## 3 Results  
Figure 3 shows the spatial distribution of 5-year mean annual COU per unit leaf area of _F. crenta_, _Q. serrata_, _Q. mongolica_ var. _ crispula_, and _B. platuyphylla_ var. _japonica_ in Japan in 2011-2015. The annual COU in each year is indicated in Figure 4. The 5-year mean COU averaged across Japan differed  
Figure 2: Responses of annual CO\({}_{2}\) uptake per unit leaf area to cumulative stomatal O\({}_{3}\) uptake (COU) of _F. crenta_, _Q. serrata_, _Q. mongolica_ var. _ crispula_, and _B. platuyphylla_ var. _japonica_ seedlings. These responses were obtained from the study by [PERSON] et al. [18] with slight modifications. The Y-intercept was modified to 100 in the present study. Plots indicate the first-flush or early leaves (\(\Circle\)) or second-flush or late leaves (\(\times\)). The Weibull function was fitted to the response, and its parameters, \(\omega\) and \(\lambda\), and the mean absolute error (MAE, %) are indicated in each figure.  
between the tree species, being 41.7 (2011-2015 range: 37.2-46.2), 26.5 (24.1-27.9), 33.0 (29.7-34.9), and 29.1 (27.8-30.6) mmol m\({}^{-2}\) in the leaves of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platyphylla_ var. _japonica_, respectively. COU was relatively low in the Tohoku and Hokkaido regions, and relatively high in Kanto, Chubu, Kinki, and Chugoku regions relative to the other regions.  
Figure 3: Spatial distribution of 5-year mean annual cumulative stomatal O\({}_{3}\) uptake (COU) per unit leaf area (mmol m\({}^{-2}\)) of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platyphylla_ var. _japonica_ in 2011–2015.  
Figure 5 shows the spatial distribution of the 5-year mean O\({}_{3}\)-induced reduction in annual CO\({}_{2}\) uptake per unit leaf area of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platphylylla_ var. _japonica_ in Japan in 2011-2015. The O\({}_{3}\)-induced reduction in annual CO\({}_{2}\) uptake each year is shown in Figure 6. The 5-year mean O\({}_{3}\)-induced reduction in CO\({}_{2}\) uptake averaged across Japan differed between the tree species, being 14.0% (2011-2015 range: 9.5-18.7%), 10.6% (7.3-12.1%), 8.6% (6.2-10.0%), and 15.4% (14.2-16.7%) in the leaves of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platphylylla_ var. _japonica_, respectively.  
Figure 7 demonstrates the impact of O\({}_{3}\) mitigation on the annual CO\({}_{2}\) uptake per unit leaf area of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platphylylla_ var. _japonica_ in 2011-2015. A curvilinear response of the reduction in the surface O\({}_{3}\) concentration to the O\({}_{3}\)-induced reduction in the annual CO\({}_{2}\) uptake was observed in the four tree species. To diminish the O\({}_{3}\)-induced reduction in the annual CO\({}_{2}\) uptake to a value of 5%, the surface O\({}_{3}\) concentrations should be reduced by 28% (2011-2015 range: 19-34%), 20% (11-23%), 17% (8-21%), and 49% (46-51%) for _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platphylylla_ var. _japonica_, respectively.  
Figure 4: Annual cumulative stomatal O\({}_{3}\) uptake (COU) per unit leaf area (mmol m\({}^{-2}\)) of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. platphylylla_ var. _japonica_ in 2011–2015. Horizontal solid lines show the median, boxes show the first through third interquartile ranges, and whiskers show the minimum and maximum COU.  
Figure 5: Spatial distribution of 5-year mean O\({}_{3}\)-induced reduction in annual CO\({}_{2}\) uptake per unit leaf area (%) of _F. crenata_, _Q. serrata_, _Q. mongolica_ var. _crispula_, and _B. plattyphyllla_ var. _japonica_ in 2011–2015.