Biogeochemical Dynamics in Forested Watershed during Winter

在日本中部的富町进行了冬季降水的化学研究。冬季降水样品中Cl^-/Na^+和Mg^<2+>/Na^+的比值与海水的比值基本相等。说明冬季降水中的Na^+、Mg^+和Cl^-来源于海水。确定了冬季降水样品中Na^+浓度与对流混合层高度之间的关系。据信，含有海盐颗粒的云滴在降雨过程中被雪晶捕获。结果表明：对流混合层高度越高，雪晶收集海盐颗粒的速率越大；在几种产生冬季降水的天气条件下，确定了冬季降水中的δ ^<18>O值与对流混合层顶部气温的关系。在相同温度下，冬季季风条件下的降水比其他天气条件下的降水要大。在冬季季风条件下，对流混合层顶部的温度与冬季降水样本的δ ^<18>有很好的关系。研究了开放样地、落叶样地和针叶林样地积雪中阴离子浓度和生物活性的变化。针叶林样地积雪中主要阴离子的浓度高于开阔样地和落叶样地。随着融雪的进行，主要阴离子的浓度逐渐降低。积雪中PO_3^<3->的浓度随着融雪的进行而增加。针叶林样地积雪中叶绿素a的浓度高于开放样地和落叶林样地。在融雪季节，落叶林和针叶林样地积雪中叶绿素a浓度均呈上升趋势。雪藻在融雪季节活动较为活跃。通过培养实验，推测针叶林样地的NO_3^-可能被雪藻消耗。通过培养实验估计，Scenedesmus从积雪中消耗的氮为220毫克/升。对福岛县Aidzu-Tajima小森林流域的溪水进行了化学研究。实验流域位于温带多雪气候下，面积为0.14 km^2。该分水岭的基岩由新近纪形成的固结沉积物组成。这个分水岭完全被森林植被覆盖。月降水量在夏季最大；然而，最大的月径流记录在融雪季节。在融雪季节，水体中HCO_3^-浓度被融雪水稀释，Cl^-、NO_3^-和SO_4^<2->浓度呈阶段性增加。在融雪季节，溪流的pH值比夏季和秋季低。溪水的离子组成随季节而变化。夏季阴离子以碳酸氢盐为主，在融雪季节Cl^-+NO_3^-+SO_4^<2->的比值增大。少

A chemical study of the winter precipitation was conducted in Tohkamachi, central Japan. The ratios of Cl^-/Na^+ and Mg^<2+>/Na^+ found in the winter precipitation samples were nearly equal to those of sea water. This result suggests that Na^+, Mg^+, and Cl^- found in the winter precipitation are originated from sea water. A relationship was determined between the Na^+ concentration in the winter precipitation sample and the height of the convective mixing layr. Cloud droplets containing sea salt particles are believed to be captured by snow crystals through the rain-out process. The results indicate that the higher the convective mixing layr heights, the larger the rate of collection of sea salt particles by the snow crystals. A relationship between the delta^<18>O values in the winter precipitation and the air temperature at the top of convective mixing layr was determined for several synoptic weather conditions which produced winter precipitation. The delta^<18>O values in samples p … More recipitated under conditions winter monsoon were found to be larger than those under other weather conditions at the same temperature. A good relationship is observed between the temperatures at the top of convective mixing layr and the delta^<18>O of samples of winter precipitation under conditions of the winter monsoon.The variations of anion concentration and biological activity in the snow packs were studied at an open site, a deciduous forest site and a coniferous forest site. Concentrations of major anions in the snow pack are higher at the coniferous forest site than at both the open site and the deciduous forest site. Concentrations of major anions gradually decrease as the snowmelt progressed. Concentration of PO_3^<3-> in the snow pack increases as the snowmelt progressed. Concentration of chlorophyl-a in the snow pack is higher at the coniferous forest site than at both the open site and the deciduoud forest site. Concentrations of chlorophyl-a in the snow pack at both deciduoud and coniferous forest site increase during the snowmelt season. Activity of snow algae is considered to be actively during the snowmelt season. By the incubation experiment, NO_3^- of the sample collected at coniferous forest site is consumed probably by the snow algae. Consumption of nitrogen by Scenedesmus is estimated by the incubation experiment as 220 mg/l from the snow pack.Chemical studies of the stream water in a small forested watershed were conducted at Aidzu-Tajima, Fukushima prefecture. The experimental watershed is located under the snowy temperate climate, and has an area of 0.14 km^2. The bedrock of the watershed consists of consolidated sediment formed in the Neogene. The watershed is entirely covered with forest vegetation. Maximum monthly precipitation is observed in summer ; however, maximum monthly runoff is recorded in snowmelt season. The HCO_3^- concentration of stream water is diluted by snow meltwater, and episodic increase of concentrations of Cl^-, NO_3^- and SO_4^<2-> is observed during the snowmelt season. The pH of stream water is lower during the snowmelt season than summer and autumn. The ionic composition of stream water is variable according to the seasons. Bicarbonate is the major anion in summer, and the ratio of Cl^-+NO_3^-+SO_4^<2-> increases in snowmelt season. Less