Thursday, October 21, 2021

Branch Autonomy Theory

By thinking of a tree as an individual organism, we misunderstand it. It's better to think of a tree as a colony of branches.

According to the branch autonomy theory, "1) No branch imports carbohydrate from its parent tree after its first year, and 2) Each branch satisfies its own material and energy requirements before exporting any carbohydrate to the rest of the tree."

"The conclusion drawn from these postulates is that where light is the primary limiting factor, critical characteristics of the branch's carbohydrate economy such as photosynthesis, growth, and carbon export are largely independent of the tree to which it is attached." (from the abstract by Sprugel and Hinckley).

The theory is mentioned in a podcast interview with Chris Earle, curator of the Gymnosperm Database.


Roberto Quintana said...

Very good!
In addition to a colony of branches, each colony (tree) is also part of a much larger colony of trees in a local network of mycelium, or fungii, that shares resources and an exchange of (chemical) information with its local tribe. -RQ

James Gurney said...

Roberto, yes, I was going to mention the aspen mega grove or pando, but didn't want to confuse the issue. The element of time is also worth bringing up, since most trees have the capacity to live forever if properly cared for. The point is that we have to retool our imaginations if we want to understand the life of plants.

arenhaus said...

It's also confirmed by genetic studies of trees. A large tree does not have a single genome; it is a bundle of diverging clones, to the point where different branches form, literally, a genetic descent tree.

It's even truer for some trees than others, too. Olives, for example, are less of a single tree than a bundle of sticks which got fused together. It's not uncommon for an old olive to be only partly alive, with some branches still producing leaves and fruit and some dried up.