Dissertations / Theses on the topic 'Salinization – Control – Western Australia'

[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.

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.

[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

[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.

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.

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.

[Truncated abstract] The Collie River drainage basin is an important water resource catchment in southwestern Australia. Salinisation of a major water supply within the catchment, the Wellington Reservoir, has arisen due to changes in the water and salt balance in response to land clearing over saprolite aquifers. Paired catchment studies, the Collie Experimental Catchments (CECs), established in the early 1970’s in high and low rainfall areas increased our understanding of water and salt (predominantly chloride) movement in these aquifers through the collection and analysis of high resolution spatio-temporal data. However, the conceptual models developed from this work take little account of landscape heterogeneity, and this has caused problems in subsequent modelling studies, where success in calibrating stream flow has been countered by difficulties in predicting salt loads. The challenge remains to better describe variability in the Collie landscape and understand the influence of climate, vegetation, geology and geomorphology on observed water and salt fluxes. The release of salt from the lower saprolite aquifer and the role of the surficial aquifer in buffering groundwater discharge were investigated. The acquisition, analysis and interpretation of new regolith and geophysical data in 2001-2003 from the CECs, together with data from a high resolution digital elevation model, and existing drilling information, were used to construct a geologicalgeomorphological compartment framework, to observe changes in aquifer behaviour ... Significant differences in the salt flux from compartments have been noted at a range of scales, with implications for both water resource and land management. The approach developed to identify compartments and assess their efficiency could be simplified, using catchment critical parameters determined from geological and geomorphological characteristics. As a consequence, the implementation of a compartment framework in catchments with saprolite aquifers should allow for more informed decisions to be made in the selection of sites for revegetation strategies or the development of engineering works. This is particularly important in the Collie Catchment where reclamation scenarios are currently being discussed. Consideration of the catchment as a compartmentalised system would help manage salt loads in the Collie River and return the Wellington Reservoir to a functional water resource.

[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.

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.

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.

[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

[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.

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.

[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.

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

[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.

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.

[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.

Dryland salinity is a major and expanding threat to agricultural land in Australia. Animal production from forages grown on saline land is perhaps its most promising economic use. Glycophytic forage legumes have been evaluated under saline conditions mainly for agronomic characteristics and, to a lesser extent, for nutritive quality to animals. Plant growth and its nutritive quality are interrelated, but a decline in yield in response to salinity may be associated with effects on the chemical constituents of the plant since soil salinity affects plant metabolism. This research aimed to investigate changes in the components of yield and nutritive value of two legumes species. Lucerne ( Medicago sativa ) and Melilotus ( Melilotus albus ) were exposed to different levels of NaCl in the range of 0 to 110 mM NaCl. The research tested the hypothesis that the components of plant nutritive value are not as sensitive to salinity as shoot biomass production since the adaptive mechanisms of the plant lessen harmful effects of the salts. For both plant species, salinity decreased leaf and stem dry matter production, but increased leaf - to - stem ratio. In addition, salinity resulted in earlier flowering in Melilotus. Mineral composition was the most sensitive component of forage quality. Calculated sodium chloride concentrations were up to 125 g / kg DM in lucerne and 39 g / kg DM in Melilotus when irrigated with 110 mM NaCl. The concentrations of calcium and magnesium decreased in both species and approached the marginal range for animal production. Zinc concentration also decreased while potassium decreased in stems of lucerne only. The digestible organic matter ( DOMD ) in response to salinity varied between species. At the highest salt concentration, the whole shoot ( i.e., leaf and stem ) of lucerne decreased up to 4 percentage units while Melilotus increased by 6 percentage units. In lucerne, DOMD was influenced by a high concentration of soluble ash in leaf and stem and, in Melilotus, by an increase in the organic matter content of leaf and a reduction in lignin concentration in stem, which favoured higher digestibility. These results were supported by a histological study in which an increase in starch in Melilotus leaf, and a lower proportion of xylem in relation to parenchyma in stems, was measured. Crude protein concentration was not compromised and, in relation to Melilotus, coumarin concentration did not increase with salinity. In conclusion, the reduction in DM production of species with similar salt tolerance does not necessarily correspond to an equivalent reduction in nutritive value. This research represents the most detailed study into effects of salinity on glycophytic forage legumes. Results show that while some aspects of forage quality ( e.g., minerals composition and energy ) are strongly influenced by salinity, other aspects ( e.g., protein ) remain relatively unaffected. These findings have implications for development of productive grazing systems on saline agricultural land.
Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.

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

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.
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Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008