What is Dead Wood?
'one of the two or three greatest resources for animal species in natural forest' (Charles Elton 1966)
'Dead wood' is a broad term used to cover a wide variety of features mainly associated with mature and dead trees. There is a major distinction between long term features associated with live trees and short term ones associated with dead timber. The less common and more interesting species are generally associated with live, but over-mature trees. As a rule one species will only ever live in one particular micro-habitat so all types of dead wood are important for conservation.
Long-term habitats associated with live trees
The 'dead wood' fauna is undoubtedly richest in native broad-leafed species, especially Oak (Quercus spp.) and Beech (Fagus sylvatica). These are long-lived trees that decay slowly over centuries and provide stable conditions for some very rare highly specialised invertebrates and fungi. Key features are:
- over-mature hollow trees with heart rot, dead limbs, sap runs, rot holes and bracket fungi;
- ancient pollards also hollow and with heart rot;
- ancient coppice stools that are typically cut high and with heart rot.
Short-term habitats associated with dead trees
Once wind-blown or deliberately felled, timber begins a relatively short cycle of decay. Once in contact with the ground, and with hollow interiors exposed to the elements, conditions rapidly become unsuitable for many specialised invertebrates and fungi. Even large timber, such as entire tree trunks, can completely decompose within a few decades and need constant replenishment. Examples are:
- standing or fallen trees, branches and twigs;
- tree stumps;
- cut logs and log piles.
Why is dead wood important?
A once abundant commodity now virtually eliminated.
Deciduous woodland is the natural vegetation occurring in England. In a natural forest 'dead wood' habitats would have been abundant since the majority of trees would have been either over-mature or actually dead. Over thousands of years a very diverse community of species became dependent on this abundant commodity. This included many breeding birds and bats, numerous species of lichens and mosses and literally thousands of species of fungi and 'saproxylic' invertebrates. Invertebrates and fungi associated with dead wood habitats are typically poor colonists of new sites as they had no need to disperse.
Saproxylic invertebrates are those that are dependent, during some part of their life cycle, upon dead or dying wood or upon wood-inhabiting fungi or upon the presence of other saproxylics. The main interest lies in various beetle (Coleoptera) and fly (Diptera) families.
Today the majority of Britain's woodlands have been intensively managed for centuries. Both traditional coppice and modern plantation create relatively uniform stands of comparatively young trees with very little remaining dead wood habitat. Surviving woodlands tend to be highly fragmented and, following a local extinction event, there is little chance of a dead wood species re-colonising. Consequently, most specialist saproxylic invertebrates have declined substantially throughout Europe and some are now extinct. Today it is recognised that dead wood habitats and their associated species are an essential and natural component of a semi-natural woodland and are of great value to conservation.
