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

1990年第19号台风对喜岛的森林造成了严重破坏。此次台风对林场造成的破坏主要有两种类型：林干断裂和林分连根拔起。本研究选取的主题为林干断裂、林分连根拔起和毁林遥感调查。总结结果如下：(1)茎断是由于树干长度断裂造成的。当树干纵向产生劈裂时，截面模量变小，树干在正常状态一半的弯矩作用下发生断裂。(2)林分类型越多，树干断裂越多。许多茎断裂是发现在林分修剪高枝。这种支架是易于拆分的类型。(3)在林分连根拔研究中，进行了毁林调查和林分拔除检查。(4)立木倾斜时，立木下拔力达到峰值荷载，立木断根时发出声音。(5)对林分根系分布进行了详细测量，建立了林分根系抗拔模型。(6)该模型能够处理由于茎倾斜引起的根系旋转，能够在检测中再现根系位移。(7)利用Mos-1遥感数据对宫山町森林进行毁林提取。

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.