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. Results revealed that the maximum overturning moment (ML) occurred between 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.