## 3 Results and Discussion
### Relationships among Climate Change, Ozone Concentration and the Net Primary Productivity of Forest
According to a study by [PERSON] et al. [43], the decrease in forest productivity due to ozone in the United States has decreased by at least 3% to 16%, an average of 7.4%, in 64 sites from 1987 to 1992, and [PERSON] et al. [19] found that annual forest productivity decreased from 1987 to 1992 by 2.6 \(\pm\) 0.34%. In particular, the average concentration of ozone during the second and third quarters, when NPP is in full swing, has the greatest impact. According to these studies that ozone influences NPP production at a mean concentration of 0.04 ppm or higher [19; 43]. In fact, the concentration observed was about 0.05 ppm, indicating a concentration that influences NPP production. Damage also is expressed when contact is made between 0.06 ppm and 0.170 ppm for 4 h and between 0.200 ppm and 0.510 ppm for 1 h for susceptible species [7]. In general, it is also known that after 20 days of exposure, yield is reduced by 50% in the case of radish at 0.05 ppm per 1 day, and carnations are affected by a decrease in flowering rate and a decrease in the production of pollen. In the future, ozone concentration changes due to nitrogen oxide emissions from various scenario combinations are expected to decrease by up to between 3% and 21% when compared to current levels in the 2050s and between 29% or 36% in the 2090s (see Figure 2 in Section 2.2.3). Changes in the net primary productivity of forests due to ozone concentration change scenarios are shown in Figure 5. When average ozone concentration decreases by about 3% in the 2050s, the net primary productivity of forests increases by about 0.28%. When the average ozone concentration increases by about 21%, the productivity of the net primary productivity of forests decreases by about 1.99%. In the 2090s, when the average ozone concentration decreases by about 29%, the net primary productivity of forests increases by 2.58%, and when the ozone concentration increases by about 36%, the net primary productivity decreases by about 3.20%. Under the RCP 8.5 scenario, an increase in ozone and its impact on vegetation is simulated in Asia, where a strong decrease in NPP (1.0-1.5% per year) was simulated [15; 81; 82]. A reduction of the ozone impact on vegetation is observed in particular over the Eastern US and in Southeastern China by 2100 [15]. A study evaluated the effects of tropospheric ozone on GPP at 37 European forest sites during the time period 2000-2010 and showed, along a North-West/South-East European transect, a negative impact of ozone on GPP, ranging from 0.4% to 30% [83]. The results obtained from predicting the damage caused by ozone are different from the results of the impact assessment of climate change. The net primary productivity of forests due to climate change may increase with management or adaptation policies, but damage from ozone results in a decrease in productivity as the concentration of ozone increases. These results show that mitigation policies are important to reduce the negative impact of ozone on net primary productivity of forests. Reducing nitrogen oxide emissions and decreasing the concentration of ozone generated, thereby will also reduce the damage to forest productivity. Figure 5: Ten-year average of total net primary productivity of forests in Korea: (**a**) The net primary productivity with fixed ozone concentration; (**b**) The net primary productivity when ozone concentration increases to its maximum potential level; and, (**c**) The net primary productivity when ozone concentration decreases to its minimum potential level.