Apical bud toughness tests and tree sway movements to examine crown abrasion: preliminary results
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Apical bud toughness differences were examined for several species to determine if crown abrasion affects shoot growth of determinate and indeterminate species during stand development. Determinate buds will set and harden after initial shoot elongation in the spring, while the indeterminate shoots form leaves from the apical meristem continuously based on the resources that are available at the time of growth. These growth differences can influence which species’ buds are abraded or broken upon impact with adjoining crowns affecting crown growth. Shoot and bud toughness by species and shoot growth form were evaluated using a pendulum impact tester. Crown movement was assessed by using 3-axial accelerometers in outer most extreme points of crowns. Accelerometers automatically logged the movement of branches in the tree crown over a period of time and are evaluated with local wind data. By using both the crown sway information and associated bud and branch toughness models, evidence is provided to suggest that crown friction and abrasion are contributors to crown and stand development patterns in mixed species stands, often allowing species with determinate shoot growth to stratify above trees with indeterminate growth.