Studies on life patterns of evergreen broad-leaved trees growing in cool and nutrient-limited sites

点击翻译按钮获取中文摘要

(1) Ecophysiology and matter economy were investigated for evergreen plants in montane and subalpine sites in Mt Fuji, a volcanic mountain in central Japan, to clarify the mechanism of dominance of evergreen plants under nutrient-limited conditions.(2) On a lava bed in the montane site, forest canopy is dominated by an evergreen conifer (Pinus densiflora) and under-canopy layer is dominated by evergreen broadleaf trees (Irex pedunculosa, Pieris japonica). Evergreen broadleaf trees were different from deciduous ones in several ecophysiological features; (1) Annual turnover rate of nitrogen of evergreens was lower, (2) Evergreen leaves served as storage organs and nitrogen was retranslocated from the leaves to growing shoots in spring, (3) Maximum photosynthetic rate of evergreens was lower, but there were no difference in daily matter production because midday depletion of photosynthetic activity did not occur in evergreens, (4) Annual productivity of evergreens was higher because of photosynthetic activity before and after growing season for deciduous trees. Consequently nitrogen use efficiency (NUE) of evergreens was higher.(3) The evergreen pine tree on the lava bed had much storage nitrogen in leaves, which was retranslocated to shoots growing under more favorable light condition, and had higher NUE than that on a deep soil. High NUE was also observed in an evergreen herb in the subalpine site. Evergreen leaves served to photosynthesize under a favorable light condition in early spring.(4) These results indicated that evergreenness caused a conservative nutrient economy and high NUE in cool and nutrient-limited sites.