Integrated study on carbon dynamics and water cycle in the atmosphere-forest-stream system of mountainous catchment

全球气候变暖是当今世界面临的最重要的环境问题之一，森林与大气之间CO_2交换的研究在世界范围内得到了广泛的关注。然而，只有少数研究集中在森林流域水文循环中涉及的总碳动态，虽然这是一个关键的过程，评估森林生态系统对气候的反馈作用。本研究试图了解这个过程中的一个温带森林集水区的微气象，地球化学和水文观测的基础上。调查结果总结如下。(1)通过对不同地形条件下热量/H_2O/CO_2通量的计算，分析了不同地形条件下热量/H_2O/CO_2通量的变化。(2)用观测资料验证了一个模拟林冠上和林冠内热量/H_2O/CO_2运动的多层模式。(3)根据详细的测量结果估算了森林的生物量热储量。(4)以溶解有机碳（DOC）、钠和硫酸盐为示踪剂，研究了坡面径流路径。(5)对土壤DOC沿着径流过程的动态进行了分类，并估算了土壤DOC的收支。(6)研究了氮和硫的动态，并将日本的特征与北美的特征进行了比较。

Global warming is recognized as the most important environmental issues, and studies on the CO_2 exchange between forest and the atmosphere are conducted all over the world. However, only a few studies focus on the total carbon dynamics involved in hydrological cycle in a forested catchment although this is a key process for evaluating feedback effects of forest ecosystem on the climate. This study attempts to understand this process in a temperate forested catchment based on micrometeorological, biogeochemical and hydrological observations. The findings summarized as follows. (1) Effects of topographical effects on heat/H_2O/CO_2 fluxes were assessed to get their accurate rates. (2) A multilayer model simulating heat/H_2O/CO_2 movements above and within forest canopy was validated by the observations. (3) Biomass heat storage of the forest was estimated from the detailed measurements. (4) Flow pathways on hillslope were estimated using dissolved organic carbon (DOC), sodium and sulfate as the tracers. (5) The dynamics of DOC along the runoff process were classified and the DOC budget within soil was estimated. (6) The dynamics of nitrogen and sulfur were investigated and the characteristics in Japan estimated from our study were compared with those in North America.