Effect of the climate change in the 21st century on apple cultivation in northern Tohoku

Abstract

Due to the enrichment of atmospheric CO2 concentration, the air temperature will rise by 3-6°C and the amount of snowfall will change by the end of the 21st century in northern Tohoku district of Japan. The effect of these changes to the apple cultivation at present and in the future is reviewed. Due to the temperature increase, the date of flowering will advance at the rate 0.2 days year until 2040, as is observed already at present. The advancement will continue until 2100 under RCP8.5 scenario, while it will slow down after 2040 and stop around 2080 under RCP4.5 scenario. Because the varietal difference in the flowering date will gradually increase, the insect pollination may become difficult at the end of this century. Harvesting date will advance and delay in earlyand late-maturing varieties, respectively. Thus in late-maturing varieties, fruit weight may increase depending on the extension of fruit growth period. On the contrary, fruit storability will very likely reduce, and pigmentation will get worse especially in red-skin early-maturing varieties. Moreover, the risk of sunburn damage will increase, and the risk of late frost injury is also indicated to increase by several researchers. On the other hand, we can expect the reduction of snow damage because the amount of snowfall is generally predicted to decrease in the future, although such decreasing tendency is not detected in the past 50-100 years. Considering the conspicuous midday depression of photosynthesis observed in apple trees, they are now in serious sink-limited condition possibly due to the severe fruit thinning. Therefore, the fruit yield cultivated under high CO2 concentration will hardly increase, unless we alter the strength of thinning to improve the sink capacity of the tree.