Runoff response change by devastated forest plantations

在1970年代收集的实地证据表明，在森林覆盖的山坡上，渗透能力几乎总是超过降雨强度。在日本，由于原木价格昂贵，扁柏种植园分布广泛。在未管理的扁柏人工林，林下植被减少，扁柏的凋落物被认为是可能向下移动。因此，从野外观测来看，可能发生Hortonean漫流。另外，日本扁柏种植园的水土流失问题也一直是严重的问题。在这项研究中，我们在小集水区在未管理的扁柏人工林的径流监测，以了解Hortonean坡面流的重要性，了解人类活动对山坡暴雨流路径在日本。研究集水区位于日本中部三重县大宫村。我们在未管理的扁柏种植园安装了两个Parshall水槽，在阔叶树区安装了一个。连续监测径流水的电导率，并在选定的暴雨事件中，以1或2小时为间隔进行原位水取样，并分析溶解离子。当降雨强度较大时，未管理的柏木人工林径流峰值与降雨峰值重合，而阔叶林径流峰值较低，有时滞后于降雨峰值。利用电导率和氯离子，将扁柏人工林的暴雨过程线分为两个或三个分量。当雨强较大时，降雨分量占暴雨过程线的49-67%。这表明，在未管理的柏木人工林暴雨期间，降雨组分在坡面流中的重要性

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