James Cook University, Townsville
Aims | Introduction | Fire as a tool to manage rubber vine | Study sites | Methodology | Preliminary results |
Fire treatment site, Burdekin Catchment,
Cornishman Creek, Queensland
This study uses an experimental approach to investigate how
native animals, particularly birds and reptiles, respond to the
presence of one of northern Australia's most pervasive weeds,
rubber vine ( Cryptostegia grandiflora ). As fire is now
being used to manage rubber vine, the study is also examining how
these animals respond to fire.
Specifically, this project will answer five questions:
Is the richness or structure of bird and reptile assemblages
affected by the presence of rubber vine, and how do particular
species of birds and reptiles respond to rubber vine
What are the short and medium term impacts of different seasonal
controlled burning on bird and reptile assemblages?
What are the short-term impacts of a repeated control burn on
Do predation rates of birds on skinks increase following
What are the impacts of mosaic burning on bird assemblages?
Preliminary results indicate the burning strategies to control
rubber vine are affecting some faunal species and assemblages.
Although the majority of species affected had higher abundances in
the burnt treatments, at least one fire-sensitive species, the
Red-backed Fairy Wren, was identified.
Plants introduced to Australia that become weeds can have
devastating consequences on both native animals and plants.
Large areas of Queensland's pastoral land have been invaded by
rubber vine since its introduction into Australia in the late 1800s
from Madagascar (Grice 1997). The vine has spread rapidly along
riverbanks and adjacent open woodlands in northern Queensland,
causing problems for graziers and potentially reducing the native
biodiversity values of the state's open woodlands (Bebawi and
The weed's invasive nature and tendency to smother trees and
shrubs has reduced the biodiversity values of native vegetation,
but the impact of rubber vine on native animals is unknown.
In Australia, fire is often used as a contemporary management
tool to control introduced weeds, including rubber vine. Research
indicates that fire can significantly reduce rubber vine and has
the potential for widespread use in tropical savannas of northern
Queensland where riparian systems are infested (Grice 1997).
However, the impacts of such fire management on native fauna are
Fire and fauna studies, primarily conducted in the Northern
Territory, suggest that faunal assemblages are strongly influenced
by fire and, particularly in the tropics, by the components of a
fire regime (Braithwaite 1987; Woinarski et al . 1999).
The differences in habitat, community structure and land use
between Queensland and the Northern Territory are likely to produce
different responses to fire among faunal communities.
The striated pardalote ( Pardalotus
striatus ) was one of a number of birds that Leonie found in
higher abundance in dry burnt treatments compared to unburnt
Reptile species diversity, abundance and
composition were similar across all treatments. Above is the
knobtail gecko, Nephrurus asper
The effectiveness of different fire regimes for controlling
rubber vine was investigated by CSIRO Sustainable Ecosystems (CSIRO
SE) in a Tropical Savannas CRC-funded project (see web link
Through this research, a protocol to investigate fire as a
management tool was developed for controlling rubber vine in grazed
riparian environments of open woodlands.
Replicate experimental study sites, encompassing 2-3 km of creek
line and adjacent open woodland were established on three separate
tributaries of the Burdekin River on leasehold cattle grazing
properties in Dalrymple Shire, north Queensland.
Five plots, separated by double firebreaks, were established at
each site, spanning both sides of the creek bed. Each plot
comprises about 20 ha and covers both riparian and woodland
vegetation. Five fire treatments are being used, including single
and successive fire in both the dry and wet seasons and unburnt
The study's design allows the simultaneous examination of the
effects of single versus repetitive burning and seasonality of the
These sites also provide an excellent opportunity to examine the
impact of fire regimes and exotic species on how native faunal
communities are structured in the open woodlands of the Burdekin
River Catchment. Results will feed into a comprehensive management
strategy for the region.
Question 1: Is the richness or structure of bird and reptile
assemblages affected by the presence of rubber vine, and how do
particular species of birds and reptiles respond to rubber vine
Rubber vine regularly occurs as shrubby thickets (1-2m high)
along riparian systems where it displaces native vegetation
thickets. This may potentially affect native birds and reptiles
that regularly use vegetation thickets and associated
microhabitats, such as leaf litter. This part of the project aims
to determine how representative birds and reptiles use rubber vine
as habitat. Assemblages of fauna in both rubber vine and native
vegetation patches are being compared, along with variables such as
the availability of prey, vegetative structure and air
This particular study site is located along Six Mile Creek, an
ephemeral tributary of the Burdekin River in open woodlands where
rubber vine is prevalent.
Broad vegetative structural variables, including rubber vine
intensity, number of trees and shrubs, will be described, and the
characteristics of microhabitats (leaf litter, composition of leaf
litter, substrate composition, foliage cover) will be collected for
Species composition of birds and reptiles in native vegetation
versus rubber vine thickets will be compared, and related to
habitat variables and insect biomass.
Question 2: What are the short and medium term impacts of
different seasonal controlled burning on bird and reptile
Seasonality of a burn can be an important component in
determining faunal responses to fire. Potential rubber vine
fire-management strategies include burning in both wet and dry
seasons. The CSIRO SE experimental fire sites examined fire
treatments that included wet, dry and an unburnt control.
The composition of bird and reptile species within each fire
treatment will be compared to each other, and to the unburnt
control, at two intervals to determine the short-term (5-12 months
post-fire) and medium term (2-3 years post-fire) impacts of
The first sampling period occurred in the wet season of 2001,
and the second sampling period occurred in the wet season of
Differences in microhabitat (percentage leaf litter, grass,
rocks, canopy cover, number of trees) will be examined and the
effects of structural vegetation changes on fauna will be examined
by integrating data from the fauna survey results with that
produced by the microhabitat surveys.
Question 3: What are the short-term impacts of a repeated
control burn on bird assemblages?
Another potential fire-management strategy is repeated, or
successive, burning. The impact of of these fires will also be
investigated The short-term impacts of successive fires on bird
assemblages will be examined by comparing species composition
between a singularly burnt plot, a repeatedly burnt plot, and an
unburnt control. Treatments were sampled in the wet season one year
following the initial fire, and were again sampled in the wet
season one year after the second fire occurred. Species composition
of birds and vegetation structure will be surveyed as outlined
Question 4: Do predation rates of birds on skinks increase
following controlled burning?
One potential ecological consequence of fire, following the
removal of ground vegetation, is an increase in birds preying on on
skinks (Woinarski 1990) because of greater visibility and
accessibility. This will be examined by comparing predation rates
in burnt and unburnt plots..
Predation rates will be determined by assessing the frequency of
avian attacks on life-like skink models placed in each treatment.
Skink models will be made by attaching Blu-tac ®
onto hard plastic bases cut in the shape of a skink, and then
spray-painting them to resemble Carlia munda , a commonly
occurring skink. Models will be placed in transect lines in each
habitat of the treatments at each creek for ten consecutive
Question 5: What are the impacts of mosaic burning on bird
assemblages in grazed riparian environments of northern
Research into the impacts of fire on faunal assemblages
indicates a variety of responses to fire with certain fire regimes
favouring some species, while disadvantaging others (Braithwaite
1987; Woinarski 1990). This has resulted in an emphasis on
conservation managers to implement burning patterns that result in
a mosaic of patches across the landscape aimed at maximising
biodiversity (Woinarski & Recher 1997).
Surprisingly, however, the efficiency of mosaic burning in
enhancing overall diversity has never been demonstrated in the
literature. As the study sites represent three replicates of
fine-scale mosaic burning, incorporating unburnt, seasonally burnt
and repeatedly burnt habitat, along sections of three creeks. This
provides a good opportunity to examine the impact of mosaic burning
on bird assemblages by comparing the CSIRO-SE study sites to three
creeks in the same region that have not undergone mosaic burning
Bird assemblages will be surveyed in both woodland and riparian
habitats along 2 km sections of each creek. Half-hour timed surveys
will be conducted at each creek until no new species are detected
in three consecutive surveys. Species diversity, abundance and
assemblage structure will be compared between variably burnt and
control creeks. Vegetation structure at each creek will be
described using eight large (20 x 10 m) quadrats in each habitat of
each creek. Variables recorded will include number and species of
trees, number of shrubs, presence of ground cover, flowers and
fruit and canopy cover.
A fauna sampling strategy was established during the wet season
of 2001—as part of my Masters qualifying project—and
aimed to determine bird and reptile species richness and abundance.
The preliminary results include the short-term impacts of seasonal
burning on bird and reptile assemblages.
Differences in faunal assemblages of birds and reptiles were
investigated by comparing species number and abundance between
replicate fire treatments (unburnt control, wet-season
burnt—12 months since fire, dry-season burnt—6 months
Figure 1: Overall mean bird abundance per fire
treatment (* represents treatment different to control).
Figure 2: Mean feeding category abundance of
birds per fire treatment (* represents treatments different to
The structure of bird assemblages was further investigated by
grouping birds into feeding categories based on dietary
preferences. Preliminary analysis documented a higher overall
abundance of birds in the dry-season burnt treatments, compared to
the unburnt controls (Figure 1). Assemblage structure (using
feeding categories) of birds also varied between treatments with
higher abundances of insectivores observed in both the burnt
treatments compared to the unburnt treatments (Figure 2).
Some individual species of birds were found in higher abundances
in dry burnt treatments compared to unburnt treatments. These
included the Pied Butcherbird ( Cracticus nigrogularis ),
Striated Pardalote ( Pardalotus striatus ), and Pale Headed
Rosella ( Platycercus adscitus ).
The Red-backed Fairy Wren ( Malurus melanocephalus ) had
lower abundances in both the burnt treatments compared to the
control indicating a potential sensitivity to burning practices.
Reptile species diversity, abundance and composition remained
similar across all treatments, although higher abundances of
Carlia munda were found in dry burnt treatments compared to
Seasonality of fire is often considered a biologically important
aspect of fire regimes as it largely determines intensity and
extent of burn (Braithwaite and Estbergs 1985; Christensen et
al. 1981). The dry-season fire may have altered the vegetation
structure more dramatically than did the wet season fire, favouring
higher abundances of certain species, but not others.
Alternatively, differences in bird abundance between burning
treatments and controls may be related to time since fire. Previous
studies suggest an initial increase in general bird abundance in
the first six months post-fire, due to an increase in food
abundance or availability (Woinarski and Recher 1997).
Results indicate the burning strategies to control rubber vine
are affecting some bird species and the overall bird assemblage
structure. Although the majority of species affected had higher
abundances in the burnt treatments, at least one fire-sensitive
species was identified. Further study is required to better
understand the impact of weed management burning on faunal
assemblages in riparian environments of grazed open woodlands in
Queensland. The study will also contribute to examining a broader
conservation management theory on mosaic burning to maximise
Bebawi, F. F., and S. D. Campbell. 2002. Impact of early and
late dry-season fires on plant mortality and seed banks within
riparian and subriparian infestations of rubber vine (
Cryptostegia grandiflora ). Australian Journal of
Experimental Agriculture 42 :43-48.
Braithwaite, R. W. 1987. Effects of fire regimes on lizards in
the wet-dry tropics of Australia. Journal of Tropical
Ecology 3 :265-275.
Braithwaite, R. W., and J. A. Estbergs. 1985. Fire patterns and
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invasive tropical shrubs Cryptostegia grandiflora and
Ziziphus mauritiana . Australian Journal of Ecology
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communities of tropical woodlands and open forests in northern
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