What happens when a tree is cut down?

As mentioned in the previous post, trees are like icebergs: a significant amount of them is underground. And from a tree’s perspective, this hidden root system is more important than the leaves and branches.

The first thing to understand, then, is that when a tree is cut down, it is not dead. The roots are still alive, and they can and will regrow. For thousands of years, it has been a common forestry practice to cut down trees, let them regrow, and then harvest them again. This technique is called coppicing.

However, a tree faces two challenges in regrowing. First, it starts out with no leaves, and thus no capacity to produce food for itself through photosynthesis. It must regrow using the energy already stored up in its roots. Second, the tree must grow new leaves and branches from its remaining aboveground surface area. This means that the closer to the ground the stump is cut back, the harder it is for the tree to regrow.

This means that if a tree is seriously damaged in a storm, the best thing to do is leave it alone. As long as the roots are in the ground, the tree is still alive and well, and will grow back. Causing more damage to the tree by cutting back the remaining trunk makes it more difficult for the tree to regrow, and increases the chances that it will not survive.

The second thing that happens when a tree is cut down – assuming that it is immediately fed into a woodchipper, rather than being left to decompose into the soil – is that all the carbon that was stored in the tree is rapidly released into the atmosphere. A middle-aged tree might be holding one ton of carbon. Releasing this carbon contributes to climate change.

Finally, cutting down a healthy, mature tree can knock thousands of dollars off the value of a residential property, in addition to driving up utility bills. It’s wise to factor in these hidden costs when considering the expense associated with cutting down a tree.

 

How do trees protect themselves from falling over?

All living things behave as though they want to continue living. Plants use a variety of strategies to acquire resources and avoid hazards.

One hazard faced by plants – especially large, long-lived plants like trees – is falling over. Trees have three main strategies for avoiding this life-ending event.

The first, and most well-known, is that trees are able to move with the wind. By bending, instead of standing stiffly, trees are able to absorb the force of the wind without being harmed.

Being flexible, however, comes at a cost of structural strength. A large tree cannot have a flexible trunk, because it would not be able to hold itself up. Thus, trees employ a second strategy in parts of their structure that need to be strong. Over its lifetime, a tree learns which way the wind usually comes from, and strengthens itself in strategic locations. It does this by producing extra cellulose – the tough material that distinguishes plant cells from animal cells.

Finally, trees protect themselves from falling by tightly gripping the soil with their roots. Anyone who has ever tried to pull up a dandelion, or even a handful of turf grass, knows how tenaciously roots hold a plant in place.

A plant’s root system can be the same size as, or even larger than, the aboveground part of the plant. This provides a powerful counterbalance to any forces that may be trying to tip the plant over. Thus, when arborists say that a tree is unbalanced, they are just trying to scare homeowners into paying them money.

Even the healthiest, most structurally sound tree could fall over in a severe storm. Conversely, it is very rare for a tree to suddenly topple on a clear day. Overall, about 30 Americans a year are killed by falling trees or branches – a vanishingly small risk in exchange for all the benefits trees provide, even after they’re dead.

What is plant training?

Plant training is a method of teaching plants how they should grow.

Sometimes this is done merely to create a visual oddity, as in the “circus trees” of Axel Erlandson. In other cases, it is used for practical purposes.

In one fantastic and ancient example, people in northeastern India have for centuries been training tree roots to grow over rivers, forming living bridges. Closer to home, native peoples across North America trained trees to grow into bent shapes, to serve as markers for trails and important sites.

Plant training is also used in suburban yards. Commonly, vining plants are trained to grow up a trellis instead of sprawling across the ground. Some books on gardening in small spaces advocate training fruit trees to grow flat against a fence or wall, a technique known as espalier.

Training techniques can also be used to prevent woody plants from growing in undesirable directions. This is generally accomplished by pushing or pulling branches into a new position, and holding them there. For example, two branches growing too close together can be spread by pushing them apart and wedging a block of Styrofoam in between. Or, one branch can be pulled in a new direction, then held in place with a rope tied to some stakes. After some time, these supports can be removed, and the plant will remain in its new shape.

Plant training often does not involve any cutting. Upcoming posts will explore why cutting is ineffective in many situations.

How old is That Blog?

That Blog is one year old today! This seems like a good time to recap some key points.

In the 1600s, American settlers imported a plant known as old world meadowgrass, in order to use it as food for cows and sheep. Over time, the plant acquired the name of Kentucky bluegrass, and began to be used in a novel landscaping feature called a lawn.

Lawns, and bluegrass, spread all over the United States. However, the grass – adapted to the cool, wet climate of northwestern Europe – did not fare well in the hot South or the dry conditions of the West. This was unacceptable to lawn owners, who responded by showering the grass with fertilizers, pesticides, and supplemental water.

These treatments successfully encouraged the grass to grow. But the owners did not want the grass to grow, so they mowed it. This was detrimental to the grass’s health, so the owners gave it more fertilizers, pesticides, and water. And so the cycle went.

Some people, feeling that this was a waste of time, decided to give up their lawns and instead invite nature into their yards. As scientific evidence of the harms caused by lawns accumulates, cities and states have passed laws encouraging, or even requiring, alternatives to lawns.

Today, many people still have lawns, but a growing number do not. The purpose of That Blog is to provide information about lawns and their alternatives, in order to help people decide what kind of yard is right for them.

Are plants intelligent?

Humans, like other mammals, live life in the fast lane. Our brains are adapted to notice and react to things that change quickly: we find things that move and make noise to be endlessly fascinating.

Plants do neither of these things, so to us they seem boring, unintelligent, hardly even alive. Cavemen, it turns out, didn’t bother to draw them.

But scientists are beginning to suspect that plants may have their own kind of intelligence. Three lines of evidence point to this conclusion.

First, it is reasonable to expect that all living things are intelligent. Intelligence is expensive, biologically speaking, but stupidity isn’t adaptive. Stupid organisms don’t tend to survive. Any species that hasn’t gone extinct, therefore, is probably at least a little intelligent.

Second, plants have biological mechanisms that allow for intelligence. In humans, intelligence is driven by two main processes in the brain: electrical impulses, and the activities of a group of chemicals called neurotransmitters. Plants have both of these processes – and not only that, but they have many of the same neurotransmitters that humans do.

Third, plants behave as though they’re intelligent. It seems strange to say that plants behave at all, because our fast-paced mammal brains can rarely detect them doing much of anything. Some clever scientists, however, have figured out ways to observe plants’ behavior. In one such experiment, plants reacted defensively to the surprising experience of falling, then learned not to react when repeated falls didn’t actually cause them any harm.

Plant intelligence would have to be very different from human intelligence, because plants face a very different set of challenges in life. However, increasing evidence suggests that plants are aware of what’s happening around them, and are able to react in ways that mirror what a human would do in a similar situation.