This article was republished by The conversation.
Trees can die suddenly or quite slowly.
Fire, flood or wind can cause rapid death by severely impairing the tree’s ability to transport water and nutrients up and down its trunk.
Sometimes a serious insect attack or disease can kill a tree. This type of death usually takes from a few months to a few years. Again, a tree loses its ability to transport water and nutrients, but it does so in stages, more slowly.
A tree can also die from what you might call old age.
I am a scientist who studies trees and the web of living things that surround them. The death of a tree is not exactly what it seems, because it directly leads to new life.
Different trees, different lifespans
Trees can live incredibly long, depending on what species they are. Some pine cones, for example, are among the oldest known trees and are more than 4,000 years old. Others, such as lodgepole pines or poplars, will have much shorter lives, from 20 to 200 years. The largest trees in your neighborhood or city are probably somewhere in this range.
You’ve probably noticed that different living things have different life spans – a hamster won’t usually live as long as a cat, which won’t live as long as a human. Trees are no different. Their lifespan is determined by their DNA, which you can think of as the operating system built into their genes. Trees that are programmed to grow very quickly will be less strong – and shorter-lived – than those that grow very slowly.
But even a tough old tree will eventually die. Years and years of damage from insects and microscopic creatures combined with the abuse of time will slowly end its life. The dying process may start with a single branch, but will eventually spread to the entire tree. It may take some time for an observer to realize that a tree has finally died.
You may think of death as a passive process. But in the case of trees, it is surprisingly active.
The underground network
Roots do more than anchor a tree to the ground. They are where microscopic fungi attach and act as a second root system for a tree.
Fungi form long, super-fine filaments called hyphae. Fungal hyphae can reach much farther than the roots of a tree. They collect nutrients from the soil that a tree needs. In return, the tree repays the fungi with sugars it makes from sunlight in a process known as photosynthesis.
You may have heard that fungi can also transfer nutrients from one tree to another. This is a topic that scientists are still developing. Some trees are probably connected to other trees by a complex underground network of fungi, sometimes called a “tree web”.
How the extensive tree network in the forest works is not yet well understood, but scientists know that the fungi that form these networks are important in keeping the trees healthy.
The afterlife of a tree
Before toppling over, a dead tree can stand for many years, providing a safe home for bees, squirrels, owls and many other animals. Once it falls and turns into a log, it can host other living things, such as badgers, moles, and reptiles.
Logs also contain a different type of fungi and bacteria called decomposers. These tiny organisms help break down large dead trees to the point where you would never know they were there. Depending on conditions, this process can take anywhere from a few years to a century or more. As wood decomposes, its nutrients are returned to the soil and become available to other living things, including nearby trees and fungal networks.
A tree leaves a legacy. While alive, it provides shade, a home for many animals, and a lifeline for mushrooms and other trees. When he dies, he continues to play an important role. It gives rise to new trees ready to take its place, shelter for a diverse array of animals and, ultimately, food for the next generation of living things.
It is as if a tree never really dies, but simply passes on its life to others.
Editor’s note: This story has been updated to emphasize that much remains unknown about the relationship between trees and fungi.
This article is republished from The Conversation under a Creative Commons license. Read the original article.