Effects of dynamic site conditions on plant succession in the riparian area with a large-scale collapse in the upstream area

本研究旨在探讨上游大型塌陷区河岸区动态立地条件对植物演替的影响。调查区域位于上游塌陷区，也就是阿部江上游的大谷河河岸区，由于上游地区有大规模塌陷区，因此一直期待泥沙的输移。通过航片解译，调查了植物群落结构和演替，调查了林地消失和恢复的面积。此外，还讨论了降雨干扰的频率和强度对演替的影响。根据物种组成和密度，将研究点的森林划分为4个阶段。第一个阶段是先锋树种群落，即细叶赤杨、大叶赤杨、沙柳群落，距入侵10年，尚未经历过10~30年的概率降雨量(400~500 mm)。然而，进入第二阶段和第三阶段的林分经历了概率降雨。第二阶段为10~25年生三层林，中层为下一代物种--云杉、蒙古栎和枫树，形成林冠下的底层先锋树种。第三阶段为25-45年生林分，林下层以侧生树种和枫树种为主。第四阶段为45年生以上的林地，以枫树为主。这项研究的结果是，Ohya河的河岸植物群落与干扰的强度和频率有关。

The purpose of this research is to clarify the influence that the dynamic site condition impacts on the plant succession in the riparian area that has a large-scale collapse place in the upstream area.Investigation area is on the riparian area in Ohya River, the upper reach of Abe River, which sediment transport is constantly expected, because the place has a large-scale collapse in the upstream area. The plant community structure and the succession were surveyed and the area of the disappearance and recovery of the forest place were investigated by the aerial photograph interpretation. In addition, the influences that the frequency and the strength of the disturbance that made rainfall an index influence on the succession were discussed.Based on the species composition and sere the forest in the research sites was classified in the 4 stages. The first stage is community of pioneer species, Alnus filma, Alnus maximowiczii, Salix sachalisesis and passed 10 years from the period of invasion and has not experienced the 10-30 year probability rainfall (400-500mm) yet. However, the stands that are advanced to the second and third stages have experienced the probability rainfalls. The second stage is 10 to 25 year three-story forest, next-generation species-Carpinus in the middle story, Quercus mongolisa var.grosscratta and Acer forming the ground story under the canopy of pioneer species. The third stage is 25-45 year old stand dominated by side species and Acer species in the ground story. The fourth stage is 45 year or above forestland covered mostly by Acer species. As a result of this research, it became clear that riparian plant communities in Ohya River is related with the intensity and frequency of disturbances.