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The current level of tropospheric ozone (O₃) is expected to reduce the net primary production of forest trees. Here, we evaluated the negative effects of O₃ on the photosynthetic CO₂ uptake of Japanese forest trees species based on their cumulative stomatal O₃ uptake, defined as the phytotoxic O₃ dose (POD). Seedlings of four representative Japanese deciduous broad-leaved forest tree species (<i>Fagus crenata</i>, <i>Quercus serrata</i>, <i>Quercus mongolica</i> var. <i>crispula</i> and <i>Betula platyphylla</i> var. <i>japonica</i>) were exposed to different O₃ concentrations in open-top chambers for two growing seasons. The photosynthesis&#8722;light response curves (<i>A</i>-light curves) and stomatal conductance were measured to estimate the leaf-level cumulative photosynthetic CO₂ uptake (&#931;<i>P</i>_{n_est}) and POD, respectively. The whole-plant-level &#931;<i>P</i>_{n_est} were highly correlated with the whole-plant dry mass increments over the two growing seasons. Because whole-plant growth is largely determined by the amount of leaf area per plant and net photosynthetic rate per leaf area, this result suggests that leaf-level &#931;<i>P</i>_{n_est}, which was estimated from the monthly <i>A</i>-light curves and hourly PPFD, could reflect the cumulative photosynthetic CO₂ uptake of the seedlings per unit leaf area. Although the O₃-induced reductions in the leaf-level &#931;<i>P</i>_{n_est} were well explained by POD in all four tree species, species-specific responses of leaf-level &#931;<i>P</i>_{n_est} to POD were observed. In addition, the flux threshold appropriate for the linear regression of the responses of relative leaf-level &#931;<i>P</i>_{n_est} to POD was also species-specific. Therefore, species-specific responses of cumulative photosynthetic CO₂ uptake to POD could be used to accurately evaluate O₃ impact on the net primary production of deciduous broad-leaved trees.