The Yggdrasil Effect

Without trees, our planet and our lives would be dramatically different. Indeed, given the fact our ancestors lived in trees, it’s certain we would not be here at all.

Trees do so much, in fact, that I think we can classify their impact as the Yggdrasil Effect. Yggdrasil, of course, is the immense and sacred tree of Norse mythology. The branches and roots of the great tree connect the various parts of the cosmos. Yggdrasil is not, however, in perfect health thanks to serpents that chew at its roots and stags that chew on its leaves. In short, the great tree–and therefore the cosmos itself–is mortal and under constant threat.

The Yggdrasil Effect highlights both the many essential functions of trees in our world as well as their essential fragility and mortality.

Pumping the World Up

According to myth, Yggdrasil has three major roots that it uses to pump water from three magic springs or wells, presumably pushing those waters to the rest of the cosmos. In real life, trees play a similar role. If it weren’t for trees, in fact, most of today’s dry land would be deserts.

You see, clouds form over oceans (where most of the water is, of course) and then those clouds float over nearby land, whereupon they unleash the rain they contain. Wohlleben writes. “If depended on just this mechanism for water, life would be possible only in a narrow bank around the edge of continents.”

So, what do trees do to pump water into the rest of the world? First, they spread their canopies over the land. After the rain falls, much of it remains in the canopies where it evaporates again rather than just running off back into the oceans. “In addition,” Wohlleben writes, “each summer, trees use up to 8,500 cubic yards of water per square mile, which they release into the air through transpiration. This water vapor creates new clouds that travel farther inland to release their rain. As the cycle continues, water reaches even the most remote areas.”

So, if you happen to live in a place is not near a coast but where you get a goodly amount of rainfall, you can thank the trees.

Altered Carbon

You may have heard that the world has a carbon problem. Global monthly average concentrations of carbon dioxide have risen from around 339 parts per million in 1980 to 412 parts per million in 2020, an increase of more than 20%. More carbon means more global warming, which means all kinds of bad stuff, including more frequent and devastating forest fires.

But as long as they are not being incinerated, trees are amazingly good at pulling carbon dioxide out of the air and storing it in their bodies. Even once the trees die, much of the carbon is stored underground as they disintegrate into the forest floor. Wohlleben writes,

It’s true that some of this carbon dioxide does indeed return to the atmosphere after a tree’s death, but most of it remains locked in the ecosystem forever. The crumbling tree is gnawed and munched into smaller and smaller pieces and worked, by fractions of inches, more deeply into the soil….The farther underground, the cooler it is….And so it is that carbon dioxide finds its final resting place in the form of humus, which continues to become more concentrated as it ages.

If we could just stop burning all the ancient carbon that is stored below ground in the form of carbon-rich fossil fuels, then eventually the trees could capture much of the carbon in the air and once again cool down our ever-hotter planet. It’s nice to plant more trees, of course, as a way of vacuuming and storing carbon, but it’s even better if we can leave the older trees alone to do their thing. The larger tree, the more quickly it grows in terms of total biomass, thereby sucking up more carbon.

Controlling the Climate (for Reals!)

Controlling the weather has long been a trope in the world of fiction. (Typically associated with carton villains: Simon Bar Sinister anyone?) In the real world, we haven’t gotten very far with weather control aside from some cloud seeding. On a larger scale, of course, there’s the climate, both global and regional. We’ve been affecting climate via our massive global bumbling with greenhouse gases, but this is a case where we’ve changed it for the worse for our own species (not to mention so many species).

Simon Bar Sinister

Trees, however, have a much better track record in this area, able to create their own climates, both macro and micro, for their own benefit. We’ve already discussed the macro aspect of pumping water all over the planet (which obviously serves the need of trees as well as humanity). But trees are also pretty good at affecting climate on other scales. Wohlleben provides the example for a little forest of beech trees.

With their annual leaf fall, the beeches created an alkaline humus that could store a lot of water. In addition, the air in this little forest gradually became moister, because the leaves of the growing beeches calmed the air by reducing the speed of the wind blowing through the trunks of the pines. Calmer air meant less water evaporated. More water allowed the beeches to prosper…

In short, the beeches became part of a positive feedback loop, helping to create an environment in which they could thrive. Now that’s an excellent case of climate control.

Beneath the Arms of Giants

Wohlleben also refers to tree-driven “microclimates.” When I read that, I could immediately relate. We have an oak tree in our front yard, which feels so different from our back yard that they might as well exist in separate dimensions. Whereas the front yard often feels cool and moist even in the heat of the summer, the back yard feels parched and blazing hot, especially in the summer. In the Florida winter, the temperature is somehow more moderate under the tree, a characteristic that made more sense when I learned, according to Wohlleben, that “trees sweat.”

Huh. So that’s why our cars don’t get frost on their windshields in the winter as they did when we used to parked them on a treeless corner in the same city. They’re kept warmer under the giant, radiating, sweaty tree. I’m not sure if that’s gross or comforting. Maybe a bit of both.

Of course, I was perfectly aware that parking under a tree is messy, though I never quite considered it was because trees shed bits of bark and sticks in the same way we human beings shed our skin (which is where so much of the dust in our houses come from–I know, ew).

In short, trees are literally the moist, smelly, sweaty, shedding giants in our midst, so big that they create the micro-climates in which we live. I suppose we know that at some level. On another level, however, we often tend to see them as inanimate things such fences, pillar, streetlights and the roofs of houses. Maybe that’s because we hold their lives in our hands. Viewing them as beings rather than things means we have responsibility for these giants on whom we so depend. It’s a lot of pressure. I suspect many of us would rather not think about it.

Note: This post covers some of the material in chapters 16 to 18 in The Hidden Life of Trees.
Featured image: The norns Urðr, Verðandi, and Skuld beneath the world tree Yggdrasil (1882) by Ludwig Burger.,_Werdanda,_Skuld,_unter_der_Welteiche_Yggdrasil_by_Ludwig_Burger.jpg

At the Roots of Stalwart Trees

Let’s get back to The Hidden Life of Trees. This post approximately covers chapters 14, 15 and 19.

To Be or Not to Be a Tree

Trees regularly defy our expectations. Sure, we know there are bonsai trees, the miniatures so carefully cultivated according to principles developed in Japan. But those are explicitly shaped through human artifice. They are to “normal” trees as Chihuahuas are to wolves (no offense intended to my Chihuahua cousins, since all a domesticated dogs are, to one degree or another, shaped through human interventions).

Short Tree Syndrome

But how about the dwarf birch found mainly in the tundra of the Arctic region? Is that, as the name implies, just a kind of bonsai shaped by nature rather than humankind? Nah, at least not according to the conventions of taxonomy, which considers it a shrub.

Okay, then, so what’s a shrub? Wikipedia says shrubs are distinguished from trees “by their multiple stems and shorter height, less than 6–10 m (20–33 ft) tall.” But I don’t think Peter Wohlleben quite buys it:

[I]f you were to apply the same measure to other trees, then small beeches or mountain ash wouldn’t count as trees either. These two are often browsed on so heavily by large mammals such as deer that they grow multiple shoots like bushes and hold out at a height of 20 inches for decades.

So, maybe this is just prejudice against smaller sizes extended into plant world. Ah, well, and Pluto is not a planet either. Science, apparently, believes size really does matter.

Just Don’t Call Me Stumpy

And then there’s the case of the trees that have been frequently cut down to the trunk so that the impoverished people of yore could harvest their wood without cutting down the whole tree, a practice called coppicing. The question that Wohlleben raises is whether “trees that have numerous bushy trunks or thick callouses at the base where periodic felling has encouraged a proliferation of growth” are trees or not. Another question: in cases where there’s a carpet of shrubby growth around a single trunk, are they still a single tree?

A coppiced alder stool after one year’s growth. Taken by Cat James 12 February 2005 in East Dean, Hampshire. Coppicing#/media/File:Coppice_stool2.JPG

It’s Not the Size of the Tree, It’s the Shoot of the Root

Maybe we’re putting too much emphasis on what pokes up above the ground and not enough on what’s underneath: that is, the root. Wohlleben suggests that root of the tree is, quite literally, also the root of its wisdom. That is, it’s where the tree’s “brain” may reside.

Brain, you ask? Isn’t that a bit farfetched? Possibly, but now we know that trees can learn. This means they must store experiences somewhere…the roots are the part of the tree best suited to the task…For there to be something we would recognize as a brain, neurological processes must be involved, and for these, in addition to chemical messages, you need electrical impulses. And these are precisely what we can measure in the tree….

So, is there a kind of brain somewhere in a tree’s root bulb? Perhaps. Maybe we should not judge a tree based on its height or its multiplicity of stems but by the content of its arboreal character.

Beneath the Surface

It isn’t just the roots of trees that are below ground. It’s the whole system that sustains them, and that they sustain. Wohlleben notes that “up to half the biomass of a forest is hidden in this lower story.”

Yet, it’s not just about sheer mass. It’s also about the diversity and quantity of things. He writes, “There are more life forms in a handful of forest soil than there are people on the planet. A mere teaspoon contains many miles of fungal filaments.”

The Menagerie of the Underworld

So, who inhabits a healthy forest floor? Well, mostly icky, brilliant Lilliputians doing wonderfully gross stuff.

For example, there are the Oribatida, aka, beetle mites; at just .04 inches long, they look like bulbous spiders with shortish legs. One species feeds on the sundry fragments of leaves and tree bark, while another sucks on fungi juice. Wohlleben writes that “they appear everywhere at the intersection of birth and decay.” Want to take stuff shed from trees and help turn it into soil? They’re your bug.

Oribatid mite with a visiting friendly springtail (6841930644).jpg
This was taken on a Scarlet elf cup mushroom.
Andy Murray
Creative Commons Attribution-Share Alike 2.0

In the photo above, you get a bonus photo of a springtail, which is a kind of hexapod. As with the beetle mites, different species of springtail eat different stuff. Some eat fungi, others eat plants materials and pollen, and some are meat-eating little critters dining on the likes of nematodes and rotifers.

Then there are the weevils, which Wohlleben decribes as teeny, weeny insectoid elephants without the ear flaps. As you can see by the photo below, that’s a fairly generous description of creatures that a lot of folks consider pests. The bottom line, though, is that the ones in the forests do some really useful work, boring holes in leaves and stems and the like.
Lixus angustatus
English: A weevil of the Curculionidae family.
Author Alvesgaspar

These little beasties, along with many others, are key to making good soil. Moreover, once you lose them, they do not come bouncing back. Wohlleben writes:

[T]he return of the teeny creatures can take a very, very long time…More than a hundred years ago, oak forests were planted on the Luneburg Heath on what had once been arable land….Even after [a century], there are still gaping holes in the species’ inventory, and this deficit has grave consequences for the forest, as the nutrient cycles of birth and decay aren’t functioning properly.

The bottom line that we’re still doing a crazy amount of damage of the environment and, even once (or if) we stop, it’ll take lifetimes before things get back to some optimal cycle. We need to be more careful with the world.

The Above Board Brutalizers

Meanwhile, trees must also cope with the menagerie above the root line. Maybe the first critters you think of are nesting birds, scurrying squirrels, perhaps the occasional momma opossum and her young, or the seeming endless variety of monkeys in South America.

Lovely. And fun!

But the trees themselves probably think harder about the hoards of animals that want to feast on them. Let’s start as the A’s.

A Is For Aphid (as well as Argh! and Ack!)

  • Aphids, aka, plant lice, aka, brutal little bloodsucking bastards. (It’s personal. I still hold a grudge based on what they did to my sunbeach flowers). These creeps are the vampires of the plant world but they’re also the cattle of the ant world. How weird is that?
Plate 2 from Insects, their way and means of living, R. E. Snodgrass.

Aphids are vampires because they suck all the lifeblood out of plants by digging their little fangs into the innocent veins of leaves and needles. Wohlleben explains.

The tree’s lifeblood rushes right through these tiny insects and comes out the other end in large droplets. Aphids need to saturate themselves like this because the sap contains very little protein–a nutrient they need for growth and reproduction. They filter the fluid for the protein they crave and expel most of the carbohydrates, above all, sugar, untouched.

Because they are basically pooping out big blobs of sugar water (sometimes called honeydew), certain ants adore certain aphids. Ants love honeydew so they’re basically farming the aphids, herding them around to the juiciest parts of the poor plants, protecting their pet vampires from predators, and even carrying them into their nests at night and/or for winter to protect them.

An ant guards its aphids
viamoi – originally posted to Flickr as ant aphids Uploaded using F2ComButton

B Is for Other Brutal Bugs

Aphids are just one kind of buggy brute. Among others are:

  • Bark beetles: You might say their bite is worst for the bark. The bark beetle seeks to literally move into the bark of weakened trees, aiming to devour the delicious and nutritious cambium, which is the growing layer between the bark and the wood. If they can squeeze in, the beetles grow their eggs close the cambium so the larvae can fatten themselves at the expense of the tree.
  • Caterpillars: When you’re a kid, you love caterpillars (awww, gonna be a butterfly). Later on, if you do any gardening, you start to loath them and their ilk (especially canker worms!). Trees also are not a fan. Caterpillars utterly devour their leaves and needles. Fortunately, the trees usually survive, even if they come in huge numbers. But if the caterpillars arrive en masse several years in a row, trees can weaken and die.
  • Gall midges and wasps: The larvae of these critters “reprogram” leaves with their saliva so that the leaves “grow into a protective casing or gall.” The casing holds the developing insects, who munch away till the leaves fall. Fortunately, this tends to do a lot less damage than the likes of bark beetles and caterpillars.

Kingdoms of Suckers and Sappers

Those that love to sap and suck at trees come from multiple kingdoms (the biology kind, not the Game of Thrones kind). We’ve already mentioned aphids, one of the prime insect types. Next, are birds in the form of woodpeckers. Losing sap can kill a tree just as losing blood can kill an animal, but woodpeckers seldom wound trees fatally.

Then there’s the fungi, especially the honey fungus mushroom, which forces itself into the roots of trees, where it sucks sugar and nutrients out of the cambium. Even fellow plants can get in on the act, and the pinesap is strange one. It doesn’t contain chlorophyll and so can’t photosynthesize. As a result, it can grow in darker places as it feeds on the flow of nutrients traveling between fungi and tree roots.

Just Don’t Call Them Dear

I’ve always thought of deer as woodland creatures but Wohlleben reminds us that “normally, they wouldn’t be living in the forest at all because they eat mostly grass.” The truth is that deer are associated with forests because human beings and their domesticated animals take up most of the grasslands. If they can’t get their fill of grasses in the nighttime hours, they’re forced to do desperate things such as eat the bark of of trees. When this happens, the damage can be so extensive that fungi creep into the wounds and weaken the tree.

Male deer can also harm or even kill young trees when the deer use them to scratch the itchy skin off their antlers before they shed them. Wohlleben notes, “The little tree’s bark is in such a bad state after this performance that the tree usually dies.”

The Stalwart Life

We often think of trees as calm, beautiful, even majestic. But I don’t think we give them enough credit for being almost miraculously stalwart. The scientists tell us that we animals are ruled by fight or flight instincts when threatened.

Well, trees can’t fly, or run, or even trudge. They have to stand and fight against, as we’ve seen, a wide range of foes. So, maybe we need a new poem that begins,

I think that I shall never see
a hero stalwart as a tree.

Running? Running’s for wusses. If you’re a tree, you literally stand your ground, resisting and persisting for centuries at a time–even as generations of fast runners ultimately fall and die, nourishing the soil that sustains you.

Featured image: Tree with visible roots in Kiental, between Herrsching and Andechs, Germany, by Diego Delso,_Alemania_2012-05-01,_DD_12.JPG

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.

Note: In case you were left wondering, this post approximately covers chapters 9 through 13, though I can never quite keep myself from deviating beyond the confines of the text itself.