The importance of near-natural stand structures for the

For. Snow Landsc. Res. 79, 1/2: 127–144 (2005)
127
The importance of near-natural stand structures for the
biocoenosis of lowland beech forests
Susanne Winter, Martin Flade, Heiko Schumacher, Eberhard Kerstan and Georg Möller
Brandenburg State Agency for Large Protected Areas, Tramper Chaussee 2, D-16225 Eberswalde,
Germany
[email protected]; [email protected]; [email protected];
[email protected]
Abstract
A ‘Research and Development Project’ in Brandenburg (Germany) running from 1999 to 2003
aimed to define nature conservation standards for the management of lowland beech forests. The
avifauna, saproxylic beetle fauna, ground beetles, saproxylic fungi, and the stand structures were
investigated in twelve managed near-natural beech forests, and in six that had been unmanaged
for 12 to more than 100 years near-natural beech forests to identify bioindicators for near-natural
forest stands, which maintain the typical biocoenosis of beech forests. Some selected spotlight-like
results are presented in this paper.
The results show, for example, striking differences in stand structures between near-natural
beech stands and managed forests, close dependence of bird species on silviculture influences and
effects of forest developmental phases on ground beetles of beech forests. For instance, near-natural
stands are much more structured, richer in dead wood (10–20 times of the volume of managed
forests) and are characterised by a much higher abundance of breeding birds, especially woodinhabiting and beech forest indicator species, as well as some saproxylic fungi species. Saproxylic
and ground beetles are characteristic of deciduous forests.
Some examples for bioindicators of natural or near-natural beech forests are:
1 High number of special tree structures (e.g. trees with severe crown damage, large cavities,
clefts in the stem, scratches and bark bags with/without mould), which are typical attributes of
ancient forests and a suitable structural indicator.
2 The Middle Spotted Woodpecker Dendrocopos medius was identified as a valid indicator for
mature beech forests with old trees. The occurrence of D. medius depends on two typical stand
structures: a) rough bark structures (typical for old beech trees >200 years), and b) dead wood
in parts of the stems or branches of standing trees.
3 Carabus glabratus is suggested as a bioindicator among the ground beetles.
4 Fungi species of the genus Pluteus are significantly more frequent in unmanaged forests.
5 The number of individuals of saproxylic beetle species which are not captured in the managed
forests is three times higher than in >50 year-old unmanaged beech forests.
Keywords: lowland beech forest, natural beech forest, nature conservation standard, bioindicator
for naturalness, Fagus sylvatica, stand structure, avifauna, saproxylic beetles, saproxylic fungi,
Carabidae, ground beetles
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Introduction
The potential natural global distribution of beech forests with dominant Fagus sylvatica L. is
restricted to Europe with a focus on western, western-central and southern parts. In the
southern and warmer part of the potential natural distribution area, beech forests are located
in (sub)mountainous to subalpine regions, whereas in the northern area it is mainly a lowland to submountainous forest type. Lowland beech forests are potentially distributed in a
narrow belt from northern France and southern Great Britain over the northern part of
Germany, Denmark and southern Sweden to northern Poland (BOHN and WEBER 2000).
Germany has a high responsibility for the conservation of beech forest as it contains the
core area of global beech forest occurrence. Our project focuses on the lowland beech
forests because of their currently restricted distribution. At present, lowland beech forests
are scarce and extremely fragmented. The two largest continuous lowland beech forest
tracts of 3500 and 6500 hectares are located in the Schorfheide-Chorin Biosphere Reserve,
state of Brandenburg, north-east Germany.
Besides the small and fragmented area of actual occurrence, the lowland beech forests
have been severely altered by silviculture (e. g. young trees, in general with a maximum age
of 160 years). There are no virgin lowland beech forests left.
In practice it seems impossible to protect the whole biocoenosis of beech forests (FFHguideline 1992, appendix 1), including 7000 animal species and 4000 plant species (BERTSCH
1947) by simply creating unmanaged reserves (‘total reserves’). Although in Germany larger
unmanaged lowland beech forest reserves (which are not ancient forests!) were established
in 1990, e. g. parts of the Jasmund and Müritz National Parks and in the Schorfheide-Chorin
Biosphere Reserve. The proportion of strict reserves in the total forest area is less than 1 %.
Considering the limited dispersal potentials of many saproxylic beetles and fungi, it is obvious
that the protection of the entire lowland beech forest biocoenosis can only be guaranteed or
succeeded by implementing maintenance and conservation measures as part of normal
beech forest management.
The goal of the Research and Development Project (1999–2003) at the Brandenburg
State Agency for Large Protected Areas was to define nature conservation standards for the
management of lowland beech forests (FLADE et al. 2004; WINTER et al. 2002, 2003). The
main question was how to manage lowland beech forests without disturbing the typical biocoenosis. To answer this, the main studies had to find out the differences between managed
and unmanaged forests and the importance of near-natural stand structures for the bioceonoses of lowland beech forests. Some exemplary results of this comparison are presented
in this article.
There are three major topics:
1 To identify the differences between near-natural beech stands and managed forests.
2 To analyse the impacts of the stand structure on the biocoenosis.
3 To identify bioindicators for conservation-sound beech forest management.
2
Study sites and methods
The avifauna, saproxylic beetle fauna, ground beetles, saproxylic fungi, vegetation and the
stand structures were investigated in twelve differently managed near-natural beech forests,
and in six that had not been managed for 12 to more than 150 years. All stands were older
than 120 years. The study plots were located in the north-eastern part of Germany. Most of
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them were in the northern part of Brandenburg with four in Mecklenburg-Vorpommern
(Fig. 1). The area of study sites was about 40 ha each. This plot size could not be achieved in
two of the near-natural sites (r2 Heilige Hallen 24.9 ha, tree stand ~350 years old, r3 Fauler
Ort 13.6 ha, >350 years old) and the two shelterwoods (w4 Haussee 11.4 ha and w6
Klaushagen 17.4 ha).
Fig. 1. Location of the study sites in north-east Germany.
Fifteen study plots belong to the Galio odorati-Fagetum (FISCHER 1995). Four of them are
mixed with the Luzulo-Fagetum caused by the rich-structured relief and the soil changes of
this young moraine landscape, which was shaped by the Vistula glaciation (LIEDTKE and
MARCINAK 1995). The vegetation of one unmanaged study site represents the richer part of
the Galio odorati-Fagetum with Mercurialis perennis, Hepatica nobilis and Paris quadrifolia.
Two managed sites and one ~20 years unmanaged study site belong to the Luzulo-Fagetum.
The study sites are divided into three subdivisions, which are marked with different
letters: 1. managed forest = w (abbreviation of the German word “Wirtschaftswald”), 2. from
10 to 20 years undisturbed forests = k (abbreviation of “kurzzeitig ungenutzt” – shortly
unmanaged), 3. 50 years or more undisturbed forest = r (abbreviation of long-term reference
study plot). Study site Serrahn r1 was unmanaged for ~50 years and Heilige Hallen r2 and
Fauler Ort r3 for an unknown time but more than 100 years.
2.1
Stand structure
Our field studies were divided into grid point studies and full-coverage studies. At grid
points (100 m × 100 m in r-study plots, 100 m × 200 m in w- and k-study plots), detailed
parameters of the stand were measured.
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1 20 “Special Tree Structures” (STS) were recorded in a circle of 12.62 m radius (500 m2).
The 13 selected STS referred to in this paper are: 1. trees with severe crown damage
(more than 50 % of the crown is lost), 2. secondary crown trees (almost dead stems with
one or more big lateral branches, developed after break-down of the primary crown),
3. living trees with completely broken crowns, 4./5. large cavities with/without mould, 6.
cavities of large woodpeckers (Green Picus viridis and Black Woodpecker Dryocopus
martius), 7. clefts in the stem, 8. open bark gaps (scratches) and 9./10. bark bags with/without mould, 11.–13. trees with tinder fungus Fomes fomentarius, with Fomitopsis pinicola
or other fungi (for definitions see WINTER 2005). As an example of the results we take
the STS “bark bags with mould” with the following definition of its structure: The bark of
a tree is partially lifted and filled up with mould between the bark and stem; the lifted
bark has a width and height of 5 cm × 5 cm minimum, and a minimum depth of 2 cm.
The choice of special tree structures is mainly based on knowledge of habitat needs of
saproxylic insects and fungi (KOCH 1989; MÖLLER 1991, 1993, 1994; KÖHLER 1996) as
well as bats (MESCHEDE and HELLER 2000) and birds (BEZZEL 1986, 1992; FLADE 1994,
GLUTZ and BAUER 1994). The results presented are based on data from STS of living
trees.
2 Dead wood volume was calculated according to the length and middle diameter, measured
for standing dead trees 7 cm or more in diameter at 1.3 m breast height (without bark
6 cm diameter) and for lying dead trees 15 cm or more in diameter at the thicker end and
7 cm (without bark 6 cm) or more in diameter at the thinner end.
3 The forest development phases were mapped extensively in the study sites following the
method of TABAKU (2000) with small modifications by WINTER (2005).The forest cycle
was divided into eight development phases: regeneration, grow-up, early optimum, middle
optimum, late optimum, terminal, breakdown phases and gaps. Additionally, fens, bogs
and open water (small lakes) were mapped.
2.2
Breeding birds
The recording of breeding birds and their abundance was according to the ‘extended territory
mapping’ methodology (FLADE 1994; BIBBY et al. 1995, DO-G 1995). The avifauna of several
study sites was mapped in up to four subsequent years (1998–2001).
The bird population density has a natural dynamic or variation. Local changes could be
caused by weather conditions (like severity of winters), time and intensity of tree-fructification as well as shooting, droughts or other impacts during migration and wintering
(BEZZEL 1982; GATTER 2000). To achieve comparability of data gathered in different years,
an annual reference index value for eastern Germany calculated by SCHWARZ and FLADE
(2000) and FLADE and SCHWARZ (2004); data of the DDA Monitoring Programme = the
German Common Birds Census) was used. This index is based on some hundred bird monitoring plots which are surveyed by standardised methods and shows the large-scale annual
population changes of breeding birds in the whole of Germany as well as in sub-regions.
Local data on abundance were multiplied with the corresponding East-German population
index to be able to consider the general annual changes in species populations.
Calculation of preference index: A preference index was used to analyse whether birds
either prefer or avoid distinct forest development phases. Using a GIS, the number of bird
registrations in each forest development phase was summarised. The expected number of
registrations was calculated as an area proportion of the development phase and proportional share of all registrations of the respective bird species. Finally, the preference
For. Snow Landsc. Res. 79, 1/2 (2005)
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index for each bird species and development phase was calculated as follows: preference
index = number of bird records/expected number of records –1.
2.3
Saproxylic fungi
In eight study sites (five w-, one k- and two r-sites), all wood-inhabiting fungi species with
fruit bodies >4 mm diameter were registered in transects of one to two ha per study site. In
study sites with very low abundance of suitable habitats for saproxylic fungi, a transect was
taken which was a little longer than in well-structured stands. These transects had a width of
25 m. In the years 2000 to 2002, the fungi were mapped on five visits per study site in a semiquantitative way. Additional to the species name, the substrate of the fungi and the number
of growing locations (‘findings’) were registered. The number of fruit bodies was not relevant,
but the substrate units were. One saw-stump, one standing/fallen tree or branch was regarded
as one unit. Heaps of brushwood and fallen dead crowns were also regarded as a single unit.
The scientific names of the saproxylic fungi according to GERHARDT (1997) and additionally to JÜLICH (1984), MOSER (1978) and BREITENBACH and KRÄNZLIN (1984) are
used.
2.4 Saproxylic beetles
Saproxylic beetles (and some other important saproxylic insect taxa, not included in this
paper) were recorded at nine study sites (3 r-sites, 1 k-site and 5 w-sites) at five selected,
representative grid points each (see section 2.1). At each sample point, a bark beetle trap, a
crown trap (KÖHLER 2003) and one or two (depending on the breast height diameter of the
chosen tree) lime strips (rings), were installed for a full reproductive season (early May to
late August). Additionally, all special structures (dead wood and STS) providing habitats for
saproxylic insects were investigated by ‘hand and lamp trapping’ and ‘meshing samples’ over
the whole study site. Data analysis was performed separately for the whole data set of the
study site and exclusively for the data of the standardised grid point samples (the latter was
important in order to compare numbers of individuals between different study sites and to
correlate the trapping results with stand structure data). Indicator species for natural beech
forests were classified according to the following categories: a) species which were recorded
in several individuals and at (mostly) several sample points in the long-term unmanaged
study sites (r-sites), but were absent in the managed study sites (w-sites), and b) species
which were significantly more abundant at sample points in r-sites compared to the w-sites.
2.5
Ground beetles – Carabidae
For the recording of ground beetles, the standard pit trap method (BARBER 1931) was used.
Ethylenglycol was used as the trapping liquid. In every study site, five traps were installed at
selected grid points (see 2.1) from the beginning of the vegetation period (early spring) up
to the end of November. In every development phase (including gaps) which was represented
in the grid points of each study site, at least one was chosen to place a pit trap. Since the
maximum number of different development phases represented by grid points was five per
study site, a selection of development phases was not necessary. The pit traps were emptied
every fortnight (15 times during the vegetation period).
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Susanne Winter et al.
3
Exemplary results
3.1
Stand structure
3.1.1 Dead wood volume
The difference in occurrence of dead wood in managed and unmanaged forests was surprisingly large (Fig. 2). The r-sites (142–244 m3 per ha) had an approximately 10 to 15 times higher dead wood volume than w-sites (2.7–34 m3 per ha, within a section area of 10 hectares up
to 78 m3 per ha). The k-sites (unmanaged for 12–20 years) did not yet show clear differences
from the w-sites (Fig. 2). Dead wood pieces were not only much more abundant in the r-sites,
but were also on average twice as long and much thicker than in w-sites.
dead wood volume [m3/ha]
250
200
150
100
50
0
managed
unmanaged unmanaged
<20 years
>50 years
Fig. 2. Dead wood volume in managed and unmanaged lowland beech forests (mean volume
[m3/ha] + standard error.
3.1.1 Occurrence of Special Tree Structures (STS)
A certain time after direct human impact has ceased, forests develop distinct differences to
managed forests: e.g. smaller patches of development phases and development of late
optimum, terminal and breakdown phases (= ageing phases, LEIBUNDGUT 1993; KORPEL
1995; TABAKU 2000). In unmanaged forests, the qualitative diversity is, with 10 to 13 special
tree structure types per study site, significantly higher (p <0.001) than in managed forests
(3–8 special structure types per study site). In r-study sites, the number of STS is twice as
high as in w-study sites (Fig. 3). The mean in long-time unmanaged forests is 156 STS/ha and
in managed forests 76 STS/ha. If the structure of open bark gaps is excluded (promoted in
managed forests by felling and harvesting, and in unmanaged forests by falling trees), the
number of STS in r-study sites is almost three times higher than in w-study sites. This shows
that managed forests are much more uniform in structure.
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In the following, one STS and its importance for the lowland beech forest biocoenosis is
presented:
Bark bags with mould form from dead bark on dead or living trees. The bark is partially
lifted and filled up with mould between bark and stem. This STS was registered with a width
and height of 5 cm × 5 cm minimum, and a minimum depth of 2 cm. The mould consists of
decayed wood, chitin parts from insects, and animal excrement. The bark bags with mould
were variously used as nesting sites by treecreepers Certhia brachydactyla, C. familiaris
(GLUTZ and BAUER 1993), and as breeding sites or roosts for bats (e. g. Barbastella barbastellus, Myotis bechsteini, MESCHEDE and HELLER 2000). Insects use them as both hiding
places and breeding nests. In particular, species of the Dermestidae and Alleculidae prefer
to live in the mouldy, nutritious bark bags (MÖLLER 2000). So too do species of the
Histeridae which capture fly larvae in the bark bags. Another typical inhabitant of bark bags
in the crown of trees is Dictenidia bimaculata.
This small STS was not found in most of the managed forests, whereas in the r-study plots
it was found regularly. This STS is a good indicator for ageing structures on living trees
(Fig. 4). In all w-, k-study sites and in Serrahn r1 bark bags are less common than in >100
year-old unmanaged beech forests.
number/ha
250
bark gaps
all the other STS
200
150
100
50
0
w1 w2 w3 w6 w7 w8 w9 w10 w11 w12 w13
k1 k2 k3
k4
r1
r2
r3
study plots
Fig. 3. Special tree structures in managed and unmanaged lowland beech forests (number/ha) and share
of open bark gaps of the total number.
number/ha
10
8
6
4
2
0
w1 w2 w3 w6 w7 w8 w9 w10 w11 w12 w13
k1 k2 k3
k4
r1
study plots
Fig. 4. Bark bags with mould in managed and unmanaged lowland beech forests (number/ha).
r2
r3
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Susanne Winter et al.
3.2
What impact does the stand structure have on the biocoenosis?
3.2.1 Breeding birds
In the unmanaged forests Heilige Hallen r2 and Fauler Ort r3, 60–120 territories/10 ha were
found (Fig. 5). This is significantly more than in all other study sites (p <0,001, MannWhitney-U-Test). Because of the still very homogeneous structure, the briefly unmanaged
k-study sites do not have more territories/10 ha than the managed sites.
The calculation of the preference index for the habitat use of birds according to the forest
development phases resulted in pronounced differences (Fig. 6).
The breakdown phase is the most favourable phase for breeding birds. The early optimum
and terminal phase as well as gaps are also preferred by birds, but less than the breakdown
phase. Birds avoid the regeneration and middle optimum phase. It is not surprising that
forest birds occur less often in fen mires, bogs and forest lakes, which are not development
phases, but occur frequently in lowland beech forests.
23 of the 37 recorded bird species of lowland beech forests preferred the breakdown
phase (preference index >1). The differences in the abundance between w- and r-study sites
are mainly caused by the lack of this phase in managed forests.
One of the ‘wood-inhabiting’ species, which qualifies as an indicator species of beech
forests, the Red-breasted Flycatcher Ficedula parva, avoids the breakdown phase. It prefers
to forage in dark dense beech forest stands with high air humidity. Additionally, it needs
small cavities and clefts for nesting. These habitat needs are fulfilled in the terminal phase,
where F. parva has been recorded most often. All other indicator species of beech forests
(according to FLADE 1994, modified) prefer the terminal and/or breakdown phase.
High breeding-bird abundances in r-study plots and preferences for ageing phases
already indicate the rich and diverse supply of habitat structures in near-natural lowland
beech forests. The ecological value and importance of near-natural stand structures is also
exemplified by the Middle Spotted Woodpecker (Dendrocopos medius), which is mainly
abundance (territories/10 ha)
120
100
80
60
40
20
0
w1 00
w3 00
w6 00
w8 99 w10 98/02 w12 98–02
w13 01
w7 99
w4 99
w2 01
w9 98
w11 99
k1 00
k3 98
k2 98/01
r1 99–00 r3 98–01
r2 98–01
Fig. 5. Abundance of breeding birds (territories/10 ha) in unmanaged and managed lowland beech
forests; w = managed, k = shortly and r = long time unmanaged lowland beech forests; for study sites
with more than one mapping season: average values. Minimum and maximum abundance is shown for
study sites with more than one year of research.
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distributed in central and south-eastern Europe. Germany has about 20 % of the world
population (FLADE 1998). In our study sites, the occurrence of D. medius can be divided into
three categories (Fig. 7):
1 In six w- and two k-study sites the species is missing.
2 In six managed beech forests D. medius occurs, but in four of them this is caused by the
occurrence of oaks, which have a share of <10 % of the total number of stems.
3 The long-time unmanaged r-study sites Heilige Hallen r2 and Fauler Ort r3 show more
than one territory/10 ha, although almost no oaks occur. The same was the case in the k1study site ‘Stechlin’.
2.0
preference index
1.5
I
II
III
IV
V
regeneration
grow-up phase
early optimum phase
middle optimum phase
late optimum phase
VI
VII
VIII
IX
terminal phase
breakdown phase
gaps
fen/bog/water
1.0
0.5
0.0
I
II
III
IV
V
VI
VII
VIII
IX
–0.5
mosaic structure
Fig. 6. Preference index of breeding birds according to different forest development phases, and including
wetlands.
3.0
territories/10 ha
2.5
2.0
1.5
1.0
0.5
0
w1 00
w3 00
w6 00
w8 99 w10 98/02 w12 98–02
w2 01
w4 99
w7 99
w9 98
w11 99 w13 01
k2 98/01
k1 00
k3 98
r2 98–01
r1 99–00 r3 98–0
Fig. 7. Occurrence of Middle Spotted Woodpecker Dendrocopos medius (territories/10 ha) in lowland
beech forests. w = managed, k = shortly and r = long-term unmanaged lowland beech forests; for study
sites with more than one mapping season: average values.
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Susanne Winter et al.
3.2.2 Saproxylic fungi
The number of saproxylic fungi species (126 in total) varies in the study sites between 68 and
86. Most species were found in the forests Heilige Hallen r2 and Fauler Ort r3, unmanaged
for more than 100 years. The fewest were observed in one of the managed beech forests
(Fig. 8). Slightly more species were found in unmanaged lowland beech forests than in
managed stands, but the difference is not significant. Regarding the total number of findings
(localities) there were slightly, but also not significant, fewer localities in r-sites than in
w-sites (Fig. 9).
The occurrence of 22 species shows significant differences between managed and unmanaged lowland beech forests. Only three (Ascocoryne sarcoides [Fig. 10], Trametes hirsuta and
T. versicolor) of them are more abundant in managed forests. Eight out of 19 species, which
are more frequent in the r-study sites, Heilige Hallen r2 and Fauler Ort r3, belong to the
genus Pluteus (Fig. 11). Some species like Hericium coralloides (Scop.:Fr.) Gray, Pluteus
romellii (Britzelm.) Sacc. and P. umbrosus (Pers. ex Fr.) were exclusively recorded in r-study
sites.
3300
total number of localities of species
number of species per study site
95
90
85
80
75
70
3000
2700
2400
2100
1800
1500
1200
900
65
managed
unmanaged unmanaged
<20 years >50 years
Fig. 8. Species number (mean + standard deviation)
of saproxylic fungi found in managed, less than 20
and more than 50 years unmanaged lowland beech
forests.
managed
unmanaged
Fig. 9. Total number of growing units (localities)
of species registered in managed and unmanaged lowland beech forests (Box-Whisker-Plot,
showing median and quartiles).
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Ascocoryne sarcoides
[mean number of records per study site]
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50
40
30
20
10
0
managed
unmanaged >50 years
Fig. 10. Occurrence of Ascocoryne sarcoides
in managed and unmanaged lowland beech
forests.
Pluteus cervinus
Pluteus hispidulus
Pluteus nanus
70
Pluteus petasatus
60
Pluteus
phlebophorus
mean number of Pluteus species in study sites
Pluteus romellii
Pluteus salicinus
Pluteus umbrosus
50
40
30
20
10
0
managed
unmanaged <20
unmanaged >50
Fig. 11. Occurrence of eight species of genus Pluteus in managed, less than 20 and more than 50 years
unmanaged lowland beech forests.
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Susanne Winter et al.
3.2.3
Saproxylic beetles
In the unmanaged forests nearly 200 beetle species occur which were not recorded in the
managed forests (whole data set, including investigation of STS on the whole study site). The
total number of individuals of these beetles is very high (>1200). In managed forests fewer
than 400 individuals of beetle species without a record in the unmanaged forests were found
(Fig. 12), despite five w-sites, but only four (on average smaller) k- and r-sites were studied.
This result, along with the strong correlation between indicator species number and dead
wood volume found in the standardised grid sample plots, (Fig. 13, right) confirms the enormous importance of old-growth stands.
In managed beech forests, no significant correlation between the amount of dead wood in
grid sample plots (circles of 500 m2) and the number of individuals of indicator species was
found (Fig. 13, left), whereas the unmanaged beech forests show a strongly significant correlation between these two parameters (R2 0.41, p <0.01).
1400
individuals
Number of …
1200
species
1000
800
600
400
200
0
w12
w1
w5
w10
w9
k2
r1
r2
r3
managed
unmanaged
Fig. 12. Number of beetles species and recorded individuals of these species which occurred in only one
of the study sites exclusively; w = managed, k = briefly unmanaged and r = long-term unmanaged lowland beech forests; right: summarised data for managed and long-term unmanaged study plots.
2500
number of individuals
number of individuals
2500
2000
1500
1000
500
2000
1500
1000
500
0
0
0
10
dead wood [m2/500m2]
20
0
10
dead wood [m2/500 m2]
20
30
Fig. 13. Correlation between the number of individuals of saproxylic indicator beetle species and dead
wood, left: managed, and right: >50 years unmanaged lowland beech forests; both in sample plots (circles)
of 500 m2.
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Altogether, we identified 131 beetle species (out of 711 species with 155 000 individuals in
total) that significantly prefered unmanaged lowland beech forests, which we classify as indicator species for the naturalness of stands. Species number and number of individuals of
these indicator species (recorded in the grid sample plots) correlate significantly not only
with various dead wood parameters (besides total volume also e. g. number of objects,
volume of standing and fallen dead wood, basal area), but also with the forest development
phases, abundance of STS and number of STS types.
3.2.4 Ground beetles
4
60
individuals per trap
ground beetles of mesophilic deciduous
forest [individuals per 5 pit traps]
Ground beetles are influenced by changed stand structures in the ageing period (WINTER
et al. 2002; WINTER 2005). In long-term unmanaged lowland beech forests, many more individuals of so-called mesophilic forest ground beetle species (according to MÜLLERMOTZFELD 2001) were recorded than in managed forests (Fig. 14). As one example, the
occurrence of Carabus glabratus is shown (Fig. 15 and 16).
Carabus glabratus is trapped significantly more often in unmanaged than in managed
forests (Fig. 15). This is because it favours the breakdown phases which occur much more
often in unmanaged than in managed forests. On average, more than three individuals of C.
glabratus were found in pit traps located in the ageing phases. In all the other development
phases, summarised in two columns in Figure 16 (grow-up phase and optimum stage,
KORPEL 1995), a maximum of 0.5 individuals/pit trap only was recorded.
50
40
3
2
1
30
managed
unmanaged unmanaged
<20 years >50 years
Fig. 14. Captures of mesophilic forest ground beetle
species (MÜLLER-MOTZFELD 2001) in managed,
<20 years and >50 years unmanaged lowland beech
forests.
managed
unmanaged
Fig. 15. Captures of Carabus glabratus in managed and unmanaged lowland beech forests
[mean number of individuals per trap].
140
Susanne Winter et al.
number of individuals (mean)/trap
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
grow-up
optimum
development stage
4
breakdown
Fig. 16. Carabus glabratus in different forest development phases
[number of individuals per trap].
Discussion
This paper presents only an exemplary sample out of the entire results of a comprehensive
research project, which aimed to identify nature conservation standards for the management
of lowland beech forests (FLADE et al. 2004; WINTER et al. 2002, 2003, 2005). We focus on a
selection of pronounced differences between managed and unmanaged forests here.
Considering the fact that all study sites consist of ‘mature’ beech stands more than 120
years old, the clear differences between managed and long-term unmanaged forests in various
parameters like dead wood volume, special tree structures, and composition of different
parts of the biocoenosis are striking. The natural ageing of lowland beech forests up to the
breakdown phase causes an increase in structural and species diversity as well as an increase
in the number and abundance of species typical for lowland beech forests. As shown in the
investigations on breeding birds, saproxylic fungi, saproxylic beetles and ground beetles
(Winter et al. 2002), and also in more detailed ecological studies on foraging habitat use of
typical beech forests birds (such as the European Nuthatch Sitta europaea, Red-breasted
Flycatcher, and Middle Spotted Woodpecker; HERTEL 2001), strong-dimensioned dead
wood, the development of ageing phases and special tree structures are keystones for the
occurrence of typical and threatened beech forest species. According to ERNST and
HANSTEIN (2001), dead wood and special structures of old living trees also play an essential
role in the diversity of lichens.
The Middle Spotted Woodpecker Dendrocopos medius was identified as a valid indicator
for mature beech forests without any share of oaks. Occurrence depends on two typical
stand structures: a) rough bark structure (typical for old beech trees >200 years old) and b)
dead wood forming part of the stems or branches of standing trees (see above; GÜNTHER
and HELLMANN 1997; HERTEL 2001, 2003). Whilst young beeches have an unsuitable and
smooth bark, old trees develop the necessary rough bark with scratches and clefts.
Additionally, all breeding cavities of the Middle Spotted Woodpecker (n = 20) were located
in standing dead wood (dead trees or dead branches of living trees), which occurs much
more often in unmanaged than in managed forests.
For. Snow Landsc. Res. 79, 1/2 (2005)
141
Among the saproxylic fungi, the Icicle fungus Hericium coralloides is thought to be a suitable indicator for conservation-sound beech forest management. This fungus grows on dead
wood in a progressed stage of decay and, under suitable conditions, fructificates every year.
The species is easy to recognise because of its typical fruit body. Registration of this fungus
in the course of habitat type mappings and certification procedures is possible. The indicator
value is also described by SCHMID and HELFER (1995): “Unfortunately, you cannot find
Icicle fungus very often in the forest for simple economic reasons. The fungus does not put
up with saw-stumps or broken branches. It needs dead stems of strong dimensions as
habitat. Nowhere else is it able to build its fruit bodies. These large stems have an enormous
timber value and thus are rarely left for the Icicle fungi in the forest. To make a taxation of
this fungus could be regarded as worthless.” This fact gave the fungi a ranking in the Red
List of Brandenburg (MUNR 1993).
Strong-dimensioned dead wood contains more micro-climatic and decomposition stages
than smaller stems. Besides the Icicle fungus, some species of the genus Pluteus, especially
P. umbrosus, indicate old-growth forests (NUSS 1999) because it grows exclusively in the
final phase of the decomposition of these strong-dimensioned stems.
The high abundance of Ascocoryne sacroides in managed forests can be explained by its
occurrence on fallen small and damp branches, e.g. brushwood and crown breakage in managed forests, and on the cutting surface of tree stumps (MICHAEL et al. 1986). The two
Trametes species T. hirsuta and T. versicolor are more abundant in managed forests because
of their preference for light forest stands (DERBSCH and SCHMITT 1987; KERSTAN 2003). A
relatively low density of these species in unmanaged forests was also found by ADAMCZYK
(1995).
According to our results, the ground beetle Carabus glabratus shows a clear preference
for the ageing phases of beech forests, but according to the literature it is not a stenope silvicol
species (KOCH 1989; WACHMANN et al. 1995). C. glabratus does not depend upon beech
forests; it finds suitable habitats in coniferous or mixed forests, too (BARNDT et al. 1991;
MÜLLER-MOTZFELD 2001). Nevertheless, other authors have recorded C. glabratus only in
extended and old forests (LOHSE 1954; DÜLGE 1992). ASSMANN (1994) and ASSMANN et al.
(2001) described the species as an indicator for historical old-growth forest. Whether C.
glabratus is a suitable indicator for near-natural beech forests cannot be decided on the basis
of our investigation. Further detailed studies are necessary.
These results show that the occurrence of typical structures of the ageing phases in managed forests determines whether there is a deterioration of the typical biocoenosis, and thus
is crucial for the maintenance or loss of natural biodiversity.
Acknowledgements
This study could not have been undertaken without the Federal Agency for Nature Conservation
in Bonn, Germany, which financed our research project, and Silvia Dingwall for improving the
English.
142
Susanne Winter et al.
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Accepted May 19, 2005