Download Frequent fuel-reduction burning: the role of logs and associated leaf

Austral Ecology (2000) 25, 99–107
Frequent fuel-reduction burning: the role of logs and
associated leaf litter in the conservation of ant biodiversity
N. ANDREW,1* L. RODGERSON1 AND A. YORK2
1
Australian Flora and Fauna Research Centre, Department of Biological Sciences, Wollongong
University, Wollongong, New South Wales, and 2Key Centre for Biodiversity and Bioresources,
Department of Biological Sciences, Macquarie University, Sydney, New South Wales, Australia
Abstract Frequent low-intensity fires are used in management of Australian forests to reduce fuel loads and
protect natural resources and human property. Low-intensity fires are typically patchy and unburned litter microhabitats are often associated with large objects such as logs, which may act as refuges both for vertebrate and for
invertebrate fauna. The aim of this study was to determine whether ants were using unburned leaf litter microhabitats associated with logs as a refuge after fire. The study was carried out in Bulls Ground State Forest, New
South Wales, Australia, where experimentally burned and unburned sites had previously been established. Species
richness and abundance of ants in leaf litter did not differ between habitats adjacent to logs and away from logs,
in burned and unburned sites. Fifteen of the 42 ant species were found in all four habitats, and contributed 94%
of total ant abundance. Every habitat had a group of unique species, which together made up 30% of the total
species richness. There was also a distinct group of species that was not found in the leaf litter associated with the
burned/open habitat. However, as 45% of all species were found in low abundance (less than 10 individuals), care
must be taken in inferring patterns for these groups. When functional groups were used to assess community structure, ‘cryptic’ species were found to be common in all habitats, whereas ‘subordinate Camponotini’ were found
in burned habitats only. This study indicates that in an area where frequent burning is applied on a broad scale,
preserving a range of microhabitats, including those associated with retained logs, may make a substantial
contribution to conserving ant biodiversity.
Key words: ants, community structure, fire management, forests, functional groups, leaf litter, logging, Tullgren
funnels.
INTRODUCTION
Frequent low-intensity fire is the main management
tool used in Australian temperate forest areas. It is used
to reduce the incidence of severe and damaging wildfires, to stimulate germination and regeneration of
targeted plant species after logging, and to manipulate
wildlife habitat (Whelan 1995; McCullough et al.
1998). Surprisingly, there is little information on the
long-term effects of this fire regime on the abundance
and diversity of animals that live within these forests
(Whelan 1995). It is also unclear whether animals may
survive fires by taking refuge in unburned areas within
the burned habitat, or whether they must recolonise
from adjacent unburned areas (Whelan et al. 1980;
Campbell & Tanton 1981).
Fallen logs within managed eucalypt forests are quite
common (Meggs 1996) and are expected to provide
foraging, nesting and sheltering sites for many forest
*Present address: Mr N. Andrew, Department of Biological
Sciences, Macquarie University, Sydney, NSW 2109, Australia
(Email: [email protected])
Accepted for publication July 1999.
fauna. However, the number of large logs is expected
to decline over time in these areas as a result of oldgrowth logging and ongoing logging of regrowth
forests (State Forests of New South Wales 1995).
Integrated logging practices result in increased utilisation of timber resources, with unmerchantable trees
more commonly being used for railway sleepers, firewood, fencing timber and pulpwood. In northeastern
New South Wales, for example, salvage logs represent
approximately 21% of the overall annual woodflow
(State Forests of New South Wales 1995). Such strategies need to be weighed up against the potential
benefits to conservation of leaving logs within managed
forests (Meggs 1996). Large logs may act as effective
small-scale fire breaks because of their size and the
moist leaf litter that accumulates next to them (personal observation). This leaf litter may act as a microhabitat (Torres 1994) and potential refuge from fire for
a range of small animal species that are unable to
escape the fire (Campbell & Tanton 1981).
Forestry studies in Australia have traditionally
focused on vertebrates and plants (e.g. Braithwaite
1983; Loyn et al. 1983; Loyn 1985; Dickinson &
Kirkpatrick 1987; Kavanagh 1991; Lunney et al.
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N. A NDREW ET A L .
1991; Lindenmayer & Lacy 1995). Invertebrates are
now beginning to be incorporated into forestry studies
(e.g. Abbott et al. 1984; Neumann 1991; Michaels &
McQuillan 1995; York 1996). Changes in the species
diversity and abundance of particular invertebrate taxa,
such as ants, are often used to assess the impact of a
given management practice. However, species diversity
and abundance may not necessarily change, and it is
important to consider changes in species composition
of the disturbed community (York 1994, 1996). In
Australia, ants are considered to be good ‘bioindicators’
of disturbance because they are abundant and diverse
across a range of habitats, and are functionally important across all trophic levels (Andersen 1990). Ants are
responsive to environmental changes within their
habitats (Andersen 1990; Burbidge et al. 1992), and
their community assemblages (‘functional groups’)
can reflect the degree of habitat disturbance (Majer
et al. 1984; Andersen 1986, 1990, 1995; Burbidge et
al. 1992; Roth et al. 1994; Torres 1994; York 2000).
Previous work undertaken at the sites used in this
study (York 2000) examined the general differences in
ant community composition between burned and
unburned sites. The current work was designed to test
a specific hypothesis, namely that logs and associated
leaf litter play an important role in maintaining ant
biodiversity in frequently burned areas compared to
unburned areas. This was done by addressing the
following questions.
1. Is there a difference in the abundance, species richness, species composition, and/or functional groupings of the ant assemblages sampled from leaf litter
associated with logs compared to away from logs?
2. Does the abundance, species richness, species
composition, and/or functional groupings of the ant
assemblages recovered in leaf litter associated with
logs, relative to that away from logs, differ between
frequently burned and unburned sites?
(New South Wales Bush Fire Coordinating Committee
1998). Twelve of the 14 sites were chosen for this study.
Two sites (one burned and one unburned) were
judged to differ substantially from the other sites due
to rocky substrates. At the time of this study, March
1996, ‘burned’ sites had last experienced fire 4 years
ago in 1992 and ‘unburned’ sites had remained firefree for more than 25 years.
All sites were searched prior to sampling for suitable
woody debris (logs with girth >1 m), with suitable leaf
litter surrounding them. Debris had to be at least 10 m
from the site boundary to reduce potential edge
effects. At each of the 12 sites, leaf litter was sampled
adjacent to three logs (‘log’) and at three positions
approximately 3 m away from logs (‘open’). We ensured
that there was at least 10 m between each log. Samples
were collected on the 16 and 17 March 1996 during
a period of fine weather. At each position, four 1-L
samples of leaf litter were collected, bulked, and then
Table 1. Summary table of ANOVA for the number of ant
species and the abundance of ants extracted from 4 L leaf
litter using Tullgren Funnels at Bulls Ground State Forest,
New South Wales, during March 1996
Source of variation
d.f.
Burn
Site (Burn)
Rep (Site (Burn))
Position
Burn 3 Position
Site (Burn) 3 Position
Rep (Site (Burn)) 3
Position
1
10
24
1
1
10
24
Number
of species
F
P
Abundance
F
P
0.39 0.55
5.33 0.00
4.61
1.84
6.13 0.03
0.14 0.72
0.73 0.69
0.001 0.97
2.68 0.13
1.15 0.37
0.06
0.11
METHODS
The study area is located in Bulls Ground State Forest,
Kendall Management Area, Compartment 70, New
South Wales, Australia (31°339S, 152°389E), where
Eucalyptus pilularis (coastal blackbutt) is the dominant
canopy species. The area was first logged and treated
silviculturally in 1958–59. Fourteen 1-ha sites were
established for a long-term fire study by the Forestry
Commission of New South Wales in March 1970.
These sites were randomly selected and considered to
be representative of the surrounding forest type. Seven
sites were allocated to a ‘burned’ treatment and seven
were allocated as ‘unburned’ control sites. ‘Burned’
sites were burned every 3 years in autumn between
1970 and 1992 (York 1999a). This burning frequency
is defined as Zone 1 (Asset protection) of the Hazard
Reduction Zoning System for NSW managed forests
Fig. 1. Mean abundance (6 SE) of ants extracted per 4 L
leaf litter using Tullgren Funnels from the different habitats
(B/O, burnt/open; B/L, burnt/log; U/O, unburnt/open; U/L,
unburnt/log; n 5 6) at Bulls Ground State Forest during
March 1996.
LOGS C ON S ERV I N G A N T BI OD I V ER S I T Y A FT ER FI R E
placed into moist cotton bags for short-term storage
and transport.
Leaf litter samples were taken to the State Forests
Research Division to undergo invertebrate extraction
using modified Tullgren Funnels (Fairey 1982; Tanton
101
et al. 1983). Temperature of the funnels was maintained
10°C warmer than the room for 7 days. Funnel sieves
had an aperture size of 6 mm 3 6 mm and the collecting
liquid consisted of 200 mL Vantoc CL (which acts as
a biocide and surfactant) and 2 L water.
Table 2. Presence of ant species extracted per 4 L leaf litter in four habitats (B/O, burned/open; B/L, burned/log; U/O,
unburned/open; U/L, unburned/log) from six sites at Bulls Ground State Forest, New South Wales, during March 1996. The
symbols indicate the presence of a species within the sites, noting that three replicates were taken from each site (s, ant species
was found within one replicate of the site; •, two replicates; d, three replicates). Functional groups (Funct. Gp) of each species
are included (adapted from Andersen 1990, 1995, 1997), as is their membership in one of seven general groups (A, B, C, D,
E, F, or G) based on presence/absence in habitats (see text for explanation). Dom., Dominant Dolichoderinae; Sub-dom., subordinate Camponotini; Clim Sp., climate specialists; Cryp., cryptic species; Opp., opportunists; Gen., generalised Myrmicinae;
Sp. Pred., specialist predators.
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N. A NDREW ET A L .
Samples were returned to the laboratory and sorted
using a binocular microscope. Ants were separated
from the other orders, and then sorted to genera using
characteristics described by Andersen (1991a) and
Bolton (1994). Individuals were then sorted to
morphospecies following the protocols of Oliver &
Beattie (1993, 1996). Morphospecies were checked
and confirmed as separate species by Dr Stephen
Shattuck (CSIRO Entomology, Canberra) and a reference collection was lodged at the State Forests Research
and Development Division, West Pennant Hills,
Sydney. The taxonomic nomenclature used here is consistent with that used by York (2000).
The mean species richness and abundance (per 4 L
leaf litter) were analysed by analysis of variance (ANOVA)
in relation to three factors: ‘burn’ (burned/unburned),
‘sites’ (six per burn), and ‘position’ (log/open). ‘Sites’
were nested within ‘burn’, with three replicate logs per
site nested within ‘sites’ for a total of 72 samples. ‘Burn’
and ‘position’ were treated as fixed factors, and ‘sites’
was treated as random. ‘Sites’ were included as a
factor due to previous spatial patterns identified by York
(1999a, b, 2000). The ANOVA model used was:
constant 1 burn 1 site (burn) 1 rep (site [burn]) 1
position 1 burn 3 position 1 site (burn) 3 position 1
rep (site [burn]) 3 position.
Abundance data were square root transformed to
improve the normality of the underlying distribution
(Zar 1984). All analyses were performed using SYSTAT
1996 (Systat).
Ant species were grouped according to habitat type
(burned/open, burned/log, unburned/open, unburned/
log) in which they were found. Functional groupings
(Andersen 1990, 1995, 1997) were examined in order
to determine whether there was any relationship with
the habitat in which they were found. A multivariate
analysis of variance (MANOVA) was used to detect differences between the relative species richness of each functional group within each habitat (n 5 4). The three
samples taken from leaf litter under logs were bulked
from each site, as were samples from open leaf litter.
Sites (n 5 6) were used as replicates for a total of 24
samples. Percentage data were square root and arcsin
transformed according to Zar (1984) to improve the
Fig. 2. Two-dimensional MDS (multidimensional scaling)
plot (stress 5 0.0) showing similarity of habitats (B/O,
burned/open; B/L, burned/log; – U/O, unburned/open; U/L,
unburned/log) according to ant assemblages extracted from
leaf litter at Bulls Ground State Forest during March 1996.
The habitats circled represent 70% similarity in ant assemblages using the Bray–Curtis coefficient of similarity.
Fig. 3. Comparison of the proportion of ant species in
functional groups extracted from leaf litter in four different
habitats (B/O, burned/open; B/L, burned/log; U/O,
unburned/open; U/L, unburned/log) at Bulls Ground
State Forest during March 1996. , Specialist predator;
h, generalist;
, opportunist; j, cryptic;
, climate
specialist; , sub-dominant; , dominant.
Table 3. Summary table of MANOVA for the proportion of ant species in functional groups extracted from leaf litter using
Tullgren Funnels at Bulls Ground State Forest, New South Wales, during March 1996
Functional group
Source of
variation
d.f.
Habitat
Error
3
20
Dominant
F
P
Subdominant
F
P
Climate
specialist
F
P
Cryptic
F
P
Opportunist
F
P
Generalist
F
P
Specialist
predators
F
P
0.33 0.80
1.64 0.21
0.86 0.48
0.98 0.42
1.03 0.40
1.37 0.28
0.58 0.64
LOGS C ON S ERV I N G A N T BI OD I V ER S I T Y A FT ER FI R E
normality of the underlying distribution. Analysis was
performed using SYSTAT.
Multivariate analysis of the abundance of each ant
species was performed using PRIMER (Carr 1996). A
multidimensional scaling (MDS) and dendrogram of
the data were used to assess and display the similarity
of ant assemblages collected from leaf litter in the four
different habitats (burned/open, burned/log, unburned/
open, unburned/log). The similarity matrix for the dendrogram and MDS was based on the Bray–Curtis
metric (b 5 –0.05). The MDS was constructed in two
dimensions.
RESULTS
Abundance and species richness
In total, 5127 ants were collected from the leaf litter
samples in all four habitats. Despite large differences
in overall ant abundance, there were no statistically
significant differences in overall abundance between
burn treatment or sample position (log versus open)
(Fig. 1), and no significant interaction (Table 1).
Overall, 42 ant species from 32 genera belonging to
four subfamilies were collected within the study area.
There were 18 species of Myrmicinae from 15 genera,
13 species of Ponerinae from nine genera, 10 species
of Formicinae from seven genera, and one species of
Dolichoderinae.
The mean species richness of ants collected from leaf
litter positions adjacent to logs (13 6 3.5) was significantly greater than that from leaf litter collected away
from logs (12 6 2.9; Table 1). There was also significant variation in species richness among sites. However,
there was no significant difference in species richness
between burned (12 6 2.8) and unburned (12 6 3.6)
sites, and the interaction between the burn treatment
and sample position (‘burn’ 3 ’position’) was also not
significant (Table 1).
Ant community composition
Of the 42 ant species collected, 15 species were found
in leaf litter from all four habitats (group A, Table 2).
Five of these species (Paratrechina sp. 1, Hypoponera sp.
1, Solenopsis sp. 1, Stigmacros sp. 3, and Pheidole sp. 1)
were collected from most sites within these habitats.
Overall, this group of 15 species made up 94% of the
ant abundance (4807 individuals), with two species
making up 58% of this (Pheidole sp. 1–1717 and
Paratrechina sp. 1–1220).
Eight species (165 individuals) were found in the
leaf litter of the burned/open habitat and at least
one other habitat, but not all four habitats (group B).
These species may potentially reside in all four
103
habitats, but generally were not widespread within the
samples.
Six species (105 individuals) were found in leaf litter
from at least two habitats, but were absent from the
burned/open habitat (group C). Two of these species
(Rhytidoponera sp. 2 and Orectognathus sp. 1) were found
only adjacent to logs at both burned and unburned
sites, with only five and three individuals collected,
respectively. The other 13 species (30% of total species
richness) were only found in a single habitat type: four
species from burned/open (group D, 22 individuals),
three from burned/log (group E, seven individuals), two
from unburned/open (group F, two individuals), and
four species from unburned/log (group G, 19 individuals). The majority of these species were only found
in one sample from one site so they can be considered
locally rare within that habitat.
Multivariate analysis of the ant assemblages suggests
that all four habitats were quite similar (between 60%
and 73% similarity; Fig. 2). However, the unburned/
open and unburned/log habitats were most similar in
their ant assemblages, and these were more similar to
the burned/log habitat than to the burned/open habitat.
The analysis of patterns of ant community composition (Table 2) indicates that many common and abundant species are distributed across leaf litter in all four
habitats (group A). However, there are distinct groups
of species that were not recovered from burned/open
habitats (groups C, E, F and G). These species were
found in only a few samples and in low abundance, but
make a strong contribution to the overall species richness. However, because these species are found in such
low numbers, the random effects of presence/absence
for these species must be considered.
The ant community composition was also examined
in terms of the functional groupings (dominant
Dolichoderinae (dominant), subordinate Camponotini
(sub-dominant), climate specialist (hot and cold
climate specialists combined), cryptic, opportunist,
generalised Myrmecinae (generalist) and specialist
predator; Table 2, Fig. 3. Cryptic species were most
common with 15 of the 42 species (36%) belonging to
this group. This group was found in each of the four
habitats, though six of the cryptic species (Stigmacros
sp. 5 [11 individuals], Amblyopone spp. 1 [one] and 2
[eight], Acropyga sp. 1 [five], Oligomyrmex sp. 1 [one]
and Sphinctomyrmex sp. 1 [two]) were recovered in
low numbers. The opportunists and the specialist
predators were also reasonably common, being found
in all four habitats, and each contributing seven species
overall.
Overall, the contribution of each functional group
was similar for each habitat (Table 3). Within burned
habitats the relative percentage of functional groups is
roughly the same between log and open litter positions
(Fig. 3). This is also the case in the unburned habitat,
but here there was a greater percentage of specialist
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N. A NDREW ET A L .
predators and generalists, and a lower percentage of
climate specialists in litter associated with logs. The
major difference between burned and unburned
habitats with regard to community structure is the lack
of sub-dominants on unburned sites. The dominants,
climate specialists and generalists were found in all four
habitats, collectively contributing 26% to the overall
species composition. The dominants consisted of only
one species in each habitat (Anonychomyrma sp. 1). The
contribution of climate specialists and generalists to
species composition, however, varied between the
different habitats. Similar numbers of species of climate
specialists were found at burned/open, burned/log, and
unburned/open sites, and fewer at unburned/log
habitats. Sub-dominant species were only found in
the burned habitats. Camponotus sp. 4 was found
both in log and in open positions, whereas one
individual of Polyrhachis sp. 3 was found only in the
open position. In our sampling, none of these differences among habitats were statistically significant
(Table 3).
DISCUSSION
Disturbance has been found to be important in determining the composition and structure of ant communities (Brian et al. 1976; Majer et al. 1984; Puntilla et
al. 1991; Burbidge et al. 1992; Roth et al. 1994; York
1996, 2000). In Australian forest communities fire is
an important and ongoing disturbance and a number
of studies (e.g. Andersen 1988; Andersen & Yen 1985;
1991b; York 1994, 1996, 2000) have examined the
effect of fire on ant communities. In this study, the
species diversity and abundance of ant species in leaf
litter did not differ significantly between frequently
burned and unburned areas, and the abundance
between two major microhabitats (log/open) within
these habitats. However, there was a significant difference in species richness between the log/open microhabitats.
Ant species richness within leaf litter was similar
across the four habitats (burned/open, burned/log,
unburned/open, unburned/log; Table 1: burn 3 position). York (2000) also found that there was no difference in species richness between burned and unburned
sites, and with approximately two thirds of species being
found in both treatments. Mean (6 SE) values of
species richness (at the scale of ‘site’) found in litter
samples collected in ‘open’ areas in this study were 11.3
(6 1.1) and 12.3 (6 1.3) for burned and unburned
habitats, respectively (Table 2). This is similar to richness values of 10.0 (6 1.8) and 13.8 (6 1.5) found in
the same habitats by York (2000) 2 years earlier.
Even though species richness between habitats is
similar, species composition did differ (Table 2). The
majority of ant species were associated with all four
habitat types (group A), which is important since it
implies that these ant species can maintain populations
in a wide range of conditions. However, the leaf litter
associated with the four different habitats had groups
of unique ant species, with many of these species occurring in low numbers (groups D, E, F and G). This
association of some species to a particular habitat makes
sense since each habitat has different attributes, such
as the presence of logs, which may suit a particular
group of ants (Majer et al. 1984). The group of ants
found only in leaf litter associated with the two
unburned habitats and the burned/log habitat could be
due to the leaf litter not being scorched by fire.
Similarly, the group of ants found solely in the leaf litter
associated with the burned/open habitat may need the
disturbance of frequent fire. However, these associations are based on trends that include species that were
sampled in low abundances therefore they must be
treated with caution.
The richness of ant species found in each habitat
implies that, 4 years postfire, the burning practices used
by forest managers are not adversely impacting upon
ant diversity even though they are structurally simplifying the environment (see York 1999b). York (2000)
showed that a mosaic of burned and unburned habitats at the landscape scale maintains the overall ant
diversity within the treated area. Unburned habitat
includes whole areas not being burned, as well as
microhabitats close to large objects, such as logs within
burned areas, which can maintain a moist and thick
layer of leaf litter (Harmon et al. 1986; Torres 1994;
Brown et al. 1996). This study has shown that in areas
where, for strategic purposes, frequent burning is
applied on a broad scale, the microhabitat associated
with retained logs may make a substantial contribution
to overall invertebrate biodiversity conservation.
Many previous studies both in Australia (e.g.
Springett 1976; Campbell & Tanton 1981; Abbott
1984; Abbott et al. 1984; Neumann 1991; Neumann
& Tolhurst 1991; York 1999a) and overseas (e.g.
Heyward 1936; Metz & Farrier 1973), have looked at
taxa at the ordinal level to examine the effects of fire
on invertebrate composition. This is appropriate when
many groups are used. However, changes in community composition within taxa and between treatments
often cannot be clearly identified. This study found that
there are differences in ant species composition
between different habitats (Fig. 2; Table 2). These differences must therefore be considered if management
decisions are to be made on the role of frequent lowintensity burning, and the role that logs play in these
managed forests.
Abundances of ants extracted from leaf litter were
similar for all habitats because 94% of overall ant abundance was contributed by 15 species that were found
in all four habitats. There were also 19 species (nearly
half of the species collected) contributing less than
10 individuals each to the overall abundance, thus
LOGS C ON S ERV I N G A N T BI OD I V ER S I T Y A FT ER FI R E
indicating they are rare. These species of low abundance (e.g. Sphinctomyrmex, Amblyopone, Oligomyrmex
and Acropyga) are frequently overlooked in studies
because they are suited to particular microhabitat conditions (Majer et al. 1984; York 1994) and are uncommon. Rare species may be able to survive single fires
by taking refuge within leaf litter that is not burned
(Campbell & Tanton 1981). Many rare species in this
study require specialist habitat, and may not survive frequent fires without large objects or unburned areas to
act as potential refuges. However, because these species
are found in such low numbers the associations that
are made must be done with caution (see Diamond
1976; Simberloff & Abele 1976).
The method of ant collection is also critical to the
assessment of the composition of the ant community
sampled. In many ant-based studies pitfall traps are
used (Whelan et al. 1980; Andersen 1986, 1988,
1991b; Neumann & Tolhurst 1991; Burbidge et al.
1992; York 1994, 2000) because of their simplicity and
their ability to collect a large number of animals. Pitfalls
catch throughout the 24-h activity cycle, but a number of days of trapping are necessary to reduce biases
due to day-to-day variation of populations (Rossbach
& Majer 1983; Greenslade 1985; Abensperg-Traun
1992). However, this method does not necessarily show
the overall ant community composition as it only collects species that are foraging on the top of the leaf litter and soil (Holldobler & Wilson 1990). Leaf litter
sampling is a ‘snapshot’ collection technique. Even
though one sample is taken at one time of the day, it
records species that are cryptic and solitary within the
leaf litter, that have small densities of workers (Olson
1994), such as was found in this study. Comparing the
ant species found in this study with those found in York
(2000) leaf litter sampling collects species that are
unlikely to be found in pitfall traps. In this forest environment, of the 90 species collected by York, 16 species
(18%) were detected only in litter samples. Sampling
the leaf litter associated with large logs (this study)
added a further five species to the inventory, which
although only a small percentage overall (5.3%),
detected rare species which are (potentially) functionally important in the ecosystem and have high conservation status. These were Pheidole sp.7, Monomorium
spp. 4 and 5, Sphinctomyrmex sp.1 and Orectognathus
sp.1. All these species were collected from one sample
within one or two sites (Table 2). This indicates that
they may have been missed from other samples due to
chance alone. However, Orectognathus sp.1 was found
in leaf litter collected from under logs both in the
burned (one individual) and unburned (two individuals) habitats. This indicates that conservation of this
species may need to include the preservation of logs
within both burned and unburned habitats.
The overall structure of ant communities appeared
to be quite similar across the four habitats (Fig. 3;
105
Table 3). However there were some differences in the
dominants and subdominant functional groups which
were not significant but are possibly important. Subdominant species (15 individuals of Camponotus sp. 4
and one Polyrhachis sp. 3) were found only in ‘burned’
habitats, indicating they potentially need disturbances,
such as fire, to reduce leaf litter loads (Andersen 1995).
Only one species in a dominant functional group was
collected (74 individuals of Anonychomyrma sp. 1) from
all sites, with the majority (69 individuals) sampled
from the burned/log habitat. However, these nonsignificant trends together with the other results from
this analysis (Table 3) need to be viewed with caution
for two reasons. Firstly, the sample sizes for MANOVA
were relatively small, and secondly we did not fully meet
the assumptions of parametric tests.
Regularly prescribed fire treatment is used in
managed forests to reduce the incidence of wildfires
within these forests. Due to the nature of high intensity
wildfires (Gill 1981; Whelan 1995) it is neither possible
nor desirable to have a no-burn policy within managed
dry eucalypt forests. Leaf litter adjacent to woody debris
(such as logs) seems to play a valuable role in maintaining ant community composition within managed
forests after a long-term low-intensity fire regime has
been implemented (as shown in this study). The need
to look at community composition and functional
groups, as well as species diversity, is extremely important in studies such as these, especially in terms of
maintaining a functioning ecosystem (Beattie 1995;
Commonwealth of Australia 1996; Lovejoy 1996).
Such information is important since forestry agencies
manage these areas through controlling leaf litter (fuel)
levels. As part of their fauna management strategy in
northern New South Wales, State Forests aim (State
Forests of New South Wales 1995), during harvesting,
to retain ground logs and associated understorey
vegetation around designated habitat trees and to
prescribe only low-intensity patchy fires. In light of
this, the maintenance of a range of habitats including
totally unburned areas, as well as potential refuges
such as logs, within areas subject to frequent burning
would be desirable to maintain ant community
diversity.
ACKNOWLEDGEMENTS
State Forests of New South Wales kindly let us use of
the experimental burn sites at Bulls Ground State
Forest, as well as their Tullgren Funnel facilities at West
Pennant Hills. We thank Sarah Hill for her help with
the extractions, David Britton who assisted with
preliminary ant identifications, Michael Dunlop and
Ken Russell for advice on statistical analyses, and
Rob Whelan for his comments on the draft
manuscript.
106
N. A NDREW ET A L .
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