Abstract
It is often observed that a tree that had once penetrated a mesh of a chain-link fence has continued the thickening growth for long years to engulf part of the fence. We obtained a specimen of a tree trunk containing engulfed part of a fence. The trunk was from chinese elm (Ulmus parvifolia) with a diameter of about 25 cm, and the angle between the trunk axis and the fence plane was about 38 degree). An X-ray image of the specimen demonstrated for the first time that the metal wire of the fence engulfed by the trunk did not disappear nor was rotten, but stayed intact with some deformations. 2) X-ray CT scan images were obtained at 1 mm intervals along the axis perpendicular to the fence plane. The growth ring formation was highly disturbed by the wounding caused by the fence wires and then recovered a few years later. 3) Based on the results of the three-point bending test of the fence wire (JIS G3543 V-GS2) the force of the thickening trunk pressing the wire at the start of the engulfment was estimated to be as high as 190 N (19.4 kgf), and the mechanical work done until then was estimated to be about 2.3 J.
