“True, I talk of dreams,
Which are the children of an idle brain,
Begot of nothing but vain fantasy,
Which is as thin of substance as the air…”
Romeo and Juliet, William Shakespeare
It’s true the atmosphere around us is invisible, but is it really as insubstantial as Mercutio thinks? For humans perhaps, but not for photosynthetic organisms. Sure, plants may appear to be firmly rooted in the ground, but this tether to substance is only a deception. They really make a living knitting mass out of thin air by pulling carbon dioxide from the atmosphere and fixing it into useful biological molecules.*
This feat is most obvious in the world’s most massive organisms- the Sequoias. These giants are experts at silently converting air into substance. Tree size can be measured in different ways like height or girth, but the true measure of mass is trunk volume. Based on this measure, the largest tree ever reported was the Lindsey Creek tree. It was felled by a storm in 1905, and the local paper published some details on its measurements to give an estimated trunk volume of 90,000 cubic feet. The Crannell Giant was discovered in 1926 and more precise measurements calculated a minimum trunk volume of 61,573 cubic feet. It was logged in the late 1940s.
The most massive living tree (single stem) is the giant sequoia (Sequoiadendron giganteum) General Sherman in the Giant Forest of Sequoia National Park with an estimated trunk volume of 52,508 cubic feet. It soars to a respectable 274.9 feet in height with a base circumference of 102.6 feet and is estimated to be more than 2,000 years old. It is truly the biological manifestation of majesty.
Of course, even this mighty giant has humble beginnings. Check out this video that documents the growth of sequoia seedlings over the first five years of their lives. You may still doubt how those young trees could grow into a giant the size of the General Sherman, but over the course of ~2300 years the area corresponding to the base of the General Sherman received 341 Gigawatt hours-worth of incident solar energy.** What would you do with that much energy? Well, you could power New York City for about a month. If you are a sequoia, you could use photosynthesis to turn it into ~50,000 cubic feet of tree.
Don’t think that an older tree like the General Sherman is going to sit on its laurels when it comes to gaining mass. As I mentioned yesterday, new research has shown that this kind of older tree is increasing its growth rate when it comes to adding mass. The statement can seem quite intangible when juxtaposing the most massive living organism and a substance as thin as air. How much mass are we talking about? The 40 cubic feet of growth General Sherman adds annually at 13.42 pounds of carbon per cubic foot corresponds to 537 pounds of carbon. That’s just over a quarter ton of carbon extracted from the air each year by a single tree.
With those numbers, I’ll have to disagree with Shakespeare. It seems that air has more substance than Mercutio would lead you to believe. Perhaps there is more to that dream as well.
* Remember the equation for photosynthesis? No? You must be new here.
**∏(5.5 m)2 = 123 m2 x 4.2 kWh/day x 365 days/yr x 2300 yrs = 341GWh
The incident solar radiation on the area of the size of the base of the General Sherman. Sure, the size of the base would be changing over the course of those 2300 years, but the canopy area is much larger and the error bars on the age are on the order of centuries, so I’m calling it close. If anyone else would like to come up with a better algorithm that takes into account the changing area over the course of the tree’s lifetime, please show your work in the comments section below.
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