Runoff response change by devastated forest plantations

20世纪70年代收集的野外证据表明，在有森林的山坡上，入渗能力几乎总是超过降雨强度。在日本，由于原木价格昂贵，日木人工林分布广泛。在未经管理的白木人工林中，林下植被减少，白木凋落物可能会向下移动。因此，从野外观测来看，有可能发生霍顿式覆坡流。此外，日木人工林的水土流失问题一直是日本面临的严重问题。在这项研究中，我们监测了无人管理的日木人工林小集水区的径流，以了解Hortonean陆地流对于理解人类对日本山坡风暴流路径的影响的重要性。该研究的集水区位于日本中部三重县的大宫村。我们在无人管理的日木种植园安装了两个Parshall水槽，在阔叶树区域安装了一个。连续监测径流水的电导率，并在选定的暴雨事件中，每隔1或2小时进行原位水采样，分析溶解离子。当降雨强度较大时，无管理的杉木人工林径流量峰值与降雨峰值重合，而阔叶林径流量峰值较低，有时滞后于降雨峰值。利用电导率和氯离子将日木人工林的风暴线分为两部分或三部分。强降水时，降雨分量占暴雨线的49% ~ 67%。这说明了降雨成分在无管理的杉木人工林暴雨期间的坡面流中的重要性

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