DO3SE model applicability and O3 flux performance compared to AOT40 for an O3-sensitive tropical tree species (Psidium guajava L. ‘Paluma’)
2015
Assis, Pedro I. L. S. | Alonso, Rocío | Meirelles, Sérgio T. | Moraes, Regina M.
Phytotoxic ozone (O₃) levels have been recorded in the Metropolitan Region of São Paulo (MRSP). Flux-based critical levels for O₃ through stomata have been adopted for some northern hemisphere species, showing better accuracy than with accumulated ozone exposure above a threshold of 40 ppb (AOT40). In Brazil, critical levels for vegetation protection against O₃ adverse effects do not exist. The study aimed to investigate the applicability of O₃ deposition model (Deposition of Ozone for Stomatal Exchange (DO₃SE)) to an O₃-sensitive tropical tree species (Psidium guajava L. ‘Paluma’) under the MRSP environmental conditions, which are very unstable, and to assess the performance of O₃ flux and AOT40 in relation to O₃-induced leaf injuries. Stomatal conductance (g ₛ) parameterization for ‘Paluma’ was carried out and used to calculate different rate thresholds (from 0 to 5 nmol O₃ m⁻² projected leaf area (PLA) s⁻¹) for the phytotoxic ozone dose (POD). The model performance was assessed through the relationship between the measured and modeled g ₛₜₒ. Leaf injuries were analyzed and associated with POD and AOT40. The model performance was satisfactory and significant (R ² = 0.56; P < 0.0001; root-mean-square error (RMSE) = 116). As already expected, high AOT40 values did not result in high POD values. Although high POD values do not always account for more injuries, POD₀ showed better performance than did AOT40 and other different rate thresholds for POD. Further investigation is necessary to improve our model and also to check if there is a critical level of ozone in which leaf injuries arise. The conclusion is that the DO₃SE model for ‘Paluma’ is applicable in the MRSP as well as in temperate regions and may contribute to future directives.
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