Investigators: R. H. Crozier1 and
P. Schmid-Hempel 2
1Department of Biochemistry & Genetics, La Trobe University
2Ecology Group, ETH, Zürich
A pilot study on ants and their relationships
with parasites involved a stay in Folwer's Gap Field Station
by Prof.P.Schmid-Hempel, in November 1998
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Investigators: David Dunkerley
School of Geography and Environmental Science, Monash University,
Clayton, VIC 3168
Rainfall simulation experiments begun in
1997 have been continued, in order to expand the available database
and to explore further the role of gibbers, organic litter,
and chenopod shrubs in influencing hydrologic and erosional
behaviour. In a continuation of work on the properties of the
immediate environs of chenopod shrubs, extensive work has been
carried out in order to define what may be called the 'zone
of influence' that surrounds these plants. Because of the dispersal
of litter, organic matter and nutrients, and the spread of root
channels and faunal burrowing, the presence of a shrub has been
shown to be associated with altered hydrologic behaviour across
a zone extending well beyond the limits of the canopy. To explore
this, detailed transects running from the stems of shrubs and
into the shrub interspace beyond the canopy have been sampled
at close intervals. Parameters measured to date on these radial
transects include soil shear strength, soil bulk density, and
soil infiltration rate. Miniature cylinder infiltrometers (10
cm diameter) have been used to measure the infiltration rates.
Because the soil surfaces are frequently quite fragile, and
carry crusts that could be disturbed by the installation of
conventional cylinder infiltrometers, the miniature devices
have been bonded to the soil surface with a silastic adhesive.
Some soil properties, such as bulk density, are relatively uniform
with increasing radial distance from the stem. In contrast,
shear strength is very low beneath the canopy, reaches a peak
near the canopy margin, and declines again into the shrub interspace.
The peak in strength appears to be associated with biological
soil crusts. Infiltration rates are most rapid near the stem,
and decline rapidly with increasing radial distance. The pattern
of this decline is best fitted by a power function model of
the form
ln (infiltration rate, mm/h) = 4.228 - 0.425
ln (stem distance, cm)
This relationship, based on 71 infiltration
tests, is statistically significant (p = 0.0001). It confirms
that infiltration rates remain considerably above the lower
shrub interspace value even at locations well beyond the boundaries
of the plant canopy. For the bluebush specimens studied, the
mean canopy radius was approximately 46 cm. Thus, the conventional
use of canopy dimensions in order to parameterise the shrub
environment may not adequately reflect this larger 'zone of
influence'. Testing of the power function model in the explanation
of hydrologic response of runoff plots containing shrubs is
underway.
Soil bulk density has been determined using
the pit-and-membrane method, modified by the use of an electronic
soil-surface indicator probe that allows very precise filling
of the pit to the original soil surface level. Similarly, infiltration
rates are determined using cylinder infiltrometers in association
with an electronic water level probe that permits ponding depths
to be maintained very precisely. Water uptake rates are typically
monitored at 60-second intervals for 30-60 minutes, in order
to estimate the final infiltration rate. A remaining issue in
this work is the correction of infiltration data for lateral
seepage. At present, a simple geometric model has been applied
to correct for this, but the procedure requires additional testing
and validation.
The field program is supported by funding
from the Australian Research Council.
Publications:
Dunkerley D.L. 1998. The effects of plant
litter on sediment detachment and transport in the arid zone:
rainfall simulation experiments at Fowlers Gap, NSW. Paper presented
at the Eighth Biennial Conference, Australian and New Zealand
Geomorphology Group, Goolwa, SA, November 15-20, 1998. Conference
Abstracts p.18. (Compiler Prof. R. Bourman, University of South
Australia).
Investigator: Adrian Fisher, School of Geography, UNSW, Sydney, NSW 2052
Gibson (1996) observed a shallow dipping
Early Cretaceous sediment, on the eastern edge of the Barrier
Ranges on Fowlers Gap Station. It has subsequently been termed
the Telephone Creek Formation. Iron and silica cemented pods
and horizons of ferricrete and silcrete were found to be dipping
within this sediment. The small discontinuous outcrops of silcrete
and ferricrete have a probable origin from groundwater discharge.
The Telephone Creek Formation is unconformably overlying the
Devonian Nundooka Sandstone, and is blanketed by the red clay
sediments of the Bancannia Basin.
After correlation with the results of Baarda
(1968) on the Planet Bancannia South No. 1 bore, the Formation
appears to be a sequence (from youngest to oldest) of a finely
laminated micaceous shale, through to a micaceous sandy conglomerate
to a, micaceous grey shale. Since its deposition in fluvial
and lacustrine conditions, the Formation has been deformed by
down warping of the Bancannia Basin, or by tectonics. A fault
offsetting the formation may exist in the area where Fowlers
Creek cuts through the Barrier Ranges. Gibson (1997, 1998a,
1998b) has investigated the post-cretaceous tectonics.
Some high level beveled surfaces within
the Barrier Ranges appear to be the surface trace of the Devonian
- Cretaceous unconformity. Due to this surface, and extensive
remnant surface gravel from the Formation existing across both
sides of the Barrier Ranges, the Telephone Creek Formation seems
to have previously had a much larger distribution. Outcrops
are also present on the western side of the ranges, situated
on Floods Creek Station. Mesozoic, possibly Early Cretaceous
plant fossils were found in a ferricrete bed within this Floods
Creek outcrop. This suggests strongly that the mesas and their
underlying sediments are not part of the Tertiary duricrust,
and brings into doubt the naming by Neef et al. (1995)
of many outcrops of Tertiary sediments that exist in the area.
Ward et al. (1969) had previously
identified Tertiary silcretes on Fowlers Gap Station. These
small outcrops exist on the western side of the Station in Sandstone
Paddock. They appear to be extremely different to the silcretes
found within the Cretaceous sediments. A satisfactory explanation
for the existence of the two varieties of silcretes has not
yet been found.
References
Baarda, F., D., 1968, Planet Bancannia South
No. 1 completion reportfor Planet Exploration Company Pty. Ltd.
Cundill Meyers & Associates Pty. Ltd. (unpublished)
Fisher, A.G., 1997, An investigation of
silcrete, ferricrete and the Telephone Creek Formation at Fowlers
Gap Arid Zone Research Station, Western New South Wales. Unpublished
Honours Thesis, School of Geography, University of NSW.
Gibson, D. L., 1996, Cretaceous sediments,
tectonics, and landscape development in the northern Barrier
Ranges. In: Regolith '96, Second Australian Conference on
Landscape Evolution and Mineral Exploration, The State of the
Regolith 20. Co-operative Research Centre for Lanscape
Evolution and Mineral Exploration, (CRC LEME), Perth/Canberra.
Gibson, D. L., 1997, Recent Tectonics and
landscape evolution in the Broken Hill region. AGSO Research
Newsletter 26, 17-20.
Gibson, D. L., 1998a, Regolith and its relationships
with landforms in the Broken Hill region, western NSW. In:
Eggleton, R. A. (ed.), The State of the Regolith, Proceedings
of the Second Australian Conference on Landscape Evolution and
Mineral exploration, Brisbane, Queensland, Australia 1996.
Geological Society of Australia Special Publication 20.
Gibson, D. L., 1998b, Post-Early Cretaceous
tectonism and landscape development in the northern Barrier
Ranges, Western NSW. Proceedings of the 14th Australian
Geological Convention, Townsville, 6-10 July.
Neef, G., Bottrill, R. S. and Ritchie, A.,
1995, Phanerozoic stratigraphy of the northern Barrier Ranges,
western New South Wales. Australian Journal of Earth Sciences,
v. 42, p. 557-570.
Ward, C. R., Wright-Smith, C. N. and Taylor,
N. F., 1969, Stratigraphy and Structure of the North-East Part
of the Barrier Ranges, New South Wales. Journal and Proceedings,
Royal Society of New South Wales, v. 102, p. 57-71.
Investigators: Adrian Fisher, School of Geography, UNSW, Sydney, NSW 2052
Silica cemented horizons in arid zone soils
are commonly termed soil hardpans. They have been described
in many arid and semi-arid areas throughout the world. In the
United States of America Flach et al. (1973) conducted
research into hardpans for the U.S. Department of Agriculture.
They termed the silica cementation a duripan, and concluded
that they are "most extensive in soils of very easily weatherable,
noncrystalline parent materials, such as pyroclastics".
In Australia however, hardpans have been
found on a wide variety of parent materials. Most research conducted
on Australian hardpans has agreed with the hypothesis suggested
by Teakle (1936). This was summarised by Lawrie (1973), who
stated, "development of hardpans is due to the leaching
of soluble silica into the subsoil after heavy but infrequent
rains followed by long periods of intense dessication and dehydration
of silica during dry conditions". Lawrie also states that
the silica "has probably been transported in solution from
siliceous sediments and from silica released by weathering of
siliceous mantles of stone and gravel." Many researchers
also propose a relationship between the soil hardpan and residual
deep weathering profiles. Although these theories have been
established, our understanding of how soil hardpans form is
still incomplete.
Some research into hardpans at Fowlers Gap
Station has been conducted by Chartres (1982, 1983, 1985). The
work however was only preliminary, with 6 sample localities
over north-western New South Wales, 2 of which were on Fowlers
Gap Station. This differs greatly from the work done by Lawrie
who gathered 55 samples along a 100km transect, north of White
Cliffs.
The current research by myself hopes to
build on the preliminary work of Chartres, through investigating
the soil hardpans on Fowlers Gap Station, looking at both micromorphological
and chemical properties of the hardpan soils. However, it is
hoped that the proposed research will be able to clarify the
relationship between soil hardpans and geomorphic position,
through the detailed approach of Lawrie.
REFERENCES
Chartres, C.J., (1982), The pedogenesis
of desert loam soils in the Barrier Range, western New South
Wales. I: Soil parent materials. Australian Journal of Soil
Research, 20, 269-281.
Chartres, C.J., (1983), The pedogenesis
of desert loam soils in the Barrier Range, western New South
Wales. II: Weathering and soil formation. Australian Journal
of Soil Research, 21, 1-13.
Chartres, C.J., (1985), A preliminary investigation
of hardpan horizons in north-west New South Wales. Australian
Journal of Soil Research, 23(2), 325-337.
Flach, K.W., Nettleton, W.D. and Nelson,
R.E., (1973), The micromorphology of silica-cemented soil horizons
in western North America. p715-729 In: Rutherford, G.K.
(ed.) Soil Microscopy; Proceedings of the fourth international
working-meeting on soil micromorphology. The Limestone Press,
Kingston, Ontario.
Lawrie, J. W. (1978) Hardpans in Western
New South Wales, Australia. Proceedings of the First International
Rangeland Congress.
Teakle, L.J.H., (1936), The red and brown
hardpan soils of the acacia semi-desert scrub of Western Australia.
Journal of Department of Agriculture Western Australia, 13,
480-499.
Investigator: Ben Macdonald, School of Geography,
UNSW, Sydney, NSW 2052
The properties of and linkages between sorted-step,
weakly sorted step, weakly contoured, and contour chenopod patterned
ground were investigated. This complex association of patterned
ground occurred on a pediment on the eastern flank of the Barrier
Ranges in arid western New South Wales. The rehabilitation and
management of these forms of chenopod patterned ground is also
considered by assessing the impact of contour furrowing upon
a similar area of contour patterned ground to the north.
The patterned ground complex were described
using plant cover and microtopography from line transect data,
low level air-photo interpretation and soil data from profiles
within 4 trenches, sampled to include a full range of surface
conditions across each of the four areas. Within the contour
furrowed area, two sites, treated and untreated were similarly
described, except the soil data was collected form points.
The accumulation of aeolian material during
the Quaternary resulted in the formation of soils which have
a high clay content with a shrink swell potential, that developed
into gilgais. The topography of the pediment influenced the
movements of these soils and produced the microtopography that
shape the different forms of patterned ground at the site.
The concentration of the coarse fraction
within the run-off areas is caused by the hydrological mosaic
and soil water movement and the resulting up thrusting of stones
within the run-off areas. The decreasing coarse fraction content
with increasing slope length is explained by geomorphological
and anthropogenic history of the site.
The pediment is made up of two geomorphic
surfaces, the relict upper slope (sorted step patterned ground)
and the lower fan slope (contour patterned ground). The pedogenic
and the geomorphic history of the pediment area inextricably
linked, and the upper slope soils have under gone more pedogenesis
than the lower slope. There is a conspicuous absent of the red-brown
hardpans from the soils of the site despite conditions conducive
to their formation. The key in the control in the patterned
ground system is the amount of water available for redistribution.
The geomorphology and pedology of the pediment indicated the
role of climate was an important factor in the formation of
patterned ground.
The vegetation of the pediment has been
significantly affected by the grazing history of the area. The
pediment is characteristically bare, and the progressing downslope
the amount of vegetation cover decreases by 4.01%. The covertype
associations also vary downslope, the upper site is a copperburr-saltbush
association, saltbush-copperburr association and the lowest
site is a copperburr-grass-saltbush association. The greater
amount of cover at the upper site is due to the greater amount
of the water run-off water generated compared to lower sites.
The decrease in the amount of saltbush cover is caused by the
decreasing amounts of available nitrogen within the run-off
areas. The nitrogen is fixed by algae, which grow under the
quartz gravel lag. This lag decreases downslope and thus the
saltbushes are unable to compete with the grass for the available
nitrogen pool. The bioavailability of various micronutrients
(Cu, Fe, Mn, Mo, Ni, Pb, and Zn) was found to be high but no
firm conclusions could be drawn. However there was evidence
that there is a redox differential between the run-off/run-on
areas within the chenopod patterned ground system.
The differences between run-off/run-on areas
in terms of infiltration and evaporation and evapo-transpiration
has resulted in the formation of different soil properties.
The run-off areas are "salt dumps" where soluble salts
(Ca2+, Mg2+, K+ & Na+)
are concentrated and the within the run-areas less concentrated.
All the different forms have soluble salt mosaic.
Investigator: Adam Munn and Terence J. Dawson, School of Biological Science, UNSW, Sydney, NSW 2052
Juvenile red kangaroos (Macropus rufus)
have the highest mortality rate of any population cohort during
times of environmental stress. Severe or prolonged drought for
example determines recruitment into adult populations. This
project is designed to examine the physiology of juvenile kangaroos
at their most vulnerable ages: permanent pouch exit (250 days
old) and weaning (360 days old). By looking at the thermal biology
of juveniles we can derive their base energy and water requirements
and determine how important these factors are in governing juvenile
survival. Eventually, an understanding of the major factors
influencing juvenile survival should indicate which environmental
factors are most important for regulating the size and structure
of adult populations.
Studies at Fowlers Gap over the past 30
years have suggested that food quality plays an important role
in the foraging ecology of arid zone kangaroos. This is particularly
so for the smaller, younger animals whose energy demands are
higher than adults. Work conducted at the UNSW Kensington campus
using animals obtained from Fowlers Gap is currently examining
the efficiency of juvenile and adult animals in digesting poor
quality feed. This will provide information about juvenile digestive
constraints and food requirements which can later be used in
developing and testing foraging models at Fowlers Gap.
Investigators: Gresley A Wakelin-King, Dept. Earth Sciences, La Trobe University, Bundoora, Vic.
3068
Arid zone fluvial systems are not merely
dry versions of "normal" rivers. They often carry
very coarse sediments; they have extremely flashy discharge
(very low to very high volumes of water flow); they have vegetation
growing within the channel. These and other factors make arid
zone fluvial processes qualitatively different from those in
temperate climates. However there is relatively little research
carried out on these types of rivers. Seventy percent of continental
Australia lies within the arid zone, and we cannot effectively
deal with these rivers unless we understand how they work.
A flowing river will alter its channel by
repeated feedback mechanisms until it can perform its "task"
(the transport of a given amount and size of sediment, within
a given water flow) in the most energy-efficient way possible.
Fluvial processes can alter channel slope (by depositing or
eroding sediment, or changing its planform to cover more ground
to descend the same distance); they can alter channel cross-section
(by erosion or deposition in channel or banks). Therefore where
a river’s processes cannot be directly observed, due to
its isolation and the rarity of flow events, it is possible
to understand its processes by examining channel cross-sections
and planforms along its length.
Fowlers Creek is 55 km in length, and flows
northeast out of the Barrier Ranges in far western NSW. A map
of the river has been made using 1:50,000 scale aerial photographs.
The creek has been divided into three sections: catchment, trunk,
and distributary fan; and other river and floodplain features
have been interpreted. In 1997 and 1998 I established sites
every one or two kilometers along the creek, and at each site
surveyed a channel cross section, observed geomorphological
relationships, and collected channel and bank sediment for description.
This research is being conducted on a half-time
basis and will be completed in early 2002.
1998 Research
reports