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Zidbits – Learn something new everyday! | August 1, 2014

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Do Trees Die From Old Age?

Do Trees Die From Old Age?

Trees usually die from disease and other outside environmental factors. This raises the question; can trees die from simply being too old? Today we’ll take a look at how old age affects trees.

Do Trees Die From Old Age?

The answer is a bit complicated, but yes. Trees do in fact die of old age. However, the term ‘old age’ is always a secondary cause. When a tree gets old, it has trouble protecting most of its inner heartwood and/or exterior. This means it cannot fight damage as well as when it was younger. The same can be seen in humans and most other animals – as we age, our immune system gets weaker and thus has a tougher time fighting off infections and protecting us.

Woody plants heal through by compartmentalizing the damage, sealing it off from the rest of the plant. This is called CODIT. This process happens in four steps, called “walls“. The process happens like this:

  • Wall 1: The tree blocks the transport tubes surrounding the wound, thereby preventing the wound/infection from spreading further.
  • Wall 2: The tree then builds a ring around the wound or infection to prevent it from spreading inward. This acts as a barrier providing further protection.
  • Wall 3: The tree then sections the wound laterally. This prevents the infection or wound from spreading circularly, keeping it from spreading left or right.
  • Wall 4: As the trunk grows, the tree’s new growth rings seal off the infection or wound. This prevents it from spreading outward into the new growth.

When a tree gets extremely old, it begins to lose this ability to compartmentalize and eventually causes the tree to die. Trees that still have leaves on them but their trunks are completely hollow is an example of wall 4 beginning to fail. Unless the wall 4 step has succeeded just in the nick of time, the tree will soon die.

CODIT example

Example of CODIT

Another common way trees die is by girdling themselves because they get too big, or something unpleasant gets sucked up in their roots which get caught in the phloem and xylem. It’s very similar to getting a piece of food caught in your throat. A tree can also eventually choke and die.

Girdling can also be caused by insects and animals. Most insects and animals only eat the newest part of the tree, where the phloem and xylem channels are active. This area is called the cambium. When this cambium is eaten, the tree has no way to pass nutrients or water up and down the tree. The tree eventually starves to death.

However, when a tree is extremely old, simple weathering is enough to pull the bark off a tree. This also damages the flow of water and nutrients. This is about as close as a tree can get from dying of old age.

Some of the largest trees species have no ceiling of growth (like redwoods). These trees can get so large that the atmospheric pressure prevents the tree from getting its nutrients and water from the roots to the leaves. This weakens the tree substantially and causes it to be a susceptible to a wide range of ailments. Most of which will kill the tree.

Comments

  1. BiologyExams4U

    Thanks for sharing. But I am bit confused about the term ‘old age’. Giant trees of hundreds of years old has meristems or actively dividing cells that ensures indefinite growth unlike animals. Secondly, the central region of wood are non conductive, but I think that is not a sign of old age. These regions has depositions (we call this region as heart wood which yields timber) and offers huge mechanical strength for these giant tress to stand firm.

    • TheWoodOre

      I think there is no real title as “Death from old age”. People don’t die from being old, they die from having their body be used up, which is usually when people are considered old.

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