Runoff response change by devastated forest plantations

20世纪70年代S收集的野外资料表明，在森林覆盖的山坡上，入渗能力几乎总是超过降雨强度。在日本，由于木材价格昂贵，Hinoki(Chamecyparis Obtusa)人工林分布广泛。在无人管理的Hinoki种植园，林下植被减少，Hinoki的凋落物可能会向下移动。因此，从野外观测来看，可能会发生霍顿式的陆上洪水。此外，Hinoki种植园的土壤侵蚀一直是日本的严重问题。在这项研究中，我们监测了未管理的Hinoki种植园小流域的径流，以了解霍顿陆流对了解人类对日本山坡暴雨路径的影响的重要性。研究流域位于日本中部三叶县大宫村。我们在无人管理的Hinoki种植园安装了两个Parshire水槽，在阔叶树区域安装了一个。连续监测径流水的电导率，在选定的暴雨事件中，每隔1或2小时进行现场水样采样，并对溶解离子进行分析。当降雨强度较大时，人工林径流峰值与降雨峰值一致，而阔叶林径流峰值较低，有时延迟到降雨峰值。利用电导率和氯离子将Hinoki种植园的风暴过程线分成两个或三个组分。当降雨强度较大时，降雨分量占暴雨过程的49-67%。这表明在未管理的Hinoki人工林暴雨期间，降雨分量在陆面流中的重要性

The field evidence collected in the 1970's showed that in forested hillslopes, infiltration capacities almost always exceeds the rainfall intensities. In Japan, Hinoki (Chamecyparis Obtusa) plantation distributes widely because of the expensive log price. In unmanaged Hinoki plantations, understory vegetation decreases and the litter of Hinoki is known to be likely to move downward. Therefore, from the field observation, Hortonean overlandflow may occur. In addition, the soil erosion in Hinoki plantation has been the serious problems in Japan. In this study, we monitored the runoff in small catchments in unmanaged Hinoki plantations to understand the importance of Hortonean overland flow for understanding the human impact on hillslope stormflow path in Japan.The study catchments locate in Ohmiya village, Mie Prefecture, central Japan. We installed two Parshall flumes in unmanaged Hinoki plantations, and one in broad leave tree area. Electrical conductivity of runoff water is monitored continuously and in selected storm events, in situ water sampling was conducted 1 or 2 hour interval and dissolved ions were analyzed. When the rainfall intensities were high, runoff peaks coincide with rainfall peak in unmanaged Hinoki plantations, but runoff peaks were low and sometimes delayed to the rainfall peak in the broad-leaf forest. The storm hydrograph in Hinoki plantations were separated into two or three components, using electrical conductivity and Cl ions. When rainfall intensity was high, rainfall components occupied 49-67% of the storm hydrograph. This shows that the importance of the rainfall components in overland flow during rainstorm in unmanaged Hinoki plantations