Ozone stomatal flux and O3 concentration-based metrics for Astronium graveolens Jacq., a Brazilian native forest tree species.

The current levels of surface ozone (O-3) are high enough to negatively affect trees in large regions of Sao Paulo State, southeastern Brazil, where standards for the protection of vegetation against the adverse effects of O-3 do not exist. We evaluated three O-3 metrics - phytotoxic ozone dose (POD), accumulated ozone exposure over the threshold of 40 ppb h (AOT40), and the sum of all hourly average concentrations (SUM00) - for the Brazilian native tropical tree species Astronium graveolens Jacq. We used the DO3SE (Deposition of Ozone for Stomatal Exchange) model and calculated PODY for different thresholds (from 0 to 6 mmol O-3 m(-2) PLA s(-1)), evaluating the model's performance through the relationship between measured and modelled conductance. The response parameters were: visible foliar injury, considered as incidence (% injured plants), severity (% injured leaves in relation to the number of leaves on injured plants), and leaf abscission. The model performance was suitable and significant (R-2 = 0.58; p < 0.001). PODO was better correlated to incidence and leaf abscission, and SUM00 was better correlated to severity. The highest values of O-3 concentration-based metrics (AOT40 and SUM00) did not coincide with those of PODO. Further investigation may improve the model and contribute to the proposition of a national standard for the protection of native species. (C) 2016 Elsevier Ltd. All rights reserved.