Study on effects of forest types on river-water quantity and quality in mountainous regions

本项目的目的是阐明森林类型对山区河流水质和水量的影响。在塔玛山和关东山区不同森林类型的几个小流域进行了水文和水文地球化学观测。研究了土壤化学和土壤性质在水文条件下的变化规律，建立了流域尺度的准物理径流模型，反映了森林流域土壤特性的异质性。利用该模型研究了森林覆盖对径流特征的影响。模型较好地模拟了观测结果，表明径流特征的差异来自于不同森林类型引起的土壤性质的差异，如土壤深度、土壤持水曲线等。利用稳定同位素对森林流域氮素循环进行了研究。

The purpose of this project is to clarify the effects of forest types on river-water quality and quantity in mountainous regions. Hydrological and hydrogeochemical observations were carried out on several small watersheds in Tama hill and Kanto mountain with various types of forests. Soil chemistry and soil property on hydrological conditions were investigated.A quasi-physical runoff model for catchment-scale was developed, representing heterogeneity of soil characteristics in forested catchments. The effects of forest cover on runoff characteristics were investigated by using the model. The model performed well the observation results, suggesting that the differences of runoff characteristics come from the differences of soil properties, such as soil depth and water retention curve, caused by forest types.Processes of changes in water chemistry were investigated. Nitrogen Cycle in forested watersheds were focused on by using stable isotopes.