Dissertations / Theses on the topic 'Sub-tropical'
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Engelbrecht, Nicolaas Carel Marthinus. "Foggage value of sub-tropical grasses." Diss., University of Pretoria, 2002. http://hdl.handle.net/2263/28505.
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The use of foggage as winter feed for animal maintenance is unlikely to totally replace hay and/or silage, but should be used as an alternative for the early winter. The most important objective in producing foggage is to feed animals to at least maintain body weight through the winter season. As foggage is generally not a high quality feed, it usually can not be used for producing animals without supplementation. Using foggage can also mininise expensive inputs, such as labour and machinery. This is the single most outstanding advantage of using pasture foggage over hay, haylage, crop residues or silage. Although pastures also have establishment and fertilizer costs, these are less than costs associated with intensive annual crops. Many pastures are also perennial, which means less establishment costs. This emphasises the importance for less intensive farming systems. Depending on what the objectives of the farmer are, he can manage foggage to produce a high yield with a lower quality or vice versa. Thus it is critical to maintain a balance between yield and quality. Foggage quality was inversely related to the growing season after the pasture was closed-up and thus the quality will be lower with earlier closing-up time. Fertilisation, especially with nitrogen, will increase the nutritive value of the product (6% - 12%CP). The aim of this study was to determine which pasture provides the best foggage in different scenarios. The conclusion is, therefore, that a farmer must first decide on his management plan and where his foggage will fit in. Then it is recommended to choose the species (or accession) that is best adapted to his specific area of farming. Silk sorghum and Coastcross II had the best yields recorded. Smutsfinger grass was very palatable, had high digestibility and would, therefore, be recommended for quality in the higher rainfall eastern parts of the country. Because of their drought resistance, Molopo and Kleingrass will be recommended for the warmer areas with less rainfall and Molopo especially for small farmers who lack overall grazing management skills or infrastructure.Dissertation (MSc (Agric) Pasture Science)--University of Pretoria, 2002.
Plant Production and Soil Science
unrestricted
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Bakmeedeniya, Lekha Udayanganie. "MODELLING POLYGENERATION WITH DESICCANT COOLING SYSTEM FOR TROPICAL (AND SUB - TROPICAL) CLIMATES." Thesis, KTH, Energiteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-43253.
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Modelling Polygeneration with Desiccant Cooling System for Tropical(and Sub Tropical) ClimatesAbstractSpace cooling has become a necessity in tropical countries. Maintainingcomfortable indoor conditions in industrial environments incur high energy bills due toheavy dependency on electrically operated air conditioning systems. In order to exploreways and means to improve the energy efficiency and alternative energy resources, afeasibility study was conducted using a transient simulation software TRNSYS toimplement a combined cooling, heating and power system suitable for a tropicalcountry.It is proven from the literature search that desiccant dehumidification inconjunction with evaporative coolers can reduce air conditioning operating costssignificantly since the energy required to power a desiccant cooling system is small andthe source of this required energy can be diverse.(Low exergy heat such as solar, wasteheat and natural gas)This research is conducted to evaluate the performance and applicability ofdesiccant cooling systems under tropical climatic conditions. Two operating modes;ventilation and recirculation modes of solid desiccants based open cycle air conditioningthat use waste heat from a CHP plant are analysed to understand their operatingranges, performances and applicability. The model developed is used to propose asuitable desiccant cooling system for a selected industry environment in Sri Lanka.Preliminary results obtained by a parametric analysis for weather data for Colombo, SriLanka shows 0.95 and 1.02 optimum coefficients of performance for the ventilation andrecirculation modes respectively when heat is available at 85°C. Based on thecomparisons of the analysis it is seen that the desiccant cooling appears to be a logicalsupplement for space cooling applications in tropical climates like Sri Lanka. And for thecase study taken to investigate can be proposed with a desiccant cooling system with ahot water storage as the energy supply and it can maintain a COP of about 0.48 undertropical weather conditions.
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Al-Yazeedi, Saleh Ali Bin Shiekhan. "Epidemiology of foot infection in a sub-tropical climate." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286319.
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Newham, Michael John. "Nitrate Retention and Removal in Sub-Tropical Riparian Zones." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/366141.
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Worldwide, contamination of streams and groundwater with excess nitrate has been linked to agricultural land use and particularly to the application of nitrogen fertilisers to increase agricultural production. Nitrate is an effective contaminant in agricultural areas; it is highly mobile, having a low affinity for soil sorption, and so moves with runoff and sub-surface flows. Excess nitrate can cause ecological impacts on waterways and coastal receiving water through eutrophication and, in some cases, contributes to coastal ‘dead zones’. Nitrate also has toxicological effects on aquatic organisms and those using contaminated water as a drinking source. Riparian zones, those zones where interaction of aquatic and terrestrial environments occurs, are identified as areas of intense biogeochemical cycling and can act as buffers against excess nitrate by reducing the amount of nitrate reaching stream channels. Nitrate retention processes of biotic uptake and transformation to less mobile forms can increase the residence time of nitrate within the riparian zone, while removal processes of denitrification can permanently remove nitrate-nitrogen in gaseous forms.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Breedt, Machiel Christoffel. "Gold exploration in tropical and sub-tropical terrains with special emphasis on Central and Western Africa." Thesis, Rhodes University, 1996. http://hdl.handle.net/10962/d1005578.
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The aim of this dissertation is an attempt to' provide a general guide for future gold exploration in tropical and sub-tropical terrains. The dissertation includes a brief discussion of the various exploration techniques used in regional and local exploration. This provide the necessary background knowledge to discriminate between the constraints and applications and to be able to select the techniques which are more suitable for gold exploration in tropical and sub-tropical terrains. Weathering, gold geochemistry and soil formation, fields often neglected, are emphasized to illustrate the importance of the mobility and dispersion of gold in the weathering of the lateritic soil profile. A sound knowledge and experience in regolith mapping is to the advantage of the explorationist. Case studies with special emphasis on Central- and Western Africa are included to illustrate the effectiveness of some of the gold exploration techniques in tropical and sub-tropical terrains. Gold exploration is a highly complex and demanding science and to be successfull involves the full intergration of all geological, geochemical and geophysical information available. An intergrated exploration method and strategy would enhance the possibility of making viable discoveries in this highly competative environment where our mineral resources become more depleted every day. Where applicable, the reader is refered to various recommended literature sources to provide the necessary background knowledge which form an integral part of gold exploration.
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Boucek, Ross E. "Investigating Sub-tropical Community Resistance and Resilience to Climate Disturbance." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2993.
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Changes in global climate will likely increase climate variability. In turn, changes in climate variability have begun to alter the frequency, intensity, and timing of climate disturbances. Continued changes in the climate disturbance regime experienced by natural systems will undoubtedly affect ecological processes at every hierarchical scale. Thus, in order to predict the dynamics of ecological systems in the future, we must develop a more mechanistic understanding of how and in what ways climate disturbance affects natural systems. In South Florida, two climate disturbances recently affected the region, a severe cold spell in 2010, and a drought in 2011. Importantly, these disturbances affected an ecosystem of long-term, comprehensive, and persistent ecological study in the Shark River estuary in the Everglades National Park. The aims of my dissertation were to (1) assess the relative severity of these two climate disturbances, (2) identify effects of these disturbances on community structuring, (3) compare community change from the 2010 cold spell with community change from another extreme cold spell that affected sub-tropical China in 2008, (4) assess the effects of the drought on predator prey interactions in the Shark River and (5) apply a spatial approach to predicting population resistance to these events. My results show that the 2010 cold spell was the most severe cold event to affect the Shark River in the last 80 years, while the drought was the worst drought to occur in the last 10 years. The cold spell drove community change that was predictable based on the traits of component species, whereas community change was less predictable using trait-based approaches. When comparing community change from the extreme 2010 event in Florida with the event in China, I identified three consistencies related to community change from extreme cold events that occurred across both events that will help build generalized understanding of community resistance to increasingly extreme climate events in the future. From the trophic study, I found that the drought reduced prey for estuarine piscivores. Not only was prey biomass reduced, the drought drove a compositional shift in prey communities from fish to invertebrates, which are lower in calories. Last, I found that animal movement may create temporally dynamic resistance scenarios that should be accounted for when developing predictive models.
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Walkington, Ian A. "Wind and bouyancy driven models of sub-tropical ocean gyres." Thesis, Keele University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397658.
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Paul, Miriam. "Restoring Rainforest – the Capacities of Three Different Reforestation Pathways to Re-establish Ecosystem Properties." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/366066.
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The broad scale destruction of tropical and subtropical rainforests has been one of the largest land-cover conversions taking place on earth, with a wide range of deleterious consequences at local, landscape, and global scales. While the resulting loss of biodiversity and habitat for rainforest-dependent fauna and flora has been well-studied as a major effect, clearing of rainforests also significantly influences soil processes such as biochemical cycles and microbial functions. More recently, there has been a growing public interest in reforestation activities. There are a range of different pathways by which rainforest cover can be restored to cleared land, including autogenic, or „natural‟, regrowth, management of this autogenic regrowth, and tree planting for ecological restoration. However, little is known about the recovery processes of ecosystem properties under different reforestation pathways in the same landscape. The broad objective of this thesis was to assess both the effects of deforestation on a range of ecosystem processes and the potential of different reforestation pathways to restore these processes. The study was conducted in the Big Scrub area in subtropical eastern Australia, a basaltic plateau that once supported the continent‟s largest continuous stand of lowland subtropical rainforest, which was mostly cleared for pasture in the mid to late 19th century. In this landscape, the properties of five site-types were compared, with five replicate sites in each. The site-types consisted of two reference conditions, pasture and intact rainforest, and three different reforestation pathways. These pathways were: autogenic regrowth dominated by the non-native tree species camphor laurel (Cinnamomum camphora); similar regrowth managed in order to remove the camphor laurel and release the growth of recruited rainforest seedlings; and ecological restoration plantations. Camphor laurel is a dominant species in the Big Scrub region, where it readily colonises abandoned pastures and is known to facilitate the recruitment of later successional rainforest tree species. In ecological restoration plantings, a high diversity of native rainforest tree seedlings is planted to restore biodiversity. The main ecosystem properties studied within the sites were as follows: 1. size and composition of viable soil seed banks; and 2. soil physical properties and nutrient cycles. This study also assessed the consequences of altered soil properties and nutrient dynamics for the early growth of rainforest pioneer seedlings. To assess the effects of deforestation and reforestation on soil seed banks, germination experiments were conducted using soil from all five site-types (three reforestation pathways, pasture, and rainforest sites). Germination trays were positioned in a shade-house and seedling emergence was monitored over a period of six months. Germinated seedlings were classified into functional groups according to their life-form, origin, successional stage, and dispersal mode. Additionally, floristic data from a subset of the study sites was used to examine how the seed bank was related to the standing vegetation. Despite a much larger total abundance of seeds in seed banks from pasture sites, these sites contained very few native woody plants and were dominated by grasses and herbaceous species. Further, seed banks of reforested and rainforest sites were mainly composed of pioneer and early secondary species, whereas late secondary and mature phase species appeared almost solely in the standing vegetation. The abundance and diversity of most of the functional groups that were impacted by deforestation showed values similar to rainforest in at least one of the three reforestation pathways; whilst the three pathways differed only slightly in their capacities to restore soil seed banks. In the initial phases of reforestation, however, seed banks play no vital role after long-term pasture establishment. The effects of deforestation and reforestation on the physical and biochemical properties of soil were tested by measuring a range of properties in soil samples from all five site-types. The main emphasis was placed on carbon- and nitrogen-related soil properties, as they are major nutrients in terrestrial ecosystems. Before these data were collected, a study was performed in a subset of the sites to identify the variation of soil properties at different spatial scales (subplot, site, and site-type level) and to develop a spatial design for the collection of soil samples within sites. For each of the five site-types, two replicate sites were measured, with 16 subplots in each site. Subplots were seven cm in diameter and regularly aligned with a spacing of 10 m. The seven soil properties measured in this soil variability study were: gravimetric water content; soil organic matter; pH; total organic carbon; microbial biomass carbon; nitrate-nitrogen, and nitrification rate. Across all sites, water content, soil organic matter, and pH showed a consistently low variability at all three spatial scales. In contrast, soil properties related to microbial processes exhibited higher degrees of spatial variability at the site and the subplot level. However, even in soil properties with a high tendency for spatial variability, the physical mixing of subsamples from subplots within a site, in contrast to analysing subsamples individually, could be validated as a useful technique to reduce analytical effort and cost. In the main study of soil properties under deforestation and reforestation, 19 properties were measured at each of five sites in each of the five site-types (the same 25 sites used for the seedling germination experiment). These properties consisted of: eight nitrogen-related variables (total nitrogen (N), ammonium-N, nitrate-N, total inorganic N, plant-available ammonium-N, plant-available nitrate-N, nitrification rates, and denitrification rates); six carbon-related properties (total carbon (C), total organic carbon, soil organic matter, 13C value, microbial biomass carbon, and soil microbial activity); and five general soil properties (gravimetric water content, pH, bulk density, fine root biomass, and plant-available phosphate). Of the 19 soil properties, nine differed significantly between rainforest and pasture. Nitrate-N levels, plant-available nitrate-N levels, nitrification rates, and fine root biomass were significantly greater in rainforest than in pasture sites, while plant-available ammonium-N levels, 13C values, pH, bulk density, and plant-available phosphate concentrations showed greater levels in pasture sites. Apart from fine root biomass, all of these soil properties were re-established to a level similar to that in rainforest in at least one of the three reforestation pathways. However, the capacity to re-establish soil properties varied among the three reforestation pathways. For example, autogenic regrowth dominated by camphor laurel showed a good recovery of nitrification, ammonium, and phosphate levels, but did not significantly facilitate the re-establishment of nitrate-N and bulk density. The impacts of soil properties – and hence deforestation and reforestation – on early seedling development were tested by measuring the growth of rainforest pioneer seedlings in soils collected from the three different reforestation pathways, as well as from pasture and rainforest soils. Three species, Alphitonia excelsa, Guioa semiglauca, and Omalanthus nutans, all fast-growing pioneer species that are common in the Big Scrub region, were chosen for this study. The seedlings were kept in a shade-house over a period of about seven months, and height and diameter were measured at regular time intervals. Although the three species varied significantly in height and diameter growth, they responded similarly to the five site-types, with generally lower growth rates in untreated autogenic regrowth and higher rates in soils from all other site-types, including pasture. However, there was little evidence that seedling performance was directly influenced by soil properties. Across all three species and all 25 sites, seedling growth rates...Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Kavanagh, Lydia Jane. "An engineered ecosystem for environmentally sustainable wastewater treatment for remote tourist resorts in tropical/sub-tropical regions /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16958.pdf.
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Honey, David James. "Heme b in marine cyanobacteria and the (sub-) tropical North Atlantic." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/359063/.
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Heme b is the iron containing prosthetic group to an important pool of iron proteins known as the hemoproteins. Hemoproteins are functionally diverse, playing key roles in photosynthetic and respiratory electron transfer (e.g. cytochrome b6f, photosystem II, cytochrome bc1) among other fundamental biological processes. Heme b is the most naturally abundant heme structure, but data regarding hemes in the marine environment are limited. An investigation has been conducted to improve our understanding of heme b abundance in marine organisms through laboratory monoculture studies of three marine cyanobacteria grown under varying total iron concentration. The unicellular cyanobacteria Synechococcus sp. WH7803 was examined under three total iron concentrations: 12 nmol L-1 (low), 120 nmol L-1 (medium) and 1200 nmol L-1 (high). The marine diazotrophs (i.e. nitrogen fixers) Crocosphaera watsonii (WH8501) and Trichodesmium erythraeum (IMS101) were studied under six total iron concentrations between 0 and 120 nmol L-1. Cultures were analysed for heme b, chlorophyll a, particulate organic carbon (POC) and particulate organic nitrogen (PON) concentration. Nitrogen fixation rates and biophysical measurements (Fv/Fm and σPSII) were also obtained for diazotroph cultures. Field data regarding the concentration of heme b, chlorophyll a, POC and PON as well as nitrogen fixation rates were collected during two research cruises in the subtropical North Atlantic (STNA, D346) and tropical North Atlantic (TNA, D361); an oceanographic region known to demonstrate high nitrogen fixation rates and receive significant dust (iron) deposition from the Saharan and Sahel deserts of Western Africa. Cultures of Synechococcus sp. WH7803 showed evidence of iron stress at low iron treatments via reduced maximum growth rates (μmax), total biovolume and chlorophyll a concentration. This was also reflected by a significant reduction in cellular heme b content per unit carbon (heme:C) at the lowest iron concentration. An estimated heme b requirement between 1.0 and 1.5 μmol mol-1 C is proposed for Synechococcus sp. WH7803 in order to facilitate μmax. Chlorophyll a to heme b ratios (chl:heme) were significantly decreased in low iron cultures of Synechococcus sp. WH7803, suggesting b-type hemoproteins were conserved when iron stressed. Cultures of Crocosphaera and Trichodesmium were similarly influenced by the availability of iron, with reduced total biovolume and chlorophyll a concentration reported at low iron treatments. However, heme:C ratios were maintained at approximately 1.5 and 0.5 μmol mol-1 C for Crocosphaera and Trichodesmium cultures, respectively. A high iron requirement is associated with marine diazotrophs relating to the iron-rich non-heme nitrogenase enzyme complex responsible for nitrogen fixation. Nitrogen fixation rates increased as total iron concentration increased, with Trichodesmium demonstrating four-fold higher rates than Crocosphaera at corresponding iron concentrations. It has been suggested that relatively low heme b contents of Trichodesmium cultures resulted from increased nitrogen fixation activity. Furthermore, heme:C ratios of Crocosphaera and Trichodesmium were typically lower than five eukaryotic phytoplankton previously investigated, potentially related to the allocation of iron for nitrogen fixation. Mean heme:C ratios from cruises in the STNA and TNA were 0.64 and 0.66 μmol mol-1 C, respectively. Results could imply the region was iron stressed and/or dominated by cyanobacteria. Evidence is also presented suggesting a possible inverse relationship between nitrogen fixation and heme:C ratio in the TNA which could be attributed to natural populations of Trichodesmium.
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Matla, Matsoele Moses. "Helminth ichthyo-parasitic fauna of a South African Sub-Tropical Lake." Thesis, University of Limpopo (Turfloop Campus), 2012. http://hdl.handle.net/10386/822.
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Thesis (Ph.D. (Zoology)) --University of Limpopo, 2012The diversity of the helminth parasites of fishes in a clear-water, subtropical Lake Tzaneen, in South Africa was investigated. Of the 527 fish specimens sampled approximately 9000 parasites were collected. There are 38 different parasite species discussed comprising 27 Monogenea, 3 Digenea, 4 Cestoda, 3 Nematoda and 1 Acanthocephala. Four new monogenean species are described and these are Dactylogyrus spp. 1 to 4. Three monogenean species are introduced as first records in Africa and these are Actinocleidus fusiformis (Mueller, 1934), Haplocleidus furcatus Mueller, 1937 and Acolpenteron ureteroecetes Fischthal & Allison, 1940. Fourteen monogenean and one acanthocephalan species are discussed as first geographical records for South Africa and these are Gyrodactylus rysavyi Ergens, 1973, Dactylogyrus brevicirrus Paperna, 1973, Dactylogyrus cyclocirrus Paperna, 1973, Dogielius dublicornis Paperna, 1973, Dogielius sp., Schilbetrema quadricornis Paperna & Thurston, 1968, Quadriacanthus aegypticus El Naggar & Serag, 1986, Quadriacanthus clariadis Paperna, 1961, Scutogyrus gravivaginus (Paperna & Thurston, 1969), Cichlidogyrus quaestio Douëllou, 1993, Cichlidogyrus halli Price & Kirk, 1967, Cichlidogyrus sclerosus Paperna & Thurston, 1969, Cichlidogyrus dossoui Douëllou, 1993, Cichlidogyrus tilapiae Paperna, 1960 and Acanthosentis tilapiae Baylis, 1948. Seven species are discussed as first records for their hosts and these are Cichlidogyrus dossoui, Cichlidogyrus halli and Acanthosentis tilapiae on Oreochromis mossambicus; Dactylogyrus sp. 1 on Barbus radiatus and Barbus trimaculatus; Dactylogyrus sp. 2 on Barbus unitaeniatus; Dactylogyrus sp. 3 and Dactylogyrus sp. 4 on Labeo molybdinus. Gyrodactylus rysavyi is the only species with a first site (gills) record. The other monogenean species discussed are Macrogyrodactylus clarii Gussev, 1961, Macrogyrodactylus karibae (Douellou and Chishawa, 1995), Dactylogyrus afrolongicornis afrolongicornis Paperna, 1973, Dactylogyrus allolongionchus Paperna, 1973, Dactylogyrus spinicirrus (Paperna & Thurston, 1968) and Cichlidogyrus philander (Douëllou, 1993). The digeneans discussed are Glossidium pedatum Looss, 1899 and the larvae of Diplostomum van Nordmann, 1832 and Clinostomum Leidy, 1856. The Cestodes discussed are Proteocephalus glanduligerus (Janicki, 1928) Fuhrmann, 1933, Polyonchobothrium clarias Woodland, 1925 and the larvae of Ligula intestinalis Goeze, 1782 and family Gryporhynchidae. The nematodes discussed are Procamallanus laevionchus (Wedl, 1861), Paracamallanus cyathopharynx Baylis, 1923 and larvae of Contracaecum Railliet and Henry, 1912. Monogenea were commonly found on the gills but less on the skin and in the urinary bladder. Digenea were found mainly in the eyes, brain and visceral cavity, with only one species (Glossidium pedatum) present in the intestines of Clarias gariepinus. Cestoda and Nematoda were found in the intestine and body cavity. Only one species of Acanthocephala (Acanthosentis tilapiae) was found in the intestines of Oreochromis mossambicus. No definite seasonal variations of infection and parasite affinities towards the sexes and the sizes of the hosts could be determined. The lake is oligotrophic with the water quality having no influence on the parasite diversity and species richness.
the University of Limpopo Research Office, and the National Research Foundation
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Bai, Shahla Hosseini. "The Impact of Site Management Practices on the Revegetation of Highly Disturbed Sites in Sub-Tropical and Tropical Queensland." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/366823.
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Revegetation schemes are increasing in Australia and are part of strategy to restore cleared lands, enhance biodiversity and alleviate global climate change. Site preparation practices play a pivotal role in the successful establishment of revegetation projects in tropical and sub-tropical Australia. However, site preparation practices are costly and there is great interest to develop cost-effective establishment methods. The most common site preparation practices, in Australia, include weed control and fertilisation. Reduced weed competition is a crucial factor in the successful establishment of revegetation projects. Herbicide application is the most commonly used method of weed control but need for repeated site visits and sequential applications greatly increase establishment costs. Alternative methods are sought to reduce the reliance on herbicide application. One such method is scalping, the removal of the top 100 mm of soil from the planting area which effectively removes the soil seed bank. Both herbicide and scalping have implications for soil properties which could in turn affect early plant growth and establishment. This study aimed to investigate the dynamics of soil organic matter (SOM), carbon (C) and nitrogen (N) pools under differing site preparation practices and the associated effects on plant survival, growth and eco-physiological status in tropical and sub-tropical Australia.
Two experimental sites located at Rockhampton (23º31'24 S, 150º18'14 E) and Laidley (27º40'31 S, 152º24'04 E) were established in this study. The treatment layout was randomised complete block split plot. Treatments included topsoil removal (scalping) and herbicide application for weed control. Other treatments included the use of fertiliser to overcome the potentially negative effects of scalping and to give a competitive advantage to seedlings.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
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Maunsell, Sarah. "Food Webs along Elevational Gradients: Interactions among Leaf Miners, Host Plants and Parasitoids in Australian Subtropical Rainforest." Thesis, Griffith University, 2014. http://hdl.handle.net/10072/368145.
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Gradients in elevation are used to understand how species respond to changes in local climatic conditions and are therefore a powerful tool for predicting how mountain ecosystems may respond to climate change. While many studies have shown elevational patterns in species richness and species turnover, little is known about how multi-species interactions respond to elevation. An understanding of how species interactions are affected by current clines in climate is imperative if we are to make predictions about how ecosystem function and stability will be affected by climate change.
This challenge has been addressed here by focussing on a set of intimately interacting species: leaf-mining insects, their host plants and their parasitoid predators. Herbivorous insects, including leaf miners, and their host plants and parasitoids interact in diverse and complex ways, but relatively little is known about how the nature and strengths of these interactions change along climatic gradients. In order to determine how elevational changes in climatic conditions affect interactions among leaf miners, their host plants and their parasitoids, I quantified these communities and their interactions along three elevational gradients in eastern Australian subtropical rainforest. In doing so, I aimed to 1) provide information on host plant use of leaf miners and the elevational associations of these relationships, 2) understand how the species richness and assemblage composition leaf miners and their parasitoids, and composition of interactions with their hosts (plants or leaf miners), is affected by elevation, 3) uncover any elevational changes in the structure of quantitative networks connecting leaf miners and their parasitoids, and 4) test if parasitism pressure increases at the lower edge of, and below the elevational range of a specific leaf miner species.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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McKenzie-Smith, Fiona Julie, and n/a. "Habitat and Hydrological Variability in Sub-Tropical Upland Streams in South-East Queensland." Griffith University. Australian School of Environmental Studies, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030725.142256.
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Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them. Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface. Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought. The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively. Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters. Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the 'third' experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment. Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within 'ecological time' are perceived as critical to understanding the role of benthic sediment substratum.
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McKenzie-Smith, Fiona Julie. "Habitat and Hydrological Variability in Sub-Tropical Upland Streams in South-East Queensland." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/366461.
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Headwater streams are extremely vulnerable to the consequences of land-use change as they are tightly coupled with the surrounding landscape. Understanding the natural processes that influence the structure and function of these ecosystems will improve our understanding of how land-use change affects them.
Benthic substratum habitat was investigated in a sub-tropical headwater stream by quantifying temporal change to sediment texture of surface sediments (less than 10cm), over four years. Hydrological characteristics were also surveyed in detail, as hydrological regime is a primary determinant of sediment transportation. Additionally, measures of hydro-geological features - hydraulic conductivity and groundwater depth were made in order to explore features of sediment habitat that extend beyond the sediment-water interface.
Whilst the typical discharge pattern was one of intermittent base flows and infrequent, yet extreme flood events associated with monsoonal rain patterns, the study period also encompassed a drought and a one in hundred year flood. Rainfall and discharge did not necessarily reflect the actual conditions in the stream. Surface waters were persistent long after discharge ceased. On several occasions the stream bed was completely dry. Shallow groundwater was present at variable depths throughout the study period, being absent only at the height of the drought.
The sediments were mainly gravels, sand and clay. Changes in sediment composition were observed for fine particulates (size categories less than 2mm). The grain size change in the finer sediment fractions was marked over time, although bedload movement was limited to a single high discharge event. In response to a low discharge regimen (drought), sediments characteristically showed non-normal distributions and were dominated by finer materials. High-energy discharge regimes (flood) were characterised by coarsening of sands and a diminished clay fraction. Particulate organic matter from sediments showed trends of build-up and decline with the high and low discharge regimes, respectively.
Benthic habitats were described according to prevailing hydro-geological parameters. Faunas from sediment substratum samples were associated with identified habitat categories. The fauna reflected the habitat variability in terms of hydrological disturbance of the substratum structure and intermittency of discharge. An applied multivariate procedure was used to correlate temporally changing environmental parameters and faunal abundance data. Faunas were correlated with a group of variables dominated by either discharge variables or sediment textural parameters.
Sediment characteristics that affect substratum quality and substratum preference at the micro-scale were investigated via hypotheses testing. A model of carbon loss was used to determine how long particulate organic matter could potentially sustain microbial activity under experimental conditions. An estimate of up to 200 days was determined from this laboratory experiment. Secondly, enriched carbon isotopes were used in a field-based experiment to establish a link between sediments and macrofauna. Enrichment via organic sediments was found for various detritivorous and carnivorous taxa. In the ‘third’ experiment, artificial treatments were applied to elucidate substratum preference. Fauna was offered the choice of variable quantities of clay and/or quality of organic matter. There were no significant preferences found for the different substratum treatments, although further investigation is needed and a different outcome from this method may be achieved under more benign field conditions than those encountered during this experiment.
Finally, the study was set within a context of the primary features of scale. Climate and hydrological features, including linkages with the alluvial aquifer and terrestrial ecosystem, and their potential to change within ‘ecological time’ are perceived as critical to understanding the role of benthic sediment substratum.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Faculty of Environmental Sciences
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Barton, Andrew P. "Soil erosion and conservation on arable sub-tropical ultisols in Yunnan province, China." Thesis, University of Wolverhampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310709.
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Gonçalves, Daniel Ruiz Potma. "Soil carbon balance in long-term no-till in a sub-tropical environment." Universidade Estadual de Ponta Grossa, 2018. http://tede2.uepg.br/jspui/handle/prefix/2525.
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Solos podem ser uma fonte ou um dreno de CO2 atmosférico, dependendo do seu sistema de manejo. Atualmente, o uso do solo e mudança de uso do solo emitem 1,3 ± 0,5 Pg C ano-1, equivalente a 8% das emissões globais. Técnicas como a agricultura de baixa emissão de C têm sido desenvolvidas para sequestrar C nos solos e reduzir a emissão de gases do efeito estufa. Porém, além dos desafios políticos e sociais envolvendo a doção destes sistemas, ainda há muita incerteza sobre o seu real potencial de mitigação. Assim, os objetivos desse estudo foram: i) Quantificar as fontes históricas e atuais de emissão de gases do efeito estufa na região dos Campos Gerais do Paraná, Brasil; ii) quantificar o potencial das melhores práticas de manejo agrícola baseadas nos três pilares da agricultura de conservação: Solo permanentemente coberto, plantio direto e rotação de culturas, em longo prazo (30 anos) para sequestrar carbono no solo, utilizando a fazenda Paiquerê (localizada na região dos Campos Gerais) como um modelo de sucesso; iii) estimar o impacto da adoção das melhores práticas de manejo nas áreas agrícolas da região e globalmente onde adequadas pelos próximos 100 anos utilizando os modelos Century e Roth-C. As fontes de gases do efeito estufa foram apresentadas como um inventário e mostraram que as emissões históricas (1930 – 2017) foram 412,18 Tg C, no qual as mudanças de uso do solo contribuíram com 91% (376,2±130 Tg C). As florestas sequestraram 51.7 ± 23.9 Tg C em 0.6 Mha em 47 anos (1.8 Tg C Mha-1 ano-1) e o plantio direto sequestrou 30.4 ± 23.9 Tg C em 1.9 Mha em 32 anos (0.5 Tg C Mha-1 ano-1). Ambos os modelos tiveram uma boa performance e o modelo Century foi mais eficiente em simular os estoques de carbono do solo, o resíduo médio da simulação foi 10 Mg C ha−1 (13%) para n = 91. O resíduo do modelo aumentou com a quantidade de óxidos no solo, sugerindo que a inclusão do controle mineralógico pode reduzir o viés de simulação. As predições do Century mostraram que o sistema tem potencial para mitigar 13 anos de emissões regionais (330 Tg C em 100 anos) ou 105 anos de emissões do setor agricultura, floresta e pecuária (40 Tg em 100 anos) na região. Da mesma forma, globalmente o sistema apresenta um potencial para sequestrar 2,5 ± 0.02 Pg C na profundidade 0–20 cm e 11,7 ± 3 Pg C na profundidade 0-100 cm em 86 milhões de ha distribuídos por todo o mundo. Este valor é equivalente à 11% das emissões globais dos setores agricultura, floresta e pecuária e mudanças de uso do solo. Assim, a nossa metodologia possa ser utilizada como um modelo para divulgar o potencial da agricultura conservacionista em sequestrar C nos solos e suportar políticas públicas que visem à mitigação das emissões de gases do efeito estufa.
Soils can be a source or sink of atmospheric CO2, according to land use and management. Currently the land use and land use change (LULUC) emits 1.3 ± 0.5 Pg carbon (C) year-1, equivalent to 8% of the global annual emission. Techniques such as low carbon agriculture, has been developed to sequester C in soils and reduce greenhouse gas (GHG) emissions. However, besides political and social challenges for the system adoption, there’s still great uncertainty related to its real mitigation potential. This study aimed: i) Quantify the historical and current main sources of GHG emissions for Campos Gerais region in Paraná state, Brazil; ii) quantify the potential of long term (30 years) agricultural best management practices, based on the three pillars of conservative agriculture: permanent soil cover, crop rotation and no-till, to sequester C in soils, using Paiquerê farm (located in Campos Gerais region) as a successful model; iii) estimate the impact of best management practices adoption in the region croplands and globally for the next 100 years where is suitable using Century and Roth-C models. The GHG emission sources were presented as an inventory and showed that historical (1930 – 2017) GHG emissions in the region was 412.18 Tg C, in which LULUC contributes 91% (376.2±130 Tg C). Forestry sequestered 51.7 ± 23.9 Tg C in 0.6 Mha in 47 years (1.8 Tg C Mha-1 year-1) and no-till sequestered 30.4 ± 23.9 Tg C in 1.9 Mha in 32 years (0.5 Tg C Mha-1 year-1). Both models performed well, and Century was more efficient for simulate the SOC stocks, the mean residue was 10 Mg C ha−1 (13%) for n = 91. The model residue increased along with the oxides content in the soil clay fraction, suggesting that mineralogical control inclusion can reduce the model simulation bias. Century predictions showed that the system currently practiced at Paiquerê farm have the potential to mitigate 13 years of regional total emissions (330 Tg C in 100 years) or 105 years of agriculture, forestry and other land use (AFOLU) sector emissions (40 Tg in 100 years) in the region. In the same way, it has the potential to sequester 2.5±0.02 Pg C at 0-20 cm and 11.7±3 Pg C at 0-100 cm soil depth in 86 million ha globally. This is equivalent to 11% of global annual emissions from LULUC sector. In this way, our methodology can be used as a model to access the potential of conservation agriculture to sequester C and support public policies aiming to mitigate GHG emissions.
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Snow, J. T. "The environmental, elemental and proteomic plasticity of Trichodesmium in the (sub) tropical Atlantic." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374241/.
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Phytoplankton dominate surface ocean biomass and have major roles in global carbon and nutrient cycling. Of these, the cyanobacterial Trichodesmium sp. are considered the dominant and most conspicuous nitrogen fixers in the tropical and subtropical oceans, regimes frequently characterised by low concentrations of fixed nitrogen. Despite being arguably the best studied marine diazotroph, the factors controlling the distribution and growth of Trichodesmium remain a subject of debate, with sea surface temperature, the partial pressure of CO2 and nutrients including iron and phosphorus, all suggested to be important. Dominant controls on the biogeography of other important marine diazotrophic organisms are even less clear. Synthesising data from 7 research cruises collectively spanning large temporal and spatial scales across the Atlantic Ocean, including 2 previously unreported studies crossing the largely under-sampled South Atlantic gyre, we assessed the relationship between proposed environmental drivers and both community nitrogen fixation rates and the distribution of Trichodesmium. Simple linear regression analysis of the combined data set would suggest no relationship between any of the sampled environmental variables and nitrogen fixation rates. However, considering the concentrations of iron and phosphorus together within a resource-ratio framework indicates the combined effects these nutrients have on Trichodesmium and broader diazotroph biogeography. The resource ratio framework is argued to be consistent with both the previously described North-South Atlantic contrast in Trichodesmium abundance, and the presence and consequence of a substantial non-Trichodesmium diazotrophic community in the euphotic zone of the western South Atlantic subtropical gyre. Using high-throughput chemical and biological analyses we were able to observe significant plasticity in Trichodesmium’s elemental composition. The macro- and micro- elemental composition of environmental Trichodesmium showed enrichments in arsenic, vanadium and molybdenum along an environmental phosphorus gradient, which we attributed to phosphorus- stress induced accidental uptake. Stoichiometric comparison with bulk phytoplankton revealed enrichments in iron (alongside nickel, copper and zinc) to which we predict 12-37% is attributed to the process of nitrogen fixation. To date, understanding Trichodesmium’s propensity for growth in iron-deplete oceanic regimes has focused on traditional metrics such as physiological rates and targeted molecular studies. Here a labelfree quantitative proteomics technique (MSE) was employed to examine the full complement of Trichodesmium erythraeum IMS101’s proteome when grown with different iron availability. Iron stress resulted in increased abundances in proteins involved in iron-stress acclimation and of proteins involved in iron-uptake. Also a systematic decrease in the iron-binding proteins involved in photosynthesis and nitrogen fixation is reported. Such changes reveal potentially novel iron uptake pathways but also that Trichodesmium reallocates resource away from nitrogen fixation and towards components of the photosynthetic apparatus under iron stress. Finally, utilising a bioinformatic approach we are able to generate a predicted metallo-proteome for Trichodesmium, detailing the relative protein-bound concentrations of iron, vanadium, arsenic, molybdenum, zinc, nickel, copper, manganese, cadmium and cobalt. By comparing this metallo-proteome to the observed intracellular metallome we were able to synthesise our findings into the description of discreet Trichodesmium phenotypes observed in the (sub)-tropical Atlantic. In doing so, we present a comprehensive, observation-based explanation of the interactions between Trichodesmium and iron, linking small scale physiology to basin-scale biogeochemical variability.
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de, Putron Samantha Julie. "The reproductive ecology of two corals and one gorgonian from sub-tropical Bermuda." Thesis, Swansea University, 2003. https://cronfa.swan.ac.uk/Record/cronfa42702.
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This study examines the sexual reproductive ecology of three species of corals common on the sub-tropical reefs of Bermuda: the scleractinians Porites astreoides and Madracis mirabilis, and the gorgonian Pseudoplexaura porosa. The reproductive biology of corals in Bermuda is of particular interest because low winter seawater temperatures and geographical isolation make it an extreme of distribution for many of the species there. In addition, the Bermuda platform comprises reef zones that experience gradients of temperature, sediment loading and wave intensity at the different depths. The objectives are twofold; firstly, information is presented on the reproductive mode, sexuality and fecundity of the corals, and the occurrence of lunar periodicity to gamete development, planula release or spawning. The second objective addresses the question of whether environmental variability across the Bermuda platform and between years alters the reproductive cycles of these species. The study species varied in reproductive mode and sexuality. The scleractinian Porites astreoides is a brooder with a mixed sexuality; the gorgonian Pseudoplexaura porosa exhibits gonochorism with broadcasting, and the scleractinian Madracis mirabilis has hermaphroditic colonies with a proposed intermediate 'pseudo-brooding' reproductive mode. Fecundity was variable within and between Po. astreoides colonies but was not related to colony size. There was a relationship between polyp size and gamete production in Ps. porosa. The synchrony of lunar periodicity to spawning or planulae release varied between the species and this is related to the different reproductive modes. The extent that planula release of Po. astreoides was synchronised to the lunar cycle also varied according to the reef zone in Bermuda, a proposed consequence of variable turbidity levels from inshore to offshore. Observed differences in the reproductive effort of Po. astreoides and Ps. porosa, both at the different reef zones within Bermuda, as well across study years, are related to spatial and inter-annual variations in temperature profiles.
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Blazer, Mark A. "Architectural strategies in reducing heat gain in the sub-tropical urban heat island." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002781.
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O'Hanlon, Eoghain Rua Patrick Allen O'Hanlon. "Evaluating the Effectiveness of Stormwater Quality Improvement Devices (SQIDs) in Sub-Tropical Conditions." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/366913.
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Stormwater quality improvement devices (SQIDs) are frequently installed to improve the water quality of runoff to match particular water quality objectives (WQOs). However, there is a lack of data to evaluate the functioning and performance of these systems, particularly in sub-tropical climates. The primary aim of this study was to collect such data. Another aim was to establish baseline monitoring of an urban catchment before the installation of SQIDs and to forecast the improvement to the water quality after installation.
This study investigates the performance of two SQIDs (a pond and wetland) within a treatment train that has been retrofitted into a sub-tropical urban catchment (Waterbird Park) on the Gold Coast, Queensland, Australia. The method used to evaluate the effectiveness of this system was through rainfall events, sampling of the inlets to the pond, its outlet and the outlet of the wetland. Sampling was conducted through the use of automatic sampling devices, before the retrofit, during the construction phase and after the construction of the treatment train. A secondary study was conducted on a separate catchment, (Discovery Park), in which no SQIDs were installed. The Discovery Park site was used as a baseline study, where the objective was to estimate the likely improvement that a lake and wetland treatment train would have at that site.Thesis (Masters)
Master of Philosophy (MPhil)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Clough, Elizabeth Anne, and n/a. "Factors Influencing Ant Assemblages and Ant Community Composition in a Sub-Tropical Suburban Environment." Griffith University. School of Environmental and Applied Science, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040719.141317.
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The main objective of this study was to examine the abundance and diversity of ants in suburban sites following vegetation removal or modification for development. This research examines the capacity of suburban sites to support ant diversity, which is dependent on the site characteristics and their surrounding environment. The study focused on 29 suburban garden and 3 suburban reserve sites on the Gold Coast, Queensland, Australia. This region, through continuing land development, undergoes ongoing habitat disturbance and modification. Ground-dwelling ants were collected by pitfall trapping in study sites over three summers between 1997 and 1999. In total, 28,512 ants from 60 species in 31 genera were collected. Garden sites that maintain vegetation structural diversity were found to be most similar to reserve sites in terms of ant community composition. These sites were highest in ant richness and diversity and contained particularly high proportions of specialized ant species. Sites in close proximity to remnants of native vegetation contained higher species diversity and a greater proportion of specialized ant species. The introduced tramp ant, Pheidole megacephala was found in 28 of the 32 sites and was found to significantly reduce ant species richness and diversity and displace the dominant ant Iridomyrmex sp. 1 in suburban environments. This ant poses a serious threat to the recovery of a diverse ant fauna to suburban environments. Ant community composition was shown to vary significantly among suburban sites. The ant functional groups commonly found in disturbed sites were abundant in open sites with little canopy cover in this study. Sites that provided vegetation structural diversity and areas of closed canopy supported similar functional groups to natural vegetation remnants. These results indicate that ant communities in suburban environments respond to disturbance in a similar manner to ant communities in tropical forests and rainforests. The dominance by functional groups and presence of specialized species may therefore be used as an indicator of disturbance and the restoration of suitable habitat in suburban sites. The presence of specialized species of ants in suburban garden sites and their clear preference for particular site characteristics indicate that these species utilize resources available in the suburban matrix. These results indicate that residential suburban sites are of value in the enhancement of ant diversity in fragmented landscapes and that they may provide supportive habitat to, and act as corridors between, vegetation fragments. In order to preserve biodiversity within suburban environments, landowners should be advised to retain as much existing vegetation within a site as possible. Clearing should be limited to that necessary to allow construction of dwellings and for safety. In addition, landowners should be encouraged to establish or maintain structurally diverse vegetation layers within sites in order to provide diverse microenvironments for fauna habitat.
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Roberge, Alain. "Analysis of intense sub-tropical moisture transports into high latitudes of western North America." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19280.
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There can often be significant interactions between high and tropical latitudes during the Northern Hemisphere's cold season. In periods of amplified atmospheric flow, these interactions can lead to the poleward transport of significant tropical moisture from near Hawaii into northwestern North America. These are pineapple express (PE) events. This study documents the synoptic-scale signatures associated with the PE. A trajectory analysis was used to partition the events into three different synoptic types according to the origin of their trajectories. Results indicate that this large scale moisture transport is often associated with the sub-tropical jet stream, which is curved due to a high pressure ridge concomitant with the Aleutian Low. Additionally, similar moisture transport may be observed in absence of the ridge with a stronger Aleutian Low. Furthermore, thickness anomalies after the events revealed a significant warming over North America lasting for at least three days.Il peut souvent y avoir des interactions importantes entre les latitudes nordiques et tropicales durant l'hiver de l'hémisphère nord. Durant des périodes de courant atmosphérique amplifié, ces interactions peuvent mener à un transport important d'humidité tropicale de la région d'Hawaii jusqu'au au nord-ouest de l'Amérique du Nord. Ces évènements se nomment « pineapple expresses » (PE). Cette étude documente les caractéristiques synoptiques de ces évènements. Une analyse de trajectoires a été utilisée pour diviser les évènements en trois différents types synoptiques selon l'origine de leurs trajectoires. Les résultats indiquent que ce transport d'humidité à grande échelle est souvent associé avec le courant jet subtropical, qui se courbe due à une crête de haute pression accompagnée du système de basse pression des Aléoutiennes. De plus, un transport d'humidité aussi important peut être observé sans la présence de cette crête de haute pression mais avec un plus fort système de basse pression des Aléoutiennes. Parallèlement, les anomalies d'épaisseurs de l'atmosphère après ces évènements du PE révèlent un réchauffement significatif en Amérique du Nord pendant au moins trois jours.
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Coles, David P. "Dusk transition in sub-tropical reef fish communities off of North and South Carolina." Thesis, College of Charleston, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1565212.
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Although dawn and dusk periods comprise a relatively small part of the day, their importance as key ecological transition periods has been recognized for some time. Previous marine investigations into this transition have focused on tropical locations and have mostly been qualitative in nature. This project focused on the dusk period in sub-tropical reef fish communities off the coasts of North and South Carolina. High-definition underwater video was collected in 2013 and 2014 at a variety of sites featuring natural live-bottom habitat. Independent samples (43 videos) were obtained on 17 sampling dates. Fishes were tallied by time relative to sunset (TRTS) in an effort to identify temporal abundance patterns and categorize taxa by temporal niche. Sufficient data were collected for statistical analysis of 27 taxa, representing 15 families. Analyses explored whether there was a relationship between time and abundance. Of the taxa analyzed, ten showed no temporal pattern during the dusk period, seven showed abundance peaks during dusk, and ten showed declines in abundance during dusk. Patterns were not always consistent within families. In particular, the Serranidae and Sparidae families featured a variety of patterns. Uncommon species and ephemeral behavioral events were also noted and described.
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Clough, Elizabeth Anne. "Factors Influencing Ant Assemblages and Ant Community Composition in a Sub-Tropical Suburban Environment." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/366528.
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The main objective of this study was to examine the abundance and diversity of ants in suburban sites following vegetation removal or modification for development. This research examines the capacity of suburban sites to support ant diversity, which is dependent on the site characteristics and their surrounding environment. The study focused on 29 suburban garden and 3 suburban reserve sites on the Gold Coast, Queensland, Australia. This region, through continuing land development, undergoes ongoing habitat disturbance and modification. Ground-dwelling ants were collected by pitfall trapping in study sites over three summers between 1997 and 1999. In total, 28,512 ants from 60 species in 31 genera were collected. Garden sites that maintain vegetation structural diversity were found to be most similar to reserve sites in terms of ant community composition. These sites were highest in ant richness and diversity and contained particularly high proportions of specialized ant species. Sites in close proximity to remnants of native vegetation contained higher species diversity and a greater proportion of specialized ant species. The introduced tramp ant, Pheidole megacephala was found in 28 of the 32 sites and was found to significantly reduce ant species richness and diversity and displace the dominant ant Iridomyrmex sp. 1 in suburban environments. This ant poses a serious threat to the recovery of a diverse ant fauna to suburban environments. Ant community composition was shown to vary significantly among suburban sites. The ant functional groups commonly found in disturbed sites were abundant in open sites with little canopy cover in this study. Sites that provided vegetation structural diversity and areas of closed canopy supported similar functional groups to natural vegetation remnants. These results indicate that ant communities in suburban environments respond to disturbance in a similar manner to ant communities in tropical forests and rainforests. The dominance by functional groups and presence of specialized species may therefore be used as an indicator of disturbance and the restoration of suitable habitat in suburban sites. The presence of specialized species of ants in suburban garden sites and their clear preference for particular site characteristics indicate that these species utilize resources available in the suburban matrix. These results indicate that residential suburban sites are of value in the enhancement of ant diversity in fragmented landscapes and that they may provide supportive habitat to, and act as corridors between, vegetation fragments. In order to preserve biodiversity within suburban environments, landowners should be advised to retain as much existing vegetation within a site as possible. Clearing should be limited to that necessary to allow construction of dwellings and for safety. In addition, landowners should be encouraged to establish or maintain structurally diverse vegetation layers within sites in order to provide diverse microenvironments for fauna habitat.Thesis (Masters)
Master of Philosophy (MPhil)
School of Environmental and Applied Science
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Kashfi, Syeed Anta. "Investigating variation in bus ridership rates within localised areas of a sub-tropical city." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/92993/1/Syeed%20Anta_Kashfi_Thesis.pdf.
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This thesis makes a significant contribution to knowledge and understanding of 'Human Travel Behaviour' in relation to transportation research. It holds some important merits that have not been proposed before. It develops a new, comprehensive and meaningful relationship that includes bus transit ridership change due to weather variables, seasonality and transit quality of service within a single daily ridership rate estimation model. The research incorporated both temporal and spatial influences on ridership within a modelling structure, named as the Nested Model Structure. It provides a complete picture of ridership variation across the sub-tropical city of Brisbane, Australia.
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Guastella, Devid. "Studies on whiteflies living on herbaceous plants and their parasitoids in tropical and sub-tropical environment through combined morphological, molecular and geostatistical approaches." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1601.
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In tropical and sub-tropical regions, whiteflies are common pests causing severe losses on food-crops and a threat to food-security. I the sub-tropics, a critical issue is the lack of spatial information about whiteflies. Moreover, outdated information is available about the current status of their parasitoid fauna. On the contrary, in the tropics no or incomplete information is available regarding the diversity of whiteflies and their parasitoids.
Methods: Morphological, molecular and geostatistical methods were used to assess the whitefly and parasitoid fauna on herbaceous plants in a subtropical environment (Sicily) and in the tropics (Tanzania). Morphological techniques were adopted first to identify specimens. Moreover, molecular markers were used to confirm cryptic species. Bio-climatic aspects have been taken into account in the aim to understand which factors influence the spread of whitefly pest species. For this reason, diversity and distributional information was first accumulated to build a database. The database was then analyzed by Geographical Information System for (i) mapping richness and abundance, (ii) modeling the potential distribution of a pest species and (iii) revealing zones for parasitoid reserve selection. Finally, we showed how elevation gradient can be an additional instrument to study the cryptic species
Principal findings: In Sicily, a measure of the current status of whitefly and parasitoid fauna was given. Nine whitefly species were identified: Aleurolobus marlatti, Aleurothrixus floccosus, Aleyrodes elevatus, Aleyrodes proletella, Bemisia afer, Bemisia tabaci, Dialeurodes citri, Trialeurodes lauri and T. vaporariorum. Moreover, three cryptic species were identified in the B. tabaci species complex: B. tabaci Mediterranean, B. tabaci Middle East-Asia 1 and B. tabaci Italy. Modelling the potential distribution of these major whitefly pests at regional scale revealed suitable areas where they can occur. A striking finding in this study was the replacement of the exotic invader B. tabaci Middle East Minor 1 by the B. tabaci Mediterranean species, which is at present the predominant. Another important finding was the fact that the elevational gradient functions as a filter, selecting the species of B. tabaci group. As for the parasitoid fauna, nine species were identified belonging to the genera Encarsia and Erermocerus. A reserve selection model permitted to identify two main areas that seem to function as reservoir for whitefly parasitoids.
In Tanzania the diversity of whitefly species infesting cassava and other herbaceous plants was investigated. Ten whitefly species were identified: Aleurodicus dispersus; Aleurothrixus floccosus; B. tabaci species group (B. tabaci Sub-Saharan Africa 1, B. tabaci Mediterranean and B. tabaci Indian Ocean); B. afer, Bemisia sp. (formerly Asterobemisia sp.), Dialeurodes citri, Paraleyrodes bondari and T. vaporariorum. The potential distribution of super-abundant B. tabaci was modelled, revealing the presence of suitable areas extending also further to neighbouring countries such as Zambia. Moreover, unsuitable area was identified serving as an environmental barrier and avoiding the spread of the pest to the south-eastern part of the country. Six Encarsia, four Eretmocerus and one Cales species were identified, adding more species to the previous list of parasitoids recorded in East-Africa and discovering of a probable new species of Eretmocerus. For the first time En. mineoi and En. sp. pr. circumsculpturata were recorded in Tanzania. Parasitoids have been detected at very low numbers, showing the occurrence of a relatively scarce natural enemies complex.
Conclusions: The research presented here documents the whitefly and parasitoid fauna colonizing herbaceous plants in the two sites chosen, respectively tropical and sub-tropical regions. Combining the methods mentioned above was useful in understanding the diversity and distribution of these insects.
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Tao, Juan. "Riverine food webs and the effects of human disturbance on the contribution and quality of food sources to aquatic consumers in sub-tropical rivers." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/371244.
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Understanding flows of energy and nutrients through food webs can provide important insights into mechanisms influencing the structure and function of riverine ecosystems and ecological responses to human activities. However, it is not well understood how changing land use, river impoundment and flow alteration affect the quality and quantity of food resources supporting riverine food webs. The broad aims of this thesis were to determine: (1) the effects of human disturbances on basal food sources and food quality for aquatic consumers in sub-tropical rivers in south-east Queensland (SEQ); and (2) the potential for poor food quality to be causing low recruitment of the threatened Australian lungfish (Neoceratodus forsteri Krefft, 1870).
Understanding food webs is important and useful for planning environmental conservation, management and restoration. However, research on food webs has not been uniformly conducted across different parts of the world; it tends to be concentrated in specific areas or ecosystem types, and this may limit our understanding of food webs and ecosystem processes. Therefore, before answering the research questions posed, I first examined trends in food web research over time by analysing publication data from Web of Science (WOS). The review focused on the ecosystem types studied, countries in which the studies were conducted, and which countries collaborated on the studies. A total of 20,239 publications on food webs were examined, and food web research has increased dramatically since the 1990s. Most publications were focused on aquatic ecosystems, and North America and Europe contributed far more studies than Africa and South America. Collaboration among individual authors and countries has become increasingly prevalent. The USA and Canada were consistently the two most productive countries, and had the most frequent collaborations. The results indicate that food web studies from terrestrial ecosystems also require more attention in the future, especially countries from Africa and South America. Importantly, the majority of freshwater food web research has been conducted in temperate systems in the northern hemisphere. The comparatively small number of studies conducted in tropical, sub-tropical or arid freshwater systems may limit our ability to develop a general understanding and synthesis of the key factors influencing freshwater food web processes globally.
The relative importance of allochthonous sources versus autochthonous sources to aquatic consumers varies in predictable ways along longitudinal gradients in rivers. However, it remains unclear how this will change under human disturbances, such as river impoundment, flow alteration and agricultural land use. I examined the potential effects of these anthropogenic disturbances on aquatic food webs by using stable isotopes (δ13C and δ15N) from six sites in each of two comparable sub-tropical rivers, the Brisbane River and Mary River in SEQ. The Brisbane River downstream was heavily affected by impoundment and flow alteration compared to the upstream and to the Mary River. Both catchments had similar levels of agricultural land use. The results showed that the main sources of variation in δ13C and δ15N isotopic values of most basal sources, invertebrates, and fish trophic guilds were due to the effects of relative catchment position within rivers, with minimal overall differences between rivers and seasons. Most of the basal sources and consumers showed a general enrichment in δ15N values from upstream to downstream in both rivers, which could be caused by increased anthropogenic nitrogen inputs and changed nitrogen cycling in riparian soils. Mixing model analyses revealed that most of the consumers examined in both rivers were supported by autochthonous carbon sources, with no detectable influence of flow alteration or land use. In contrast, the reliance of consumers on food sources was changed to a higher contribution from autochthonous pelagic sources in Brisbane River sites downstream of the dam.
Fatty acids (FA) play an important role in aquatic food webs and are potentially powerful biomarkers for studying the structure and function of ecosystems. However, there has been limited research characterizing FA profiles among potential food sources and how they vary spatially along natural and anthropogenic disturbance gradients in rivers. Quantifying these major sources of variation in FA profiles of aquatic food sources is a critical pre-requisite to understanding variation in food quality for fish and other higher consumers and can contribute to more effective aquatic ecosystem conservation and management. I investigated the FA composition of nine potential food sources for higher consumers (including primary producers and invertebrate primary consumers) collected from eight sites in two sub-tropical rivers (Brisbane River and Mary River) subjected to varying degrees of human disturbance. Different food sources had distinctive FA profiles, and several functionally important unsaturated FA were found to bioaccumulate with increasing trophic position. Partial redundancy analysis (pRDA) was conducted to separate the effects of food source category (taxa) and environment (site). Taxa and site together explained 70.4 % of the variation in FA profiles, though taxa alone accounted for most of this (90.6 %). I found significant spatial variation in FA composition for several food sources that were potentially related to flow alteration, but the effects were weak and not uniform across taxa.
The Australian lungfish, Neoceratodus forsteri Krefft, 1870, is federally listed threatened species whose long-term persistence is at risk due to land use intensification, water resource development, and other human pressures. Changes in the availability of high-quality food resources for this species may impact recruitment and contribute to population declines. I analysed the fatty acid (FA) composition of lungfish eggs and fin tissues from two locations with contrasting flow alteration resulting from a large impoundment in the Brisbane River. I hypothesised that flow alteration alters the FA composition of important dietary items for N. forsteri which will translate to the body tissues and eggs. The contribution of each food source was estimated with mixing models using carbon and nitrogen stable isotopes. Although no negative effect on FA composition on tissues was detected from flow alteration, the stable isotope analysis demonstrated FA difference in lungfish eggs could be attributed to changes in their diet.
To conclude, my studies found that: (1) current understanding on aquatic food web processes could be biased towards temperate systems and should be modified through conducting more studies in other systems; (2) consumers in south-east Queensland sub-tropical rivers were largely supported by algal basal sources, regardless of the influence of human disturbance; (3) basal food sources and primary aquatic consumers varied in nutritional quality and possessed distinctive FA profiles, but spatial variation in FA of individual food sources was relatively low and unaffected by human disturbances associated with dams and land use; (4) the low availability of high-quality food sources could potentially be the reason for low concentrations of FAs in lungfish eggs and potentially explain the low recruitment success of this threatened species; (5) the Wivenhoe dam increased the contribution of autochthonous pelagic sources to consumers in the Brisbane River sites downstream of the dam, but did not show a negative effect on lungfish egg quality; (6) catchment land use increased the δ15N values of sources and consumers probably through increasing anthropogenic nutrient inputs and changing nitrogen cycling in riparian soils. My studies indicate that a food web approach, focusing in particular on high-quality food sources that sustain the growth and reproduction of consumers, can inform river ecosystem conservation and management.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Yik, Frances Wai Hung. "Methodologies for simulating heat and moisture transfer in air-conditioned buildings in sub-tropical climates." Thesis, Northumbria University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357106.
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Graham, John J. (John James) 1969. "Seasonal measurements of nonmethane hydrocarbons (NMHC) in a sub-tropical evergreen forest in Southern China." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/53037.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998.Includes bibliographical references (p. 169-180).
by John J. Graham, Jr.
Ph.D.
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Salter, Michael A. "The production and preservation of fish-derived carbonates in shallow sub-tropical marine carbonate provinces." Thesis, Manchester Metropolitan University, 2013. http://e-space.mmu.ac.uk/314039/.
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Recent studies have demonstrated that marine bony fish (teleosts) precipitate inorganic calcium carbonate in their gut as a by-product of osmoregulation, subsequently excreting it into the open water column as loosely aggregated millimetre-scale pellet. These studies have primarily focused on physiological aspects of this process and the fate of resulting carbonates in pelagic settings, which is likely to be dissolution at depth. However, the implications of such carbonate production in shallow tropical and sub-tropical carbonate provinces has also begun to be considered, and it is thought that fish may contribute significant quantities of morphologically distinctive mud-grade high-Mg calcite in certain habitat settings. However, most studies of carbonate mud in modern subtropical settings do not report particles that are obviously fish-derived, and questions concerning fish-derived carbonate characteristics and post-excretion stability thus arise. The present work therefore provides more detailed characterisation of the carbonate products of an expanded range of Caribbean fish species and determines their short-term preservation potential in a sub-tropical carbonate province (the Bahamas). Following collection of carbonates from 22 fish species (all starved), precipitates were characterised using scanning electron microscopy and a suite of complimentary chemical analysis techniques. The form in which these carbonates are likely to be incorporated into surface sediments was investigated by disaggregating pellets and characterising the liberated particles by performing detailed image-based grain size analyses, with additional experiments demonstrating the likely rate and extent of pellet disaggregation by placing them in agitated seawater. Finally, short-term preservation potential was determined in a series of experiments whereby excreted precipitates were exposed to surface seawater and shallow subsurface porewater conditions for several months. Results indicate that, at the point of excretion, fish-derived carbonates are morphologically and mineralogically more varied than previously thought, although most morphotypes (e.g., ellipsoids, dumbbells, spheres, rhombohedra) are seemingly unique in shallow sub-tropical marine settings. ii High-Mg calcite, typically containing 20–35 mol% MgCO3, is the dominant product of about half the species investigated, but Mg calcite with lower MgCO3 contents (in the range 2–20 mol%) is also common, as is aragonite, which can represent up to 27 wt% of carbonates excreted by some species. In addition, amorphous magnesium carbonate (AMC) and magnesium-rich amorphous calcium carbonate (ACC), both of which are strongly hydrated, represent the dominant precipitation products of some species, with a hydrated crystalline phase (monohydrocalcite) occasionally accompanying the latter. A non-carbonate phase, brucite, is nearly ubiquitous as a volumetrically minor phase. Where analysed, all of these phases are further found to differ from other carbonate sediments in the Bahamas with regard to their stable carbon and oxygen isotope compositions; a consequence of the important role of metabolic HCO3 - in the precipitation process. Detailed grain size analyses indicate that most morphotypes are released from pellets upon disaggregation as individual mud-grade particles that retain their distinctive forms. However, extreme agitation can result in polycrystalline forms releasing their fibre-like components; these particles being less distinctive than their parent forms. In contrast, some particles are intergrown and do not disaggregate beyond particle clusters that are up to fine sand sized. Moreover, excreted pellets do not necessarily always disaggregate, with moderate agitation in seawater resulting in a significant proportion of carbonate being retained as intact pellets, albeit smaller (typically fine sand sized) and more well-rounded than initial pellets (typically fine to coarse sand sized). In quiescent settings pellet diminution is less extensive, and it is thus hypothesised that a significant proportion of fish-derived carbonates excreted in the Bahamas is preserved as sand-grade pellets. Despite the highly distinctive nature of fish-derived carbonates, particles that can be attributed to production by fish nevertheless remain elusive in studies of Bahamian surface sediments. It is thus necessary to invoke post-excretion processes of dissolution and/or recrystallisation to explain the apparent disparity between production rates and occurrence as sedimentary particles. Indeed, it is demonstrated here that AMC, brucite, and large quantities of ACC undergo complete dissolution in seawater within a few days of excretion, with the remaining ACC apparently crystallising to form fine sand-grade (50–200 μm diameter) polycrystalline calcite spheres over similar timescales. iii Monohydrocalcite, also undergoes complete dissolution or alteration (to calcite) during 3 month exposures to artificial seawater, and is predicted to alter in a similar manner in natural settings. Conversely, anhydrous crystalline phases remain largely unchanged after porewater and seawater exposures lasting several months, although two important post-excretion processes are observed. Firstly, high-Mg calcite ellipsoids appear to undergo partial dissolution (with preferential loss of MgCO3) and possible recrystallisation, and, based on these observations, it is predicted that longer exposure times will result in changes being pervasive, possibly obscuring the piscine origin of initial crystals. Secondly, carbonate pellets containing minor amounts of aragonite at the point of excretion appear, in some cases, to stimulate post-excretion growth of abundant aragonite needles that are morphologically similar to aragonite needles that dominate Bahamian carbonate muds. It is further apparent that these processes are inhibited in uncleaned samples, possibly due to surface adsorption of organic compounds, but the evidence after 3 month exposures indicates that inhibiting factors might eventually be overcome. Based on these results and modelling of carbonate excretion across shallow platform areas of the entire Bahamian archipelago, it is predicted that about 18 % of excreted carbonates will dissolve after excretion, while a further 53 % may alter beyond recognition within a very short period (perhaps on the order of years). Moreover, characterisation of carbonates produced by three species of normally feeding fish indicates they produce only amorphous carbonates, despite producing crystalline phases when starved. This difference, attributed to the inhibition of CaCO3 crystallisation by dietary phosphate, indicates that loss of fish-derived carbonate to dissolution might be considerably higher than 18 % under normal natural circumstances. The sedimentary significance of fish-derived carbonates thus remains enigmatic, but results presented herein indicate that they follow very different preservation pathways depending on their excreted form, and that they may make previously unrecognised contributions to: i) the carbonate sand fraction (as peloids); and ii) aragonite needle muds (as crystals grown post-excretion).
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Kotkowski, Rachel. "Environmental Influences on Bacterio-phytoplanktonic Coupling and Bacterial Growth Efficiency in a Sub-tropical Estuary." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1155.
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Bacterio-phytoplanktonic coupling and bacterial growth efficiency (BGE) measurements were used to analyze microbial trophic dynamics and the influence of environmental factors in Florida Bay, Florida. Phytoplankton gross primary productivity (GPP) was measured using 24-hour in situ oxygen incubations; bacterial productivity (BP) was measured using 3H- thymidine incorporation. Weak bacterio-phytoplanktonic coupling was observed over the sampling period. BP was more influenced by local total nitrogen concentrations while GPP was more evenly distributed. BGE rates were low but consistent with marine and estuarine ecosystems worldwide. Results suggest that bacterioplankton growth in Florida Bay is relatively uncoupled from phytoplankton production, which may be due in part to the low levels of phytoplankton biomass in the water column, the large amount of seagrass-derived DOM production in this shallow lagoon, the loading of nitrogen and organic matter associated with terrestrial runoff, and/or their combination.
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Mundava, Charity. "Estimating Above Ground Biomass using Remote Sensing in the Sub-Tropical Climate Zones of Australia." Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/1866.
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The study focused on assessing the total above ground biomass using remote sensing in the Kimberley rangelands of Western Australia. Remote sensing has the advantage that it can rapidly provide estimates non-destructively on a large scale with a high temporal frequency. In this thesis a field sampling protocol was developed and mono- and multi-temporal above ground biomass estimation models could be calibrated and validated with field based measurements for the most significant vegetation types.
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French, Michael Duncan. "Mathematical modelling of neglected tropical disease control with particular reference to schistosomiasis in sub-Saharan Africa." Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550985.
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The overarching aim of the thesis is the use of mathematical models to provide policy-relevant guidance to neglected tropical disease (NTD) control programmes, particularly those against schistosomiasis, identified following discussions with Schistosomiasis Control Initiative (SCI) staff, and utilising the SCl's extensive datasets from sub-Saharan Africa. Firstly, changes are estimated in the force of infection (Fa/) of schistosomes following annual control in Uganda, relative to baseline, expressed as the number of mature parasites acquired per host per year. It is known that praziquantel treatment results in significant reductions in infection intensity in treated individuals; however, the thesis shows that Fal reductions also result in benefits for untreated individuals. Models are developed, parameterized and fitted to Schistosoma mansoni (intestinal schistosomiasis) data from areas with differing initial endemicity, and results indicate significant and substantial reductions following treatment. Models are developed further to estimate reductions in the Fal of S. haematobium (urogenital schistosomiasis) and used in other SCI locations (Uganda, Tanzania, Burkina Faso, Niger, Mali, Zambia). Secondly, the thesis investigates changes in schistosome population genetic structure following chemotherapy to gain insights into the transmission and clinical processes of the disease. Large-scale chemotherapy-based control likely exerts strong selective pressure on parasite populations. Recently developed microsatellite markers have demonstrated significant reductions in S. mansoni genetic diversity following one round of treatment. This may have implications for the parasite's evolutionary potential and the future success of such campaigns. Stochastic re-sampling approaches are used to estimate the magnitude of changes, the robustness of the microsatellite markers used, and to identify optimum sampling frameworks in terms of numbers of hosts, and numbers of parasites per host required, in order to detect changes in parasite population structure. Finally, results are discussed in terms of the role that models can play in the implementation, monitoring and evaluation of programmes for NTD control, and current research gaps are high lighted.
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Milne, Eleanor. "Soil conservation in relation to maize productivity on sub-tropical red soils in Yunnan Province, China." Thesis, University of Wolverhampton, 2001. http://hdl.handle.net/2436/93882.
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Agricultural land in China is being degraded, with soil erosion becoming an increasing problem. In Yunnan Province, south-west China, there is a long history of soil erosion due to soil type, climate, anthropogenic influence and because 95% of the Province is mountainous. Population pressure and lack of flat land necessitate cultivation of steep slopes. The Yunnan Government prohibits cultivation of slopes >25°, however policy enforcement would result in food shortages in the Province, due to a lack of suitable land <25°. Therefore, the most appropriate way to curb soil erosion in Yunnan is to devise affordable agronomic means of reducing soil loss, which do not decrease crop productivity on sloping land currently under cultivation. At present, very little research has addressed these issues. A research project, building on existing work from 1993-1996, was initiated in 1998. The aim was to test the hypothesis that contour cultivation and contour cultivation plus straw mulch decrease runoff and soil erosion rates on sloping land in Yunnan Province under maize cultivation and to assess the impact of these conservation measures on maize productivity and soil nutrient status. Thirty runoff plots, located on three different slope angles (I 3°, II 10° and III 27°), in three groups of 10, were used to examine three cropping treatments in a replicated plot design in 1998 and 1999. Treatments were downslope cultivation (control), contour cultivation and contour cultivation plus straw mulch. In addition, there was an unreplicated bare plot in each group. Runoff and soil loss were measured on a storm-by-storm basis. Soil nutrient status was measured at the beginning and end of each cropping season. Crop growth parameters and soil physical properties were measured throughout the cropping seasons (21/05–7/10 in 1998 and 22/05–2/10 in 1999). In 1998, seasonal rainfall was 1024 mm, ~28% greater than the 30-year mean. Soil loss was significantly reduced by contour cultivation on Slopes I and II. On Slope I, downslope cultivation produced 3.07 t ha-1 soil loss and contour cultivation reduced this by 81.4 %. On Slope II, downslope cultivation produced 19.11 t ha-1 and contour cultivation reduced this by 58.0%. The addition of straw mulch gave a further, nonsignificant, reduction on both slopes. On Slope III, downslope cultivation and contour cultivation produced 6.92 and 6.29 t ha-1 of soil loss, respectively, with contour cultivation plus straw mulch having 99.4% less erosion than downslope cultivation. In the much drier 1999 season, no treatment significantly reduced soil loss on Slope I. Contour cultivation significantly reduced soil loss on Slopes II and III. On Slope II, downslope and contour cultivation produced 11.52 t ha-1 of soil loss and contour cultivation reduced this by 85.8%. On Slope III, downslope and contour cultivation produced 8.62 and 0.23 t ha-1, respectively; a reduction of 97.3% by contour cultivation. The addition of straw mulch did not further decrease soil loss. Treatment effects on soil nutrient status varied between the two years. At the end of the 1998 season, there was significantly higher soil available N under contour cultivation plus straw mulch on all three slopes (Slopes I and II P <0.001, Slope III P <0.05), an effect that was not found in 1999. At the end of the 1999 season, soil available K was significantly (P <0.001) higher under contour cultivation plus straw mulch on Slope III. In both years, contour cultivation plus straw mulch significantly reduced soil temperature. However, this did not result in yield reductions in comparison with the control. There was an increase in soil moisture content under contour cultivation plus straw mulch during dry periods, which was particularly noticeable in 1999. In 1998, there were no significant treatment effects on grain or shoot yield. In 1999, on Slope II, contour cultivation plus straw mulch significantly increased grain yield by 50.3% compared with the downslope treatment (P <0.05). In 1999, contour cultivation plus straw mulch also significantly increased leaf plus stem yield on Slopes I and II by 12.4 and 36.8%, respectively. It is concluded that on ≤10° slopes, contour cultivation alone is a suitable soil conservation measure. However, use of straw mulch would benefit soil moisture and nutrient status and could, therefore, increase crop yield. On ≥27° slopes, it is recommended that contour cultivation plus straw mulch be used as a soil conservation measure to ensure maximum soil conservation, even in extreme rainfall conditions.
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Philibert, Marie Catherine Raïssa. "A comparative study of nitrogen uptake and nitrification rates in sub-tropical, polar and upwelling waters." Doctoral thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16794.
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Includes bibliographical referencesNitrification is the oxidation of ammonium to nitrate through a two step biological process. Nitrification in the euphotic zone has, in the past, been considered negligible even though quantifying this process correctly is important when linking carbon export to nitrate uptake by phytoplankton. However, studies of both nitrogen uptake and nitrification rates in surface waters are rare. This thesis presents such data for the Southern Ocean and St-Helena Bay, located in the Southern Benguela upwelling system. Using 15N tracers, Nitrogen uptake and regeneration rates were measured in the Southern Ocean (during a winter cruise in July 2012 and a summer cruise in February-March 2013) and St-Helena Bay (during three studies in November 2011, March 2012 and March 2013). In St-Helena Bay, the upwelling (bloom) cycle was one of the main drivers of the nitrogen cycle. As the bloom cycle started, nitrate uptake rates (5:47 ± 670:48nmol∙L⁻¹∙h⁻¹) and nitrite regeneration (4:36 - 1:28 ± 22:83 - 1:63nmol∙L⁻¹∙h⁻¹) were high but the contribution of nitrification to the nitrate demand was low. Nitrite regeneration at this time could have been driven by phytoplankton excretion. In contrast, at the end of the bloom cycle, nitrate uptake rates were low and was exceeded by nitrate regeneration rates (25:34 - 6:16 ± 82:74 - 34:41nmol∙L⁻¹∙h⁻¹). Nitrite regeneration decreased and was most likely due to ammonium oxidation at this stage of the upwelling cycle. Nitrification in the Southern Ocean was more variable than in St-Helena Bay. It was only detected at five stations out of fifteen and the accuracy of the high nitrite oxidation rates (37:21 - 9:13 ± 217 - 88nmol∙L⁻¹∙h⁻¹) observed can only be assessed with repeat measurements. Nitrate uptake rates ranged from 0.07 to 57:00nmol∙L⁻¹∙h⁻¹ while ammonium uptake rates ranged from 0.81 - 160:94nmol∙L⁻¹∙h⁻¹. The nitrogen uptake rates were similar for both seasons. Using multivariate statistical approach, it was found that during winter, in the Southern Ocean, light and ammonium availability were the most important factors regulating nitrogen uptake while in the late summer, changes in the mixed layer depth had a larger effect. This study provides new observational data for two undersampled regions and contributes to further the mechanistic understanding of the factors regulating nitrogen uptake and nitrification in the Southern Ocean and St-Helena Bay.
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Roberts, David Thomas. "Trophic Implications of Drought on a Sub-Tropical Reservoir Food Web: Lake Samsonvale (North Pine Dam)." Thesis, Griffith University, 2012. http://hdl.handle.net/10072/367026.
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This thesis provides new insights into the ecological functioning and trophic dynamics of a sub-tropical reservoir during a period of extreme hydrological variability. Australia is one of the driest continents on earth with the majority of its urban population relying on reservoirs for potable water supplies. Despite the importance of reservoirs in Australia, very little is known about the ecological functioning and trophic dynamics of these artificial ecosystems. This thesis investigates the trophic structure, dominant trophic interactions, key drivers of trophic dynamics and the influence of drought on these ecosystem features within a regionally important drinking water reservoir in South East Queensland, Lake Samsonvale (27º 16º S, 152º 56º E).
Food web conceptual diagrams provide a means for describing resource-consumer relationships within an ecosystem and can highlight the importance of certain interactions between the biotic and abiotic components of the system in the flow of energy. Carbon and nitrogen are two elements that form the currency of these interactions. This study utilised stable isotopes of carbon and nitrogen to describe the food web and investigate the trophic dynamics under contrasting hydrologic conditions within Lake Samsonvale. The application of stable isotopes for describing the Lake Samsonvale food web conformed to a number of important prerequisites to successfully apply this technique. These included sufficient isotopic separation between available energy sources and between food web components such that they occupy unique carbon and nitrogen isotopic space. Secondly, isotope values of food web components were found to change in predictable ways according to the basic principles of isotope fractionation and mixing, including conservative δ13C fractionation, and trophic level δ15N enrichment. Additionally, isotopic description of diets of many Lake Samsonvale consumers conformed to literature based description of diets.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Chaston, Katherine A. V. "Sediment nutrient bioavailability in a sub-tropical catchment dominated by agriculture : the transition from land to sea /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17118.pdf.
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Nowosielski, Kara L. "Distribution and Significance of Fecal Indicator Bacteria in Beach Sand and Seawater in a Sub-Tropical Environment." NSUWorks, 2005. http://nsuworks.nova.edu/occ_stuetd/248.
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Gastroenteritis, upper respiratory complaints and dermatological infections can all result from swimming in sewage polluted waters. Current United States Environmental Protection Agency (EPA) guidelines require that recreational beaches are routinely tested for the presence of sewage contamination. Fecal indicator bacteria, such as Escherichia coli, fecal coliforms, and enterococci, are all intestinal microflora of warm-blooded animals and are the indicators of choice. It is assumed that high concentrations of these organisms in water imply fecal contamination and hence warn of health risk to swimmers. Although local Health Departments routinely assess the quality of beach water, they do not test the sand. 1bis is surprising since most beachgoers spend more time in contact with sand than water.
The present study was part of a two-year project funded by the EPA designed to assess the microbiological quality of beach sand and its possible health risks. Over a ten-month sampling period, water, wet sand, and dry sand samples were collected and the levels of enterococci and fecal coliforms were compared at two South Florida beaches. Levels of fecal indicators were consistently higher in the dry sand relative to the wet sand and were lowest in water. An attempt to source track these indicators using the Biolog identification system suggested that bacteria in sand were from multiple sources. There was, however, some evidence to suggest that gull droppings and land runoff were major inputs to the beach. Surprisingly, offshore sewage outfalls were not found to be a major source in this study. Microspatial sampling of beach sand showed patchy distribution of enterococci. Gull droppings, which provided dense localizations of bacteria, and the subsequent translocation of enterococci through the activity of beachgoers probably accounted for most of the heterogeneity in the dry sand. Enterococci in the wet sand were more evenly distributed presumably due to the normalizing effect of wave action The swash zone, close to the area where water managers collect samples for analysis, had much higher counts of enterococci than 10m offshore. This was due to wave action washing enterococci from the sand into the water column.
Research by colleagues showed that enterococci displayed enhanced survival and growth in the sand and suggested that they should be referred to as 'environmental' enterococci. The delineation between environmental and pathogenic bacteria in the sand was investigated in this study using a molecular approach. Polymerase Chain Reaction (PCR) was shown to be able to detect pathogenic Salmonella in beach sand. However, no clear relationship was apparent between the presence of pathogens on the beach and the numbers of indicator bacteria enumerated by traditional methods. Moreover, results from a health survey conducted at the study beaches showed no obvious health risks associated with exposure to beach sand. It is likely that sand fecal indicator bacteria are predominately 'environmental' and that when these bacteria are washed into the swash zone, they could lead to unwarranted beach closures. It is recommended that water managers should consider sampling beyond the current testing depth of 3 ft (1 m) to avoid the detection of enterococci from the sand.
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Abdullah, M. M. "Thermal performance and design of buildings in the sub-tropical dry climate with particular reference to Damascus." Thesis, Cardiff University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354737.
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Hill, Polly Georgiana. "Bacterioplankton dynamics in surface waters of the north-eastern (sub-)tropical Atlantic Ocean affected by Aeolian dust." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/168937/.
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The microbial community dominates biogeochemical cycling of the ocean, affecting global climate. The impact of physical disturbance of near surface microbial populations was studied in the northeastern tropical and subtropical Atlantic Ocean. This region lies beneath easterly trade winds, resulting in strong perturbations in terms of wind driven mixing and Aeolian dust deposition. Firstly, the region’s surface water bacterioplankton community was compared with adjacent regions in terms of metabolic activity, by measuring the uptake rates of radioactively labelled amino acids (3H-leucine and 35S-methionine) as a proxy for bacterial production. Remarkably, there was little variation in uptake rates between the two Atlantic (sub-)tropical gyres. Rates reflected regional photosynthetic biomass, except in the study region. The bacterioplankton community of this region was less metabolically active than that of the oligotrophic north Atlantic gyre, despite ocean colour data identifying the region as productive. The region’s uniqueness is probably related to the episodic Saharan dust inputs experienced. To test whether dust deposition controls microbial community structure, surface communities were compared, using flow cytometry and fluorescence in situ hybridisation, between two winter periods when either wind-driven mixing or dust deposition occurred. Wind-driven mixing was associated with domination by the ubiquitous SAR11 clade of Alphaproteobacteria, whereas key primary producers, Prochlorococcus cyanobacteria, numerically dominated during calmer conditions. Phytoplankton-associated Bacteroidetes and Synechococcus cyanobacteria were most abundant during turbulent conditions. Gammaproteobacteria, encompassing opportunistic species, were the only group to benefit from dust inputs; thus dust deposition seems to have a minor influence on the region’s bacterioplankton community compared to wind mixing, suggesting community change following dust storm events may be linked to nutrients delivered by wind mixing, as much as from dust. To test further whether changes in the SAR11 and Prochlorococcus populations varied between years due to wind- or dust-related perturbation, a method based on 35S-methionine uptake was developed for measuring the metabolic response of these groups to Aeolian dust, whilst excluding wind impacts. Subsurface seawater samples were treated with freshly collected dust, added directly or indirectly as a “leachate” after its rapid dissolution in deionised water. Prochlorococcus and SAR11 cells were sorted by flow cytometry to determine their group-specific responses. Both Prochlorococcus and SAR11 were metabolically impaired by the addition of dust, which may explain the low metabolic activity observed in the region (mentioned above). Although SAR11 showed minor positive responses to dust leachate additions, leachate proved detrimental to Prochlorococcus. Thus dust dissolution in situ appears to be more deleterious to Prochlorococcus than SAR11 and hence could initiate a compositional shift in the indigenous bacterioplankton, suggesting the observed switch from SAR11- to Prochlorococcus-domination following dust deposition (mentioned above) was indeed a result of an alternative stimulus, most likely wind stress. In conclusion, whereas dust deposition may prove beneficial to bacterioplankton species with high nutrient demands, such as some Gammaproteobacteria, it does not appear to affect the ambient dominant bacterioplankton groups of the northeast (sub-)tropical Atlantic to the same degree as wind-driven perturbations. Furthermore, large dust deposition events may prove detrimental to ambient populations, resulting in low community metabolic activity.
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Pétriglieri, Jasmine Rita. "Alteration of asbestiform minerals under sub-tropical climate : mineralogical monitoring and geochemistry. The example of New Caledonia." Electronic Thesis or Diss., Nouvelle Calédonie, 2017. http://portail-documentaire.unc.nc/files/public/bu/theses_unc/These_Jasmine_Petriglieri-derniere_version_these.pdf.
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Sous climat humide tropical ou subtropical, les processus d'altération supergène sont les principaux responsables de la formation et de la libération des fibres d'amiante dans l’environnement. Plus du tiers de la Nouvelle Calédonie est recouvert d’unités ultrabasiques altérées, riches en minerai de Ni. L’exploitation minière du Ni doit composer avec la présence d’affleurements d’amiante et de minéraux fibreux de type serpentine et amphibole. Dans ce contexte, les sociétés minières doivent prévenir les risques sanitaires liés à l'exposition environnementale aux fibres minérales. Actuellement, il n'existe pas de technique analytique capable de caractériser instantanément une fibre d'amiante in situ, en fournissant des informations sur la distribution de taille, la morphologie, la composition chimique et le degré d'altération associés. Cependant, la connaissance de tous ces paramètres est nécessaire pour évaluer le risque sanitaire associé à l'exposition. L'utilisation des dispositifs portable tels quels la Microscopie Optique à Lumière Polarisée (MOLP) et la spectrométrie Raman représente la stratégie la plus efficace pour améliorer l'acquisition et l'interprétation des données, y compris pour les échantillons fortement fibreux et altérés. De plus, des analyses géochimiques préliminaires ont révélé que l'effet mécanique de la circulation des fluides entre les fibres et lamelles, associé à la lixiviation chimique des éléments à l'interface roche/eau, favorisent la dissociation des fibres et leur libération dans l'environnement. Un focus a été réalisé sur l'antigorite fibreuse, reconnue comme amiante uniquement dans la réglementation calédonienneUnder humid tropical to sub-tropical conditions, weathering processes and supergene mineralization are the main responsible for genesis and release of asbestos fibres. The New Caledonia is one of the largest world producers of Ni ore that is formed by the alteration of ultramafic rocks. Almost all outcrops of geological units and open mines contain serpentine and amphibole, also as asbestos varieties. Mining companies must therefore deal with the health concerns related to environmental exposure to mineral fibres. At present, there is not a technique capable to instantly characterize an asbestos fibre in situ, providing information about size and distribution, morphology, chemical composition and alteration grade. However, the acquisition of all these parameters is necessary for determining the health risk associated to fibre exposition. The employment of specialized tools such as Polarized Light Microscopy associated to Dispersion Staining (PLM/DS) and portable Raman spectroscopy has proved extremely effective in the improvement of performance and rapidity of data acquisition and interpretation, even in the presence of strongly fibrous and altered samples. Regardless of the alteration state, a great variability in morphology was observed (SEM investigation). Preliminary geochemical analyses have proved that the physical-mechanical effect of fluid circulation within the porous of fibres and lamellae, associated to chemical elemental exchange at rock/waters interface, favoured the dissociation of fibres and their release in the environment. A focus was set on fibrous antigorite, recognized as asbestos only by Caledonian legislation, but still not by European law
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Posselt, Amanda J. "Are Nutrients the Key Driver in Prompting Dominance of Toxic Cyanobacterial Blooms in a Sub-Tropical Reservoir?" Thesis, Griffith University, 2010. http://hdl.handle.net/10072/367306.
Full textAbstract:
Toxic cyanobacteria cause major problems, both for drinking and recreation, within
water systems and bulk water storages, worldwide. Many investigations have been
conducted to determine how, and why, they proliferate as well as why, and when, they
produce toxins. A common assumption is that cyanobacteria grow in response to an
increase in water column nutrient availability, but this is an oversimplification.
In a sub-tropical reservoir (L. Samsonvale, South East Queensland, Australia), the
toxic cyanobacterium Cylindrospermopsis raciborskii has been dominating the
phytoplankton community in the summer months for many years. The reason for this
is unknown. Lake Samsonvale typically has relatively low phosphorus (P)
concentrations, relatively high nitrogen (N) concentrations and C. raciborskii can
grow without significant nutrient inputs from the catchment or point sources. The
relatively high N concentrations in L. Samsonvale mean that it is unlikely to be a key
nutrient in promoting dominance of C. raciborskii. The low phosphorus (in particular
the phosphate) concentrations on the other hand may suggest a reason for
C. raciborskii dominance in L. Samsonvale. Studies of a non-toxic strain of
C. raciborskii originally isolated from the northern hemisphere found that a rapid
phosphate uptake rate and high phosphorus storage capacity was contributing to its
dominance in a phosphate-limited reservoir (Istvánovics et al. 2000).
The aim of this thesis was to characterise the relationship between phosphorus and
C. raciborskii in L. Samsonvale. To achieve this, three levels of investigation were
used: 1. Physiological studies at the species level; 2. Manipulative experiments at the
phytoplankton community level; 3. Characterisation of C. raciborskii ecology at the
whole of system level.
The relationship between C. raciborskii and phosphorus was studied using a
multilevel approach. Knowledge gained from this allowed detailed investigation of
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the relationship between the dominance of this species within the phytoplankton
community of L. Samsonvale.
Using continuous culture experiments, the phosphate uptake and storage capacity of
two toxic Australian strains of C. raciborskii was determined. One of these strains
was isolated from the reservoir of interest, L. Samsonvale. P dependent growth rate
and toxin production were also quantified. Both strains of C. raciborskii had a high
maximum phosphate uptake rate (450 – 600 μmol P mg C-1 d-1) with a relative low
half saturation constant (0.64 μmol P L-1). This study suggests that C. raciborskii is
capable of taking full advantage of any available phosphate that may be introduced
(such as run off) or regenerated within the phytoplankton/bacterial community. The P
dependent growth rates were similar for both strains of C. raciborskii with a
maximum growth rate at the lowest concentration of P tested (0.03 μmol P L-1).
Growth rates were lower overall than in other strains of C. raciborskii. When
C. raciborskii cells were starved of P, they produced much more toxin than when they
were grown in a nutrient sufficient environment. This indicates that toxin production
may be related to a stress response.
Some phytoplankton have been shown to produce alkaline phosphatase. This enzyme
cleaves phosphate from organically bound forms, targeting esters, which can be taken
up and used by the cell. Since C. raciborskii appears to proliferate in phosphate
limited systems, its potential to secrete this enzyme, and whether it was capable of
growth with an organically bound source of phosphate, were investigated. Alkaline
phosphatase activity was detected and C. raciborskii was found to be capable of
multiplying in a culture media containing only an organic form of P (glucose-6-
phosphate, G-6-P). However, the maximum growth rate was lower (~0.13 d-1) when
cells were grown in G-6-P compared to phosphate (~0.22 d-1) The ability of
C. raciborskii to use: 1. Organic P; 2. Rapidly utilise phosphate; and 3. Grow at a
maximum rate at relatively low phosphate concentrations, are likely to make
C. raciborskii a dominant competitor in phosphate-limited systems.
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To determine whether C. raciborskii has a competitive advantage over other
phytoplankton in the P-limited system of L. Samsonvale, in situ dialysis tube
bioassays were used to test the phytoplankton response to nutrient addition. The
dialysis tube bioassay is a novel approach aiming to minimise the confounding
problem of artificial nutrient limitation associated with traditional closed bottle
bioassays. Samples of the phytoplankton population were subjected to nutrient
additions at four different times over a summer period, to test whether a change in
phytoplankton species composition (with particular reference to C. raciborskii) could
be seen after four days. In phytoplankton communities where the proportion of
C. raciborskii was equal to, or above, 50% (biovolume), a statistically significant
increase in C. raciborskii dominance occurred when phosphate was added as a daily
spike at either of two concentrations (0.32 and 16 μM P). However, C. raciborskii
dominance decreased when phosphate was constantly added in very high
concentrations or when N and P are added together. From the bioassay experiments it
can be inferred that C. raciborskii has a competitive advantage in L. Samsonvale due
to its ability to rapidly take up phosphate. But, when the phosphate concentration is
constantly high (>6.4 μmol P L-1), C. raciborskii loses this competitive advantage.
Analysis of historical data has shown that there is no correlation between periodic
nutrient inputs (e.g. rainfall) and an increase in C. raciborskii dominance. The
mechanisms by which C. raciborskii is accessing phosphate within L. Samsonvale
were therefore examined.
One theory about how C. raciborskii is accessing phosphate in L. Samsonvale is that
it comes from nutrient injections in the bottom waters caused by mixing the reservoir
using artificial destratification. The concentration of dissolved organic phosphorus
(DOP) may also provide C. raciborskii with available phosphate. To assess these two
hypotheses, the nutrient concentration and phytoplankton cell concentrations
throughout the water column were measured, both before and after artificial
destratification. The DOP fraction was measured over a summer. Phosphate remained
v
below detection limits throughout the study, therefore the role of the destratifier in
injecting phosphate into the water column was difficult to determine. A difference in
phytoplankton distribution was noted with C. raciborskii being found at higher
concentrations lower in the water column post destratification. In contrast, the other
toxic species of cyanobacteria Microcystis aeruginosa present in substantial cell
concentrations significantly decreased in cell concentrations after the destratifier was
turned on. DOP was found to be a significant fraction (total mean 32%) of the total P
in the water column of L. Samsonvale and may therefore provide an important source
of P for C. raciborskii under low phosphate conditions.
This study has shown C. raciborskii has adapted to the low concentrations of P in
L. Samsonvale to gain a competitive advantage. Reservoir management, particularly
in relation to nutrient loads, should take this into account, as efforts to reduce P loads
may not lead to a decrease in C. raciborskii cell number or phytoplankton dominance.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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SILVA, Mariana Brito. "Estoques de carbono e nitrogênio e disponibilidade de nutrientes em sistemas silvipastoris em região tropical sub-úmida." Universidade Federal Rural de Pernambuco, 2017. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/7325.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Livestock is an activity of extensive use of large production areas without replacement of soil fertility, and may contribute to the degradation of pastures. Thus, silvopastoral systems, which integrate in the same area, tree species, pastures and animals are being adopted to improve the microbiological, chemical and physical attributes of the soil, aiming to increase agricultural productivity. In this aspect, the carbon stock, the nutrient cycling and microbial activity was evaluated in the soils of Brachiaria decumbens Stapf. in a consortium with Gliricidia (Gliricida sepium Jacq. Steud) and Sabiá (Mimosa caesalpiniifolia Benth) in the Forest Zone Pernambuco area. Soil samples were collected in dry and rainy seasons up to 100 cm depth at 0, 4 and 8 m of legume range for chemical analysis, and up to 20 cm at 0, 2, 4, 6, and 8 m from the legume range, for microbiological analyzes. It was determined the carbon stock and evaluated the carbon and total organic nitrogen contents (CTO and N-total), carbon of the soil microbial biomass (C-SBM), macro element contents and the fractionation of the organic matter of these soils. The microbial activity was based on basal respiration of the soil (BRS), allowing to evaluate the metabolic quotient. For the C-SBM, the Brachiaria monoculture and the consortium with Gliricidia and Sabiá were statistically similar in depth 0-10 cm, already in BRS. The value of basal respiration in the treatment of brachiaria was superior to the other treatments at depth 0 -10 cm, and the biological evaluations, for the metabolic quotient, Brachiaria monoculture treatments consortium with Gliricidia and Sabiá presented similar behavior. For the quantification of CTO, the consortium of Braquiária and Sabiá had values significantly higher in the 0-10 cm layer, both in the dry season and in the rainy season. For the treatment of consortium between Braquiária and Sabiá, only the distance of 4 m showed lower values of total N. The Braquiaria consortium with Sabiá showed higher values in C stocks at all distances of the legume range. In the quantification of Carbon of the organic matter fractions, the Brachiaria + Gliricidia treatment presented higher values in humic and fulvic acid fractions. In the humina fraction, the Braquiária was superior to the consortiums with Gliricídia and Sabiá. It is noticed that during the seven years, from the implantation, the three managements adopted resembled the biological activity of the soil, but, for the values of C and N total, the consortium with the legumes provided the highest values. The consortium with Sabiá demonstrated potential for soil C inventory. Already for C in the organic matter fractions, Brachiaria and Gliricidia were superior to the other treatments.
A pecuária é uma atividade de uso extensivo de grandes áreas de produção, que com o manejo incorreto das pastagens, como a ausência de reposição de nutrientes, torna-se o principal responsável pela alta proporção de pastagens degradadas observada em todas as regiões do Brasil. Assim, os sistemas silvipastoris, que integram em uma mesma área espécies arbóreas, pastagens e animais, estão sendo adotados para melhorar os atributos microbiológicos, químicos e físicos do solo, visando o aumento de produtividade agrícola. Neste trabalho, foi determinado os estoques de carbono e nitrogênio, avaliada a disponibilidade de nutrientes e atividade microbiana em solo cultivado com braquiária (Brachiaria decumbens Stapf.) em consórcio com gliricídia (Gliricida sepium Jacq. Steud) e sabiá (Mimosa caesalpiniifolia Benth) na zona da Mata de Pernambuco. Foram coletadas amostras de solo em época seca e chuvosa, até 100 cm de profundidade aos 0, 4 e 8 m de distância da faixa de leguminosa para análises químicas, e até 20 cm em pontos de 0, 2, 4, 6, e 8 m de distância da faixa de leguminosa, para análises microbiológicas. Foi determinado o estoque de carbono e nitrogênio e avaliado os teores de carbono orgânico total (COT) e nitrogênio total (N-total), carbono da biomassa microbiana (C-BMS), teores de macro elementos e realizado o fracionamento da matéria orgânica desses solos. Para o C-BMS, o monocultivo de braquiária e o consórcio com gliricídia e sabiá foram semelhantes estatisticamente na profundidade 0-10 cm. A respiração basal no tratamento com braquiária foi superior à dos demais manejos na profundidade 0-10 cm. Para o quociente metabólico, os tratamentos de monocultivo de braquiária consorciada com gliricídia e sabiá, apresentaram comportamento semelhante. O consórcio de braquiária e sabiá apresentou valores de COT significativamente superior na camada 0-10 cm, nas duas épocas avaliadas. No consórcio entre braquiária e sabiá, apenas a distância de 4 m apresentou menores valores de N total. O consórcio de braquiária com sabiá apresentou maiores valores nos estoques de C em todas as distâncias da faixa de leguminosa. Na quantificação de carbono das frações da matéria orgânica, o tratamento braquiária + gliricídia apresentou maiores valores nas frações de ácidos húmicos e fúlvicos. Já na fração humina, a braquiária foi superior aos consórcios com gliricídia e sabiá. Percebe-se que ao longo desses sete anos, a partir da implantação, os três manejos adotados assemelharam-se na atividade biológica do solo, mas, para os valores de C e N total o consórcio com as leguminosas proporcionaram os maiores valores. O consórcio com sabiá demonstrou potencial quanto ao estoque de C no solo. Já para C nas frações da matéria orgânica, braquiária e gliricídia foram superiores aos demais manejos. A adoção de leguminosas em sistema silvipastoril, foram superiores quanto aos valores de N total e estoque de N em época chuvosa.
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Nguyen, Dai Huong. "Influence of organic amendments on greenhouse gas emissions and N use efficiency in sub-tropical cropping systems." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/91549/4/Dai_Huong_Nguyen_Thesis.pdf.
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This thesis investigated the impact of organic sources of nutrients on greenhouse gas emissions (carbon dioxide, nitrous oxide and methane), nitrogen use efficiency and biomass production in subtropical cropping soils. The study was conducted in two main soil types in subtropical ecosystems, sandy loam soil and clay soil, with a variety of organic materials from agro-industrial residues and crop residues. It is important for recycling of agro-industrial residues and agricultural residues and the mitigation of greenhouse gas emissions and nitrogen use efficiency.
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Bito, Darren. "Structure and Dynamics of Herbivore Assemblages Along an Altitudinal Gradient: Indicators of Climate Change." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/366400.
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Herbivory is one of the major ecosystem processes, as are pollination and seed dispersal, which drives ecological changes in both the phytophagous fauna and their host plant assemblages. The amount of herbivory damage on a host species represents not only the amount of herbivory pressure due to phytophagous insects but also the predatory pressure due to predators at higher trophic levels. Furthermore, additional interactions of climate and environmental factors determine the conditions of the host species and subsequently the assemblage of herbivorous insects that colonize them. All these direct and indirect, positive and negative influence of climate and environmental factors combined with the requirement to propagate themselves cascades to through the higher trophic levels down to assemblage of herbivorous insects and their host species at the lower trophic levels. This study considered the host specificity of caterpillars, herbivory pressure and herbivory damage on trees and shrubs along an altitudinal gradient within subtropical and temperate rainforest. The work has attempted to show how a selected ecological process (herbivory) is being influenced by various factors including altitude, ant predation pressure and host plant species, canopy strata and physical properties of leaves.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Arts, Education and Law
Science, Environment, Engineering and Technology
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Vosloo, Mathys Christiaan. "Network analysis of trophic linkages in two sub-tropical estuaries along the South-East coast of South Africa." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1010966.
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Estuaries are some of the most productive yet threatened ecosystems in the world. Despite their importance they face significant threats through changes to river flow, eutrophication, rapid population growth long the caost and harvesting of natural resources. A number of international studies have been conducted investigating the structure and functioning of an array of ecosystems using ecological network analysis. Energy flow networks have been contsructed for coastal, lagoonal, intertidial and, most notably, permantently open estuaries. Despite the valualble insights contributed by these and other studies, a lack of information on the majority of estuarine ecosystems exists.
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Nicoloso, Rodrigo da Silveira. "Estoques e mecanismos de estabilização do carbono orgânico do solo em agroecossistemas de clima temperado e sub-tropical." Universidade Federal de Santa Maria, 2009. http://repositorio.ufsm.br/handle/1/3574.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoSoil carbon (C) sequestration in agriculture soil is a low cost option to mitigate global climatic change. No-till (NT) associated with good husbandry practices could compensate up to 15% of the anthropogenic CO2 emissions by storing the C from atmosphere as soil organic carbon (SOC). To be fully accepted as a mitigation alternative, research must be conducted to improve the accuracy of soil C sequestration estimates on field experiments as well as those made by mathematical models at regional and local scales. Complementarily, is necessary to improve the knowledge about the SOC stabilization mechanisms, delimiting the real soil´s capacity into accumulate C, quantifying how much of the stored C could be re-emitted to the atmosphere by changes in soil management. The present work is divided in four chapters with the objective to answer these questions. The first chapter has the objective to discuss the importance of sampling depth (0-0.30, 0-0.60, and 0-0.90 m) and the definition of a reliable and adequate baseline for the calculation of the C sequestration rates. Two long-term field experiments from a temperate (Mollisol) and a sub-tropical (Oxisol) climate soil were selected for this research. The experiments tested soil tillage systems (conventional tillage (CT) and NT) (Mollisol and Oxisol) and sources and rates of nitrogen amendment on corn in the Mollisol (control without N, 168 kg N ha-1 as ammonium sulfate, and 168 kg N ha-1 as organic fertilizer) and different crop rotation systems in the Oxisol (R0:soybean-wheat, R1:soybean-wheat-soybean-oat, and R2:soybean-oat-soybean-oat+vetch-corn-radish-wheat). The increase of sampling depth provided limited contribution to the estimates of C sequestration rates due to the increase of the error on SOC stocks estimates at deeper soil depths. To improve the C sequestration rate estimates, SOC temporal dynamic analysis should be preferred rather than the comparison of the SOC stocks of paired plots at a unique time point. The second chapter had the objective to apply simple mathematical equations to describe the SOC dynamics and improve the estimates of C sequestration rates and also to understand the role of the macroaggregate formation on SOC accumulation and saturation. The use of linear and kinetic (exponential growth) equation was adequate to describe the SOC dynamics increasing the accuracy of the C sequestration rate estimates by reducing errors promoted by soil spatial variability. The SOC accumulation was a function of the amount of C input to the soil and the macroaggregate formation to protect SOC. The SOC saturation process occurred from the smaller to the larger aggregate size fraction, limiting the capacity of a given superficial soil layer to accumulate SOC. However, the SOC saturation at superficial soil layers did not indicate the end of C sequestration in the soil, since the SOC accumulation occurred at sub-superficial soil layers. In the third chapter, the mathematical approach to determine changes on SOC stocks and the SOC saturation-induced limitation for C sequestration were applied to improve the accuracy of the Hénin e Dupuís (1945) one- 8 compartmental mathematical model into predict future soil C sequestration rates. The long-term field experiment from the Mollisol was selected for this research because of the better data availability (sampling years) and also by the presence of two treatments under CT and NT with SOC saturated soil layers. The mathematical adjustment (by linear equations) of the SOC dynamic coefficients improved the adjustment of the model‟s predictions. The SOC saturation-induced restriction for SOC accumulation on the mathematical model avoided the overestimation of the soil‟s potential for C sequestration. The predictions of the mathematical models indicate that the Mollisol‟s superficial layer (0-0.05 m) under NT could maintain significant C sequestration rates for up to 50 years as a function of the amount of C input to the soil. For the fourth chapter, a detailed study of the SOC pools in water-stable aggregate size fractions by granulometric and densimetric fractionation was carried out. The objective was to identify the pools where SOC accumulation was occurring and what SOC stabilization mechanisms were present. This will provide estimates of the NT potential to promote long-term C sequestration. SOC accumulation occurred preferentially in the more stable and recalcitrant SOC fractions (Mollisol and Oxisol) or in microaggregate and macroaggregate physically protected fractions (Mollisol). In the Oxisol, the SOC enrichment occurred mostly in the mineral associated-SOC fractions extra-microaggregates occluded within meso- and macroaggregates, while in the Mollisol, the SOC accumulation occurred in both intra- and extra-microaggregate mineral associated-SOC fractions. More than 78 and 92% of the C sequestration verified in the Mollisol and Oxisol, respectively, were considered as long-term by occurring in stable SOC fractions.
O seqüestro de carbono (C) em solos agrícolas é uma opção de baixo custo para mitigação das mudanças climáticas globais. O plantio direto (PD), associado a boas práticas agronômicas, pode compensar até 15% das emissões antrópicas de CO2 ao armazenar o C drenado da atmosfera na forma de carbono orgânico (CO) do solo. Para ser amplamente aceito como alternativa de mitigação, pesquisas devem ser conduzidas a fim de melhorar a precisão das estimativas de taxas de seqüestro de C em experimentos de campo, assim como as previsões feitas por modelos matemáticos em escalas regionais e locais. Complementarmente, é necessário aprimorar o conhecimento sobre os mecanismos de estabilização do CO, delimitando a capacidade real do solo em acumular C e quantificando quanto do C acumulado no solo pode ser re-emitido para atmosfera por mudança no manejo do solo. Desta maneira, o presente trabalho se divide em quatro capítulos com o objetivo de abordar estas questões. O primeiro capítulo tem por objetivo discutir a importância da profundidade de amostragem (0-0,30; 0-0,60; 0-0,90 m) e da definição de situações de linhas-base confiáveis a adequadas para o cálculo das taxas de seqüestro de C. Para isto, foram utilizados dois experimentos de longa duração sobre um solo de clima temperado (Mollisol) e outro de clima sub-tropical (Oxisol). Os experimentos testaram efeitos de sistema de preparo do solo (preparo convencional (PC) e PD) (Mollisol e Oxisol) e fontes e doses de nitrogênio para o milho no Mollisol (testemunha (T), 168 kg N ha-1 na forma de sulfato de amônia (AM) e 168 kg N ha-1 na forma de adubo orgânico (AO)) e diferentes sistemas de rotação de culturas no Oxisol (R0:soja-trigo, R1:soja-trigo-soja-aveia e R2:soja-aveia-soja-aveia+ervilhaca-milho-nabo-trigo). O aumento da profundidade de amostragem não contribuiu com a melhoria das estimativas de taxas de seqüestro de C devido ao aumento do erro nas estimativas dos estoques de CO nas camadas mais profundas de solo. Para melhoria das estimativas das taxas de seqüestro de C devem-se preferir análises temporais da dinâmica do CO no solo ao invés da comparação de estoques de CO em um único momento. O segundo capítulo tem por objetivo aplicar equações matemáticas simples para descrever a dinâmica do CO e melhorar as estimativas taxas de seqüestro de C e também entender o papel da formação de macroagregados no acúmulo e saturação de CO no solo. O uso de equações lineares e cinéticas (crescimento exponencial) foi adequado para descrever a dinâmica do CO, aumentando a precisão das estimativas de taxas de seqüestro de C ao reduzir os erros de estimativa por variabilidade espacial do solo. O acúmulo de CO no solo mostrou-se uma função da quantidade de C aportada ao solo por resíduos vegetais e a formação de macroagregados no solo para proteção do CO. O processo de saturação do solo ocorreu das menores para as maiores frações de agregados do solo, limitando a capacidade de uma 6 determinada camada de solo em acumular CO. No entanto, verificou-se que a saturação de camadas superficiais de solo não indica o fim do seqüestro de C neste solo, visto que o acúmulo de CO passa a ocorrer em camadas sub-superficiais. No terceiro capítulo, a aproximação matemática para determinar mudanças nos estoques de CO e a limitação na capacidade do solo em acumular CO promovida pelo processo de saturação dos agregados do solo foram aplicados para melhorar a precisão do modelo matemático uni-compartimental de Hénin e Dupuís (1945) em prever futuras taxas de seqüestro de C. O Mollisol foi escolhido para este estudo em função da maior disponibilidade de dados (anos de amostragem) e também pela presença de dois tratamentos em PC e PD com camada de solo saturada por CO. O ajuste matemático (por equações lineares) dos coeficientes da dinâmica do CO melhorou o ajuste das previsões do modelo com os dados observados. A restrição do modelo matemático quanto à capacidade do solo em acumular CO (saturação de CO) evitou a superestimação do potencial de seqüestro de C deste solo. As previsões do modelo matemático indicam que a camada superficial (0-0,05 m) do solo sob PD pode apresentar taxas significativas de seqüestro de C por até 50 anos, em função da quantidade de C adicionada ao solo. No quarto capítulo, foi realizado um estudo detalhado dos compartimentos do CO em função da sua distribuição em classes de tamanhos de agregados estáveis em água e o fracionamento granulométrico e densimétrico do CO. O objetivo foi identificar em quais compartimentos está ocorrendo o acúmulo de CO no solo, os mecanismos de estabilização do CO, estimando o potencial do PD em promover sequestro de C de longa duração. Verificou-se que o acúmulo de C ocorre preferencialmente em frações mais estáveis e recalcitrantes do CO (Mollisol e Oxisol) ou em frações protegidas fisicamente por micro e macroagregados (Mollisol). No Oxisol, o enriquecimento de CO ocorre principalmente nas frações de CO associadas aos minerais extra-microaggregados oclusas em meso e macroagregados de solo, enquanto que no Mollisol, o acumulo de CO ocorre tanto na fração intra como extra microagregados. Mais de 78 e 92% do seqüestro de C verificado no Mollisol e Oxisol, repectivamente, foi considerado de longa duração por ocorrer em frações estáveis do CO.
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Di, Corleto Ross, and mikewood@deakin edu au. "The Evaluation of heat stress indices using physiological comparisons in an alumina refinery in a sub-tropical climate." Deakin University, 1998. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20050915.124324.
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The production of alumina involves the use of a process known as the Bayer process. This method involves the digestion of raw bauxite in sodium hydroxide at temperatures around 250°C. The resultant pregnant liquor then goes through a number of filtering and precipitation processes to obtain the aluminium oxide crystals which are then calcined to obtain the final product. The plant is situated in a sub tropical climate in Northern Australia and this combined with the hot nature of the process results in a potential for heat related illnesses to develop. When assessing a work environment for heat stress a heat stress index is often employed as a guideline and to date the Wet Bulb Globe Temperature (WBGT) has been the recommended index. There have been concerns over the past that the WBGT is not suited to the Northern Australian climate and in fact studies in other countries have suggested this is the case. This study was undertaken in the alumina plant situated in Gladstone Queensland to assess if WBGT was in fact the most suitable index for use or if another was more applicable. To this end three indices, Wet Bulb Globe Temperature (WBGT), Heat Stress Index (HSI) and Required Sweat Rate (SWreq) were compared and assessed using physiological monitoring of heart rate and surrogate core temperature.
A number of different jobs and locations around the plant were investigated utilising personal and environmental monitoring equipment. These results were then collated and analysed using a computer program written as part of the study for the manipulation of the environmental data . Physiological assessment was carried out using methods approved by international bodies such as National Institute for Occupational Safety & Health (NIOSH) and International Standards Organisation (ISO) and incorporated the use of a Physiological Factor developed to enable the comparison of predicted allowable exposure times and strain on the individual.
Results indicated that of the three indices tested, Required Sweat Rate was found to be the most suitable for the climate and in the environment of interest. The WBGT system was suitable in areas in the moderate temperature range (ie 28 to 32°C) but had some deficiencies above this temperature or where the relative humidity exceeded approximately 80%. It was however suitable as a first estimate or first line indicator. HSI over-estimated the physiological strain in situations of high temperatures, low air flows and exaggerated the benefit of artificial air flows on the worker in certain environments ie. fans.
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Woldetsadik, Kebede. "Shallot (Allium cepa var. ascolonicum) responses to plant nutrients and soil moisture in a sub-humid tropical climate /." Alnarp : Dept. of Crop Science, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/a367.pdf.
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