Are Trees Parasites That Grow On Wood?

Introduction

I have asked myself for some time, “Are trees parasites that grow on wood? i.e. ectoparasites.” (An ectoparasite lives on the outside of its host.) Mainly this is because only the outer layers of a tree are alive. The inner part of the tree – the wood or timber – is dead. It was alive in previous years but in later years it is only the support for new growth. Consider all the old hollowed out trees: e.g. those hollowed out by wood rot. The outer layers continue to grow year on year. It is only when the outer layers are severed so that sap cannot get up the tree from the outer layers of the roots to the outer layers of the twigs with the leaves attached that the tree dies.

Are Trees Parasites That Grow On Wood?

I Found A Good Example

I have recently seen one of the best examples of tree growth behaving like an ectoparasite on the surface of wood in my local park (Alvaston Park, Derby, UK). You can see it here in these two pictures of a linden tree showing the front and back of the tree.

This one tree has two strips of living bark running up it. The front view shows quite a narrow strip running up it, and the view from behind shows a wider strip. The tree has been truncated at the top by the park keeper at some time.

The Oxford Dictionary describes a parasite as: An organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other’s expense. So on the strength of that description a tree is not a parasite since it isn’t taking nutrients from a living host at its expense (unlike mistletoe). The wood is dead.

I Found Another Example

trees parasites
An oak tree at Calke Abbey, South Derbyshire, clinging onto the remains of its old trunk.

In the picture above (taken 2017-11-06) you can see another example where the outer layers of an oak tree are being supported by the wood of the inner tree which is still standing. A large part of the original tree trunk has broken away in the past. The living part of the oak looks like a parasite on a dead tree.

Can Trees Be Transferred To Other Formers?

See my article of the same title: Can Trees Be Transferred To Other Formers?