Deadwood Is Alive

Walk through any well-managed broadleaf wood in Britain and you will find it: a fallen bough half-sunk in leaf litter, a lightning-split oak still standing, a mossy stump with a hollow at its heart. To the tidy eye it looks like neglect. To the ecologist it looks like the single most valuable habitat in the wood.

Deadwood is not waste. It is a slow, spreading larder and apartment block for thousands of species, most of which never appear in field guides because they spend their whole lives inside the wood. Around a third of woodland wildlife in the UK depends on decaying timber at some stage, and a single mature oak can support over 400 species of invertebrate, many of them found nowhere else.

A Home for Insects and Invertebrates

The technical term is saproxylic — literally "dwelling in dead wood" — and it covers beetles, flies, moths, wasps and a great many others. They are not all feeding on the wood itself. Some eat the fungi that rot it, some eat each other, and some simply need the damp, stable microclimate inside a decaying log.

• Stag beetle larvae spend three to seven years underground in rotting oak or ash stumps before emerging for a few summer weeks.
• Lesser stag beetles and noble chafers favour the softer, crumbly heartwood of old trees, including orchard trees such as apple and cherry.
• Deadwood beetles like the oak click beetle and the bright green click beetle relatives found in shaded log piles are highly sensitive to drying out.

Sun-exposed deadwood in a hedgerow or woodland edge supports a completely different community from the cool, damp wood on a north-facing slope. Variety of situation matters as much as quantity.

Fungi: The Forest's Recyclers

Nothing rots without fungi. Threads of mycelium push into the timber, breaking down lignin and cellulose and converting a fallen trunk into something other plants can use. The results are visible above ground as brackets, crusts and caps.

Two broad groups are at work. Saprotrophs feed only on dead tissue, producing the white rots that leave wood pale and stringy and the brown rots that leave it crumbly and cube-shaped. Parasites and weak pathogens, such as honey fungus, colonise living trees and can hollow out a trunk over decades.

This hollowing is not automatically bad news. A hollow veteran beech or sweet chestnut can stand for centuries, and the heart rot within it is precisely what makes the tree valuable to bats, owls and nesting birds. For the forager, deadwood fungi are also worth knowing: shaggy ink cap, chicken of the woods and beefsteak fungus all appear on stumps and fallen timber. Take only what you can identify with certainty, leave the mycelium undisturbed, and never strip a bracket fungus from a tree that is clearly providing habitat.

Birds, Bats and Other Lodgers

Standing and fallen deadwood is the structural backbone of woodland bird life.

• Great spotted woodpeckers chisel nest holes into soft, decayed trunks, and those holes are later used by starlings, nuthatches and stock doves.
• Lesser spotted woodpeckers, now desperately scarce, need fine-branched dead limbs for foraging.
• Treecreepers nest behind loose bark on standing dead trees, while marsh tits cache seeds in soft dead branches.
• Bats — barbastelle, Bechstein's, Natterer's, lesser horseshoe — roost in cracks, crevices and hollows in dead or dying timber.
• Dormice nest in hollow stumps and log piles, and hedgehogs, toads and slow-worms overwinter under damp wood at ground level.

Standing Dead Trees and Veteran Trees

A standing dead tree — often called a snag or monolith — is worth far more than its timber value. It offers decaying wood at height, in sunlight, above the damp of the forest floor, and it lasts for decades.

If you must reduce a dangerous dead tree near a path or boundary, consider leaving a monolith three to five metres tall rather than felling to the ground. Where a limb is decayed but the tree is sound elsewhere, a trained arboriculturist can reduce the crown and leave a stag-headed tree, which will continue to provide habitat while becoming safer.

Veteran trees of any species deserve the same respect. Ancient woodland indicators, rare lichens and specialised beetles are often concentrated in a handful of very old trees, so protecting them individually is more important than any general prescription.

Managing Deadwood Responsibly

Good deadwood management is mostly about doing less, more thoughtfully.

• Retain as much as you safely can. Aim for 20–30 cubic metres per hectare on a managed site, distributed across sun and shade, standing and fallen.
• Build log piles properly. One to two metres high, with the bottom logs in contact with soil, in dappled shade, and topped with brash to hold moisture.
• Leave brash after coppicing or hedge laying. Habitat piles of cut branches are quick to make and quickly used.
• Keep it away from people. Footpaths, car parks, play areas and boundaries need a tree safety survey by a qualified arboriculturist — risk assessment and ecology can coexist.
• Never move firewood long distances. Beetles, fungi and tree diseases travel in timber, so burn what you cut locally.
• Check the law before you cut. Nests, bats and some species are legally protected, and felling may require permission from the relevant forestry authority.

Treat deadwood as a crop rather than a mess, and a British wood will reward you with fungi in autumn, beetles in summer, woodpeckers all year round and a soil that keeps on building itself.