Assessment of Effective Wind Loads on Individual Plantation-Grown Forest Trees

Abstract

Quantifying wind loads acting on forest trees remains a major challenge of wind-tree-interaction research. Under wind loading, trees respond with a complex motion pattern to the external forces that displace them from their rest position. To minimize the transfer of kinetic wind energy, crowns streamline to reduce the area oriented toward the flow. At the same time, the kinetic energy transferred to the trees is dissipated by vibrations of all aerial parts to a different degree. This study proposes a method to estimate the effective wind load acting on plantation-grown Scots pine trees. It evaluates the hypothesis that the effective wind load acting on the sample trees can be estimated using static, non-destructive pulling tests, using measurements of stem tilt under natural wind conditions and static, non-destructive pulling tests. While the analysis of wind-induced stem displacement reconstructs the temporal tree response dynamics to the effective wind load, results from the pulling tests enable the effective wind load quantification. Since wind-induced stem displacement correlates strongly with the sample trees’ diameter at breast height, the effective wind load estimation can be applied to all other trees in the studied stand for which diameter data is available. We think the method is suitable for estimating the effective wind load acting on trees whose wind-induced response is dominated by sway in the fundamental mode.