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Trees

Fractures of trees at forks

Previously used methods of securing the limbs against breaking consisted of the use of rings and bars or chains. A metal ring connected with a bolt with a nut was placed on the endangered limb (hoop) and the girdling branch. A similar ring was put on the other limb, and then they were connected with metal bars or chains. Such a bond can sometimes still be found on old trees. The disadvantage of hooping tied trunks and limbs is this, that it presses the bark from the outside of the binding, and then, as the trunk thickens, it creates an obstruction and exerts pressure, crushing the bark around the entire circumference, and thus hindering the growth of wood. The downwardly flowing products of assimilation encounter an obstacle in the form of crushed conductive tissues and are stored in the excessively growing parenchyma tissue of the cortex, over the pressure exerted by the hoop. Then, characteristic bulges appear forming an overhang over the ring (drawing).

Drawing. Wrong way of tying: uneven growth of the limb pressed by the ring may lead to fracture.

In this situation, the branch is at risk, because this part of the bark, which is located below the ring, it is devoid of assimilation products up to the point of the nearest branching (the inflow of assimilates to the roots is provided by other branches), which has a negative impact on the growth of wood and may lead to the dieback of phloem and cambium. The entire branch above the ring develops normally until some time, and even better, consuming assimilation products for "own needs". The wood under the ring does not build up, while the developing branch becomes heavier and heavier. Therefore, in such cases, the limb breaks at the place where the handle is placed. This could be prevented by removing the ring early – in the initial stage of pressing. Failure to do so increases the stress in the push ring, and often also in the rod connecting the branches as a result of the expansion of the latter and the increase in their weight. Removing the bond under these conditions becomes dangerous due to the existing stress on the rim, and it is technically difficult. Before proceeding to this, it is necessary to "relax" the rod by pulling the limbs fastened with a binding with the help of ropes, then cut the bond and remove the rings and remove them. Removing the "ingrown" rings as a whole can be very difficult and should therefore be cut into smaller pieces. The removed binding should be replaced with another one, previously prepared and established above.

Currently, other methods of binding the limbs are used and recommended. The bars that hold the tied limbs go right through them and end with a nut with a suitable washer (drawing), adapted shape (usually it is in the shape of an ellipse) to the required form of the cortex wound, which must be removed before binding.

Drawing. The method of making the handle when tying two branches: a - steel round bar; b - washer resting on wood; c - washer under the nut; d - nut.

The washer prevents the nut from denting into the wood, whose small area, due to the action of significant forces that tighten the bond, he cannot prevent it. Therefore, the size of the washers used is different and their length ranges from 6 do 20 cm. Width, while maintaining the elliptical shape, should be half the length. The diameter of the holes depends on the diameter of the rod used and ranges from 10 do 18 mm. In order to maintain the required clearance when applying the washer, the holes should be larger than the bar diameter by o 2 mm. The washers are made of sheet metal or steel flat bars 3-8 mm, depending on the size of the washer. The washer can be slightly bent towards the shorter axis in order to increase the degree of adherence to the wood surface and make it more rigid. The degree of bending should correspond to the circumferential curvature of the trunk. The wood under the washer should be leveled with a chisel. The edges of the washer must always be cut (on the grinder) at an angle of 45 ° or more sharply, which facilitates the growth of healing tissue onto its surface. Moreover, under the nut there should be a circular washer with an outer diameter similar to the width of the elliptical washer or slightly smaller and the diameter of the hole, as in an elliptical washer. The purpose of placing this washer is to better distribute the pressure of the nut on the elliptical washer.