Biogeochemical Dynamics in Forested Watershed during Winter

在日本中部的Tohkamachi进行了冬季降水的化学研究。冬季降水样品中的Cl~-/Na~+和Mg~(2+)/Na~+比值与海水接近。这一结果表明，冬季降水中的Na~(2+)、Mg~(2+)和Cl~(2-)均来源于海水。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。含有海盐颗粒的云滴被认为是通过降雨过程被雪晶捕获的。结果表明，对流混合层高度越高，雪晶对海盐粒子的收集速率越大。在几种产生冬季降水的天气条件下，确定了冬季降水中的增量与对流混合层顶部气温之间的关系。样本p…中的Delta^&lt；18；O值在相同温度下，冬季季风条件下的沉淀量大于其他天气条件下的沉淀物。在冬季季风条件下，对流混合层顶部的温度与冬季降水样品的δ、lt；18和gt；O有很好的相关性。针叶林地积雪中的主要阴离子浓度高于开阔地和落叶林地。随着积雪融化的进行，主要阴离子浓度逐渐降低。积雪中PO_3~-浓度随着积雪融化的进行而增加。针叶林地积雪中的叶绿素-a浓度高于空地和落叶林地。在融雪季节，落叶和针叶林地积雪中的叶绿素-a浓度都有所增加。雪藻的活动被认为在融雪季节是活跃的。通过培养实验，针叶林样地采集的样品中的NO_3~-可能被雪藻所消耗。通过培养实验估计栅藻对积雪中氮的消耗量为220 mg/L。对福岛县野津-田岛一个小森林流域的溪水进行了化学研究。实验流域地处多雪温带气候条件下，面积0.14 km2，基岩为新近纪形成的固结沉积物。分水岭完全被森林植被覆盖。最大月降雨量出现在夏季，而最大月径流出现在融雪季节。融雪水稀释了溪水中的HCO_3~-浓度，融雪季节出现了阶段性的增加。融雪季节溪水pH值低于夏秋两季。溪水的离子组成随季节而变化。夏季以碳酸氢盐为主要阴离子，融雪季节，Cl^-NO_3^-SO_4^&t；2-gt；较少

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