Winderregte Blattschwingungen

1991

S. 402-407

4 Abb., 7 Lit. Ang.

Unselbständiges Werk

200033434

Softwood trees such as poplars and birches display characteristic, regular oscillations of the leaves in a breeze. These oscillations are of the coupled translational/rotational type. The leaf acts as a resonator which is formed by the leaf mass and the stiffness of the leaf stem. The poplar leaf, which oscillates in a direction normal to the direction of the wind, corresponds to a Kaplan turbine which is especially designed for small flow velocities. This leaf is particularly suited to convert small wind speeds to high oscillation velocities. In this way the diffusive exchange of CO2 and water vapor can be achieved with a smaller leaf area. This reduction in leaf mass explains the large trunk growth rates of poplars.