What happens to old trees? The oldest tree is over 5,000 years old. Why is it so long-lived?

Currently, the oldest known tree in the world is a Great Basin bristlecone pine in California's White Mountains, which is believed to be more than 5,000 years old.

The foxtail pine is one of the world's most famously long-lived trees, along with the ginkgo, breadfruit, giant sequoia, and many more, which are often found to be over 1,000 years old.

So the question is, do these thousand-year-old trees show signs of aging, or do trees die of aging? If not, why is the oldest tree only over 5,000 years old?

Do trees age?

As we age, some simple tasks may become increasingly difficult for us humans to complete, and more and more wrinkles may appear on the surface of our skin to show that we are really old.

Apparently, our bodies have a mechanism of gradual wear and tear that causes them to gradually malfunction, a process known in biology as aging.

Aging is not just superficial; it occurs at the cellular level, and its essence is that the cells in our bodies stop dividing, or divide more and more sloppily.

If we want our bodies to function properly, we need cells to continue dividing normally to replace those that retire and break down, but this function becomes limited as we age.

It is now known that the reason our cells fail to divide normally over time is that the telomeres at the ends of our chromosomes shorten with each division.

Telomeres are a bit like a "shield" that protects genes and prevents problems from occurring during replication. However, they wear out a little each time they replicate until their protective function is lost, and aging occurs.

Tree cells are very different from ours. Most plant cells are permanently in an embryonic state, which means they are able to keep the ends of their chromosomes the same length throughout their lives. At the same time, these cells can also transform into another cell type at any time to replenish or repair different damages.

In other words, in theory, trees do not age as we conventionally understand them, at least not on the time scale of human lifespan.

However, this does not mean that a tree can grow forever.

What happens when trees get older?

Before we go any further, we need to understand the fact that no living thing, whether plant or animal, actually dies of old age, and aging is not actually a scientifically recognized cause of death in humans.

As animals, when we die of old age, it's from age-related diseases like pneumonia, flu, cancer, or liver failure.

It is indeed difficult for trees to experience aging as we understand it at the cellular level, but they also have their own signs of "aging", and they can also die from "complications" of their own aging.

A sign that trees are "aging" is that they grow faster, which is a bit counterintuitive compared to the fact that our cells stop growing, but it's true, except that they don't grow upwards, they grow sideways.

The properties of tree cells mean they can keep growing, but some physical properties of the earth and the mechanical structure of the tree itself limit their growth.

The most important limitation of Earth is the effect of gravity. When a tree reaches a certain point in its growth, it will not be able to transport enough water from the roots to the top, thus preventing adequate photosynthesis.

At this point they reach a height limit, which varies from tree to tree.

Surprisingly, however, once trees reach their maximum height, they expand outward at an even faster rate. This surprising finding was reported in 2014 in the journal Nature[1] by a team that examined the growth of more than 700,000 trees around the world.

When trees start growing faster, another limitation comes into play - the mechanical structure will not be able to maintain a stable structure as the tree grows.

For a growing tree, they not only have construction costs, but also maintenance costs. As the trees become larger, their maintenance costs will also increase, which requires more resource quotas.

(This maintenance cost includes resistance to some diseases, repair of damage from insect invasions, natural disasters, etc.)

As trees continue to grow, the cost of maintaining them increases, inevitably to the point where the cost of trees is far greater than the resource.

At this point, the tree will most likely die from its own continued growth.

What do trees gain from their longevity?

In fact, trees have made many improvements to achieve longevity, not just the cellular level we mentioned earlier.

There are similar cases of "immortality" at the cellular level in the animal kingdom, such as lobsters. They possess an enzyme called telomerase, which prevents telomeres from shortening during cell division, so lobsters are theoretically "immortals."

However, lobsters die of old age in the same way as trees do. If a lobster is never eaten by a predator, it will die from being unable to shed its shell.

The ever-growing body requires constant shell replacement to accommodate it. As the lobster grows, when it reaches a critical value, the resources required for molting will exceed the energy they obtain.

For lobsters, this critical point will come very quickly, perhaps in dozens or hundreds of years, but trees obviously exceed this time scale.

That’s because trees have some unique innovations when it comes to staying longer.

For example, both above- and below-ground parts of trees can be directly replaced with those parts that are not viable, lost, or damaged, with or without trauma;

Another example is the formation of clones, which use a fan-shaped vascular system to allow a part of the tree to survive alone, without the entire tree having to survive;

In fact, there are many longevity adaptations that are unique to trees. If you learn about them, you will be surprised.

The result of all these efforts is that trees can live very long and remain able to reproduce.

Therefore, it is not difficult to find that the evolutionary mechanism of longevity is largely for the purpose of obtaining more offspring.

Pictured: The oldest tortoise is believed to be 190 years old

The turtles we are familiar with are also very long-lived. Their lifespan is disproportionate to their body size. This is actually closely related to the turtles' desire to have more offspring, because the survival rate of baby turtles is really worrying.

at last

The limits of lifespan vary greatly between different trees, and those that are truly long-lived are difficult to observe using our human lifespan scale.

However, it is rare that a tree will actually reach the end of its lifespan, because the longer they grow, the greater the chances of them encountering risks such as natural disasters and insect pests, which can destroy them.

This is also why, although trees are "immortal", the oldest trees we have discovered today are only more than 5,000 years old.

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