Discharge and chemistry of stream water in northern part of Hokkaido

本研究是在日本北海道最北端冬季寒冷多雪的地区进行的。1）北海道大学天盐实验林台官别站降水pH值范围为4.00-6.80。降雪pH平均值为4.71，降雨pH平均值为5.00。在该站，降雪的化学成分受到海盐的影响，从几个降雪样品中也观察到了人工来源的SO_4的影响。2）从2月到3月中旬，7个小盆地的冬季流量几乎恒定，为0.3-1.8毫米/天，显然取决于盆地的地质特征。3）夏季干旱水位期间天盐实验林河水的pH值为由第三系泥岩组成的盆地为5.4-6.2，由风化蛇纹岩物质组成的盆地为8.2左右。4）夏季干旱水位期间，该森林溪水中溶解的有机物质含量很低。然而，在降雨时，许多溶解的有机物质从流域中流失，并且与没有森林覆盖的流域相比，有森林覆盖的流域有机物质浓度更高。 5) 多风和寒冷地区的森林不仅可以通过保留积雪来防止地面冻结，而且还具有确保仲冬水资源的作用。 6) 当白斑红点鲑 (Salvelinus leucomaenis) 和多莉瓦尔登 (S.malma) 同栖息在同一河段时，不同河段的森林会产生明显的差异。资源分配发生在两个物种之间。异域种群中每个物种主要以溪流中漂流的陆生昆虫为食，与之不同的是，同域的多莉·瓦登将其主要饮食转向底栖无脊椎动物。这两个觅食器上的比例根据作为漂流食物载体的溪流流量而变化。

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.