Changes in properties of epicuticular wax and the related water loss in Japanese cedar (Cryptomeria japonica) affected by anthropogenic environmental factors

The leaves of Cryptomeria japonica D. Don collected near an electrochemical plant (on Yakushima Island) had more wax (approximately 10% higher in 1-year leaves) and less chlorophyll (approximately 50 and 30% lower in 0- and 1-year leaves, respectively) than those from a reference area, although the trees showed no symptoms of decline. In the Kanto Plain around Tokyo (Saitama and Ibaraki), where C. japonica is declining (dieback and (or) defoliation), the amount of epicuticular wax in current-year leaves and the leaf chlorophyll content were almost equivalent to those of healthy plants in mountainous areas, but the wax eroded more rapidly (approximately 1.5 times faster). Although the C and O contents and the C/O ratio of epicuticular wax were approximately equivalent irrespective of the levels of decline, the cuticular transpiration rate, especially in 1-year leaves, was higher in Saitama (water loss: 0.92 +/- 0.21%/h) and to some extent in Ibaraki (0.66 +/- 0.08%/h) than in the mountainous area (0.60 +/- 0.12%/h). This excessive transpiration, probably resulting from a degraded wax layer and the partial malfunctioning of stomata due to deposited aerosols, may be a significant factor causing the decline of C.japonica. Dry atmospheric conditions (e.g., rain factor <100), which have prevailed since the 1950s due to urbanization, may have inflicted additional stress on the tree.