Flexibility Limits Bending in Wind

photograph of bent tree in front of the blue sky during the day

Biological Strategy

AskNature Team

Image: Greg Bate / Flickr / Some rights reserved

Protect From Wind

Wind subjects living systems to various forces, such as compression, twisting, turbulence, and tension. These forces put living systems at risk of losing the ability to perform life-essential functions, such as when a plant becomes uprooted. Wind can result from weather phenomena or rapid movement through the air, as when flying. Wind is typically not a constant or predictable force, so living systems must be able to function both with and without its presence by adjusting to its direction and speed. A good example is how plants’ leaves and stems are flexible so that they can align with the wind, rather than being battered by it.

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Conifers and Others (Pines, Spruce, Gingko)

Clade Gymnosperms (“naked seeds“): Conifers, cycads, Gingko, gnetophytes

There are approximately 1,000 known species of Gymnosperms. These include well known needle-bearing plants like pines, firs, and spruce, as well as some with broad leaves like the Gingko and the gnetophytes. Instead of flowers, gymnosperms produce unenclosed (“naked”)seeds exposed on the surface of cone scales. Economically, conifers make up 45 percent of the world’s lumber production. The first gymnosperms evolved over 390 million years ago in the Paleozoic Era and dominated landscapes for a quarter of a billion years before the evolution and diversification of flowering plants.

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The trunks of trees reduce their tendency to bend in the wind due to their torsional flexibility.

“Another use of torsional flexibility, perhaps less sophisticated, happens on a larger scale. Wind on a tree will twist it unless everything (including the wind) is perfectly symmetrical about the trunk. But twisting brings bits of tree closer to a downwind orientation and brings the bits into closer proximity to each other. Both should reduce the tendency of the tree to bend over. Clever–lowering torsional stiffness ought to reduce the requirement for flexural stiffness! While we don’t have data for any intact tree, the effect has been shown for clusters of leaves (Vogel 1989), and casual observations in storms suggest that it works on larger scales. Tree-level use is consistent with the relatively low values of torsional stiffness of fresh samples of tree trunks and bamboo culms (Vogel 1995b).” (Vogel 2003:382)

Vogel S. Comparative Biomechanics: Life’s Physical World. Princeton: Princeton University Press; 2003. 580 p.