Visual Tree Assessment (VTA)
A tree is a self-optimising mechanical structure (Mattheck and Breloer 1994 *). A generating system which reacts to mechanical and physiological stresses by growing more vigorously to re-enforce weak areas, while depriving less stressed parts. This precept is described by Claus Mattheck as the axiom of uniform stress. An understanding of the axiom of uniform stress allows an Arborist to make informed judgements about the condition of a tree. Claus Mattheck introduced a biomechanically based system of visual tree assessment (VTA), which uses the reactive nature of tree growth. The basis behind VTA is the identification of symptoms, which the tree produces in reaction to a weak spot, or area of mechanical stress.

Although, Claus Mattheck stresses the limitations of this system by saying; "We can use VTA to state to what extent a defective tree is at greater risk of breaking, compared with a completely sound one. However, since nature’s principle of lightweight structures allows a natural failure rate to occur even without defects, there can be no absolute guarantee of safety." It is essential that any arborist using VTA has a broad range of experience of different tree species, as individuals and in groups, to enable them to make informed and reasoned decisions about ‘tree safety’.

* The Body Language of Trees – A handbook for failure analysis by Clous Mattheck and Helge Breloer - Research for Amenity trees No 4 HMSO Books – ISBN 0117530670

Arboriculture:
Hazard Assessment + [ Visual Tree Assement - Identify Mushrooms ] - Developments + [ Compromise ] - Legal Iissues - Ancient and Veteran Trees