Developments of principles and methods to keep ecological functions of riparian forests

我们研究了流域的泥沙运移系统和河岸林的更新过程，以提出一个框架，保持生态功能的河流管理。沉积物的产生和运输之间的时间差促进河床的快速加积和退化，导致形成阶状横向沉积。在一个无约束河段中，可以清楚地观察到这些侧向沉积和相关的辫状沉积样式。该河段有次级和废弃的河道、侧坝和洪泛区，为许多需要各种水分、基质和干扰频率的物种提供了再生场所。一旦裸露的地方被创造出来，树苗就被建立起来，从而形成了均匀的、年龄均匀的森林。底质与河流地貌密切相关，可以解释十胜川优势树种沿着海拔梯度的分布。用热量收支法和统计分析法检验了河岸林树冠的遮荫作用，并将两者进行了比较，以验证回归分析的准确性。鱼类栖息地的调查作为多尺度方法的基础。这些结果表明，河岸林的重要性，以及不同尺度的鱼类丰度控制因素的差异。我们重点研究了一种用巨石覆盖场地的重新植被方法（石头覆盖），这种方法通过保持高土壤湿度和低土壤温度来改善场地条件。结果表明，该方法对缓解干旱胁迫和促进芦笋生长十分有效。

We examined sediment routing system in a basin and regeneration process of riparian forests in order to present a framework for keeping ecological functions in stream management. A time lag between sediment production and transport promotes rapid aggradation and degradation of a streambed, resulting in creating terraced lateral deposits. These laterl deposits and associated braided pattern are clearly observed in a unconstrained reach. This reach has secondary and abandoned channels, lateral bars and floodplains, which provide regeneration sites for many species requiring a variety of moisture, substrate, and disturbance frequency. Once bare sites are created, tree seedlings are wstablished, resulting in uniformeed-, even-aged forests. Yhe substrate and stream landforms are closely correlated and we could explain the distribution of dominant tree species along the elevation gradient in the Tokachi River.The ecological functions of riparian forests were examined especially on shading and providing fish habitat. The shading by riparian forest crown was examined by heat-budgets and by statistical analysis, and them compared to verify the accuracy of regression analysis. The fish habitat ws investigated as a basis of multi-scale approach. These results indicated the importance of riparian forest, and difference in factors controlling fish abundance between scales. We focused on a revegetation method covering the site with boulders (stone-mulching), which improve site conditions by keeping soil moisture high and soil temperature low. The results proved that this method is very effective to improve dry stress and promotes an increase in growth of reparian trees.