This is a follow-up to his previous Questions about Trees which was an inquiry "about the puzzling diversity of forest trees."

This one looks into questions like:

  • Why do the leaves of trees have such varied shapes?
  • Why are trees so tall?
  • Why are trees trees (rather than other kinds of graphs)?
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From Scott Alexander: "Don't trust trees, they are seedy and shady"

I answer the "why are trees so tall" question at .  The rough answer is that height limiting treaties need to be enforced, and enforcement is costly, and for the most obvious enforcement mechanism that trees have available (negative allelopathy), enforcement is not observable by other trees.  So if any trees did enforce a height limiting treaty, the trees that freeloaded on their enforcement would out-compete them, and that's why we see tall trees and not height-treaty-limited trees.

Praise our lord Moloch for giving us trees in which shades we can rest!

I remember skimming an article which used four parameters (including mesophyll conductance and stomatal conductance) to model simple leaves.

The authors managed to "grow" a ligule, a needle and maybe some other shapes. It was really fun, unfortunately not directly related to what I was doing then (and of course, direct measurement of conductances of various leaf tissues in the nature would be a pain). They could not yet progress to complex leaves, but still it was a neat paper.

Question 1: Why do the leaves of trees have such varied shapes?

This question doesn't seem to be well answered in the sense of a forest where the ecosystem in terms of dryness and temperature is relatively constant.

One of the main reasons we have variety in nature is that if one species starts taking up a large share, strategies that prey on this species get a boost.