On the Uprooting Stability of Trees: Combined Loading Effect on Tree Stability Assessment

Tree stability under wind loading is a critical concern for risk management in urban and natural environments. Despite advances in assessment methods, discrepancies persist between theoretical predictions and real-world tree behaviour. This study presents results from an extensive field investigation conducted at the University of Dundee Botanic Gardens to evaluate tree uprooting stability through non-destructive static, dynamic, and uprooting tests. This paper focusses on the programme of non-destructive and uprooting tests conducted across twenty-one trees of a variety of coniferous and deciduous species. Regarding the non-destructive tests, multiple tests were carried out on the same trees, varying both the pulling direction and the pulling height. Geotechnical properties, including shear strength, water content, soil water retention behaviour, and granulometry, were characterized to assess their role in root anchorage. These characteristics were seen to be at least as important as species. The results revealed that the maximum overturning moment (ML) occurred between a 1.6 and 2.9° inclination during uprooting for the partially saturated ground conditions at the time of testing, irrespective of species or biometric parameters. The findings contribute to refining tree stability assessments, offering practical insights for arboriculture and urban planning.