Saturday, October 31, 2015

Seeing Tree Growth As Behavior (part 1)

Over the years I have observed some interesting forms of growth in trees, which have the aspect of behavior, as opposed to simple growth.

First is what is called an oxbow. Here the tree's leader is damaged, so another branch curves upward to become the new leader. What is remarkable is that the new leader first curves backward, then straightens upward, so that it is positioned directly above the lower trunk. Somehow the new growing leader knows where the lower trunk is. I once had a large collection of oxbows from downed trees in a small patch of boreal forest, indicating they are not a rare or chance occurrence.

Note that there is a good reason for this behavior, which is balance. If the upper trunk grew some distance out from the lower trunk then the tree would be unbalanced. Wind is a great threat to trees, so balance is important. This is probably why open grown trees brow symmetrically, even at mid-latitudes where the sun is always on just one side. My conjecture is that the trees growth in general is a tradeoff between balance and efficient solar collection.

I observed another case of apparent balance when I began building a log cabin on a remote island in Northern Ontario, in the Boreal forest. I started with several spruce trees that grew along the shore, on the edge of the island's forest. Because of their location, their branches on the open or water side were much larger than those branches on the forest side, probably because the open side is where the sunshine was.

When I limbed them I found that they were unusable because the trunks were curved. The trees had actually grown so as to lean backward, toward the forest and away from their heavy side, just a a person would do if holding a weight out in front of them. By doing this they were more balanced.

What this suggests is that trees somehow know where their various parts are and can control their growth in order to achieve overall balance. If so then their growth is something like behavior.

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