The Potential Effect of Climate Change on the Transpiration of Sugi (Cryptomeria japonica D. Don) Plantations in Japan.

Sugi (Cryptomeria japonica D. Don) trees, the most popular plantation species in Japan, are known to be sensitive to water stress. The effect of rising temperatures caused by global warming results in increases in water consumption, which in turn could have an adverse effect on sugi growth in some areas of Japan. For each grid cell at 5’N7.5’E resolution in Japan, the amounts of transpiration in hypothetical sugi stands were calculated from mesh climatic data based on needle gas exchange characteristics. Annual transpiration, which ranged from 450 to 750mm, was almost linearly related to mean annual temperature. The ratio of transpiration to precipitation (Tr/P ratio) was higher in the lowlands of the Setouchi and Kanto districts, where a decline in sugi trees has been observed. When estimations were made for a 3C increase in temperature, transpiration increased by 8 to 18%. Assuming that precipitation levels are constant, those areas with a high Tr/P ratio, like the Setouchi and Kanto districts, were seen to expand, especially in northeastern Honshu. These results suggest that global warming will have adverse effects on sugi growth in areas where precipitation is relatively low.