Tropospheric O-3 is a strong oxidant that may affect vegetation and human health. Here we report on the O-3 fluxes from a poplar plantation in Belgium during one year. Surprisingly, the winter and autumn O-3 fluxes were of similar magnitude to ones observed during most of the peak vegetation development. Largest O-3 uptakes were recorded at the beginning of the growing season in correspondence to a minimum stomatal uptake. Wind speed was the most important control and explained 44% of the variability in the nighttime O-3 fluxes, suggesting that turbulent mixing and the mechanical destruction of O-3 played a substantial role in the O-3 fluxes. The stomatal O-3 uptake accounted for a seasonal average of 59% of the total O-3 uptake. Multiple regression and partial correlation analyses showed that net ecosystem exchange was not affected by the stomatal O-3 uptake. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.