Tesi: "Plant-water relationships Western Australia"

1

Dolling, P. J. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia /". Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Dolling, Perry. "Lucerne (Medicago sativa) productivity and its effect on the water balance in southern Western Australia". University of Western Australia. Faculty of Natural and Agricultural Sciences, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0108.

Testo completo

Abstract (sommario):

[Truncated abstract] In southern Western Australia the replacement of deep-rooted native vegetation with annual species has resulted in rising water tables and increased salinity due to insufficient water use. The area has a Mediterranean-type climate where rainfall during summer is generally low but variable resulting in limited plant growth. However, if rainfall does occur it potentially can contribute to to the increased water excess or drainage by increasing the soil water content before the main drainage period in winter. The first study investigated factors controlling soil water content changes during the fallow (December to May) in annual farming systems. This was achieved by examining variation in available soil water storage to a depth of 1.0-1.5 m at three sites within 13 seasons. Reasons for the variation were examined using the Agricultural Production Systems Simulator (APSIM). This study also investigated the relationship between soil water content at the end of the fallow period (1 May) and the amount of drainage below 2.5 m by using APSIM coupled to historical weather records at three locations. At the end of the fallow a mean of 24 mm (or 25%) of rainfall during the fallow was retained in the soil. Losses of soil water during the fallow were due to evaporation (mean of 60 mm), transpiration from plant cover (mean of 12 mm) and drainage below the root zone and run off (combined mean of 13 mm). Soil water accumulation during the fallow period had a significant impact on simulated drainage under wheat in the following growing season. Every 1 mm increase in soil wetness at the end of the fallow resulted in a 0.7-1 mm increase in simulated drainage during the growing season. ... Variation in the water excess due to variation in rainfall was greater than the reduction in water excess due to lucerne. This makes the decisions about when to grow lucerne to reduce water excess difficult if livestock enterprises are less profitable than cropping enterprises. The findings of this PhD indicate that lucerne does have a place in Mediterranean-type environments because of its greater water use than current farming practices. However, its use needs to be strategic and the strategy will vary from region to region. For example, in the low rainfall region lucerne sowings need to be matched with high soil water contents and phase length will generally be short (2-3 years). In comparison at high rainfall regions lucerne will need to be grown for longer or combined with other strategies to increase water use.

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Lucas, Anne. "Water stress and disease development in Eucalyptus marginata (jarrah) infected with Phytophthora cinnamomi". Thesis, Lucas, Anne (2003) Water stress and disease development in Eucalyptus marginata (jarrah) infected with Phytophthora cinnamomi. PhD thesis, Murdoch University, 2003. https://researchrepository.murdoch.edu.au/id/eprint/167/.

Testo completo

Abstract (sommario):

The south-west of Western Australia has a Mediterranean climate and flora endemic to this area, including the keystone species, jarrah (Eucalyptus marginata), have adapted to the droughted summer conditions. The introduction of an exotic soil borne pathogen, Phytophthora cinnamomi, has challenged the survival of this and many other species. The expectation might be that plants stressed by drought are more susceptible to disease and this study examined the development of disease caused by P. cinnamomi in E. marginata and the significance of water status to that development. Seedlings of E. marginata, clonal plants resistant to P. cinnamomi and clonal plants susceptible to P. cinnamomi, were subjected to different watering regimes in a number of field and glasshouse experiments. To determine the level of drought stress that could be imposed on container-grown E. marginata seedlings without killing them, a preliminary experiment progressively lowered the moisture levels of the substrate in their containers, until the plants reached wilting point, at which time moisture was restored to a predetermined droughted level and the process repeated. With each subsequent droughting the wilting point was lower until it was found that the seedlings could survive when only 5% of the moisture lost from container capacity to wilting point was restored. No deaths had occurred after seedlings had been maintained at this low level for 14 days (Chapter 2). Based on these findings, the level of droughting maintained in all experiments conducted under controlled glasshouse conditions was 10% restoration. After testing the appropriateness of underbark inoculation, and a zoospore inoculation method for which no wounding was necessary, a new, non-invasive stem inoculation technique was developed. Stems were moistened in a pre-treatment, then agar plugs colonized with P. cinnamomi mycelium were held against the stem with wads of wet cotton wool and bound in place with tape. This technique resulted in a high proportion of infection in E. marginata (Chapter 4) without the need for underbark inoculation or the use of zoospores (Chapter 3). It was successfully used in a large field trial in a rehabilitated bauxite mine site with 2-year-old E. marginata clonal plants, resistant to P. cinnamomi (Chapter 5). Inoculation was in late spring after the winter and spring rainfall. This timing was to allow comparison of disease development in stressed plants under normal droughted summer conditions compared with itsdevelopment in non-stressed, irrigated plants. However, two months after inoculation, the area was deluged with unseasonal and abnormally heavy summer rainfall, negating any difference in the treatments and causing an outbreak of P. cinnamomi in the soil from an adjacent infested site. This resulted in the infection and death of some noninoculated control clones. Monitoring of the site continued for twelve months and the advance of P. cinnamomi at the site was mapped. To test the effect of drought on the expression of P. cinnamomi under more controlled conditions, a series of glasshouse experiments was set up that simulated two possible summer conditions; drought or drought followed by abnormally high summer rainfall. These experiments utilised E. marginata seedlings and clonal plants, some resistant and some susceptible to P. cinnamomi. Plants were inoculated with P. cinnamomi prior to or after droughting. Results were compared to those of control plants that had not experienced water deficit. In both seedlings and clonal plants, the greatest extent of colonization was found in plants which had experienced no water deficit. These results indicated that drought stress played a role in inhibiting the in planta development of P. cinnamomi in all genotypes (Chapter 8). This finding was consistent for both clones, susceptible and resistant to P. cinnamomi. Most recoveries were made from non-stressed clonal plants, resistant to P. cinnamomi (Chapter 6) and more colonization was found in non-stressed clonal plants, susceptible to P. cinnamomi (Chapter 7), than was recorded for droughted plants. The results of the field trial showed that P. cinnamomi was not recovered from some inoculated stems, which had obvious lesions, when segments were plated onto selective agar. This led to an intensive in vitro investigation into improved methods of recovery. Dark brown exudates from some segments of inoculated stems stained the surrounding agar onto which they were plated, suggesting the presence of phenolic compounds. Recovery of the pathogen from stems increased by about 10% when segments were first soaked in distilled water to leach out the phenolic compounds, then replated onto agar. Other recovery methods were also tested, including (1) baiting with Pimelea ferruginea leaves floated on the surface of water or soil filtrate, in which the infected stem segments were immersed and (2) the application of different light and temperature regimes. It was clearly shown that exudates from infected stems of field grown E. marginata inhibited the outgrowth of P. cinnamomi onto the agar. To counter the possible toxic effect that oxidized phenolics had on the growth of the P. cinnamomi, an antioxidant was added to the agar. P. cinnamomi was grown on media whichincorporated exudates from infected stems and different concentrations of ascorbic acid, with and without adjusted pH levels. There was a pronounced pH effect, with less growth on media with lower pH and no significant increase in growth of the mycelium with increased ascorbic acid concentration on pH adjusted agar (Chapter 9). The inhibitory effect of the exudates from the stem segments led to an investigation of the possibility that, if seedlings to be planted in the rehabilitation process could be pre-treated with phenolic compounds to render them more resistant, they may have an advantage when establishing in areas where there was a potential threat of P. cinnamomi. E. marginata seeds were germinated and the seedlings grown hydroponically in a constant temperature growth room. Different concentrations of synthetic catechol, a phenolic compound naturally occurring in E. marginata, were added to the nutrient solution. Roots remained immersed in the catechol solutions for three days, before being inoculated at the root tip with zoospores of P. cinnamomi. Roots in higher concentrations of catechol were less colonized than those in lower concentrations, indicating an increased resistance to the pathogen (Chapter 10). Further work is required to determine if seedlings treated before being planted in areas threatened by an outbreak of P. cinnamomi have a greater capacity for survival, and for how long the protection persists. The improved recovery of P. cinnamomi from infected plants is important for accurate assessment of the spread of the disease in an area and for the subsequent implementation of management strategies of containment and control. An outbreak of P. cinnamomi can impact on the revegetation of rehabilitated mine sites and the aetiology of the pathogen in mine sites needs to be more fully understood. The interaction of plant defences with the invasive pathogen has been examined in a range of environments in the field, the glasshouse, in a hydroponics system and in vitro. The results indicate that summer droughting increases the resistance of E. marginata to P. cinnamomi. However, more work is required to understand the mechanisms involved. The study also indicates that clones of E. marginata, selected as resistant to P. cinnamomi, are not resistant under all conditions and that environmental interactions should be further investigated. Lastly, for effective management strategies to be implemented it is critical that the pathogen can be confidently isolated from plants. It was shown that exudates from infected hosts inhibit the recovery of P. cinnamomi. Recovery methods that can overcome these inhibitory compounds are required. The findings invite further research into the complexity of host-pathogen relationships.

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Lucas, Anne. "Water stress and disease development in Eucalyptus marginata (jarrah) infected with Phytophthora cinnamomi". Murdoch University, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040820.13290.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Radomiljac, Andrew M. "Santalum album L. plantations: a complex interaction between parasite and host". Thesis, Radomiljac, Andrew M. (1998) Santalum album L. plantations: a complex interaction between parasite and host. PhD thesis, Murdoch University, 1998. https://researchrepository.murdoch.edu.au/id/eprint/270/.

Testo completo

Abstract (sommario):

This thesis examines a broad spectrum of physiological and silvicultural features of the highly valued woody angiosperm hemi-parasite Santalurn album L. (Indian sandalwood) in relation to its culture in plantations in northern Western Australia. Topics covered include allometry of host and Santalum when grown as single plant pairings in both field and pot culture, nutritional interactions between Santalum and beneficial and non-beneficial hosts, deleterious influences of parasitism on plantation productivity and heartwood induction in young trees. In Western Australia sandalwood is grown in the nursery for 8 months before establishment in the field and during this time a pot host is introduced. Survival of Santalurn after field establishment and its subsequent growth were significantly affected by the time of introduction of the pot host, Alternanthera nana. Increasing the period of the Santalum : Alternanthera association in the nursery to 109 days prior to field establishment markedly increased early growth of Salztalum plantations. Introduction at 134 days prior to field establishment was detrimental to the parasite as the Alternanthera was too vigorous for the small Santalum seedlings. Santalurn plants had a lower root : shoot ratio lower when cultured with Alternanthera in the nursery prior to field establishment compared with seedlings grown without Alternanthera. Alterrzantlzera survival in the field was high when it had been grown with Santalum for 12 weeks or more in the nursery prior to field establishment. After 1 1 weeks in the field a strong negative linear relationship was shown between Santalunz root : shoot ratio and Alternarzthera dry weight, and a positive linear relationship between Salztalum DW and Alternanthera DW. In Western Australia Santalu~n is established in the field with an intermediate host which nourishes the parasite for 3-5 years before Santalum becomes dependent on its long-term host and the intermediate host dies. The relationship between Santalum and several species tested as intermediate hosts was examined by pairing Santalum seedlings with intermediate host seedlings in 25 litre pots over a 10 month period. Growth of Santalum in pot culture with three N2-fixing woody intermediate hosts (Sesbania forrnosa, Acacia traclzycarpa and A. ampliceps), the woody non N2-fixing Eucalyptus camaldulensis or without a host varied considerably between host treatments. Santalum growth was greater and root : shoot ratio lower for seedlings grown with N2-fixing hosts compared with seedlings grown with E. carnaldulensis or with no host. The root : shoot ratio of unattached Santalum increased exponentially over time, whereas for all other treatments it remained relatively constant. An assessment of the value of the hosts, termed host use efficiency, was computed as Santalum shoot DW / host shoot DW. The host use efficiency of A. trachycalpa was greater than that of the other hosts. The xylem sap of hosts and Sarztalum, and ethanolic extracts of endophytic tissue of haustoria of Santalzkm were analysed for amino acids, organic acids and sugars to determine which solutes were available in the host and which were extracted by the Santalum haustoria from different hosts. There were similarities between Santalum and legume hosts in concentration and composition of xylem sap amino acids, and in the amino acid spectra of the corresponding Santalum endophytic tissue, whereas there were low N levels in xylem sap of E. camaldulensis and dissimilarities between its amino acid composition and that of Santalum. This indicated substantial direct intake of xylem N by Santalum from legume hosts but little N from the xylem sap of E. canzaldulensis. There were high concentrations of asparagine, glutamate, aspartate and y-amino glutamate in the xylem sap of the legume hosts, while in the non-legume the most common amino acids were glutamate, aspartate, glutamine and arginine. Proline, the predominant amino acid in the xylem sap of Santalum acurninatum growing in natural vegetation (Tennakoon et al. 1997) was not detected or present in very low concentrations in Santalurn album under these conditions. in the non-legume. Xylem sap of hosts contained variable amounts of sugars (sucrose, glucose and fructose) and organic acids (fumaric, citric and malic acid), whereas that of the parasitic Santalum was dominated by fructose and malic acid. Dissimilarities in the proportional amounts of xylem-borne sugars and organic acids were particularly evident for the E. camaldulensis : Santalum partnership. Diurnal profiles of photosynthesis and transpiration of Santalum were closely similar to those for corresponding hosts, whereas the midday leaf water potential of Santalum was consistently more negative than that of corresponding hosts. Net photosynthesis and water use efficiency was lower, but transpiration rates were similar to that of corresponding hosts. Nitrogen concentrations of foliage of Santalum were higher than their hosts, and higher when on legume hosts than on E. camaldulensis, or without a host. Nitrogen concentrations of Santalum foliage was strongly correlated with net photosynthesis and water use efficiency of Santalum. 813C values of shoot dry matter of Santalum were poorly correlated with instantaneous water use efficiency of Santalum. Tissue water relations of Santalum were similar to that of water-stress tolerant species. S. formosa proved the best host followed by Acacia ampliceps and A. traclzycarpa based on dry matter gains of Santalum. Estimates of heterotrophic gain of C of Santalum when grown in association with the legume hosts over a nine week period indicate 57.9% of C was derived from A. ampliceps, 45.5% from A. trachycarpa and 34.6% fiom S. fomosa. Abundance of haustorial attachments on roots of hosts was poorly correlated to Santalum shoot DW. Root nodules of legume hosts were parasitised by a small proportion of Santalum haustoria. Sodium and phosphorus concentrations of foliage of Santalum were generally higher than that of corresponding hosts. Net gains of calcium, potassium, phosphorus and sodium in Santalum was greatest when grown in association with hosts richest in the corresponding element. Net losses or only small gains of calcium, potassium, phosphorus and sodium were recorded when Santalum was grown with E. camaldulensis or without a host suggesting that Santalum has limited ability for uptake of those minerals through its own root system. To understand the effect of hosts on the productivity of a Santalum plantation a young plantation of Santalum with three host species Cathormion umbellatum, Sesbania formosa and Acacia anuera was selected to study the relationship between host quality and distance of hosts from Santalunz on Santalum health. The selected plantation showed marked decline in health and vigour of both Santalum and hosts between years 3 and 5. Parameters of the host plants were assessed to select the best predictor of Santalunz crown health. The height and diameter growth increment of Santalum between years 3 and 5 was strongly correlated to Santalum crown health. Santaluin crown health and growth increased as host quality increased, and the distance of host fiom Santalum decreased. An index, which combined host quality and the distance of the host from that of Santalum, was a better predictor of Santalum crown health than host distance or quality alone. The age at which heartwood is initiated in Santalum album under plantation conditions in Western Australia in unknown, but in natural stands in India it occurs between 10-13 years of age (Rai 1990). A field experiment was conducted to determine the efficacy of stem injections of paraquat andlor ethrel in initiating heartwood formation in five year old Santalum trees in a plantation. Trees injected with paraquat alone had a significantly greater extension of induced heartwood, both radially and vertically, than those trees injected with ethrel alone or distilled water. Eight months after treatment with paraquat or ethrel or a combination of these chemicals induced heartwood was formed, which had high lipid, and low starch and polysaccharide concentrations compared to the sapwood. Induced heartwood from both chemical treatments and their combinations contained total volatile oil and santalol oil (alpha and beta santalol) concentrations that were equal to or greater than that of naturally formed heartwood and greater than that of sapwood. Moisture content, and concentrations of K and Mg, and in some treatments Ca of induced heartwood were significantly lower than that of sapwood. The thesis concludes with a synthesis of the findings and suggestions for future research, with special reference to mid-rotation aspects of Santaltrm plantation silviculture.

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Radomiljac, Andrew M. "Santalum album L. plantations : a complex interaction between parasite and host". Murdoch University, 1998. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060818.134603.

Testo completo

Abstract (sommario):

This thesis examines a broad spectrum of physiological and silvicultural features of the highly valued woody angiosperm hemi-parasite Santalurn album L. (Indian sandalwood) in relation to its culture in plantations in northern Western Australia. Topics covered include allometry of host and Santalum when grown as single plant pairings in both field and pot culture, nutritional interactions between Santalum and beneficial and non-beneficial hosts, deleterious influences of parasitism on plantation productivity and heartwood induction in young trees. In Western Australia sandalwood is grown in the nursery for 8 months before establishment in the field and during this time a pot host is introduced. Survival of Santalurn after field establishment and its subsequent growth were significantly affected by the time of introduction of the pot host, Alternanthera nana. Increasing the period of the Santalum : Alternanthera association in the nursery to 109 days prior to field establishment markedly increased early growth of Salztalum plantations. Introduction at 134 days prior to field establishment was detrimental to the parasite as the Alternanthera was too vigorous for the small Santalum seedlings. Santalurn plants had a lower root : shoot ratio lower when cultured with Alternanthera in the nursery prior to field establishment compared with seedlings grown without Alternanthera. Alterrzantlzera survival in the field was high when it had been grown with Santalum for 12 weeks or more in the nursery prior to field establishment. After 1 1 weeks in the field a strong negative linear relationship was shown between Santalunz root : shoot ratio and Alternarzthera dry weight, and a positive linear relationship between Salztalum DW and Alternanthera DW. In Western Australia Santalu~n is established in the field with an intermediate host which nourishes the parasite for 3-5 years before Santalum becomes dependent on its long-term host and the intermediate host dies. The relationship between Santalum and several species tested as intermediate hosts was examined by pairing Santalum seedlings with intermediate host seedlings in 25 litre pots over a 10 month period. Growth of Santalum in pot culture with three N2-fixing woody intermediate hosts (Sesbania forrnosa, Acacia traclzycarpa and A. ampliceps), the woody non N2-fixing Eucalyptus camaldulensis or without a host varied considerably between host treatments. Santalum growth was greater and root : shoot ratio lower for seedlings grown with N2-fixing hosts compared with seedlings grown with E. carnaldulensis or with no host. The root : shoot ratio of unattached Santalum increased exponentially over time, whereas for all other treatments it remained relatively constant. An assessment of the value of the hosts, termed host use efficiency, was computed as Santalum shoot DW / host shoot DW. The host use efficiency of A. trachycalpa was greater than that of the other hosts. The xylem sap of hosts and Sarztalum, and ethanolic extracts of endophytic tissue of haustoria of Santalzkm were analysed for amino acids, organic acids and sugars to determine which solutes were available in the host and which were extracted by the Santalum haustoria from different hosts. There were similarities between Santalum and legume hosts in concentration and composition of xylem sap amino acids, and in the amino acid spectra of the corresponding Santalum endophytic tissue, whereas there were low N levels in xylem sap of E. camaldulensis and dissimilarities between its amino acid composition and that of Santalum. This indicated substantial direct intake of xylem N by Santalum from legume hosts but little N from the xylem sap of E. canzaldulensis. There were high concentrations of asparagine, glutamate, aspartate and y-amino glutamate in the xylem sap of the legume hosts, while in the non-legume the most common amino acids were glutamate, aspartate, glutamine and arginine. Proline, the predominant amino acid in the xylem sap of Santalum acurninatum growing in natural vegetation (Tennakoon et al. 1997) was not detected or present in very low concentrations in Santalurn album under these conditions. in the non-legume. Xylem sap of hosts contained variable amounts of sugars (sucrose, glucose and fructose) and organic acids (fumaric, citric and malic acid), whereas that of the parasitic Santalum was dominated by fructose and malic acid. Dissimilarities in the proportional amounts of xylem-borne sugars and organic acids were particularly evident for the E. camaldulensis : Santalum partnership. Diurnal profiles of photosynthesis and transpiration of Santalum were closely similar to those for corresponding hosts, whereas the midday leaf water potential of Santalum was consistently more negative than that of corresponding hosts. Net photosynthesis and water use efficiency was lower, but transpiration rates were similar to that of corresponding hosts. Nitrogen concentrations of foliage of Santalum were higher than their hosts, and higher when on legume hosts than on E. camaldulensis, or without a host. Nitrogen concentrations of Santalum foliage was strongly correlated with net photosynthesis and water use efficiency of Santalum. 813C values of shoot dry matter of Santalum were poorly correlated with instantaneous water use efficiency of Santalum. Tissue water relations of Santalum were similar to that of water-stress tolerant species. S. formosa proved the best host followed by Acacia ampliceps and A. traclzycarpa based on dry matter gains of Santalum. Estimates of heterotrophic gain of C of Santalum when grown in association with the legume hosts over a nine week period indicate 57.9% of C was derived from A. ampliceps, 45.5% from A. trachycarpa and 34.6% fiom S. fomosa. Abundance of haustorial attachments on roots of hosts was poorly correlated to Santalum shoot DW. Root nodules of legume hosts were parasitised by a small proportion of Santalum haustoria. Sodium and phosphorus concentrations of foliage of Santalum were generally higher than that of corresponding hosts. Net gains of calcium, potassium, phosphorus and sodium in Santalum was greatest when grown in association with hosts richest in the corresponding element. Net losses or only small gains of calcium, potassium, phosphorus and sodium were recorded when Santalum was grown with E. camaldulensis or without a host suggesting that Santalum has limited ability for uptake of those minerals through its own root system. To understand the effect of hosts on the productivity of a Santalum plantation a young plantation of Santalum with three host species Cathormion umbellatum, Sesbania formosa and Acacia anuera was selected to study the relationship between host quality and distance of hosts from Santalunz on Santalum health. The selected plantation showed marked decline in health and vigour of both Santalum and hosts between years 3 and 5. Parameters of the host plants were assessed to select the best predictor of Santalunz crown health. The height and diameter growth increment of Santalum between years 3 and 5 was strongly correlated to Santalum crown health. Santaluin crown health and growth increased as host quality increased, and the distance of host fiom Santalum decreased. An index, which combined host quality and the distance of the host from that of Santalum, was a better predictor of Santalum crown health than host distance or quality alone. The age at which heartwood is initiated in Santalum album under plantation conditions in Western Australia in unknown, but in natural stands in India it occurs between 10-13 years of age (Rai 1990). A field experiment was conducted to determine the efficacy of stem injections of paraquat andlor ethrel in initiating heartwood formation in five year old Santalum trees in a plantation. Trees injected with paraquat alone had a significantly greater extension of induced heartwood, both radially and vertically, than those trees injected with ethrel alone or distilled water. Eight months after treatment with paraquat or ethrel or a combination of these chemicals induced heartwood was formed, which had high lipid, and low starch and polysaccharide concentrations compared to the sapwood. Induced heartwood from both chemical treatments and their combinations contained total volatile oil and santalol oil (alpha and beta santalol) concentrations that were equal to or greater than that of naturally formed heartwood and greater than that of sapwood. Moisture content, and concentrations of K and Mg, and in some treatments Ca of induced heartwood were significantly lower than that of sapwood. The thesis concludes with a synthesis of the findings and suggestions for future research, with special reference to mid-rotation aspects of Santaltrm plantation silviculture.

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Collins, Shane. "Residue composition influences nutrient release from crop residues". University of Western Australia. School of Earth and Geographical Sciences, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0171.

Testo completo

Abstract (sommario):

[Truncated abstract] A greater adoption of stubble retention, minimum-till and no-till farming practices for the purposes of conserving soil, water and fertility requires a greater understanding of the complexity of physical and chemical interactions between the soil and crop residues. There is currently insufficient knowledge to allow reliable predictions of the effects of different residue types in different environments on soil fertility and crop growth, owing to the many residue characteristics and environmental interactions that have been shown to affect decomposition or nutrient release. The role of fibre and nutrient composition in nutrient release from crop residues, and implications for residue management techniques, were studied. Canola, lupin and field pea residues, obtained from farmland in Meckering and Northam, Western Australia, were separated into upper and basal stems, leaves, and siliques or pods. This was done to provide materials with a wide range of chemical and physical characteristics, and also allowed consideration of differential residue management of plant organs, such as comparing harvested canola siliques and retained canola stubble. Pre-treatment by chopping and/or humidification was applied to residues to provide some information about the processes of nutrient release. Residues were subjected to simulated rainfall to assess nutrient leaching from plant material, and placed on soil in pots in constant-temperature glasshouse conditions to assess decomposition. Amounts and rates of change of residue fibre and nutrients were determined throughout leaching and decomposition. Energy Dispersive X-ray (EDX) microanalysis was used to assess the location of diffusible ions in air-dried residues and the effects of humidification on nutrient positioning and release. ... However, the release of calcium and magnesium depended on the decomposition of the more recalcitrant components such as cellulose and lignin, as supported by microscopy results showing changes in nutrient distribution following humidification. The proportionality of amounts of calcium and magnesium leached and released during decomposition is likely to suggest a similarity of chemical form more than similarity of function or position of the two elements. Management of crop residues for maximising and optimising the timing of release of different nutrients will need to take into account the placement of different plant types and parts, particle sizes distribution and pre-treatment of material to efficiently manage short- and long-term soil fertility to sustain crops, particularly on degraded soils. Significant nutrient release of potassium, sulphur and magnesium from crop residues can be achieved from surface placement, with the release of potassium and sulphur managed by modifying residue particle size through appropriate harvesting, ploughing or sowing implement selection. High nutrient uptake crops and plant parts where they can be economically viable to grow or separated by the harvesting technique are particularly valuable as sources of nutrients and soil organic matter.

Gli stili APA, Harvard, Vancouver, ISO e altri

8

Horsnell, Tara Kathleen. "Quantifying thresholds for native vegetation to salinity and waterlogging for the design of direct conservation approaches". University of Western Australia. School of Environmental Systems Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0082.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Doole, Graeme John. "Value of perennial pasture phases in dryland agricultural systems of the eastern-central wheat belt of Western Australia". University of Western Australia. School of Agricultural and Resource Economics, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0213.

Testo completo

Abstract (sommario):

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.

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Setyawan, Dwi. "Soil development, plant colonization and landscape function analysis for disturbed lands under natural and assisted rehabilitation". University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0117.

Testo completo

Abstract (sommario):

[Truncated abstract] Spontaneous plant growth and soil development occur at disturbed sites with their extent and nature being variously affected by soil fertility status, local climate and topographic conditions. Soil-plant interactions can be diverse and site-specific within a disturbed landscape. The main purpose of the present study is to evaluate soil characteristics and landscape indices in relation to natural plant growth and soil development under different conditions and for diverse materials. A comprehensive study has been carried out to evaluate spontaneous soil development and plant colonization on various regolith materials at a railway cutting near Jarrahdale bauxite mine and on various substrates comprising waste rock, weathered regolith and replaced topsoil at Scotia (Norseman, Western Australia) and Kelian (East Kalimantan, Indonesia). At Jarrahdale soil development has occurred slowly over 36 years in relation to morphological changes in surface horizons. Soils at several locations exhibit substantial changes in color, texture and structure. The slow soil development is primarily due to low biomass and litter contributions (˜1 Mg/ha) from colonizing plants (e.g. Dryandra sessilis, Eucalyptus marginata and low shrubs) on the cutting shelf and slow litter decomposition. Nutrient accumulation is up to 5 kg N/ha, and 0.5 kg/ha for P and K. Surface soil samples from Jarrahdale are generally acidic (pH < 5.1) and contain low concentrations of total soil carbon (20 g/kg) and nutrients of total nitrogen (0.73 g/kg), bicarbonate-extractable phosphorus (bic-P) (< 2 mg/kg), bic-K (37 mg/kg) and total exchangeable bases (<1.1 cmol/kg, with 24 % base saturation). Soil properties at the Scotia waste dump are mainly associated with alkaline (mean pH = 9) and saline conditions (EC1:5 = 1.01 dS/m). Exchangeable base values are high with average concentrations of exchangeable Ca of 18 cmol/kg and exchangeable Mg of 6 cmol/kg, thus these elements are not a limiting factor for plant nutrition. Patchy plant growth on the waste dump is mostly related to differences in water availability in the arid region and to salinity such that halophytes (saltbushes Maireana and Atriplex) colonize many parts of the waste dump together with some Melaleuca and Eucalyptus species

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Poulter, Rachel. "Investigating the role of soil constraints on the water balance of some annual and perennial systems in a Mediterranean environment". University of Western Australia. Faculty of Agriculture, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0018.

Testo completo

Abstract (sommario):

This thesis compares the in situ water balance of common annual production systems (wheat, lupin, subclover and serradella) with a grazed perennial system (lucerne) at a site in the Avon Catchment, Western Australia. Using a physically-based water balance approach the value of a plant based solution in redressing the hydrological imbalance that has become a feature of much of the dryland agricultural region of Western Australia is investigated. The effectiveness of lucerne in providing greater available storage for buffering large rainfall events, as compared to the annual systems, is illustrated. Continued transpiration following out-of-season rainfall events maintains a larger available storage capacity. In contrast, the annual systems that are fallow over summer only withdrew a small fraction of water by soil evaporation between rainfall events. Under annual systems, the profile moisture store was sequentially increased to the extent that additional increments of rainfall could potentially contribute to deep drainage. A particular focus of this study has been to investigate the presence of soil constraints to root growth, and to assess how these constraints affect the water balance. A site survey indicated the soil penetration resistance was sufficient to impose a physical constraint to root growth. Published literature on the site shows soil acidity is also at a level imposing chemical constraints to root growth. A root growth model “Rootmodel”, for predicting root growth with and without soil constraints is examined in detail as a method for providing root growth parameters for inclusion into the numerical water balance model, SWIM based on Richard’s equation. Functions developed from “Rootmodel” adequately describe the effect of profile limitations to root growth, such as soil strength, moisture availability and temperature. Recommendations are made for inclusion of a growth suppressing function in “rootmodel” based on the chemical limitation of low pH. The effects of soil acidity on the root growth of several species is investigated experimentally and the resultant root data provided a reference point by which the simplified prediction of root growth built into SWIM could be adjusted using a linear reduction function. A similar linear reduction function is also employed to impose a physical constraint in the form of high penetration resistance.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Bleby, Timothy Michael. "Water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on mine rehabilitation sites in the jarrah forest of south-western Australia". University of Western Australia. School of Plant Biology, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0004.

Testo completo

Abstract (sommario):

[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Delaney, Belinda. "Verticordia micropropagation through direct ex vitro rooting". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2013. https://ro.ecu.edu.au/theses/615.

Testo completo

Abstract (sommario):

The objective of this study was to improve the existing shoot multiplication protocol for Verticordia grandis (McComb, Arthur & Newll, 1986; Newell, Growns & McComb, 2005) and to investigate and establish reliable root induction and acclimatisation protocols to enhance survival of micropropagated plantlets. It was envisaged that these protocols would be successful in micropropagation, growth and survival of different V. grandis clones and possibly applicable to other Verticordia species. The elongation of in vitro Verticordia shoots on multiplication media was improved by reducing the concentration of BAP from 1μM to 0.25 μM, which resulted in a more uniform shoot length of 4.5 – 5 cm; necessary for root induction experiments. The root induction protocol was optimised by determining the appropriate auxin concentration (80μM indole butyric acid; IBA) with an exposure time of 6 days. Acclimatisation and survival was greatly improved by transferring the IBA pulsed shoots to ex vitro conditions consisting of a free draining and aerated substrate (a mixture of peat and perlite 1:3) in crack pots. These were initially placed into a greenhouse (with controlled temperature & light conditions) in order to maintain high humidity. Over time humidity was reduced and after 112 days the plantlets were transferred to larger pots, containing fresh soil (peat/perlite/sand = 1:1:1) and placed in a shade house with a regular watering regime. Long-term survival was monitored and after 252 days survival was over 70%. The declining survival rates after this time has made it evident that field performance and long-term survival needs further investigation. The application of the improved shoot multiplication and root induction protocols on other V. grandis clones produced survival rates of 0 to 62.5% (depending upon clone) over 252 days.

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Hollick, Penelope Sarah. "Mycorrhizal specificity in endemic Western Australian terrestrial orchids (tribe Diurideae): implications for conservation". Thesis, Hollick, Penelope Sarah (2004) Mycorrhizal specificity in endemic Western Australian terrestrial orchids (tribe Diurideae): implications for conservation. PhD thesis, Murdoch University, 2004. https://researchrepository.murdoch.edu.au/id/eprint/103/.

Testo completo

Abstract (sommario):

The specificity of fungal isolates from endemic Western Australian orchid species and hybrids in the tribe Diurideae was investigated using symbiotic seed germination and analysis of the fungal DNA by amplified fragment length polymorphism (AFLP). The distribution of the fungal isolates in the field was also assessed using two different seed baiting techniques. The information from these investigations is essential for developing protocols for reintroduction and translocation of orchid species. Two groups of orchids in the tribe Diurideae were studied. Firstly, a number of Caladenia species, their natural hybrids and close relatives from the southwest of Western Australia were selected because orchid species from the genus Caladenia are considered to have among the most specific mycorrhizal relationships known in the orchid family ? an ideal situation for the investigation of mycorrhizal specificity. Secondly, species of Drakaea and close relatives, from the southwest of Western Australia and elsewhere in Australia, which are never common in nature and occur in highly specialised habitats, were selected to investigate the influence of habitat on specificity. Seed from the common species Caladenia arenicola germinated on fungal isolates from adult plants of both C. arenicola and its rare and endangered relative C. huegelii, while seed from C. huegelii only germinated on its own fungal isolates. The AFLP analysis grouped the fungal isolates into three categories: nonefficaceous fungi, C. huegelii type fungi, and C. arenicola type fungi. The group of C. huegelii type fungi included some fungal isolates from C. arenicola. An analysis of the AFLP fingerprints of C. arenicola fungal isolates from different collection locations showed that some, but not all, populations were genetically distinct, and that one population in particular was very variable. Despite being thought to have very specific mycorrhizal relationships, Caladenia species hybridise frequently and prolifically in nature, often forming self-perpetuating hybrid lineages. Five natural hybrids within Caladenia and its closest relatives were investigated. Symbiotic cross-germination studies of parental and hybrid seed on fungi from the species and the naturally occurring hybrids were compared with AFLP analyses of the fungal isolates to answer the question of which fungi the hybrids use. The germination study found that, while hybrid seeds can utilise the fungi from either parental species under laboratory conditions, it is likely that the natural hybrids in situ utilise the fungus of only one parental species. Supporting these observations, the AFLP analyses indicated that while the parental species always possessed genetically distinct fungal strains, the hybrids may share the mycorrhizal fungus of one parental species or possess a genetically distinct fungal strain which is more closely related to the fungus of one parental species than the other. The work on Caladenia hybrids revealed that C. falcata has a broadly compatible fungus that germinated seeds of C. falcata, the hybrid C. falcata x longicauda, and species with different degrees of taxonomic affinity to C. falcata. In general, germination was greater from species that were more closely related to C. falcata: seeds from Caladenia species generally germinated well on most C. falcata isolates; species from same subtribe (Caladeniinae) germinated well to the stage of trichome development on only some of the fungal isolates and rarely developed further; and seeds from species from different subtribes (Diuridinae, Prasophyllinae, Thelymitrinae) or tribes (Orchideae, Cranichideae) either germinated well to the stage of trichome development but did not develop further, or did not germinate at all. The AFLP analysis of the fungal isolates revealed that the fungi from each location were genetically distinct. In situ seed baiting was used to study the introduction, growth and persistence of orchid mycorrhizal fungi. A mycorrhizal fungus from Caladenia arenicola was introduced to sites within an area from which the orchid and fungus were absent, adjacent to a natural population of C. arenicola. In the first growing season, the fungus grew up to 50 cm from its introduction point, usually persisted over the summer drought into the second season and even into the third season, stimulating germination and growth to tuber formation of the seeds in the baits. Watering the inoculated areas significantly increased seed germination. Mycorrhizal relationships in Drakaeinae were less specific than in Caladeniinae. A study of the species Spiculaea ciliata revealed that this species, when germinated symbiotically, develops very rapidly and has photosynthetic protocorms, unlike all other members of the Drakaeinae. An AFLP analysis of the fungal isolates of this species grouped the isolates according to whether they had been isolated from adult plants or reisolated from protocorms produced in vitro. Isolates were genetically distinct when compared before germination and after reisolation. A cross-species symbiotic germination study of seeds of three Drakaea species and one Paracaleana species against fungal isolates from the same species and several other Drakaeinae species revealed lower specificity in this group than previously thought. A number of fungal isolates from Drakaea and Paracaleana species germinated two or more seed types, while all seed types germinated on fungal isolates from other species and the seed of Drakaea thynniphila germinated to some extent on every fungal isolate tested. An AFLP analysis of the Drakaeinae fungal isolates supported this information, revealing little genetic differentiation between the fungi of different orchid species. An ex situ seed baiting technique was used to examine the role of mycorrhizal fungi in microniche specialisation in the narrow endemic Drakaea. Soil samples from within and outside two Drakaea populations were tested for germination of the relevant seed types. In both cases, germination was significantly higher on soil samples from within than outside the populations, suggesting that the relevant mycorrhizal fungi may be restricted to the same microniches as the Drakaea species. The presence of similar fungi at distant, disjunct locations may be related to the extreme age and geological stability of the Western Australian landscape. The information from these investigations is essential for developing protocols for reintroduction and translocation of orchid species. It appears that the mycorrhizal relationships in these groups of orchids are not as specific as was previously thought. For reintroduction work, a broad sampling strategy is necessary, as it cannot be assumed that the same orchid species has the same fungus at different locations. A broadly compatible fungus may be of considerable utility in conservation work, such as in situations where a specific fungus appears to have poor saprophytic competence or where soil conditions have been altered. Seed baiting studies provide additional data on fungal distribution in situ. In general, molecular data do not provide information about efficacy or fungal distribution, so research programs that combine symbiotic germination studies with seed baiting investigations and genetic analyses of the fungi will provide the maximum benefit for designing more effective conservation programs.

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Hollick, Penelope Sarah. "Mycorrhizal specificity in endemic Western Australian terrestrial orchids (tribe Diurideae) : implications for conservation /". Hollick, Penelope Sarah (2004) Mycorrhizal specificity in endemic Western Australian terrestrial orchids (tribe Diurideae): implications for conservation. PhD thesis, Murdoch University, 2004. http://researchrepository.murdoch.edu.au/103/.

Testo completo

Abstract (sommario):

The specificity of fungal isolates from endemic Western Australian orchid species and hybrids in the tribe Diurideae was investigated using symbiotic seed germination and analysis of the fungal DNA by amplified fragment length polymorphism (AFLP). The distribution of the fungal isolates in the field was also assessed using two different seed baiting techniques. The information from these investigations is essential for developing protocols for reintroduction and translocation of orchid species. Two groups of orchids in the tribe Diurideae were studied. Firstly, a number of Caladenia species, their natural hybrids and close relatives from the southwest of Western Australia were selected because orchid species from the genus Caladenia are considered to have among the most specific mycorrhizal relationships known in the orchid family ? an ideal situation for the investigation of mycorrhizal specificity. Secondly, species of Drakaea and close relatives, from the southwest of Western Australia and elsewhere in Australia, which are never common in nature and occur in highly specialised habitats, were selected to investigate the influence of habitat on specificity. Seed from the common species Caladenia arenicola germinated on fungal isolates from adult plants of both C. arenicola and its rare and endangered relative C. huegelii, while seed from C. huegelii only germinated on its own fungal isolates. The AFLP analysis grouped the fungal isolates into three categories: nonefficaceous fungi, C. huegelii type fungi, and C. arenicola type fungi. The group of C. huegelii type fungi included some fungal isolates from C. arenicola. An analysis of the AFLP fingerprints of C. arenicola fungal isolates from different collection locations showed that some, but not all, populations were genetically distinct, and that one population in particular was very variable. Despite being thought to have very specific mycorrhizal relationships, Caladenia species hybridise frequently and prolifically in nature, often forming self-perpetuating hybrid lineages. Five natural hybrids within Caladenia and its closest relatives were investigated. Symbiotic cross-germination studies of parental and hybrid seed on fungi from the species and the naturally occurring hybrids were compared with AFLP analyses of the fungal isolates to answer the question of which fungi the hybrids use. The germination study found that, while hybrid seeds can utilise the fungi from either parental species under laboratory conditions, it is likely that the natural hybrids in situ utilise the fungus of only one parental species. Supporting these observations, the AFLP analyses indicated that while the parental species always possessed genetically distinct fungal strains, the hybrids may share the mycorrhizal fungus of one parental species or possess a genetically distinct fungal strain which is more closely related to the fungus of one parental species than the other. The work on Caladenia hybrids revealed that C. falcata has a broadly compatible fungus that germinated seeds of C. falcata, the hybrid C. falcata x longicauda, and species with different degrees of taxonomic affinity to C. falcata. In general, germination was greater from species that were more closely related to C. falcata: seeds from Caladenia species generally germinated well on most C. falcata isolates; species from same subtribe (Caladeniinae) germinated well to the stage of trichome development on only some of the fungal isolates and rarely developed further; and seeds from species from different subtribes (Diuridinae, Prasophyllinae, Thelymitrinae) or tribes (Orchideae, Cranichideae) either germinated well to the stage of trichome development but did not develop further, or did not germinate at all. The AFLP analysis of the fungal isolates revealed that the fungi from each location were genetically distinct. In situ seed baiting was used to study the introduction, growth and persistence of orchid mycorrhizal fungi. A mycorrhizal fungus from Caladenia arenicola was introduced to sites within an area from which the orchid and fungus were absent, adjacent to a natural population of C. arenicola. In the first growing season, the fungus grew up to 50 cm from its introduction point, usually persisted over the summer drought into the second season and even into the third season, stimulating germination and growth to tuber formation of the seeds in the baits. Watering the inoculated areas significantly increased seed germination. Mycorrhizal relationships in Drakaeinae were less specific than in Caladeniinae. A study of the species Spiculaea ciliata revealed that this species, when germinated symbiotically, develops very rapidly and has photosynthetic protocorms, unlike all other members of the Drakaeinae. An AFLP analysis of the fungal isolates of this species grouped the isolates according to whether they had been isolated from adult plants or reisolated from protocorms produced in vitro. Isolates were genetically distinct when compared before germination and after reisolation. A cross-species symbiotic germination study of seeds of three Drakaea species and one Paracaleana species against fungal isolates from the same species and several other Drakaeinae species revealed lower specificity in this group than previously thought. A number of fungal isolates from Drakaea and Paracaleana species germinated two or more seed types, while all seed types germinated on fungal isolates from other species and the seed of Drakaea thynniphila germinated to some extent on every fungal isolate tested. An AFLP analysis of the Drakaeinae fungal isolates supported this information, revealing little genetic differentiation between the fungi of different orchid species. An ex situ seed baiting technique was used to examine the role of mycorrhizal fungi in microniche specialisation in the narrow endemic Drakaea. Soil samples from within and outside two Drakaea populations were tested for germination of the relevant seed types. In both cases, germination was significantly higher on soil samples from within than outside the populations, suggesting that the relevant mycorrhizal fungi may be restricted to the same microniches as the Drakaea species. The presence of similar fungi at distant, disjunct locations may be related to the extreme age and geological stability of the Western Australian landscape. The information from these investigations is essential for developing protocols for reintroduction and translocation of orchid species. It appears that the mycorrhizal relationships in these groups of orchids are not as specific as was previously thought. For reintroduction work, a broad sampling strategy is necessary, as it cannot be assumed that the same orchid species has the same fungus at different locations. A broadly compatible fungus may be of considerable utility in conservation work, such as in situations where a specific fungus appears to have poor saprophytic competence or where soil conditions have been altered. Seed baiting studies provide additional data on fungal distribution in situ. In general, molecular data do not provide information about efficacy or fungal distribution, so research programs that combine symbiotic germination studies with seed baiting investigations and genetic analyses of the fungi will provide the maximum benefit for designing more effective conservation programs.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Mitchell, Patrick John. "From conduits to communities : plant water use strategies and evapotranspiration in a semi-arid ecosystem in south-western Australia". University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0034.

Testo completo

Abstract (sommario):

[Truncated abstract] Understanding the ecohydrological dynamics of native vegetation can provide a benchmark for future efforts to restore landscape hydrology and allow predictions of potential landscape responses to climate uncertainty and associated changes in vegetation cover. The key drivers of evapotranspiration (Et) involved in maintaining a hydrological balance that minimises deep drainage in semi-arid ecosystems operate at a range of scales, and in this thesis I assessed the water relations of functionally and taxonomically diverse plant communities in south-western Australia from the leaf-level to ecosystem scale. For three key communities; heath shrubland, mallee (small multistemmed eucalypt) -heath, and open eucalypt woodland, populating a typical catenary sequence of soil types along a slope, I addressed the following questions: 1) What are the predominant water use strategies of wheatbelt native plant communities and what underlying trade-offs determine the distribution of plant water use strategies along the topographical gradient? 2) What are the roles of soil water and hydraulic limitation in controlling the spatial and temporal dynamics of transpiration in different functional types? 3) What is the magnitude and partitioning of total Et in the woodland community and what processes determine Et fluxes on a seasonal and annual basis? 4) What are the seasonal differences in Et among contrasting community-types and how do these patterns relate to canopy attributes and transpiration capacity along the topographical gradient? A key philosophical step in working with species-rich communities was to develop the concept of 'hydraulic functional types' (HFTs) to identify groupings of species using associations of physiological and morphological traits that define their hydrological functioning. .... However, as shallow soils dried during spring and summer, Et fluxes were significantly lower at the heath site (0.35 versus 0.66 mm day-1 for the woodland in February), demonstrating that the seasonality of Et fluxes differentiates communityscale contributions to regional water balance. Land-surface exchange of water over native vegetation is by no means uniform, but varies according to the spatial and temporal availability of water along topographical gradients. In general, shallow soils present fewer opportunities for water use partitioning and favour drought hardiness and a transpiration response that tracks recent rainfall patterns, whereas deeper soils promote greater differentiation in water use strategy and support canopies responsive to atmospheric demand. This thesis provides a unique description of ecosystem water balance in a global biodiversity hotspot by viewing complex vegetation mosaics in terms of their relevant hydrological units. This information is fundamental to sustainable agroforestry and revegetation efforts and our ability to gauge possible changes in vegetation structure and function under a changing climate.

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Lenz, Tanja. "The effect of resource dynamics on invasive annual and native perennial grasses in grasslands of the mid-north of South Australia /". Title page, table of contents and abstract only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phl575.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Zencich, Sandra Jane. "Variability in water use by phreatophytic Banksia woodland vegetation of the Swan Coastal Plain, Western Australia". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2003. https://ro.ecu.edu.au/theses/1328.

Testo completo

Abstract (sommario):

Seasonal changes exist in source-water utilisation by Banksia woodland species overlying a shallow aquifer on the Swan Coastal Plain in Western Australia These were studied to identify the importance of groundwater as a water source to this vegetation. Intra-and interspecific variation in seasonal water use was investigated across the dominant overstorey and understorey species, with particular emphasis on species of different rooting morphologies. Seasonal water use was investigated across a topographical gradient ranging from a groundwater depth of 2.5 to 30 metres, a scenario representative of the coastal sand-dune system. An examination was also made of the response of woodland vegetation to an induced and rapid temporal separation from the groundwater able, beyond the normal range of groundwater fluctuation. To investigate a species' seasonal water usage, measurements of the naturally occurring stable isotope of hydrogen in water (deuterium, δ2H) were used to distinguish among potential plant water sources. Isotopic ratios from vascular water of the study species were compared with those of potential sources of precipitation, soil moisture and groundwater. The primary assumptions of this method were validated for the study species in laboratory experiments, and field-sampling strategies were developed. Through this process, the water sources available to plants were identified. Mixing models were employed to calculate the proportion of groundwater used. The results of this study confirm that groundwater is an important water source to both overstorey and understorey components of the woodland. Phreatophytic species were characterised by a deep root system, in which the tap root played a significant role in groundwater uptake. These species derived some of their water from groundwater throughout the dry-wet cycle. With the onset of the hot, Mediterranean summer, they increased their use of deep moisture sources, including groundwater. Variability in groundwater usage was observed at the interspecific and intraspecific level. This was dependent on root-system distribution and maximum root depth. For those species capable of using groundwater, the degree to which it was utilised was dependent on the proximity of groundwater (i.e. the depth to the water table), and the availability of moisture in shallower horizons of the soil profile (i.e. the season). For individuals occurring at shallow depth to water (< 8 m), groundwater was an important water source: whereas, at greater depths (≥8 m) its importance decreased as it was used in lower proportions and/or for shorter durations. Comparisons of within-species variation revealed disparities in groundwater usage, and possibly dependency, between the dominant overstorey Banksia species. Banksia ilicifolio, a species confined to habitats where groundwater depth is ≤8 m, was dependent on groundwater during the dry summer period (up to 90% of water used was groundwater) and may be considered a summer obligate phreatophyte. B. attenuata is a summer facultative phreatophyte, occurring where groundwater depth is 2 to >30m with groundwater accounting for between 5 to 75% of water used depending on depth to the water table. These results suggest the possibility of an obligate-facultative phreatophyte distinction. The response of phreatophytic Banksia species to changes in the groundwater regime beyond the normal range of groundwater fluctuation confirmed the seasonal nature of groundwater dependence, and varied sensitivity of individuals according to their position within the sandplain landscape (i.e. proximity to groundwater).

Gli stili APA, Harvard, Vancouver, ISO e altri

19

au, j. anderson@murdoch edu, e Jonathan Anderson. "Impacts of Amending Bauxite Residue Sands with Residue Fines for the Establishment of Vegetation on Residue Disposal Areas". Murdoch University, 2009. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090831.155453.

Testo completo

Abstract (sommario):

Long term storage of bauxite residue materials requires a capping stratum which will limit erosion while stabilizing slopes, limit deep infiltration of water into storage piles, and be aesthetically acceptable to the surrounding community. A diverse native vegetative community capable of surviving seasonal drought, low plant available water and nutrient constraints has the best potential of satisfying most, if not all of these requirements. Current and past rehabilitation of residue disposal areas (RDAs) using species native to southwest Western Australia has exhibited varying success. Current practices at Alcoa World Alumina Australias (Alcoa) Western Australia refineries have bauxite residue fines (< 150 ìm) stored within impoundments, in which the outer embankments are constructed with bauxite residue sands (> 150 ìm). The residue sands are also used as the growth media in the capping stratum for vegetation establishment on the disposal sites. Despite the inherently hostile properties of residue sand (pH > 10, EC(1:5) > 4 dS m-1, and ESP > 50), reductions in alkalinity (pH), salinity (EC) and sodicity (ESP) are corrected, through freshwater leaching, to a greater extent than is possible with residue fines. Although leaching can reduce the hostile character of residue sand, additions of phosphogypsum are typically added to expedite the removal of Na and alkalinity, and inorganic fertilizers are incorporated to improve the nutrient status of the growth media. However, due to the inconsistencies in vegetation establishment, which are attributed to poor water retention, inherent nutrient deficiencies and rapid loss of nutrients within residue sands (because of high hydraulic conductivity), further amendments are required. The aim of this study was to determine if amending the residue sand capping layer with residue fines would enhance its overall growth potential for vegetation establishment. Additions of fines to residue sands were predicted to increase water retention, add nutrients and increase the ability of the growth media to retain nutrients. Comparisons were made between the treated residue fines (seawater washed, carbonated, or unaltered) at a series of fines additions (1 - 20 % w/w) and a control(residue sand) amended with 2% (w/w) phosphogypsum and inorganic fertilizer. Comparisons were to determine the differences in 1) water retention, 2) nutrient concentrations and nutrient retention, and 3) plant growth responses and plant biomass nutrient concentrations between the growth media treatments. Four experiments were set up to measure differences in these variables which included: a glasshouse study involving the growth of Acacia saligna; a germination and emergence study (A.saligna); a two year field study in Western Australia; and a glasshouse column leaching study. Water retention increased with increasing percentage of residue fines addition. Plant available water (PAW) increased up to 110 %, with a 20 % increase in fines, representing an increase of 0.026 m3 PAW m-3 residue growth media, when compared to the residue sand only. This increase in PAW was attributed to changes in pore space distributions, due to the increasing fines contents altering the sandy texture to loamy sand texture class. However, initially much of this increase in PAW may not be realized, due to estimated temporary increases in osmotic potential associated with the high salt contents of residue sand and fines. Fines materials have much greater salt contents, and thus need to be leached to a greater extent than sands to remove the associated osmotic potential effects. Essential plant nutrients (P, K, S, Ca, Mg, and B) were increased with additions of residue fines in the glasshouse studies, although many nutrients (Mg, Zn, Mn and B) were still marginal for sustainable plant growth and development. Seawater treated residue fines additions produced the greatest increases in growth media nutrients with substantial increases in soluble (> 7 mg L-1) and exchangeable (> 0.10 cmolc kg-1) Mg, being up to 400 % greater than all other treatments. Along with these necessary nutrients, concentrations of Na were also increased in all fines additions treatments. Added Na may offset the benefits of fines additions, at least in the short term, due to inhibitions of cation uptake from Na competition. However, in the column leaching study soluble and exchangeable Na was lost rapidly from the profile, due to Ca and K displacement of Na from exchange sites during leaching. Soluble Na was removed from the profile to < 5 % of initial concentrations, after only three pore volumes of leaching, and exchangeable Na was removed from charge sites to less than 25 % of the initial concentration. Fines additions did increase concentrations of Mg and K on exchange sites, thus reflecting increased nutrient retention capacity relative to that in residue sand only. Plant growth responses and plant biomass nutrient concentrations were altered with the additions of residue fines to residue sands. The germination and emergence study demonstrated that the emergence of native seedlings was affected by additions of fines, due to the increased salinity and sodicity of the materials. Acacia saligna seedling emergence was inhibited by EC(1:5) > 2 dS m-1, which was highly correlated with a Na/Ca ratio of > 40, for all treatments, except the seawater fines additions. Seeds sown in seawater treatments emerged from growth media with EC(1:5) as high as 3.33 dS m-1 and appeared to be better correlated with Ca/Mg ratios than any other variable. Native vegetation growth responses showed mixed results in fines treated residues in the field. In the greenhouse study, plant growth tended to decrease with fines additions. Poor plant growth with increasing fines additions occurred despite the increased water retention and increased nutrients. This was attributed to the addition of Na associated with the residue fines, as increases in Na, EC and ESP in fines treatments all appear to have limited growth of Acacia saligna in the glasshouse over three months. Seawater fines additions had elevated Mg and B concentrations in plant biomass, and performed better than the carbonated or unaltered fines treatments, but still had reduced growth compared to the residue sand, which contained lower Na concentrations. Additional plant growth limitations may have occurred, due to possible plant nutrient deficiencies including: Mg, Zn, Mn and B and Na toxicity. Incorporation of residue fines into residue sands did increase water retention, nutrient concentrations and the nutrient retention capacity, but did not enhance the overall growth potential for vegetation, at least in the short term. Reductions in germination and emergence of seedlings and reduced plant growth were attributed to increases in Na concentrations introduced from the fines. Seawater washed residue fines had lower ESP and greater concentrations of nutrients, thus reducing the negative impacts from the additional Na introduced, and showed the greatest promise as a fines amendment. As leaching occurs over the first few initial months of rehabilitation, it is expected that the majority of the Na will be removed, from a system with an addition of 5 to 10 % fines, and the positive benefits of the fines additions will than be realized. Findings also illustrate that delaying the planting of vegetation on RDAs, until adequate leaching has occurred to reduce the Na concentrations, will substantially increase vegetation emergence and establishment.

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Mensforth, Lisa. "Water use strategy of Melaleuca halmaturorum in a saline swamp /". Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phm548.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Schymanski, Stanislaus Josef. "Transpiration as the leak in the carbon factory : a model of self-optimising vegetation". University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0095.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Rea, Naomi. "The influence of water regime on the population ecology of two emergent macrophytes in South Australia /". Title page, contents and summary only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phr281.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Vermeulen, Tarina. "Plant water relations of Elytropappus Rhinocerotis with specific reference to soil restrictions on growth". Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5416.

Testo completo

Abstract (sommario):

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The Renosterveld of the Western Cape region is often seen as a natural occurring veld type that will very easily re-establish itself wherever land is left unattended. In this study it was firstly noted that where wheatlands of the Berg River catchment (BRC) is left bare for a number of years, the renosterbos as a pioneer is slow in its re-growth response and when it does, certain patches in the landscape are preferred. This study therefore firstly focussed on the soil restrictions that widely determined the positions in the Berg River landscape where the renosterbos will re-establish itself. Secondly we needed to know whether some of the soil restrictions encountered could be alleviated and was possibly due to cultivation of this land. Through aerial observation it was found that a general patchiness does exist in the naturally occurring Renosterveld of the Voëlvlei area and hill tops of the region and was described by others as the true nature of this veld type. Closer investigation of the soils in the Voëlvlei reserve however showed that soil type played a major role in the patchiness found here. When re-growth of the renosterbos in previously cultivated areas was investigated, it was found that the soil type played the major role in the patchiness that occurred. The most commonly found soil restriction was soil density of the lower horizons. Any soil form that prevented the renosterbos to access the perched water table, to about 15m depth could not support the renosterbos. It is however our belief that soil could be prepared for the re-growth of renosterbos and through this action; renosterbos could also be used to alleviate the salinity problems found in this region. Additionally we investigated the impact of land-use change on the soil water balance and soil salinity by comparing a mature re-established stand of Renosterveld with an adjacent wheatfield. From the results, large differences in salinity and soil water behaviour were detected between the Renosterveld and wheatfield. Modelling of soil and plant water relations was done and the results were correlated well with field observations. This research also confirmed that the renosterbos through its deep rootedness is crucial in the conservation of other species found in the Renosterveld resulting from its ability to keep the water table down and with that the salts that is so often a problem in this area.
AFRIKAANSE OPSOMMING: In die Wes-Kaap word Renosterveld gesien as 'n veld tipe wat natuurlik voorkom en maklik sal hervestig in areas waar land sonder toesig gelaat word. In hierdie studie is dit eerstens opgemerk dat waar koringlande in die Berg Rivier opvanggebied kaal gelaat word vir 'n aantal jare, is die renosterbos as pionier stadig in sy hervestiging en wanneer terug groei wel plaasvind is dit selektief. Die studie fokus dus eerstens op grondbeperkinge wat die areas bepaal waar Renosterveld sal hervestig. Tweedens wou ons vasstel of die grondbeperkings wat voorkom in die grond en wat heel moontlik die oorsaak is van landbewerking opgehef kan word. Deur lugfoto-waarneming is dit gevind dat algemene leë kolle wel opgemerk is in die natuurlik plantegroei van die Renosterveld, in die Voëlvlei area, asook teen die berg hange. Dit word beskryf as 'n algemene kenmerk van die Renosterveld. Nadere ondersoek in die verskillende grondtipes van die area het egter gewys dat die grond tipe 'n belangrike rol speel in die voorkoms en groei van die renosterbos en uiteindelik die (her-)vestiging van Renosterveld. Die terug groei van die renosterbos is ondersoek in voorheen bewerkte lande. Dit is gevind dat die grond tipe 'n belangrike rol speel in die voorkoms van die leë kolle in die Renosterveld. Die mees algemene grond beperking wat opgemerk is, was die verdigte sub-horisonte. Enige grondvorm wat toegang van die renosterboswortels tot by die grondwatertafel (tot by 'n diepte van 15m) beperk, is nie voldoende om die groei van 'n volwasse renosterbos te onderhou nie. Dit is egter ons oortuiging dat die grond voorberei kan word vir die hervestinging van die renosterbos en deur dit te bewerkstellig sal grondversouting beheer kan word. Die impak van landgebruikverandering op die grondwaterbalans en grondversouting is ook ondersoek, deur 'n volwasse stand van Renosterveld te vergelyk met 'n nabygeleë koringveld. Die resultate het getoon dat daar groot verskille in die grondwatervlakke, asook die soutinhoud tussen die Renosterveld en die koringland voorkom. Modellering van die grond-en plantwaterverhouding is uitgevoer en data het goed gekorreleer met veld waarnemings. Die studie het bevestig dat die natuurlike bewaring van die diep gewortelde renosterbos noodsaaklik is vir die voortbestaan van blom- en skilpadspesies wat slegs in die Renosterveld voorkom asook die vermoë van die renosterbos om stygende watertafels en versouting te beheer waar dit dikwels 'n probleem in hierdie area is.

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Sumardi. "The influence of water stress on flowering and fruit production of Capsicum annuum Longum (chilli peppers) /". View thesis View thesis, 1993. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030604.113630/index.html.

Testo completo

Abstract (sommario):

Thesis (M.Sc. (Hons)) -- University of Western Sydney, Hawkesbury, 1993.
"A thesis submitted in fulfilment of the requirements for the degree of Master of Science (Honours) at the University of Western Sydney, Hawkesbury, School of Horticulture" Bibliography : leaves [126]-145.

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Jenkins, Sommer. "Ecophysiological principles governing the zonation of puccinellia (Puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) on saline waterlogged land in south-western Australia". University of Western Australia. School of Earth and Geographical Sciences, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0133.

Testo completo

Abstract (sommario):

Puccinellia (puccinellia ciliata) and tall wheatgrass (Thinopyrum ponticum) often show ecological zonation in saline landscapes, with puccinellia occurring in less elevated more saline/waterlogged locations, and tall wheatgrass occurring in more elevated less saline/waterlogged locations. The aims of this study were to: (a) characterize the observed ecological zonation at a field site, (b) quantify the effects of variables likely to explain growth differences of the two plants in glasshouse experiments, and (c) identify and compare anatomical and physiological mechanisms that explain these zonation patterns. At an experiment in the field near Kojonup (0522824E, 6244579N), puccinellia was found to colonise the lower more severely salinised and waterlogged zones of the landscape, with tall wheatgrass occupying the higher less affected zones. These differences in zonation were clearly associated with variance in soil salinity and water-table depth. Glasshouse experiments in soil revealed that low pH values, low calcium concentrations and variation in salinity alone did not explain the ecological zonation observed in the field. However, there was a substantial difference in the responses of the two plant species to waterlogging in combination with salinity. Puccinellia grew better under saline waterlogged conditions than tall wheatgrass, which was associated with better regulation of Na+ and K+ under saline/waterlogged conditions than in tall wheatgrass. Under non-saline conditions, waterlogging (hypoxia) decreased shoot weights in puccinellia by 15% and in tall wheatgrass by 20%. Similar growth results were obtained in nutrient solution culture, where waterlogging was simulated by lowering the oxygen in solutions through bubbling with N2 gas. Under saline hypoxic conditions, puccinellia, compared to tall wheatgrass, showed increased growth and maintenance of selectivity of K+ over Na+ across adventitious roots. Solution experiments revealed adaptive traits responsible for conveying better growth and ion maintenance present in puccinellia, but not tall wheatgrass, such as inducement of a barrier to radial oxygen loss in the basal regions of adventitious roots (not previously reported in the literature for puccinellia), formation of root aerenchyma and packing of cortical cells and suberin deposition in hypodermal and endodermal root cell layers. These results should assist in targeting pasture species, and predicting their growth response, in saline and waterlogged landscapes. Further work on examining the genetic material of puccinellia is warranted in order to identify genes that could be transferred into crop plants to convey salt and waterlogging tolerance.

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Blanch, Stuart James. "Influence of water regime on growth and resource allocation in aquatic macrophytes of the lower River Murray, Australia /". Title page, summary and contents only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phb639.pdf.

Testo completo

Abstract (sommario):

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).

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Grigg, Alasdair M. "An ecophysiological approach to determine problems associated with mine-site rehabilitation : a case study in the Great Sandy Desert, north-western Australia". University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0118.

Testo completo

Abstract (sommario):

[Truncated abstract] Establishment of vegetation and ecosystem functioning is central to the mitigation of environmental impacts associated with mining operations. This study investigated the ecophysiological functioning of mature plants in natural vegetation and applied this knowledge to diagnose problems affecting plant health and causes of poor plant cover at a mine-rehabilitation site. Ecophysiological parameters, including plant water relations and mineral nutrition, were studied in conjunction with soil physical, hydraulic and chemical properties. The natural ecosystem at the study location in the Great Sandy Desert is characterised by sand dunes and interdunes with distinct plant communities on each. One of the most notable features of the vegetation is the presence of large Corymbia chippendalei trees high on the dunes and relatively small scattered shrubs in the interdunes. Triodia grasses (spinifex), dominate the vegetation in both habitats but different species occur in each; T. schinzii is restricted entirely to the dunes, and T. basedowii occurs only in the interdunes. It was hypothesised that the deep sandy dunes afford greater water availability but lower nutrient supply to plants in this habitat compared with those occurring in the lower landscape position of the interdunes. Water-relations parameters (leaf water potentials, stomatal conductance, d13C) revealed that dune plants, particularly woody species, displayed higher water status and water use than closely related and often congeneric plants in the interdunes. Nutrient concentrations in soils were significantly higher in the interdunes, but concentrations in foliage were similar for related species between habitats. It is concluded that the dunes provide a greater store of accessible water than the soil profile in the interdunes. ... Following an experimental wetting pulse equivalent to a summer cyclone event, A. ancistrocarpa plants displayed significant increases in stomatal conductance, leaf water potential and sap velocity in lateral roots within three days of irrigation at the natural site and two days at the rehabilitation site. Secondary sinker roots originating from distal sections of lateral roots were evidently supplying water to maintain hydraulic function in laterals, thus enabling a fast pulse response. This was accentuated at the rehabilitation site where roots were confined closer to the surface. These results indicate that plants at the rehabilitation site are more dependent on small pulses of water and have less access to deep reserves than plants at the natural site. It is concluded that high runoff losses and insufficient soil depth are major factors contributing to plant water stress, and combined with the direct impacts of erosion, are largely responsible for plant death and ultimately poor plant cover. These issues can be alleviated if cover soil depth is increased to more than 0.5 m and slope angles are reduced to <12o. This study demonstrates the value of an ecophysiological approach for diagnosing problems affecting plant establishment at mine-rehabilitation sites. Furthermore, it has provided recommendations that will improve the rehabilitation strategy and lead to the development of a well vegetated, resilient ecosystem on a stable and non-polluting land form.

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Habib, Ramy. "Life cycle GHG emissions and water consumption for a hypothetical 400 MW coal-fired power plant in Western Australia: Impacts of carbon capture and a comparison of two prevailing carbon capture technologies". Thesis, Habib, Ramy (2017) Life cycle GHG emissions and water consumption for a hypothetical 400 MW coal-fired power plant in Western Australia: Impacts of carbon capture and a comparison of two prevailing carbon capture technologies. Masters by Coursework thesis, Murdoch University, 2017. https://researchrepository.murdoch.edu.au/id/eprint/40483/.

Testo completo

Abstract (sommario):

Carbon capture technology is expected to play a significant role in Australia to meet its long-term commitment for reducing greenhouse gas (GHG) emissions, so it is important to evaluate its impact by conducting an environmental life cycle assessment to evaluate the total GHG emissions and total lifecycle water consumption. In this study, a hypothetical 400MW sub-critical coal-fired power plant in Western Australia without carbon capture is considered as the base case. The total life cycle GHG emissions and life cycle water consumption are compared with two prevailing carbon capture technologies (e.g. oxy-fuel combustion and post-combustion carbon capture). The results show that both carbon capture technologies will reduce the total GHG emissions but will result in an increase of the total life cycle water consumption during the power plant operation and coal mining as a result of the energy penalty imposed by the use of carbon capture technology and the additional water requirement of the carbon capture system (e.g. direct contact cooler in case of post-combustion carbon capture). The study, also, shows that oxy-fuel combustion with carbon capture is more efficient in carbon abatement with less water requirement compared to post-combustion carbon capture. A sensitivity analysis is conducted to investigate the effect of using different combustion technologies for the base case and the effect of reducing the percentage of carbon captured on the total GHG emissions and water consumption for all scenarios. This trade-off between GHG abatement and water consumption as a result of using carbon capture technology will require the use of an environmental indicator that assess the water requirement for different low-carbon technologies against the base case. The Water-Carbon Abated Ratio indicator (WCAR) is proposed as a single indicator that measures the amount of water consumed or saved for each kilogram of carbon abated. The study shows that oxy-fuel combustion is more efficient in reducing GHG emissions with lower impact on water consumption compared to post-combustion carbon capture (e.g. oxy-fuel combustion has higher WCAR values compared to post-combustion carbon capture).

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Cooling, Marcus Paul. "Adaptations of aquatic macrophytes to seasonally fluctuating water levels / by Marcus Paul Cooling". 1996. http://hdl.handle.net/2440/18913.

Testo completo

Abstract (sommario):

Bibliography: leaves 105-121.
viii, 133, [28] leaves : ill. ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
This thesis tests the hypothesis that plant strategies to respond to seasonal flooding can be used to predict their tolerance to variation in water regime. The studies illustrate contrasting strategies for survival in seasonally fluctuation water levels. These are tested in the field against similar species. Plants are surveyed at four stages of flooding at Bool Lagoon. The morphologically plastic species, V. reniformis and Triglochin procerum, respond to flooding with taller shoots and increased investment in photosynthetic tissue. It is concluded that the reproductive effort is much lower in the field than in the pond experiments, and changes in the population density of both species are not related to water regime.
Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997?

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Cooling, Marcus Paul. "Adaptations of aquatic macrophytes to seasonally fluctuating water levels / by Marcus Paul Cooling". Thesis, 1996. http://hdl.handle.net/2440/18913.

Testo completo

Abstract (sommario):

Bibliography: leaves 105-121.
viii, 133, [28] leaves : ill. ; 30 cm.
This thesis tests the hypothesis that plant strategies to respond to seasonal flooding can be used to predict their tolerance to variation in water regime. The studies illustrate contrasting strategies for survival in seasonally fluctuation water levels. These are tested in the field against similar species. Plants are surveyed at four stages of flooding at Bool Lagoon. The morphologically plastic species, V. reniformis and Triglochin procerum, respond to flooding with taller shoots and increased investment in photosynthetic tissue. It is concluded that the reproductive effort is much lower in the field than in the pond experiments, and changes in the population density of both species are not related to water regime.
Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997?

Gli stili APA, Harvard, Vancouver, ISO e altri

31

St, Clair Peter James. "Responses of Eucalyptus globulus spp. globulus and E. grandis to salinity and waterlogging". Phd thesis, 1997. http://hdl.handle.net/1885/145385.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Barrett, Damian Joseph. "Ecophysiological bases for the distribution of rainforest and eucalypt forest in Southeastern Australia". Phd thesis, 1992. http://hdl.handle.net/1885/142215.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Donohue, Randall James. "Vegetation - water dynamics in the Australian landscape". Phd thesis, 2009. http://hdl.handle.net/1885/148238.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Mensforth, Lisa. "Water use strategy of Melaleuca halmaturorum in a saline swamp / by Lisa Jane Mensforth". Thesis, 1996. http://hdl.handle.net/2440/18922.

Testo completo

Abstract (sommario):

Bibliography: leaves 214-239.
xviii, 239 leaves : ill., maps ; 30 cm.
The aim of this study is to identify the water use strategy of Malaleuca halmaturorum in response to salinity and waterlogging in the root zone and through this quantify groundwater use and the role of M. halmaturorum in the water balance. The water use strategy of M. halmaturorum is investigated in the saline ephemeral swamps of South Eastern South Australia to understand the effect of the wetland vegetation on the groundwater balance and the survival mechanisms and reasons for the decline in health of M. halmaturorum in the region.
Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1997

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Rea, Naomi. "The influence of water regime on the population ecology of two emergent macrophytes in South Australia / by Naomi Rea". Thesis, 1993. http://hdl.handle.net/2440/20591.

Testo completo

Abstract (sommario):

Bibliography: leaves 103-120.
1 v. (various pagings) : ill. (some col.), maps ; 30 cm.
Species interactions are dependent on the water regime, which affects the relative allocation to below (sediment resource acquisition) and above ground (C acquisition) parts. At shallow and regularily exposed sites, Baumea is the superior competitor. In Hacks and Bool Lagoon, South Australia, changing distribution patterns occur in deep and permanently flooded conditions, where Baumea dies back, paving the way for Triglochin to passively take it's place.
Thesis (Ph.D.)--Dept. of Botany, University of Adelaide, 1993

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Weidemann, Stephanie Lyn. "Spatial and temporal variability of transpiration in the Gwydir and Namoi catchments from 2000-2004". Master's thesis, 2006. http://hdl.handle.net/1885/147127.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Lenz, Tanja I. "The effect of resource dynamics on invasive annual and native perennial grasses in grasslands of the mid-north of South Australia / Tanja Lenz". 2004. http://hdl.handle.net/2440/22082.

Testo completo

Abstract (sommario):

"July 2004."
Bibliography: leaves 120-136.
vii, 136 leaves : ill. (some col.), maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Investigates the effects of soil moisture dynamics on the growth and interactions between invasive annual grasses and native perennial grasses in the mid-north of South Australia. At most sites annual grass abundance was positively correlated with rainfall, soil moisture after rainfall and higher soil productivity. Perennial grass abundance was negatively correlated with annual grass abundance and soil moisture after rainfall, and was weakly positively correlated with percentage summer rainfall, elevation, radiation, gravel and slope. Overall perennial grasses responded little to the environmental variables investigated, but strongly to annual grass abundance, while for annual grasses soil moisture was the driving variable.
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Lenz, Tanja I. "The effect of resource dynamics on invasive annual and native perennial grasses in grasslands of the mid-north of South Australia / Tanja Lenz". Thesis, 2004. http://hdl.handle.net/2440/22082.

Testo completo

Abstract (sommario):

"July 2004."
Bibliography: leaves 120-136.
vii, 136 leaves : ill. (some col.), maps ; 30 cm.
Investigates the effects of soil moisture dynamics on the growth and interactions between invasive annual grasses and native perennial grasses in the mid-north of South Australia. At most sites annual grass abundance was positively correlated with rainfall, soil moisture after rainfall and higher soil productivity. Perennial grass abundance was negatively correlated with annual grass abundance and soil moisture after rainfall, and was weakly positively correlated with percentage summer rainfall, elevation, radiation, gravel and slope. Overall perennial grasses responded little to the environmental variables investigated, but strongly to annual grass abundance, while for annual grasses soil moisture was the driving variable.
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Environmental Biology, 2004

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Blanch, Stuart James. "Influence of water regime on growth and resource allocation in aquatic macrophytes of the lower River Murray, Australia / by Stuart James Blanch". Thesis, 1997. http://hdl.handle.net/2440/19198.

Testo completo

Abstract (sommario):

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?

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "Plant-water relationships Western Australia"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili