Preliminary experiments and verification of controlled pulling tests for tree stability assessments in Mediterranean urban areas

Tree stability assessments are an indispensable tool for preserving the safety of people and property. National legislation identifies the tree custodians as those responsible for monitoring the risk factors with regard to civil and criminal liability for damage to persons or property. Currently evaluations to assess tree stability are usually made by means of visual methods and they do not always allow for an evaluation of the true health the plant. The controlled pulling test is considered to be particularly useful to evaluate the tendency of root-plate windthrow caused by thrust exerted by meteorological events such as wind and snow. This type of instrumental analysis is not yet widespread in Italy and it is sometimes applied improperly. As a result, this preliminary study focuses on these issues in order to develop a methodology with particular reference to the definition of the fundamental variables, as well investigating the possibility of its application to Mediterranean species. ► Falling trees or tree parts constitute a significant hazard to people and property. ► Visual analysis does not always permit a complete study of tree health and stability. ► Controlled pulling test represent a tool to visual analysis for evaluating root-plate rollover. ► Pulling tests estimate the critical wind speed that causes windthrow. ► These procedures improve stability tree assessment.