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

我们研究了流域的泥沙输送系统和河岸森林的更新过程，以提供一个在河流管理中保持生态功能的框架。泥沙产生和运移之间的时间滞后促进了河床的快速淤积和退化，从而产生了阶地侧向沉积。这些红土沉积和伴生的辫状图案在一个不受约束的河段中清楚地观察到。这段河段有次生和废弃的水道、横向沙洲和泛滥平原，为需要各种水分、基质和干扰频率的许多物种提供了再生场所。一旦裸露的场地被创造出来，树苗就被培育出来，形成了均匀的、甚至是年代久远的森林。底质和溪流地貌密切相关，可以解释高知河优势树种沿海拔梯度的分布。研究了河岸林的生态功能，特别是在遮荫和提供鱼类栖息地方面。对河岸林冠层的遮荫进行了热量收支和统计分析，并进行了比较，验证了回归分析的准确性。作为多尺度方法的基础，对鱼类生境进行了调查。这些结果表明了河岸森林的重要性，以及不同尺度之间控制鱼类丰度的因素的差异。我们重点研究了一种用巨石覆盖场地的重建方法(石块覆盖)，这种方法通过保持高土壤水分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，促进林分生长是非常有效的。

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.