Dissertations / Theses on the topic 'Lower River Murray'

Thesis (Ph. D.)--University of Adelaide, Depts. of Zoology and Botany, 1998?
Addendum inserted. Includes copies of author's previously published papers. Includes bibliographical references (p. 390-414).

Vegetation along the River Murray floodplains has been shown to be in a severe state of decline. This decline is amplified by the impositions of river regulation. In South Australia, where vegetation losses have been great, regeneration is limited and may result in not only individual tree losses but also widespread population decline. This study aimed to examine the relationship between river flows and the regeneration process in populations of Eucalyptus camaldulensis and Eucalyptus largiflorens. The current structure of the populations was examined to determine if a viable number of varying age-classed trees were present. Tree surveys conducted at Banrock Station determined that while densities were low for both species, E. camaldulensis had a more sustainable population structure than E. largiflorens. Growth stages for both species illustrated highly clumped distribution, which is believed to correspond with river flooding magnitudes and frequencies. To address the potential link between tree distribution and flooding within the River Murray, a hydrological analysis was conducted for Banrock Station using river flows at the South Australian border from 1900 to 2003. The amount of time growth stages for each species were inundated was found to be greatly reduced under regulated flows compared to natural flows. This has resulted in shifted localized regeneration patterns corresponding with E. camaldulensis' greater demand for inundation than E. largiflorens. Moderate magnitude flows have been most impacted by regulation, and consequently these are the very flows needed for floodplain tree population maintenance. Flowering and seed fall for E. camaldulensis and E. largiflorens were monitored at Banrock Station for 22 months to identify losses in reproductive potential resulting from tree decline. While seed viability was not affected by vigour, trees with visually reduced vigour were found to produce less fruit and had reduced seed fall, as well as a reduced rate of fruit development. Dendrochronological techniques were applied to floodplain trees. Age and size relationships could be established, implying that such techniques can be applied in South Australia to high quality sites. Growth responses within cohorts were similar and easily matched between individuals illustrating cyclic, but not necessarily seasonal correlations. This work verified the preferential selection of younger trees for dendroecological studies, and identified a relationship between on moderate flows and measurable girth expansion in both floodplain tree species.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.

Thesis (B. Sc. (Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1996.
One folded chart in pocket on back cover. Australian National Grid reference Adelaide sheet S1 54/9 Renmark sheet S1 54/10 1:250 000. Includes bibliographical references (leaves 38-42).

Copy of author's previously published article inserted. Bibliography: leaves 198-217. This thesis explores the impact of sustained disturbances on the ecology of algal dominated biofilms in the Lower River Murray, South Australia. It focuses on the physical effects of regulation through changes to the light environment and water level regime, and the local effects of grazing. The nutritional signficance of biofilms for the abundant populations of prawns and shrimps in the Lower Murray is also examined.

Copy of author's previously published article inserted.
Bibliography: leaves 198-217.
249 leaves : ill., maps ; 30 cm.
This thesis explores the impact of sustained disturbances on the ecology of algal dominated biofilms in the Lower River Murray, South Australia. It focuses on the physical effects of regulation through changes to the light environment and water level regime, and the local effects of grazing. The nutritional signficance of biofilms for the abundant populations of prawns and shrimps in the Lower Murray is also examined.
Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 1997?

Vegetation along the River Murray floodplains has been shown to be in a severe state of decline. This decline is amplified by the impositions of river regulation. In South Australia, where vegetation losses have been great, regeneration is limited and may result in not only individual tree losses but also widespread population decline. This study aimed to examine the relationship between river flows and the regeneration process in populations of Eucalyptus camaldulensis and Eucalyptus largiflorens. The current structure of the populations was examined to determine if a viable number of varying age-classed trees were present. Tree surveys conducted at Banrock Station determined that while densities were low for both species, E. camaldulensis had a more sustainable population structure than E. largiflorens. Growth stages for both species illustrated highly clumped distribution, which is believed to correspond with river flooding magnitudes and frequencies. To address the potential link between tree distribution and flooding within the River Murray, a hydrological analysis was conducted for Banrock Station using river flows at the South Australian border from 1900 to 2003. The amount of time growth stages for each species were inundated was found to be greatly reduced under regulated flows compared to natural flows. This has resulted in shifted localized regeneration patterns corresponding with E. camaldulensis' greater demand for inundation than E. largiflorens. Moderate magnitude flows have been most impacted by regulation, and consequently these are the very flows needed for floodplain tree population maintenance. Flowering and seed fall for E. camaldulensis and E. largiflorens were monitored at Banrock Station for 22 months to identify losses in reproductive potential resulting from tree decline. While seed viability was not affected by vigour, trees with visually reduced vigour were found to produce less fruit and had reduced seed fall, as well as a reduced rate of fruit development. Dendrochronological techniques were applied to floodplain trees. Age and size relationships could be established, implying that such techniques can be applied in South Australia to high quality sites. Growth responses within cohorts were similar and easily matched between individuals illustrating cyclic, but not necessarily seasonal correlations. This work verified the preferential selection of younger trees for dendroecological studies, and identified a relationship between on moderate flows and measurable girth expansion in both floodplain tree species.
Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.

"October 2003"
Errata inside front cover.
Bibliography: p. 289-313.
iii, 334 p. : ill., map, photo (col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This thesis examines the influence of 'water regime', or spatial and temporal patterns in the presence of water, on the floristic composition of wetlands on the River Murray in South Australia. It explores the hypothesis that the composition of wetland vegetation is determined by components of the water regime, namely depth, duration and the rate and timing of flood and drawdown.
Thesis (Ph.D.)--University of Adelaide, Cooperative Research Centre for Freshwater Ecology and School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

"October 2003"
Errata inside front cover.
Bibliography: p. 289-313.
iii, 334 p. : ill., map, photo (col.) ; 30 cm.
This thesis examines the influence of 'water regime', or spatial and temporal patterns in the presence of water, on the floristic composition of wetlands on the River Murray in South Australia. It explores the hypothesis that the composition of wetland vegetation is determined by components of the water regime, namely depth, duration and the rate and timing of flood and drawdown.
Thesis (Ph.D.)--University of Adelaide, Cooperative Research Centre for Freshwater Ecology and School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

Riverbank collapse is a natural and expected phenomenon associated with the evolution of rivers worldwide and has been studied extensively over the last two decades and remains an active research topic. The evolution of riverbank stability analysis has followed closely the developments in analytical methods, investigation tools, stabilisation methods and data acquisition technology. Furthermore, the stability of riverbanks is a multifaceted issue which involves the study of geology, topography, stratigraphy, hydrology, climate, spatial variation and geotechnical engineering. The River Murray is one of the only river systems in the world that can fall below sea level due to the barrages preventing the inflow of sea water during periods of low river flows. Over the last few years, an unprecedented period of dry conditions and low flows between 2005 – 2010 led to more than 162 reported riverbank collapse-related incidents along the Lower River Murray, in South Australia (downstream of Lock 1 at Blanchetown to Wellington). Those collapse-related incidents threatened public infrastructure, private property and the safety of river users, and also provide significant challenges for environmental and river management. From the inventory of the South Australian Department of Environment, Water and Natural Resources (DEWNR), riverbank collapse, erosion, cracking, tree leaning and collapse and levee problems are the main forms of the recorded incidents. Geographical information systems (GIS) is well known for its efficient and cost-effective spatial data processing capabilities, which include spatial data collection, manipulation and analysis, and has been widely used in riverbank instability research. As a significant feature of this thesis, GIS, incorporating high-resolution spatial data, such as aerial photographs and LIDAR (light detecting and ranging) images, facilitates the assessment of riverbank instability in several ways. Firstly, the actual location of the historical collapse can be determined and verified by the use of high-resolution aerial image comparison and interpretation to facilitate accurate back-analyses. Secondly, the 2D and 3D geometry of the riverbank is able to be readily extracted from the LIDAR digital elevation models (DEMs). Thirdly, the dimensions of the predicted collapsed regions can be validated against high-resolution aerial images, and finally, the influencing factors are able to be manipulated and mapped with GIS to predict regions susceptible to riverbank collapse. This thesis aims to: (1) examine the failure mechanisms affecting riverbank collapse along the Lower River Murray and identify the most relevant mechanism; (2) identify potential triggers for riverbank collapse events that should be monitored and managed in the future; (3) develop a framework, incorporating spatial information, GIS and geotechnical data, to facilitate the prediction of riverbank collapse along the Lower River Murray (between Blanchetown and Wellington, South Australia); and (4) develop a framework, based on GIS and geotechnical data, to identify regions susceptible to high risk of riverbank collapse along the Lower River Murray. In order to realise these aims, numerical analyses have been performed using two commercially available software programs, ArcGIS and SVOffice, which integrate the limit equilibrium method, back-analysis of collapse incidents, transient unsaturated flow modelling, steady state modelling, and DEMs and high-resolution aerial images within a GIS framework. The modelling has been informed by a series of geotechnical investigations undertaken at various sites along the River Murray.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Civil, Environmental & Mining Engineering, 2015.

Addendum inserted.
Includes copies of author's previously published papers.
Bibliography: p. 390-414.
xvi, 420, [13] p. : ill., maps ; 30 cm.
Aims to examine the effects of water regime on growth, vegetative recruitment, resource allocation and photosynthesis in selected perennial species, and the adaptations permitting them to tolerate sub-optimal regimes.
Thesis (Ph.D.)--University of Adelaide, Depts. of Zoology and Botany, 1998?

"January 2003"
Amendments in pocket inside back cover.
Bibliography: leaves 212-229.
xi, 229 leaves : ill. (some col.), map, plates (col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2003

"January 2003"
Amendments in pocket inside back cover.
Bibliography: leaves 212-229.
xi, 229 leaves : ill. (some col.), map, plates (col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2003

Most of the lower River Murray and its floodplain wetlands are impacted upon by degradation caused by river regulation. Increasingly the restoration of these ecosystems and the river water quality has become a high priority for federal and state governments and associated departments and agencies. Public concern is adding to the pressures on these departments and agencies to restore these ecosystems and to sustainably maintain the river water quality. The long term monitoring of floodplain wetlands has been limited, compounding the difficulties faced by managers and decision makers on assessing the potential outcome of restoration options. The role of this project in the broad scheme of restoration/rehabilitation is to contribute to the construction of a model capable of increasing managers and decision makers understanding, and build consensus of potential outcomes of management option. This model was to use available data. The developed model, based on WETMOD developed by Cetin (2001), simulates wetland internal nutrient processes, phytoplankton, zooplankton and macrophyte biomass as well as the interaction (nutrient and phytoplankton exchange) between wetlands and the river. The model further simulates the potential impact management options have on the wetlands, and their nutrient retention capacity, and therefore their impact on the river nutrient load. Due to the limitation of data, wetlands were considered in categories for which data was available. Of these two had sufficient data to develop, calibrate and validate the model. Management scenarios for these two wetlands were developed. These scenarios included, the impact of returning a degraded wetland in a turbid state to a rehabilitated clear state, and the impact the removal of nutrient from irrigation drainage inflows has on wetland nutrient retention, and consequent input to the river. Scenarios of the cumulative impact of the management of multiple wetlands were developed based on using these two wetlands, for which adequate data was available, as “exemplar” wetlands, i.e. data from these wetlands were substituted for other similar wetlands (those identified as belonging to the same category). The model scenarios of these multiple wetlands provide some insight into the potential response management may have on individual wetlands, the cumulative impact on river nutrient load and how wetland morphology may relate to management considerations. The model is restricted by data availability and consequently the outputs. Further, some limitations identified during the development of the model need to be addressed before it can be applied for management purposes. However, the model and methods provide a guide by which monitoring efforts can assist in developing future modelling assessments and gain a greater insight not only at the monitoring site but also on a landscape scale.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1320131
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Includes list of publications issued during the candidature.
Bibliography: leaves 176-197.
iii, ix, 197, [22] leaves : ill., maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Phosphorus retention was measured in five pilot-scaled constructed wetlands with different configurations in terms of macrophyte species and substrates in order to evaluate the phosphorus removal efficiency of water plants and substrates in experimental ponds; assess the contribution of macrophytes to phosphorus removal through direct uptake, modification of water chemistry and impacts on the phosphorus adsorption characteristics of substrate; and, contribute to the optimal design and operation of constructed wetlands for the treatment of agricultural drainage water.
Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002?

Includes list of publications issued during the candidature.
Bibliography: leaves 176-197.
iii, ix, 197, [22] leaves : ill., maps ; 30 cm.
Phosphorus retention was measured in five pilot-scaled constructed wetlands with different configurations in terms of macrophyte species and substrates in order to evaluate the phosphorus removal efficiency of water plants and substrates in experimental ponds; assess the contribution of macrophytes to phosphorus removal through direct uptake, modification of water chemistry and impacts on the phosphorus adsorption characteristics of substrate; and, contribute to the optimal design and operation of constructed wetlands for the treatment of agricultural drainage water.
Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002?

The major assumption of currently accepted fish recruitment hypotheses (e.g. flood pulse concept and flood recruitment model) is that in the absence of overbank flows the main river channel does not provide adequate food and habitat for larvae and juveniles. However, periods of low flows are common throughout floodplain rivers, and there are a wide diversity of life history strategies exhibited by riverine fish. Therefore, the broad applicability of these assumptions to the management of all fish species and floodplains rivers has been questioned. The low flow recruitment hypothesis pioneered the concept that some fishes can successfully spawn and recruit during low flows by utilising main channel habitats. Characteristics of the river channel, flow regime and level of regulation are often distinctly different both within and between rivers, and many of the recruitment models and indeed the life history strategies of fishes, remain untested in alternative floodplain river systems. River regulation has resulted in altered flow regimes in river systems throughout the world, and in turn, has a range of negative impacts on the fish populations. The Murray-Darling Basin is Australia’s largest river catchment and has been severely affected by river regulation. To test some of the assumptions of the previously described recruitment models larval fish and zooplankton sampling was conducted in the main channel environments of the Lower River Murray, South Australia. In comparison to the rest of the Murray-Darling Basin, the Lower River Murray is unique due to the combination of four distinct geomorphologic regions, the absence of significant tributaries, and the high degree of regulation. Extensive river regulation has drastically reduced the natural flow variability of the Lower River Murray. Furthermore, there has been little work on the spawning and larval assemblages within this region. Larval fish sampling is often used for studying the early life history of fishes, but sampling gear and diel timing of sampling can bias results. Pelagic plankton tows were the single most effective method for collection of most species. Diel variation was identified for many species; with most exhibiting higher abundances during the night, although one species occurred in higher abundances during the day. Given these results the sampling regime for this project utilised both day and night pelagic plankton tows. Annual differences in the larval assemblages in relation to variations in hydrology and environmental variables were investigated across four years, including a year of increased flow and a water level raising, and three years of low regulated flow with stable water levels. The main channel environment of the Lower Murray supported larvae from all life history strategies. The larval assemblage differed between years; the flow pulse year was consistently different from the subsequent three low flow years. Three responses to varying hydrology were identified in the larval assemblage: larvae that were 1) positively correlated to increased flow, 2) negatively correlated to the increased flow and 3) correlated to temperature. The low flow recruitment hypothesis was supported, with a number of smallmedium bodied native species spawning under low flow conditions in the river channel. However, golden perch and silver perch (flow cued spawners), were only present during the flow pulse year. Environmental flows are therefore vitally important for the management and restoration of some native fish species. Strong within year variability was inherent in the data due to the seasonal variation in spawning time of fishes. The timing of peak spawning in the Lower River Murray was compared to other studies throughout the Basin. The broad spawning patterns identified for individual species were similar to seasonal spawning guilds identified for Australian species in previous studies. These spawning guilds were spring/summer and summer spawners. Understanding the timing of spawning of key species within a region will ensure that management actions can be targeted at providing benefits for species of interest. The key assumption of many recruitment models is that the main river channel is an area of low productivity, and therefore it does not provide adequate food for developing larvae, which is particularly pronounced in years of low flow. Zooplankton sampling was conducted during the spring/summer of 2006 in the pelagic zone of the main river channel in a typical low flow year. Although temporally and spatially restricted, results indicated that during a low flow year an abundant prey source does exist in the main river channel in the Lower River Murray. Furthermore the prey was abundant in the pelagic zone of the open water, where traditionally pelagic zooplankton abundances have been documented to be relatively low. This suggests that in the absence of floodplain inundation developing larvae have adequate access to food in this lowland temperate system. The inundated floodplain is generally recognised as important habitat for developing, larvae, consequently the importance of the main channel environment is frequently overlooked despite many studies highlighting the importance of shallow, still littoral zones. Larval fish were sampled in three main channel habitats: backwaters, open water and still littoral zones. Larvae of key species successfully spawned and utilised these main channel habitats during a low flow year. Specifically, still littoral zones and backwaters were important main channel habitats for developing fish larvae, providing support for the applicability of the low flow recruitment hypothesis to the Lower River Murray. Some species (namely the small – medium bodied natives were able to spawn and recruit in the Lower River Murray under low flow conditions, but these were also able to spawn under the higher flow conditions. However, during the low flow years there were no larvae golden perch or silver perch collected, suggesting that these species were not spawning under the low flow conditions. This study has highlighted that a number of species will spawn and develop as larvae in the heavily regulated weir pool environment. In addition, adequate food and habitat were available for developing fish larvae in the absence of floodplain inundation in the Lower River Murray. However, for species with specific flow requirements (such as golden perch and silver perch, and potentially Murray cod and freshwater catfish) continued low flow conditions may pose a significant threat. In heavily regulated systems, environmental water allocations should be considered to manage and potentially restore declining fish populations, and the benefit of within channel flow pulses should not be underestimated.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2010

Riparian environments have degraded world-wide as a consequence of human development and climatic change. The native floodplain tree communities of semi-arid river systems are under stress from reduced flooding frequencies as a consequence of water extractions, river regulation and climate change. In regions with saline aquifers, river regulation and land management have also caused soil salinisation, further impacting on floodplain tree health. The lower River Murray in south-eastern Australia is a major ecological asset considered as an area of international significance. The dominant floodplain vegetation is suffering severe decline in health, with approximately 80% of floodplain trees reported as being in poor condition or dead. A reduction in water availability from reduced flooding and soil salinisation, has been identified as the primary cause. This has resulted from large irrigation extractions across the Murray-Darling Basin and elevated saline groundwater levels due to river regulation and land clearance. Management of these ecosystems needs to address both surface and groundwater changes. Increasing flooding regimes from environmental flow management and lowering of groundwater in regions of shallow saline aquifers are the most common scenarios adopted world-wide. Traditionally the assessment of management options for floodplain habitats has focussed on changes in river flow with no consideration given to surface water and groundwater interactions. In addition groundwater has been treated as a single homogenous unit. Wide floodplains have high spatial variability of habitats due to historic meandering anabranch creek systems that cause changing elevations and soil types. This in turn creates a highly variable pattern of surface and groundwater interactions. This thesis investigates the major causes of floodplain tree decline and develops methods for predicting the spatial impacts on floodplain tree health from a range of management scenarios. Surface and groundwater changes are often highly inter-connected but are usually considered separately at regional scales because of the complexity of management and modelling of surface and groundwater interactions over large areas. This thesis addresses the surface and groundwater changes at the regional scale of the lower River Murray. A floodplain inundation model for the River Murray (RiM-FIM) is developed to predict the extent of flooding at various magnitudes of flow and river regulation and a ‘drought index’ was used to indicate the risk to floodplain tree health of changing flow regimes. A floodplain impacts model (FIP) was applied spatially to predict groundwater discharge onto the floodplain and model vegetation risk. At the floodplain scale, surface and groundwater need to be integrated to assess detailed management scenarios. This thesis develops a method for assessing soil water availability from surface and groundwater interactions using a spatial and temporal model of salt accumulation and recharge (WINDS). This model is then used to predict floodplain tree health. The thesis contributes to the science of floodplain processes and develops a number of innovative modelling techniques for predicting the spatial variability of floodplain tree impacts, improving on traditional broad assessment methods. The tools are applicable to other saline semi-arid rivers and are useful for environmental flow and groundwater management decision making.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2013

"August 2004"
Includes bibliographical references.
xi, 108 p. : ill., maps, plates ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
"This thesis extends and summarises Australian data on carp (Cyprinus carpio L.) reproductive biology and early growth. Specifically, it (1) validates the aging of larval and early-juveniles via daily otolith increment counts, (2) provides regression equations to account for shrinkage that occurs upon preservation of young-of-the-year (YOY) carp in 70 and 95% ethanol, (3-4) investigates the timing, frequency and duration of spawning via gonad staging and via a combination of gonad staging and YOY sampling, and (5) investigates relationships between YOY recruitment and nine hydro-climatic parameters, and examines spatial and temporal variation in YOY growth."
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

Bibliography: leaves 361-390.
425, [50] leaves : ill. (chiefly col.), maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Geography and Anthropology, 1995

This thesis explores the hydrological factors that may contribute to the observed distribution patterns of invasive willows (Salix) and native trees (Eucalyptus camaldulensis, E. largiflorens and Acacia stenophylla) along the Lower River Murray (LRM) in southern Australia. An initial survey, establishing the diversity and flowering biology of Salix taxa was carried out to ascertain the extent of invasion, and the likelihood of hybridisation, which may accelerate invasion. S. babylonica, S. fragilis, S. × chrysochoma and S. × rubens occur in the study region, each represented by a single gender. None were present on floodplains, but the most dominant taxon, S. babylonica, occurred along the entire length of the main channel. No seed or seedlings were observed; hence reproduction is likely to be asexual. More detailed survey work was then carried out to characterise the distribution patterns of the dominant S. babylonica and co-occurring natives (Eucalyptus camaldulensis, E. largiflorens and Acacia stenophylla) along a hydrologic gradient produced by the extensive weir system in the LRM. In weir pools, variation in daily water levels of weir pools is low (± 0.1 m) immediately upstream of the weir, but higher immediately downstream (0.2-1.0 m daily). The distribution of natives was uniform across weir pools, while S. babylonica was more abundant above weir structures, suggesting low tolerance to variable water regimes. Hypotheses relating to the observed distribution patterns were then tested experimentally on juveniles of the S. babylonica, E. camaldulensis and A. stenophylla. The experiment was carried out in outdoor ponds using an orthogonal design, with four elevations in relation to water level (-25 cm, 0 cm +25 cm, + 50 cm) under each of three water regimes. Experimental water regimes manipulated the magnitude of daily water level changes (static, 0 m dayˉ¹ ; moderate, ± 0.05 - 0.15 m dayˉ¹; high, ± 0.2 -0.5 m dayˉ¹) to mimic typical hydrological conditions across weir pools in the LRM. Final biomass and mean relative growth rates (S. babylonica, 0.0403 ± 0.002 g mˉ²dayˉ¹ A. stenophylla, 0.0249 ± 0.0017 g m ˉ² dayˉ¹; E. camaldulensis, 0.0204 ± 0.0016g mˉ² dayˉ¹) of all 3 species were unaffected by water regimes (i.e. water fluctuations), but were affected by elevation. Survival of both S. babylonica and A. stenophylla was lowest at low elevations where inundation was high. At higher elevations (+25 cm, +50 cm) the RGR of S. babylonica juveniles was much higher than the native juveniles. To test if the persistence of adults of each species along hydrologic gradients were associated with differing tolerances to water deficits and water use characteristics, S. babylonica and native species were examined under typical hydrological conditions in the field and during an unusual drawdown. S. babylonica occurring at the lowest elevations on riverbanks, had the least negative predawn shoot water potential (ψpredawn), followed by the natives, which were at higher elevations. A. stenophylla had the lowest stable carbon isotope ratio (δ¹³C) values (by 1.7 ‰) on the riverbank; suggesting more profligate water use than S. babylonica and E. camaldulensis. However, all riverbank trees had significantly less negative ψpredawn and lower δ¹³C than native trees on floodplains, consistent with higher water availability on riverbanks. The position and stable oxygen isotope ratio (δ¹⁸O) values were consistent with riverbank S. babylonica sourcing their water directly from the river or from shallow soil-water sources (<0.25 m). In floodplain habitats, depth to water was > 2.5 m, and groundwater was 5 times more saline (4.97 ± 0.88 dS mˉ¹) than river-water. Native trees with deep roots, the ability to lower water potentials and alter water use efficiencies may be at an advantage in this habitat relative to S. babylonica. Extreme low flows in the LRM, over a 6-month period, provided an opportunity to assess how S. babylonica and E. camaldulensis responded to a river-water drawdown. During the drawdown, river-water levels fell at a rate of ~2 – 2.5 mm dayˉ¹ and dropped to a minimum of 0.42 m below the designated pool level. S. babylonica and E. camaldulensis maintained high ψpredawn across the drawdown period, most likely because riverbank soil water availability was not limited; as depth to water table only decreased marginally (≤0.15 m) and soil water content and soil water potential were high (<1.1 MPa). However, an above average rainfall in February 2003 significantly increased soil water potential in the upper 0.25 m of the riverbank, which correlated with a significant increase in ψpredawn in E. camaldulensis, suggesting they were able to use shallow, precipitation derived soil-water sources whereas S. babylonica were not. Also under hot, dry conditions, S. babylonica had higher transpiration rates and lower instantaneous water use efficiencies than co-occurring E. camaldulensis. This suggests that S. babylonica may consume larger volumes of water per unit leaf area than natives, if access to water is maintained.
Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2010