Within the scope of the study carried out in cooperation with Şişli Municipality Parks and Gardens Directorate and Istanbul University-Cerrahpaşa Faculty of Forestry, approximately 200 large and old trees were identified in the district in the first stage.
While trees in parks and gardens, as well as on streets and in areas with heavy pedestrian and vehicle traffic, will be included in the study, century-old trees in campuses such as Darülaceze, where people spend most of the day, will also be examined.
In the first stage of the study, the physical characteristics of the trees determined, such as height, trunk structure, crown diameter, obliquity and branching points, will be measured. The ages of the trees will also be determined approximately by examining previous experiences and annual rings taken from some trees with an increment auger.
After this, acoustic tomography will be applied to reveal the condition of the trees inside the trunk. By measuring the travel speed of sound waves sent through sensors placed at certain intervals on the tree, the differences between living tissue and areas with decay or gaps will be detected.
If rot is detected in the measurements, a re-examination will be made from different heights of the body. Thus, not only the point where the rot is located, but also where it starts on the trunk of the tree and how long it continues will be determined, and the data obtained will be evaluated in three dimensions.
However, the presence of rot in the trunk alone will not be considered sufficient to cut down the tree. In addition to the tomography result, data such as the tree's height, crown diameter, inclination, branching structure and wind exposure will be evaluated and the risk of the tree falling over will be calculated.
By including the strongest wind data ever recorded in the region into the model, different risk levels will be created for trees. Necessary interventions will be determined for trees in high and extreme risk groups.
These interventions will vary depending on the condition of the tree. In order to reduce the peak load, pruning will be done, visible cavities will be cleaned and mechanical supports will be used when physical conditions are suitable. Thus, the aim is to reduce the risk of the tree falling over and to keep it alive in its place as much as possible.
Cutting will be considered as a last resort in cases where the tree is no longer irreversible and it is not possible to keep it alive safely. In this case, it will be planned to remove the tree and plant a new tree in its place.
It was stated that the importance of the study was demonstrated by the tree fall in Teşvikiye last month, and after the fall of a large plane tree that appeared healthy from the outside, rot was detected starting from its roots and continuing to its trunk.
Istanbul University-Cerrahpaşa Faculty of Forestry Lecturer Assoc. Dr. Serhun Sağlam told the AA correspondent that the tree falls in cities in recent years once again reveal the importance of internal rot that cannot be seen from the outside.
Reminding the large plane tree that fell in Teşvikiye last month, Sağlam stated that trees that appear healthy from the outside can rot from the inside, and that they aim to detect similar risks in advance with this study.
Stating that approximately 200 large and old trees will be examined in the first stage, Sağlam stated that the study is not limited to parks only, but also includes street trees and centuries-old trees in areas where people spend time, such as Darülaceze.
"The work is done to keep the trees alive as much as possible"
Sağlam stated that monuments and monument candidate trees are indispensable for urban life, but they can pose a risk due to their size, and regarding the purpose of the study, he said, "We are working on monuments and trees that have monument value, that is, trees that are candidates for becoming monuments. Of course, these trees are very valuable aesthetically and have countless benefits to society. However, we also encounter some problems when living together. Unwanted accidents can occur, especially in stormy weather, as they reach gigantic sizes. We saw this in the large plane tree that fell in Teşvikiye last month. It looked quite healthy from the outside, but when it fell, it started from its roots to its trunk." "The main purpose of this study is to detect this internal rot, which is not noticeable from the outside, and then calculate the risk of falling by evaluating the tree's height, crown diameter, bending structure and wind data in the region. Thus, we aim to keep these centuries-old trees alive as much as possible and to prevent them from harming people, buildings and vehicles." he said.
"Sound waves show the inside of the tree in three dimensions"
Stating that the acoustic tomography method is applied without damaging the tree, Sağlam explained the working principle of the system in detail as follows:
"In acoustic tomography, we place sensors on the trunk of the tree at regular intervals. Then we send sound waves. The sound travels normally in the living tissue of the tree. However, when it comes to areas with rot or gaps, it cannot pass directly, it has to go around. We determine the location of the rot by measuring the speed of the sound. If we see rot at the bottom, we go up one layer and repeat the measurement. Thus, we can see in three dimensions where the rot starts and continues to where. "We calculate the real rollover risk by adding it to the model with all physical properties such as diameter, height and wind load."
"Rot formation does not necessarily mean that the tree will be cut down."
Emphasizing that the priority of the work is not to cut down trees, but to extend their lives as much as possible, Sağlam said:
"The occurrence of rot on a tree does not mean that we will immediately cut it down. If we see that the tree can live safely for 10 or 20 years, we definitely try to keep it in place. For this, we prune to reduce the peak load, clean out any cavities, and strengthen the tree with mechanical supports when necessary. However, if it has reached an irreversible point and poses a serious risk for human life, then as a last resort, we remove the tree and plant a young and healthy tree in its place."
Stating that approximately 200 trees were included in the study in the first stage, Sağlam said that the district has a richer variety of old trees than expected.
Sağlam said, "Şişli is not a very large district, but despite this, we have many large and old trees, especially plane trees. In the first stage, we identified approximately 200 trees. These will be examined as a priority. Later, if necessary, we can switch to medium-sized trees. We also see in the age determinations that many of our plane trees are over 100 years old. There are those that have reached 130-150 years of age. Some of them are already registered as monumental trees by the Ministry." he said.
"We detected rot on the tree, which appeared completely healthy from the outside."
Stating that they encountered a remarkable example during the inspections on the street, Sağlam explained why the measurements were repeated layer by layer with the following words:
"The tree we are currently working on looked completely healthy from the outside. It is on a very heavily used street. People sit under it, children play in the park right next to it. In our first measurement, we saw that there was rot inside. Therefore, we take measurements again from the second level. Because we need to see how far the rot continues. After that, we will calculate the risk of falling over, together with the other physical characteristics of the tree, and if pruning is required, this result will determine the severity."
"The centuries-old trees in the Darülaceze will also be protected with the same method."
Stating that the old trees in the Darülaceze campus were also included in the study, Sağlam gave the following information:
"People live under these trees 24 hours a day in the Hospice. This is an institution with a history of more than 130 years and there are many centuries-old plane trees in its garden. All trees here will be examined with the same method. The risks of falling over will be calculated, the necessary pruning and other interventions will be reported. Because the safety of people in these areas is as important as the protection of the trees. In cities, trees live under serious pressure due to vehicles, people, exhaust gases and trapped roots. However, they provide us with clean air, by trapping precipitation. "They reduce the risk of floods, provide coolness in summer and reduce energy consumption in winter. Therefore, technical studies alone are not enough. People should also not damage the roots, trunks and branches of trees. We need to strengthen this culture through training and awareness-raising activities to prevent behaviors such as engraving on trees."
