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

Concentration- and flux-based O-3 dose-response relationships were developed for poplars in China. Stomatal conductance (g(s)) 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 O-3 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 R-2 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 AOT(40) (accumulated O-3 exposure over 40 nmol mol(-1)) and POD7 in relation to 5% reduction in total biomass for poplar were 12 mu mol mol(-1) h and 3.8 mmol m(-2), respectively. (C) 2015 Elsevier Ltd. All rights reserved.