Transcript presentation

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
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
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
• 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 (μg.cm-3)
in oak branches during the decomposition and
mineralization process
(Swift, 1977 in Dajoz, 2000)
Elements
N
P
K
Ca
Mg
Fresh wood
1,057
69.5
767
1,935
146
Wood with fungi
1,304
54.4
141
3,871
118
Wood with fungi
and animals
710
27.8
20.9
1,777
58.3
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)
Organic
nitrogen
(%)
Ammoniacal
nitrogen
(%)
Nitric
nitrogen
(%)
Carbon
Healthy
wood
0.24
28
Dry rot
0.31
Damp rot
Wood
mould
Soil
Ash
C/N
(%)
Organic
matter
(%)
(%)
(%)
12
41.2
97.9
2.1
171.7
0
32
48
98.6
1.4
154.8
0.47
0
56
48.9
97.8
2.2
104
0.77-0.99
16-20
64-88
40.543.8
87-94.8
1.3-5.2
44.2-51.3
0.33
-
-
0.65
-
-
2.2
Moisture of substrate (% weight) in tree cavities
Calculation: (weight of water in s ubs trate/dry weight of s ubs trate)*100
Collecting date: April 30, 2002
Num ber of s am ples : n = 9, s am ple s ize N = 18
Subs trate profile: s urface layer - 20 cm - 40 cm deep
500
% weight
400
300
200
100
SURFACE
20 cm
0
1
2
3
4
5
CAVITY
6
7
8
9
40 cm
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
• 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 nondestructive 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
•
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
• 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
•
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
A commercial spruce
forest, Polana,
central Slovakia
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
3000
70
60
50
40
30
20
10
0
All Coleoptera
Scolytidae
Natural forest
Cerambycidae
Managed forest
number of individuals
number of species
80
2500
2000
1500
1000
500
0
All Coleoptera
Scolytidae
Cerambycidae
Ancient oak tree
Central Slovakia
Old pasture woodlands
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.
Problems
• 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