Evaluation of the chronic effects of ozone on biomass loss of winter wheat based on ozone flux-response relationship with dynamical flux thresholds

To evaluate the chronic negative effects of elevated ozone concentration on winter wheat in China, a parameterized Jarvis-type multiplicative stomatal conductance model with data collected from open-top chamber experiments on field grown wheat during four growing seasons in 2008-2011, were utilized to derive relationships between relative biomass and absorbed ozone phytotoxic dose (POD). The work introduced a variable flux threshold expressed as a function of gross photosynthesis rate (A), considered the detoxification ability for ozone damage on winter wheat, varying with time of day and growth stages of winter wheat. The results showed the linear relationships with the highest coefficient of determination (R2 = 0.8029) and intercept closer to 1 (value 1.0018) were obtained, between the PODY above a varied flux threshold Y and relative dry matter loss of wheat, compared with other fixed flux thresholds. The results demonstrated that the flux response relationship accounting for the photosynthetic ability can be used with confidence to assess and predict the damage effects of ozone on yields loss of crops across China.