Dissertations / Theses on the topic 'Salinity control – Western Australia'
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Graham, Tennille. "Economics of protecting road infrastructure from dryland salinity in Western Australia." University of Western Australia. School of Agricultural and Resource Economics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0207.
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[Truncated abstract] The salinisation of agricultural land, urban infrastructure and natural habitat is a serious and increasing problem in southern Australia. Government funding has been allocated to the problem to attempt to reduce substantial costs associated with degradation of agricultural and non-agricultural assets. Nevertheless, Government funding has been small relative to the size of the problem and therefore expenditure needs to be carefully targeted to interventions that will achieve the greatest net benefits. For intervention to be justified, the level of salinity resulting from private landholder decisions must exceed the level that is optimal from the point of view of society as a whole, and the costs of government intervention must be less than the benefits gained by society. This study aims to identify situations when government intervention is justified to manage dryland salinity that threatens to affect road infrastructure (a public asset). A key gap in the environmental economics literature is research that considers dryland salinity as a pollution that has off-site impacts on public assets. This research developed two hydrological/economic models to achieve this objective. The first was a simple economic model representing external costs from dryland salinity. This model was used to identify those variables that have the biggest impact on the net-benefits possible from government intervention. The second model was a combined hydro/economic model that represents the external costs from dryland salinity on road infrastructure. The hydrological component of the model applied the method of metamodelling to simplify a complex, simulation model to equations that could be easily included in the economic model. The key variables that have the biggest impact on net-benefits of dryland salinity mitigation were the value of the off-site asset and the time lag before the onset of dryland salinity in the absence of intervention. ... In the case study of dryland salinity management in the Date Creek subcatchment of Western Australia, the economics of vegetation-based and engineering strategies were investigated for road infrastructure. In general, the engineering strategies were more economically beneficial than vegetation-based strategies. In the case-study catchment, the cost of dryland salinity affecting roads was low relative to the cost to agricultural land. Nevertheless, some additional change in land management to reduce impacts on roads (beyond the changes justified by agricultural land alone) was found to be optimal in some cases. Reinforcing the results from the simple model, a key factor influencing the economics of dryland salinity management was the urgency of the problem. If costs from dryland salinity were not expected to occur until 30 years or more, the optimal response in the short-term was to do nothing. Overall, the study highlights the need for governments to undertake comprehensive and case-specific analysis before committing resources to the management of dryland salinity affecting roads. There were many scenarios in the modelling analysis where the benefits of interventions would not be sufficient to justify action.
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Doole, Graeme John. "Value of perennial pasture phases in dryland agricultural systems of the eastern-central wheat belt of Western Australia." University of Western Australia. School of Agricultural and Resource Economics, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0213.
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Over the past thirty years, price relativities and technological development have motivated an increase in the area of land allocated to cropping, as opposed to pasture production, throughout the central wheat belt of Western Australia. Nevertheless, reducing the proportion of pasture in these rotations has challenged the future productivity of farming systems in this area. First, the frequent application of selective herbicides for weed control in extended cropping rotations has promoted the development of herbicide resistance in a number of major agricultural weeds. Second, the primary use of annual plants has promoted the development of soil salinisation by allowing a significant proportion of rainfall to recharge saline water tables. The inclusion of perennial pasture phases between extended periods of cropping may mitigate or delay these constraints to production through (a) allowing the use of costeffective forms of non-selective weed control, and (b) through creating a buffer of dry soil that absorbs leakage occurring beneath subsequent crops. This study consequently explores the value of including perennial pasture phases in dryland agricultural systems in the eastern-central wheat belt of Western Australia, accounting for benefits related to herbicide resistance and water table management. A novel computational algorithm for the solution of multiple-phase optimal control problems is developed and used to conduct a conceptual analysis of the value of lucerne (Medicago sativa L.) pasture for managing annual ryegrass (Lolium rigidum Gaudin), the primary weed in wheat belt cropping systems. The competitiveness and fecundity of annual ryegrass provide strong economic incentives to maintain a low weed population, irrespective of herbicide-resistance status. Consequently, the ineffectiveness of selective herbicides primarily reduces the profitability of cropping by motivating the adoption of more costly non-selective forms of weed control. The inclusion of lucerne in land-use rotations is only optimal in the presence of severe herbicide resistance given (a) the low efficiency of alternative weed-management practices available during the pasture phase, relative to selective-herbicide application; (b) the significant cost of establishing this perennial pasture; and (c) the high relative profitability of cereal production in the absence of resistance. The value of lucerne, relative to annual pastures, for weed management is explored in greater detail through the use of compressed annealing to optimise a sophisticated simulation model. The profitability of candidate rotations is also manipulated to account for the long-term production losses accruing to the recharge of saline groundwaters that occurs beneath them. Sequences incorporating lucerne are only more profitable than those that include annual pasture at the standard set of parameter values if (a) annual ryegrass is resistant to all selective herbicides, (b) the water table is so shallow (approximately less than 3.5 m deep) that frequent rotation with perennials is required to avert soil salinisation, or (c) sheep production is highly profitable. The value of perennial pasture is sufficient under these circumstances to overcome its high establishment cost. Consistent with intuition, these benefits are reinforced by lower discount rates and higher rates of leakage occurring beneath annual-based systems. Formulation of an effective communication strategy to report these results to producers is justified given the complexity involved in determining the true magnitude of these intertemporal benefits through alternative means, such as field trials.
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Bell, Lindsay William. "Prospects of Dorycnium species to increase water use in agricultural systems of southern Australia." University of Western Australia. School of Plant Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0033.
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[Truncated abstract] Dryland salinity is a major environmental challenge facing agriculture in Australia. One option to manage dryland salinity is the use of perennial forages that increase water use of agricultural systems. However, the current array of perennial forages is limited. Forage species that satisfy the range of climatic and edaphic environments, and production systems, in southern Australia are needed (Chapter 1). In particular, low rainfall regions lack options other than lucerne (Medicago sativa L.) (Chapter 1). The Dorycnium genus (canary clovers) contains perennial species that might be useful forage plants for southern Australia. Dorycnium are sub-shrubs and their plant form differs from current perennial forages (Chapter 1). The aim of this project was to investigate some of the agronomic traits of several species of the genus Dorycnium to explore where they might be used in Australia and how they might be integrated into agricultural systems for management of dryland salinity. First, two desktop investigations assessed the potential adaptation and role of Dorycnium species in southern Australia: a review of the current literature on the agronomic characteristics of Dorycnium (Chapter 2) and an eco-geographical analysis to explore the ecology of Dorycnium species (Chapter 3). The agronomy of Dorycnium has been previously researched mainly in New Zealand, and although this provides some indications on where and how Dorycnium might be best used in Australia, this still requires testing in Australia. In particular, the aluminium tolerance of Dorycnium species indicates that they may be more suitable for acid soils than lucerne. Little ecological data was obtained for germplasm and herbarium collection sites of Dorycnium species. Climate comparisons between the native distribution of Dorycnium species in the Mediterranean basin and Australia, using spatial aridity data and CLIMEX climate match modelling, revealed that D. hirsutum and D. rectum might be suitably adapted to the temperate pasture regions of southern Australia. Suitable germplasm of D. pentaphyllum may also exist, but subsequent investigations in this project focussed on D. hirsutum and D. rectum.
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Lewis, Marjorie Fay. "The significance of episodic recharge in the Wheatbelt of Western Australia /." Connect to thesis, 2000. http://eprints.unimelb.edu.au/archive/00000682.
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Bari, Mohammed A. "A distributed conceptual model for stream salinity generation processes : a systematic data-based approach." University of Western Australia. School of Earth and Geographical Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0058.
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[Truncated abstract] During the last fifty years mathematical models of catchment hydrology have been widely developed and used for hydrologic forecasting, design and water resources management. Most of these models need large numbers of parameters to represent the flow generation process. The model parameters are estimated through calibration techniques and often lead to ‘unrealistic’ values due to structural error in the model formulations. This thesis presents a new strategy for developing catchment hydrology models for representing streamflow and salinity generation processes. The strategy seeks to ‘learn from data’ in order to specify a conceptual framework that is appropriate for the particular space and time scale under consideration. Initially, the conceptual framework is developed by considering large space and time scales. The space and time scales are then progressively reduced and conceptual model complexity systematically increased until ultimately, an adequate simulation of daily streamflow and salinity is achieved. This strategy leads to identification of a few key physically meaningful parameters, most of which can be estimated a priori and with minimal or no calibration. Initially, the annual streamflow data from ten experimental catchments (control and cleared for agriculture) were analysed. The streamflow increased in two phases: (i) immediately after clearing due to reduced evapotranspiration, and (ii) through an increase in stream zone saturated area. The annual evapotranspiration losses from native vegetation and pasture, the ‘excess’ water (resulting from reduced transpiration after land use change), runoff and deep storage were estimated by a simple water balance model. The model parameters are obtained a priori without calibration. The annual model was then elaborated by analysing the monthly rainfall-runoff, groundwater and soil moisture data from four experimental catchments. Ernies (control, fully forested) and Lemon (53% cleared) catchments are located in zone with a mean annual rainfall of 725 mm. Salmon (control, fully forested) and Wights (100% cleared) are located in zone with mean annual rainfall of 1125 mm. Groundwater levels rose and the stream zone saturated area increased significantly after clearing. From analysis of this data it was evident that at a monthly time step the conceptual model framework needed to include a systematic gain/loss to storage component in order to adequately describe the observed lags between peak monthly rainfall and runoff.
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Cleland, Jonelle. "Western Australia's salinity investment framework : a study of priority setting in policy and practice." University of Western Australia. School of Agricultural and Resource Economics, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0120.
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In March 2002 the Western Australian Minister for Environment and Heritage adopted a policy framework to guide investment decisions on salinity management. Promoted as Western Australia's Salinity Investment Framework (or the SIF), it offered a set of principles for prioritising investment decisions that were generally grounded in economic theory. This represented a significant landmark in terms of the government's appreciation of the scale of salinity problem and its acknowledgement that a full turnaround in the situation was beyond the reach of both volunteers and the public purse. The evolution of the SIF policy, including an initial trial in the Avon Basin, provided an opportunity to evaluate pre-policy processes; observe policy on the run; and test stakeholder reactions to the investment principles embodied in the the SIF, as well as their reaction to its implied outcomes. The intention of the study was to highlight any barriers standing in the way of effectively implementing a policy to prioritise investments in salinity management and identify any novel approaches developed in an attempt to overcome them. The evaluation was multifaceted to incorporate retrospective and prospective modes of inquiry. The retrospective investigation involved the construction of a series of policy narratives using evidence from notes and minutes taken at SIF meetings, as well as other formal and informal documents. It systematically captured the influence of key people, events and decisions on the SIF up until June 2008. This evaluation highlighted the impact of (1) policy entrepreneurs; (2) time lags; (3) vertical silos, and (4) priority setting hierarchies. The prospective investigation involved the execution of a community survey featuring attitudinal questions, paired comparisons and a choice modelling experiment. The survey involved 269 personal interviews with rural landholders, townspeople and landcare officers across the Avon Catchment. It captured perceptions towards past funding strategies and proposals for future allocations and explored the nature of priority setting decisions in relation to trade-offs between: (1) the mix of assets protected; (2) the degree of risk; (3) the level of community involvement in the decision, and (4) the distribution of benefits. This evaluation highlighted the importance of (1) incentives and disincentives for change; (2) awareness of priority setting concepts; (3) the capacity of regional bodies; and (4) elements perceived to be crucial in priority setting.
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Horsnell, Tara Kathleen. "Quantifying thresholds for native vegetation to salinity and waterlogging for the design of direct conservation approaches." University of Western Australia. School of Environmental Systems Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0082.
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A field-based project was undertaken to develop and test a mechanism which would allow for the correlation of the health of vegetation surrounding playa lakes in south-west Australia with the natural variation in salinity and waterlogging that occurs spatially and temporally in natural systems. The study was designed to determine threshold ranges of vegetation communities using moderately extensive data over short temporal periods which will guide the design of potential engineering solutions that manipulate hydrological regimes to ultimately conserve and protect native vegetation. A pair of playa lake ecosystems, surrounded by primary production land, was modelled with hydro-geological data collected from March 2006 to March 2007. The data was used to determine the hydroperiods of vegetation communities fringing playa lakes and provide insight into the areas and species that are most affected by extreme rainfall events which are hypothesised to have a significant, rapid deleterious effect on the ecosystems. The methodology was multi-faceted and included; a detailed topographical survey; vegetation surveys; hydrological and hydro-geological monitoring over a 12 month period. 4 The hydro-geological data and vegetation data was linked with the topographical survey at a high resolution for spatial analysis in a Geographic Information System (GIS) to determine the degree of waterlogging experienced by vegetation communities over the monitoring period. The study has found that the spatial and temporal variability of hydroperiods has been reduced by rising groundwater levels, a result of extensive clearing of native vegetation. Consequently populations are becoming extinct locally resulting in a shift in community composition. Extreme summer rainfall events also have a significant impact on the health of vegetation communities by increasing the duration of waterlogging over an annual cycle and in some areas expanding the littoral zone. Vegetation is most degraded at lower positions in the landscape where communities are becoming less diverse and dominated by salt tolerant halophytic species as a result of altered hydrological regimes. Some species appear to be able to tolerate groundwater depths of less than 2.0 m from the surface, however there are thresholds related to the duration at which groundwater is maintained at this depth. Potential engineering solutions include groundwater pumping and diverting water through drains to maintain sustainable hydroperiods for vegetation in areas with conservation value. The effectiveness and efficiency of the engineering solutions can be maximised by quantifying thresholds for vegetation that include sustainable durations of waterlogging. The study has quantified tolerance ranges to salinity and waterlogging with data collected over 12 months but species may be experiencing a transition period where they have 5 sustained irreversible damage that will result in their eventual mortality. With long-term monitoring, the methodology developed and tested in the study can be used to quantify the long-term tolerance ranges that are important for the application of conservation approaches that include engineering solutions.
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Speldewinde, Peter Christiaan. "Ecosystem health : the relationship between dryland salinity and human health." University of Western Australia. School of Population Health, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0127.
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Australia is experiencing widespread ecosystem degradation, including dryland salinity, erosion and vegetation loss. Approximately 1 million hectares (5.5%) of the south-west agricultural zone of Western Australia is affected by dryland salinity and is predicted to rise to 5.4 million hectares by 2050. Such degradation is associated with many environmental outcomes that may impact on human health, including a decrease in primary productivity, an increase in the number of invasive species, a decrease in the number of large trees, overall decrease in biodiversity, and an increase in dust production. The resulting degradation affects not only farm production but also farm values. This study examines the effects of such severe and widespread environmental degradation on the physical and mental health of residents. Western Australia has an extensive medical record database which links individual health records for all hospital admissions, cancer cases, births and deaths. For the 15 diseases examined in this project, the study area of the south west of Western Australia (excluding the capital city of Perth) contained 1,570,985 morbidity records and 27,627 mortality records for the 15 diseases examined in a population of approximately 460,000. Environmental data were obtained from the Western Australian Department of Agriculture?s soil and landscape mapping database. A spatial Bayesian framework was used to examine associations between these disease and environmental variables. The Bayesian model detected the confounding variables of socio-economic status and proportion of the population identified as Aboriginal or Torres Strait Islander. With the inclusion of these confounders in the model, associations were found between environmental degradation (including dryland salinity) and several diseases with known environmentally-mediated triggers, including asthma, ischaemic heart disease, suicide and depression. However, once records of individuals who had been diagnosed with coexistent depression were removed from the analysis, the effect of dryland salinity was no longer statistically detectable for asthma, ischaemic heart disease or suicide, although the effects of socio-economic status and size of the Aboriginal population remained. The spatial component of this study showed an association between land degradation and human health. These results indicated that such processes are driving the degree of psychological ill-health in these populations, although it remains uncertain whether this 4 is secondary to overall coexisting rural poverty or some other environmental mechanism. To further investigate this complex issue an instrument designed to measure mental health problems in rural communities was developed. Components of the survey included possible triggers for mental health, including environmental factors. The interview was administered in a pilot study through a telephone survey of a small number of farmers in South-Western Australia. Using logistic regression a significant association between the mental health of male farmers and dryland salinity was detected. However, the sample size of the survey was too small to detect any statistically significant associations between dryland salinity and the mental health of women. The results of this study indicate that dryland salinity, as with other examples of ecosystem degradation, is associated with an increased burden of human disease.
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Callow, John Nikolaus. "River response to land clearing and landscape salinisation in southwestern Australia." University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0085.
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[Truncated abstract] Land clearing is known to increase runoff, and in many dryland landscapes is also associated with rising saline watertables, causing increased stream salinity and degrading riparian vegetation. The limited understanding of how river morphology responds to these changes and the potential for vegetation-based strategies to offer river management options under these conditions, has prompted this research. In southwestern Australia the severity of salinity and recent nature of land clearing provides an appropriate setting to investigate river response. A data-based, multidisciplinary methodology was applied to determine how land clearing and landscape salinisation has altered landscape sensitivity through changes in erosive potential, system connectivity and material threshold mechanisms, and how these affect patterns of river response. The study investigated the responses of morphologically similar reaches across fifty two study sites in the Kent River and Dalyup River catchments, in the south coastal rivers region of Western Australia. Land clearing was found to have significantly altered the hydrologic regime and erosive potential in both frequency and magnitude, with flow becoming more perennial, and increased annual discharge, flood peaks and bankfull flow frequency. While sediment transport rates have also increased since land clearing, they remain low on a global scale. Human response to a reduced rainfall regime and related water security pressures has caused large hillslope areas to be decoupled from the main channels by bank and farm dam construction, and have reduced downstream transmission of change. ... By contrast, steeper-sloped mid-catchment areas with minimal vegetation degradation caused by salinity are associated with higher erosive potential. A more erosive response is observed in these reaches where floodplains have been cleared for agricultural purposes. A conceptual model of vegetation growth across the salinity gradient observed in the study catchments was developed, and applied to selected river styles to assess the potential that vegetation-based strategies offer for river management. This work identifies the unsuitability of river restoration strategies, but the potential for river restoration or remediation in a saline landscape. Hydraulic modelling demonstrated that river rehabilitation strategies such as improving the vegetation condition of the riparian buffer using native or commercial species on areas elevated above saline flow can stabilise reaches. For river styles in wide and flat valleys, there is limited potential for vegetation-based river rehabilitation under the current salinity gradient. Field observation and modelling suggest that river remediation may offer geomorphic management options in salt-affected reaches through channelisation to lower watertables, and further research on this is warranted. This work found a consistent response for river styles across the two study catchments. Based on the understanding of river response and the potential for vegetation-based river management for each style, this research offers a regional-scale tool for river management in a saline landscape.
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Carver, Scott Stevenson. "Dryland salinity, mosquitoes, mammals and the ecology of Ross River virus." University of Western Australia. School of Animal Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0100.
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[Truncated abstract] In an era of emerging and resurging infectious diseases, understanding the ecological processes that influence pathogen activity and the influences of anthropogenic change to those are critical. Ross River virus (RRV, Togoviridae: Alphavirus) is a mosquito-borne zoonosis occurring in Australia with a significant human disease burden. In the southwest of Western Australia (WA) RRV is principally vectored by Aedes camptorhynchus Thomson (Diptera: Culicidae), which is halophilic. The inland southwest, the Wheatbelt region, of WA is substantially affected by an anthropogenic salinisation of agricultural land called dryland salinity, which threatens to influence transmission of this arbovirus. This study assessed the ecological impacts of dryland salinity on mosquitoes, mammalian hosts and their interactions to influence the potential for RRV transmission. Many aquatic insect taxa colonise ephemeral water bodies directly as adults or by oviposition. Using a manipulative experiment and sampling from ephemeral water bodies in the Wheatbelt, I demonstrated that salinity of water bodies can modify colonisation behaviour and the distribution of some organisms across the landscape. Halosensitive fauna selected less saline mesocosms for oviposition and colonisation. In particular, Culex australicus Dobrotworksy and Drummond and Anopheles annulipes Giles (Diptera: Culicidae), potential competitors with Ae. camptorhynchus, avoided ovipostion in saline mesocosms and water bodies in the field. This finding suggests salinity influences behaviour and may reduce interspecific interactions between these taxa and Ae. camptorhynchus at higher salinities. Using extensive field surveys of ephemeral water bodies in the Wheatbelt I found mosquitoes frequently colonised ephemeral water bodies, responded positively to rainfall, and populated smaller water bodies more densely than larger water bodies. The habitat characteristics of ephemeral water bodies changed in association with salinity. Consequently there were both direct and indirect associations between salinity and colonising mosquitoes. Ultimately the structure of mosquito assemblages changed with increasing salinity, favouring an increased regional distribution and abundance of Ae. camptorhynchus. The direct implication of this result is secondary salinisation has enhanced the vectorial potential for RRV transmission in the WA Wheatbelt. ... This thesis contributes to an emerging body of research aimed at delineating important ecological processes which determine transmission of infections disease. Collectively the findings in this study suggest dryland salinity enhances the potential for RRV activity in the Wheatbelt. Currently, human RRV notifications in the Wheatbelt do not reflect the salinity-RRV transmission potential in that area, but appear to be associated with dispersal of RRV from the enzootic coastal zone of southwest WA. I speculate dryland salinity is a determinant of potential for RRV transmission, but not activity. Dryland salinity is predicted to undergo a two to four fold expansion by 2050, which will increase the regional potential for RRV activity. Preservation and restoration of freshwater ecosystems may ameliorate the potential for transmission of RRV and, possibly, human disease incidence.
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my, marina@umt edu, and Marina Hassan. "Parasites of native and exotic freshwater fishes in the south-west of Western Australia." Murdoch University, 2008. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090720.141418.
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Fewer than 200 fish species are found in freshwater habitats in Australia, of which 144 are confined exclusively to freshwater. At least 22 species of exotic freshwater fish have been introduced into Australia, and 19 of these have established self-sustaining populations. However, the parasite fauna of both native and exotic freshwater fishes in Australia is poorly known. This is particularly the case in the south-west of Western Australia, where there have been no previous comprehensive studies of the parasites of 14 native species and nine or more exotic species of fish found in freshwater habitats.
This study represents a survey of the parasites of freshwater fishes in the South West Coast Drainage Division and reports 44 putative species of parasites in 1429 individual fishes of 18 different species (12 native and six exotic) from 29 locations. Parasites were found in 327 (22.88%) fishes, and of the infected fishes, 200 (61.16%) were infected with only one species of parasite and 127 (38.84%) were infected with two or more species of parasites. For helminth and arthropod parasites, which were more comprehensively surveyed than protozoan and myxozoans, I found 37 species compared to 77 species found in a recent study of fishes from the East Coast Drainage Division.
The present study demonstrated that parasitic infection was significantly more common in native fish species (mean prevalence of infection with any species of parasite = 0.36 ± 0.09) than in exotic fish species (0.01 ± 0.12). Parasites were found in all native fish species, but in only two exotic fish species that were examined. Parasite regional and component community diversity were estimated by species richness (the number of species, S) and by an index of taxonomic diversity (HT). Both parasite species richness and parasite taxonomic diversity were significantly greater in native fish species (mean S = 10.5 ± 2.3; mean HT = 1.19 ± 0.14) than in exotic fish species (mean S = 1.6 ± 3.3; mean HT = 0.27 ± 0.20). These relationships were consistent over all geographic locations that were sampled. The reduced parasite load of exotic species compared to native species has been previous reported across a wide range of taxa. It is thought to arise partly because founding populations of hosts have a low probability of harbouring the species total parasite fauna, and partly because parasites that infect introduced exotic species may not be able to maintain their life cycle in the new environment. It has been suggested that a reduced parasite load increases the competitive ability of exotic species compared to native species (the parasite release hypothesis) and this may partly explain the abundance and apparent competitive success of exotic over native species of freshwater fish in the South West Coast Drainage Division.
For native species of fish, there were major differences among species in both prevalence of parasitic infection and parasite community diversity, but this variation was not related to fish size, whether the fish were primarily freshwater or primarily estuarine, or whether they were primarily demersal or pelagic.
In this study, I report two new parasites in south western Australian waters. Both are copepod parasites; Lernaea cyprinacea and a new species of Dermoergasilus. The Dermoergasilus appears to be native to the south-west of Western Australia and has been described as Dermoergasilus westernensis. It differs from previously described species in the genus principally by the armature of the legs. This new species was found on the gills of freshwater cobbler, Tandanus bostocki and western minnow, Galaxias occidentalis in two different river systems.
Lernaea cyprinacea is an introduced parasitic copepod found on the skin and gills of freshwater fishes in many areas of the world. The parasite has not previously been reported in Western Australia. We found infestations of L. cyprinacea on four native fish species (G. occidentalis; Edelia vittata; Bostockia porosa; T. bostocki) and three introduced fish species (Carassius auratus; Gambusia holbrooki; Phalloceros caudimaculatus) at two localities in the Canning River, in the south-west of Western Australia. The parasite has the potential to have serious pathogenic effects on native fish species, although it appears to be currently localised to a small section of the Canning River.
Over all localities from which fishes were sampled in the present study, the proportion of native freshwater fishes with parasitic infections and the component community diversity of the parasite fauna of native fishes were both negatively related to habitat disturbance, in particular to a suite of factors (river regulation, loss of riparian vegetation, eutrophication and presence of exotic fish species) that indicate increased human usage of the river and surrounding environment. The reduced parasite load and diversity in native fishes from south-west rivers with greater human usage was due principally to the loss of a number of species of trematode, cestode and nematode endoparasites which use fishes as intermediate hosts. Other studies have also found that endoparasites with complex life cycles are most likely to be adversely affected by environmental changes, presumably because any environmental changes which impact on either free-living parasite stages or on any of the hosts in the complex train of parasite transmission will reduce parasite population size and may cause local extinction of the parasite species.
The most heavily infected species of native freshwater fish in the South West Coast Drainage Division was T. bostocki with 96% of all individuals containing at least one species of parasite. As with most freshwater fishes of south-west Australia, T. bostocki is limited in its distribution to waterways with relatively low salinity. The degree of parasitism and histopathology of internal and external organs in T. bostocki from the Blackwood River was examined over a period of rapid, seasonal changes in water salinity. As salinity increased, the infracommunity richness and prevalence of ectoparasites on the skin of fishes decreased, while the infracommunity richness and prevalence of endoparasites increased. This was associated with a decrease in histopathological lesion scores in the skin and an increase in histopathological lesion scores in internal organs, particularly the intestine. I hypothesise that the seasonal spike in salinity had two contrasting effects on parasitic infections of T. bostocki. Firstly, it increased the mortality rate of parasites directly exposed to water, leading to a decrease in ectoparasitic infection and associated pathology. Secondly, it suppressed immune function in fish, leading to a decreased mortality rate of parasites not directly exposed to water and a more severe pathological response to endoparasitism.
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Farrell, Claire. "Leaf-litter and microsite on seedling recruitment in an alley-planted E. sargentii and Atriplex spp. saline agricultural system." University of Western Australia. School of Plant Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0110.
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[Truncated abstract] In order to assess the sustainability of mixed plantings on saline land, this thesis examined the importance of leaf-litter trapping and microsites on recruitment in a salt affected alley-belted (tree/shrub) agricultural system in Western Australia. Located in the low rainfall region (MAR <330 mm) of the wheatbelt, the 60 ha site consists of concentric rows of Eucalyptus sargentii trees with mounded (6 - 11 cm high) 10 -15 m inter-rows of Atriplex spp. Sustainability of this system and fulfilment of productive and ameliorative functions is dependant on successful recruitment (perennials). Although the present study site was conducted on farmland in a Mediterranean-type climate, low annual rainfall and spatial arrangement of perennial shrubs and trees, allow useful comparisons to be made with naturally occurring banded semi-arid systems and vice-versa. Of key interest were leaf-litter redistribution and trapping by tree and shrub rows and whether litter-cover/microsites facilitated/interfered with seedling recruitment (establishment, growth and survival). Litter from the tree row, redistributed by prevailing winds and rain, accumulated adjacent to saltbush seeding mounds, creating a mosaic of bare and littered areas across the site (total litter 10 t/ha over 22 months). Accumulated litter was hypothesized to differentially influence seasonal soil abiotic parameters (depending on litter-cover density) including; salinity, water availability, infiltration rates, water repellency and temperature. These abiotic conditions were also hypothesized to vary between tree and shrub microsites. Biotically, recruitment at this site was also hypothesized to be determined by interactions (positive and negative) between perennial components and understorey annuals/perennial seedlings. Accumulation of litter and resultant heterogeneity was influenced by shrub morphology, microtopography, wind direction and distance from litter source, with increased litter on the leeward sides of hemispherical Atriplex undulata shrubs and shrubs closest to tree rows. ... The importance of tree/shrub microsites varied seasonally, with no influence in winter due to moderate temperatures and increased water availability. In warmer months saltbush mid-row microsites were most favourable for seedling recruitment due to moderate litter-cover; reducing salinity, temperatures and increasing infiltration; and reduced root-competition/shading by the tree row. Tree microsites also directly inhibited seedling recruitment through increased salinities and water repellency. However, trees also indirectly facilitated recruitment in adjacent areas through provision of leaf-litter. As litter-trapping and recruitment patterns at this site mirror those found in semi-arid natural and artificial systems, the results of this study provide useful insights into creating appropriate mimics of low rainfall natural banded woodland and chenopod shrublands. Saltbush seeding mounds, shrub morphology and litter were key components for litter trapping and recruitment heterogeneity at this site. In this tree/shrub alley planting, where litter quantities directly influence vegetation cover densities, future saline plantings need to consider appropriate tree/shrub row spacings and orientation for efficient resource (seeds, litter and water) capture.
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Jardine, Andrew. "The impact of dryland salinity on Ross River virus in south-western Australia : an ecosystem health perspective." University of Western Australia. School of Population Health, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0182.
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[Truncated abstract] A functional ecosystem is increasingly being recognised as a requirement for health and well being of resident human populations. Clearing of native vegetation for agriculture has left 1.047 million hectares of south-west Western Australia affected by a severe form of environmental degradation, dryland salinity, characterised by secondary soil salinisation and waterlogging. This area may expand by a further 1.7-3.4 million hectares if current trends continue. Ecosystems in saline affected regions display many of the classic characteristics of Ecosystem Distress Syndrome (EDS). One outcome of EDS that has not yet been investigated in relation to dryland salinity is adverse human health implications. This thesis focuses on one such potential adverse health outcome: increased incidence of Ross River virus (RRV), the most common mosquito-borne disease in Australia. Spatial analysis of RRV notifications did not reveal a significant association with dryland salinity. To overcome inherent limitations with notification data, serological RRV antibody prevalence was also investigated, and again no significant association with dryland salinity was detected. However, the spatial scale imposed limited the sensitivity of both studies. ... This thesis represents the first attempt to prospectively investigate the influence of secondary soil salinity on mosquito-borne disease by combining entomological, environmental and epidemiological data. The evidence collected indicates that RRV disease incidence is not currently a significant population health priority in areas affected by dryland salinity despite the dominant presence of Ae. camptorhynchus. Potential limiting factors include; local climatic impact on the seasonal mosquito population dynamics; vertebrate host distribution and feeding behaviour of Ae. camptorhynchus; and the scarce and uneven human population distribution across the region. However, the potential for increased disease risk in dryland salinity affected areas to become apparent in the future cannot be discounted, particularly in light of the increasing extent predicted to develop over coming decades before any benefits of amelioration strategies are observed. Finally, it is important to note that both dryland salinity and salinity induced by irrigation are important forms of environmental degradation in arid and semi-arid worldwide, with a total population of over 400 million people. Potential health risks will of course vary widely across different regions depending on a range of factors specific to the local region and the complex interactions between them. It is therefore not possible to make broad generalisations. The need is highlighted for similar research in other regions and it is contended that an ecosystem health framework provides the necessary basis for such investigations.
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Taukulis, Fiona E. "Diatom communities in lakes and streams of varying salinity from south-west Western Australia : distribution and predictability." Curtin University of Technology, Dept. of Environmental Biology, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17715.
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The distribution pattern of diatoms from lakes and streams of varying salinity in the south-west of Western Australia was investigated. A total of 95 water bodies were sampled and separated into freshwater (<3 ppt), hyposaline (3-20 ppt), mesosaline (20-50 ppt) and hypersaline (>50 ppt). The south-west and specifically the inland wheatbelt region has been severely influenced by secondary salinisation, due to clearing of native vegetation for agriculture. There has been little research on diatom communities from salt-affected systems, with this data providing the basis for the development of an inference model based on species optima and tolerance limits to salinity. Physico-chemical variables measured from the study sites were collated and assessed. Salinity ranged from freshwater (0.04) to hypersaline (156.80 ppt), and pH ranged from acidic (2.90) to alkaline (10.51). Dissolved oxygen levels were recorded from 1.11 to 18.67 mgL-1, water temperature from 6.30 to 28.10 °C and peripheral vegetation scores from 1 (little or no cover) to 5 (dense cover). Analysis of variance (ANOVA) showed that salinities were significantly higher in standing waters located further inland, compared to flowing waters in high rainfall areas. Hypersaline wetlands displayed significantly lower dissolved oxygen levels, higher water temperatures and reduced peripheral vegetation, compared to freshwaters. The pH of hypersaline sites was also significantly lower, associated with surrounding land use or underlying geology. The data collected provides important baseline information, with implications for aquatic biota.The community structure of diatoms in relation to varying salinity concentration was explored. An artificial substrate collector (JJ periphytometer) was used to standardise sampling and ensure diatom assemblages were representative of ambient water quality. A total of 217 taxa were identified with the highest diversity observed in freshwater sites (up to 33 species), and limited to less than 15 in hypersaline waters. According to BIOENV, salinity was the key factor influencing diatom community structure. SIMPER analysis found a number of discriminating taxa between salinity ranges, specifically between assemblages from freshwater and hypersaline sites. Taxa such as Achnanthidium minutissimum and Gomphonema parvulum were indicative of freshwaters. In comparison, Amphora coffeaeformis and Nitzschia ovalis were associated with hypersaline water bodies. Diatom community structure was also examined from 20 hypersaline wetlands in the wheatbelt region with varying pH. Characteristic taxa including Amphora coffeaeformis, Hantzschia sp. aff. baltica and Nitzschia ovalis showed a wide tolerance to salinity and pH, or hypersaline acidic conditions. BIOENV analysis found there were no observable differences between diatom assemblages in relation to salinities above 50 ppt and that pH was highly correlated to species composition. The increasing occurrence of acid saline lakes is of concern and is most likely attributable to deep drainage practices and continued use of fertilisers in agricultural areas.
A diatom-based transfer function was developed from the south-west dataset, to document species optima and tolerance limits to salinity. CCA analysis showed that salinity accounted for a significant and independent amount of variation in the diatom data enabling an inference model to be derived. The most successful model was generated using tolerance-downweighted weighted averaging, with a high coefficient of determination and low prediction errors that remained high after jackknifing. The optima of freshwater diatoms were similar to those reported from other regions of the world, although the optima of hypersaline species tended to be higher. Comparatively, the model performed very well, with the potential to be applied in future paleolimnological studies. In conclusion, this study has shown diatoms to be effective biomonitoring tools, providing the basis for future sampling strategies that assess the biodiversity of salt-affected water bodies in Western Australia. Potential indicator species from different salinity ranges were identified and the sensitivity of diatoms allowed for the development of a statistically robust inference model for the south-west. The reported optima and tolerance limits of important taxa may be further explored to evaluate the success of remediation measures implemented for secondary salinised systems in this region.
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McDonald, Kathi. "Variation in morphology, salinity and waterlogging tolerance and resource allocation in strawberry clover (Trifolium fragiferum L.) : implications for its use in mildly saline soils in southern Australian farming systems." University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0105.
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[Truncated abstract] In southern Australian farming systems the replacement of deep-rooted perennial native vegetation with shallow-rooted annual crops and pastures has resulted in rising groundwater tables and an increased incidence of dryland salinity. It has been suggested that to address this issue by restoring hydrological balance, large areas of agricultural land need to be vegetated with perennial plants. One of the most agriculturally productive ways to do this is to introduce perennial pastures, both into upslope groundwater
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Minkey, David Mark. "Weed seed predation by ants in the crop growing areas of Western Australia." University of Western Australia. Faculty of Natural and Agricultural Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0089.
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[Truncated abstract] In the crop growing areas of Western Australia, two economically important weed species, Lolium rigidum Gaud. (annual ryegrass) and Raphanus raphanistrum L. (wild radish), have evolved widespread herbicide resistance to multiple chemistry groups. Consequently, grain growers in the region have adopted an integrated approach to weed management that includes many non herbicide tools, however many more are needed as these weed species become increasingly more difficult to control. This thesis examines, in a series of field trials carried out in the Western Australian crop growing area, the potential for weed seed predation of annual ryegrass and wild radish by naturally occurring granivores as a new weed management tool for grain growers . . . The study discusses the implications of these results with the view to manipulating predation of weed seed through agricultural management practices. Ants were shown to be the dominant seed predator in this environment, especially in the centre of fields. The study has identified that the ant species Melophorus turneri (Forel), Monomorium rothsteini (Forel), Pheidole hartmeyeri (Forel) and Rhytidoponera metallica (Smith) are potential biological control agents for annual ryegrass seeds while P. hartmeyeri was identified as the only species suitable for biological control of wild radish seed pods. Ants were found to be sensitive to disturbance and some to crop residue type and these effects are discussed in relation to seed removal. This study of weed seed predation in agricultural fields is the most complete in this environment and can be used to inform further work in this area. It has identified that naturally occurring granivores can be used as a weed management tool.
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Campagna, Veronica. "Limnology and biota of Lake Yindarlgooda - an inland salt lake in Western Australia under stress." Curtin University of Technology, Department of Environmental Biology, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17473.
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Inland salt lakes of the arid and semi-arid zones of Western Australia are unique systems. An unpredictable rainfall pattern and a transient water regime ensure these lakes remain dry for much of the year. Lake Yindarlgooda in the Eastern Goldfields of Western Australia is a typical inland salt lake that has been subjected to additional stresses. This thesis is the outcome of investigations conducted on the lake from 2001 to 2003. Emphasis is on the limnology and biota of the lake, including an adjacent wetland, and impacts on the aquatic ecosystems caused predominantly by mining. Lake Yindarlgooda is a large, shallow hypersaline lake situated on the Yindarlgooda Palaeoriver. It is sodium chloride dominated and has naturally high background levels of nickel. Sites impacted by the leaching of hypersaline decant water from a leach residue storage facility (LRSF) were differentiated from control sites using multivariate statistics. Salinity was found to be a major determinant in the structure of the biological communities in the lake systems.Different biotic communities with low taxonomic diversity were recorded in Lake Yindarlgooda and Swan Refuge, a nearby hyposaline clay pan. The benthic microbial communities were dominated by halotolerant diatoms, notably Amphora coffeaeformis, Navicula incertata and Hantzschia baltica. Variation in the diatom assemblages between the playa sites and the clay pan were noted, influenced by habitat type and salinity. Within Lake Yindarlgooda, the diatom assemblages in the control and impact sites were found to be similar. A narrow salinity spectrum dictated the taxa present. Many of the benthic diatoms collected during the dry phase were encysted, having entered dormancy. The invertebrate fauna in Lake Yindarlgooda and Swan Refuge belonged to the Crustacea. A larger percentage of hyposaline invertebrate taxa were recorded from Swan Refuge, while those in Lake Yindarlgooda were typically halotolerant species. The Ostracoda showed the greatest diversity and their abundance was higher in the southern control sites while the Anostracan, Parartemia sp., dominated the northern impact sites of the playa.
The riparian zone of Lake Yindarlgooda supported a diverse plant community, dominated by the Chenopodiaceae. The marginal vegetation communities along the shores of Lake Yindarlgooda were found to be similar, indicating habitat homeogeneity. Within the riparian zone both biological and physical soil crusts occupied large areas not inhabited by vascular plants. The biological soil crust identified was composed of an association between the filamentous cyanobacterium Microcoleus sp. and a moss species (Musci). Both biological and physical soil crusts were found to have functional roles in stabilising the surrounding low dunes. The soil crusts in the northern control sites were badly degraded as a result of trampling by livestock, while those in the southern control sites were protected and were intact. Only one Parartemia species was found to inhabit Lake Yindarlgooda, Parartemia n. sp. d. It was collected in salinities ranging from 50 to 140 g L-1. The population appeared to be oviparous, recruitment mostly from resting eggs. The male to female ratios varied between sites, as did the number of juveniles compared to the adults. The northern impact sites had a more mature Parartemia population than the southern control sites and appeared to have undergone a second recruitment. Examination of the surface sediment found a well established Parartemia “egg bank” in the northern impact sites with egg numbers much higher than in the southern control sites.
The ultrastructure of the Parartemia resting egg was identical to that of Artemia. Differences in the external features and internal structure of the resting egg of Parartemia n sp. d and Parartemia n. sp g from Lake Miranda, another saline lake, were identified. This study showed morphological variation of the egg within Parartemia, a finding not previously recorded. Rehydration trials on the Parartemia egg bank indicated that the increase in sediment salinity from the LRSF had a negative effect on the hatching of the resting eggs. In salinities above 60 mS cm-1 hatching was less successful. The conditions provided in the trials were similar to those in Lake Yindarlgooda. The hatching technique was repeated on sediment from Lake Miranda with similar results. These trials were considered a valuable monitoring tool in the assessment of impacts on the biota of temporary lakes in the absence of water. This study demonstrated that in the absence of water the egg and spore/seed bank can be used as a proxy for monitoring temporary lakes. It was also found to be valuable in understanding the distribution and diversity of the biotic communities in Lake Yindarlgooda. This study provides the first integrated reference information on a Western Australian inland salt lake against which any future impact may be assessed.
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Dunne, Christopher Philip. "Control of Sudden Death in Cultivated Proteas from the Southwest of Western Australia." Murdoch University, 2004. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20041207.140807.
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Phytophthora cinnamomi Rands is a common and devastating pathogen of cultivated proteas worldwide. Webb (1997) described a Sudden Death plant disease of proteas in Western Australia (WA) protea plantations. Proteas that suffer the syndrome display symptoms such as stunted growth, wilting, chlorosis and often death. In the current study, a number of protea plantations in the southwest of WA were visited to quantify the extent that P. cinnamomi was attributing to deaths of cultivated proteas. The survey indicated that P. cinnamomi is the major cause of Sudden Death in proteas. A range of other fungi (Fusarium, Botryosphaeria, Pestalotiopsis, Alternaria) and pests (nematodes, mealy bug, scale insects) were also identified to be contributing to protea death and decline in WA plantations. In many cases the factors contributing to protea disease appeared complex, with a range of physical factors or nutritional imbalances commonly associated with these pathogens and pests. As P. cinnamomi was the major cause of death of cultivated proteas the remainder of the experiments described in this dissertation investigated its control in horticultural plantings.
Biofumigation has the potential to become an important technique in an overall integrated management approach to P. cinnamomi. In this thesis, biofumigation refers to the suppression of pathogens and pests by the incorporation of Brassica plants into the soil. Two biofumigants (Brassica juncea (L.) Czern., B. napus L.) were screened for their effect on the in vitro growth of five common Phytophthora species (P. cinnamomi, P. cactorum (Lebert & Colin) Schroeter., P. citricola Sawada, P. cryptogea Pethyb. & Laff. and P. megasperma Drechsler). Growth was determined by the measuring dry weight and radial growth of vegetative hyphae. B. juncea was found to be superior in its suppressive effect compared to B. napus. There was also significant variation in the sensitivity of the Phytophthora species to the suppressive effects of the biofumigants. P. cinnamomi was the most sensitive of the five species investigated. Where the rates of the biofumigant were sufficient to suppress growth of Phytophthora, the suppressive effect was mostly fungicidal.
To determine how B. juncea and B. napus affect the infective ability and survival of P. cinnamomi, their effects on sporangia and chlamydospores production in soil was investigated in vitro. P. cinnamomi colonised Miracloth discs were added to soil amended with the two Brassica species, before being removed every two days over an eight day period for the determination of sporangia production, chlamydospore production and infective ability. Only the soils amended with B. juncea significantly reduced sporangia production in P. cinnamomi. Both Brassica species increased the percentage of aborted or immature sporangia and reduced the infective ability of the pathogen. Neither Brassica species had any effect on zoospore release or chlamydospore production in P. cinnamomi.
Soil cores and soil leachate were collected from biofumigant-amended field soils to determine the inoculum potential and infective ability of the pathogen under glasshouse conditions. Amending the soil with both Brassica species had an immediate suppressive effect on the inoculum potential and infective ability of the P. cinnamomi. However, after this initial suppression there was a gradual increase in the recovery of the pathogen over the monitoring period of four weeks. To determine if the suppression would result in decreased disease incidence in a susceptible host, Lupinus angustifolius L. seeds were planted in the biofumigant amended soil. B. juncea amended soils reduced the disease incidence of P. cinnamomi by 25%. B. napus had no effect on disease incidence in L. angustifolius.
Although the current study had demonstrated that biofumigants could suppress the growth, sporulation and infection of P. cinnamomi, it was unclear if this would equate to a reduction in disease incidence when applied in the field. A field trial was conducted on a protea plantation in the southwest of Western Australia that compared biofumigation with B. juncea to chemical fumigation (metham sodium) and soil solarisation. The three soil treatments were used in an integrated management approach to control P. cinnamomi that included the use of a hardwood compost, mulch and water sterilisation. All treatments were monitored during their application to ensure the treatments were conducted successfully. The three soil treatments significantly reduced the recovery of the pathogen and the infective ability of the pathogen to a soil depth of 20 cm. Metham sodium was the most suppressive soil treatment and soil solarisation was the least suppressive treatment. Only the metham sodium treatment resulted in a significant reduction in the incidence of root rot in Leucadendron salignum P.J. Bergius x laureolum (Lam.) Fourc (c.v. Safari Sunset) over the monitoring period of three years.
Another field trial was conducted on the same protea plantation to compare the effectiveness of B. juncea and B. napus, without the use of other control strategies, to reduce the incidence of P. cinnamomi infection of Leucadendron Safari Sunset. The concentration of isothiocyanates was monitored for seven days after the incorporation of the biofumigants. Although both Brassica species reduced the recovery and infective ability of the pathogen, neither biofumigant reduced the incidence of root rot in Leucadendron Safari Sunset.
In conclusion, P. cinnamomi is the most common and devastating pathogen in WA protea plantations. The current study demonstrated that P. cinnamomi is sensitive to the suppressive nature of biofumigants. Biofumigants can suppress the in vitro growth, sporulation, infective ability of P. cinnamomi and reduce the incidence of the disease caused by the pathogen in the glasshouse. Of the two Brassica species investigated, B. juncea was superior in its ability to control P. cinnamomi compared to B. napus. When applied in the field, biofumigation using B. juncea was found to be more suppressive that soil solarisation, but not as effective as metham sodium.
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Dunne, Christopher P. "Control of sudden death in cultivated proteas from the Southwest of Western Australia /." Access via Murdoch University Digital Theses Project, 2004. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20041207.140807.
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Bell, Lindsay William. "Prospects of Dorycnium species to increase water use in agricultural systems of southern Australia /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2006.0033.
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Thomas, Claudia. "The epidemiology and control of Clostridium difficile infection in a Western Australian hospital." University of Western Australia. School of Population Health, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0011.
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[Truncated abstract] The prinicipal aim of this thesis was to explore the relationship between 3rd generation cephalosporin antibiotics and hospital-acquired Clostridium difficile-associated diarrhoea (CDAD). This antibiotic class has been implicated in the aetiology of CDAD; therefore restriction of these antibiotics via antibiotic policies represents a potential strategy for prevention and control of CDAD. Successful control of CDAD in hospitals translates to improved quality of care for patients, and a reduction of pressure on hospital resources. Therefore, the objectives of this study were to determine whether 3rd generation cephalosporins were related to CDAD, to evaluate the effect of changes to antibiotic policy on the incidence of CDAD, and to determine the impact of CDAD on patient length of stay and hospital costs. The study was conducted in Sir Charles Gairdner Hospital (SCGH), a public teaching hospital located in Perth, the capital city of the state of Western Australia. Evidence for an association between 3rd generation cephalosporins and CDAD was obtained from studies of ecologic- and individual-level data. A time series analysis of the relationship between monthly consumption of 3rd generation cephalosporins and the incidence of CDAD in SCGH was undertaken covering the period 1994 to 2000. The results demonstrated a positive relationship between the use of 3rd generation cephalosporins and CDAD. A matched case-control study that involved 193 adult inpatients diagnosed with CDAD and 386 adult inpatients without CDAD, selected from the period 1996 to 2000, was conducted. Information was collected on exposure to 3rd generation cephalosporin antibiotics during hospitalisation, as well as exposure to other antibiotics and medications, procedures, and comorbidities. Results from conditional logistic regression analyses found CDAD cases were six times more likely to be exposed to 3rd generation cephalosporins during their admission, prior to the onset of diarrhoea, than controls (adjusted odds ratio [OR] = 6.17, 95% confidence interval [CI] = 1.56-24.37). Approximately one third of CDAD in the study population could be attributed to 3rd generation cephalosporins. CDAD cases were also four times more likely to have been exposed to either amoxicillin-clavulanate or ticarcillin-clavulanate (adjusted OR=4.23, 95% CI=1.81-9.93). In October 1998, an antibiotic policy was introduced at SCGH that restricted the use of ceftriaxone, the 3rd generation cephalosporin most commonly used by the hospital. During 1999 and 2000, the incidence of CDAD halved as ceftriaxone consumption fell in response to this policy. The effect of this policy was demonstrated in the time series model; during the post-policy period the relationship between ceftriaxone and CDAD that was evident prior to the policy was cancelled out. From the individual-level data, obtained from the case-control study, a reduction in the prevalence of exposure to 3rd generation cephalosporins from 11% to 1% accounted for a 30% reduction in the incidence of CDAD. Data from the case-control study was also used to analyse the independent contribution of CDAD to length of stay and admission costs using multiple linear regression
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Borger, Catherine. "The biology and ecology of Salsola australis R.Br. (Chenopodiaceae) in southwest Australian cropping systems." University of Western Australia. School of Plant Biology, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0062.
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Salsola australis is an introduced weed of crop and pasture systems in the Western Australian broad acre cropping and pasture region (wheat-belt). This thesis investigated the classification, biology and ecology of the genus Salsola in southwest Australia, as well as modelling the effectiveness of possible weed control practices. Prior to this research, S. tragus was the only recognised species of the Salsola genus within Australia. However, genetic analysis revealed that four genetically distinct putative taxa of the genus Salsola were found in southwest Australia, none of which were S. tragus. The taxa that is the most prevalent agricultural weed was classified as S. australis, but the other three putative taxa could not be matched to recognised species. All four taxa were diploid (2n = 18), as opposed to tetraploid (2n = 36) S. tragus. Within the agricultural system of southwest Australia, S. australis plants established throughout the year, although the majority of seed production occurred in late summer and autumn. Total seed production (138-7734 seeds per plant) and seed viability (7.6-62.8%) of S. australis were lower than that reported for other agricultural weed species of the Salsola genus. Seed dispersal occurred when the senesced plants broke free of their root system to become mobile. Wind driven plants travelled and shed seed over distances of 1.6 to 1247.2 m. Movement of approximately half the plants was restricted to less than 100 m by entanglement with other S. australis plants within the stand. Some seed was retained on the senesced plants, but the germinability of this seed fell to less than 2% in the two month period following plant senescence (i.e. a decline of 79%). Once seed shed into the soil seed bank, anywhere from 32.3 to 80.7% of the viable seeds germinated in the year following seed production, with the rest remaining dormant or degrading. A model of the life cycle of S. australis based on the population ecology data indicated that the dormant seed bank had very little effect on annual seedling recruitment, but seed dispersal from neighbouring populations had a large impact on population growth rate. Therefore, the most successful weed control measures were those that restricted seed dispersal from neighbouring populations, or those that were applied to all populations in the region rather than to a single population. Weed control techniques applied to a single population, without reducing seed dispersal, could not reduce population size.
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Wildy, Daniel Thomas. "Growing mallee eucalypts as short-rotation tree crops in the semi-arid wheatbelt of Western Australia." University of Western Australia. School of Plant Biology, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0031.
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[Truncated abstract] Insufficient water use by annual crop and pasture species leading to costly rises in saline watertables has prompted research into potentially profitable deep-rooted perennial species in the Western Australian wheatbelt. Native mallee eucalypts are currently being developed as a short-rotation coppice crop for production of leaf oils, activated carbon and bio-electricity for low rainfall areas (300—450 mm) too dry for many of the traditional timber and forage species. The research in this study was aimed at developing a knowledge base necessary to grow and manage coppiced mallee eucalypts for both high productivity and salinity control. This firstly necessitated identification of suitable species, climatic and site requirements favourable to rapid growth, and understanding of factors likely to affect yield of the desirable leaf oil constituent, 1,8-cineole. This was undertaken using nine mallee taxa at twelve sites with two harvest regimes. E. kochii subsp. plenissima emerged as showing promise in the central and northern wheatbelt, particularly at a deep acid sand site (Gn 2.61; Northcote, 1979), so further studies focussed on physiology of its resprouting, water use and water-use efficiency at a similar site near Kalannie. Young E. kochii trees were well equipped with large numbers of meristematic foci and adequate root starch reserves to endure repeated shoot removal. The cutting season and interval between cuts were then demonstrated to have a strong influence on productivity, since first-year coppice growth was slow and root systems appeared to cease in secondary growth during the first 1.5—2.5 years after cutting. After decapitation, trees altered their physiology to promote rapid replacement of shoots. Compared to uncut trees, leaves of coppices were formed with a low carbon content per unit area, and showed high stomatal conductance accompanied by high leaf photosynthetic rates. Whole-plant water use efficiency of coppiced trees was unusually high due to their fast relative growth rates associated with preferential investments of photosynthates into regenerating canopies rather than roots. Despite relatively small leaf areas on coppice shoots over the two years following decapitation, high leaf transpiration rates resulted in coppices using water at rates far in excess of that falling as rain on the tree belt area. Water budgets showed that 20 % of the study paddock would have been needed as 0—2 year coppices in 5 m wide twin-row belts in order to maintain hydrological balance over the study period. Maximum water use occurred where uncut trees were accessing a fresh perched aquifer, but where this was not present water budgets still showed transpiration of uncut trees occurring at rates equivalent to 3—4 times rainfall incident on the tree belt canopy. In this scenario, only 10 % of the paddock surface would have been required under 5 m wide tree belts to restore hydrological balance, but competition losses in adjacent pasture would have been greater
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Sounness, Marcus Neil. "Alternative grazing systems and pasture types for the South West of Western Australia : a bio-economic analysis." University of Western Australia. School of Agricultural and Resource Economics, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0054.
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Alternative grazing systems and pasture types for wool production in the south west of Western Australia were analysed using bio-economic modelling techniques in order to determine their relative productivity and profitability. After reviewing the experimental and modelling literature on perennial pastures and grazing systems, seven case studies of farmers were conducted in order to investigate the practical application of innovative grazing systems and use of perennial pastures. Together these case studies provided information for identifying relevant variables and for calibrating the modelling work which followed. The core of the work lies in a bio-economic model for investigating the comparative value of the three grazing systems and two pasture families mentioned above. A baseline scenario using currently available and reliable scientific data provides baseline results, after which a number of sensitivity analyses provide further insights using variations of four key parameters: persistence, heterogeneity, water soluble carbohydrates, and increased losses. Results show that perennial pastures are in the studied region more profitable than annual pastures. Under current baseline conditions, continuous grazing with perennial pastures is the most profitable enterprise, but this superiority is not robust under parameter variations defined by other scenarios. The more robust solution in terms of enterprise profitability is cell grazing with perennial pastures. The results indicate that intensive grazing systems such as cell grazing have the potential to substantially increase the profitability of grazing operations on perennial pasture. This result is an encouraging one in light of its implications for water uptake and salinity control. It means that economics and land care can go hand in hand, rather than be competitive. It is to be noted that it is the choice of the grazing system in combination with the pasture species, rather then the pasture species itself, that allows for such complementarity between economics and sustainable land use. This research shows that if farmers adopt practices such as cell grazing they may be able to increase the area that they can profitably plant to perennial pasture thus reducing the impacts of dryland salinity. This finding is consistent with the findings of the case studies where the farmers perceived that, provided grazing was planned, increasing the intensity of their grazing management and the perenniallity of their pastures would result in an increase in the profitability of their grazing operation. As a result this research helps to bridge a gap which has existed in this area of research, between the results of scientific research and those reported in practice.
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McGowan, Wayne S. "Thinking about the responsible parent : freedom and educating the child in Western Australia." University of Western Australia. Graduate School of Education, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0014.
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This study is concerned with how educational legislation shapes and uses freedom for the purpose of governing the parent. The key question guiding the study was: How does the Act constitute the ‘parent’ as a subject position responsible for schooling the child? Central to the work is an examination of the School Education Act 1999 (the Act) using Foucault’s thinking on governmentality. This is prefaced by historical accounts that bring together freedom and childhood as contrived styles of conduct that provide the governmental logic behind the Act. The study reveals how the Act shapes and uses the truth of freedom/childhood to construct the responsible parent as a style of conduct pegged to a neo-liberal political rationality of government. It is this political rationality that provides the node or point of encounter between the technologies of power and the self within the Act which forms the ‘responsible’ identity of the parent as an active self-governing entrepreneur made more visible by the political construction of ‘others.’ This is a legal-political subjectivity centred on the truth of freedom/childhood and a neo-liberal rationality of government that believes that any change to our current ethical way of being in relation to educating the child would ruin the very freedoms upon which our civilised lifestyle depends. In essence, the Act relies on the production of ‘others’ as the poor, Aboriginal and radical who must be regulated and made autonomous to constitute the ‘parent’ as an active consumer whose autonomous educational choices are an expression of responsibility in relation to schooling the child
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Michael, Pippa J. "Agro-ecology of Malva parviflora (small-flowered mallow) in the Mediterranean-climatic agricultural region of Western Australia." University of Western Australia. Faculty of Natural and Agricultural Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0076.
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[Truncated abstract] Malva parviflora L. (small-flowered mallow) (Malvaceae) is a common weed of pastures and wastelands and its distribution has increased rapidly throughout Australia during the last decade. Control of M. parviflora with herbicides, such as glyphosate, is often unsatisfactory and changing farming practices, such as minimum tillage, have facilitated its spread. Yet there has been little research on M. parviflora in the past and many aspects of its biology and ecology are unknown. Hence, there exists a need to examine these aspects in order to investigate and develop suitable integrated weed management strategies. Weed identification is the first and probably the most important step in the management of weeds. Here it is shown that the weedy Malva species in Western Australian farming systems is M. parviflora, and not a morphologically similar Malva species or hybrid of two species. A common garden study of 24 populations collected across the agricultural region of south-west Western Australia revealed that since its introduction over 140 years ago M. parviflora has successfully adapted to a wide range of distinct environments. The species is able to thrive in areas that vary in annual rainfall from 315 to 496 mm, maximum average temperatures from 21.9 to 26.8oC and minimum average temperatures from 9 to 13.6oC. However, there was limited broad scale ecoclinal differentiation and low genetic variation within the common garden study with only length of time between sowing and flowering differing between populations. As the species was shown to possess a predominately inbreeding system, which typically would create ecotypes/ecoclines due to limited gene flow, it was suggested that seed dispersal by sheep is likely to have increased gene flow thus suppressing population differentiation. A considerable proportion of mature hardseeded M. parviflora can survive rumen digestion and mastication by sheep. ... With origins thought to be in the Mediterranean region, it is not surprising that M. parviflora has thrived and prospered in south-west Western Australia. This thesis has determined several aspects that have enabled it to flourish in this Mediterranean-type environment and most of these attributes, including autogamous reproduction, ecoclinal/ecotypic formation, dormancy and asynchronous germination and rapid seed development, are commonly found in successful weeds world-wide.
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Jenkins, Sommer. "Ecophysiological principles governing the zonation of puccinellia (Puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) on saline waterlogged land in south-western Australia." University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0133.
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Puccinellia (puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) often show ecological zonation in saline landscapes, with puccinellia occurring in less elevated more saline/waterlogged locations, and tall wheatgrass occurring in more elevated less saline/waterlogged locations. The aims of this study were to: (a) characterize the observed ecological zonation at a field site, (b) quantify the effects of variables likely to explain growth differences of the two plants in glasshouse experiments, and (c) identify and compare anatomical and physiological mechanisms that explain these zonation patterns. At an experiment in the field near Kojonup (0522824E, 6244579N), puccinellia was found to colonise the lower more severely salinised and waterlogged zones of the landscape, with tall wheatgrass occupying the higher less affected zones. These differences in zonation were clearly associated with variance in soil salinity and water-table depth. Glasshouse experiments in soil revealed that low pH values, low calcium concentrations and variation in salinity alone did not explain the ecological zonation observed in the field. However, there was a substantial difference in the responses of the two plant species to waterlogging in combination with salinity. Puccinellia grew better under saline waterlogged conditions than tall wheatgrass, which was associated with better regulation of Na+ and K+ under saline/waterlogged conditions than in tall wheatgrass. Under non-saline conditions, waterlogging (hypoxia) decreased shoot weights in puccinellia by 15% and in tall wheatgrass by 20%. Similar growth results were obtained in nutrient solution culture, where waterlogging was simulated by lowering the oxygen in solutions through bubbling with N2 gas. Under saline hypoxic conditions, puccinellia, compared to tall wheatgrass, showed increased growth and maintenance of selectivity of K+ over Na+ across adventitious roots. Solution experiments revealed adaptive traits responsible for conveying better growth and ion maintenance present in puccinellia, but not tall wheatgrass, such as inducement of a barrier to radial oxygen loss in the basal regions of adventitious roots (not previously reported in the literature for puccinellia), formation of root aerenchyma and packing of cortical cells and suberin deposition in hypodermal and endodermal root cell layers. These results should assist in targeting pasture species, and predicting their growth response, in saline and waterlogged landscapes. Further work on examining the genetic material of puccinellia is warranted in order to identify genes that could be transferred into crop plants to convey salt and waterlogging tolerance.
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Kangas, M. I. "Postlarval and juvenile western king prawn Penaeus latisulcatus Kishinovye studies in Gulf St Vincent, South Australia, with reference to the commerical fishery /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phk159.pdf.
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Friesen, Lincoln Jacob Shane. "Identification of the mechanisms of wild radish herbicide resistance to PSII inhibitors, auxinics, and AHAS inhibitors." University of Western Australia. School of Plant Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0106.
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The objective of this Ph.D. research was to identify new and novel mechanisms of wild radish (Raphanus raphanistrum L.) resistance to photosystem II (PSII) inhibitors, auxinics, and acetohydroxyacid synthase (AHAS) inhibitors. PSIIinhibitor resistance was demonstrated to be target-site based, and conferred by a Ser264 to Gly substitution of the D1 protein. Auxinic resistance was associated with reduced herbicide translocation to the meristematic regions of resistant wild radish plants. Two new resistance mutations of wild radish AHAS were discovered, including one encoding the globally rare Asp376 to Glu substitution, and another encoding an Ala122 to Tyr substitution, which has never been identified or assessed for resistance in plants previously. Characterization of the frequency and distribution of AHAS resistance mutations in wild radish from the WA wheatbelt revealed that Glu376 was widespread, and that some mutations of AHAS are more common than others. Computer simulation was used to examine the molecular basis of resistance-endowing AHAS target-site mutations. Furthermore, through the computer-aided analysis, residues were identified with the potential to confer resistance upon substitution, but which have not previously been assessed for this possibility. Results from this Ph.D. research demonstrate that diverse, unrelated mechanisms of resistance to PSII inhibitors, auxinics, and AHAS inhibitors have evolved in wild radish of the WA wheatbelt, and that these mechanisms have accumulated in some populations.
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Son, Kyongho. "Improving model structure and reducing parameter uncertainty in conceptual water balance models with the use of auxiliary data." University of Western Australia. School of Environmental Systems Engineering, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0094.
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[Truncated abstract] The use of uncertainty analysis is gaining considerable attention in catchment hydrological modeling. In particular, the choice of an appropriate model structure, the identifiability of parameter values, and the reduction of model predictive uncertainty are deemed as essential elements of hydrological modelling. The chosen model structure must be parsimonious, and the parameters used must either be derivable from field measured data or inferred unambiguously from analysis of catchment response data. In this thesis, a long-term water balance model for the Susannah Brook catchment in Western Australia has been pursued using the ?downward approach?, which is a systematic approach to determine the model with the minimum level of complexity, with parameter values that in theory are derivable from existing physiographic data relating to the catchment. Through the analysis of the rainfall-runoff response at different timescales, and the exploration of the climate, soil and vegetation controls on the water balance response, an initial model structure was formulated, and a priori model parameter values estimated. Further investigation with the use of auxiliary data such as deuterium concentration in the stream and groundwater level data exposed inadequacies in the model structure. Two more model structures were then proposed and investigated through formulating alternative hypotheses regarding the underlying causes of observed variability, including those associated with the absence of a contribution of deep groundwater flow to the streamflow, which was indicated by deuterium concentration and internal dynamics characterized by the observed groundwater levels. ... These differences are due to differences in the time delay between rainfall and recharge between upland and riparian regions. The ages of water recharging the groundwater and discharging from the catchment were estimated by assuming a piston flow mechanism. In the deeper, upland soils, the age of recharging water was considerably larger than the unsaturated zone delay would suggest; a recharge response 16 days after an infiltration event may involve water as much as 160 days old. On the other hand, the delay and the age of recharging water were much lower in the shallow riparian zone. Where the upland zone contributes significantly to discharge, the predicted difference between the rainfall-discharge response time and the average age of discharging water can be significant.
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Taylor, Peter John 1957. "Potential impacts of interception belts on the management of dryland salinity." 1999. http://web4.library.adelaide.edu.au/theses/09AGRP/09agrpt245.pdf.
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Bibliography: p. 161-185. The main aim of this project was to establish whether or not interception belts can be expected to transpire sufficient volumes of water to be considered a feasible option for controlling rising groundwater. (conclusion)
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Humphries, Alan Wayne. "New challenges for lucerne in southern Australian farming systems : identifying and breeding diverse lucerne germplasm to match these requirements." 2008. http://hdl.handle.net/2440/50451.
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Lucerne is a deep-rooted perennial pasture that is promoted to land managers in southern Australia to mitigate the effects of dryland salinity, a problem of national significance caused by the replacement of native trees and shrubs with annual crops and pastures. In recent years, the acceptance of climate change has provided further rationale for increasing the use of perennial legumes in our farming systems. Perennial legumes have a role in offsetting C02 emissions by sequestering C and N in soil, and provide new, resilient options for future farming in a warmer and more variable climate. This research has focused on evaluating the diverse range of germplasm found in lucerne (Medicago sativa spp.) for a range of attributes in order to determine its compatibility with existing and future farming systems in southern Australia. Regional field evaluation at 8 sites in southern Australia showed that lucerne is a broadly adapted and robust plant. After 3 years, plant density ranged from 2-55 plants / m2 with differences in persistence attributed to tolerance to a combination of stresses including soil acidity, saline and sodic subsoils, drought conditions and persistent heavy grazing. Highly winter-active lucerne (class 9-10) was confirmed to be the most suitable group for short phase rotations in southern Australia, providing grazing is well managed. This germplasm was less persistent than other winter activity groups, but produces more total herbage yield in environments with winter dominant rainfall patterns. Highly winter-active lucerne has poor persistence under continuous grazing, but this may aid in its removal when used in rotation with crops. Winteractive germplasm (class 6-8) was more grazing tolerant and persistent, making it the most suitable group for longer phase rotations (>4 years), or where more flexible grazing management practices are required (i.e. 35 days grazing followed by 35 days recovery). Individual grazing tolerant plants from this group were selected and randomly inter-mated to form new breeder’s lines in the development of a grazing tolerant cultivar. For the first time, the high water-use of a farming system involving wheat overcropped into lucerne is presented. Lucerne over-cropped with wheat used an additional 43-88 mm of water in comparison to continuous wheat at Roseworthy and Katanning respectively. Over-cropping reduced wheat yield by 13-63%, but it can be more efficient in terms of land area to grow lucerne and wheat as a mixture than on separate parcels of land. Very winter-dormant lucerne (class 1-2) appears to be less competitive with winter cereal crops during wheat establishment. It may also be possible to reduce lucerne’s competition with wheat at the critical stage of anthesis, with low spring yielding lucerne varieties identified in this research (SA37908). This group of plants provides excellent potential for the development of high water-use farming systems because they are grazing tolerant and persistent, and have summer forage production and sub-soil water extraction rates that are equivalent to winter active lucerne. The research has been used to identify the perfect ideotype for lucerne in phase farming and over-cropping systems, which can be used to set targets in future breeding programs. The research also highlights current opportunities for the integration of lucerne into southern Australian farming systems to help curb the spread of dryland salinity and reduce the impact of climate change.http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1344608
Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008
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Kirkby, S. D. (Stephen Denis). "Managing dryland salinisation with an integrated expert system/geographic information system / S.D. Kirkby." 1994. http://hdl.handle.net/2440/21517.
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Bibliography: leaves 119-218.xiv, 218 leaves : ill. (some col.), maps (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Salt Manager represents the software system developed by this thesis to implement an interactive land classification methodology. An Expert System (ES), a Geographic Information System (GIS), remotely sensed information and a relational database management system (RDBMS) have been utilised to construct the methodology.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geography, 1995