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

(1)对日本中部火山富士山山地和亚高山万年青植物的生理生态学和物质经济学进行了研究，以阐明在营养有限条件下万年青植物的优势机制。(2)在火山岩床上的山地网站，森林冠层占主导地位的万年青针叶树（赤松）和下冠层占主导地位的万年青阔叶树（Irex pedunculosa，马醉木）。万年青阔叶树与落叶阔叶树在生理生态上存在差异;（1）常绿植物氮素的年周转率较低，（2）春季万年青植物叶片作为氮素的贮藏器官，氮素从叶片转移到新梢，（3）常绿植物的最大光合速率较低，但在每日物质生产方面没有差异，因为在常绿植物中没有发生光合活性的中午耗竭，（4）常绿树种的年生产力较高，主要是由于落叶树种在生长季前后的光合作用活跃。因此，常绿植物的氮素利用效率（NUE）较高。(3)熔岩床上的万年青松树叶片中储存的氮素较多，在较好的光照条件下，这些氮素被转移到新梢生长中，其氮素利用效率高于深层土壤。在亚高山的万年青草本植物中也观察到高NUE。早春，万年青叶在良好的光照条件下进行光合作用。(4)这些结果表明，常绿导致了一个保守的养分经济和高氮利用效率在凉爽和养分有限的网站。

(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.