The causes of forest damage and the process of ruin in this field

1990年第19号台风对奇伊半岛的森林造成了巨大的破坏。这次台风主要造成林分断干和连根拔起两种类型的森林破坏。本研究选取了断枝、林分连根拔起和毁林遥感调查为研究对象。主要研究结果如下：(1)树干断裂是由于树干长度断裂造成的。当树干纵裂时，截面模量值变小，树干在正常状态的一半弯矩作用下折断。(2)林分类型越多，树干裂解越严重。在修剪高度较高的树枝处，发现有许多树干折断。(3)在林分连根研究中，对毁林情况进行了调查，并对林分倒塌情况进行了考察。(4)林分倾斜、断根时，林分的下拉力最大。详细测量了林木根系的分布，建立了林分连根拔除阻力模型。(6)该模型能较好地处理树干倾斜引起的根系旋转，并能再现试验中根系的位移。(7)利用MOS-1数据对宫山町林区的受害林木进行了遥感取材。

The forest in Kii peninsula was received large damage by the typhoon No.19,1990. This typhoon are mainly caused forest damage of two types that are stem breakage and uproot of stand. The topics chosen are stem breakage, uproot of stand and the surveying of damage forest by remote sensing in this study. The summarized results are as follows.(1)Stem breakage is caused by the length split of trunk. When the split of trunk is produced lengthwise, the section modulus becames small value and the stem breaks down by the bending moment of a half of normal state.(2)The more type of stand occurs the split of trunk, the more stem breakage happens. Many stem breakages are found at stand pruned highly branch. This stand is the type which is easy to split.(3)In study of uproot of stand, the damage forest is surveyed and pulling down of stand is examined.(4)The force of pulling down of stand reaches the peak load as soon as stand inclining and when root breaks off, it makes a sound.(5)The distribution of root system is measured in detail and the resistance model on uprooting of stand.(6)This model is able to deal with the rotation of root system caused by stem inclining and to reproduce the displacement of root system in the examination.(7)The damage forest is taken out in forest of Miyama cho used by Mos-1 data for remote sensing.