Pruning affects tree movement in hurricane force wind

Abstract

The goal of this study was to determine how different pruning techniques affect trunk movement on live oak subjected to hurricane force winds. Tree movement in wind on nonpruned trees was compared with movement on trees with crowns thinned, reduced, or raised. Twenty trees were blown using a wind generator up to 45 m/s (110 mph) maintained for 3 min. Each tree was instrumented with three orientation sensors at set heights along the trunk to measure its deflection. Thinning or reducing crowns significantly reduced upper trunk movement at all wind speeds, whereas raising did not. Lower trunk movement was not affected by pruning type. These data indicated that foliage and branches toward the top of tree crowns were largely responsible for trunk movement in straight-line wind with those toward the bottom less important. Trees that are reduced or thinned in the manner described could receive less damage in windstorms. © 2008 International Society of Arboriculture.