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Published on: June 24, 2019
Stomatal ozone flux estimation in Mediterranean forests through sap flow analysis
Andrea Viviano1, Ryoji Tanaka2, Elena Paoletti3
1Consiglio Nazionale delle Ricerche, Istituto di Ricerca sugli Ecosistemi Terrestri, Via Madonna del Piano 10, 50019, Sesto Fiorentino (Firenze), Italy; Dipartimento di Scienze e Tecnologie Agrarie, Ambientali e Forestali, Università degli Studi di Firenze, Via delle Cascine 5, 50144, Firenze, Italy.
Tropospheric ozone (O3) harms European forests. This study found that sap-flow derived ozone flux (POD1_Sap) better predicts visible foliar injury (O3_VFI) than standard models, suggesting improved critical levels for forest protection.
Area of Science:
- Environmental Science
- Forest Ecology
- Plant Physiology
Background:
- Tropospheric ozone (O3) is a major threat to European forest health, causing visible foliar injury (O3_VFI).
- Current methods to assess O3 impact use exposure (AOT40) and flux-based indices (PODY), with PODY relying on the DO3SE stomatal model.
- On-site validation of stomatal models is needed to accurately assess O3 phytotoxicity.
Purpose of the Study:
- To compare the correlation between sap-flow derived PODY (PODY_Sap) and O3_VFI against the standard DO3SE model-derived PODY.
- To determine exposure- or flux-based critical levels (CL) for 5% O3_VFI.
- To evaluate the utility of on-site sap flow data for refining O3 flux metrics and critical levels.
Main Methods:
- Hourly O3 concentrations and environmental data were collected from four Italian forest sites (2018-2024).
- Sap flow was measured using TreeTalker devices.
- O3_VFI was assessed annually on Fagus sylvatica, Quercus cerris, and Quercus ilex.
Main Results:
- POD1_Sap showed a higher positive correlation with O3_VFI than the standard DO3SE model-derived POD1.
- A critical level (CL) for 5% O3_VFI was proposed at 37.93 mmol O3/m2 POD1 for Fagus sylvatica.
- On-site sap flow data improved the accuracy of O3 flux metrics.
Conclusions:
- Sap-flow derived stomatal conductance data offers a more accurate assessment of O3 flux impacts on forest vegetation.
- Refined O3 flux metrics using on-site data can lead to updated and more reliable critical levels for O3-VFI.
- This approach enhances the protection strategies for European forests against ozone damage.
