Seasonal ozone uptake by a warm-temperate mixed deciduous and evergreen broadleaf forest in western Japan estimated by the Penman-Monteith approach combined with a photosynthesis-dependent stomatal model

Canopy-level stomatal conductance over a warm-temperate mixed deciduous and evergreen broadleaf forest in Japan was estimated by the Penman-Monteith approach, as compensated by a semi-empirical photosynthesis-dependent stomatal model, where photosynthesis, relative humidity, and CO2 concentration were assumed to regulate stomatal conductance. This approach, using eddy covariance data and routine meteorological observations at a flux tower site, permits the continuous estimation of canopy-level O-3 uptake, even when the Penman-Monteith approach is unavailable (i.e. in case of direct evaporation from soil or wet leaves). Distortion was observed between the AOT40 exposure index and O-3 uptake through stomata, as AOT40 peaked in April, but with O-3 uptake occurring in July. Thus, leaf pre-maturation in the predominant deciduous broadleaf tree species (Quercus serrata) might suppress O-3 uptake in springtime, even when the highest O-3 concentrations were observed. (C) 2013 Elsevier Ltd. All rights reserved.