Small yet mighty, these vibrant hubs of life are essential for biodiversity. Peek into the miniature worlds hidden within our trees.
Tucked away in trunks and branches, tree-related microhabitats are tiny sites of life that play a vital role in healthy woodland ecosystems. From rotholes housing rare bats and beetles to pockets of rainwater teeming with micro-crustaceans, these fascinating little worlds provide food and shelter for thousands of specialised species.
As you might imagine, a tree-related microhabitat is a small-scale habitat supported by a tree. Examples include broken branches, sap runs and woodpecker holes, as well as nests, mushrooms and ivy.
We are only just beginning to understand the importance of these often-overlooked features. Thousands of weird and wonderful species depend on these important refuges, many of which are highly specialised animals, plants, lichen and fungi. The hoof fungus, for example, supports around 600 species of arthropod (a group of animals including insects, spiders and crustaceans), while the endangered hermit beetle can only survive inside a decades-old rothole and will almost never leave this snug sanctuary throughout its life.
Credit: Ben Lee / WTML
Microhabitats are the secret to woodlands that thrum and pulse with life. From pollinating plants to decomposing deadwood, every species plays a unique and important role in the woodland ecosystem. Each of these species has different needs, so a wood brimming with a diverse range of microhabitats can provide refuge, breeding, wintering and feeding spots for a wonderful array of woodland wildlife.
Credit: Hermann Brehm / naturepl.com
Some of these unique habitats can spring up in an instant – for example, a rock falling on a tree might cause an injury, or a lightning strike could leave a scar, creating the perfect conditions to support specialised organisms. Other causes might be colonisation by fungi, the chiselling away of wood by a woodpecker, or a forest fire. Some microhabitats, such as rotholes, can take decades to form and are very difficult to replace once we lose them.
Only the oldest and thickest trees develop many different - or even all - kinds of microhabitats. So the older and larger a tree grows, the more valuable it is to the woodland ecosystem. For example, a study of pedunculate oaks found that less than 1% of the trees under 100 years of age had cavities, while all of them had cavities at the age of 400.
Based on work by the Swiss Federal Institute for Forest, Snow and Landscape Research, there are more than 50 different types of tree-related microhabitats. These are split into seven main categories, which are
Credit: Alamy / Rebecca Cole
A bird with a built-in jackhammer, the woodpecker uses its chisel-like beak to carve holes out of tree trunks. Sheltered from the elements, these little homes offer a warmer microclimate that is perfect for keeping young chicks cosy . Abandoned cavities are snapped up by all manner of opportunists, including bats, birds and dormice. The faeces, food and carcasses these animals leave behind provide nitrogen for hungry invertebrates.
Woodpeckers often excavate their breeding cavities in the tender wood found just below fungal fruiting bodies. These fungal canopies shelter the entrance to the hole, a little like an awning! This is a mutually beneficial arrangement, as woodpeckers can help to carry fungal spores to new trees.
Credit: Alamy / ImageBROKER / Farina Grassmann
These are hollows or pockets in trees where rainwater collects, creating small pools in which teeny-tiny life forms flourish. There are 15 dendrotelm-dwelling insect species in Europe, half of which can only survive in this specific microhabitat. Peer inside and you might spot micro-crustaceans which also rely on these secluded woodland oases. The inhabitants of a dendrotelm mainly feed on nutrients from decomposing leaves. From time to time, amphibians might drop by to moisten their skin.
Credit: Alamy / Yon Marsh Science
Have you ever seen a tree with a charred, spiralling scar along its trunk? When lightning strikes a tree, its bark can fissure and crack, while the wood inside splinters. These lightning scars often have such a variety of characteristics that they can support an array of different animals within the same split trunk: look a little closer and you might find spiders, snails, slugs, bats and birds sheltering within.
In commercial timber forests, trees are often cut down before they have a chance to age and decay, resulting in a shortage of old trees with special microhabitats in these woods.
Elsewhere, the UK boasts thousands of ancient trees with special microhabitats, more than many countries in the rest of Europe. But most of these extraordinary trees are not legally protected. To be able to care for them, we first need to find out where they are.
Identifying where ancient trees are helps us give them the care and protection they need. Add your records to the Ancient Tree Inventory so we can locate ancient tree hot spots, monitor threats and plan how best to conserve these living legends for future generations.
We can only protect the ancient and veteran trees we know about.
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