IALE-OZ
NEWSLETTER
ISSUE
2.1 April
2001
EDITORIAL
Hello,
and welcome to a new issue of the IALE-OZ Newsletter. This
issue contains thesis abstracts for two IALE-Oz members. Rodney
van der Ree presents an outline of his work on arboreal marsupials
in the linear woodland remnants of northern Victoria, and George
Perry presents the outcomes of his work modelling landscape-level
vegetation dynamics in New Caledonia. This issue also includes
information on an inaugural Australian Ornithological Conference
to be held at Charles Sturt University in Bathurst, NSW later
this year.
Thank
you to everyone who contributed to this issue of the newsletter.
Contributions for the next issue will be sought in early June,
although you are welcome to send them in at any time throughout
the year. Feedback, comments and suggestions regarding the
newsletter are also welcome.
Please
contact:
Amy
Hahs a.has@pgrad.unimelb.edu.au
Diane
Pearson dpearson@gis.ntu.edu.au
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MEMBERSHIP
REMINDER
The year
2001 sees IALE-OZ launched firmly into its second year of operation.
This is a great time to show your support for this fledgling chapter
by ensuring your membership and contact details are up to date.
Current
membership for the Australasian Chapter stands at 30, with ten
members yet to renew their subscription. Benefits of membership
include: subscription to the IALE Bulletin (6 times a year), the
IALE-OZ Newsletter (4 times a year), and reduced subscription
rates to the journal Landscape Ecology, all of which contribute
to your up-to-date knowledge of things that are happening in this
exciting area of research.
If you
need a new membership form, or wish to update your contact details,
please contact the Membership Secretary:
Diane
Pearson - Email: dpearson@gis.ntu.edu.au
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Ph.D.
Thesis Abstract
ECOLOGY OF ARBOREAL
MARSUPIALS IN A NETWORK OF REMNANT LINEAR HABITATS
Linear
strips of vegetation set within a less-hospitable matrix are common
features of landscapes throughout the world. Depending on location,
form and function, these linear landscape elements include hedgerows,
fencerows, shelterbelts, roadside or streamside strips and wildlife
corridors. In many anthropogenically-modified landscapes, linear
strips are important components for conservation because they
provide a large proportion of the remaining wooded or shrubby
habitat for fauna. They may also function to provide connectivity
across the landscape. In some districts, the linear strips form
an interconnected network of habitat.
The spatial
configuration of remnant habitat (size, shape and arrangement)
may influence habitat suitability, and hence survival, of many
species of plant and animal in modified landscapes. Near Euroa
in south-eastern Australia, the clearing and fragmentation of
temperate woodlands for agriculture has been extensive and, at
present, less than 5% tree cover remains, most of which (83%)
occurs as linear strips along roads and streams. The remainder
of the woodland occurs as relatively small patches and single
isolated trees scattered across the landscape. As an assemblage,
arboreal marsupials are woodland dependent and vary in their sensitivity
to habitat loss and fragmentation.
This thesis
focuses on determining the conservation status of arboreal marsupials
in the linear network and understanding how they utilise the landscape
mosaic. Specifically, the topics examined in this thesis are:
(1)
the composition of the arboreal marsupial assemblage in linear
and non-linear woodland remnants;
(2)
the status and habitat preferences of species of arboreal marsupial
within linear remnants; and
(3)
the ecology of a population of the Squirrel Glider Petaurus
norfolcensis in the linear network, focusing on population dynamics,
spatial organisation, and use of den trees.
The arboreal
marsupial fauna in the linear network was diverse, and comprised
seven out of eight species known to occur in the district. The
species detected within the strips were P. norfolcensis, the Sugar
Glider Petaurus breviceps, Common Brushtail Possum Trichosurus
vulpecula, Common Ringtail Possum Pseudocheirus peregrinus, Brush-tailed
Phascogale Phascogale tapoatafa, Koala Phascolarctos cinereus
and Yellow-footed Antechinus Antechinus flavipes. The species
not detected was the Feathertail Glider Acrobates pygmaeus. Survey
sites in linear remnants (strips of woodland along roads and streams)
supported a similar richness and density of arboreal mammals to
sites in non-linear remnants (large patches or continuous tracts
of woodland nearby). Furthermore, the combined abundance of all
species of arboreal marsupials was significantly greater in sites
in the linear remnants than in the non-linear remnants. This initial
phase of the study provided no evidence that linear woodland remnants
support a degraded or impoverished arboreal marsupial fauna in
comparison with the non-linear remnants surveyed.
Intensive
trapping of arboreal marsupials within a 15 km linear network
between February 1997 and June 1998 showed that all species of
arboreal marsupial (except A. pygmaeus) were present within the
linear strips. Further analyses related trap-based abundance estimates
to measures of habitat quality and landscape structure. Width
of the linear habitat was significantly positively correlated
with the combined abundance of all arboreal marsupials, as well
as with the abundance of P. norfolcensis and T. vulpecula. The
abundance of T. vulpecula was also significantly positively correlated
with variation in overstorey species composition, Acacia density
and the number of hollow-bearing trees. The abundance of P. norfolcensis
was positively correlated with Acacia density and canopy width,
and negatively correlated with distance to the nearest intersection
with another linear remnant. No significant variables were identified
to explain the abundance of P. tapoatafa, and there were insufficient
captures of the remaining species to investigate habitat preferences.
Petaurus
norfolcensis were resident within the linear network and their
density (0.95 - 1.54 ha-1) was equal to the maximum densities
recorded for this species in continuous forest elsewhere in south-eastern
Australia. Rates of reproduction were also similar to those in
continuous forest, with births occurring between May and December,
a mean natality rate of 1.9, and a mean litter size of 1.7. Sex
ratios never differed significantly from parity. Overall, the
population dynamics of P. norfolcensis were comparable with published
results for the species in contiguous forest, clearly suggesting
that the linear remnants currently support a self-sustaining,
viable population.
Fifty-one
P. norfolcensis were fitted with radio transmitters and tracked
intermittently between December 1997 and November 1998. Home ranges
were small (1.3 - 2.8 ha), narrow (20 - 40 m) and elongated (322
- 839 m). Home ranges were mostly confined to the linear remnants,
although 80% of gliders also utilised small clumps of adjacent
woodland within farm paddocks for foraging or denning. Home range
size was significantly larger at intersections between two or
more linear remnants than within straight sections of linear remnants.
Intersections appeared to be important sites for social interaction
because the overlap of home ranges of members of adjacent social
groups was significantly greater at intersections than straight
sections. Intersections provided the only opportunity for members
of three or more social groups to interact, while still maintaining
their territories.
The 51
gliders were radiotracked to 143 different hollow-bearing trees
on 2081 occasions. On average, gliders used 5.3 den trees during
the study (range 1 - 15), and changed den trees every 4.9 days.
The number of den trees used by each glider is likely to be conservative
because the cumulative number of den trees continued to increase
over the full duration of the study. When gliders shifted between
den trees, the mean distance between consecutive den sites was
247 m. Den trees were located throughout a glider's home range,
thereby reducing the need to return to a central den site and
potentially minimising energy expenditure. Dens were usually located
in large trees (mean diameter 88.5 cm) and were selected significantly
more often than expected based on their occurrence within the
landscape.
The overall
conclusion of this thesis is that the linear network I studied
provides high quality habitat for resident populations of arboreal
marsupials. Important factors influencing the suitability of the
linear remnants appear to be the high level of network connectivity,
the location on soils of high nutrient status, the high density
of large trees and an Acacia understorey. In highly fragmented
landscapes, linear habitats as part of the remaining woodland
mosaic have the potential to be an integral component in the conservation
of woodland-dependent fauna. The habitat value of linear strips
of vegetation should not be underestimated.
Rodney
van der Ree Email: rvdr@unimelb.edu.au
School of Ecology and Environment, Deakin University, Clayton,
Victoria, 3168.
Present Address: Australian Research Centre for Urban Ecology
(ARCUE). c/- School of Botany, University of Melbourne, Victoria,
3010.
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Ph.D.
Thesis Abstract
SPATIAL MODELLING
OF LANDSCAPE-LEVEL VEGETATION DYNAMICS, MONT DO, NEW CALEDONIA
The
coniferous tree Araucaria laubenfelsii (Araucariaceae) forms a
key component of vegetation structural assemblages on ultramafic
substrate at Mont Do, New Caledonia; it is listed in the conifer
red book as a Category 3 species (‘restricted or scattered range’).
A. laubenfelsii is the sole species on Mont Do to be found both
as an emergent in maquis (shrubland) and as a common canopy species
in adjacent rainforest patches. The vegetation on Mont Do
forms a spatially complex mosaic of maquis, maquis with emergent
Araucaria laubenfelsii, Araucaria woodland, and rain forest (both
with and without A. laubenfelsii). The density of A. laubenfelsii
across the landscape is highly variable, from areas of maquis
where the species is absent, to areas where stem densities are
very high. In many places the boundary between rain forest
patches and the maquis is extremely abrupt. A spatially
explicit model, including the processes of vegetation succession,
seed production and dispersal and fire spread, was developed to
explore the mechanisms of pattern formation and maintenance for
the 100 ha area comprising the Mont Do Reserve. The model
uses a grid-based framework within which succession is simulated
using a state and transition approach incorporating spatially
explicit seed production and dispersal. Fire spread is modelled
using a percolation algorithm.
Analysis
of the model suggests that infrequent large fire events are responsible
for driving landscape dynamics. Although the current landscape
pattern is a complex mosaic of maquis and forest patches, palynological
evidence suggests that prior to human colonisation of New Caledonia
it was probably forest-dominated. Model results show that
under altered fire regimes the landscape may rapidly ‘switch’
from being forest-dominated to being a maquis-forest mosaic.
Large fire events, triggering positive feedback loops at several
spatial scales, act to reinforce this change by increasing the
average size of fire events and hence the flammability of the
landscape as a whole. Nevertheless, the temporal distribution
of fire events (relative to each other) may be as important as
simple increases in fire size in driving landscape change.
The current abundance of the intermediate vegetation types is
probably attributable to higher fire frequencies over the last
two hundred years. The ultramafic substrate on Mont Do causes
limiting growth conditions and hence succession in the landscape
occurs very slowly. As a result the time spent in fire-prone
successional stages is lengthened and this has a significant influence
on landscape dynamics. The nature of the substrate on Mont
Do possibly differentiates it from similar systems where succession
occurs more rapidly, and where a more rapid progression through
the maquis stage might lead to a higher likelihood of a return
to forest.
Model
results suggest that the landscape may be at a point from which
it could move to either a maquis-dominated condition (especially
if a series of fire events occur in the next 100-200 years), or,
in the absence of disturbance, could move towards a forest-dominated
condition. The heavy recruitment of A. laubenfelsii into
the maquis from forest patches suggests a move towards a more
heavily forested landscape composition. The persistence
of the intermediate vegetation types seems uncertain under either
of these scenarios. However, even if the abundance of closed
forest does increase it seems unlikely that A. laubenfelsii will
disappear from Mont Do. Given sufficient light levels, A.
laubenfelsii can persist in forest environments, and the species
tends to be found on drier ridges (where other species can not
dominate the canopy) and within light gaps created by disturbance
events such as lightning strike. Conversely, A. laubenfelsii
would probably persist in a maquis-dominated landscape, although
its distribution may be restricted to fire-protected areas such
as rocky-outcrops.
Map
of New Caledonia illustrating the location of the large ultramafic
sheet in the south of the island, the Mont Do study site, and
the location of the New Caledonian archipelago relative to Australia
and New Zealand (map drafted by Chandra Jayasuriya).
A
screen snapshot of the spatial landscape model in operation.
The primary graphics window displays and updates the vegetation
map. Other landscape and fire history information is also
provided, as is a bar graph, which shows the relative abundance
of the different vegetation types in the landscape.
George
Perry
Email: george.perry@kcl.ac.uk
Dept. of Geography, University of Melbourne
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THE
INAUGURAL AUSTRALIAN ORNITHOLOGICAL CONFERENCE
Charles Sturt University, Bathurst, NSW 4th - 7th December 2001
The
AOC is intended to provide a forum for the exchange of information
and ideas between people involved in avian-based research and
conservation throughout Australasia. Designed to complement the
4-yearly Southern Hemisphere Ornithological Congress, it is anticipated
that the AOC will be held every two years and become the main
scientific event on the Australian ornithological calendar.
The
conference program will span three days and feature topical symposia,
poster sessions, workshops and round-table discussions in addition
to regular contributed papers.
Of
particular interest to landscape ecologists are the anticipated
symposia on:
- "Birds
is degraded landscapes: declines, consequences and management
implications"
- "Bird-habitat
relationships: a hierarchy of scales"
For
further information contact:
AOC 2001 Conference Secretariat
Conference Solutions
PO Box 238
Deakin West ACT 2600
Phone: 02 6285 3000
Fax: 02 6285 3001
E-mail: birds@con-sol.com
Website: http://clio.mit.csu.edu.au/aoc2001
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