A sneak peek into the dynamics of our wooden friends
Though it may not seem obvious at first, our wooden friends are a lot like us. Before we embark on a social campaign to fight for equal rights for trees, let’s take a closer look at the nature of trees and forests, as investigated by Peter Wohlleben in his book The Hidden Life of Trees: What They Feel, How They Communicate – Discoveries from a Secret World.
First, trees are caring beings. A group of trees bunched together make a forest, something greater than the sum of its parts: forests provide a cool, moist microclimate and shield the trees in themfrom powerful winds that could snap a branch like a twig, so to speak. Though some trees have large crowns, they do not abuse their advantage to continue growing above the others; instead, they share resources through their roots, which extend twice as wide as the crown, ensuring that virtually all trees are connected, and through the fungal network that grows on their roots, completing the “wood wide web”. Consequently, photosynthesis is equalized so that all trees in the forest produce the same amount of sugar per leaf. Wohlleben calls this “social security”. Think of it like a tax system that distributes resources to keep the entire population successful: a sick or injured tree is not left for dead. Strangely, not even dead trees are left for dead. There are signs of living green material in what used to be the cambium, the living layer between the bark and woody centre, in the stumps of fallen trees. While the inner portion has rotted away to humus, the cambium lives on, kept on life support by the nearby trees in the forest.
Raising a child in the forest is no sappy business. Mother trees leaf out a strict upbringing by light depravation and resource limitation. Only 3% of the sunlight that hits the canopy filters down to the forest floor, and that amount is barely enough to keep the young sapling alive. Furthermore, its short little roots cannot poke around to find additional resources, so its diet is kept in check by its mother, forcing the tree to grow up straight as an arrow. The result is a 100-year-old sapling that’s “no thicker than a pencil and no taller than a human”, living in the shadow of its towering 400-year-old parent. All is not for naught, however, this young (and 100 years is quite young) tree has been growing tiny, dense, airtight cells that make it flexible against the wind, resistant to physical damage, and prevent fungal infections from spreading inside the tree. On the other hand, spoiled city trees that grow up alone in parks get all the light and nutrients they want, but they can grow to irregular shapes that will eventually collapse as the weight of the crown increases. Their large, inflexible cells can snap in high winds, and their air bubbles give fungi a chance to breathe while they chew away at their tasty, nutrient rich interior.
Though without a nervous system, trees have some of the senses. When giraffes feed on acacia trees, the trees release toxins into their leaves for self-defense and release ethylene gas to alert their neighbours to start producing toxins too. A gaseous compound can be detected by sensory receptors on trees? Something smells funny. When pine and elm summon specific predatory insects to attack the pests chewing on their leaves, they choose which compounds to release based on the taste of the saliva of those bugs. During the spring, when deciduous trees are getting ready to sprout their leaves, they wait until there are enough daylight hours (13 hr or more, in the case of beeches). How they can tell is not entirely understood, but it’s likely that leaf buds have solar cells that can detect light, protected behind a few layers of brown translucent scales.
If the fact that trees can taste, see, and smell does not stump you, perhaps an electrical system will. Oaks send slow-moving electrical impulses through their roots to tell other oaks to produce tannins in their leaves, a bitter compound that gets pests to dine somewhere else for the night. Before growing new leaves, trees also look for a warming temperature trend; that’s why trees do not suddenly grow leaves during a few warm days in winter. If they can identify a trend, it implies that trees have memory: they can compare the conditions now to what they used to be.
Finally, trees have personality. The decision to shed leaves in the fall and grow leaves in the spring is personal. Members of the same species located within arm’s length do so at separate times. To keep the leaves longer into the fall means to store up more sugar and energy for the coming winter, but at the risk of being damaged by fall storms, like an umbrella in the wind. To shed them early and play it safe means to withdraw the nutrients from the leaves by breaking down chlorophyll back to the tree, making it easier to prepare for the coming spring. Ultimately, that decision is made individually.
When our understanding of trees as complex living beings is more firmly rooted, the environmental movement to protect and rehabilitate forests will see even more support. It’s the responsibility of humans to protect life on Earth and the environments that allow life to survive, and trees fall into both categories: as individuals and as forests.
By Husein Almuhtaram
Please note that opinions expressed are the author’s own. They do not necessarily reflect the views and values of The Blank Page.