Effects of artificial disturbance of river on the biodiversity of the river forest

为探讨河滨森林生物多样性的机制，研究了日本温带地区保存较好的河滨森林中几种优势树种的繁殖策略和交配系统。在雌雄异株树种Salix sp.中，我们揭示了有性繁殖和无性繁殖在林龄上的相对重要性。在柳属植物中，雌性在繁殖过程中投入了大量的资源，但雌性在生理、形态和物候等方面具有较好的补偿生殖成本的机制。我们还发现，江边种Jugalns ailanthifolia是一个异花异花的物种，它有两种开花物候。这两种类型对男性和女性功能的投入都是相等的。男性的繁殖成功率也几乎与女性相同。利用稳定同位素揭示了从山地河岸森林凋落物到海洋鱼类的食物链。本研究证明了保护天然河滨林对维持生物多样性的重要性。

To evaluate the mechanisms of bio-diversity of riverside forests, we investigated the reproductive strategies and mating systems of several dominant tree species in several well-preserved riverside forests in temperate region of Japan. In the dioecious tree species, Salix sp., we revealed the relative importance of sexual and asexal reproduction in relation to stand ages. In Salix sp., female invest much more resource to reproduction, but they have several superior physiological, morphological, and phenological mechanisms to compensate the reproductive cost. We also revealed that a riverside species, Jugalns ailanthifolia, is a heterodichogamous species, which have two type of flowering phenolgies. Both types invest equally to each of male and female function. Male reproductive success was also almost identical to that of females.We revealed the food chain from litter fall in mountaneous river side forest to fish in sea by using stable isotope. This study provide the evidences of importance of the preservation of natural riverside forests to maintain the bio-diversity.