Photo by Artan Sadiku on Unsplash
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Some trees are genetically programmed to grow taller than others. California redwood, Douglas-fir, Sitka spruce in North America; a number of Dipterocarp species (“Philippine” mahoganies) in Southeast Asia; and several species of eucalypts in Australia grow to heights exceeding 165' (50 meters). Do these and other tall trees have special properties that give them mechanical advantages? If so, would these properties produce superior masts and spars for boats?
Why some trees have evolved to grow so much taller than others has fascinated me for more than two decades. Certainly, the environment in which trees find themselves plays a role. The two tallest trees in the world, California redwood (Sequoia sempervirens) and Australia’s mountain ash (Eucalyptus regnans), can reach maximum heights of greater than 328' (100 meters). They grow in very similar latitudes (35° to 40° North and South) and are blessed with winter rains, summer fogs, and ambient temperatures in the Goldilocks range—not too warm, not too cold.
Trees are unsupported columns with crowns that are free to sway in the wind. So, are tall trees stronger than shorter trees? We know that wood density is correlated with many strength properties, yet tall trees do not, necessarily, have denser and stronger wood. Redwood and western red cedar have rather low-density, weak woods. So, some other mechanical properties must be critical for preventing buckling in long, slender columns.