Matter-economical roles of the evergreen foliage ofAucuba japonica,an understory shrub in the warm-temperate region of Japan

Leaf demography and productivity ofAucuba japonica, an understory shrub in the warm-temperate region, were examined and dry matter economy was analyzed to evaluate the roles of the evergreen foliage. Turnover of leaves occurred during a short period in spring. The mean leaf life span was about 2.6 years. Annual NAR (net assimilation rate) of each sample shoot was calculated from the biomass and the total dead mass estimated from scars of leaves and floral parts. The average NAR was 1.34±0.22 g·g⁻¹·yr⁻¹. The ratio of dry matter produced by leaves during their whole life span to the initial investment was 3.45±0.37. The annual NAR calculated for individual plants was negatively related to the life span of their leaves. The seasonal change in SLW (specific leaf weight) showed that the reserve material in leaves was accumulated from autumn to early spring and was consumed for the growth of new organs in the following season. The dry matter withdrawn in spring from the overwintering foliage amounted to 40% of dry mass of the new organs developed.