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?
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.
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.
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?
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.
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 https://en.wikipedia.org/wiki/Root#/media/File:Kiental_entre_Herrsching_y_Andechs,_Alemania_2012-05-01,_DD_12.JPG