumed to influence the stomatal conductance in relation to the effect on the leaf life span. During the hours after noon the stomata tended to close to an extent that could not be explained by the combined effects of leaf temperature, leaf-to-air vapour pressure difference (VPDLA) or solar radiation. For these reasons factors describing the reduction of stomatal conductance caused by ozone and time of day were introduced in the calibration of the Östad stomatal conductance model. VPDLA induced closure of stomata at ≈1.5kPa. In elevated carbon dioxide concentration (680μmolmol−1) the stomatal conductance was reduced by approximately 60%. Test with the data from Östad showed that the Östad multiplicative model had an r2-value of 0.59 for the relationship between calculated and observed conductance. The Östad as well as the Emberson models were used to estimate the cumulated uptake of ozone (CUO) by the wheat flag leaves. The relationship between CUO based on the Östad model cumulated from anthesis to harvest, with a threshold for the uptake rate of 5nmolm−2s−1 and relative yield loss, resulted in a higher r2-value (0.90) than any other CUO model or relationships based on the accumulated ozone exposure over 40nmolmol−1 (AOT40). The corresponding relationships between relative yield and CUO based on the Emberson model and with AOT40 were however also statistically significant.
Ozone uptake modelling and flux-response relationships—an assessment of ozone-induced yield loss in spring wheat
Danielsson, Helena (author) / Karlsson, Gunilla Pihl (author) / Karlsson, Per Erik (author) / Håkan Pleijel, H. (author)
Atmospheric Environment ; 37 ; 475-485
2002-10-30
11 pages
Article (Journal)
Electronic Resource
English
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