Literatura científica selecionada sobre o tema "Rare plants – Western Australia"
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Artigos de revistas sobre o assunto "Rare plants – Western Australia"
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Miller, Ben P., David R. Symons e Matthew D. Barrett. "Persistence of rare species depends on rare events: demography, fire response and phenology of two plant species endemic to a semiarid Banded Iron Formation range". Australian Journal of Botany 67, n.º 3 (2019): 268. http://dx.doi.org/10.1071/bt18214.
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The association of rare plant species and Banded Iron Formation (BIF) ranges in semiarid Western Australia is a noted phenomenon. These ranges are also a focus of iron ore exploration and mining. Decisions and planning required for development, conservation and management resulting from this interest, often consider translocation of these threatened species. Nonetheless, little is known about the ecology of BIF-endemic species to support any such decisions. We assessed population structure, patterns of growth, mortality, recruitment, reproduction and in situ seedbank persistence for two declared rare flora species. The shrub Darwinia masonii, and sedge Lepidosperma gibsonii are endemic to an area <40 km2 on the south-western boundary of the Australian arid zone. Both species were found to be long lived and slow growing, with evidence for reliance on rare events such as fire, and high rainfall years, including, for some processes, consecutive high rainfall years for growth, reproduction and recruitment. Retrieval and germination of seed batches shows that both species’ seedbanks are long-lived, with seasonal dormancy cycling. This, together with the ability of mature plants to survive through years not supporting growth, and, for L. gibsonii, to resprout after fire, are key mechanism for persistence in this unpredictable and low rainfall environment.
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Kennedy, J., e G. Weste. "Vegetation Changes Associated With Invasion by Phytophthora cinnamomi on Monitored Sites in the Grampians, Western Australia". Australian Journal of Botany 34, n.º 3 (1986): 251. http://dx.doi.org/10.1071/bt9860251.
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The effects of invasion by Phytophthora cinnamomi were measured on sites representing the larger forest regions of the Grampians. Changes were obvious at first, with the death of more than 50% of the species including large plants such as Xanthorrhoea australis, but soon became dificult to detect as susceptible species were replaced by field-resistant graminoids. Reductions were assessed in species heterogeneity and plant density during 1976, at the onset of disease and from 1977 to 1984. Susceptible species disappeared from infested forest and no re-emergence was observed. Less-susceptible plants such as some Euca/yptus spp. declined in number, regeneration and size, due to deaths or dieback of the branches. Reductions in tree canopy and the loss of structural dominants of the understorey caused changes in the flora which are likely to persist. The survival of rare, susceptible endemic species may be endangered. On dry, steep slopes the dead plants were not replaced and the amount of bare ground increased causing erosion of the soil surface. Some graminoid species increased in abundance on level, infested sites, resulting in a different species composition but with both species heterogeneity and plant density numerically similar to the previous flora.
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Cox, Brad. "Granite Outcrops Symposium". Pacific Conservation Biology 4, n.º 3 (1998): 271. http://dx.doi.org/10.1071/pc98271a.
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Western Australia is a flat landscape. Granite outcrops are one of the few features that rise above the terrain. This makes them unique landmarks for people, and islands for plants and animals. They are highly significant in terms of their geological, biological and cultural values. They contain some of the world's oldest rocks, are an important source of water, often contain aboriginal heritage sites and are refuges for many rare and endangered flora and fauna.
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Touchell, DH, KW Dixon e B. Tan. "Cryopreservation of Shoot-Tips of Grevillea scapigera (Proteaceae): a Rare and Endangered Plant From Western Australia". Australian Journal of Botany 40, n.º 3 (1992): 305. http://dx.doi.org/10.1071/bt9920305.
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Cryopreservation of leaf, petiole, stem pieces and shoot-tips was investigated as a means for long-term maintenance of germplasm of the rare and endangered species, Grevillea scapigera A.S. George. Crypreservation was only achieved using shoot-tips or axillary buds and a slow-cooling regime with the aid of an improvised freezing device. The highest survival of thawed explants (20%) was obtained with 4-week-old in vitro shoot-tips cultured for 48 h in a prefreezing liquid culture medium supplemented with 5% dimethylsulfoxide. The pretreated shoot-tips were frozen in a liquid medium containing 10% dimethylsulfoxide cooled at a rate of 0.5°C/min to -40°C and held at this temperature for 30 min before being plunged into liquid nitrogen. Shoot-tips that survived the freeze-thaw cycle produced callus followed by shoot production 22 weeks after thawing. All shoots regenerated from thawed tissues and transferred to soil appeared phenotypically identical to untreated control shoots and plants. Rapid methods for assessing post-thaw tissue viability and explant recovery using triphenyltetrazolium chloride were tried but these methods were inadequate for determining the capacity of thawed tissues to recover from freeze damage.
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Briggs, BG, LAS Johnson e SL Krauss. "The species of Alexgeorgea, a Western Australian genus of the restionaceae". Australian Systematic Botany 3, n.º 4 (1990): 751. http://dx.doi.org/10.1071/sb9900751.
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The three species of Alexgeorgea Carlquist are revised, including A. ganopoda L. Johnson & B. Briggs, a newly described rare species of the Mt Frankland–Bow River region of the south-west of Western Australia.
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Olde, Peter. "Grevillea pieroniae Olde (Proteaceae: Grevilleoideae: Hakeinae), a rare new species in the Triloba Group from the Stirling Range, Western Australia, and a short history of the group." Telopea 23 (2020): 227–35. http://dx.doi.org/10.7751/telopea14783.
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Twenty-one Grevillea species currently comprise the Triloba Group sensu Flora of Australia, or Group 1 sensu The Grevillea Book. All species except the transcontinental species G. anethifolia R.Br. are distributed in southwest Western Australia. Grevillea pieroniae Olde, herein described, is currently treated as Grevillea sp. Stirling Range (D.J. McGillivray 3488 & A.S. George) by the Western Australian Herbarium. It has some affinity with Grevillea anethifolia through shared possession of similar truncate-conical to cylindrical pollen-presenters. Grevillea pieroniae is a rare species that is potentially threatened by Phytophthora cinnamomi, fire frequency, a drying climate, as well as grazing by feral and native herbivores, so requires careful assessment and ongoing monitoring. A short history of the Triloba Group is provided to give context to Grevillea pieroniae and as precursor to other related species soon to be recognised.
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Pierce, Nuri B., e Michael G. Simpson. "Polyaperturate pollen types and ratios of heteromorphism in the monocot genus Conostylis (Haemodoraceae)". Australian Systematic Botany 22, n.º 1 (2009): 16. http://dx.doi.org/10.1071/sb08040.
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Pollen aperture heteromorphism (variation of aperture number in pollen grains within each flower and in all plants of a taxon) is described in the diverse monocot genus Conostylis R.Br. (Haemodoraceae) and that of related genera, all endemic to Western Australia. We report results of pollen observations from 153 specimens. In Conostylis, aperture number varies greatly, with biporate, triporate, tetraporate and polyporate pollen present, features considered rare and possibly developmentally significant for monocots. Pollen aperture types and their ratios in this genus are stable and consistent within species and subspecies groupings and phylogenetically informative.
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Walker, E., M. Byrne, B. Macdonald, D. Nicolle e J. McComb. "Clonality and hybrid origin of the rare Eucalyptus bennettiae (Myrtaceae) in Western Australia". Australian Journal of Botany 57, n.º 3 (2009): 180. http://dx.doi.org/10.1071/bt08148.
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Clonality and hybrid origin influence the conservation status of rare and restricted species. Eucalyptus bennettiae Carr & Carr is a rare species known only from a few individuals that may be clonal and may have arisen through hybridisation between other co-occurring species. The hybrid status and clonality of E. bennettiae was investigated with analysis of microsatellite variation in E. bennettiae compared with its putative parents, E. lehmannii subsp. parallela, E. sporadica and E. astringens subsp. redacta, identified through morphological characteristics. Analysis of microsatellite variation revealed clonality with one individual present at each location, and additivity of alleles and no unique alleles in E. bennettiae compared with two of the putative parents, E. lehmannii subsp. parallela and E. sporadica. In addition, E. bennettiae displayed intermediacy in species relationships and measures of relatedness, and assignment tests showed mixed ancestry in relation to these species but not the third putative parent, E. astringens subsp. redacta. These findings confirm that E. bennettiae is a hybrid and evaluation of the taxon for conservation protection shows that it does not satisfy the criteria for listing as a threatened species.
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Butcher, Ryonen. "New taxa of 'leafless' Tetratheca (Elaeocarpaceae, formerly Tremandraceae) from Western Australia." Australian Systematic Botany 20, n.º 2 (2007): 139. http://dx.doi.org/10.1071/sb06015.
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The relationships among rare ‘leafless’ species of Tetratheca Sm. occurring on banded ironstone ranges near Koolyanobbing, Western Australia, and allied, unclassified, populations from Eneabba, Newdegate and the Die Hardy Range have been assessed by molecular characters. These findings, in conjunction with morphological investigations, have identified a new species and two new subspecies from within the ‘T. aphylla group’ and these are formally described here. Tetratheca nephelioides R.Butcher, is geographically restricted to the Eneabba area and has close morphological affinity to T. aphylla F.Muell. Tetratheca aphylla subsp. megacarpa R.Butcher, is restricted to the Newdegate area, some 300 km south of the only known populations of T. aphylla subsp. aphylla in the Helena and Aurora Range. Tetratheca paynterae Alford subsp. cremnobata R.Butcher is restricted to the Die Hardy Range, c. 10 km north-east of the only known population of T. paynterae subsp. paynterae at ‘Windarling’. All of these taxa are recognised as Declared Rare Flora. In the process of updating the existing key to ‘leafless’ species of Tetratheca to include these new taxa, two additional new species were identified from within collections of T. nuda Lindl. These are described here as T. angulata R.Butcher and T. applanata R.Butcher. Images and distribution maps for all taxa are provided.
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Li, C. X., Hua Li, K. Sivasithamparam, T. D. Fu, Y. C. Li, S. Y. Liu e M. J. Barbetti. "Expression of field resistance under Western Australian conditions to Sclerotinia sclerotiorum in Chinese and Australian Brassica napus and Brassica juncea germplasm and its relation with stem diameter". Australian Journal of Agricultural Research 57, n.º 10 (2006): 1131. http://dx.doi.org/10.1071/ar06066.
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Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, has become one of the most serious disease problems in oilseed rape-growing areas in Australia. Sources of resistance to this disease have been sought worldwide. In this study, germplasm comprising 42 Brassica napus and 12 Brassica juncea accessions from China and Australia, was screened for resistance to Sclerotinia stem rot under Western Australian field conditions. Resistance was confirmed in some germplasm from China and new sources of resistance were identified in germplasm from Australia. Furthermore, our study found that the severity of stem lesions was related to stem diameter and percentage of the host plants that were dead. It was evident that both stem lesion length and percentage of plant death were at the lowest level when the stem diameter was approximately 10 mm. Smaller or greater stem diameter resulted both in increased stem lesion length and plant death. Stem diameter may be a useful parameter in breeding cultivars of oilseed Brassicas with Sclerotinia resistance.
Teses / dissertações sobre o assunto "Rare plants – Western Australia"
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Swarts, Nigel. "Integrated conservation of the rare and endangered terrestrial orchid Caladenia huegelii H.G. Reichb". University of Western Australia. School of Earth and Geographical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0044.
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The Orchidaceae is characterized by a remarkably diverse range of life forms and some of the most highly specialized interactions with soil fungi and insect pollinators found in the flowering plants. Many species are rare or threatened with extinction either directly through loss of habitat or over-collection or, indirectly through debilitation or loss of mycorrhizal association or pollinator capacity. Australian temperate terrestrial orchids represent one of the most threatened groups in the Australian flora with many taxa clinging to existence in urban and rural bushland remnants, road verges and unprotected bushland. The aim of this study is to research and develop integrated conservation based on critical aspects of terrestrial orchid biology and ecology, towards the recovery of the rare and endangered Western Australian terrestrial orchid Caladenia huegelii. This study identified key aspects involved in an integrated conservation approach and research focused on conservation genetics, mycorrhizal interactions and in situ and ex situ conservation strategies for this species. Using polymorphic microsatellite molecular markers, high levels of genetic diversity were found within remnant populations of C. huegelii, while weak differentiation was observed among populations over the species geographic range. These results indicate historic genetic exchange between C. huegelii populations, a possible consequence of the sexually deceptive pollination strategy and the capacity for widespread seed dispersal. Symbiotic germination studies revealed compatibility barriers to C. huegelii germination with the orchid possessing a highly specific orchid-mycorrhizal association relative to common sympatric congeners. These results were reflected in a phylogenetic analysis of DNA sequences, revealing C. huegelii associates with only one endophyte species within the fungal family Sebacinaceae across its geographic range. Large scale in situ seed baiting demonstrated that endophytes compatible with C. huegelii were limited in distribution relative to common and widespread orchid species, a feature for C. huegelii that may be a major contributing factor in limiting the distributional range of the species. Detailed, within site seed baiting methods identified hotspots for mycorrhizal fungus compatible with C. huegelii that were unoccupied by the orchid. These mycorrhizal hotspots where used to investigate the effect of endophyte presence on survival of transplanted mature plants and seedling outplants. The in situ survival of glasshouse propagated seedlings was further optimized by incubating seedlings in growth containers before transfer to soil and outplanting seedlings in their second growing season. The findings of this study will substantially advance the recovery of C. huegelii and provide benchmark knowledge for similar projects with other rare and threatened terrestrial orchid species.
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Williams, Aleida Helen. "An ecophysiological comparison of rare ironstone endemics and their common congeners". University of Western Australia. School of Plant Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0241.
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[Truncated abstract] In south-western Australia a rare plant community occurs on shallow soils overlaying massive ironstone rock. These 'ironstone communities' are open shrublands, which are subject to extremes in drought and solar radiation and support many rare and endemic species. The restricted distribution of many of these species may be related to their high degree of specialisation to this harsh habitat and their inability to respond plastically to different environmental conditions. Indeed, earlier work has shown that ironstone Hakea species (Proteaceae) have a specialist root-system morphology investing mainly in deep roots, thereby increasing their chance of accessing cracks in the rock surface and obtaining water before the onset of summer drought. In this thesis I further examine aspects of specialisation and its possible consequences for species rarity using two ironstone Hakea species and comparing them with two of their widely distributed congeners. In the first experiment (Chapter 2) I explore inherent drought tolerance, independent of root-system morphology, as a further specialisation to the ironstone environment. All species were grown in sand in pots in a glasshouse for 7 months and then droughted for 5 weeks. There was no evidence that the ironstone species had a greater inherent drought tolerance than their common congeners. During drought all species maintained leaf water content of mature leaves by reducing stomatal conductance and osmotically adjusting, though ironstone species tended to OA (osmotic adjustment) more than common species. ... This suboptimal investment of resources may result in a lower competitive ability in shadier environments, and thus could partially explain their restricted distribution. In Chapter 4, I investigated the plasticity of root traits in response to levels of phosphorus supply. South-western Australian soils are phosphorus impoverished and phosphorus is well known to elicit plastic responses in root allocation and architecture. Ironstone species showed less plasticity in total root length, producing similar root length across P treatments, while common species showed an increase in root length with increasing [P]. Other root characteristics were similarly plastic in response to P treatment between species. However, when supplied with increasing [P], ironstone species invested an increasing proportion of roots in the bottom of pots while common species invested more in the top. This differential response in root allocation in response to P may reflect a fundamental trade-off between nutrient and water acquisition, with the ironstone species mainly foraging for water and investing in deeper roots, while the common species invest more in superficial roots to obtain nutrients. In conclusion, the rarity and restricted distribution of the ironstone Hakea species may be related to their specialist root-system morphology as well as a lowered phenotypic plasticity of functional traits. A reduction in plasticity may reduce their competitive ability outside their ironstone habitats, and thus contribute to the restricted distribution of these species. This may also be the case for other rock-outcrop endemics and more generally, for other rare plant species restricted to particular habitats where a lowered phenotypic plasticity in traits relevant to their particular habitat may contribute to their restricted distribution.
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Bougoure, Jeremy J. "The role of mycorrhizal fungi in nutrient supply and habitat specificity of the rare mycoheterotrophic underground orchid, Rhizanthella gardneri". University of Western Australia. School of Plant Biology, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0076.
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Rhizanthella gardneri (Rogers) is a critically endangered orchid restricted to two isolated regions of south-western Australia. Rhizanthella gardneri is an entirely subterranean mycoheterotrophic species that purportedly forms a tripartite relationship with a mycorrhizal fungus (Ceratobasidiales) that links with an autotrophic shrub of the Melaleuca uncinata complex to acquire nutrients. Whether the rarity of R. gardneri is intrinsic is overshadowed by the recent effect of extrinsic factors that means R. gardneri requires some form of conservation and may also be a viable candidate for restoration. To create an integrated conservation strategy for R. gardneri, reasons for its decline and knowledge of its biological and ecological functioning must be elucidated. This thesis focuses on three key questions; 1) what are the habitat requirements and limitations to R. gardneri survival; 2) what is the identity and specificity of the fungus R. gardneri forms mycorrhizas with; and 3) does R. gardneri form a nutrient-sharing tripartite relationship with a mycorrhizal fungus and autotrophic shrub. Key climate, soil and vegetation characteristics of known R. gardneri habitats were quantified to provide baseline data for monitoring known R. gardneri populations, to better understand how R. gardneri interacts with its habitat, and to identify possible new sites for R. gardneri introduction. Habitats of the two known R. gardneri populations differed considerably in soil chemistry, Melaleuca structure and Melaleuca productivity. Individual sites within populations were relatively similar in all attributes measured while overall Northern and Southern habitats were distinct from each other. These results suggest that R. gardneri can tolerate a range of conditions and may be more widespread than previously thought, given that there are extensive areas of Melaleuca thickets with similar habitat characteristics across south-western Australia. The fungus forming mycorrhizas with R. gardneri was identified, using nuclear ribosomal DNA sequences, as a Rhizoctonia-type fungus within the Ceratobasidiales. All fungi isolated from R. gardneri individuals representative of its currently known distribution were genetically similar, suggesting R. gardneri is highly dependent on this specific fungal species. Given that R. gardneri appears to exclusively associate with a specific fungal species, species-specific molecular primers were designed and used to analyse the fungis presence in known and potential R. gardneri habitats. These results 6 suggest that the fungus exists beyond the known R. gardneri habitats and gives hope to finding new populations.
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Sutcliffe, Karen. "The conservation status of aquatic insects in South-Western Australia /". Access via Murdoch University Digital Theses Project, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040430.153605.
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Loo, Christopher. "The ecology of naturalised silvergrass (Vulpia) populations in south-western Australia". University of Western Australia. School of Plant Biology, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0093.
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[Truncated abstract] Annual grasses have colonised a diverse range of environments in southern Australia. The “Silvergrasses” of the genus Vulpia are excellent examples being widely distributed, are prevalent weeds of agriculture and have had a long history to naturalise on the continent. Research was undertaken on Vulpia populations to identify if naturalising species have reproductive traits that provide propagules with the best chances of success. Furthermore, research aimed at investigating if these traits vary between species and their populations and how this variability related to the environment. A herbarium and field study was undertaken to establish what Vulpia species occur in SW Australia and to investigate environmental factors affecting their distribution. 169 herbaria specimens was examined and a botanical field survey of 189 sites was carried out in September 1998. Four species occur in the region: V. fasciculata, V. muralis, V. bromoides and two variants of V. myuros (V. myuros var. megalura and V. myuros var. myuros). V. bromoides and V. myuros were introduced early into the region while V. fasciculata and V. muralis more recently. It is plausible that Vulpia invaded the region via early seaport settlements and was spread by agricultural expansion. 96% of field sites contained V. myuros var. myuros, 79% V. myuros var. megalura, 50% V. bromoides, 6% V. fasciculata and 6% contained V. muralis. 90% of sites contained a mix of species and 9% of sites contained pure species stands. V. myuros var. myuros is the most widespread species and dominant form of V. myuros. It is found from high rainfall regions through to arid locations occurring on mostly light textured low fertility soils. V. muralis and V. fasciculata occur infrequently with the former widely dispersed and the later occurring predominantly on sands. V. bromoides occurs extensively in high rainfall regions but rarely extends to locations receiving less than 400-450mm annual rainfall and northward above 30°00’ latitude. It is predominantly on light to loamy textured soils that are fertile and acid. The most common species V. myuros and V. bromoides often coexist within sites but the dominance of one over the other is strongly correlated with growing season length and false break frequency. V. bromoides is positively correlated to growing season length and V. myuros is negatively related. The distribution of Vulpia species is strongly influenced by climate and soils. Variability in distribution is a reflection of the ecological differentiation between species to colonise different environments
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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.
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[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.
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Nuruzzaman, Mohammad. "Phosphorus benefits of white lupin, field pea and faba bean to wheat production in Western Australian soils". University of Western Australia. School of Plant Biology, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0094.
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[Truncated abstract] Soils of Western Australian cropping regions are very low in phosphorous. White lupin, chickpea, and faba bean are being increasingly used in rotations with wheat on these soils. Yield of wheat after a legume crop is frequently higher than its yield after wheat. It has been reported that in addition to nitrogen, legumes can also contribute to improve the availability of phosphorous for the subsequent crops. This PhD research project aimed at optimising the economic returns of wheat-legume rotations through more efficient use of P fertiliser in the legume phase as well as enhanced availability of soil P in the subsequent wheat phase
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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.
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Riffkin, Penelope A., of Western Sydney Hawkesbury University e Faculty of Science and Technology. "An assessment of white clover nitrogen fixation in grazed dairy pastures of south-western Victoria". THESIS_FST_xxx_Riffkin_P.xml, 1999. http://handle.uws.edu.au:8081/1959.7/31.
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Australia is amongst the more efficient milk producers in the world.Milk production in the region of south-western Victoria relies mainly on rainfed white clover/perennial ryegrass pastures.As the demand for efficient and competitive milk production increases, the value of N2 fixation must be maximised. The objective of this thesis was to assess N2 fixation in grazed dairy pastures in south-western Victoria. Several tests and experiments were conducted and results noted. Studies revealed low white clover yields to be the major factor limiting N2 fixation in the region. For N2 fixation to have a significant impact on pasture quality and production, problems associated with legume persistence need to be addressed. Strategies may include the breeding of white clover cultivars with greater tolerance to water stress, improved winter production and increased competitiveness with companion species. Alternatively, the introduction of different legume species, better suited to the environment, may be appropriate. Where N2 fixation is unlikely to satisfy N demands, it may be necessary to introduce the strategic use of supplementary feeds or nitrogenous fertilisers. However, this would need to be carefully considered to ensure high input costs did not jeopardise the competitive advantage of low input pasture-based systemsMasters Thesis
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Underwood, Jim. "Routine and rare genetic connections in corals off northwest Australia and the implications for conservation". University of Western Australia. School of Animal Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0158.
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[Truncated abstract] The extent to which marine populations are connected by larval dispersal is crucial to their distribution, maintenance and diversity. Thus, for the effective conservation of threatened systems such as coral reefs, understanding patterns of connectivity is essential. However, the biophysical mechanisms that retain or disperse larvae within and among populations are poorly understood. Though the open ocean environment provides the opportunity for long-distance dispersal, if this potential is only rarely realised, recruits produced from afar are unlikely to contribute to the local-scale demography of populations over ecological time frames, but will limit broad-scale genetic diversification over evolutionary time. This thesis explores the extent of genetic and demographic connectivity of two species of reef-building corals over a range of spatial scales among the discontinuous reef systems of northwest Australia. ... Putative source and sink dynamics were not random, but were associated with levels of disturbance and recovery from a recent and catastrophic coral bleaching. When S. hystrix samples from another two offshore systems were included in the analysis, large differences among systems showed that gene flow over hundreds of kilometres is rare over microevolutionary time scales that account for connections over multiple generations. Levels of subdivision over the same spatial scales were markedly lower in the acroporid coral, Acropora tenuis, than in S. hystrix. These results are congruent with expectations based on reproductive mode; in contrast to S. hystrix, which releases brooded larvae that are competent to settle immediately, A. tenuis broadcasts its gametes, and after external fertilisation, the larvae need to develop for several days before they are competent to settle. Despite the differences in levels of broad-scale subdivision, in both species significant differentiation was detected between reefs within systems (>10 km), and between sites within some reefs (< 10 km). These results indicate not only that dispersal between reefs and even some reef patches is restricted, but also that hydrodynamics influence retention of brooded and spawned larvae in similar ways. Further analysis of A. tenuis populations from two coastal systems detected significant differences in genetic diversity among the four major systems of northwest Australia. Additionally, genetic divergence between the coastal and offshore zones was greater than expected by the geographic separation of systems, indicating that connectivity between these zones via transport of A. tenuis larvae on oceanic currents occurs rarely even over microevolutionary time scales. This study has two primary implications for conservation. First, since coastal and offshore reefs of northwest Australia appear to be discrete genetic entities, they have independent evolutionary potential to adapt to local conditions and environmental change. Second, systems, reefs and some reef patches of northwest Australia are demographically independent units. Therefore, designs of coral reserve networks should consider routine dispersal distances of kilometres to a few tens of kilometres.
Livros sobre o assunto "Rare plants – Western Australia"
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Napier, Anna. Survey of rare and poorly known eucalypts of Western Australia. Wanneroo, W.A: Western Australian Wildlife Research Centre, 1988.
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Burbidge, Andrew A. Threatened animals of Western Australia. Kensington, W.A: Dept. of Conservation and Land Management, 2004.
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Mitchell, A. A. Arid shrubland plants of Western Australia. 2a ed. Nedlands, W.A: University of Western Australia Press in association with the Dept. of Agriculture, Western Australia, 1994.
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Mitchell, A. A. Arid shrubland plants of Western Australia. Nedlands, W.A: University of Western Australia Press with the Western Australian Dept. of Agriculture, 1988.
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Dittrich, Thomas, Thomas Seifert, Bernhard Schulz, Steffen Hagemann, Axel Gerdes e Jörg Pfänder. Archean Rare-Metal Pegmatites in Zimbabwe and Western Australia. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-10943-1.
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Census of the vascular plants of Western Australia. 2a ed. Perth: Western Australian Herbarium, Dept. of Agriculture, 1985.
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Petheram, R. J. Plants of the Kimberley region of Western Australia. Crawley, W.A: University of Western Australia Press, 2003.
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J, Dundas Patricia, ed. The bushland plants of Kings Park, Western Australia. [Perth, W. Australia: s.n.], 1988.
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Johnstone, R. E. Mangroves and mangrove birds of Western Australia. Perth, W.A: Western Australian Museum, 1990.
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Wagner, David H., 1945- author e United States. Bureau of Land Management. Oregon State Office, eds. Guide for the identification of rare, threatened or sensitive bryophytes in the range of the northern spotted owl, western Washington, western Oregon, and northwestern California. Portland, Or: U.S. Department of the Interior, Bureau of Land Management, Oregon-Washington State Office, 1996.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Rare plants – Western Australia"
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Ruiz-Avila, R. J., e V. V. Klemm. "Management of Hydrocotyle ranunculoides L.f., an aquatic invasive weed of urban waterways in Western Australia". In Management and Ecology of Freshwater Plants, 187–90. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-011-5782-7_29.
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Osborne, J. M., J. E. D. Fox e S. Mercer. "Germination response under elevated salinities of six semi-arid bluebush species (Western Australia)". In Towards the rational use of high salinity tolerant plants, 323–38. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1858-3_35.
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Cox, Morgan A., Aaron J. Cavosie, Michael Poelchau, Thomas Kenkmann, Phil A. Bland e Katarina Miljković. "Shock deformation microstructures in xenotime from the Spider impact structure, Western Australia". In Large Meteorite Impacts and Planetary Evolution VI. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.2550(19).
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ABSTRACT The rare earth element–bearing phosphate xenotime (YPO4) is isostructural with zircon, and therefore it has been predicted that xenotime forms similar shock deformation microstructures. However, systematic characterization of the range of micro structures that form in xenotime has not been conducted previously. Here, we report a study of 25 xenotime grains from 10 shatter cones in silicified sandstone from the Spider impact structure in Western Australia. We used electron backscatter diffrac tion (EBSD) in order to characterize deformation and microstructures within xenotime. The studied grains preserve multiple sets of planar fractures, lamellar {112} deformation twins, high-angle planar deformation bands (PDBs), partially recrystallized domains, and pre-impact polycrystalline grains. Pressure estimates from micro structures in coexisting minerals (quartz and zircon) allow some broad empirical constraints on formation conditions of ~10–20 GPa to be placed on the observed microstructures in xenotime; at present, more precise formation conditions are unavailable due to the absence of experimental constraints. Results from this study indicate that the most promising microstructures in xenotime for recording shock deformation are lamellar {112} twins, polycrystalline grains, and high-angle PDBs. The {112} deformation twins in xenotime are likely to be a diagnostic shock indicator, but they may require a different stress regime than that of {112} twinning in zircon. Likewise, polycrystalline grains are suggestive of impact-induced thermal recrystallization; however, in contrast to zircon, the impact-generated polycrystalline xenotime grains here appear to have formed in the solid state, and, in some cases, they may be difficult to distinguish from diagenetic xenotime with broadly similar textures.
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Blondel, Jacques, e Frédéric Médail. "Biodiversity and Conservation". In The Physical Geography of the Mediterranean. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780199268030.003.0039.
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The biodiversity of Mediterranean-climate ecosystems is of particular interest and concern, not only because all five of these regions (the Mediterranean basin, California, central Chile, Cape Province of South Africa, western and southern parts of Australia) are among the thirty-four hotspots of species diversity in the world (Mittermeier et al. 2004), but they are also hotspots of human population density and growth (Cincotta and Engelman 2000). This relationship is not surprising because there is often a correlation between the biodiversity of natural systems and the abundance of people (Araùjo 2003; Médail and Diadema 2006) and this, inevitably, raises conservation problems. Within the larger hotspot of the Mediterranean basin as a whole, ten regional hotspots have been identified. They cover about 22 per cent of the basin’s total area and harbour about 44 per cent of Mediterranean endemic plant species (Médail and Quézel 1997, 1999), as well as a large number of rare and endemic animals (Blondel and Aronson 1999). A key feature of these Mediterranean hotspots as a whole is their extraordinarily high topographic diversity with many mountainous and insular areas. Not surprisingly this results in high endemism rates and they contain more than 10 per cent of the total plant richness (see the recent synthesis of Thompson 2005). However, of all the mediterranean-type regions in the world, the Mediterranean basin harbours the lowest percentage (c.5%) of natural vegetation considered to be in ‘pristine condition’ (Médail and Myers 2004; Chapter 7). With an average of as many as 111 people per km2, one may expect a significant decline in biological diversity in the Mediterranean basin—a region that has been managed, modified, and, in places, heavily degraded by humans for millennia (Thirgood 1981; Braudel 1986; McNeill 1992; Blondel and Aronson 1999; Chapter 9). There are two contrasting theories that consider the relationships between humans and ecosystems in the Mediterranean (Blondel 2006, 2008). The first one is the ‘Ruined Landscape or Lost Eden’ theory, first advocated by painters, poets, and historians in the sixteenth and seventeenth centuries, and later by a large number of ecologists.
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Luker, Vicki. "The Half-Caste in Australia, New Zealand, and Western Samoa between the Wars: different problem, different places?" In Foreign Bodies: Oceania and the Science of Race 1750–1940. ANU Press, 2008. http://dx.doi.org/10.22459/fb.11.2008.09.
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Alexander, Earl B., Roger G. Coleman, Todd Keeler-Wolfe e Susan P. Harrison. "Serpentine Land Use and Health Concerns". In Serpentine Geoecology of Western North America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195165081.003.0030.
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Soils developed from serpentine (ultramafic) substrates are noted for their meager and strange biomass. The chemical infertility is the main controlling factor in the development of plants in serpentine soils (Proctor and Woodell 1975, Kruckeberg 1984, Brooks 1987). Botanists have recognized the unusual nature of the endemic plants and this has led to preserving serpentine tracts that contain rare plant species. The evolution of plant species that are restricted to serpentine has produced remarkable adaptations to survival on serpentine substrates. Kruckeberg (1984) pointed out that the long-term habitat attrition on these rare natural serpentine ecosystems requires conservation initiatives to insure their preservation. In California, private and public land managers are required to develop environmental impact studies before disturbing tracts containing serpentine bedrock and its overlying soils (Clinkenbeard et al. 2003). The U.S. Fish and Wildlife Service (USFWS 1998) carried out a recovery plan for 28 species of plants and animals that occur exclusively or primarily on serpentine soils and grasslands in the San Francisco Bay area. The strategy was to provide detailed actions needed to achieve self-sustaining populations of endangered species so they will no longer require protection under the Endangered Species Act. Serpentine land tracts within metropolitan areas have come under closer regulation, as there is concern of releasing naturally occurring asbestos during construction disturbances. Typical examples of disturbance would be construction sites, new road construction, and quarry excavation. Of particular concern are the large amounts of dust produced in quarry operations or unpaved gravel roads consisting of crushed serpentine rock. The dust from such sites may contain airborne asbestos fibers released from the serpentine. This asbestos-bearing dust may pose a toxic threat to the construction workers and to later occupants of homes, schools, and office buildings occupying serpentine tracts. Asbestos is the blanket term for a group of naturally occurring silicate minerals that can be separated into fibers. The fibers are strong, durable, and resistant to extreme heat. Because of these qualities, asbestos has been used in industrial, maritime, automotive, scientific, and building products.
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Harding, Andrew, e Jean Palutikof. "The Climate System". In The Physical Geography of the Mediterranean. Oxford University Press, 2009. http://dx.doi.org/10.1093/oso/9780199268030.003.0013.
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The Mediterranean region has a highly distinctive climate due to its position between 30 and 45°N to the west of the Euro-Asian landmass. With respect to the global atmospheric system, it lies between subtropical high pressure systems to the south, and westerly wind belts to the north. In winter, as these systems move equatorward, the Mediterranean basin lies under the influence of, and is exposed to, the westerly wind belt, and the weather is wet and mild. In the summer, as shown in Figure 3.1, the Mediterranean lies under subtropical high pressure systems, and conditions are hot and dry, with an absolute drought that may persist for more than two or three months in drier regions. Climates such as this are relatively rare, and the Mediterranean shares its winter wet/summer dry conditions with locations as distant as central Chile, the southern tip of Cape Province in South Africa, southwest Australia in the Southern Hemisphere, and central California in the Northern Hemisphere. All have in common their mid-latitude position, between subtropical high pressure systems and westerly wind belts. They all lie on the westerly side of continents so that, in winter, when the westerly wind belts dominate over their locations, they are exposed to rain-bearing winds. In the Köppen classification (Köppen 1936), these climates are known as Mediterranean (Type Cs, which is subdivided in turn into maritime Csb and continental Csa). The influence of the Mediterranean Sea means that the Mediterranean-type climate of the region extends much further into the continental landmass than elsewhere, and is not restricted to a narrow ocean-facing strip. Nevertheless, within the Mediterranean region climate is modified by position and topographic influences can be important. The proximity of the western Mediterranean to the Atlantic Ocean gives its climate a maritime flavour, with higher rainfall and milder temperatures throughout the year. The eastern Mediterranean lies closer to the truly continental influences of central Europe and Asia. Its climate is drier, and temperatures are hotter in summer and colder in winter than in the west. Annual rainfall is typically around 750 mm in Rome, but only around 400 mm in Athens.
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Barker, Graeme. "Understanding Foragers". In The Agricultural Revolution in Prehistory. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780199281091.003.0007.
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Hunter-gatherer or forager societies, as the names imply, have been defined first and foremost by their mode of subsistence: ‘hunting of wild animals, gathering of wild plants, and fishing, with no domestication of plants, and no domesticated animals except the dog’ (Lee and Daly, 1999: 3). Another recent survey develops this defining characteristic in the following terms: ‘the absence of direct human control over the reproduction of exploited species, and little or no control over other aspects of population ecology such as the behaviour and distribution of food resources. In essence, hunter-gatherers exercise no deliberate alteration of the gene pool of exploited resources’ (Panter-Brick et al., 2001b: 2, their italics). In addition to this primary characteristic of ‘not being farmers’, there are or have been two other very common features amongst recent and contemporary forager societies, as Lee and DeVore (1968b: 11) commented in their opening essay to the seminal Man the Hunter volume: ‘(1) they live in small groups, and (2) they move around a lot’. At the end of the Pleistocene, forager societies peopled most regions of the world, at most latitudes. By the middle of the second millennium ad, foragers still occupied a third of the globe including all of Australia and most of North America, and large tracts of South America, Africa, North, and North-East Asia. Yet in recent centuries foragers have ‘retreated precipitously in the face of the steamroller ofmodernity’ (Lee and Daly, 1999: 1), occupying only those areas where farmers simply cannot go, or where farming is so marginal as to be uneconomic (Fig. 2.1). Many societies frequently cited in archaeological textbooks as examples of forager societies today, like the !Kung-San of the Kalahari, in fact also practise cultivation or herding on a small scale, and others depend heavily on trade with neighbouring farmers for staple foods. It is extremely difficult to translate foragers’ behaviour as recorded today or in the recent past into theories of general applicability to the world’s prehistoric foraging population prior to farming. The task is all the more complicated by the remoteness of the everyday lives of foragers (present and past) from western Europeans, a remoteness that has given rise to two enduring currents in European philosophical thinking about such societies: that they are alien savages on the one hand, or innocents close to the state of nature on the other (Barnard, 1999).
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Orme, Antony R. "The Tectonic Framework of South America". In The Physical Geography of South America. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195313413.003.0008.
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Tectonism is the science of Earth movements and the rocks and structures involved therein. These movements build the structural framework that supports the stage on which surface processes, plants, animals and, most recently, people pursue their various roles under an atmospheric canopy. An appreciation of this tectonic framework is thus a desirable starting point for understanding the physical geography of South America, from its roots in the distant past through the many and varied changes that have shaped the landscapes visible today. Tectonic science recognizes that Earth’s lithosphere comprises rocks of varying density that mobilize as relatively rigid plates, some continental in origin, some oceanic, and some, like the South American plate, amalgams of both continental and oceanic rocks. These plates shift in response to deep-seated forces, such as convection in the upper mantle, and crustal forces involving push and pull mechanics between plates. Crustal motions, augmented by magmatism, erosion, and deposition, in turn generate complex three-dimensional patterns. Although plate architecture has changed over geologic time, Earth’s lithosphere is presently organized into seven major plates, including the South American plate, and numerous smaller plates and slivers. The crustal mobility implicit in plate tectonics often focuses more attention on plate margins than on plate interiors. In this respect, it is usual to distinguish between passive margins, where plates are rifting and diverging, and active margins, where plates are either converging or shearing laterally alongside one another. At passive or divergent margins, such as the present eastern margin of the South American plate, severe crustal deformation is rare but crustal flexuring (epeirogeny), faulting, and volcanism occur as plates shift away from spreading centers, such as the Mid-Atlantic Ridge, where new crust is forming. Despite this lack of severe postrift deformation, however, passive margins commonly involve the separation of highly deformed rocks and structures that were involved in the earlier assembly of continental plates, as shown by similar structural legacies in the facing continental margins of eastern South America and western Africa. At active convergent margins, mountain building (orogeny) commonly results from subduction of oceanic plates, collision of continental plates, or accretion of displaced terranes.
Trabalhos de conferências sobre o assunto "Rare plants – Western Australia"
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Wuchter, C., L. Mucina, S. Stanley, A. Sessions e K. Grice. "Environmental Drivers Shaping Physiological Flexibility of Plants in Saline Habitats from Shark Bay, Western Australia". In 29th International Meeting on Organic Geochemistry. European Association of Geoscientists & Engineers, 2019. http://dx.doi.org/10.3997/2214-4609.201903000.
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Peterseim, Juergen H., Amir Tadros, Udo Hellwig e Stuart White. "Integrated Solar Combined Cycle Plants Using Solar Towers With Thermal Storage to Increase Plant Performance". In ASME 2013 Power Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/power2013-98121.
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In Australia both natural gas and an excellent solar irradiance are abundant energy sources and its combination is one option to implement concentrating solar power (CSP) systems in Australia’s traditionally low cost electricity market. The recently introduced carbon pricing mechanism in Australia is likely to steer investment towards combined cycle gas turbine (CCGT) plants. This will also lead to further plants being built in high solar irradiance areas where CSP could provide valuable peak capacity. Hybridisation would enable more competitive power generation than standalone CSP systems as hybrid plants share equipment, such as steam turbine and condenser, therewith lowering the specific investment. This paper investigates the novel hybridization of CCGT and solar tower systems to increase the efficiency of integrated solar combined cycle (ISCC). Currently, all ISCC plants use parabolic trough systems with thermal oil as this technology is most mature. However, increases in plant efficiency, simpler solar tower integration as well as further synergies of solar tower ISCC systems, such as joint use of tower as CCGT stack, are likely to enhance the economic viability of new ISCC plants. In addition to a technical concept description this paper outlines the ideal sites for ISCC plants in Australia and presents a 200MWe ISCC case study with 3h molten salt thermal storage for the conversion of the Port Hedland open cycle gas turbine (OCGT) facility in Western Australia into a solar tower ISCC plant.
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Coulon, Vincent, Sébastien Christophe, Laurence Grammosenis, Luc Guinard e Hervé Cordier. "Protection of Nuclear Power Plants Against Natural Hazards: Protection Principles Against Rare and Severe Natural Hazards for New Nuclear Power Plants". In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16185.
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Abstract The field of protection against external natural hazards (eg.: rare and severe hazards) has regularly evolved since the design of the first NPPs (Nuclear Power Plants) to take into account the experience feedback. Following the Fukushima Daiichi accident in March 2011, consideration of rare and severe natural hazards has considerably increased in the international context. Taking rare and severe natural hazards into account is a challenge for operating nuclear reactors and a major issue for the design of new nuclear reactors. In Europe, considering lessons learnt from the Fukushima Daiichi accident, European safety authorities released new reference levels in the framework of WENRA 2013 (Western European Nuclear Regulators Association) standards for new reactors [1] to address external hazards more severe than the design basis hazards. Considering this input, the French and UK nuclear regulators have released specific guidelines (Guide No. 22 related to design of new pressurized water reactors [2] for France and ONR Safety Assessment Principles SAPs [3] for the UK) to describe how to apply those principles in their national context. To comply with those different guidelines, EDF has developed different approaches, called Beyond Design Basis (BDB) approaches, related to rare and severe natural hazards issue in the French and UK context for nuclear new build projects. Those two approaches are presented in the present technical paper with the following structure: - safety objectives; - hazards to consider; - SSCs (Structures, Systems, and Components) required to meet safety objectives; - study rules and assumptions; - analysis of deterministic or probabilistic nature, thereby including the following: ○ analysis of available margins (margin between 10−4 per annum exceedance frequency of hazard site level or equivalent level of safety and the chosen Design Basis Hazard level also called ‘inherent margin’); ○ Fukushima Daiichi accident Operating Experience feedback; ○ probabilistic safety analyses. This technical paper highlights common characteristics and differences between the two approaches considering the French and UK regulatory contexts.
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Blinderman, Michael S., e Bernard Anderson. "Underground Coal Gasification for Power Generation: High Efficiency and CO2-Emissions". In ASME 2004 Power Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/power2004-52036.
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Underground Coal Gasification (UCG) is a gasification process carried out in non-mined coal seams using injection and production wells drilled from the surface, enabling the coal to be converted into product gas. The UCG process practiced by Ergo Exergy is called Exergy UCG or εUCG. εUCG was applied in the Chinchilla UCG-IGCC Project in Australia. The IGCC project in Chinchilla, Australia has been under development since July 1999. The project involves construction of the underground gasifier and demonstration of UCG technology, and installation of the power island. Since December 1999 the plant has been making gas continuously, and its maximum capacity is 80,000 Nm3/h. Approximately 32,000 tonnes of coal have been gasified, and 100% availability of gas production has been demonstrated over 30 months of operation. The UCG operation in Chinchilla is the largest and the longest to date in the Western world. The εUCG facility at Chinchilla has used air injection, and produced a low BTU gas of about 5.0 MJ/m3 at a pressure of 10 barg (145 psig) and temperature of 300° C (570° F). It included 9 process wells that have been producing gas manufactured from a 10 m thick coal seam at the depth of about 140 m. The process displayed high efficiency and consistency in providing gas of stable quality and quantity. The results of operations in Chinchilla to date have demonstrated that εUCG can consistently provide gas of stable quantity and quality for IGCC power projects at very low cost enabling the UCG-IGCC plant to compete with coal-fired power stations. This has been done in full compliance with rigorous environmental regulations. A wide range of gas turbines can be used for UCG-IGCC applications. The turbines using UCG gas will demonstrate an increase in output by up to 25% compared to natural gas. The power block efficiency reaches 55%, while the overall efficiency of the UCG-IGCC process can reach 43%. A UCG-IGCC power plant will generate electricity at a much lower cost than existing or proposed fossil fuel power plants. CO2 emissions of the plant can be reduced to a level 55% less than those of a supercritical coal-fired plant and 25% less than the emissions of NG CC.
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He, Suoying, Guanhong Zhang, Yi Xu e Fengzhong Sun. "The Inlet Air Pre-Cooling of Natural Draft Dry Cooling Towers-Wetted Medium Issue". In ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3235.
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Dry cooling towers are an alternative cooling method when large quantities of water are not available. Examples of the proposed applications are the enhanced geothermal and concentrated solar thermal (CST) power plants in arid or semi-arid areas, like south-western United States, Australia, western Asia, north-western China and the rest of the world. Natural draft dry cooling towers (NDDCTs) have received widespread attention because they do not consume water, have low maintenance requirements and cause small parasitic losses. Unfortunately, the performance of a NDDCT is severely reduced when the ambient air is hot, which is because the NDDCT is driven by buoyancy effect and relies solely on air to cool the working fluid. The present study introduces inlet air pre-cooling using wetted media, which combines dry and wet cooling. The wet cooling system only operates at high ambient temperatures to assist dry cooling. However, wetted-medium cooling introduces extra pressure drop which reduces the air flow passing through the NDDCT and thus impairs the tower heat rejection. To this end, this paper takes into account the trade-off between the wetted-medium cooling and the extra pressure drop. Early studies find that the performance of NDDCTs can be improved by wetted-medium evaporative pre-cooling when the ambient air is hot and dry. However, the pre-cooling enhancement is seasonal-dependent and is significantly affected by wetted media. To further investigate the effect of wetted medium type on pre-cooling performance, the current study simulates a pre-cooled NDDCT using five selected wetted media (i.e., three film and two trickle media) based on a self-developed MATLAB program. The innovations of the current study are: (1) two typical types of wetted media with the potential of evaporative pre-cooling are comparatively studied to give suggestions for future pre-cooling design; (2) the characteristics of wetted media suitable for evaporative pre-cooling of NDDCTs are summarized. The simulation finds that the media with high or low cooling efficiencies and pressure drops are not promising while those media with middle cooling efficiencies and pressure drops intend to produce much performance enhancement of the studied NDDCT. The film medium, Cellulose7060 with pressure drops of 28.6–272.1 Pa/m and cooling efficiency range of 44.7–88.5% is most promising for such pre-cooling enhancement. For the studied NDDCT, the critical temperatures below which the tower performance does not benefit but is hindered by wetted-medium pre-cooling are 28, 16, 30, 26 and 26°C for cellulose7090, cellulose7060, PVC1200, Trickle125 and Trickle100, respectively (ambient humidity of 20% and medium thickness of 200mm). The pre-cooling enhancements can go up to 100% by 200mm-thick cellulose7060 at extreme hot and dry climate (i.e., ambient temperature of 50°C and humidity of 20%). The simulation will give instructions for the design of pre-cooled NDDCTs.