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CONSERVATION AND ECOLOGY


A new approach to tree surveys has recently come to the fore which


involves identifying areas of high and low risk


species to measure growth rings and bark diameter. The stability and health of the tree can then be assessed much more accurately. As the micro drill enters the tree, the


Formal Inspections


A formal inspection is one where a person visits a tree for the sole reason of assessing that tree, for either inventory or health and safety purposes. This will normally take the form of a ground level inspection looking at the general health and stability of the tree; assessing die back, uprooting or structural defects. This provides a cost effective means of


identifying trees which present a risk and require a detailed inspection. In order to undertake a formal inspection, a general knowledge of trees and the ability to identify poor health or structural weaknesses is required. Further, the capacity to assess the height and falling distance of the tree is also essential in order to establish the element of risk the tree provides. The ability to identify visible signs of ill health or structural weakness, such as cavities or heave (root plate movement), is also necessary as they may cause the tree to fail.


Detailed inspections


Detailed surveys should be carried out by a qualified specialist who is experienced in the field of investigation. The landowner should satisfy themselves of the specialist’s qualifications and experience and ensure that they have the necessary insurance to carry out the tasks required. Generally, an initial ground level visual assessment will take place to identify signs of structural failure. This may result in the need for further specialist investigation comprising either soil and root assessments, aerial surveys or the use of diagnostic tools such as resistograph drill. Detailed surveys are generally confined to trees of high amenity value to the landowner.


Recording details


Records should be kept to provide evidence of due care and attention. They should not be onerous, but should record date and type of inspections and any actions required and subsequent remedial works as appropriate. They do not need to include every tree, but it would be advisable to list individual trees that present risk listing and identifying them and their location, the findings of detailed inspections and the actions taken to minimise risk.


Resistograph testing


The resistograph is an instrument that detects decay and cavities in trees and timber. The arborist is able to detect wood decay, stages of rot, cavities, cracks and ring structure. It can also be used in certain


resistance of the wood changes the rotation speed of the drill. These variations are translated into a graph. The tiny drilling hole closes itself up without any damage to the tree. This then provides written evidence which, combined with the experience of the arborist, allows a rational decision to be made.


There is no substitute for experience, as


the drill provides evidence of only the area where it is used. The arborist’s experience will tell him, depending on the pathogen, where the greatest likelihood of failure is liable to be. Different fungal bodies attack different areas of the tree; some favour roots and buts, whilst others may favour branches or limbs. It is, therefore, important to ensure the arborist you use has sufficient experience to assess the tree before detailed surveys are under taken.


Article by John Nicholson, Independent consultant on habitat and landscape management.


PC February/March 2019 119





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