Dissertations / Theses on the topic 'Plant conservation – Western Australia'
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1
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.
Abstract:
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.
2
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.
Abstract:
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.
3
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/.
Abstract:
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.
4
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.
Abstract:
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.
5
Sutcliffe, Karen Elizabeth. "The conservation status of aquatic insects in south-western Australia." Murdoch University, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040430.153605.
Abstract:
Freshwater ecosystems in south-western Australia have been extensively altered over the last two centuries as a result of human activities. The effect this has had on aquatic fauna, particularly invertebrates, is largely unknown because of inadequate knowledge of the pre-existing fauna. Future changes in the composition of aquatic fauna will also go undetected unless current distributions of existing species are well documented.
This thesis addresses the problem by investigating the current distributions and conservation status of aquatic insects in south-western Australia from three orders: Odonata, Plecoptera and Trichoptera. Extensive distributional data was collected by identifying larval specimens from a large number of samples collected throughout the south-west as part of an Australia-wide macroinvertebrate bioassessment project. In addition, a database created from a species-level biological study of the wheatbelt region of Western Australia was utilised, and previously published records of occurrence for species within the south-west were compiled. These results were then used to assess the conservation status of each species using the IUCN red list criteria.
Environmental parameters measured at time of sampling were also examined using logistic regression to determine which factors are important in influencing the distributions of aquatic insects in south-western Australia. The conservation value of sites based on Odonata, Plecoptera and Trichoptera compositions was also determined and the degree of protection provided for sites of high conservation value investigated.The high rainfall forested region of the south-west was found to be important for a large number of species, including the majority of those found to be rare and/or restricted.
Overall, 37% of species were found to be threatened, with the Trichoptera containing both the greatest number and highest proportion of threatened species. Logistic regression results generally agreed with the distributions obtained for each species, with rainfall and other parameters indicative of streams in the headwaters of forested catchments being positively associated with species found to be restricted to the high rainfall region. Two parameters known to be affected by human disturbance in the south-west, conductivity and nutrient concentrations, were found to be important in determining the occurrence of many species and this could have important consequences for aquatic insect conservation. Widespread species occurring within the low rainfall region of the south-west did not show as many significant relationships to measured environmental parameters, possibly due to their greater ecological tolerances and adaptations which allow them to persist in a low rainfall environment. The implications of results are discussed, and recommendations for the conservation and management of aquatic insects in south-western Australia are given.
6
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.
7
Naude, Minette. "Fynbos riparian biogeochemistry and invasive Australian acacias." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20325.
Abstract:
Thesis (MScConEcol)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Riparian ecotones, transitional areas between upland terrestrial communities and aquatic ecosystems, are very dynamic and complex ecosystems with intrinsic ecological properties differing in spatial structure, function and temporal dynamics. Riparian habitats along rivers of the Mediterranean south-western Cape are sensitive to environmental change and particularly vulnerable to invasion by invasive alien plants (IAPs), especially nitrogen-fixing Acacia spp., and yet relatively little work has focused on how riparian ecosystems in this region respond to such stressors. The important roles that intact riparian vegetation play in maintaining ecosystem integrity and services have been increasingly highlighted as we acknowledge the degradation of these habitats. While the Working for Water (WfW) programme has been shown to be very successful in eradicating IAPs in riparian zones in the short-term, the extent to which riparian ecosystems recover following alien clearing activities remains poorly understood. The results presented in this study addressed several different aspects of riparian structure and function and acts as a steppingstone for guiding future research and management in riparian zones by adding to the evaluation of the success of clearing initiatives and restoration thereof. The aim of this study was to assess plant functional type (PFT) cover, soil physical and chemical properties, and selected biogeochemical processes in natural, Acacia- invaded and cleared riparian ecotones and associated non-riparian upland fynbos. Fieldwork was performed in mountain and foothill sections of six perennial river systems within the south-western Cape. Eleven sites of three categories were chosen: four natural sites (uninvaded); four moderate to highly invaded sites (predominantly A. mearnsii); and three cleared sites (a formerly invaded site that had been cleared more than 7 years prior to the study). Within each site, four to five replicate plots were established along each of three geomorphological zones (wet bank, dry bank, and upland fynbos). Seasonal soil samples were collected for a period of one year. Results from this study showed that PFT cover and composition, soil physical and chemical properties and rates of nitrogen (N) and phosphorus (P) mineralization differed amongst invasion status, between geomorphological zones and across seasons. Regarding most soil physical and chemical properties and indices N and P cycling, river floodplains (dry banks) were very similar to terrestrial uplands. Acacia spp. changes soil properties and affects plant functional attributes by i) enriching the system with N; ii) enhancing litter inputs; iii) altering soil physical properties; iv) changing the composition and reducing the cover of PFT; and v) enhancing P mineralization rates. Although measured soil physical and chemical properties and N and P mineralization rates were reduced to levels that were similar to or resembled the situation at natural areas, available inorganic N remained two times higher after more than seven years of clearance. Furthermore, cleared areas were characterized by sparse woody cover and a high cover of alien grasses. Correlations between soil silt and clay content and several soil properties measured in this and other studies indicates important linkages between soil texture and resource availability. Clearing Acacia spp. may initiate restoration of invaded riparian ecosystems, but changes in ecosystem function (e.g. elevated soil N availability) as a result of invasion may necessitate active restoration following the removal of the alien species. Active restoration under such conditions would be required to facilitate the restoration of cleared riparian communities. However, we still lack the mechanistic understanding around fynbos riparian recovery after clearing, as the success of restoration may depend on complex interaction and feedback cycles between plants and their physical environment. A greater comprehensive understanding of fynbos riparian ecological processes will not only improve the effectiveness of restoration initiatives by integrating science and management, but also advance the field of riparian ecology.
AFRIKAANSE OPSOMMING: Rivier oewerwal-areas, oorgang gebiede tussen aangrensende terrestriële gemeenskappe en akwatiese ekosisteme, is baie dinamiese en komplekse ekosisteme met intrinsieke ekologiese eienskappe wat verskil in struktuur, funksie (bv. biogeochemie siklusse) en temporale dinamika. Oewerhabitatte langs riviere van die Mediterreense suid-wes Kaap is sensitief vir omgewingsveranderinge en kwesbaar vir indringing deur uitheemse plante (bekend as “invasive alien plants” (IAPs)), veral stikstof-fiksering Acacia spp., en relatief min werk het nog gefokus op hoe ekosisteme in die streek reageer op sulke veranderinge in die omgewing. Die belangrike rol wat gesonde oewerwal plantegroei speel in die handhawing van ekosisteemdienste- en integriteit, is al hoe meer uitgelig soos ons die agteruitgang van hierdie habitat in ag neem. Terwyl die Werk vir Water (WvW)-program al dat baie suksesvol was in die uitwissing van IAPs in oewersones in die kort termyn, is die mate waarin oewer-ekostelsels herstel na skoonmaakaksies swak verstaan. Fynbos oewerwal-areas is grootliks ingeneem deur houtagtige IAPs, veral stikstof fiksering Acacia spp. (soos Acacia mearnsii). Die resultate wat in hierdie studie aangebied is, het verskillende aspekte van oewer- struktuur en funksie aangespreek en dien as middel vir toekomstige navorsing en bestuur van oewerwal ekosisteme deur by te dra tot die evaluering van die sukses van skoonmaak inisiatiewe en die herstelproses daarvan. Die doel van hierdie projek was om die moontlikhede vir herstel van fynbos owerwal-ekostelsels te evalueer deur middel van verskeie grond- fisiese en chemiese eienskappe; plant funksionele groep dekking (genoem ‘plant functional types’ (PFT)); en geselekteerde grond biogeochemie prosesse in natuurlike, Acacia- aangetaste, en skoongemaakte rivierstelsels en nabygeleë terrestriese areas te vergelyk. Veldwerk is gedoen in bergstroom en voetheuwel rivierseksies van ses standhoudende rivierstelsels in Suid-wes Kaap, Suid Afrika. Van uit hierdie geselekteerde rivierstelsels is elf studie areas van drie kategorieë (of indringing status) gekies: vier natuurlike areas (nie aangetas); vier gematig- tot hoogs aangetaste areas (hoofsaaklik A. meanrsii); en drie skoongemaakte areas (rivieroewers wat meer as sewe jaar van te vore skoongemaak is). Binne elke studie area was vier tot vyf soortgelyke persele gevestig by elke van drie breë geomorfologiese sones: naamlik nat-, droë en hoogliggende terrestriese fynbos. Seisoenale grondmonsters vir 'n tydperk van een jaar is geneem. Resultate van hierdie studie het getoon dat PFT dekking en samestelling, grond fisiese- en chemiese eienskappe en N-mineralisasie en suur fosfatase aktiwiteit verskil tussen indringing status, geomorfologiese sones en oor seisoene. Ten opsigte van meeste grond fisiese en chemiese eienskappe en indekse van stikstof (N) en fosfor (P) siklusse kom die rivier vogregimes (droë oewersones) baie ooreen met die terrestriële gebiede. Aan die anderkant is die natbanksones gekenmerk deur grondeienskappe wat baie verskil van die ander twee geomorfologiese gebiede. Die gegewens ondersteun die hipotese dat indringing deur Acacia spp. verskeie grondeienskappe verander en plante se funksionele kenmerke beïnvloed deur i) die sisteem met voedingstowwe te verryk (veral N); ii) verhoog die toevoeging van plantmateriaal; iii) verander grond fisiese eienskappe; iv) verander die samestelling en verminder die dekking van PFT; v) en verhoog P biogeochemie. Hoewel grond fisiese -en chemiese eienskappe, en indekse van N en P mineralisasie verminder is tot vlakke wat soortgelyk aan natuurlike areas, het beskikbare anorganiese N twee keer hoër gebly by skoongemaakte gebiede. Nietemin, voorheen skoongemaakte gebiede is weer-binnegeval deur eksotiese grasse en die regenerasie of hertelling van inheemse fynbos gemeenskappe is taamlik beperk, veral houtagtige oewer struike en bome. Korrelasies tussen grond slik-en klei-inhoud en verskeie grondeienskappe gemeet in hierdie en ander studies dui op belangrike skakeling tussen die grondtekstuur en voedingstof beskikbaarheid. Die opruiming van Acacia spp. mag as aansporing dien vir die herstellingsproses van rivieroewerstelsels, maar veranderinge in die funksie van ekosisteme (bv. verhoogte grond N beskikbaarheid), as gevolg van indringing, mag aktiewe herstel noodsaak nadat die indringer spesies verwyder is. Aktiewe herstel onder sulke omstandighede sal verwag word om die herstel van skoongemaak oewer gemeenskappe te fasiliteer. Ons het wel egter nog 'n gebrek aan die meganistiese begrip in verband met die herstel van fynbos oewerwal areas na opruimings-inisiatiewe, sedert die sukses van herstel kan afhang van komplekse interaksie en terugvoer siklusse tussen die plante en hul fisiese omgewing. ʼn Meer omvattende begrip van fynbos rivieroewer ekologiese prosesse sal nie net die doeltreffendheid van opruimings-inisiatiewe deur die integrasie van wetenskaplike navorsing en bestuur verbeter nie, maar ook vooraf die gebied van rivieroewer-ekologie.
8
Mursidawati, Sofi. "Mycorrhizal association, propagation and conservation of the myco-heterotrophic orchid Rhizanthella gardneri." University of Western Australia. School of Earth and Geographical Sciences, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0014.
Abstract:
Many orchids require mycorrhizal symbioses with fungi for their development and survival. Rhizanthella gardneri the Western Australian underground orchid is associated with the companion plant Melaleuca uncinata and its ectomycorrhizal fungus symbiont. Much less is known about the habitat requirements of its sister species, R. slateri, which occurs in Eastern Australia. The absence of chlorophyll from Rhizanthella gardneri and R. slateri results in total dependency on associations with fungal symbionts. Many ecological and biological aspects of these fascinating orchids remained poorly known, including the identity of the fungal associates and the nature of their tripartite associations with Rhizanthella and Melaleuca. Extremely high specificity of these mycorrhizal relationships is likely to be the most important factor explaining the highly specific habitat requirements of underground orchids. The purpose of this study was to conduct further investigations of the role of the mycorrhizal associations of Australian underground orchids by identifying the fungi involved in these associations, optimising their growth in sterile culture and devising efficient means for synthesising their tripartite associations with R. gardneri and M. uncinata. In total, 16 isolates of fungi were successfully obtained from the two underground orchids and used in a series of experiments to understand both the nature of the fungi and their relationship with orchids. The identity of these fungi was established by using conventional morphological and molecular methods. Cultural and morphological studies revealed that all isolates from R. gardneri and R. slateri were binucleate rhizoctonias with affinities to members of the genus Ceratobasidium. However, the teleomorph state that was observed from the R. slateri symbiont during this study more closely resembled a Thanatephorus species. Further identification using ITS sequence comparisons confirmed that mycorrhizal fungi of Rhizanthella belonged to the Rhizoctonia alliance with relatives that include Thanatephorus, Ceratobasidium, or Rhizoctonia from other continents with over 90% similarity. Most of these related fungi are known as plant pathogens, but some were orchid mycorrhizal fungi. However, the isolates from the two underground orchids were most closely related to each other and formed a discrete group relative to other known members of the Rhizoctonia alliance. Sterile culture experiments determined culture media preferences for mycorrhizal fungi from Rhizanthella and other orchids. A fully defined sterile culture medium designed to more closely resemble Australian soil conditions was formulated. This new medium was compared to undefined media containing oats or yeast extract and recommendations for growth of these fungi are provided. The undefined media based on oats provided the best growth of most fungi, but the new Australian soil media was also effective at growing most orchid mycorrhizal fungi and this fully defined media was less prone to contamination and should provide more reproducible results. A comparison of three methods for inoculating M. uncinata with the underground orchid fungi resulted in the production and characterisation of ectomycorrhizal roots and hyphae formed by fungi isolated from R. gardneri and R. slateri. These underground orchid fungi could easily be distinguished from other mycorrhizal fungi (caused by airborne contamination) by the characteristic appearance of these roots and hyphae. A new system for growing and observing tripartite mycorrhizal associations was devised using pots with side viewing windows and the use of transparent seed packets to contain Rhizanthella seeds. This method allowed all the stages of seed germination to be observed in the glasshouse, culminating in the production of underground orchid rhizomes. Seed germination was only successful when seed was placed directly over active M. uncinata ectomycorrhizas confirmed to belong to the correct fungus by microscopic observations through the side of window pots. The importance of these new scientific discoveries concerning the biology and ecology of the underground orchids and their associated fungi for the recovery of these critically endangered orchids are discussed.
9
Pritchard, Deborah Leeanne. "Phosphorus bioavailability from land-applied biosolids in south-western Australia." Curtin University of Technology, Muresk Institute, 2005. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16492.
Abstract:
The annual production of biosolids in the Perth region during the period of this study was approximately 13,800 t dry solids (DS), being supplied by three major wastewater treatment plants. Of this, 70% was typically used as a low-grade fertiliser in agriculture, representing an annual land use area of around 1,600 ha when spread between 5 and 7 t DS/ha. Loading rates of biosolids are typically based on the nitrogen (N) requirements of the crop to be grown, referred to as the N Limiting Biosolids Application Rate (NLBAR). A consequence of using the NLBAR to calculate loading rates is that phosphorus (P) is typically in excess of plant requirement. The resultant high loading rates of P are considered in the guidelines developed for the agricultural use of biosolids in Western Australia, but lack research data specific to local conditions and soil types. Regulatory changes throughout Australia and globally to protect the environment from wastewater pollution have created a need for more accountable and balanced nutrient data. Experiments presented in this thesis were undertaken to ascertain: the percentage relative effectiveness (RE) of biosolids as a source of plant available P compared with inorganic P fertiliser; loading rates to best supply P for optimum crop growth; P loading rates of risk to the environment; and the forms of P in local biosolids. Therefore, both the agronomic and environmental viewpoints were considered. Anaerobically digested and dewatered biosolids produced from Beenyup Wastewater Treatment Plant, Perth with a mean total P content of 2.97% dry weight basis (db) were used in a series of glasshouse, field and laboratory experiments. The biosolids were sequentially fractionated to identify the forms of P present and likewise in soil samples after applying biosolids or monocalcium phosphate (MCP).The biosolid P was predominantly inorganic (92%), and hence the organic fraction (8%) available for mineralisation at all times would be extremely low. The most common forms of biosolid P were water-soluble P and exchangeable inorganic P (66%), followed by bicarbonate extractable P (19%) and the remaining P as inorganic forms associated with Fe, Al and Ca (14%). Following the application of biosolids to a lateritic soil, the Fe and Al soil fractions sorbed large amounts of P, not unlike the distribution of P following the addition of MCP. Further investigation would be required to trace the cycling of biosolid P in the various soil pools. The growth response of wheat (Triticum aestivum L.) to increasing rates of biosolids and comparable rates of inorganic P as MCP, to a maximum of 150 mg P/kg soil was examined in the glasshouse. The percentage relative effectiveness (RE) of biosolids was calculated using fitted curve coefficients from the Mitscherlich equation: y = a (1-b exp–cx) for dry matter (DM) production and P uptake. The initial effectiveness of biosolid P was comparable to that of MCP with the percentage RE of biosolids averaging 106% for DM production of wheat shoots and 118% for shoot P uptake at 33 days after sowing (DAS) over three consecutive crops. The percentage residual value (RV) declined at similar rates for DM production in MCP and biosolids, decreasing to about 33% relative to freshly applied MCP in the second crop and to approximately 16% in the third crop. The effectiveness of biosolid P was reduced significantly compared with inorganic P when applied to a field site 80 km east of Perth (520 mm annual rainfall). An infertile lateritic podsolic soil, consistent with the glasshouse experiment and representative of a soil type typically used for the agricultural application of biosolids in Western Australia was used.
Increasing rates of biosolids and comparable rates of triple superphosphate (TSP), to a maximum of 145 kg P/ha were applied to determine a P response curve. The percentage RE was calculated for seasonal DM production, final grain yield and P uptake in wheat followed by lupin (Lupinus angustifolius L.) rotation for the 2001 and 2002 growing seasons, respectively. In the first year of wheat, the RE for P uptake in biosolids compared with top-dressed TSP ranged from 33% to 55% over the season and by grain harvest was 67%. In the second year, and following incorporation with the disc plough at seeding, the RE for P uptake by lupins in biosolids averaged 79% over the growing season compared with top-dressed TSP, and by grain harvest the RE was 60%. The residual value (RV) of lupins at harvest in biosolids compared with freshly applied TSP was 47%. The non-uniform placement of biosolids (i.e. spatial heterogeneity) was primarily responsible for the decreased ability of plant roots to absorb P. The P was more effective where biosolids were finely dispersed throughout the soil, less so when roughly cultivated and least effective when placed on the soil surface without incorporation. The RE for grain harvest of wheat in the field decreased from 67% to 39% where biosolids were not incorporated (i.e. surface-applied). The RE could also be modified by factors such as soil moisture and N availability in the field, although it was possible to keep these variables constant in the glasshouse. Consequently, absolute values determined for the RE need to be treated judiciously. Calculations showed that typical loading rates of biosolids required to satisfy agronomic P requirements of wheat in Western Australia in the first season could vary from 0 to 8.1 t DS/ha, depending on soil factors such as the P Retention Index (PRI) and bicarbonate available P value.
Loading rates of biosolids were inadequate for optimum P uptake by wheat at 5 t DS/ha (i.e. 145 kg P/ha) based on the NLBAR on high P sorbing soils with a low fertiliser history (i.e. PRI >15, Colwell bicarbonate extractable P <15 mg P/kg). On soils of PRI <2 mL/g however, biosolids applied at identical loading rates would result in high concentrations of available P. Further work on sites not P deficient would be necessary to validate these findings on farmed soils with a regular history of P fertiliser. The sieving of soil samples used in the field experiment to remove stones and coarse organic matter prior to chemical analysis inadvertently discarded biosolids particles >2 mm, and thus their was little relationship between soil bicarbonate extractable P and P uptake by plants in the field. The risk of P leaching in biosolids-amended soil was examined over a number of different soil types at comparable rates of P at 140 mg P/kg (as either biosolids or MCP) in a laboratory experiment. Given that biosolids are restricted on sites prone to water erosion, the study focussed on the movement of water-soluble P by leaching rather than by runoff of water-soluble P and particulate P. In general the percentage soluble reactive P recovered was lower in soils treated with biosolids than with MCP, as measured in leachate collected using a reverse soil leachate unit. This was particularly evident in acid washed sand with SRP measuring 14% for biosolids and 71% for MCP, respectively, although the differences were not as large in typical agricultural soils. Specific soil properties, such as the PRI, pH, organic carbon and reactive Fe content were negatively correlated to soluble reactive P in leachate and thus reduced the risk of P leaching in biosolids-amended soil.
Conversely, the total P and bicarbonate extractable P status of the soils investigated were unreliable indicators as to the amount of P leached. On the basis of the experiments conducted, soils in Western Australia were categorised according to their ability to minimise P enrichment and provide P necessary for crop growth at loading rates determined by the NLBAR. Biosolids applied at the NLBAR to soils of PRI >2mL/g with reactive Fe >200 mg/kg were unlikely to necessitate P loading restrictions. Although specific to anaerobically digested biosolids cake applied to Western Australian soils, the results will be of relevance to any industry involved in the land application of biosolids, to prevent P contamination in water bodies and to make better use of P in crop production.
10
Fisher, Judith L. "Fundamental changes to ecosystem properties and processes linked to plant invasion and fire frequency in a biodiverse woodland." University of Western Australia. School of Plant Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0109.
Abstract:
[Truncated abstract] Mediterranean southwest Australia, a global biodiversity hotspot, has nutrient deficient soils, exacting climatic conditions and is species rich with 7380 native vascular plant species, of which 49% are endemic. The region is expected to experience one of the world's highest degrees of biodiversity loss and change in the coming decades, with introduced species presenting a major threat. Limited knowledge is available on the mechanisms of ecosystem change associated with invasion and fire in this biodiversity hotspot region. Banksia woodland, an iconic complex species-rich natural ecosystem is one of the major vegetation types of the coastal sandplain, extending from 15 to 90 km inland and 400 kms along the west coast. The following hypothesis was tested to explore the ecological impacts of invasion: Is invasion of Banksia woodland by the introduced species Ehrharta calycina and Pelargonium capitatum accompanied by an alteration in ecosystem properties and processes, whereby the degree of change is related to fire frequency and abundance of introduced species? Different vegetation conditions, i.e. Good Condition (GC), Medium Condition (MC), Poor Condition invaded by Ehrharta calycina (PCe) and Poor Condition invaded by Pelargonium capitatum (PCp) were utilized for field assessments. ... In the soil seed bank, species numbers and germinant density decreased significantly for native and seeder (fire sensitive) species between GC sites and invaded sites. Surprisingly 52% of germinants at GC sites were from introduced species, with much of the introduced soil seed bank being persistent. Native species were dominated by perennial shrubs, herbs and sedges, while introduced species were dominated by perennial and annual grasses and herbs. Invasion by introduced species, associated with frequency of fire, altered the ecosystem, thus disadvantaging native species and improving conditions for even greater invasion within the Banksia woodland. Significantly higher soil phosphorus P (total) and P (HCO3) were found at PCe and PCp sites compared to GC sites. Leaf nutrient concentrations of phosphorus were significantly higher, and potassium and copper significantly lower in PCe and PCp sites, with introduced species having significantly greater concentrations than native species (except Manganese). This study demonstrated the key role of phosphorus in the Banksia woodland, in contrast to other research which identified nitrogen as the major nutrient affected by invasion. Higher levels of soil and leaf phosphorus, loss of species diversity and function, changes in fire ecology and canopy cover and a limited native soil seed bank make restoration of a structural and functional Banksia woodland from the soil seed bank alone unlikely. Without management intervention, continuing future fire is likely to result in a transition of vegetation states from GC to MC and MC to PC. The knowledge gained from this study provides a better ecological understanding of the invasive process. This enhanced understanding will enable the development of adaptive management strategies to improve conservation practices within a biodiversity hotspot and reduce the impact of the key threatening process of invasion.
11
Richards, Jacqueline Denise. "The first reintroduction of the western barred bandicoot (Perameles bougainville) to mainland Australia." University of Sydney. Biological Sciences, 2005. http://hdl.handle.net/2123/692.
Abstract:
Almost half of the world�s mammal extinctions in the last two hundred years have occurred in Australia (Short and Smith 1994). The western barred bandicoot Perameles bougainville is one of a suite of species that is currently threatened with extinction, surviving only on two islands in Shark Bay, Western Australia. Reintroduction has been used as a tool in conservation biology to assist in the recovery of threatened species, such as the western barred bandicoot. The aims of this project were to 1) successfully reintroduce and establish a free-ranging mainland population of the western barred bandicoot at Heirisson Prong, Shark Bay, 2) contribute information on the biology of the species, its interactions with introduced species, and its likelihood of persistence as a reintroduced population in the longer-term, and 3) to provide recommendations to assist future reintroductions of the species. The first reintroduction of the western barred bandicoot from surviving remnant island populations to the mainland, some 60 years after its apparent mainland extinction, was from Dorre Island to Heirisson Prong in 1995. Animals were translocated initially to a predator-free refuge on Heirisson Prong, and then subsequently released to the 12 km2 peninsula where introduced predators (foxes Vulpes vulpes and feral cats Felis catus) had been controlled, but European rabbits Oryctolagus cuniculus had not. Despite a small founder number and high mortality of free-range bandicoots in the presence of a low-density feral cat population, the bandicoot population successfully established. The reintroduced population of western barred bandicoots provided an opportunity to study the biology of the species, and to compare it with the remnant island populations and other species of Australian bandicoot. Many population parameters were similar between the island and mainland western barred bandicoot populations, as well as between the western barred bandicoot and other bandicoot species, suggesting that the habitat at the reintroduction site is suitable for long-term persistence of the population. However, there were some notable differences. The western barred bandicoot is the smallest extant species of bandicoot, with fewer young per litter than recorded for other bandicoot species, adult sex ratios were closer to parity, animals reached sexual maturity later, and it is the only species of bandicoot where females are larger than males. Home range size is larger also than recorded for other species. Some of these differences may be explained in part by trade-offs between island dwarfism, lactational pressures, and nest defence. The nesting biology of the western barred bandicoot was studied at Heirisson Prong, including during periods of high and low densities of rabbits. Individuals of the species constructed and utilised nests in a similar fashion to other species of Australian bandicoot, nesting amongst litter underneath shrubs. The western barred bandicoot appeared to favour particular shrub species, especially when vegetation condition was poor due to rabbit damage, but displayed flexibility in being able to construct nests under a variety of shrub species where at least some surface litter was present. Grasses were used in nest construction only when rabbit density was low. Nests appear important for protection against temperature extremes and diurnal predators. Vegetation exclosures around three of the shrub species most commonly used by the western barred bandicoot for nest sites (Acacia ligulata, A. tetragonophylla and Melaleuca cardiophylla) were used to examine the impact of rabbits on vegetation on Heirisson Prong. A high-density rabbit population over the summer of 1997/98 caused in a decrease in canopy cover and the death of mature A. ligulata. Subsequent rainfall and low-density rabbit populations allowed A. tetragonophylla shrubs to recover their former structure, and M. cardiophylla to recover, but not to the same degree. The flexibility of western barred bandicoots in use of nest materials and their omnivorous diet may enable the species to survive in the face of habitat modification by rabbits. Population viability analysis was used to examine future options for the recovery of the endangered western barred bandicoot. Biological data from the Dorre Island and Heirisson Prong populations were input to the computer simulation program VORTEX. The western barred bandicoot populations were modelled under a variety of scenarios to examine the possible effects of changes in carrying capacity, founder population size, inbreeding depression, and the occurrence of drought and cat predation as catastrophes, on the probability of population extinction. This analysis highlighted the need for eradication of feral cats, above all other management actions. Cat predation was particularly potent when it acted through high loss of juveniles, as well as adult bandicoots. Predator control is considered critical for the long-term persistence of reintroduced populations of the western barred bandicoot. This study documents the first reintroduction of the endangered western barred bandicoot to mainland Australia. The population had been extant for four years at the completion of data collection for this thesis, in late 1999 and for over eight years at the finalisation of this thesis in July 2004. The knowledge gained from the reintroduction was used to discuss management recommendations and future options for the recovery of the species. The primary concern for reintroductions of this, and other species of bandicoots, remains the control of introduced predators. For long-term persistence of small, isolated populations, such as those of the western barred bandicoot at Heirisson Prong and the Arid Recovery Project at Roxby Downs in South Australia, and the eastern barred bandicoot Perameles gunnii at a range of sites in Victoria, the complete eradication of introduced predators is essential.
12
Bhatti, Muhammad Ali. "Genetic variation in naturalized wild radish (Raphanus raphanistrum L.) populations in the mediterranean climate of south-western Australia." University of Western Australia. School of Plant Biology, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0012.
Abstract:
[Truncated abstract] Wild radish (Raphanus raphanistrum L.), an outcrossing annual plant, is one of the most widespread and successful colonising weeds in the Australian wheat belt. It was introduced accidentally during the latter part of the 19th century, apparently independently through the major ports of southern Australia. The widespread success of wild radish, and therefore the likelihood of distinct populations, gives us the opportunity to study the colonizing process with adaptation in annual outbreeding species, and to explore their genetic diversity. The aims of this thesis were to study the genetic diversity of wild radish and to investigate which factors are important in its success. After an initial review of the literature (chapter 2), the thesis describes experiments where genetic variation between and within populations was compared at 55 sites in transects across the wheat belt and high rainfall zones of temperate Western Australia (chapter 3). In chapter 4, variation in life history traits was compared with variation in AFLP molecular markers. The role of seed dormancy in the survival of the species was examined in chapter 5, and variation in the oil content of seeds and their fatty acid composition was examined in chapter 6. Finally, the results were discussed in chapter 7 with special reference to the adaptive value of outcrossing in annual weeds. The results suggest that wild radish has evolved to fit the Australian environment. However, measurement of 14 morphological and phenological characters showed that in most cases within site variation was much greater than that between sites. Most of the variation between sites was associated with geoclusters, a name given to zones of similar environmental conditions in regard to rainfall and temperature. Thus plants from areas with high rainfall and low temperature produced longer, wider pods with more segments, heavier seeds and flowered later than plants from more arid areas.
13
Noack, Denise Helen. "The contribution of heritage agreements to conservation in the Murray Mallee of South Australia /." Title page, contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09ENV/09envn739.pdf.
14
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.
Abstract:
[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.
15
Duxbury, M. L. "Implementing a relational worldview : Watershed Torbay, Western Australia - connecting community and place /." Access via Murdoch University Digital Theses Project, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20080617.132132.
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.
Abstract:
[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.
17
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.
Abstract:
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.
18
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.
Abstract:
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.
19
Bunny, Felicity J. "The biology, ecology and taxonomy of Phytophthora citricola in native plant communities in Western Australia." Murdoch University, 1996. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061122.122739.
Abstract:
The objectives of the project were to develop an understanding of the disease dynamics caused
by Phytophthora citricola in native plant communities in the south of Western Australia. Prior
to 1983, the pathogen had only been reported twice from Australian forests. Since then,
P. citricola has been extensively recorded from plant communities north and south of Perth, and
is currently the second most frequently recovered Phytophthora species from the northern jarrah
forest and the northern sandplains.
The objectives were addressed by examining the biology, ecology and taxonomy of
isolates of P. citricola local to the southwest. Examination of the intraspecific variation of
P. citricola by isozyme analysis resolved three major electrophoretic subgroups (SG), and these
were aligned with morphological and cultural variation within the species. One electrophoretic
SG was confined to forested areas. This SG differed from other SGs in sporangial dimensions,
growth rate on two media and in vitro sensitivity to phosphonate. A redescription of the species
may be warranted.
P. citricola was positively associated with two roads in the northern jarrah forest. Road
surfaces were sampled, then soil overburden was removed and the surface of the concreted
lateritic layer beneath was sampled. Isolation of P. citricola declined away from the road into the
adjacent forest and was more frequently recovered from the caprock (up to 1 metre below soil
surface) than from the soil surface. The most probable source of introduction was from infested
soil on vehicles using the roads.
Oospores were shown to be produced in two soils, a lateritic gravelly loam and sand,
and in plants. In soil, the electrophoretic SG confined to the forest (loamy soil) produced only
limited numbers of oospores in the sandy soil of the northern sandplain. The restriction of this
SG to the forested areas is probably physiological, rather than limited dispersal, with the SG
currently occupying the full extent of its range. Estimation of the relative persistence of
oospores, zoospores and plant material colonised by P. citricola established that only oospores
(either free in soil or in colonised plant material) were important in long tern survival in soil.
Oospores were still viable after six months at two field sites, and after 18 months in soil in the
laboratory.
Phosphonate is currently the most promising method of control of Phytophthora induced
disease in native plant cornmunites of the southwest. The efficacy of phosphonate against
P. citricola was examined in vivo and in vitro against two SGs. Phosphonate successfully
inhibited lesion growth of both SGs in vivo, but of only one electrophoretic subgroup in vitro.
The ecological implications of infestation of native plant communities in the southwest
of Australia are discussed.
20
Bunny, F. "The biology, ecology and taxonomy of Phytophthora citricola in native plant communities in Western Australia /." Access via Murdoch University Digital Theses Project, 1996. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061122.122739.
21
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.
Abstract:
[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
22
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.
23
Venn, Darren Peter. "A changing cultural landscape Yanchep National Park, Western Australia /." Connect to thesis, 2008. http://portalapps.ecu.edu.au/adt-public/adt-ECU2008.0012.html.
24
Paap, Trudy. "The incidence, severity and possible causes of canker disease of Corymbia calophylla (marri) in the southwest of Western Australia." Paap, Trudy (2006) The incidence, severity and possible causes of canker disease of Corymbia calophylla (marri) in the southwest of Western Australia. PhD thesis, Murdoch University, 2006. http://researchrepository.murdoch.edu.au/241/.
Abstract:
The impact of a canker disease of Corymbia calophylla (marri) in the southwest of Western Australia (WA) has increased substantially since it was first observed causing decline and death of this species in the 1970s. By the early 1990s there were expressions of concern and calls to determine the cause and management options. Despite this, there has been very little research into the incidence, severity and possible causes of the disease. There are, however, historical reports dating back to the 1920s of a canker disease of amenity planted C. ficifolia caused by Sporotrichum destructor, though the diagnosis and Latin description were never published. It has been suggested that there may be links between this species and the genus Quambalaria, a group containing leaf and shoot pathogens of species of Eucalyptus and Corymbia.
This study examined the incidence and symptomology of the disease, the range of fungal species associated with healthy and diseased C. calophylla, and the pathogenicity of isolates obtained from these surveys. Also investigated was the identity of the pathogen, S. destructor, historically attributed to canker disease of C. ficifolia, to determine whether this pathogen is responsible for the current epidemic of C. calophylla canker and if it is synonymous with Quambalaria.
Cankers were present on trees across the range of surveyed sites, with lesions occurring on trunks, branches or twigs of 25.7 % of the C. calophylla surveyed. Canker incidence was significantly greater on trees present at remnant sites, such as roadsides and in paddocks, than forest trees being 38 % and 13.3 %, respectively. Tree height, trunk diameter at breast height and crown position, size and health ratings were significant predictors of canker presence, with cankers more common on larger, older trees and trees with poor crown condition. Bark cracks exuding kino were present on 48 % of the surveyed trees, and when dissected, lesions were observed on 40 %, suggesting that these cracks could be the initial stages of canker disease. This was confirmed by the observation of a number of cracks that developed into perennial cankers during the three year study. Monitoring of canker development and the examination of transverse sections showed the circumvention of host defenses by the pathogen and the subsequential walling off response of the host (which typifies perennial cankers) was not necessarily an annual event, with no change observed in some cankers over the three year period, while others progressed rapidly in that time, occasionally to the point of girdling and killing the host.
Initial surveys isolated 44 fungal species from healthy and diseased C. calophylla, with opportunistic pathogens including Endothiella eucalypti and Cytospora eucalypticola common. Subsequent surveys foccussed more on a potential pathogen in the genus Quambalaria, which was rarely isolated from active lesions, presumably because of its slow growth rate, but which sporulated consistently on the surface of older sections of the cankers.
DNA sequences confirmed that Q. cyanescens and Q. pitereka are present in southwest WA, with the latter associated with leaf and shoot disease. A third and new species of Quambalaria was isolated from cankers. Comparisons of disease symptoms and conidiogenesis indicate this species is synonymous with S. destructor. The species is formally described here as Q. coyrecup T. Paap sp. nov.
A pathogenicity trial was unsuccessful in causing disease symptoms in trees inoculated with core plugs taken from canker lesion margins of diseased trees, though the time frame and environmental factors may not have been adequate for disease development. The core plug inoculation method may also have failed because opportunistic pathogens which were frequently isolated from lesions out-competed Q. coyrecup (paralleling the results achieved by culturing from lesions). Quambalaria coyrecup caused symptoms matching those observed in natural infections when suitable hosts were inoculated, confirming it is the fungus responsible for the current canker disease of C. calophylla and C. ficifolia. Endothiella eucalypti also caused significant lesions, though these were not typical of natural infections, which together with its frequent isolation from both healthy and diseased trees suggests it is an opportunistic pathogen, potentially contributing to disease development in trees already infected with Q. coyrecup.
Isolates of Q. pitereka from WA and eastern Australia both caused typical shoot blight symptoms in the WA hosts C. calophylla and C. ficifolia, and the eastern Australian host C. maculata, though a larger path trial is required to examine the possibility of host specificity. Quambalaria cyanescens was non-pathogenic in all inoculation trials.
The current cause of cankers in C. calophylla is now known to be the same as the fungus historically implicated in the canker disease of C. ficifolia, when at the time it was described as an endophyte doing little or no damage in C. calophylla. Thus, it is of immediate importance to determine the factors driving this decline, and develop control and management options.
25
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.
Abstract:
[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.
26
Ryan, Kylie A. "Small, no-take marine protected areas and wave exposure affect temperate, subtidal reef communities at Marmion Marine Park, Western Australia." University of Western Australia. School of Plant Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0130.
Abstract:
[Truncated abstract] The ecological effects of marine protected areas (MPAs) in temperate ecosystems are poorly understood relative to their tropical counterparts. The limited number of rigorous empirical studies supporting existing theoretical models, increasing public awareness of the importance of marine conservation strategies and legislative requirements to review management effectiveness provide further impetus to study temperate MPAs. Investigations should consider confounding effects of natural variability if MPA effects are to be clearly demonstrated. This research helps to address these needs by investigating the short term effects of sanctuary zones (no-take MPAs where fishing is prohibited) and wave exposure at Marmion Marine Park, Western Australia. The three sanctuary zones at Marmion Marine Park are extremely small (0.061 0.279 km2) compared to most reported in the literature. The sanctuary zones are nested within a larger, fished zone (94.95 km2). The sanctuary zones have been protected from fishing since the year 2000. A post-hoc, asymmetrical sampling design was used in this study and involved surveys of fishes, mobile invertebrates and macroalgae at one sanctuary zone and two fished sites (controls) at each of three successive, subtidal reef lines. The three reef lines are exposed to a gradient in wave energy. The size structure and abundance of the heavily exploited Panulirus cygnus (Western Rock Lobster) were positively affected by protection from fishing in sanctuary zones, despite the highly mobile nature of this migratory species. The mean abundance of legal size lobsters was higher in sanctuary zones compared to fished sites during an interannual study (2003, 2005 and 2006). The total abundance of lobsters and the mean abundance of legal size lobsters were higher at inshore and offshore sanctuary zones compared to fished control sites during a 2005/2006 fishing season study. These zoning effects did not vary with the time of survey. ... Furthermore, the abundance of large lobsters in sanctuary zones decreased with the duration of the 2005/2006 fishing season. Similarly, it is likely that sanctuary zones are too small relative to the movement of fishes to adequately protect stocks of some targeted species. The small sanctuary zones at Marmion are unlikely to offer protection to highly mobile species over the long term. And finally, ecological assemblages within each level of wave exposure are distinct. Consequently for each assemblage type, the current reserve design does not include replication of sanctuary zones and does not offer any 'insurance' in the event of isolated impacts affecting a particular zone. This study has identified the benefits and deficiencies of the design and function of small no-take temperate MPAs in Western Australia. An increase in the size and number of sanctuary zones within each wave exposure level will help to address the v shortfalls of the zoning scheme and enhance the conservation benefits of management at Marmion Marine Park. More generally, this study demonstrates that the mobility of the species to be protected from fishing should be considered when designing MPAs. Lessons learned from this work will be beneficial for the future management and conservation of resources in the region and elsewhere.
27
au, chalwell@yahoo com, and Shane Thomas Samuel Chalwell. "Plant Communities of Greenstone Hills of the Eastern Goldfields of Western Australia as Analogues for the Rehabilitation of Rocky Waste Dumps." Murdoch University, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20041014.113057.
Abstract:
The vegetation of greenstone hills in the Kalgoorlie area of the Eastern Goldfields region of Western Australia was studied to identify the key environmental influences on community and species distribution. This information was needed to determine if plant communities of the hills could provide analogues for the rehabilitation of waste rock dumps that are produced as a consequence of open cut mining.
The ridges, slopes and flats adjacent to the main slope were examined and the floristic data sorted into communities. Two structurally and floristically distinct alliances were identified, one dominated by eucalypt species and the other by Acacia quadrimarginea. The eucalypt woodland displayed a taller upper stratum and few groundlayer species and was the dominant vegetation of the flats at the base of the hills. The acacia community was a low woodland and is the dominant vegetation of the hill slopes. Both communities were dominant at an equal number of sites on the ridges of the hills.
An investigation of the environmental variables found that edaphic, rather than topographic, factors were responsible for the community distribution on the hills. The eucalypt woodland showed a strong affinity to soils derived from calcrete, which had higher levels of electrical conductivity and lower exchangeable sodium percentages than the soils of the acacia low woodland. Under such conditions, the clay fraction of the soil remains in a more flocculated state allowing higher rates of water infiltration and hydraulic conductivity compared to the acacia soils. Soil nutrients were found to have a secondary influence on community distribution and had a greater effect on species distribution within alliances.
A study of the seasonal variation in water content of the soils showed that more moisture is retained in the upper soil horizons in the acacia community than in the eucalypt community during the wetter part of the year, indicating the acacia soils had poorer infiltration properties than the eucalypt soils. The distribution of drought tolerant species such as A. quadrimarginea and Prostanthera incurvata was found to be correlated to soil moisture content of the dry season whilst no correlation was found for the eucalypts at any time of the year.
Seasonal comparisons of leaf moisture content and xylem pressure potential showed that the eucalypts maintained their total leaf moisture content throughout the year whereas species such as A. quadrimarginea and Allocasuarina campestris recorded high levels of desiccation of their leaf tissue over the summer. The eucalypts also maintained a more consistent pre-dawn xylem pressure potential throughout the year than either A. quadrimarginea or the shrub species Dodonaea microzyga, indicating a greater degree of stomatal control and access to a more consistent soil water supply. The eucalypts require access to a greater soil volume than the acacias or shrubs in order to ensure sufficient water supplies for the maintenance of tissue moisture levels throughout the year. In this way, the eucalypts are able to effectively avoid the summer drought, whereas the acacias and shrubs are able to tolerate desiccation of their leaf tissues over this period.
Investigations of the germination requirements and early seedling survival of prominent species from the greenstone hills indicated that fire may be a factor in the regeneration of most hills species. All studied species were either tolerant of or responded positively to the application of dry heat. In relation to seedling establishment on waste dumps, increasing the soil moisture content of waste dump soils increased the germination rate of most species but did not result in greater seedling survival at the end of the first summer. The provision of microsites which encouraged root development and provided protection for the young seedlings was found to be more important in reducing mortality rates in the first year than increasing the total germination.
The study emphasized the importance of physical soil factors and the soil moisture regime in the distribution of eucalypt and acacia communities on the greenstone hills. A species response to drought stress strongly influences its ability to compete for soil water on different soil types. The eucalypts studied in this project dominated on soils where there is better recharge of subsoil water reserves which can be accessed over the summer period to maintain tissue water levels. Acacias are tolerant of tissue desiccation and will compete successfully on shallower soils and where hydraulic conductivity is poor.
Although the project was valuable in identifying water relations as the main control on community distribution on the hills, waste dumps are not strictly analogues of intact greenstone hills due to the differences in rock type and profile formation. Electrical conductivity levels are also higher due to extraction processes. However, the environmental relationships of the different species show that the more drought tolerant species such as Allocasuarina campestris, Acacia quadrimarginea and understorey species associated with them, may be suitable species to form the basis of vegetation reinstatement on waste dumps in the Kalgoorlie region.
28
Everard, David Alexander. "The conservation status of some unique plant communities in the Eastern Cape." Thesis, Rhodes University, 1986. http://hdl.handle.net/10962/d1007497.
Abstract:
In response to a growing concern over the rising rates of extinction of the world's plants and of habitat destruction, studies of Southern African threatened plants were initiated in the 1970's. These studies, which have largely concentrated on Western Cape flora, led to the publication of "Threatened Plants of Southern Africa" by Hall et al., 1980, which attempted to list as many threatened or possibly threatened species as possible. It was however marred by a lack of recent herbarium records and detailed studies from many parts of the region, the Eastern Cape being one of these. In order to extend these detailed studies to gain a clearer picture of the numbers of threatened species in the Eastern Cape and evaluate the conservation status of Eastern Cape vegetation this project was initiated. Initially lists of possibly threatened and endemic taxa of the Eastern Cape were compiled from various sources. These listed taxa were then checked against herbarium records, all available information being filled onto index cards for filing purposes. This paper-based filing system was then transferred into a computer-based data bank to facilitate the efficient storage and retrieval of information. Results from this data bank show that there are 662 variously threatened plant taxa in the Eastern Cape, many of which fall into temporary categories which need to be clarified by investigation in the field. Primarily based on the above results, a table ranking the various vegetation types into an order of priority for investigations about conservation requirement was developed.Subtropical Thicket was found to be the vegetation type in most need of investigation and so an extensive phytosociological survey was carried out in the Valley Bushveld which forms the major portion of Subtropical Thicket in the Eastern Cape. Twelve sites were sampled for floristic and environmental variables along a rainfall gradient of between 300 mm yr⁻¹ and 1 000 mm yr⁻¹ and along a longitudinal gradient from the Buffalo River in the east to the Gamtoos-Kromme complex in the west. Floristic data W(re analysed using multivariate techniques of classification and ordination. A classification by two-way species indicator analysis revealed the Valley Bushveld to consist of two orders of thicket, the Kaffrarian Succulent Thicket containing the two suborders, Inland Succulent Thicket and the Coastal Succulent Thicket and the Kaffrarian Thicket containing Coastal Kaffrarian Thicket and Inland Kaffrarian Thicket. Ordina tion by detrended correspondence analysis also grouped sites according to these vegetation categories in a sequence along one axis, to which the rainfall gradient could be related. Variables such as diversity indices, numbers of endemics, numbers of threatened taxa and structural features were also extracted from the data and these were correlated with environmental variables by multiple regression analysis. Species richness and the percent woody component w\!re positively correlated with rainfall while endemism and percent succulent component were strongly negatively correlated with rainfall. Most of the other relationships were explained by interrelationships with rainfall. Finally the sites were evaluated according to floristic criteria indicative of conservation value. The Coastal Succulent Thicket appeared to have the highest conservation value mainly owing to high endemism, while Inland Kaffrarian Thicket was also important as it supports a high number of species. The thickets with high conservation value are therefore the thickets of coastal areas in the western parts of the Eastern Cape which receive a low rainfall and the thickets which receive a rainfall in excess of 800 mm.KMBT_363
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29
Honda, Motoshi. "Relationships between flood frequency and riparian plant community structure in mountain streams of western Montana." The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-05302008-155627/.
Abstract:
Flooding is the dominant factor structuring riparian plant communities along large, low elevation streams, but it is less clear what role flooding plays in the structure and composition of riparian plant communities along mountain streams. In the first part of this study, I examined the influence of four environmental variables (flood frequency, microtopography, light availability, and soil texture) and spatial heterogeneity on riparian plant community structure in seven study areas along mountain streams in western Montana, USA. Multivariate and spatial statistics were used to determine the relative strength of each set of factors and their interactions in explaining riparian plant community structure. Flooding influenced vegetation characteristics by an indirect pathway through microtopography in all study areas, whereas the direct influence of flooding was found commonly only in three study areas. Other consistent direct influences included light (60%) and space (87%). Direct and indirect influences of flood frequency through microtopography, and the direct influences of light and vegetation patch structure should be included in predictive models of riparian plant community structure in mountain streams. Boundary analysis showed that microtopography was an important factor for boundary maintenance of riparian plant communities. In the second part of the study, the effective flood frequency was determined initially by partial Mantel tests between inundation extent associated with each flood frequency and plant communities, and the results were compared to floristic characteristics derived from DCA and Indicator Species Analysis. Flood frequencies ranging from one to eight years were most strongly associated with the understory and overall plant community structure, whereas overstory communities were influenced by both frequent (¡Ü 9 year) and large infrequent (¡Ý35 year) floods. Riparian plant communities in mountain streams are mostly influenced by frequent flooding but large floods are also important for maintaining spatial heterogeneity.
30
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.
Abstract:
[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.
31
Sharma, Jyotsna. "Mycobionts, germination, and conservation genetics of federally threatened Platanthera praeclara (Orchidaceae) /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060142.
32
Jefferson, Lara Vanessa. "The biology and ecology of species of Maireana and Enchylaena : intra- and inter- specific competition in plant communities in the eastern goldfields of Western Australia /." Curtin University of Technology, School of Chemical and Biological Sciences, 2001. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=14451.
Abstract:
Members of the family Chenopodiaceae are routinely used as colonizer plant species to rehabilitate waste and tailings materials on mine sites in the Eastern Goldfields of Western Australia. These are specifically selected for their salt and drought tolerance and also because they are representative of the surrounding natural vegetation. Where these have been sown, competition between several species has been observed. The resulting plant community structure is typically lower in species diversity than the initial seed mixture. This study aimed to determine whether competition was occurring between five of the species commonly used and some of the mechanisms that determine community structure on the rehabilitated areas of waste material. Atriplex bunburyana, Atriplex codonocarpa, Maireana brevifolia, Maireana georgei and Enchylaena tomentosa were selected for the study, which was conducted in three parts. Firstly, different plant densities and species combinations were studied in the field and in a pot trial to determine whether or not competition was occurring and to determine the resources that the plants were competing for. The results of the field trial revealed that competition was occurring, but that it formed only one component of the complex interactions between plant species, density and soil characteristics (i.e. pH and salinity). The pot trial complemented the outcome of the field trial. In addition, it showed that competition was occurring, but was even more pronounced. This was most likely due to the lack of nutrients and the limited availability of space in the pots.In the second part of this study, the ability of each species to survive and grow when subjected to adverse environmental conditions, such as low moisture availability, high salinity and low light availability, was examined in relation to competition. All five species were treated with different water regimes and soil salinity. Salt played an important role, especially for the Atriplex spp. and M. brevifolia, in ensuring survival when moisture availability was low. The effect of shade on the Maireana species and E. tomentosa was also researched after field observations suggested that M georgei was adversely affected when growing within the canopy of A. bunburyana. The pot trial showed that growth of M. georgei was affected by progressively more shade, whereas E. tomentosa was facilitated by shade. Maireana brevifolia exhibited significant tolerance to low light intensity. In the last part of this three-part study, all five chenopods were screened for allelopathy. Allelopathy may play an important role in determining community structure in successive plant generations. All chenopod species produced allelopathic substances, which were isolated from their leaves. The inhibition of seed germination was found to be speciesspecific and occurred only at certain concentrations. The seed of the Atriplex spp. was not affected by M. georgei and E. tomentosa extracts.
33
Bryan, Nicholas Joseph. "Characteristics of the Unionid Community and Habitat in a Power Plant Thermal Plume in Western Lake Erie." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1369403135.
34
Chalwell, Shane Thomas Samuel. "Plant communities of greenstone hills of the Eastern Goldfields of Western Australia as analogues for the rehabilitation of rocky waste dumps." Chalwell, Shane Thomas Samuel (2003) Plant communities of greenstone hills of the Eastern Goldfields of Western Australia as analogues for the rehabilitation of rocky waste dumps. PhD thesis, Murdoch University, 2003. http://researchrepository.murdoch.edu.au/510/.
Abstract:
The vegetation of greenstone hills in the Kalgoorlie area of the Eastern Goldfields region of Western Australia was studied to identify the key environmental influences on community and species distribution. This information was needed to determine if plant communities of the hills could provide analogues for the rehabilitation of waste rock dumps that are produced as a consequence of open cut mining.
The ridges, slopes and flats adjacent to the main slope were examined and the floristic data sorted into communities. Two structurally and floristically distinct alliances were identified, one dominated by eucalypt species and the other by Acacia quadrimarginea. The eucalypt woodland displayed a taller upper stratum and few groundlayer species and was the dominant vegetation of the flats at the base of the hills. The acacia community was a low woodland and is the dominant vegetation of the hill slopes. Both communities were dominant at an equal number of sites on the ridges of the hills.
An investigation of the environmental variables found that edaphic, rather than topographic, factors were responsible for the community distribution on the hills. The eucalypt woodland showed a strong affinity to soils derived from calcrete, which had higher levels of electrical conductivity and lower exchangeable sodium percentages than the soils of the acacia low woodland. Under such conditions, the clay fraction of the soil remains in a more flocculated state allowing higher rates of water infiltration and hydraulic conductivity compared to the acacia soils. Soil nutrients were found to have a secondary influence on community distribution and had a greater effect on species distribution within alliances.
A study of the seasonal variation in water content of the soils showed that more moisture is retained in the upper soil horizons in the acacia community than in the eucalypt community during the wetter part of the year, indicating the acacia soils had poorer infiltration properties than the eucalypt soils. The distribution of drought tolerant species such as A. quadrimarginea and Prostanthera incurvata was found to be correlated to soil moisture content of the dry season whilst no correlation was found for the eucalypts at any time of the year.
Seasonal comparisons of leaf moisture content and xylem pressure potential showed that the eucalypts maintained their total leaf moisture content throughout the year whereas species such as A. quadrimarginea and Allocasuarina campestris recorded high levels of desiccation of their leaf tissue over the summer. The eucalypts also maintained a more consistent pre-dawn xylem pressure potential throughout the year than either A. quadrimarginea or the shrub species Dodonaea microzyga, indicating a greater degree of stomatal control and access to a more consistent soil water supply. The eucalypts require access to a greater soil volume than the acacias or shrubs in order to ensure sufficient water supplies for the maintenance of tissue moisture levels throughout the year. In this way, the eucalypts are able to effectively avoid the summer drought, whereas the acacias and shrubs are able to tolerate desiccation of their leaf tissues over this period.
Investigations of the germination requirements and early seedling survival of prominent species from the greenstone hills indicated that fire may be a factor in the regeneration of most hills species. All studied species were either tolerant of or responded positively to the application of dry heat. In relation to seedling establishment on waste dumps, increasing the soil moisture content of waste dump soils increased the germination rate of most species but did not result in greater seedling survival at the end of the first summer. The provision of microsites which encouraged root development and provided protection for the young seedlings was found to be more important in reducing mortality rates in the first year than increasing the total germination.
The study emphasized the importance of physical soil factors and the soil moisture regime in the distribution of eucalypt and acacia communities on the greenstone hills. A species' response to drought stress strongly influences its ability to compete for soil water on different soil types. The eucalypts studied in this project dominated on soils where there is better recharge of subsoil water reserves which can be accessed over the summer period to maintain tissue water levels. Acacias are tolerant of tissue desiccation and will compete successfully on shallower soils and where hydraulic conductivity is poor.
Although the project was valuable in identifying water relations as the main control on community distribution on the hills, waste dumps are not strictly analogues of intact greenstone hills due to the differences in rock type and profile formation. Electrical conductivity levels are also higher due to extraction processes. However, the environmental relationships of the different species show that the more drought tolerant species such as Allocasuarina campestris, Acacia quadrimarginea and understorey species associated with them, may be suitable species to form the basis of vegetation reinstatement on waste dumps in the Kalgoorlie region.
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Clark, Stephanie A. "Systematics, spatial analysis and conservation genetics of Meridolum corneovirens (Pfeiffer, 1851) and related forms (Gastropoda: Camaenidae) from the Sydney region of Australia /." View thesis, 2005. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20051019.154748/index.html.
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Worth, David John. "Reconciliation in the forest? : an exploration of the conflict over the logging of native forests in the south west of Western Australia." Murdoch University, 2004. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040804.161830.
Abstract:
Over the past 30 years in Western Australia (WA), there has been a heated debate about the future use of the remaining temperate old-growth forests of karri and jarrah in the south-west of the State. This debate revolved around policy proposals from two social movements: one social movement wanted to preserve as much of the remaining old-growth forests as possible, and an opposing social movement supported a continued sustainable logging of the forests for hardwood products. This research project undertook a comparative case study analysis of Australia (TCA) on the pro-logging side and Liberals For Forests (LFF) on the anti-logging side. It drew on a macro-level European theoretical approach (New Social Movement theory) and a US organizational approach (Resource Mobilisation Theory). The study also investigated the extent to which these two social movement organisations (SMOs) had been effective in
Over the past 30 years in Western Australia (WA), there has been a heated debate about the future use of the remaining temperate old-growth forests of karri and jarrah in the south-west of the State. This debate revolved around policy proposals from two social movements: one social movement wanted to preserve as much of the remaining old-growth forests as possible, and an opposing social movement supported a continued sustainable logging of the forests for hardwood products. This research project undertook a comparative case study
analysis of one WA organisation from each of these two social movements- Timber Communities Australia (TCA) on the pro-logging side and Liberals For Forests (LFF) on the anti-logging side. It drew on a macro-level European theoretical approach (New Social Movement theory) and a US organizational approach (Resource Mobilisation Theory). The study also investigated the extent to which these two social movement organisations (SMOs) had been effective in influencing the development of State forest policy. For this purpose Schumakers (1975) framework for judging the political effectiveness of social movements was used. The key research problem investigated in this thesis is why these two SMOs continued to debate the forest policy issue after more than 30 years of public controversy?
Interviews with a key range of stakeholders were the key research method of this study. Additionally, an investigation into important economic and social changes in the south west was undertaken using census and other data between 1971 and 2001 and this was supported by an historical analysis of the timber industry in WAs south west. Finally, a 3-year study of the reporting of forest issues by two local and one national newspaper was completed. The 1998-2000 period was chosen for the newspaper analysis as this was when the new Regional Forest Agreement was being finalised.
This research shows that new values toward the old-growth forests developed among the WA public over the past 30 years and this has created an unbridgeable policy gap between those such as the TCA who wanted the past policies to continue and those such as the LFF who wanted to preserve the remaining native forests. ABS data confirm that the south-west region of WA changed dramatically between 1970 and 2000 as the wine and tourism industries developed and that these changes were different to those occurring in the other wine regions and non-city areas of Australia. As the population increased in this region, a key segment attracted by these new employment opportunities were middle class, well-educated people with new values toward the natural environment.
The interview and newspaper article data clearly showed that the debate in WA in the late 1990s over the proposed RFA provided a new political opportunity for the anti-logging movement to raise their concerns and to establish a renewed public debate about the appropriateness of the WA forest policies. This came at a time when the traditional policy power of the timber industry stakeholders and the government department in charge of the forests (Conservation And Land Management) had been dramatically diminished. The combination of these factors led to the election of the new ALP government and the introduction of a new, non-logging policy for WAs old-growth native forests.
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au, j. anderson@murdoch edu, and 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.
Abstract:
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.
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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.
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Vrdoljak, Sven Michael. "The conservation value of habitat remnants for flower visiting insects in the lowlands of the Cape Floristic Region." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5280.
Abstract:
Thesis (PhD(Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: See full text document for abstract
AFRIKAANSE OPSOMMING: sien volteks dokument vir die opsomming
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Stenhouse, Renae N. "Ecology and management of bushland in Australian cities." University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0027.
Abstract:
[Truncated abstract] Native vegetation (bushland) in urban areas remains in small, isolated patches embedded within a matrix of human-dominated land uses. Bushlands in urban areas have high biodiversity conservation and social values, and there has been a local-level movement towards protecting and managing urban bushlands in Australia. This thesis aims to test principles, theories and concepts relating to the ecology and management of bushland fragments in Australian cities ... A commonly used qualitative scale was compared with an ecologically based, quantitative technique developed in the research. The qualitative scale was found to be a reliable proxy for assessing vegetation condition, while also being more user-friendly for community groups and other bushland managers. The human-caused disturbances and weed cover in urban bushlands indicate a need for management intervention. Local government has an important role in local biodiversity management, yet there has been little research on this topic ... Positive partnerships developed where local governments have taken a ‘contract model’ approach to volunteer coordination, have a number of expectations of volunteer groups, and provide the groups with relatively high level of assistance. Also important is a local government that supports, respects, trusts and communicates with the community group, and recognises volunteers’ skills, knowledge and contributions. With increased resources allocated to local government bushland management and conservation, and coordination with community groups, the full potential of local bushland management would be realised.
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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.
Abstract:
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.
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Jackson, Tania. "Occurrence and variation of Endothiella eucalypti in Eucalyptus globulus plantations of south-western Australia and the influence of some biotic and abiotic factors on the response of the host to the pathogen /." Access via Murdoch University Digital Theses Project, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20061129.132615.
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Otto, Mia. "Spatial and temporal changes in Fynbos riparian vegetation on selected upland rivers in the Western Cape." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86603.
Abstract:
Thesis (MScConEcol)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Restoration practices commonly make use of a reference condition in order to restore a site to a better ecological state than it is currently in. The selection process and relevance of the reference condition has not yet been tested in upland Western Cape rivers especially with relation to spatial and temporal scales. This thesis sought to evaluate whether space (longitudinal) and time (temporal) influence riparian plant community composition (laterally), how it influences the community composition and whether these differences impacts the selection of a reference condition used in restoration practices. In order to investigate the role longitudinal position, sites were selected across three longitudinal zones: mountain stream, transitional and upper foothills. Historic sites used in a previous study on riparian vegetation of upland rivers were resampled and datasets used for temporal comparisons between undisturbed sites, sites recovering after clearing of invasive alien plants and sites affected by fire. Riparian vegetation communities showed differences between longitudinal zones, basins and rivers. The species responsible for marginal zone identity (plants in close proximity to the active channel), determined using relative cover abundance varied, with Isolepis prolifera responsible for the group identity in the mountain stream and transitional sites but in the foothills Calopsis paniculata, Drosera capensis and Metrosideros angustifolia saplings were responsible for lateral zone identity. The lower dynamic (transitional between wet and drybank) had no similarities between different longitudinal zones across rivers. In the lower zone Pteridium aqualinum was mostly responsible for the identity. The upper bank had no single species responsible for group identity. The species described to be typical for the reference condition on these particular rivers by other studies were mostly present in the comparable lateral zone but it was however not always responsible for the identity of the specific lateral zone. By comparing selected environmental variables such as horizontal distance from active channel, elevation and substrate calibre with different longitudinal zones’ riparian vegetation species distribution, different combinations were produced. The mountain streams showed the strongest relationship with horizontal distance and elevation in combination to one another and the upper foothills horizontal distance from the active channel was linked most strongly to vegetation positioning. These results confirm the importance of space when attempting to assess, study or restore riparian communities. Temporally, sites had stronger similarity to data collected during the same sampling period than with historic data. Also, the overall relative species abundance did not show significant change to be present at a site scale. The changes in community composition were found to be due to a lateral zone scale variation in species abundance. As expected the undisturbed rivers showed less variation in species responsible for temporal changes than the recovering and fire-exposed rivers. Species responsible for changes in relative abundance at a lateral zone scale were Metrosideros angustifolia, Morella serrata, Brabejum stellatifolium, Isolepis prolifera, Elegia capensis, Prionium serratum and Calopsis paniculata. Due to the species diversity not changing much temporally but the relative abundance of specific species showing much variation over time it can be concluded that the changes are not diversity based but instead driven by changes in relative abundances of species typical for a lateral zone. The spatial and temporal variation in riparian vegetation community composition was found to be significant enough to suggest that the use of a fixed reference condition for all Western Cape rivers would not be feasible due to clear differences between basins. Secondly when selecting a reference site the spatial location of this site should be within the same longitudinal zone since bank shape does influence riparian plant species distribution. Finally the temporal comparison between sites showed high diversity in species abundances but small differences in diversity overall. This would suggest that a general community description specific to 1) where the site is situated and 2) based on the present riparian vegetation community composition within a specific basin may be more realistic and achievable for restoration and environmental management purposes as opposed to using site descriptions from the past and reference sites too far upstream or downstream from the restoration site.
AFRIKAANSE OPSOMMING: Herstel praktyke maak algemeen gebruik van 'n verwysing toestand om 'n terrein te herstel na 'n beter ekologiese toestand as wat dit tans is. Die keuringsproses en relevansie van die verwysing toestand is nog nie in die boonste gedeeltes van Wes-Kaap Riviere getoets nie, veral met betrekking tot ruimtelike en tydskale nie. Hierdie tesis het gesoek om te evalueer of ruimte (longitudinaal) en tyd (temporaal) rivieroewers plant gemeenskap samestelling (lateraal) beïnvloed en of hierdie verskille die keuse van 'n verwysing toestand in die herstel praktyke beïnvloed. Ondersoek terreine was oor drie longitudinale sones geselekteer: berg stroom, oorgangs en boonste hange terreine. Historiese terreine was weer ondersoek en die datastelle was gebruik vir die temporale vergelykings tussen onversteurde terreine, terreine wat herstel na die skoonmaak van indringer spesies en wat geraak was deur 'n brand. Oewerplantegroei gemeenskappe het verskille tussen longitudinale sones, rivier-kom en rivier takke gewys. Die spesies wat verantwoordelik was vir marginale zone (plante in nabye afstand met die aktiewe rivier kanaal) identiteit, bepaal met behulp van relatiewe dekking hoeveelheid, het gevarieer met Isolepis prolifera verantwoordelik vir die groep identiteit in die berg stroom en oorgangs trerreine, maar in die boonste hange was dit Calopsis paniculata, Drossera capensis en Metrosideros angustifolia boompies wat verantwoordelik was vir die laterale sone identiteit. Die laer dinamiese area het geen ooreenkomste tussen marginale gebiede van verskillende longitudinale sones gehad nie. In die onderste sone was Pteridium aqualinum meestal verantwoordelik vir die groepering se identiteit. Die boonste bank het nie 'n enkele spesie wat verantwoordelik was vir die groep identiteit gehad nie. Die spesies beskryf as tipies vir die laterale sone deur Reinecke et al. (2007) was meestal teenwoordig in die beskryfde laterale sone van hierdie studie, maar dit was egter nie altyd verantwoordelik vir die identiteit van die laterale sone gemeenskap nie. Verskillende lengte sones het gekorreleer met verskillende omgewingsveranderlikes wat sterkste gekoppel kon word aan die verspreiding van spesies. Die bergstrome het die sterkste verhouding met horisontale afstand en hoogte in kombinasie met mekaar gehad en in die boonste hange was horisontale afstand van die aktiewe kanaal die sterkste gekoppel aan plantegroei posisie. Die belangrikheid van ruimte is onmiskenbaar ten opsigte van evaluering, bestudering en die herstel van rivieroewers gemeenskappe. Terreine het sterker ooreenkoms met data gehad wat tydens dieselfde tydperk versamel was, as met historiese data. Die algehele relatiewe spesies hoeveelheid het egter nie beduidende verandering getoon op 'n terrein skaal nie. Soos verwag was het die onversteurde riviere minder temporale variasie in spesies getoon as die herstellende en brand blootgestelde riviere. Spesies wat verantwoordelik was vir die verandering in relatiewe hoeveelhede op 'n laterale sone skaal was M. angustifolia, Morella serrata, Brabejum stellatifolium, I. prolifera, Elegia capensis, Prionium serratum en C. paniculata. As gevolg van die diversiteit van spesies wat nie baie verander het tydelik nie, maar die relatiewe hoeveelheid van spesifieke spesies wat heelwat variasie oor tyd getoon het, kan dit afgelei word dat die veranderinge nie diversiteit gebaseerd was nie, maar eerder gedryf was deur veranderinge in relatiewe hoeveelhede van tipiese spesies in 'n laterale sone. Die ruimtelike en tydelike variasie in oewerplantegroei gemeenskap samestelling was beduidende genoeg om voor te stel dat die gebruik van 'n vaste verwysing toestand vir alle Wes-Kaapse riviere nie haalbaar sou wees nie as gevolg van duidelike verskille tussen riviere. Tweedens, by die kies van 'n verwysing terrein moet die ruimtelike plek van hierdie terrein in dieselfde lengte sone wees aangesien bank vorm 'n invloed op rivieroewer plant verspreiding het. Laaastens, het die tydelike vergelyking tussen terreine hoë diversiteit in spesies verspreidings maar klein verskille in algehele diversiteit gehad. Dit stel voor dat 'n algemene beskrywing van die gemeenskap wat spesifiek op 1) waar die terrein geleë is en 2) gebaseer op die huidige oewerplantegroei gemeenskap samestelling binne 'n spesifieke rivier netwerk dalk meer realisties en haalbaar vir hersteel en bestuurs doeleindes sou wees. Hierdie benadering word verkies bo die gebruik van n terrein beskrywings uit die verlede en verwysing terreine te ver stroomop of stroomaf van die herstel gebied.
44
au, B. Bradshaw@Timbercorp com, and Ben Philip Bradshaw. "Physiological aspects of Corylus avellana associated with the French black truffle fungus Tuber melanosporum and the consequence for commercial production of black truffles in Western Australia." Murdoch University, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060327.92530.
Abstract:
The black truffle (Tuber melanosporum Vitt.) industry in Australia is relatively new and has enormous potential but some truffières (truffle farms) fail to meet anticipated harvest projections. Inappropriate soil conditions and climate, and the management of such factors are suggested as the primary reasons for inadequate yield. In addition, requirements for ascocarp initiation and development and the role of the host plant in such processes are unknown. This study examines interactions between European hazel (Corylus avellana L.) and the ectomycorrhizal (ECM) black truffle symbiont in a commercial truffière (Hazel Hill) in south-western Australia. Specific studies were initiated to examine the interactions of host physiology, mycorrhizal infection and the interaction with abiotic factors. The study related specific physiological processes of the host plant to the known life cycle of the black truffle to determine the role of the host plant in ascocarp production, if any. The work also examined the effect of silvicultural treatments intended to increase truffle production.
A review of existing literature was undertaken to determine the key soil and climatic factors required for successful truffle production. Climatic conditions appeared more important than soil chemistry and structure in Western Australia, with significant seasonal variation in air and soil temperatures required plus irrigation to supplement summer rainfall. This information was used to define areas with potential for truffle production in the south-west of Western Australia: the cooler, high rainfall regions (>1000 mm annual rainfall) where there is sufficient seasonal variation in soil temperature and availability of adequate quantities of quality water for irrigation. Subsurface soil acidification and salinity, as well as groundwater salinity, are constraining factors. Lime amendment is necessary to create sufficiently high pH and CaCO3 levels required by the truffle fungus.
A field trial was established to monitor the seasonal C dynamics of European hazel in the context of the life cycle of the black truffle. Maximum translocation of sucrose in the phloem sap coincided with the period of anticipated rapid growth of the truffle ascocarp implicating the use of current photosynthate in C nutrition of the ascocarp. Sampling of non-structural carbohydrates (NC) of above and belowground plant material indicated maximum storage of C in the host coincides with maturation of the ascocarp. These observations provide evidence of a synchronous growth habit of the plant host and the ascocarp.
The C allocation patterns of European hazel in response to liming a loamy soil, taken from near the Hazel Hill truffière, and inoculation with ECM fungi (T. melanosporum, Hebeloma sp. and Scleroderma sp.) were examined in a glasshouse pot trial. Liming increased biomass allocation to the shoot and induced deficiencies of phosphorus and manganese. Colonisation by ECM fungi significantly increased net photosynthesis, indicating the sink strength of these fungi, but there was no relationship between the level of mycorrhizal infection and fine root NC. The maximum rate (40 g lime kg-1 soil) reduced infection by Hebeloma and Scleroderma and had no impact on T. melanosporum. Further, infection rates of T. melanosporum did not increase in response to lime suggesting lime is not necessary for ECM development in this soil type.
Fertiliser is widely used in commercial truffières in Australia but the consequences for truffle production are unknown. In a field trial, the growth and physiological response of European hazel to forms of phosphorus (34 and 68 kg ha-1 apatite-P and 68 kg ha-1 triple super phosphate -P) and nitrogen (50 kg ha-1 of NO3- and NH4-N) were examined as well as the mycorrhizal response to fertiliser. Apatite-P increased phloem sap sucrose concentrations which was attributed to increased root biomass and associated sink capacity. Fertiliser application did not change fine root NC concentrations suggesting no increase in allocation of C to ECM structures. The highest rate of apatite-P decreased mycorrhizal infection rates of T. melanosporum and, most likely, was the result of increased infection rates of Hebeloma. In contrast to the literature relating to indigenous Australian ECM fungi, the highest rate of soluble-P did not decrease ECM infection rates in T. melanosporum. Nitrogen treatments increased foliar N content and improved gas exchange efficiency of plants, and had no adverse impact on the level of ECM infection. Fertilisation with N significantly increased soil respiration rates suggesting N limits mineralisation at this site.
Some truffières manage the canopies of the host tree to ensure maximum exposure of the soil surface in order to increase soil temperatures. As there are no published data on the effect of pruning on black truffle production, a field trial was established to document the impact of canopy pruning on host physiology and soil temperature. The removal of 65% of canopy leaf area reduced phloem sap sucrose concentrations, soil respiration rate and the soluble: insoluble NC ratio of fine roots in the short term (1-3 weeks). There was no compensatory response of leaf gas exchange parameters as a result of pruning. Generally, there was no long term impact on plant physiological parameters as a result of pruning. Long term effects on soil temperature were observed as a result of pruning. Mean annual temperature and amplitude increased significantly beneath pruned trees and spring, summer and autumn soil temperatures increased as did diurnal variation as a result of pruning. Pruning did not increase winter soil temperatures and therefore would probably not impact on ascocarp maturation during this period.
This research has provided insight into the C physiology of hazel associated with the black truffle and the consequences for truffle production. The results provide anecdotal evidence of direct C transfer between the host and the developing truffle, contrary to the existing paradigm that the ascocarp is saprotrophic for the majority of its growth and development. There is a need to validate this finding as there are consequences for management of commercial truffières. Liming of loam duplex soils can reduce the abundance of the most common competitor ECM fungi and should be encouraged in commercial truffières. Applying phosphorus and nitrogen to commercial truffières will improve growth rates of planted trees without adversely impacting on ECM infection by black truffle fungi, although the impact on truffle production remains unknown. It is anticipated truffle production will improve in the longer term as a result of pruning and prudent canopy management. Management options should include tree removal to reduce planting density and increase soil exposure in truffières. There is a need for longer term trials to be established to determine the C nutrition of the truffle ascocarp and to clearly define the key stages of the black truffle life cycle in Western Australia.
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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.
Abstract:
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.
46
Snyder, Melissa. "Ecological and Genetic Variation Among Populations of Boechera caeruleamontana sp. nov. (Brassicaceae) from Blue Mountain and Dinosaur National Monumentin Eastern Utah and Western Colorado." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6344.
Abstract:
Boechera is a large genus of flowering plants whose taxa are found primarily in North America. Boechera vivariensis (S.L. Welsh) W.A. Weber (the Park rockcress) is restricted to the Uintah Basin on Weber sandstone substrates in the vicinity of Dinosaur National Monument and Blue Mountain. The nomenclature of Park rockcress is significantly impacted by the discovery that the type collections of the taxon represent a rare, apomictic diploid resulting from the hybridization between B. thompsonii and an undescribed sexual diploid (to be called Boechera caeruleamontana sp. nov. Allphin and Windham). As a result, greater information is needed regarding how B. vivariensis and B. caeruleamontana. are distributed geographically in the region of Dinosaur National Monument and surrounding areas. Thus, we performed genetic analyses on leaf samples taken from over 50 individuals at known sites of B. vivariensis throughout its geographic range. Individuals from each site were also compared morphologically. We also compared associated plant communities at each site and characterized the soils. In our thorough sampling, we did not pick up B. vivariensis. All individuals sampled belonged to B. caeruleamontana, suggesting that most individuals previously assigned to B. vivariensis, are actually representative of B. caeruleamonanta. Populations of B. caeruleamontana were genetically diverse compared to other Boechera species, most likely indicative of its insect pollination strategy. However, all populations had lower heterozygosity than expected based upon Hardy-Weinberg expectations. Reproductive and genetic data indicated that populations are showing signs of inbreeding. The population at Jones Hole Fish Hatchery was most unique genetically, morphologically, and reproductively.
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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.
Abstract:
[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.
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George, Amy Kathryn. "Eucalypt regeneration on the Lower Murray floodplain, South Australia." Connect to this title online, 2004. http://hdl.handle.net/2440/37706.
Abstract:
Vegetation along the River Murray floodplains has been shown to be in a severe state of decline. This decline is amplified by the impositions of river regulation. In South Australia, where vegetation losses have been great, regeneration is limited and may result in not only individual tree losses but also widespread population decline. This study aimed to examine the relationship between river flows and the regeneration process in populations of Eucalyptus camaldulensis and Eucalyptus largiflorens. The current structure of the populations was examined to determine if a viable number of varying age-classed trees were present. Tree surveys conducted at Banrock Station determined that while densities were low for both species, E. camaldulensis had a more sustainable population structure than E. largiflorens. Growth stages for both species illustrated highly clumped distribution, which is believed to correspond with river flooding magnitudes and frequencies. To address the potential link between tree distribution and flooding within the River Murray, a hydrological analysis was conducted for Banrock Station using river flows at the South Australian border from 1900 to 2003. The amount of time growth stages for each species were inundated was found to be greatly reduced under regulated flows compared to natural flows. This has resulted in shifted localized regeneration patterns corresponding with E. camaldulensis' greater demand for inundation than E. largiflorens. Moderate magnitude flows have been most impacted by regulation, and consequently these are the very flows needed for floodplain tree population maintenance. Flowering and seed fall for E. camaldulensis and E. largiflorens were monitored at Banrock Station for 22 months to identify losses in reproductive potential resulting from tree decline. While seed viability was not affected by vigour, trees with visually reduced vigour were found to produce less fruit and had reduced seed fall, as well as a reduced rate of fruit development. Dendrochronological techniques were applied to floodplain trees. Age and size relationships could be established, implying that such techniques can be applied in South Australia to high quality sites. Growth responses within cohorts were similar and easily matched between individuals illustrating cyclic, but not necessarily seasonal correlations. This work verified the preferential selection of younger trees for dendroecological studies, and identified a relationship between on moderate flows and measurable girth expansion in both floodplain tree species.Thesis (Ph.D.)--School of Earth and Environmental Sciences, 2004.
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Kurzweg, Sabine Eva Maria Johanna. "Standardizing quarter degree grid data for plant species in the Western Central Bushveld for more explicit use in spatial models / Sabine Eva Maria Johanna Kurzweg." Thesis, North-West University, 2011. http://hdl.handle.net/10394/9516.
Abstract:
South Africa is a megadiverse country, and its biodiversity is endangered by population pressure and the development needs of a developing country. In order to address the rapid decline in biological diversity, biodiversity planning has become a key focus area that aims at identifying priority areas for species and ecosystem conservation within and outside of formally protected areas. Plant conservation hotspots are identified by the quantification of indicator taxa such as plant taxa richness, rarity and endemism. But the urgent and enormous task of biodiversity assessment for conservation planning requires that we make most of what we know. Therefore, this study seeks to make a contribution by finding new ways of biodiversity pattern estimation from the extrapolation of incomplete sets of plant species distribution data at the Quarter Degree Grid level. Incomplete sampling across the grids of a study area results in false records of species absence and thus a biased biodiversity estimation. As a possible solution, plant distribution data for the western Central Bushveld Bioregion has been standardized using two profiles, namely the ‘Centroid Grid’ and ‘Integrated Grid’ profile. The former involves the strengthening of under-sampled grids by extrapolating species occurrences from three adjacent grids with the most similar vegetation units, whereas the latter integrates phyto-diversity data for the four grids intersecting at each grid reference point. Standardized data has proved to provide a means to counter the bias in plant diversity data linked to Quarter Degree Grids by a) strengthening of under-sampled grids and b) visibly smoothing out the gaps between under- and well-sampled grids, which resulted in improved biodiversity estimation for more representative spatial biodiversity modelling. Interpolation created geo-referenced polygons for more explicit use in the identification of areas of conservation concern at bioregional scale. However, well-sampled grids still dominate the outcomes of the analysis by creating spatial sampling bias. Therefore, this approach to calibrate Quarter Degree Grid resolution of spatial data is an additional attempt to achieve more representative mapping of biodiversity patterns, which is a prerequisite for strategic conservation planning for ‘living landscapes’.Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012
50
Heliyanto, Bambang. "The ecological genetic consequences of local endemism and natural population fragmentation in Banksia ilicifolia (Proteaceae)." University of Western Australia. School of Plant Biology, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0123.
Abstract:
[Truncated abstract] The species-rich Southwest Australian Floristic Region (SAFR) is a global biodiversity hotspot. Characterised by a Mediterranean-type climate and nutrient deficient landscape, this region is endowed with 7380 native vascular plant species/sub species, of which 49% are endemic and 2500 are of conservation concern. Despite the global significance of this region, there is still only a poor understanding of the factors influencing high diversity and endemism, and especially the population genetic consequences of narrow endemism and naturally fragmented species distribution. Holly leaved banksia (Banksia ilicifolia R. Br.), although widespread through Southwest Western Australia (SWWA), has a naturally fragmented distribution, with generally small populations restricted to swales and wetland fringes with depth to groundwater less than 10 m. As such, it provides an excellent model to better understand the ecological genetic consequences of local endemism, population size and natural population fragmentation . . . Products of wide outcrossing (over 30 km) showed a heterosis effect over local outcrossing, indicating increased ecological amplitude of offspring following interpopulation mating. These results suggest that the breeding and mating biology of B. ilicifolia counters the negative genetic erosion effects of narrow ecological amplitude and small population size. Recent habitat fragmentation, and reductions in population size and increased isolation, is impacting on these processes, but further research is required to assess the ultimate consequences of these genetic effects for population viability.