Strategy for preservation of veteran trees in the city - a model of conduct based on plant defense mechanisms and the idea of sustainable development

Although the research on the defense mechanisms of trees was carried out in the 1930s, it was not until the mid-1980s that – under the influence of Alex Shigo – an arborist movement began, which was based on understanding defense mechanisms, growth physiology and development of trees. A balanced approach to shaping, planting, care and protection of trees at different ages is still evolving. The changes include particularly the venerable specimens, for until recently invasive methods of treatment and care were used. The aim of this paper is to present a model for dealing with veteran trees. The research included a representative sample of 400 older trees with outstanding natural, historical and landscape value, located in greenery areas (parks, squares, street greenery). These trees are exposed to strong anthropogenic pressure and accelerated degradation due to unfavorable habitat conditions and urbanization processes. The method of valorisation of these trees, assessment of their health status and vitality with regard to the aspect of human safety and their property is presented. The rules for dealing with the trees in question have been defined to improve their biological and mechanical functions as well as to minimize the risk of an accident