Fraternization Under the Forest Floor

In my first post on Peter Wohlleben’s The Hidden Life of Trees, I wrote a bit about the how certain hyphae–that is, the branching filaments that make up the mycelium of a fungi–play a key role in establishing the “wood wide web.” But perhaps you were left wondering, “Okay, but what’s in for the fungi?”

The Enlighted Entrepreneurship of Fungus

As it turns out, a lot. The fungi definitely take their cut of the sugar and other carbohydrates produced by trees. Indeed, they can take as much as a third of a tree’s total food production for services rendered. A third!

The IRS has got nothing on the fungi.

So, what do the trees get in return? Well, as we previously noted, they extend the reach of tree roots and allow trees to share not only nutrients but also information with one another. Let’s face it, that’s pretty good service. It’s as if our Internet provider was not only letting us exchange information but also allowing us to directly send food and water to one another.

But, as the Ronco people used to say, “And that’s not all!”

The beneficial fungi also provide certain medical benefits. Not only do they filter out poisonous heavy metals, they ward off bacteria and the more destructive types of brethren fungi.

But these tree-loving fungi are not dedicated to just one species of tree. They play the field, willing to connect trees of different species. Wohlleben writes, “Although many species of tree fight each other mercilessly above ground and even try to crowd out each other’s root systems, the fungi that populate them seem to be intent on compromise.”

In a way, the fungi are like a huge retail chain (think Amazon), helping many companies because betting on just one corporation could be disastrous if that corporation failed. Similarly, the fungi do not want to bet on just one species of tree because if some plague takes out that species, then they their fates are tied only that failing species. If a beech tree complains to that it’s local fungi should not also be helping their competitors the oaks, you can almost hear the fungi say, “Sorry there Beech boy, it’s not personal, it’s business.”

Plumbing the Mysteries of Trees

Not only don’t we fully grasp the complexities of trees, we don’t even understand a lot of the basics. One of those basics is plumbing. That is, how do trees pump water all the way from their roots to their crowns?

Wohlleben discusses two primary theories. First, there’s capillary action. Wikipedia defines the action this way:

[T]he process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces like gravity. The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper and plaster, in some non-porous materials such as sand and liquefied carbon fiber, or in a biological cell. It occurs because of intermolecular forces between the liquid and surrounding solid surfaces. If the diameter of the tube is sufficiently small, then the combination of surface tension (which is caused by cohesion within the liquid) and adhesive forces between the liquid and container wall act to propel the liquid.

Here’s how I think of it: when you put water in a narrow vessel, the water itself stands above the lip of the vessel. So, when you fill a glass of water to the brim, the water actually stands slightly above the rim of the glass due to capillary action. The narrower the vessel, the higher it stands.

Although I’ve noticed this before, I’ve never thought much about it. However, this action accounts for some of the rise of water up the trunk of a tree. How much? Wohlleben says 3 feet in a 300 foot tree. In other words, more than you might think but not all that much.

The second way trees pump water is transpiration. Wohlleben describes it thus:

In the warmer part of the year, leaves and needles transpire by steadily breathing out water vapor. In the case of a mature beech, the tree exhales hundreds of gallons of water a day. This exhalation causes suction, which pulls a constant supply of water up through the transportation pathways in the tree.

So, the tree uses suction, the same principle by which we drink our juice boxes. Which is very cool!

There’s just one problem with this transpiration idea. It doesn’t explain the mysterious rise of water in trees before the leaves emerge. In fact, water pressure is highest in trees before leaves open in the spring!

So, we can glibly toss around terms such as capillary action and transpiration, but they alone can’t account for what trees are doing in the real world. And, if we can’t even account for basic plumbing in trees, imagine how much else we’re missing.

Skin in the Losing Game of Life

Bark is the skin of trees. Like our skin, tree bark is constantly being shed. As with our skin, bark holds in life-giving water and protects a tree’s inner organs from the deadly world outside. As with our skin, bark wrinkles as the trees age.

The wrinkles aren’t the only things we share with trees. Like us, trees actually start to bald and shrink a bit as they get old. And, as with us, they finally succumb to entropy, and their bark begins to fail.

When it does, the non-beneficial types of fungi help bring about their demise. Wohlleben writes:

Small moist wounds have become portals for fungi to enter. The fungi advertise their triumphant advance through the tree by displaying magnificent fruiting bodies that jut out from the trunk in the shape of semicircular saucers that grow larger with each passing year…Then one day it’s all over. The truck snaps and the tree’s life it at an end.

And so the tree dies and eventually becomes part of the forest floor, feeding the roots of its competitors and children. Meanwhile, the fraternizing fungi below continue their work, taking in the big picture, ultimately seeing the forest for the trees.