The mechanical effects of bulges developed around bark-included branch junctions of hazel (Corylus avellana L.) and other trees

Abstract Key message Large bulges formed around bark-included branch junctions can be conceived of as ‘compensatory growth’. Despite Claus Mattheck’s hypothesis that ‘the larger the bulges, more likely junction is to fail’, this study identifies extent defect inside such key information in predicting junction’s load-bearing capacity. A currently prevalent rule European arboriculture if a tree associated with large bulge in-line plane included bark then it fail than there smaller or absence bulging. This for arborists originates from an initial suggestion no data and not logically consistent recent research into effects natural bracing trees, nor guidance provided by International Society Arboriculture. also raises question how correctly interpret function these at junctions: either secondary growth has been pushed side internal pressures, compensatory developing weakened component. To test veracity rule, 117 common hazel ( Corylus avellana L.) were subjected tensile tests, comprising controls within them specimens exhibiting range sizes. In addition, photographs failure 110 categorized assess frequency failed different degrees The results mechanical testing identified three significant factors affected maximal bending moment their morphology, diameter ratio width apex junction. Overall, each category tested, bulging was found predictor junctions’ moment. finding reinforced analysis images inclusion where most frequent inclusions those little Both findings identify would better interpreted growth. highlights need further on capacity inform managers substantial variations biomechanical performance have yet elucidated.