 1996 Research
reports
- Behavioural and ecological
interactions of mammalian herbivores in the arid-zone hills
- Feeding ecology of Red
kangaroos: A comparison of juveniles and adults
- Hormonal relations of
moult and breeding in White-plumed Honeyeaters
- Integrating remote sensing
techniques for geological and soil mapping investigations at Fowlers
Gap
- Effect of body size on foraging
behaviour of Euros
- Discriminating vegetation
composition with high spectral resolution imagery
- An understanding of the mechanics
controlling the form of chenopod patterned ground, western NSW:-
Completion of soil sampling and vegetation surveys
- The use of image classification
for stone distribution and shape
- Soil cation distribution
in chenopod patterned ground, arid western New South Wales, Australia
- A comparison between three
different sites of patterned ground gilgai complexes: An insight
into their formation
- Fowlers Gap station walks
- The quantitative assessment
of Bladder Saltbush (Atriplex vesicaria) rangelands using remotely
sensed imagery at Fowlers Gap Station
- Microsatellite analyses of
Phytidoponera sp. 12
- Spatio-temporal interaction
of mammalian herbivores in the arid zone
BEHAVIOURAL AND ECOLOGICAL INTERACTIONS
OF MAMMALIAN HERBIVORES IN THE ARID-ZONE HILLS.
Investigators: Cate Athey and David Croft, School of Biological Science, UNSW
Fieldwork concluded in 1996 for this study
which began at Fowlers Gap in 1994. The aim has been to investigate
the effects on the behaviour and ecology of a population of euros
(Macropus robustus) occurring in an area of overlap with
populations of other species of mammalian herbivores in the hills
of the arid zone. Euros are also known as the hill kangaroo and
previous studies have found them to associate strongly with the
slopes of hills; this is especially so of females. Euros are also
known to be relatively unsocial amongst the species of large kangaroos
and especially in comparison with introduced grazing species of
sheep and goats. As a consequence of these aspects of the behaviour
of the euro, we wish to see how unmanaged/natural populations
of euros behave in their habitat of the hills in response to the
presence of the introduced species - sheep, goats and rabbits.
At the same time we have examined the degree to which the euro
population overlaps populations of the red kangaroo and the eastern
and western grey kangaroo within the study site. Finally we have
compared the use of the area between the sexes in the euro population
to determine how males and females interact with each other and
with individuals of the populations of other species.
The study site has been broadly divided by
its topopgraphy into the flats and the hills. In general the flats
are used to stock most of the sheep because of the easier fencing
and mustering and perceived better pasture than the hills, but
sheep are also kept in paddocks in the hills. The study site at
Fowlers Gap covers an area of 3.5 x 3 km within the paddocks of
South Ridge, North Holding, Strip and South Sandstone. Sheep are
kept in all of these paddocks at different times and densities.
Feral goats and rabbits also occur in the area, and are subject
to occasional population management control.
During the three years of field work, the
following hypotheses were tested:
- That the population density and distribution
of euros will be affected by the presence of other species of
mammalian herbivores, that the density will decline in response
to an influx or overlap with another species and that the distribution
will be altered as euros shift away from the introduced species
of herbivores.
- That as a consequence of moving away from
other individuals within an overlapping area individual euros
are likely to be displaced from areas of greater vegetation cover
to poorer cover and the results of this can be measured as a trade
off between a decreased reproductive output and survival, and
an increase in home range to compensate for poorer cover.
- That the affects of overlap between euros
and individuals or populations of other kangaroo species will
be less pronounced and probably not apparent compared to that
with the introduced species.
- That individual euros will limit the time
spent associating in close proximity as in general only small
groups have been identified together in past studies. In particular,
male and female euros will limit the time that they spend together
to reproductive-related associations to minimise the time spent
overlapping in the same area and on the same resources
- That male euros benefit from a strategy of
having a larger home range than female euros, and that they gain
a nutritional benefit from grazing to a greater degree than the
female euros on the flats rather than in the hills.
- That this tendency for euros to minimise
contact and spatial overlap between themselves and other individuals,
will also be demonstrated at the water trough within the study
site. In response to increasing densities of other species in
the area, euros will alter their temporal drinking patterns and
may even consume less water to avoid overlap spatially.
The results of this study are currently being
analysed at the UNSW in Sydney.
FEEDING ECOLOGY OF RED KANGAROOS:
A COMPARISON OF JUVENILES AND ADULTS
Investigators: Amanda Bilton and Terence Dawson, School of Biological Science, UNSW
The relationship between feed intake and the
level of available food for a herbivore (often determined as plant
biomass) is called the functional response. The importance of
the functional feeding response is that it provides the key inputs
into models dealing with the dynamics of kangaroo populations
The functional response of juveniles (weaned,
young at foot) and adult red kangaroos (Macropus rufus)
were investigated for a rangeland pasture dominated by chenopod
shrubs. The investigation involved an intensive grazing trial.
The diets of the two age classes were also compared throughout
the trial. Diets and food intake rates were further examined using
an optimal foraging model based on linear programming.
Both adults and juveniles showed highly variable
intake rates in response to decreasing vegetation biomass. The
method of measurement of the vegetation was considered to be the
major contributor to this variability. The maximum food intakes
of adults and juveniles were 80 and 84 g/kg0.75.day,
approximately 30% greater than the maximum value previously recorded
for adults feeding on similar pasture. Intakes of the two age
classes were similar despite a predicted increase in metabolic
demand by the small animals. The level of biomass below which
the animals could no longer maintain intake was approximately
40 kg/ha, much lower than the value of 250 kg/ha obtained by short.
Juveniles had a higher harvesting efficiency than adults, indicating
and increased ability to maintain intake at low vegetation biomass.
Under relatively ‘good’ pasture
conditions, at the beginning of the trial, the diets of the adults
and juveniles were similar. The diets diverged as pasture conditions
deteriorated; the adults selecting a higher proportion of higher
quality plants (grasses and forbs).
The energy maximising diets predicted by the
optimal foraging model were different from the observed diets
under relatively good pasture conditions. Under relatively ‘poor’
environmental conditions the energy-maximised diets predicted
by the model were not significantly different from that observed.
The model also accurately predicted that both age classes were
in negative energy balance.
A comparison of the intake rates determined
from the functional response curves with those obtained from the
optimal foraging model was obscured by the variation in the data
from the functional response trials. Intakes determined via the
optimal foraging model, however, reflected the decrease in intake
rate and subsequent state of negative energy balance expected
as pasture biomass decreases. This signifies the optimal foraging
models potential for determining the functional response in free-range
conditions.
Further functional response studies are necessary
to determine the accurate feeding responses of juvenile animals
to declining levels of pasture biomass.
 Return to index
HORMONAL RELATIONS OF MOULT
AND BREEDING IN WHITE-PLUMED HONEYEATERS
Investigators: Bill Buttemer, Lee Astheimer,
and Karen Fildes, Dept. of Biological Sciences and Dept. of Biomedical Science, University of Wollongong
Our past surveys have revealed that White-plumed
Honeyeaters (WPH) are reproductively labile, but have predictable
moult schedules each year. In some years summer breeding occurs
extensively at Fowler’s Gap and results in moult/breeding
overlap. This situation is extremely uncommon in birds living
in highly seasonal environment and birds living in such environments
are known to have hormonal mechanisms to prevent temporal overlap
of moulting and breeding. We have just finished a series of experiments
to gain insight into the influence of breeding hormones on moult.
We compared the effects of testosterone on moulting rates of WPH
males to those of moulting House Sparrows (HS). Males of both
species were divided into two groups: experimental birds were
implanted with silastic tubes filled with testosterone, whereas
control bales were implanted with empty silastic tubes. Testosterone
suppressed moult altogether in HS but only reduced the moulting
rate by about 40% in WPH. We are now examining the effect of the
testosterone implants in thyroxine (T4) levels in these two species,
as T4 is known to be involved with moult in many avian species.
Our other ongoing experiment is examination
of the relation between testes size and testosterone production
in WPH. Our data so far reveal that adult males do not show full
gonadal regression, but instead have testes no smaller than about
50% of maximum at any time of the year. Females, by contrast,
show complete ovarian regression. We have examined the functional
state of male testes by injecting LH/RH intrajugularly in males
followed by subsequent plasma sampling 5 and 15 minutes later
to quantify LH secretion by the anterior pituitary and testosterone
production by the testes, respectively. Our analyses thus far
reveal no correlation between testes size and LH or testosterone
secretion. We are now investigating the state of sperm production
in testes as a function of gonad size.
INTEGRATING REMOTE SENSING TECHNIQUES FOR GEOLOGICAL
AND SOIL MAPPING INVESTIGATIONS AT FOWLERS GAP
Investigator: Rob Hewson, School of Applied Geology, UNSW
This research is investigating the capabilities
of thermal infrared, synthetic aperture radar and airborne geophysics
remote sensing techniques to discriminate geological and soil
units in an arid environment. Airborne high-resolution thermal
infrared (TIMS) and radar imagery (AIRSAR) has been integrated
with airborne radiometric and magnetic data to discriminate key
minerals and structural/topographic controls on the geology. Subtle
geomorphological and colluvial/alluvial features have also been
identified in this research. Detailed fieldwork in 1994 and 1995
have previously mapped mineralogical and soil textural variations
over the area surveyed by thermal and radar imagery. Fieldwork
in 1996 investigated the anomalies identified from airborne radiometric
and magnetic data.
A short field trip was conducted at Fowlers
Gap in November 1995 to ground truth interpretations made from
airborne radiometric and magnetic data obtained from the Australian
Geological Survey Organisation. Thirteen survey lines were measured
with a portable Gamma ray spectrometer over anomalous features
and boundaries identified from radiometric data. Magnetic susceptibility
measurements were also obtained from soil and surface scree deposits
to assist the interpretation of aeromagnetic data. A final groundtruthing
of TIMS thermal imagery was also carried out in November.
The TIMS data was corrected for atmospheric
effects and reprocessed into thermal emissivity data. Laboratory
measurements of thermal infrared reflectance (FTIR) spectra for
a selection of Fowlers Gap soils and rocks were obtained from
NASA’s JPL and John Hopkins University. These FTIR measurements
were resampled into the six bands measured by the TIMS thermal
infrared scanner to assist in the interpretation of the processed
emissivity image data. The limited FTIR laboratory sampling of
Fowlers Gap soils suggested that grain size effects can be observed
from thermal infrared scanners such as TIMS and the future ASTER
satellite. Spectral unmixing of the TIMS data produced four endmembers
or ground cover components in the area: quartz, shales/clays,
dry vegetation on fine soils/sediments, and green vegetation on
fine soils/sediments.
Airborne radiometric data has been proved
to be strongly influenced by alluvial processes at Fowlers Gap,
particularly on the floodplains of the Fowlers Gap Creek northeast
of the Picnic Creek/Silver City Highway crossover (Conservation
paddock). Shales and phyllites are particularly well defined by
the potassium and thorium radiometric channels. The aeromagnetic
data tends to show deeper structural features and boundaries however
an alluvial fan pattern, similar to the radiometric anomaly, is
observed on the floodplains of Fowlers Gap Creek. Ironstone rich
piedmonts are also observed in the aeromagnetic data where maghermite
may be developed.
Integration of the radiometric, radar and
thermal datasets has been shown to provide a more complete geological
and geomorphological interpretation than when the datasets are
interpreted separately. The unmixed TIMS data identifies both
the shale and clay rocks and soils while the radiometric data
identifies the potassium-bearing shales/phyllites. The radiometric
data also detects minerals at a greater depth than the TIMS imagery
and identified shales/phyllites underneath transported quartzite/sandstone
scree. Soil and colluvial sediment textures interpreted from multi-wavelength
AIRSAR images compares favourably with the coarse grained quartz/sandstone
scree covered piedmonts identified from TIMS images.
EFFECT OF BODY SIZE ON FORAGING BEHAVIOUR OF EUROS
Investigators: Monika Klede1, David Croft2, Udo
Ganslosser1
1Institute for Zoology, University of Erlangen-Nürnberg;
2 School of Biological Science, UNSW
A five and a half months study was conducted
at Fowlers Gap to investigate aspects of the feeding ecology of
the euro (Macropus robustus erubescens) in relation to
differences in body size. The aim of the study was to relate food
quantity and composition to the euro's energy requirements and
digestive physiology and to relate foraging behaviour, movement,
vegetation composition at feeding sites and vigilance to the individual's
size class.
Plant density and distribution were sampled
by the wandering quarter method. Plant quality was characterised
by the product of greenness and size of a plant, and by the water
content, which was sampled on a monthly basis. The behaviour of
euros while feeding was observed during dusk and dawn. In addition
data on group size and bite size of euros when feeding on different
food plants were collected.
The water content of the food plants was related
to rainfall. The quality of food plants did not differ between
the euro size classes. Mean group size was 1.8 which is smaller
than the average group size in other studies and fewer large males
with females were observed than in other studies. The scarcity
of large males could be related to an extremely dry year before
the study period (1994: 95 mm rainfall), because their number
has been found to decline in dry conditions due to high mortality.
A relationship between group size and plant distribution was found.
The more defendable a vegetation site was, the smaller the group
size. The feeding ecology of the euro was related to body size.
Large males fed on plants containing more fibre than fed on by
small males. Large males are better able to use poor quality forage
due to their relatively larger gut size. The quantity of plants
eaten was related to body size. However, quantity did not increase
in proportion to body mass but rather was better related to metabolic
rate through M0.75.
Large euros occupied habitat with relatively
low quality plants but selected the most digestible plants from
amongst these. Small euros fed in areas with relatively high quality
food. They were more selective of high quality plants than large
euros. Vigilance was related to group size and body size. The
larger the individual was then the higher its group size and level
of vigilance. The proportion of time spend moving was inversely
related to energetic costs. The frequency of walking decreased
with increasing body size. This could reflect either a large stride
length or a decrease in selecting amongst plants. Large males
with females spent less time foraging than those alone. Males
with females appear to trade-off foraging against mate acquisition
and defence.
DISCRIMINATING VEGETATION COMPOSITION WITH
HIGH SPECTRAL RESOLUTION IMAGERY
Investigator: Megan Lewis, Department of Environmental Science and Management, The University of Adelaide
This research is evaluating the use of airborne
scanner imagery of high spatial and spectral resolution for discriminating
and mapping vegetation composition in arid landscapes. Fowlers
Gap provides the setting for the work, which is being conducted
towards a PhD by Megan Lewis in the School of Geography, University
of New South Wales, and supervised by Associate Professor Tony
Milne. The study is comparing a range of satellite and airborne
image types including Landsat Thematic Mapper, airborne video,
Geoscan II airborne scanner and CASI (Compact Airborne Spectrographic
Imager) all acquired over Fowlers Gap from 1993 to 1996.
Ecological information is being extracted
from the imagery using conventional processing techniques such
as classification, and newer approaches such as spectral mixture
analysis, matched filtering and spectral matching, which aim to
identify and quantify sub-pixel components of the landscape. The
study places considerable emphasis on calibration of image components
against quantitative field data.
1996 was the last season of field work and
image acquisition for this project. CASI airborne imagery was
acquired in April in a 25 x 2 kilometer swath over a range of
Fowlers Gap land systems, and 90 ground sites sampled in March
and May. The imagery is at 3 metre resolution and has 19 narrow
wavebands in the visible and near infra-red portions of the spectrum,
and shows considerable spatial and spectral information about
soil, rock and vegetation types. Visible and near infra-red reflectance
spectra of the dominant vegetation species, and of soils and rocks
at the field sample sites were collected with a FieldSpec spectroradiometer
to provide reference standards against which the imagery can be
calibrated, and the spectral components identified.
Earlier sections of the work are in press
or being prepared for publication. The land cover classification
using "wet" and "dry" images from January
and June 1993 successfully discriminated nine vegetation associations
and related these to an objective vegetation classification. The
vegetation classes mapped by the imagery also successfully predicted
field cover classes for 50 independent verification samples. Spectral
unmixing of the same imagery mapped sub-pixel abundances of photosynthetic
and non-photosynthetic vegetation, soil, exposed rock and the
quartz pebbles that that are a characteristic feature of many
Fowlers Gap land systems. Linear regressions were established
between image estimates of most of these components and field
measurements of percentage cover. The distribution of photosynthetic
vegetation component changed dramatically between the wet summer
of 1993 and the subsequent dry winter. Despite the 18 spectral
bands of the Geoscan imagery acquired in January 1993 only one
vegetation component could spectrally identified, since most perennial
and ephemeral species were actively growing a the time and had
similar spectral characteristics. However, because of the narrow
short-wave infra-red bands of this imagery which show absorptions
characteristic of specific minerals, several soil and rock types
could be distinguished.
Trials with the airborne video system showed
it s value as a reconnaissance mapping and land assessment tool,
and established correlations between image and field estimates
of tree and ground covering vegetation at specific sample sites 2,3,4. However, because of the calibration required
to relate field and image estimates of cover, the airborne video
is most useful as an adjunct rather than replacement for ground
data collection.
References:
Lewis, M.M. Numeric classification
as an aid to spectral mapping of vegetation communities. (In review)
Grierson, I.T. and Lewis, M.M. (1995).
Airborne video - an adjunct to ground studies for rangeland remote
sensing. Proc. 2nd Northern Australian
Remote Sensing and Geographic Information Systems Forum, 18-20
July 1995, Darwin, 165-170.
Grierson, I.T. and Lewis, M.M. (1995).
Video remote sensing. GIS User 13:33-35.
Grierson, I.T. and Lewis, M.M. Evaluation
of arid land systems using airborne video. Geocarto International (Accepted March 1996, in press).
AN UNDERSTANDING OF THE MECHANICS CONTROLLING THE
FORM OF CHENOPOD PATTERNED GROUND, WESTERN NSW:- COMPLETION OF
SOIL SAMPLING AND VEGETATION SURVEYS
Investigator: Ben Macdonald, School of Geography, UNSW
The aim of this project is to use the soils
physical and chemical properties to understand the processes controlling
the form of different areas of patterned ground at Fowlers Gap
Station. During the first two months of session two (1996), fieldwork
was carried out at Fowlers Gap Station. Below is an outline the
work completed to this date.
Previsional study sites were selected after
a detail search of the 1986 1:10,000 Fowlers Gap Station air-photo
set for areas of patterned ground, which would fit the project
criteria. These previsional study sites were reduced to a single
site, by field checking during 1995-6, within Hotel Paddock. The
study site was located within this paddock because
it occurred on a relict alluvial fan
encompassed four different forms of patterned
ground
vehicular access was possible due to a
power line road, and
at the time of the completion of the vegetation
surveys was under the minimal influence of the pio-sphere
effect.
A series of 4 trenches were dug into the four
different forms of patterned ground within the Hotel Paddock site.
The depth of each of the trenches was to be 2m, but the front-end
loader did not have the sufficient power to complete the task.
The trenches as a result were of varying depths between and within
each individual trench. The lengths of each of the trenches were
also of vary distances, because it was determined by the spacings
of the vegetated and bare areas of the patterned ground which
occurred at the trench sites. The alignment of the trenches upon
the surface of the relict fan is such that the trenches are on
roughly placed on transect in a down-slope direction.
The final soil sampling strategy was decided
upon after the inspection of each of the trench sites, which was
that,
a minimum of 14 soil sampling sites would
located on one of the side walls of the trenches,
the location of these 14 sampling sites would
be within the centre of the bare and vegetated zones and at the
boundaries of these zones,
samples would be taken at constant 10 cm intervals
to depth and the first 10 cm interval would be sub-sampled, to
include variations due to cryptogamic crusts, at 1, 2.5, 5, and
10 cm from the soil surface,
the samples taken would not be biased and
would include coarse fraction as well as fine fraction, and
where possible auguring through the floor
of the trench at each of the 14 soil sampling sites was carried
out to compensated for the short comings of the tractor and allowed
for soil samples to be taken from deeper in the profile
The soil samples were placed in snap-locked
bags, the air evacuated and transported back to Sydney for laboratory
analysis. At every sample site detailed profile description using
McDonald et al., (1990). A vegetation survey using
a modified line-intercept method was conducted at each of the
trench areas. The samples and data collected from this fieldwork
will be analysed and hopefully completed during 1997. I would
to thank all the station staff and researchers for making my stay
most enjoyable and to all those that came out into the field and
give me their assistance.
References
McDonald, R. C., Isbell, R. F., Speight,
J. G., Walker, J. and Hopkins, M. S., 1990. Australian soil
and land survey. Vol. 1 Field Handbook, 2nd Ed. Inkata Press,
Sydney.
THE USE OF IMAGE CLASSIFICATION FOR STONE DISTRIBUTION
AND SHAPE
Investigators: Ben Macdonald and Allan Evans, School of Geography,
UNSW.
The measurement of the coarse fraction of
soils and in streambed deposits is not a precise science. There
is still disagreement in the literature about the most practical
ways to gain statistically acceptable measurements (Dunkerly,
1994). Gale and Hoare (1992) methods of bulk sampling has been
refuted by Dunkerly (1994) as being insensitive to some aspects
relating to stone parameterisation and that their method is physically
impossible to carry out.
Dunkerly (1995) however advocates the use
of mean diameters weighting by stone surface area and perimeter
length as a better parameterisation of stone geometry. Dunkerly
(1995) states that "these weighting factors have the advantage
that they relate closely to stone characteristics relevant to
slope hydrology and erosion processes". Another advantage
of Dunkerly’s (1995) method is that sampling time is very
quick compared to other methods.
The aim of this current research is to improve
Dunkerly’s (1995) method by using image classification to
improve the speed of which the data can be analysed. At the present
time the research has been centred on the refinement of the computer
software for the image analysis of the stone shape and size. Once
this is completed trials will begin in the School of Geography’s
out door loading area using stones and soil collected from Fowlers
Gap.
These trials will be used to find the ideal
system set-up; some aspects are outlined below;
the use of digital imagery vs standard
photographic techniques
the resolution requirements for the software,
method of camera mounting, and
the problem of overlapping stones.
Once the bugs and problems have been removed
from the system, field trails will begin at Fowlers Gap to test
if the method is robust in the real world. It is believe this
method will further the research into the geomorphic evolution
of the physical landscape.
References
Dunkerley, D.L., 1994. Bulk sampling
of coarse clastic sediments for particle size analysis: a comment.
Earth Surface Processes Landforms, 19:255-261.
Dunkerley, D.L., 1995. Surface stone
cover on desert hillslopes; parameterizing characteristics relevant
to infiltration and surface runoff. Earth Surface Processes Landforms,
20:207-218.
Gale, S.J. and Hoare, P.G., 1992.
Bulk sampling of coarse clastic sediments for particle size analysis.
Earth Surface Processes Landforms, 17:729-733.
SOIL CATION DISTRIBUTION IN CHENOPOD PATTERNED GROUND,
ARID WESTERN NEW SOUTH WALES, AUSTRALIA
Investigators: Ben Macdonald1, Mike Melville1,
and Ian White2
1School of Geography, UNSW; 2CRES, ANU
The study of the origins and characteristics
of patterned ground in arid Australia has generally been confined
to the relationship between the hydrological regime and its control
of plant growth. There is usually only a secondary consideration
given to the soil’s chemical and physical properties and
subsequently they fail to emphasis the spatial variation of soil
properties in pattern ground. Studies do exist which have established
patterns of association between vegetation distribution and soil
properties that range in scale from that of the broad geological
province (Noy-Meir, 1974) to that of soil changes around individual
shrubs (Charley, 1972).
Our study shows the characteristics and proposes
the processes controlling of the cation distribution in chenopod
patterned ground within an enclosure in Airstrip Paddock at a
scale intermediate between that of Noy-Meir (1974) and Charley
(1972). It is believed that there is an important interrelationship
between soil hydraulic properties, soil cations, soil swelling
properties and plant spatial variation across the patterned ground
landscape.
Part of this paper was presented at "Banded
vegetation patterning in arid and semi arid environment"
symposium and the whole paper is currently under review for a
special edition of Catena.
References
Charley, J. L., 1972. The Role of
Shrubs in Nutrient Cycling. In Mckell, C.M., Blaisdell, J. P.
and Goodin, J. R. (eds) Wildland Shrubs - Their Biology and Utilization.
An International Symposium. Utah State Uni., Logan Utah, July
1971. USDA.
Noy-Meir, I., 1973. Desert ecosystems:
Environment and producers. Ann. Rev. Ecol. Syst., 4:25-51.
A COMPARISON BEWTEEN THREE DIFFERENT SITES
OF PATTERNED GROUND GILGAI COMPLEXES: AN INSIGHT INTO THEIR FORMATION.
Patterned ground gilgai complexes are one
of the most common land-units on pediments in the arid zone of
western New South Wales.
Patterned ground is a land-unit where the
spatial variation of vegetated and bare areas are rhythmically
repeated The microtopography of the complex, generated by the
gilgai phenomena, causes the redistribution and concentration
of sheet run-off into the vegetated areas. The system can support
more vegetation than that is allowed under the environment conditions.
Within the patterned ground system there are
also spatially repeated variations in the soils chemical and physical
properties. The bare areas generally are self-sealing and semi-impervious
to water and are "salt dumps". The gilgai complex has
established a system where soil moisture and osmotic gradients
all favour the flow of soil water carrying soluble salts from
the vegetated areas and the bare area’s subsoil concentrating
it into the bare areas topsoil. The patterns of soluble salt distribution
are a product of complex response as the soils become adjusted
to the preferential inputs of run-off water into the vegetated
soil due to the gilgai complex.
Most studies of patterned ground gilgai complexes
are concerned with system operation in regards to hydrology, soil
chemistry and vegetation at a small scale to macro-scale studies
relating climate to the various forms of patterning. There are
a few, if any, studies which have look at the differences between
patterned ground gilgai sites located on different parts of a
relict alluvial fan. The aim of this paper is to gauge if there
are any differences between 3 different patterned ground sites
on an alluvial fan within Hotel Paddock at Fowlers Gap Station.
It forms the basis of a preliminary study of the change in form
of patterned ground gilgai complexes in the local complex
Part of this paper was presented as a poster
paper at the Regolith ’96 : The state of the Regolith, Second
Australian Conference on Landscape Evolution and Mineral Exploration
and a full version is being submitted for the Journal of Arid
Environments.
FOWLERS GAP STATION WALKS
Investigators: Ben Macdonald, Marc Robson, Richard Jessop and Allan Evans, School of Geography,
UNSW.
The Fowlers Gap Management Committee decided
during its last sitting (September 1996) that the Station should
have a number of "ecological and educational" walks
for its many visitors. The designs of these walks are suited for
all that might visit the station, from the scouts to the more
senior members of our community. The walks have been classified
into different categories to inform the user of what he/she will
face on the track. The categories are listed below:
Category 1. The easy walk. Anybody who
can walk will find this walk very non-challenging.
Category 2. The non-easy walk. The length
of this walk might challenge older folk. The walk is generally
on flatter ground.
Category 3. The difficult walk. The length
and terrain of this walk will make this walk very challenging
for the older folk and difficult for the unfit.
Category 4. The long difficult walk. This
walk is similar to 3 but longer and harder.
Category 5. The over-night walk. This
walk is similar to 4 but it involves over-night camping. It
would be recommended that the walkers be confident of their
abilities before attempting this walk.
In all approximately five to six walks have
been planned and are ready for construction. It is proposed that
the tracks should be completed by the end of Session 1, 1997,
with the construction period over the Easter break.
The nature handbook which will accompany the
walks is designed to enlighten the visitor to the many different
aspects (eg vegetation, pastoral, geological etc.) of the station.
The directions and map for the walks will be presented upon a
separate A4 or A3 page.
It is proposed that a walk information board
should be placed in the library at the station. The board will
outline the different walks to be done at the station and a full
map of the station will also be displayed. The nature handbook
and walk notes for the different walks will be located near this
display board.
THE QUANTITATIVE ASSESSMENT OF BLADDER SALTBUSH (Atriplex
vesicaria) RANGELANDS USING REMOTELY SENSED
IMAGERY AT FOWLERS GAP STATION.
Investigators: Marc Robson and Qiming Zhou, School of Geography,
UNSW.
Shrub steppes occupy approximately 308,000
km2 of the Australian mainland. These communities are
generally composed of clumped woody perennial shrubs separated
by areas of bare ground, however, following rain these bare areas
become covered by low annuals, grasses and forbs. The shrublands
are highly regarded by the pastoral industry and have been utilised
for the grazing of sheep and cattle since the 1850’s. Coincident
with the initiation of grazing practices was large-scale land
degradation due primarily to overgrazing. Over time the community
structure of the shrublands was changed through the removal of
the perennial shrubs by stock, with subsequent erosion and replacement
by other species. This mismanagement resulted in a decline in
the carrying capacity of the rangelands as large tracts of once
productive shrublands were replaced by unpalatable vegetation
and scalded surfaces.
In order to manage the rangelands in a sustainable
way it is important to maintain the cover of perennial shrubs
as it is these plants which are primarily responsible for protecting
the soil from erosion. Thus, perennial shrubs should be regarded
primarily as maintainers of landscape stability and secondarily
as a forage resource by the land manager. The most crucial time
for the manager is in dry periods when all the preferred forage
(forbs and grasses) has been removed leaving only the shrubs to
graze. Decisions must be made, based on the state of the shrubs
and soil condition, as to when stock should be relocated. This
three year project is been undertaken with the aim of providing
the land manager with quantitative information concerning rangeland
condition with particular emphasis on the perennial shrub component.
Bladder Saltbush (Atriplex vesicaria)
was selected for this study because of its wide spread distribution
and sensitivity to grazing. This species is generally preferred
to other perennial shrubs as a source of forage when the more
palatable grasses and forbs have been eaten and as such, should
be carefully monitored to ensure its persistence during those
times in which it is being grazed. Remotely sensed satellite data
is particularly suited to this task as it can provide cost effective
and continuous information on rangeland condition at the scales
required by the pastoral industry. Problems remain however, to
relate the spectral reflectance measurements recorded by satellites
to quantitative surface variables such as cover and biomass.
This project will attempt to produce a methodology
which will allow for the extraction of quantitative surface variables
from imagery recorded by the Landsat TM sensor. This information
will be used to construct a rangeland GIS which will aid the land
manager in maintaining the stability and therefore, the productivity
of the land.
MICROSATELLITE ANALYSES OF Rhytidoponera sp.12
Investigators: W. T. Tay and R. H. Crozier, School of Genetics and Human Variation, La Trobe University, Bundoora 3083.
Developing further the population structure
findings discussed in the previous report (Tay et al., 1997),
intra- and inter- colony relatedness in the queenless ponerine
ant Rhytidoponera sp. 12 is being investigated using five
highly polymorphic microsatellite markers developed from a R.
sp 12 genomic DNA library. Ant samples collected during 1996 will
be used to study genetic distances between individual colonies
over a three-year sampling period. The gamergate (egg-laying workers)
turn-over rate in R. sp. 12 will also be investigated.
One colony was completely excavated from Conservation Paddock.
The depth of the colony was estimated at two metres. No males
were found in this colony, while approximately 460 workers were
collected. These workers were dept alive for approximately 6 months
under laboratory conditions. Workers were colour coded and egg-laying
individuals recorded. Gamergates were identified by dissection
using ovarian activity and/or spermathecal content (Pamilo et
al., 1985; Peeters, 1987). Unmated workers of R. sp.
12 from this colony were found to lay trophic eggs. This supported
the study of Pamilo et al. (1985) that laying of trophic
eggs by unmated workers were possible. This finding did not support
the observations of Peeters (1987), although different laboratory
conditions under which these nests were kept may have contributed
to the differences noted. Sperm DNA isolated from gamergates is
being used to investigate the mating behavior in R. sp.
12 through typing of the mates of the gamergates.
References:
Pamilo, P., R.H. Crozier, and J Fraser,
1985. Inter-nest interactions, nest automony, and reproduction
specialization in an Australian arid-zone ant, Rhytidoponera sp. 12. Psyche, 92(2-3):217-236.
Peeters, C.P. 1987. The reproductive
dividsion of labour in the queenless ponerine ant Rhytidoponera sp. 12. Insectes Sociaux, 34 (2):75-86.
Tay, W.T., J.M. Cook, D.J. Rowe,
and R.H. Crozier. 1997. Migration between nests in the Australian
arid-zone ant Rhytidoponera sp. 12. Revealed by DGGE analyses
of mitochondrial DNA. Molecular Ecology, In Press.
SPATIO-TEMPORAL INTERACTION OF MAMMALIAN HERBIVORES
IN THE ARID ZONE.
Investigators: Ingrid Witte and David Croft, School of Biological Science, UNSW
This project investigates the interactions
between four species of kangaroos (Red Kangaroos, Western and
Eastern Grey Kangaroos and Euros), sheep, rabbits and goats in
plains habitat and the foot-slopes of the Barrier Range at Fowlers
Gap. ‘Total grazing pressure’ and associated appropriate
stocking/control rates to conserve vegetation, soil and water
resources are examined, and the possibility of mixed species grazing
as a possible diversification of an economic base for the land-holders
in the Western Division is explored. The study aims to set up
a GIS as an aid for better management of the herbivore assemblage
in the arid zone with respect to sustainable long term use and
to allow for faster recovery from the impact of past overgrazing.
For this the interactions between the species
have been assessed since March 1994 and this will continue through
to March 1997 at both the population and the individual level
in four paddocks (410-720 ha), of which two are stocked with sheep.
The paddocks under study incorporate four different land systems
and twenty different land classes with their associated vegetation
communities. The populations of all species are monitored in space
and time by monthly population surveys, analysing, for example,
habitat use, to look at habitat segregation or overlap and at
possible interference competition, age/sex class composition etc.
The surveys have so far shown highly fluctuating
densities of Red Kangaroos, which along with sheep are the most
abundant species. Densities have ranged from as low as five to
as high as 150 individuals Km-2 in response to unpredictable
and patchy rainfall and associated poor or rich vegetation conditions,
although at ‘average’ times there appears to be a relatively
stable resident population in the study area. Red Kangaroo numbers
decreased in both paddocks stocked with sheep with the onset of
lamb dropping, suggesting avoidance by Red Kangaroos when ewes
are characteristically more dispersed within the paddock. Red
Kangaroos suffered significantly during the drought conditions
in 1995, however, allowed for higher survival, and recruitment
increased significantly. Sheep losses during all times were low
with the few cases of death due to occasional fly-strike. Lambing
rates were good to excellent.
Western Grey Kangaroos, apart from sheep the
species with the most similar habitat requirements to Red Kangaroos,
have maintained small but stable populations over time. Although
recruitment was lowered in drought conditions, they were still
more reproductively successful than Red Kangaroos and continued
to be so in 1996. This high recruitment probably offset the mortality
due to the conspicuous cases of choroid blindness in the population.
Eastern Grey Kangaroos are present in very low numbers only and
have shown a marginal impact on the plains and foot-slope habitat,
preferring the dense lateral tree and shrub cover close to large
creek beds. Euro numbers vary greatly according to environmental
conditions and only males make use of the lower lying areas, females
mostly remain in the hills and never venture past the foot-slopes
of the hills even in extremely poor conditions.
Goats are highly transient and can appear
in large mobs, their appearance often coinciding with deteriorating
conditions or a build-up in numbers. The colonisation of the area
by rabbits appears quite stable. About 120 rabbit warrens have
been mapped in the study area with most warrens situated on the
foot-slopes, along drainage channels and large gullies. All warrens
have been surveyed by counting active entrances on a three monthly
basis. The rabbit population appears to fluctuate slightly with
a change in the resource base and high rainfall lead to the collapse
of warrens.
Individual behaviour and reproductive success
of the species is followed by radio-tracking sub-samples of females.
This is done to help explaining the behaviour of the population
over time in space. Rabbits have been caught in poor and rich
conditions and tracked using fluorescent dye and an ultra-violet
light to estimate their foraging radius and thus to establish
their area of impact during changing environmental conditions.
From analysis of the habitat selection of
the species it has become evident that there is more segregation
than expected when looking at land classes and soil types. These
relationships are being modelled to determine grazing pressure
in association with estimates of vegetation resources. The variations
in the resource base in the study area over time, quantity and
quality of vegetation have been assessed using a wheel-point device
along about 40 km of transects to determine the vegetation cover
on a seasonal basis and by looking at the survivorship of plants
using Quicktake digital photography of randomly selected plots
along the same transects on a six-weekly basis. In addition vegetation
is assessed fortnightly on grazed and ungrazed plots in two of
the paddocks using digital photography. Precise estimates of resource
use have been gained by monitoring vegetation plots and water
troughs by 24-hour time-lapse video observations.
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