Bending of Pinus jeffreyi in response to wind

Stephen H. Bullock, J. Francisco Martínez-Osuna, Eulogio López-Reyes, José L. Rodríguez-Navarro


Aim of study: To evaluate the degree of trunk sway in relation to wind velocity, with varying temporal integration and to compare this relation among seasons.

Area of study: Sierra de Juárez, Baja California, México

Materials and Methods: 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.

Main results: 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.

Research highlights: 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.

Keywords: biomechanics; Pinus jeffreyi; seasonality; stress accumulation; time series; tree bending.


biomechanics, Pinus jeffreyi, seasonality, stress accumulation, time series, tree bending

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DOI: 10.5424/fs/2015243-08292