Discharge and chemistry of stream water in northern part of Hokkaido

本研究在日本北海道最北部的冬季寒冷多雪地区进行。1）北海道大学铁盐实验林的Toikanbetsu站降水的pH值在4.00-6.80之间。降雪pH值平均为4.71，降雨pH值平均为5.00。（2）7个小流域冬季流量趋于稳定，为0.3-1.8mm/d，冬季流量的变化趋势与降水量的变化趋势基本一致。2月至3月中旬，降水量和降水量取决于盆地的地质特征。在夏季干旱水位期间，由第三系泥岩组成的盆地的河水pH值为5.4-6.2，由风化的蛇纹石组成的基底的河水pH值约为8.2。在夏季干旱水位期间，该森林溪流中溶解性有机物含量很低。而在降雨过程中，大量溶解有机物从流域中渗出，有森林覆盖的流域有机物浓度高于无森林覆盖的流域。5）高寒地区的森林不仅可以通过保持积雪来防止地面冻结，6）当白色斑焦生长到一定程度时，其生长量随时间的延长而增加，但随着时间的延长，其生长量逐渐减少（Salvelinus leucomaenis）和花红点鲑（S.malma）在同一河段共存，两种红点鲑之间存在明显的资源分配。在异域种群中，每个物种主要以漂流在溪流中的陆地昆虫为食，而同域多莉瓦登则将其主要饮食转移到底栖无脊椎动物。这两个觅食的比例变化取决于流流量作为漂流食物的载体。

This research was carried out in the northermost part of Hokkaido, Japan, a cold and snowy region during winter.1) The pH of precipitation at Toikanbetsu station of Teshio Experimental Forest, Hokkaido University, was in the range of 4.00-6.80. The mean value of snowfall pH was 4.71 and that of rainfall was 5.00, respectively. At this station, the chemical composition of snowfall was affected by sea salts and the influence of SO_4 constituting from artificial origins was also obsrved from several snowfall samples.2) The winter discharge at 7 small basin became near constant, 0.3-1.8mm/day, from February to Mid-march and cleary depended on the geological charactors of the basin.3) The pHs of streamwater in the Teshio Experimental Forest during drought water-level in summer were 5.4-6.2 at the basins consisting of Tertiary mudstone and about 8.2 at the basis consisting of weathered serpentine materials.4) The content of dissolved organic materials in the streamwater of this Forest was very low during drought water-level in summer season. At rain event, however, many dissolved organic materials eloded out from the basin and the concentration of organic materials was higher at the basins with forest covers compared to that with no forest.5) Forests at windy and cold region not only prevent ground freezing by preserving snow cover, but also have the effect on scuring water resources during mid-winter.6) When white-spoted charr (Salvelinus leucomaenis) and Dolly Varden (S.malma) cohabit the same reaches, distinct resosurce partitioning occurs between the two species. In contrast to the allopatric populations where each species primarily feeds on terrestrial insects drifting in the stream, the sympatric Dolly Varden shifts its primary diets to the benthic invertbrates. The proportions on these two foragers are changed depending on stream discharge as carrier of drifting food.