The Root of the Matter
Let me skip this slide and quickly talk to you about roots. One of the things that we see from mosses to lower vascular plants to things like cycads to large oak trees is a progression that is going on underground with regard to a firm foundation. These foundations are useful for buildings and they're also useful for trees.
 You see here the foundation to a tree. Essentially it takes the form of a buttressed platform, which can be at the surface of the ground or more typically submerged under the surface of soil. From an architectural engineering point of view, this is an absolutely superb way in which you can resist the dynamic forces of wind. If wind for example, is blowing on the canopy of this tree, such that the trunk would torque towards this direction, you can see that this portion of the root system is placed under compression by the rotation of this stem about this pivot point.
Wood is remarkably strong under compression and all of this surface dirt above and below is essentially acting to resist this pivot point. At the opposing windward side, many of the younger roots are actually supporting this portion of the root system in tension, gripping the soil like underground cable wires. We've actually done experiments where we've uprooted trees. I can tell you that roots are remarkably strong. In many cases, we actually have back hoes that were pulled back into excavated holes elastically by a root after it stored enough energy due to deformation.
Here we see a fossil buttressed root-like system. But these are not roots. They are actually horizontally growing stems. We know that plants like this one evolved this kind of architecture way in the distant past.
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