life bridging the gap logotyp

08. Dead wood

Despite its name, “dead wood” is full of life. Dead wood exists in many different forms and successional stages which replace one another over time. The length of these stages differs greatly depending on the type of wood – but also on the size of the wood, moisture level and sun exposure. Text: Jonas Hedin

Just like in a pine Pinus sylvestris, the inner part of an oak’s trunk contains heartwood. In the heartwood there are cells that no longer conduct water or minerals, instead they are filled with e.g. tannins. This means that the oak develops much more long-lasting wood than a tree that lacks heartwood. It can take centuries for an oak’s heartwood to decompose. Its sapwood, on the other hand, breaks down relatively quickly; after 10-15 years, most of the sapwood is consumed by fungi and insects. The wood decomposes in several successional stages, each with different species communities. Old oaks contain large amounts of dead wood and an enormous variety of habitats. For this reason, it is important to manage your old oaks so that they can survive as long as possible.

A diversity of dead wood

In order to assist species with specialist requirements, it is important to know which species live in the dead wood in the area you are managing. In large areas it can be possible to create different types of dead wood, while in smaller areas you should use what is most suitable in that particular location. The fauna of insects that live in standing dead wood is distinctly different from those that live in fallen dead wood. Therefore, it is important to save both types of dead wood. Fallen trunks should not be cut up, because intact trunks have a more natural moisture gradient, which is important for wood-decay fungi and insects.

Trunks cut up into three-metre lengths are of considerably less value. It is natural for trees to be blown over in storms, creating valuable habitats – because of the dead wood itself, but also because of the open space and the ground upheaval that occurs. If such wind-felled trees have to be moved, ensure that the trunks are taken to a designated dead wood pile.

Damaging living trees is a suitable measure because over time, it often leads to a continuous supply of dead wood. Other methods include partial or full ring-barking, or felling entire trees and leaving them in place. If this obstructs grazing, the branches from the crown can be placed in a pile close to the trunk.

For the conservation, management and restoration of oak-rich woodlands and tree-covered pasture, there are a number of things to keep in mind when it comes to dead wood.

  • Aim for a diversity of dead wood. If possible, conserve all the naturally occurring species of trees in your area.
  • The dead wood should be both small and large, both standing and fallen, and in both sunny and shaded locations.
  • Aim to have dead wood in every successional stage, at least in the long term.
  • Keep all hollow trees.
  • Retain natural wind-fallen trees.
Dead wood at Valje Nature Reserve. Photo by Robert Ekholm.
Fallen hollow oak tree with wood mould and jackdaw’s nest. Photo by Nicklas Jansson.
Several piles of small dead wood were saved during clearing. Photo by Carina Greiff.

Things you can do to increase the amount of dead wood

  • Veteranise, if there are suitable trees. See chapter on veteranisation.
  • Ring-bark trees, partially or fully, and preferably at a tree’s distance to paths and roads.
  • Identify locations for dead wood piles, and place dead wood from trees felled locally there. For endangered species reliant on fallen trees, it may be necessary to enrich a protected area with really large dead oak wood, which can last for centuries.
  • If necessary, standing dead trees can be created by an arborist or woodland harvester. But remember that a tree that has died and remains in place contains many more habitats.
  • If deciduous trees have been felled in an area containing stag beetles, it might be a good idea to create a stag beetle pile. See the chapter on stag beetle piles.
  • It is much better to create small amounts of dead wood continuously, than a large amount on one occasion.
  • Piles of branches and tops can become deathtraps for wood-living insects, if the piles remain over the summer: female beetles can lay their eggs in the wood, which later gets chipped. So, plan your management such that felling and clea- ring is done after August 1, and chipping is done before April 1st.

In restoration and ongoing management, by always being mindful of the wood that is dead but very full of life, it is possible to create a large variation in habitat, and consequently also a landscape very rich in species.