DEADWOOD HABITAT ACTION PLAN TECHNICAL APPENDIX

1 Preamble

Dead wood is those parts of the trees or shrubs where the trunk, branches, twigs or roots have died and become available as substrate for a variety of invasive organisms such as bacteria, lichens and fungi, making it more easily accessible for penetration by animals, both vertebrate and invertebrate, for breeding or shelter. The patterns of degradation over time provide a sequence of habitats which vary from large dry cavities in main trunks and large limbs suitable for nesting birds/mammals or summer roosts for bats, to a proliferation of microhabitats such as detritus and/or water -filled rot holes, assorted burrowings and detaching bark which host a very substantial invertebrate population of central importance in the woodland ecosystem.

In an unmanaged broadleaved forest such as that which covered most of Britain and Northern Europe, and the West Midlands in particular, after the retreat of the ice age some 10,000 years ago, around 17% of all the organic matter present is in the form of deadwood (cf. the extant Primeval Forest of Bialowiesa in Poland).

Our native flora and fauna largely evolved in such conditions and a very high proportion - about 13% - of our native invertebrate animal and fungus species have life cycles making them dependent on the dead wood environment at some stage during their development. In total, almost 5,000 British species are known to be associated with deadwood, but the true total is clearly far higher, as many species undoubtedly remain to be discovered and the life cycles of many others are unknown. Because the public are largely unfamiliar with these species, they are in most cases very poorly recorded, but they contribute enormously to our overall national biodiversity (compare the total known native British vertebrate fauna represented by 210 species of breeding birds, 48 mammals, 12 reptiles/amphibians and 38 freshwater fish). Because of their overwhelming importance in terms of biodiversity in this habitat, this Action Plan concentrates on invertebrates and fungi.

While some species of the deadwood community are relatively numerous and form a significant component of the woodland food chain; others are highly specialised, adapted to living in very specific and limited micro-habitats within the deadwood environment. Many of Britain's rarest and most endangered species are amongst the latter and are particularly susceptible to fragmentation or loss of habitat.

With the increase in human population, the deadwood habitat has been under pressure since prehistoric times, originally as a source of fuel and raw material for handicraft, more recently by a desire for tidiness and an, often exaggerated, perceived threat to public safety and security coupled with a lack of appreciation of its importance to wildlife. Harvesting of mature trees for timber rather than allowing them to mature, die and decay naturally has historically also had a major impact on the proportion of deadwood in woodland.

The habitat

Dead wood exists not only as completely dead trees, either standing or fallen/felled, but most importantly as a very significant component of mature living trees (particularly pollards and hollow trees) and may be in the form of:

• Dead sections of living trees, including bark, branches and twigs,
• Dead standing trees,
• Dead stumps,
• Dead fallen trunks, branches and twigs,
• Dead parts of tree roots,
• Rotting fence posts and other man-made wooden structures,
• Wood chips created during woodland clearing activities.

Within these general categories, a number specific primary micro-habitats can be recognised:

• Dry dead heartwood,
• Rotting heartwood,
• Under dry dead bark,
• Under wet rotting bark, particularly where fallen trunks/branches penetrate standing water
• (ponds & streams),
• In rotting stumps,
• In rotting tree roots - particularly within cavities filled with semi-liquid rot products,
• Rot holes (water or detritus filled), often in otherwise healthy trees.

Other secondary micro-habitats, particularly important for insects, are formed as a result of colonisation of the primary habitats by bacteria, fungi and other insects:

• Fungal bodies growing on standing dead trunks/branches,
• Fungal bodies growing on rotten fallen trunks/branches,
• Abandoned insect borings in dead wood,
• In social insect nests in dead trees,
• The living bodies of deadwood-dependent invertebrates - a significant number of insect species live as internal parasites of other insects/invertebrates,
• A significant number of insect species live as obligatory internal parasites of other deadwood-dependent insects/invertebrates.

Although technically not a true deadwood habitat, sap runs from wounds on mature and senescent trees provide an additional very rich habitat for a significant number of particularly scarce insect species in environments where deadwood abounds.

The Dead Wood Nutrient Cycle

This is eloquently described by Stubbs (1972), but can be summarised as follows. Dead wood is invaded by bacteria, fungi and other micro-organisms which initiate chemical change and produce nutrients (e.g. sugars) that invertebrates can consume. While some invertebrates (particularly beetles) directly attack the unaltered wood itself, others thrive on the bacteria and fungi and the wood they have altered. Still others depend on the bores created by their fellow invertebrates or bore into the softened decayed for shelter or nesting space. Many prey on, or parasitise other invertebrates or live as scavengers in their nests.

A significant proportion of the invertebrates become prey to vertebrates, particularly birds and bats, which are in turn parsitised by other invertebrates or consumed by larger predators.

Dung and dead bodies are returned to the soil where they join the decomposed remains of the original dead wood, creating a habitat for soil organisms. Ultimately, virtually all the deadwood biomass becomes nutrients for the development of new organisms.

Cut/felled timber

From the point of view of dead wood wildlife, there is very little difference between naturally fallen timber and cut/felled timber in the same location. Most species live in damp rather than dry dead wood, so tend to colonise the inner rather than the outer parts of stacked timber piles. Timber stacked in shade (i.e. within the woodland) is a much richer habitat than timber stacked in the open.

2 Associated species

Fungi

Fungus spores, carried in the air, are deposited on the wood. If they land on a suitable spot they will germinate and send hyphae into the wood, gradually softening it and breaking it down. Under suitable conditions, as yet not fully understood, fruiting bodies are produced which spread spores to new substrates. The fruiting bodies are the visible signs of fungal activity, but the mycelium, in the form of fine thread like strands through the deadwood, is always there, carrying out the decomposition of the wood. As the wood is broken down, suitable habitats are provided for invertebrates and their larvae. The fruiting bodies of the fungi themselves also provide habitats for some specialised invertebrates, which may lay their eggs on or in the fungus, or "graze" on the spore-bearing surface. The fruiting bodies of the majority of deadwood inhabiting fungi are rather small or insignificant (microfungi), but many are much larger and appear in the form of toadstools or brackets (macrofungi).

Invertebrates

Invertebrates dependent on dead wood at some stage of their life cycle include species of worms, snails, copepods, millipedes, centipedes, pseudoscorpions, spiders, mites and numerous insects. Many other groups of invertebrates, such as woodlice (Isopoda), are common inhabitants of deadwood, but also thrive in other habitats.

Many of the flying insects involved (e.g. hoverflies) spend their immature stages (egg, larva, pupa) in deadwood, but their adult stages (those familiar to non-naturalists) are found in a wide variety of habitats (e.g. at flowers).

Other species dependent on dead wood

This document addresses primarily invertebrates and fungi, which are relatively well known - even if poorly recorded, but it must be recognised that there are numerous representatives of other groups which are dependent on the dead or dying wood environment and which contribute to the overall biodiversity of the habitat. These include viruses, bacteria, mosses & liverworts (Bryophytes), algae, ferns & horsetails (Pteridophytes) and others.

Some vertebrates are also dependent or largely dependent on the presence of dead wood for survival. These include woodpeckers, which are predaceous on insect dead wood insect larvae, willow tits, tawny owls, nuthatches and several species of bats (particularly the noctule bat) which rely on cavities in tree trunks for nesting or roosting.

Numbers of Species

The following table, derived from the data sources listed in Appendix C, shows the approximate numbers of species of invertebrates and fungi recorded from Birmingham and the Black Country ("B&BC"). A total of over 1100 species believed to be associated with dead wood have so far been recorded, but this is likely to be a significant underestimate of the true total, since many groups are very poorly known and under-recorded. Appendix C contains a table summarising the conservation status of the dead wood invertebrates.

Table 1.1. Approximate Numbers of Invertebrate & Fungus Species associated with Dead Wood

* Includes a few species also associated with live timber and species associated with sap runs.
** Includes species recorded from the whole of Warwickshire

Appendix A: PRINCIPLES OF DEADWOOD MANAGEMENT GUIDELINES

• The most desirable management of woodland for the benefit of wildlife generally is to allow trees and parts of trees (trunks, branches, roots, etc.) to mature, die, fall and decay naturally without interference.
• Trees containing dead wood, particularly hollow trees and pollards, are not necessarily more prone to falling than other trees. Seek opinion of experts, taking into account the latest research data, before trimming/felling such trees.
• Careful pruning is always a preferable strategy to felling. Where cutting of dead/dying wood has to be undertaken, work should be planned in line with the following order of preference:

1. Trim/remove only individual branches, leaving other branches & trunk standing,
2. Remove as little of the trunk as possible, leave a stump standing as high above the ground as possible,
3. Never remove the stump and roots - always leave them to rot in place. Stump grinders should only be used in the most exceptional circumstances.

• Disposition of cut timber
  It is always preferable to leave timber to rot as logs on site, than to move it or chip it. The vast majority of dead wood species require moist conditions. Dead wood left lying or stacked in full sun sunshine quickly dries out. For this reason, cut timber should as far as possible be stacked in a shaded position. The bigger the stack, the more chance that a moist environment will survive in the centre of that stack. The preferred disposition (in order of preference) of cut or cleared fallen timber is as follows:

1. Wherever possible leave it lying where it fell (naturally or by cutting), especially if it is partly submerged in water (pond, lake or stream),
2. Move it to similar situation in shade nearby site of origin,
3. Stack cut timber in shaded position as close as possible to site of origin,
4. Stack cut timber in shaded position at a remote site
5. Stack cut timber in poorly shaded position close to site of origin,
6. Chip timber and leave it in piles in shaded position around sites of origin,
7. Chip timber and leave it in piles at in shaded position at remote site.
8. Chip timber and spread it evenly as close to site of origin as possible.

As an alternative to stacking cut timber, consideration may be given to securing it in a (near) vertical position by strapping it to an existing tree trunk or propping it against another tree or a bank etc..

• Security considerations
  Large logs are very difficult to move: stacked timber should be left in as large pieces as possible to prevent theft, unauthorised removal or dispersal.
  
• Public safety strategies
  Where public paths pass close to old or important trees regarded as posing a potential risk of falling timber, strategies other than felling should be considered in order to preserve the habitat. These would include:

1. Propping the suspect limbs/trunks,
2. Moving/rerouting the paths away to a safe distance,
3. Preventing/limiting public access by fencing, or hedges/boundaries of suitable plants (hawthorn, bramble, etc).

Appendix B: CONSERVATION STATUS

The British Red Data Books provide an assessment ("RDB category") of the rarity and vulnerability of most (the better known) species of insects (Shirt, 1987) and fungi. The reader is referred to those publications for a full definition of each category.

Table B1.1. Red Data Book categorisation of the Timber-Associated Invertebrates

Appendix C: DATA SOURCES

Invertebrates (Compiled by M.J. Smart & M. Bloxham)

The invertebrate species counts in tables 1.1 and B1.1 were derived from a following sources:

1. The total number of British species in each group was obtained by counting the number of species on the RECORDER database. The figures for Diptera and Hymenoptera were adjusted to correspond with those published by Chandler (1998) and Gauld & Bolton (1988) respectively.
2. The counts of species in each group recorded in the B&BC area were derived from data in the EcoRecord database maintained by the WT.
3. An draft list (in preparation for publication) of the British invertebrate species believed to be associated with living and decaying wood was made available by Dr. K. Alexander. Since only a few species are associated with healthy wood, that list was taken as approximating the total British dead wood invertebrate fauna and used directly to derive the total British dead wood species counts.
4. The individual species lists used in (2) and (3) above were combined to generate a list of dead wood species recorded from the B&BC area.

Fungi (Compiled by W. Moodie & D. Antrobus)

Counts of overall numbers of British species and those known to be associated with dead wood were derived for each systematic group using a variety of published reference works. This has been compared with the published list of species recorded in Warwickshire (updated with some unpublished more recent data) to derive figures representative of the local area. It must be emphasised that records for the whole of Warwickshire are included, incorporating some areas not strictly within B&BC.

Data Source References

Alexander, K.N.A., An Annotated Checklist of the Invertebrates of Living & Decaying Timber. In press.

Cannon, P.F. Hawksworth, D.L. and Sherwood-Pike, M.A. (1985), The British Ascomycotina, an Annotated Checklist. C.A.B., Slough.

Chandler, P. (Ed), Checklists of Insects of the British Isles (New Series), Part 1 : Diptera, RES, London

Clark, M.C.C. (1980), A Fungus Flora of Warwickshire. British Mycological Society, London.

Dennis, R.W.G. (1978), British Ascomycetes. 2nd Edition. Cramer, Vaduz.

Dennis, R.W.G. (1995), The Fungi of South East England. Royal Botanic Gardens, Kew.

Dennis, R.W.G. Orton, P.D. and Hora, F.B. (1974), New Check List of British Agarics and Boleti. Cramer, Lehre.

Duncan, U.K. (1970), Introduction to British Lichens. Buncle, Arbroath.

Ellis, M.B. and Ellis, J.P. (1990), Fungi Without Gills, An Identification Handbook. Chapman and Hall, London.

Falk, S. (1999), A Survey of the Insects of Sutton Park, Birmingham. Unpublished Report.

Gauld, I & Bolton, B (1988), The Hymenoptera.

Grove, W.B. (1935), British Stem and Leaf Fungi. Cambridge University Press, Cambridge.

Henrici, A. and Cook, P. (1991), A List of British Aphyllophoroid Fungi. Keys, Newsletter of the B.M.S. Keys Group 5, 5.1.1 to 5.1.48.

Lister, A. (1911), A Monograph of the Mycetozoa. Second Edition. British Museum, Natural History, London.

Shirt, (1987), The British Red Data Books: 2. Insects. Nature Conservancy Council, Peterborough.

Sutton, B. (1980), The Coelomycetes. C.M.I., Slough.

Wilson, M. and Henderson, D.M. (1966), British Rust Fungi. Cambridge University Press, Cambridge.

Appendix D: DEADWOOD TERMINOLOGY

Technical terminology has been avoided as far as possible in the main text of this BAP. Nevertheless, anyone reading the recommended references will quickly come across such terms. A summary of the more common terms is given here to assist in understanding those references.

Appendix E: LIST OF CONTRIBUTORS

The Dead Wood BAP Committee

* facilitator & editor

Acknowledgements

The following people have contributed advice and assistance to the committee during the preparation of this document:

Biodiversity Action Plan for Birmingham and the Black Country © 2000

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