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

本研究的目的是阐明森林流域特别是北方森林流域水分、能量和物质循环的变异性。我们的研究结果总结如下：北海道北部森林(稀疏混交林)山地盆地有三个主要结果。即：(1)退水期的水温与地表以下1.8m处的土壤温度相似，表明地下水对径流的贡献来自于该深度：(2)固体降水占年降水量的53%，融雪径流占年径流的45%；(3)融雪中期最有可能发生泥沙补给，新提供的泥沙对河床微粉的活跃搅动形成融雪期中期明显的悬沙浓度峰值。在北温带…第四纪火山灰分水岭更多的森林地带，即使在200 mm/48小时的降雨事件中，旧水对暴雨的贡献率也超过80%。这一结果是由标准的二氧化硅浓度双组分线分离方法得出的。高达80%的峰值径流表明，新的水分随土壤发生了置换。为了了解森林流域养分负荷的径流特征，我们同时观测了4条相互毗连的森林溪流的水质。对4条河流水质数据的主成分分析表明，表层土层状况和径流变化程度是表征森林溪流水质的主要因素。为了阐明寒冷雪区森林流域的水文特征，对托雅湖流域的水量平衡及其流域径流进行了近15年的研究。融雪季节的径流流量占流域年总流量的20%~30%。这一高流量有助于在夏季保持较高的湖泊水位。较少

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