Studies on the variability of the water and material cycle in the forest

本研究的目的是阐明森林盆地，特别是北方森林盆地的水、能量和物质循环的变异性。研究结果表明：北海道北部森林（稀疏混木）山地盆地存在三个主要结果。即：1)退潮期的河流温度与地表以下1.8 m处的土壤温度相似，表明地下水对河流流量的贡献来源于该深度；②固体降水占年降水量的53%，融雪径流量占年径流量的45%；3)融雪中期最可能出现对河床泥沙的补沙，新补沙对河床细粉的积极搅动形成融雪中期悬沙浓度的明显峰值。在北温带第四纪火山灰流域，即使在200mm/48h的降雨事件中，旧水对暴雨流量的贡献也超过80%。这个结果是由标准的双组分水线分离方法得到的二氧化硅浓度。高达80%的峰值径流表明，在这一事件中，新的水与土壤的转移立即发生了。为了解森林流域养分负荷的径流特征，对4个相邻流域的森林溪流进行了水质观测。对4条河流水质数据的主成分分析表明，表征森林河流水质的主要因素是表层土壤状况和河流流量变化程度。为明确寒雪区森林流域的水文特征，对近15年来托雅湖的水平衡及其流域径流进行了研究。融雪季节的径流量占流域年总流量的20% ~ 30%。这种高流量有助于在夏季保持较高的湖泊水位。少

The purpose of this study is to clarify the variability of the water, energy and material cycle in the forested basin, specially in the boreal forest basin. Our findings are summarized as follows :There are three main results in the forested (sparse mixed-wood) mountainous basin in northern Hokkaido. That is, 1) stream temperatures during the recession flow period were similar to the soil temperature at 1.8 m below the land surface, suggesting that subsurface water contributions to streamflow are derived from this depth ; 2) the solid precipitation accounted for 53% of the annual precipitation and snowmelt runoff accounted for 45% of the annual runoff ; and 3) a sediment supply to the river-bed sediment was most likely to be occurred during the mid-snowmelt season, and active stirring-up of river-bed fines from the newly supplied sediment formed the clear peak of the suspended sediment concentration in mid-snowmelt season.In a quaternary volcanic ash watershed in the northern temperate … More forest zone, the old water contributed the stormflow more than 80% even in a 200mm/48hours-rainfall event. This result was derived from the standard two-component hydrograph separation approach for the silica concentration. As much as 80% of peak runoff suggests that new water displacement with soil wa* occurred immediately during the event.To understand the runoff characteristics of the nutrient loads from the forest basin, water quality of the four forest streams whose basins are contiguous to each other was observed simultaneously. The principle component analysis of the water quality data of the four streams suggested that the main factors characterizing the water quality of the forest streams are the condition of surface soil layer and the degree of streamflow variation.To clarify the hydrological characteristics of the forest watershed in cold snowy region, the water balance of Lake Toya and the runoff from its watershed were studied for last 15 years. The stream inflow in the snowmelt season was 20 to 30% of the annual total discharge from the watershed. This high flow rate contributes to maintain the high lake water level in the summer. Less