After my last fun fact Friday (all about how water gets from the roots of trees to their leaves), my mind was racing with more questions.

The one that I felt I couldn’t ignore was less about what was happening inside the trees and more about the exteriors. Of course, once I started digging into the internet’s resources to find the answer to this question, I discovered that the exteriors of trees are a result of what is happening inside them.

Why do trees have such different types of bark?

The answer, it turns out, was far more difficult to uncover than I imagined. Though I still haven’t discovered a solid answer in any journals, articles, or even on the great oracle (Wikipedia), the quest for it led me to learn more about tree anatomy than I ever thought I would (yes, I did order a tree anatomy textbook).

During this research, I discovered something else: Trees are incredibly efficient

How do trees optimize for growth and survival?

 While reading about the function of tree wood and bark, I discovered the principle of branch autonomy. As someone who values her autonomy over almost everything else, the idea that different parts of trees might have the ability to control themselves vs being controlled as one single organism piqued my interest. It transformed the way that I thought about trees to be more like a living society rather than one singular living organism.  

 This isn’t a perfect analogy, but it helped me understand how different parts of a tree function independently in some instances but as part of the greater whole in others.  

 Before we jump into just how efficient trees seem to be, let’s talk a bit more about this whole autonomy thing.

What is branch autonomy theory?

As long as light is the limiting factor observed… after its first year, a branch will not import carbohydrates from the parent tree and will satisfy its own energy requirements almost completely independently from the parent tree (2).

In simpler terms, branch autonomy is the idea that a branch on a tree can function independently from the rest of the tree.

To better understand this theory, plants have been observed under normal conditions as well as while under stress. A branch’s ability to function independently from the rest of a tree has also been observed in relation to various resources: carbon, water, and nutrients. (1)

What does this have to with efficiency?

“Branch autonomy might limit the damage that a localized stress or injury might do to the plant as a whole” (1).

 Having worked at a few tech start-ups, I’m familiar with constant shifts in priorities. The original “big” product(s) that we were once focused on, no longer have the same results and there are new ideas and products that we need to shift our focus toward to grow.

Another example: In Creative Writing, we often say “kill your darlings.” This refers to the fact that sometimes there’s a particular piece of prose that you wrote, and you love it, but after reevaluating, you realize it is taking away from the story as a whole. So, you get rid of it and lean into new, different areas.     

It’s a similar situation for trees. Older branches become shaded and if the tree were to focus as much attention on those branches (which are more limited in resources) as it did to those which have access to more sunlight, it would lose out on growth potential. (1)

These optimizations are not as straightforward as I have outlined above. The autonomy of branches seems to differ between species as well as seasons (1), but the idea that this happens at all is fascinating.  

 This blog post has only lightly scratched the surface of the efficiencies of trees. In a future post, I’ll definitely go into how they heal. It also does not even begin to cover the nuances of branch autonomy and when this theory is applicable—and when it’s not. However, I thought it was such a fun idea to think about, especially as we constantly think about optimizing ourselves.  

(1)     DG Sprugel, TM Hinckley, W. Schaap

Annual Review of Ecology and Systematics, Vol. 22 (1991), pp. 309-334

https://www-jstor-org.ezproxy.sfpl.org/stable/2097264?read-now=1&seq=20

(2) DG Sprugel

Physiology, Volume 22, Issue 15-16 (2002), Pages 1119-1124

When branch autonomy fails: Milton’s Law of resource availability and allocation

https://doi.org/10.1093/treephys/22.15-16.1119

https://academic.oup.com/treephys/article/22/15-16/1119/1633838?login=false