DECAYING WOOD RECYCLING WITHIN ARBOREAL ECOSYSTEMS By Andrew Cowan N.D.Arb. – essentialARB issue 8 spring 2003
Dead wood may well have recently died, and no longer part of the living tree, or even attached to it, but we should not be calling it DEAD, because it’s DECAYING. You may think this is just another word for the same thing, but unlike Monty Python’s dead parrot sketch, the point is that dead wood is anything but dead. The description dead wood implies a static state, without the consideration for the process of decay, and the diversity of life forms involved.
It is the process of decay which is the focus here, the progression of use by different organisms. Some like their wood served up fresh with the sap still ebbing from it’s vessels, while there are those that prefer it when others have had their fill and all that is left is a mass of soft cellulose or brittle lignin. The diverse array of organisms that are involved in the breakdown of dead woody tissues is truly amazing. So much so that decaying wood can be considered a specialist habitat in it’s own right.
The figures are quite astounding, just considering the invertebrates that exist and depend on the decaying wood habitat, there are includes 1700 species in Britain, 6 % of total British Fauna, but the worrying fact is that 40 % are either British Red Data Book Species or labelled nationally scarce. In an effort to reduce potential losses, the JNCC* and RSPB** produced a practical handbook called ‘Habitat Management for Invertebrates’, which was republished in 2001.
Historically, woodland managers have removed dead wood on the basis of hygiene, to protect the timber resource from what have traditionally been perceived as pests, like insects and fungi. This is also true of many, parkland and garden sites managed by arborists, where dead wood in trees is seen as a liability, and is removed for fear it may fall and injure someone. The result is that there is simply not enough decaying wood habitat to sustain populations of many key species of conservation importance.
The recognition that decaying wood habitat is a dynamic system of processes, which are a constantly evolving part of the arboreal ecosystem, is an important step towards its successful and sustainable management. It is also a demonstration of how the terms we use can influence our perception of the management objectives. Our role as arboricultural managers is one of careful guidance, to encourage and support natural processes, not to impose a physical form or state to fit our ideas of what is right.
We must strengthen our recognition for the fact that trees live within a different time frame to us mere humans. Their living processes are almost the ultimate in sustainability, to a point where, in the right circumstances, they have the capability to attain immortality. A paper was recently published in the Arboricultural Journal (Vol.26 No.3 Sep 2002 pp 213-238) by Neville Fay called ‘Environmental arboriculture, tree ecology and veteran tree management’, which stresses the management impacts of tree life spans measured in hundreds of years, and in some cases millennia. The implications of this are that the component parts of arboreal ecosystems can undergo cyclic fluctuations, which are measured in centuries.