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Significance of Dead Wood for Biodiversity Conservation and Close to Nature Forestry Peter Zach, Ján Kulfan Institute of Forest Ecology, Slovak Academy of Sciences, Zvolen. This presenration is to show how fascinating the world around dead wood is and what we can learn from it.

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Significance of Dead Wood for Biodiversity Conservation and Close to Nature ForestryPeter Zach, Ján KulfanInstitute of Forest Ecology, Slovak Academy of Sciences, Zvolen

This presenration is to show how fascinating the world around dead wood isand what we can learn from it
definition read et al 2000
Definition (Read et al., 2000)
  • (1) deadwood – wood which no longer fulfils any function for the tree
  • (2) dead wood – wood that no longer contains living cells
  • (3) coarse woody debris – CWD –

an American expression which refers to dead wood with diameter of more than

2.5 cm

ecological significance of dead wood
Ecological significance of dead wood

In a forest ecosystem:

  • wood(together with soil) amounts to the most significant sources

of organic material and mineral elements

  • improves physical, chemical and biological properties of soils
  • retains water and keeps moisture and regulates the temperature, contributes to a formation of typical forest micro- and mesoclimates
  • provides habitat, nutritions or food to a variety of organisms, namely to obligate and facultative saproxylic species, some of which play an important role in its decomposition and mineralization (e.g. fungi, insects)
  • increases species richness (number of species) and diversity of organisms
  • limits the risk of soil erosion and stabilise litter on steep slopes
  • indicates a forest ecosystem quality (disturbace, exploatation)
decomposition of wood
Decomposition of wood
  • cellulose (40-62% of dry weight of wood according to tree species) – fungi, bacteria and a few insects are able to decompose (hydrolyse) cellulose
  • hemicelluloses (actice participation of xylophagous insects)
  • lignin (18-38%) – only highly specialised fungi, bacteria and some protozoans are most significant, but a very limited number of insects can also digest lignin with help of fungal and bacterial symbionts in their digestive tracts
  • secondary components (2-3%, starch, soluble sugars,etc.)

Concentrations of main mineral elements (μ in oak branches during the decomposition and mineralization process (Swift, 1977 in Dajoz, 2000)

from fresh wood to wood mould
From fresh wood to wood mould
  • levels of organic nitrogen are low in healthy wood, they rise in decaying wood and are the highest in wood mould (the same with nitric nitrogen, ammoniacal nitrogen)
  • the C/N ratio, which is very high in fresh (healthy) wood, gradually falls and is the lowest in wood mould
Chemical composition of wood without decay, decaying wood and wood mould in chestnut trees (Kelner, 1967 in Dajoz, 2000)
dead wood
Dead wood
  • provides one of the two or three greatest resources for animal species in a natural forest ecosystem (Charles Elton in The pattern of animal communities )
  • if removed the forest fauna is impoverished by 20% (Kirby, Drake, 1993)
  • In Central Europe every fifth to sixth beetle species depends on dead wood (Reiner, 1991)

Aromia moschata

saproxylic beetles as indicators of a forest ecosystem quality
Saproxylic beetles as indicators of a forest ecosystem quality
  • Why? Saproxylic beetles strongly depend on CWD and take important part in its decomposition, they are restricted to various niches and do not migrate long distances, they are rich in species and in specimens and include significant bioindicary species, they can be collected through non-destructive methods, remnants of beetles in old (even fossil) wooden structures can also be identified.
Key factors affecting diversity of saproxylic beetles : species richness and number of specimens of specialists
  • amount of decaynig wood – general factor
  • diversity of dead tree parts (habitat heterogeneity)

- number of dead trees of large diameter

- presence of all stages of decay

  • number of polypore species and fruting bodies
  • distance to the nearest suitable habitats – every species has lower limit of how scattered its substrate can be before its population collapse – this distance increases with the size of clear-cut or thinning area (links to isolation effects)
  • level of disturbance (forest exploatation – cutting, thinning the trees, and adverse affects) – larger clear-cut or intensively thinned areas cannot be recolonized by beetles
dead wood amounts in primeval forests
Dead wood amounts in primeval forests
  • there are differences in dead wood amounts between different types of primeval forests
  • primeval forests comparable in their site and environmental conditions show only minor fluctuations in their overall biomass (Saniga, 2001)
  • if a particular primeval forest is considered proportion of dead wood may vary greatly within it according to the developmental phase (aggradation, optimum, disaggregation)
  • 50-200 m3 of CWD in semi-natural and virgin forests (Albrechts, 1991)
  • Western Carpathians: Boky (56,5 m3/ha, 14,7% of the whole amount of trees), Dobroc 1998 (184-412 m3/ha, 20-34% Badin 1997 (246-433 m3/ha, 27-37%), Polana (182,8 m3/ha, 32,9%) (Korpel, 1997, Saniga M., 2001)
dead wood amounts in commercial forests
Dead wood amounts in commercial forests
  • they can be very low (none or up to 5 m3) as well as higher (over 100 m3 in extensively managed forests) and very high after disasters
  • sufficient amounts can be derived from observations made in primeval forests combined with the results of experimental studies using indicator species or indicator groups
  • sufficient amounts to stabilise populations of saproxylic beetles in commercial oak and spruce forests: 5-10 m3/ha in Germany (Ammer, 1994), but even some 30 m3/ha showed to be insufficient in spruce forests in Norway (Okland et al., 1996)
  • sufficient amounts for the same purpose in an extensively managed oak forest in Germany: 40 m3 /ha (5% of the amount of living trees) (Haase, Topp, Zach, 1998)
how to support diversity of saproxylic beetles and that of a forest ecosystem
How to support diversity of saproxylic beetles and that of a forest ecosystem
  • to increase proportion of semi-natural forests
  • to avoid monocultures everywhere where possible (conversion to mixed forests)
  • to save large-diameter trees (diameter more than 40 cm) in different stages of decay and to support the existence of „special trees“ with basal hollows in tree trunks everywhere where possible
  • to avoid extensive cutting over large areas, the same concerns extensive thinning of pioneer tree species
  • to monitor dead wood amounts in order to predict unfavourable trends in their development and to integrate this monitoring in regular forest inventories
monocultures of norway spruce
Monocultures of Norway spruce

A commercial spruce forest, Polana,

central Slovakia

or mixed fir beech forests
or mixed fir-beech forests ?

Badin nature reserve,

central Slovakia


Obligate saproxylic Coleoptera in a natural and extensively managed fir-beech forest (Badin, 1996-1997)based on catches in flight-interception traps

ancient oak tree
Ancient oak tree

Central Slovakia

Any log left in a forest would help to increase species diversity. Unfortunately, not all organisms can be supported this way.

Upupa epops, Polana, W. Carpathians.

Large forest areas have been lost in Slovakia in the past but, compared to Western Europe, this is not excessive.

Still some 2,000000 ha remaining...

Large-diameter logs in Konigsforst, Cologne, Germany.

  • avoidance of presence of dead wood by some foresters, landscapes owners and the public (forest hygiene, pests, easthetical aspects, risk to forest or park visitors, etc.)
  • fragmentation of ownership in a forest sector
  • protected areas (not state owned) – compensations to forest and landscape owners – Natura 2000

A wider discussion and closer co-operation is needed to approach or reach a consensus on dead wood matters between the forestry practices and nature conservation and the public