Nature on our doorsteps: Tree Hollows

Rosaleen Dwyer is the County Heritage Officer at South Dublin County Council – every week she gives us an insight into nature on our doorsteps and the beautiful biodiversity of its plants and wildlife.

NATURE will always try and fill an empty space.

Wherever a little room opens up in a habitat like a woodland or meadow, species are ready to move in quickly to grow and reproduce.

This will also happen if a space opens up in the bark of a tree.

This might happen following damage caused by a grazing animal, by people, by high winds, or by a lightning strike.

When an opening forms, rain begins to get directly into the living wood. If the spores of a fungus land, these grow and begin to feed on the wet wood.

Beetles also arrive and burrow deep, feeding on the wood and carrying the fungus even deeper into the tree.

A small area of damage can thus become a hole that reaches deep into the tree as the wood rots.

These holes can affect the health of the tree.

They can weaken the branch or the trunk and cause it to break away, exposing more of the inner wood.

Rot holes can, however, be interesting places for a range of other species that might be looking for a place to live.

If the hole fills with rain, and if it becomes lined with leaves, a permanent layer of water and rotting matter can form in the bottom of the hole.

These muddy layers are great places for microscopic single-celled animals, for tiny springtails, and the larvae of certain insects.

They can grow safely, free from predators, as they feed on the nutrient-rich rotting organic matter.

These wet organic layers are also great places for seeds to land and germinate.

Sometimes the most unusual plants will take root and can be seen growing out from these wet holes.

Other rot holes may stay dry, and these places can be great nesting locations for birds, squirrels, insects, spiders, and even roosting bats.

So, even holes in trees can be important areas where biodiversity can grow and thrive.