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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Phytoplankton and turbulence at selected scales

Regel, Rudi Herbert. January 2003 (has links) (PDF)
Bibliography: leaves 309-329. This thesis attempts to contribute to the understanding of how turbulence affects phytoplankton in freshwater systems, focussing on the temporal and spatial scales in phytoplankton dynamics ranging from photochemistry in the surface mixed layer to a small-scale shear and growth to intra-seasonal changes in community composition in a lake subject to high disturbances.
2

Ecology and management of weeds under no-till in southern Australia

Chauhan, Bhagirath Singh January 2006 (has links)
No - till systems have been widely adopted by farmers in Australia over the past decade to reduce soil erosion, improve soil physical and chemical properties, conserve soil moisture and save on fuel costs. These changes in tillage practices can have a major influence on the ecology and management of weeds. Studies were undertaken on the seed biology of six important Australian weed species to provide underpinning knowledge of their response to tillage. Field studies were also undertaken to investigate the effect of no - till on weed seedling emergence, seed bank persistence and herbicide behaviour. Seed germination of threehorn bedstraw and wild turnip, the latter only at sub - optimal temperatures, was inhibited by light. In contrast, seed germination of common sowthistle and Indian hedge mustard was stimulated by light. Seed germination of small - flowered mallow was not influenced by the light conditions. Seedling emergence of threehorn bedstraw, wild turnip, small - flowered mallow and annual ryegrass was low on the soil surface but increased with shallow burial, which suggests that farming practices that achieve shallow burial of seeds are likely to promote greater seedling emergence of these weed species. In contrast, seedling emergence of common sowthistle and Indian hedge mustard was greatest for the seeds present on the soil surface and emergence decreased with increased burial depth. In field experiments, low soil disturbance tillage systems left more seeds on the soil surface after crop sowing, whereas high soil disturbance systems buried most of the seeds. Seedling emergence of annual ryegrass, threehorn bedstraw and wild radish was greater under minimum tillage than no - till system. In contrast, seedling emergence of Indian hedge mustard, common sowthistle, silvergrass, small - flowered mallow and turnipweed was greater under the no - till system. Seedling emergence of wild oat and wild turnip was not influenced by the tillage system. Even though seedling emergence of annual ryegrass was much lower under no - till, the persistence of residual viable seeds of annual ryegrass from one season to the next was similar between the tillage systems. This was because of much greater seed decay under no - till ( 48 to 60 % ) than that recorded under minimum tillage ( 12 to 39 % ). All dinitroaniline herbicides ( trifluralin, pendimethalin and oryzalin ) were more effective in reducing the number of plants, spikes, dry matter and seed production of annual ryegrass when incorporated at sowing with tines than with the discs. At Minlaton in 2004 and 2005, bioavailable trifluralin was greater under tillage systems with greater levels of soil disturbance than under lower soil disturbance systems. In the absence of the herbicide, annual ryegrass was less competitive with wheat under the disc - sown systems. The response of grain yield to herbicides was greater under the tine - sown systems than the disc - sown systems. The performance of S - metolachlor on annual ryegrass control was investigated under no - till. The control of annual ryegrass was greater than 80 % when S - metolachlor was applied at sowing ( incorporated by sowing or post - sowing pre - emergence ). However, application of the herbicide at sowing resulted in phytotoxic effects on crop emergence and grain yield of wheat. Application of S - metolachlor at 20 or 23 days before sowing not only provided effective control ( 74 to 83 % ) of annual ryegrass, it was also safe on wheat. Application of this herbicide at 40 or 46 days before sowing was relatively ineffective in controlling annual ryegrass ( 33 to 49 % weed kill ) but safe on wheat. In conclusion, soil disturbance caused by tillage was found to have a major influence on the behaviour of the seed bank of different species including seedling emergence and decay rates of weed seeds. However, the response to tillage tended to be species - specific and was related to their seed biology. Tillage systems also had a major influence on the efficacy and bioavailability of trifluralin, which is prone to volatilisation losses. The findings of this research program are expected to contribute to the improvement in weed management under no - till systems. / Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.
3

Phytoplankton and turbulence at selected scales / by Rudi Herbert Regel.

Regel, Rudi Herbert January 2003 (has links)
Bibliography: leaves 309-329. / xvii, 329 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis attempts to contribute to the understanding of how turbulence affects phytoplankton in freshwater systems, focussing on the temporal and spatial scales in phytoplankton dynamics ranging from photochemistry in the surface mixed layer to a small-scale shear and growth to intra-seasonal changes in community composition in a lake subject to high disturbances. / Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, 2003
4

Sustaining the western myall woodlands : ecology and mangement

Ireland, Carolyn. January 1997 (has links) (PDF)
Bibliography: leaves 227-244. This study is conceived to address various aspects of western myall (Acacia papyrocarpa Benth) recruitment, lifespan, distribution and the effects of major vertebrates on the species' ecology over the major part of its range in South Australia. A study of the population dynamics of the species is done to assess the adequacy of net recruitment. Population structure is examined across the woodlands. The new concept of "fossil paddocks" is adopted to investigate the historical impact of introduced herbivores on the landscape.
5

The ecology of Melangyna viridiceps and Simosyrphus grandicornis (Diptera : Syrphidae) and their impact on populations of the rose aphid, Macrosiphum rosae

Soleyman-Nezhadiyan, Ebrahim. January 1996 (has links) (PDF)
Bibliography: leaves 213-233. This thesis studies the influence of the two common syrphid species on populations of rose aphids in rose gardens in Adelaide. The study determines whether the provision of attractive flowers increases the suppressive effect of syrphids on rose aphids and analyses some ecological and biological aspects of two syrphid species -- Melangyana viridiceps (Macquart) and Simosyrphus grandicornis (Macquart) -- in a Mediteranean climate to obtain a better understanding of their biological control potential.
6

Sustaining the western myall woodlands : ecology and management / by Carolyn Ireland.

Ireland, Carolyn January 1997 (has links)
Bibliography: leaves 227-244. / xiv, 244 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. / This study is conceived to address various aspects of western myall (Acacia papyrocarpa Benth) recruitment, lifespan, distribution and the effects of major vertebrates on the species' ecology over the major part of its range in South Australia. A study of the population dynamics of the species is done to assess the adequacy of net recruitment. Population structure is examined across the woodlands. The new concept of "fossil paddocks" is adopted to investigate the historical impact of introduced herbivores on the landscape. / Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Science and Rangeland Management, 1997
7

The ecology of Melangyna viridiceps and Simosyrphus grandicornis (Diptera : Syrphidae) and their impact on populations of the rose aphid, Macrosiphum rosae / by Ebrahim Soleyman-Nezhadiyan.

Soleyman-Nezhadiyan, Ebrahim January 1996 (has links)
Bibliography: leaves 213-233. / xiii, 255 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis studies the influence of the two common syrphid species on populations of rose aphids in rose gardens in Adelaide. The study determines whether the provision of attractive flowers increases the suppressive effect of syrphids on rose aphids and analyses some ecological and biological aspects of two syrphid species -- Melangyana viridiceps (Macquart) and Simosyrphus grandicornis (Macquart) -- in a Mediteranean climate to obtain a better understanding of their biological control potential. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1997
8

The taxonomy, morphology and reproduction of the Myrionemaceae, Elachistaceae, Corynophlaeceae and Giraudyaceae (Phaeophyceae) in Southern Australian / Stephen Skinner

Skinner, Stephen January 1980 (has links)
Typescript (photocopy) / vii, 228 leaves, [43] leaves of plates : ill. ; 31 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1981
9

Ecology and behaviour of Pachycephala rufogularis and P. inornata (Aves: Pachycephalidae) in woodlands of South Australia.

Moise, Dragos January 2009 (has links)
Since European settlement, the woodlands and associated habitats, especially in the temperate zones of Australia, have been extensively cleared and converted to arable land and pastures. Much of the remaining vegetation in the agricultural zone occurs as small isolated patches prone to disturbance and degradation. Apart from habitat loss and fragmentation, altered fire regimes, periods of intense drought, and the introduction of exotic plants and animals, have contributed to the deterioration of most of the natural habitats across Australia, with a negative impact on the native wildlife, including birds. Many woodland bird species have undergone widespread declines, culminating in some local or even regional extinctions. In the mallee woodlands of south-east Australia two closely related species of whistlers (fam. Pachycephalidae) — Red-lored Whistler Pachycephala rufogularis and Gilbert’s Whistler P. inornata — have overlapping ranges, and in some areas they co-exist. These two species are morphologically and ecologically similar. However, despite the similarities, P. rufogularis has undergone greater declines in distribution and abundance than P. inornata. The ecology of these two species is poorly known, which renders adequate management impracticable. The major objectives of this thesis were to determine the key habitat requirements for the two species, to determine their habitat use, and to document the ecology and behaviour of the two species, particularly their foraging, and intra- and interspecific interactions. A sound knowledge of the ecology of the two species is needed to underpin appropriate actions for their management and conservation. Morphological features were measured from skins of P. rufogularis and P. inornata in the South Australian Museum collection, and from captured live birds, to detect if any aspect of the morphology could indicate possible niche partitioning between the two species. Also, the use of biometry as a tool for separating the sexes for P. rufogularis, for determining the species of the uncoloured immature birds and for sexing immatures, was evaluated. No morphological feature suggested niche partitioning. The biometry did not prove a very reliable tool for distinguishing sexes in adult P. rufogularis, but reliably identified the species of the uncoloured immatures. Sexing immatures based on biometrical data alone was not possible. Research was conducted in two main South Australian parks: Gluepot Reserve and Ngarkat Conservation Park. Ecological and behavioural data for P. rufogularis and P. inornata were collected by observing marked (colour-banded and radio-tagged) and unmarked individual birds of both species and sexes, over a two-year period from June 2004 to May 2006. The home ranges of P. rufogularis and P. inornata were determined by tracking the movements of birds in the landscape. Pachycephala rufogularis had much larger home ranges than P. inornata, especially when breeding. The striking differences in home range size between the two ecologically similar species might be related to differences in site fidelity. Pachycephala rufogularis at Gluepot was sedentary, being detected in the same locations throughout the year, and over several years. On the contrary, P. inornata generally showed poor site fidelity, being more mobile, and shifting home ranges between and within seasons. In the field the two species were segregated by habitat. Pachycephala rufogularis and P. inornata showed different habitat preferences, even in areas where they did not co-occur. Pachycephala rufogularis favoured low mallee with Triodia on sand dunes, while P. inornata favoured tall mallee with sparse shrub understorey in interdunes, but also other habitats, such as prickly Acacia thickets and Casuarina woodlands. However, both species used the mallee- Triodia with Callitris vegetation type. The key to coexistence in this habitat was a behavioural one, P. inornata acting as a subordinate species. Pachycephala rufogularis had strict habitat requirements, with the presence of Triodia being critical for the presence of the species. In contrast, P. inornata was more flexible in its habitat requirements, and used a broader range of vegetation types, being more of a habitat generalist. The investigation of habitat use from both a spatial and temporal perspective confirmed that both species actively selected habitat, and that the habitats they selected differed. The core areas of home ranges predominantly contained the preferred habitat for both species. In both species, core areas of home ranges of breeding individuals (where generally the nests were placed) contained preferred habitat in higher proportion than core areas of non-breeding birds. This suggests that during breeding, both species are more restricted to, and/or use more intensely the preferred habitat than when not breeding. The foraging behaviour did not differ consistently between the two species, both capturing insects mostly by snatching in canopy foliage, and also by gleaning on the vegetation, at different heights. However, the two species were already segregated by habitat. Thus the resource partitioning occurred spatially, at the macrohabitat level. In the instances when individuals of both species foraged in the same area and used the same resources, resource partitioning occurred at a temporal scale. Both species were generalists in foraging; therefore, a presumed foraging specialisation as a possible factor related to the decline of P. rufogularis was ruled out. Pachycephala rufogularis and P. inornata are unlikely to be competitors. Support for this argument came from the situation at Ngarkat, where P. inornata was absent. Despite this, P. rufogularis did not use a broader range of vegetation types in Ngarkat, as would be expected under ‘competitive release’. Instead the species maintained strict habitat requirements, specializing virtually on a single vegetation type. The rigid habitat requirements of P. rufogularis, together with its sedentary nature, render this species vulnerable to disturbances, such as wildfires. On the other hand, the apparent flexibility in habitat requirements and greater mobility may explain why P. inornata has been more successful than its sibling species. The information on habitat requirements, preference and use, and also on home ranges of P. rufogularis and P. inornata provided in this study should be included in future habitat suitability models and predictive models for these species, which will assist in their management. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374821 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009
10

Ecology and behaviour of Pachycephala rufogularis and P. inornata (Aves: Pachycephalidae) in woodlands of South Australia.

Moise, Dragos January 2009 (has links)
Since European settlement, the woodlands and associated habitats, especially in the temperate zones of Australia, have been extensively cleared and converted to arable land and pastures. Much of the remaining vegetation in the agricultural zone occurs as small isolated patches prone to disturbance and degradation. Apart from habitat loss and fragmentation, altered fire regimes, periods of intense drought, and the introduction of exotic plants and animals, have contributed to the deterioration of most of the natural habitats across Australia, with a negative impact on the native wildlife, including birds. Many woodland bird species have undergone widespread declines, culminating in some local or even regional extinctions. In the mallee woodlands of south-east Australia two closely related species of whistlers (fam. Pachycephalidae) — Red-lored Whistler Pachycephala rufogularis and Gilbert’s Whistler P. inornata — have overlapping ranges, and in some areas they co-exist. These two species are morphologically and ecologically similar. However, despite the similarities, P. rufogularis has undergone greater declines in distribution and abundance than P. inornata. The ecology of these two species is poorly known, which renders adequate management impracticable. The major objectives of this thesis were to determine the key habitat requirements for the two species, to determine their habitat use, and to document the ecology and behaviour of the two species, particularly their foraging, and intra- and interspecific interactions. A sound knowledge of the ecology of the two species is needed to underpin appropriate actions for their management and conservation. Morphological features were measured from skins of P. rufogularis and P. inornata in the South Australian Museum collection, and from captured live birds, to detect if any aspect of the morphology could indicate possible niche partitioning between the two species. Also, the use of biometry as a tool for separating the sexes for P. rufogularis, for determining the species of the uncoloured immature birds and for sexing immatures, was evaluated. No morphological feature suggested niche partitioning. The biometry did not prove a very reliable tool for distinguishing sexes in adult P. rufogularis, but reliably identified the species of the uncoloured immatures. Sexing immatures based on biometrical data alone was not possible. Research was conducted in two main South Australian parks: Gluepot Reserve and Ngarkat Conservation Park. Ecological and behavioural data for P. rufogularis and P. inornata were collected by observing marked (colour-banded and radio-tagged) and unmarked individual birds of both species and sexes, over a two-year period from June 2004 to May 2006. The home ranges of P. rufogularis and P. inornata were determined by tracking the movements of birds in the landscape. Pachycephala rufogularis had much larger home ranges than P. inornata, especially when breeding. The striking differences in home range size between the two ecologically similar species might be related to differences in site fidelity. Pachycephala rufogularis at Gluepot was sedentary, being detected in the same locations throughout the year, and over several years. On the contrary, P. inornata generally showed poor site fidelity, being more mobile, and shifting home ranges between and within seasons. In the field the two species were segregated by habitat. Pachycephala rufogularis and P. inornata showed different habitat preferences, even in areas where they did not co-occur. Pachycephala rufogularis favoured low mallee with Triodia on sand dunes, while P. inornata favoured tall mallee with sparse shrub understorey in interdunes, but also other habitats, such as prickly Acacia thickets and Casuarina woodlands. However, both species used the mallee- Triodia with Callitris vegetation type. The key to coexistence in this habitat was a behavioural one, P. inornata acting as a subordinate species. Pachycephala rufogularis had strict habitat requirements, with the presence of Triodia being critical for the presence of the species. In contrast, P. inornata was more flexible in its habitat requirements, and used a broader range of vegetation types, being more of a habitat generalist. The investigation of habitat use from both a spatial and temporal perspective confirmed that both species actively selected habitat, and that the habitats they selected differed. The core areas of home ranges predominantly contained the preferred habitat for both species. In both species, core areas of home ranges of breeding individuals (where generally the nests were placed) contained preferred habitat in higher proportion than core areas of non-breeding birds. This suggests that during breeding, both species are more restricted to, and/or use more intensely the preferred habitat than when not breeding. The foraging behaviour did not differ consistently between the two species, both capturing insects mostly by snatching in canopy foliage, and also by gleaning on the vegetation, at different heights. However, the two species were already segregated by habitat. Thus the resource partitioning occurred spatially, at the macrohabitat level. In the instances when individuals of both species foraged in the same area and used the same resources, resource partitioning occurred at a temporal scale. Both species were generalists in foraging; therefore, a presumed foraging specialisation as a possible factor related to the decline of P. rufogularis was ruled out. Pachycephala rufogularis and P. inornata are unlikely to be competitors. Support for this argument came from the situation at Ngarkat, where P. inornata was absent. Despite this, P. rufogularis did not use a broader range of vegetation types in Ngarkat, as would be expected under ‘competitive release’. Instead the species maintained strict habitat requirements, specializing virtually on a single vegetation type. The rigid habitat requirements of P. rufogularis, together with its sedentary nature, render this species vulnerable to disturbances, such as wildfires. On the other hand, the apparent flexibility in habitat requirements and greater mobility may explain why P. inornata has been more successful than its sibling species. The information on habitat requirements, preference and use, and also on home ranges of P. rufogularis and P. inornata provided in this study should be included in future habitat suitability models and predictive models for these species, which will assist in their management. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1374821 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009

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