Bending of Pinus jeffreyi in response to wind

Abstract

<p><em>Aim of study:</em> To evaluate the degree of trunk sway in relation to wind velocity, with varying temporal integration and to compare this relation among seasons.</p><p><em>Area of study:</em> Sierra de Juárez, Baja California, México</p><p><em>Materials and Methods:</em> Displacements of a 19 m tall Jeffrey pine tree were recorded at 6 m from a three dimensional digital compass during one year, at c. 4 Hz. Adjacent wind speed at 6 m was recorded at 1 Hz.</p><p><em>Main results:</em> Sway was essentially unaffected by wind in the same second  but increasing dependence of cumulative displacement on average sustained wind speed was found for intervals of 1 to 60 minutes (r² up to 0.89).  The relation is generally log-linear but apparently differs in parameters between seasons.</p><p><em>Research highlights:</em> Wind-sway relations are clear from integration of several-to-many minutes. However, to estimate cumulative stress, sub-second data on sway are essential.  Sub-second, precision measurements of sway can be registered from small, inexpensive sensors.</p><p><strong>Keywords:</strong><strong> </strong>biomechanics; <em>Pinus jeffreyi</em>; seasonality; stress accumulation; time series; tree bending.</p>