Concentration- and flux-based ozone dose–response relationships for five poplar clones grown in North China

Concentration- and flux-based O3 dose–response relationships were developed for poplars in China. Stomatal conductance (gs) of five poplar clones was measured to parameterize a Jarvis-type multiplicative gs model. The maximum gs and other model parameters varied between clones. The strongest relationship between stomatal O3 flux and total biomass was obtained when phytotoxic ozone dose (POD) was integrated using an uptake rate threshold of 7 nmol m−2 s−1. The R2 value was similar between flux-based and concentration-based dose–response relationships. Ozone concentrations above 28–36 nmol mol−1 contributed to reducing the biomass production of poplar. Critical levels of AOT40 (accumulated O3 exposure over 40 nmol mol−1) and POD7 in relation to 5% reduction in total biomass for poplar were 12 μmol mol−1 h and 3.8 mmol m−2, respectively. •A stomatal conductance model was calibrated for poplar clones in China.•The stomatal O3 flux–response relationship was developed for poplars.•O3 concentrations > 28–36 nmol mol−1 contributed to poplar biomass reduction.•Current ambient O3 level in most places of China has threatened poplar growth.•Ozone sensitivity of poplar is similar to that of birch/beech. For the first time, dose–response relationships were developed for risk assessment of O3 impacts on poplars in China.