Dead or alive? Bark or trunk?
Check out these 3 pics. Which of the 3 trees do you think are still alive?
The first tree is dead. You know it's dead because there is no more vegetation growing on it, no leaves, no moss, nothing.
The second and third trees are still alive, despite missing large sections of the tree trunk
As it turns out, the bark of the tree really matters in its survival. Notice how the first tree has no more bark, but the second and third ones still do.
Simply speaking, the bottom of the tree - the roots - absorb water from the ground.
The top of the tree, the leaves, photosynthesize to produce food(sugars) for the tree.
The trunk is responsible for transporting water from the roots up to the leaves.
But the bark is what transports the food produced by the leaves down to the roots.
As long as a small bit of trunk remains, the tree can still survive (if the tree is standing it obviously still has some trunk). This applies even if the trunk is mostly hollow, as in pics 2 and 3.
But if there a gap in the bark of the tree, there is no way for the food produced by the leaves to reach the roots, and the tree dies.
In fact removing a ring of bark, or girdling, is a technique used to kill trees.
This is sometimes inadvertent; girdling is used to make fruits sweeter, by concentrating the food produced in the top half of the tree. However, if there is no continuous run of bark from top to bottom, the price of sweeter fruits is a dead tree.