To see the other types of publications on this topic, follow the link: Plant availability.
Dissertations / Theses on the topic 'Plant availability'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Plant availability.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Russell, L. W. "Computer simulation of process plant availability." Thesis, Teesside University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328836.
Full text
2
Laxton, Emma. "Relationship between leaf traits, insect communities and resource availability." Thesis, Electronic version, 2005. http://hdl.handle.net/1959.14/483.
Full textAbstract:
Thesis (PhD)--Macquarie University, Division of Environmental and Life Sciences, Dept. of Biological Sciences, 2005.<br>Bibliography: p. 178-203.<br>Introduction -- Study sites -- Leaf characteristics and resource availability -- Insect herbivory and resource availability -- Insect communities and resource availability -- Influence of resource availability on recovery from herbivory -- Conclusions.<br>This project used the resource availability hypothesis (Coley et al., 1985) as a framework for investigating the relationship between resource availability (as defined by soil nutrients), leaf traits, insect herbivore damage and insect community structure. According to the hypothesis, plants from low resource environments should be better-defended, have longer leaf lifespans and slower growth rates than plants from higher resource environments. Higher resource plant species are expected to suffer higher levels of herbivory and recover faster from herbivory than low resource plant species (Coley et al. 1985). A corollary to this hypothesis is that plants from higher resource sites should support greater densities of insect herbivores than low resource species. Comparisons between high and low resource sites were made in terms of: (i) leaf traits of mature and immature leaves; (ii) phenology of leaf maturation; (iii) herbivore damage in the field and laboratory; (iv) diversity and abundance of herbivorous insect fauna; and (v) ability to recover from herbivory.<br>Mode of access: World Wide Web.<br>243 p. ill., maps
3
Baethgen, Walter E. "Plant nitrogen availability in selected Virginia soils." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/90907.
Full textAbstract:
Surface and subsoil samples were collected from agriculturally important soils of Coastal Plain, Piedmont and Ridge and Valley regions of Virginia for the purpose of determining the contribution of different soil N fractions to plant available N. Soil samples were analyzed for exchangeable and non-exchangeable NH₄⁺-N, NO₃⁻-N, total N, and organic matter contents. The samples were also subjected to the anaerobic incubation procedure as an index of organic N availability. Plant available N was measured by N uptake of successive wheat crops grown in the greenhouse. Multiple linear regression models for different groups of samples were used to determine the contribution of the different soil N fractions to the plant available N supply, and to predict N uptake by wheat. Best models were selected considering fit, significance of the regression coefficients, and predictive ability. Due to the high correlation among the different soil N fractions, important collinearity was present and affected the linear models. These effects were reduced by utilizing biased techniques. All the soils provided significant amounts of N to the wheat in both the first and second crops. Exchangeable NH₄⁺-N and NO₃⁻-N were the major initial sources of plant available N. Non-exchangeable NH₄⁺-N was also a significant contributor to the plant available N supply for most soils. The results of the biological and chemical indices of organic N availability were highly correlated among each other, and with plant N uptake by the first and second wheat crops. Plant N uptake was associated with the variation observed in the different soil N fractions, indicating that wheat is a good indicator crop for plant N availability experiments. The procedures used to detect and combat collinearity were effective in producing more stable models with better predictive ability. Further research should be conducted under field conditions to study the contribution of non-exchangeable NH₄⁺-N to plant N availability.<br>M.S.
4
Berglund, Linda. "Disturbance, nutrient availability and plant growth in phenol-rich plant communities /." Umeå : Dept. of Forest Vegetation Ecology, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s327.pdf.
Full text
5
Harral, Josephine Erica. "Experiments on resource availability and plant species richness." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415053.
Full text
6
au, 30075885@student murdoch edu, and Ross F. Brennan. "Zinc Application and its Availability to Plants." Murdoch University, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20050602.142302.
Full textAbstract:
Globally, low zinc (Zn) soils are widespread, but one of the largest expanses of such soils is in south west Australia (WA). Early Zn research in the region determined how much fertiliser Zn was required for profitable production of spring wheat (Triticium aestivum L.) and subterranean clover (Trifolium subterraneanum L), the major crop and pasture species at the time. The research showed that Zn sulfate and ZnO were equally effective Zn fertilisers, but ZnO was cheaper and so was widely used. The research indicated that in the year of application, depending on soil type, between 0.5-1.5 kg Zn/ha provided adequate Zn for the production of wheat and subterranean clover. The length of time that a single application of Zn fertiliser remains fully effective in maintaining the production of crops and pasture in future years (residual value; (RV)) had not been determined. This knowledge of the RV of Zn fertilisers is required for soils of WA. The experiments that measured the RV of fertiliser Zn for spring wheat and subterranean clover form the bulk of this thesis.
The soils in the region were also initially acutely phosphorus (P) deficient requiring the application of fertiliser P for profitable production. Single superphosphate was the P fertiliser initially used. It was manufactured locally using phosphate rock imported from Nauru and Christmas Islands. This phosphate rock also contained much Zn, and the single superphosphate manufactured from it contained 400-600 mg Zn/kg. At amounts of application needed to provide adequate P, the Zn-contaminated superphosphate also supplied about 90 g Zn/ha. Therefore, early field experiments measured the RV of ZnO applied to soil when single superphosphate was applied annually at >150 kg/ha. In these experiments, the RV of Zn was measured when different amounts of fertiliser nitrogen (N) was applied. This was because it has recently been very profitable to apply fertiliser N to wheat crops, which greatly increased grain yields and so may have increased the demand for Zn, thereby probably decreasing the RV of the original ZnO application. In these experiments, there were many nil-Zn plots. In subsequent years, freshly-applied ZnO amounts were applied to measure the RV of the original ZnO treatments relative to the fresh Zn treatment. No Zn deficiency was detected for up to 23 years after applying ZnO while applying superphosphate at >150 kg/ha per year and for all amounts of N applied.
Subsequently cheap imported DAP fertiliser was used for wheat crops instead of locally produced Zn-contaminated single superphosphate and urea. The imported DAP contained about 50 mg Zn/kg (1/12 that of single superphosphate). This new fertiliser strategy induced Zn deficiency in many wheat crops. This led to further field studies to determine the RV of ZnO fertiliser when DAP was applied. The experiments also included 2 Zn-contaminated single superphosphate treatments. In one, no ZnO was applied, and superphosphate was applied at >150 kg/ha per year to match the amount of P applied as DAP to the other treatments. The other treatment was the same, except 1.5 kg/ha Zn as ZnO was applied in the first year only. In subsequent years, freshly-applied ZnO amounts were applied to measure the RV of the original ZnO treatments relative to the fresh Zn treatment. Relative to freshly-applied Zn in each year, the RV of the original ZnO treatments decreased as the length of time that the Zn was in contact with soil increased. However, the rate of decline in the RV was also found to differ with soil type, and was affected by soil pH, clay and organic carbon content of soil, and in alkaline soils with the calcium carbonate content of soil.
Parallel glasshouse studies measured the RV of Zn, as Zn sulfate, for wheat and subterranean clover, using many soils from WA and other Australian States. The glasshouse studies also showed that the rate of decline in the RV of the original Zn application varied markedly with soil type and was strongly influenced by soil pH, clay and organic carbon content of soil, and in the alkaline soils, the amount of calcium carbonate in soil.
In the above studies, the RV of fertiliser Zn was measured relative to freshly-applied Zn using yield of plants (shoots and grain for wheat, shoots for clover), Zn content in shoots and grain, and soil test Zn using the ammonium oxalate and DTPA procedures. In addition, Zn concentration in young tissue and rest of shoots (glasshouse studies) and young tissue and whole shoots (field studies) was measured, and Zn concentration related to 90 % of the maximum yield (critical Zn in plant parts) was determined. The studies showed that the DTPA soil test procedure, together with soil pH, and clay and organic matter content of soil, was an accurate prognostic test for indicating when Zn deficiency was likely in the next clover or wheat crop. The study confirmed that young tissue (youngest fully expanded leaves) provided critical plant test values for diagnosing Zn deficiency in plants. The plant and soil tests for Zn are now used by commercial soil and tissue testing laboratories.
When Zn deficiency was diagnosed early in field grown wheat, Zn sprays can be applied to the crop foliage to prevent or minimise decreases in grain yields at the end of the growing season. Zn sulfate and Zn chelate are the most widely used compounds. This thesis reports the results of a field study to compare the effectiveness of the two compounds when the spray was applied at two growth stages of wheat (Gs14; seedling growth and Gs24; tillering). In addition, Zn applied with the seed while sowing the wheat crop was also included. Zinc applied to the soil while sowing was the most effective treatment. Zn chelate was more effective as a spray than Zn sulfate when applied at the earlier growth stage, but Zn sulfate was cheaper, and both sprays were equally effective when applied at the later growth stage.
Recently in the region, durum wheat (T. durum L.), narrow-leafed lupin (Lupinus angustifolius L.), yellow lupin (L. luteus L.), white lupin (L. albus L.), canola (Brassica napus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.) and lentil (Lens culinaris Medik) were all increasingly grown in rotation with spring wheat. Consequently, the Zn requirement of the new crops was compared with the Zn requirements of spring wheat. Species requiring less Zn than spring wheat to produce the same relative yield were faba bean, chickpea, albus lupin and canola; species requiring more Zn were lentil and durum wheat.
Spreadsheet models were developed to determine when re-application of fertiliser Zn was required for low and high production systems. Relative to freshly-applied Zn, the rate of decline in the RV of Zn applied in a previous year varied depending on the amount of Zn applied, time the Zn was in contact with soil since application, properties of the soil (soil pH, % clay, % organic carbon, % free calcium carbonate), plant species, and the amount of Zn removed in harvested grain or hay.
The thesis has culminated in a better understanding of Zn in the agricultural production systems of WA. The distribution and correction of Zn deficiency is now predictable for the many soil types and cropping systems of WA. Accurate identification of Zn deficiency for a range of crop and pasture species by plant analyses, typically the youngest mature leaf, is now possible for local conditions. With the calibration of the DTPA Zn soil test for soils of WA, particularly for wheat the major crop species grown in WA, prognosis of potential Zn deficiency can now be predicted before the appearance of Zn deficiency or loss in plant production.
7
Franklin, Oskar. "Plant and forest dynamics in response to nitrogen availability /." Uppsala : Swedish University of Agricultural Sciences, 2003. http://diss-epsilon.slu.se/archive/00000345/.
Full textAbstract:
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003.<br>Appendix consists of reprints of three papers and a manuscript, three of which are co-authored with others. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix.
8
Wan, Hon Chi Judy. "Interaction of earthworms and microorganisms on nutrient availability and crop growth." HKBU Institutional Repository, 2004. http://repository.hkbu.edu.hk/etd_ra/588.
Full text
9
Kvarnström, Elisabeth. "Plant-availability of phosphorus removed from wastewater by different processes /." Luleå, 2001. http://epubl.luth.se/1402-1544/2001/18/index.html.
Full text
10
Erickson, Heather E. "Nitrogen and phosphorus availability, ecosystem processes and plant community dynamics in boreal wetland meadows /." Thesis, Connect to this title online; UW restricted, 1994. http://hdl.handle.net/1773/5590.
Full text
11
Rosas, Torrent Teresa. "Integrating plant hydraulics into functional traits framework to understand plant adjustments along a water availability gradient." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667361.
Full textAbstract:
Una de les principals contribucions com ecòlegs forestals al segle XXI és proporcionar la teoria i aproximacions ecològiques per descriure i predir canvis dels ecosistemes forestals causats pel canvi global. En l'última dècada, l’ecologia basada en els trets funcionals ha sorgit com a una nova disciplina capaç de transformar l'ecologia en una disciplina més mecanicista i predictiva, i no només merament descriptiva. Tanmateix, algunes de les seves assumpcions fundacionals no s’han testat rigorosament. S’assumeix que els trets mesurats a nivell d’òrgan es poden escalar fàcilment a nivell de tota la planta, que la variabilitat intraespecífica dels trets (ITV) es pot ignorar en gran mesura i que els trets afecten les taxes demogràfiques dels individus i, per tant, són funcionals. A més, la majoria d’aproximacions estudien trets relativament fàcils i ràpids de mesurar per a un gran nombre de mostres, tot i que no estan directament relacionats amb mecanismes fisiològics específics. En aquesta tesis, mostrem que els trets hidràulics de les plantes poden ser de gran utilitat a l'hora d'entendre les principals estratègies ecològiques de les plantes. El transport d'aigua de les plantes afecta tant la seva taxa fotosintètica com el seu creixement. La hidràulica de les plantes permet incorporar l’aigua en l'economia del carboni i els nutrients, i determina la resistència de les plantes a la sequera esdevenint un factor clau a l’hora d’avaluar la vulnerabilitat dels boscos al canvi climàtic.
L'objectiu principal d'aquesta tesi és integrar els trets hidràulics en el marc dels trets funcionals clàssics, i determinar-ne la variabilitat, relacions i compromisos a diferents escales, així com usar aquesta informació per definir estratègies de les plantes per fer front a la sequera. Per tal d’aconseguir aquest objectiu, es van seguir dues aproximacions diferents: una basada en la compilació d’un conjunt de dades global de 1149 espècies d’arreu del món (Capítol 2); i una altra basada en dades de trets foliars, del tronc i hidràulics mesurats al llarg d'un gradient de disponibilitat d'aigua, en sis de les espècies arbòries dominants a Catalunya (NE Espanya) (Capítol 3 i Capítol 4). Concretament, al Capítol 2 es testa un nou marc conceptual que relaciona els trets hidràulics amb els trets més clàssics a nivell global. En el Capítol 3 s’investiguen els ajustos i la coordinació dels trets hidràulics, foliars i del tronc al llarg d’un gradient de disponibilitat d'aigua a nivell interespecífic i intraespecífic. Finalment, al Capítol 4 s’avalua la importància funcional dels trets estudiats en el capítol anterior, explorant-ne les relacions amb el creixement dels arbres a nivell interespecífic i intraespecífic.
Un resultat rellevant d'aquesta tesi és que no hem trobat evidències que donin suport a l’existència d’un espectre econòmic global de tota la planta que n’integri els diferents òrgans i recursos (carboni, nutrients i aigua). D'aquesta manera, escalar els trets mesurats a nivell d’òrgan a trets de tota la planta i estratègies en l’ús de recursos, pot ser més difícil del que es sol preveure degut a les respostes compensatòries que es donen dins d’un mateix individu. També mostrem que la ITV és especialment rellevant en trets integradors que involucren més d’un òrgan i que incorporar la ITV és un pas necessari per millorar la nostra comprensió dels ajustos de les plantes als canvis ambientals. Finalment, il·lustrem que la nostra comprensió de les relacions entre el creixement i els trets pot millorar considerablement mitjançant la selecció de trets estretament relacionats amb funcions fisiològiques i factors ambientals específics del context d’estudi, integrant els trets al llarg d’eixos comuns de variació, i reavaluant les variables que s’utilitzen per reflectir el funcionament de la planta.<br>One of the main contributions of forest ecologists, in the 21st century, is to provide ecological theory and tools to describe and predict forests ecosystem changes caused by the ongoing global change. Over the last decade, ‘functional trait-based ecology’ has emerged as a refreshed discipline with the promise to turn ecology from a primarily descriptive science into a more mechanistic and predictive discipline. However, several foundational assumptions of trait-based ecology have not been rigorously tested. It is presumed that organ-level traits can be easily scaled-up to whole-plant traits, that intraspecific trait variability (ITV) can be largely overlooked and that traits affect individual demographic outcomes and thus, are functional. Additionally, most trait-based approaches study ‘soft’ traits which are relatively easy and quick to measure for a large number of samples although they are not directly linked to specific physiological mechanisms. We argue that plant hydraulic traits can provide useful insights to the understanding of plant ecological strategies. Water transport throughout the plant affects both photosynthetic rate and growth. Plant hydraulics allow linking water to the carbon/nutrient economics and determine plants’ drought resistance and thus, are key factors when assessing forest vulnerability to climate change.
The main aim of this thesis is to integrate plant hydraulics into a functional trait-based framework, to assess trait variability, relationships and trade-offs at different ecological scales and to use this information to define strategies to cope with drought stress. To achieve this objective, two different study approaches were followed: one based on compiling a global dataset for 1149 species worldwide (Chapter 2), and another based on field data collection of a set of leaf, stem and hydraulic traits along a water availability gradient for six of the dominant tree species in Catalonia (NE Spain) (Chapter 3 and Chapter 4). Specifically, in Chapter 2 we test a new framework relating hydraulic and more ‘standard’ traits across species at the global scale. In Chapter 3 we investigate the adjustments and coordination of hydraulic, leaf and stem traits along a water availability gradient at the interspecific and intraspecific levels. Finally, in Chapter 4 we test the functional importance of traits studied in the previous chapter, exploring the strength of the association between traits and tree growth also at the interspecific and intraspecific levels.
A significant finding to emerge from this thesis is that we do not find support for a world-wide ‘fast-slow’ plant economics spectrum that integrates across organs and resources (carbon, nutrients and water). Thus, scaling-up from organ level traits to whole-plant traits and resource use strategies may be more challenging than commonly anticipated because of compensatory responses within individuals. We also show that the ITV is especially relevant for integrative traits that involve more than one organ and that accounting for ITV is a necessary step forward towards improving our understanding of plant adjustments to environmental changes. Finally, we also show that our understanding of trait-growth (and by extension trait-performance) relationships can be greatly improved by selecting traits closely related to physiological functions and context-specific environmental drivers, integrating them along common axes of variation, and re-assessing the variables that are used to reflect whole-tree performance
12
Eskelinen, A. (Anu). "Plant community dynamics in tundra: propagule availability, biotic and environmental control." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514293139.
Full textAbstract:
Abstract
Plant community composition and diversity are determined by the balance between rates of immigration and extinction. Processes of immigration to a local community, i.e. propagule availability and dispersal of propagules between and within habitats, set the upper limit for the pool of species potentially capable of coexisting in a community, while local biotic interactions, i.e., competition, facilitation, herbivory and interactions with below-ground ecosystem components, and environmental factors control colonisation and establishment, and determine the persistence and dynamics of already existing species.
In this thesis, I studied (1) the interactions between propagule availability, biotic and environmental constraints on colonisation, and (2) the interdependence between biotic and environmental factors regulating community processes in already established resident vegetation. First, I found that both propagule availability and competition with adult plants limited the rates of colonisation and total community diversity in a relatively low-productive tundra ecosystem. Long-term exclusion of mammalian herbivores and alleviation of nutrient limitation by fertilization increased the intensity of competition with established vegetation, and diminished immigration rates. In addition, I also found that community openness to colonization depended on the initial community properties, i.e., the functional composition and the traits of dominant plants in resident vegetation, which mediate the effects of nutrient addition and biomass removal on immigration rates. Second, adult plants in the resident vegetation experienced an increased extent of neighbourhood competition and herbivory in nutrient enriched conditions and in naturally more fertile habitats. However, the effects were also species-specific. On a community level, release from heavy grazing favoured lichens over graminoids and increased species richness. Furthermore, I also showed that plant community composition was strongly linked with soil organic matter quality and microbial community composition, and that these vegetation-soil-microbe interactions varied along a gradient of soil pH.
Overall, my results emphasise that propagule availability, biotic and environmental control over community processes are strongly interconnected in tundra ecosystems. Especially, my findings highlight the role of plant competition and herbivory and their dependence on soil nutrient availability in governing colonisation and resident community dynamics. My results also indicate that plant functional composition and traits of dominant plants are of great importance in channelling community responses to external alterations and dictating plant-soil interactions.
13
Neilsen, Denise. "Characterization and plant availability of zinc in British Columbia orchard soils." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72835.
Full text
14
Hanafi, M. M. "Dissolution and plant availability of phosphate rock in acid Malaysian soils." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386725.
Full text
15
Bilbrough, Carol J. "Growth Responses of Great Basin Plant Species to Variation in Nitrogen Availability." DigitalCommons@USU, 1996. https://digitalcommons.usu.edu/etd/6520.
Full textAbstract:
For this dissertation, I examined the ability of field-grown plants to capture N presented in enriched patches or in whole-plant pulses. I assessed root proliferation in N-enriched patches when Agropyron desertorum plants had been previously fertilized or shaded. All plants responded with increased root growth rates in N-enriched patches. However, root proliferation by shaded plants was 50% less than unshaded plants. Unexpectedly, plants with higher N status had greater root growth rates in enriched patches than plants that had not received N supplement. I concluded that plants already under competitive pressure above ground for light and below ground for nutrients should be less able to respond to opportunities presented in nutrient patches.
I then examined plant growth responses and biomass production of six Great Basin species (Bromus tectorum, Taeniatherum medusae, Agropyron desertorum, Pseudoroegneria spicata, Artemisia tridentata, and Chrysothamnus nauseosus) following a pulse ofN applied in the early, mid, or late spring. An equal quantity of N, applied continuously, was a control. Surprisingly, most of the species grown under the continuous supply had lower growth rates and less biomass production than plants recieving an N pulse. The exception was Chrysothamnus, which responded equivalently to all treatments. Generally, the greatest response occurred in early phenological stages. Four of the six species had their greatest response to the early-spring pulse, suggesting that these cold-season species are well-adapted to take advantage of early spring nutrient pulses. This study demonstrated that instead of benefitting from a season-long supply of N, there were times during the growing season when plants were able to use pulses of N for significant gains in biomass. I also investigated the root properties (root biomass, specific root length [the ratio of root length:root mass], and root uptake capacity) that determined plant response to pulses. Despite considerable temperature differences and changes in plant phenological stages, root uptake capacity remained remarkably constant throughout the season. However, this consistency did not explain the differences in productivity during the season. Root biomass also did not explain these growth responses to pulses. Instead, I suggest that the quantity of actively growing fine roots, plus the ability to effectively exploit the soil volume in the early spring, results in capture of early nutrient pulses.
16
Talbot, Victoria. "The chemical forms and plant availability of copper in composting organic wastes." Thesis, University of Wolverhampton, 2007. http://hdl.handle.net/2436/20493.
Full textAbstract:
A seven-step sequential extraction scheme was used to track changes in operationally defined copper speciation during the composting of a mixture of grass clippings and sawdust originating from tanalised timber. Starting materials were either unamended or treated with differing amounts of soluble copper, using a copper acetate solution, and then composted in the laboratory. Results showed that at the start of the experiment over 80% of the copper present in the unamended materials occurred in forms not immediately available for plant uptake. However, composting processes enabled the release of this copper which then, over time, became more bioavailable. Large amounts of copper in the copper amended materials were initially detectable in all fractions except the residual one, but over time it was seen to move from all fractions to the EDTA extractable fraction, thought to determine organically complexed / chelatable metals (Amir, 2005). This continued until an equilibrium was reached and then the water and calcium nitrate extractable forms appeared to hold the excess. Copper as determined by these extracts would be available for plant uptake. In the second experiment, three different organic wastes (grass/sawdust, pig slurry/sawdust and sewage sludge cake/sawdust) to which copper had been added as copper acetate, sulphate or EDTA, were composted in the laboratory. Samples were taken at 0, 105 and 318 days and subjected to a range of analyses: copper by sequential extraction using two different extraction schemes, a chelating resin membrane (CRM) procedure and by XRF spectrometry; FTIR analysis for functional groups; total carbon, nitrogen and sulphur; pH, EC, NH4+ and NO3- nitrogen, COD, germination indices and optical properties of water extracts. Sequential extractions demonstrated clear changes in copper distribution amongst various fractions within the materials, with copper originally present in the materials being transferred from the oxidisable fractions to easily extractable (and hence potentially phytoavailable) fractions. Transfer of copper from available to less available fractions in copper amended materials was also seen with movement of copper within copper EDTA treated materials being the slowest of all. Initial amounts of copper in fraction 1 extracted from all samples determined the rate at which copper was transformed. CRM determined copper correlated strongly with copper from fraction 1 of the Tessier scheme, although changes over time did not correspond well. Other parameters measured indicated that that the material was maturing (decreases in C/N and polysaccharide functional groups). However, other results demonstrated that the composts were still immature and unstable. Such slow decomposition was attributed to the high lignin content of the materials. Nevertheless, immobilisation of potentially phytotoxic level of copper was still demonstrated. The usefulness of chelating resin membrane as a predictor of phytoavailable copper is also discussed.
17
Wright, Hannah. "Soil drying and re-wetting effects on phosphorus availability and plant yields." Thesis, Lancaster University, 2018. http://eprints.lancs.ac.uk/126966/.
Full textAbstract:
Water and phosphorus (P) are essential resources for crop production, yet both are increasingly limited, threatening global food security. Soil drying and re-wetting (DRW) has reportedly increased P availability in numerous soils, whilst intermittent irrigation that applies less water than conventional full irrigation can maintain crop yields. To test the hypothesis that DRW could release P at soil water potentials (SWPs) that can support plant growth, thereby increasing crop P use efficiency and yields, experiments at different scales aimed to evaluate P release and plant uptake. Laboratory studies using three low-P UK soils determined that available P (sodium bicarbonate extractable P) significantly increased (by 4-7 mg kg-1) as SWP decreased (to a minimum of -212 MPa). A significant change point (releasing 2 mg P kg-1) occurred at -2.9 MPa. A pot study showed that surface soil drying to this change point did not increase P availability over one or two DRW cycles, suggesting laboratory results could not be scaled up spatially and temporally. Initially air-drying (to -38 MPa) and re-wetting soil prior to planting Brachypodium distachyon in pots significantly increased available P at transplanting (by 1 mg kg-1) and doubled grain yields independent of P fertiliser application. In a field trial in central Madagascar in low-P, highly P-fixing soil, applying alternate wetting and drying (AWD) or post-anthesis soil drying to Oryza sativa hardly altered P uptake or yields. Thus, DRW increased P availability and yields in pots, but plants did not benefit during a cropping cycle in the field. Applying P fertiliser (10 or 25 kg ha-1) had a greater effect than AWD, with optimal harvest index (HI) and P use efficiency (PUE) at the intermediate rate. Further research to determine locally-relevant management techniques, stimulating P release at appropriate spatial and temporal scales to allow plant uptake, is urgently required.
18
Guignard, Maite Stephanie. "Ecological consequences of angiosperm genome size and macronutrient availability." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/24632.
Full textAbstract:
Genome size (GS) is a fundamental trait influencing cellular, developmental and ecological parameters, and varies c. 2400- fold in angiosperms. This astonishing range has the potential to influence a plant's nutrient demands, since nucleic acids are amongst the most phosphate and nitrogen demanding cellular biomolecules, and hence its ability to grow and compete in environments where macronutrients are limited. Angiosperm GS are strongly skewed towards small genomes, despite the prevalence of polyploidy in the ancestry of most if not all angiosperm lineages. This thesis examines the hypothesis that large genome sizes are costly to build and maintain and that angiosperm species with large GS are constrained by nitrogen and phosphate limitation. It untangles the interactions between GS, polyploidy and competition in plant communities, and examines how herbivory and GS play a role in plant productivity, measured as above-ground biomass. The hypothesis that large GS are costly was approached by analysing: 1) plant communities growing under different macronutrient conditions at the Park Grass Experiment (Rothamsted, UK); 2) plant communities under different conditions of macronutrient limitation and insect, mollusc, and rabbit herbivory at Nash's Field in Silwood Park (UK); and, 3) Ellenberg's indicator values which represent the realised niche of a species in terms light, water, and soil fertility. Support for the hypothesis was found in all experiments. The range of analyses show that angiosperm plants with large genomes (e.g. 1C-value > 5 pg) are indeed under greater macronutrient limitation in comparison to plants with small genomes, and that it is polyploid plants with large GS which are the most competitive when macronutrient resources are plentiful. In terms of herbivory, the key finding is a highly significant negative association between GS and rabbit herbivory. A species' realised niche for soil fertility was found to show a positive association with its GS. Overall the thesis shows that angiosperm GS plays a central role in plant community composition and responses to macronutrient conditions, and potentially on higher ecosystem processes through associations at different trophic levels.
19
Du, Junrong. "Evaluation of equipment reliability, availability and maintainability in an oil sands processing plant." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/7527.
Full textAbstract:
The oil sands industry is a developing sector of Canada’s economy; one area of focus for
oil sands companies is to improve plant maintenance and overall plant availability.
Although considerable progress has been made in the improvement of plant maintenance
in other industries, oil sands and mining companies in general do not significantly benefit
from this due to variable feed supply that impacts plant performance. As well historically
for mining maintenance has not been done well.
The work presented in this thesis develops a framework for understanding oil sands
processing plant key equipment failures by utilizing data collected over two years at
Albian Sands Energy Inc, an operator of an oil sands mine in Alberta, Canada. The data
is used to calculate mean time between maintenance for key pieces of oils sand
processing equipment. As well various statistical techniques are applied to the data to
identify the best maintenance strategies for the site. Finally the efficacy of advanced
statistical techniques, such as Power Law modeling, for predicting time to next failure for
equipment is demonstrated.
20
Dissanayake, D. M. A. P. "Plant and soil factors influencing the availability of phosphorus from natural phosphate sources." Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU065665.
Full textAbstract:
Plant, soil and fertiliser factors that affect P availability from directly applied sparingly soluble rock phosphates were evaluated. The quality and the homogeneity in relation to both mineralogical and chemical composition greatly influenced the dissolution of rock phosphates. Temperate and tropical soils were used to assess the effect of pH, P and Ca status on rock phosphate dissolution. Rock phosphate fertilisers behaved differently under temperate and tropical conditions. In low pH soil, rock phosphates dissolved to a greater extent. However, soil factors were interrelated to fertiliser and plant factors. This created a complicated situation in rock phosphate availability. Effective utilisation of rock phosphates by plant species and cultivars of the same species was evaluated using monocotyledons, dicotyledons, fast growing species and slow growing perennials. Plant demand for P, Ca and their nutrient uptake pattern governed the availability of rock phosphate in the soil. Utilisation of rock phosphate was greatly dependent upon the initial P status. Plants were unable to use the added rock phosphate when they meet their P requirements effectively from the P already present in the soil. Plants which absorb more cations and hence acidify the soil, enhanced the rock phosphate dissolution. Removal of soil Ca by plant uptake positively related to rock phosphate utilisation. In order to assess the phosphorus availability in soils a relatively novel bioassay was evaluated. Irrespective of the species the method was able to indicate both plant P demand and P supply of the soil. The method was successfully used under conditions of low phosphate supply. It was compared with more widely acceptable existing soil P tests. Correlations existed with resin P methods. Potential use of the method for field situation is discussed and suggestions are made for future studies.
21
Koyama, Lina. "Soil Nitrogen Availability as a Controlling Factor of Plant Nitrogen Use and Distribution." Kyoto University, 2003. http://hdl.handle.net/2433/149533.
Full textAbstract:
Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第9866号<br>農博第1303号<br>新制||農||862(附属図書館)<br>学位論文||H15||N3741(農学部図書室)<br>UT51-2003-C634<br>京都大学大学院農学研究科地域環境科学専攻<br>(主査)教授 武田 博清, 教授 東 順一, 教授 谷 誠<br>学位規則第4条第1項該当
22
Grün, Astrid. "Impact of phosphate availability and nutritional status on the wheat transcriptome." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28960/.
Full textAbstract:
Economic, political and environmental factors have prioritized the need for research on phosphate (Pi) acquisition efficiency (PAE), Pi use efficiency (PUE) and Pi fertilizer uptake efficiency in crops. However, the coordination of molecular responses to Pi starvation and the mechanisms of Pi starvation tolerance have been investigated predominantly in model plants but remain elusive in grain crops, especially in wheat. This project investigates transcriptional profiles in wheat, particularly in the roots, as a response to nutrient availability focusing on phosphate (Pi). Furthermore, appropriate screening approaches and the difficulties in crop improvement, particularly for wheat, are discussed. Pi acquisition by plants is mediated by members of Pi transporter families. The roles of these Pi transporters in Pi partitioning and re-translocation is complex and the knowledge about their functioning in wheat still limited. Here, members of the Pht1 family in wheat were identified, their expression profiles determined when exposed to different nutrient regimes in roots and ear tissues at various developmental stages and their potential role as targets for genetic improvement discussed. In addition to Pi transporters, regulatory genes including transcription factors, signalling pathways and apparently other Pi-responsive genes with unknown function are also of critical importance. Therefore, the genome-wide responses to limited nutrient availability were investigated for the first time in roots of field-grown wheat exposed to limited nutrient availability resulting in the identification of several candidate genes for PAE/PUE improvement on the molecular level. These data were validated against other studies and across a wider wheat germplasm. Furthermore, the correlation of candidate gene expression to the nutritional status, Pi availability and PAE/PUE properties revealed four potential target genes which may be major contributors to genotypic diversity of this trait. However, there are still some agronomic bottlenecks which impede implementing Pi efficient crops and the application of molecular tools and marker genes.
23
Karlinski, Melissa. "Seedling xylem anatomy of two Banksia species relative to availability of groundwater." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2019. https://ro.ecu.edu.au/theses/2217.
Full textAbstract:
Fluctuating environmental conditions place plants at risk of mortality if they cannot adapt, particularly to warmer temperatures and drier environments. Plants are known to modify their morphology, physiology and anatomy to thrive under these conditions, and xylem anatomy and hydraulic architecture are common traits studied to understand plant adaptations and responses to changeable water availability. However, little is known about the changes to the hydraulic architecture of groundwater dependent plants during their early establishment in water-limited environments. By exposing young seedlings of two Banksia species to contrasting groundwater availability treatments in a glasshouse experiment, it was possible to analyse the xylem vessel traits (vessel diameter (Vd), maximum vessel diameter (Dmax), vessel density (Dv) and vessel length (VL)) in root and stem tissue samples using ImageJ software. Analysis of vessel traits identified significant vascular tapering in both Banksia attenuata and B. littoralis, i.e. a low density of large diameter vessels found in roots, and a higher density of small diameter vessels found in the stem. Vessel traits of B. attenuata and B. littoralis seedlings with access to an artificial water table did not differ significantly to those with access to only unsaturated soil. This lack of significant difference was surprising as studies have shown variation in xylem anatomy of plants exposed to contrasting water availabilities, commonly referred to as the hydraulic efficiency and safety trade-off theory. However, the traits did vary between the two species, with significantly larger mean Vd and Dv in B. attenuata seedling roots, and significantly higher mean Dv in B. littoralis seedling roots. VL also differed, with B. attenuata having significantly longer vessels than B. littoralis. These differences may relate to the contrasting habitat requirements of the chosen species. B. attenuata occurs across varying gradients in depth to groundwater, while B. littoralis is found in low-lying swampy areas. This could suggest that B. attenuata may be more ‘flexible’ in its xylem development, whereas B. littoralis develops a more rigid anatomy, affording protection in case of disconnection from groundwater. The findings from this study provide a better insight into how the xylem anatomy of groundwater-dependent species varies in relation to groundwater availability, and how and why species of the same genus may develop significantly different vessel traits.
24
Simmons, Jason. "Influence of Poultry Litter on Dark Tobacco Growth and Soil Nutrient Availability." TopSCHOLAR®, 2004. http://digitalcommons.wku.edu/theses/516.
Full textAbstract:
Due to the relatively high value of dark tobacco compared with fertilizer costs, nitrogen is recommended at levels as high as 338 kg ha"1. Such rates of inorganic fertilizers increase the osmotic pressure of the soil solution and soil acidity, often causing reduced stands, Mn toxicity, Mo and Ca deficiencies, and reduced yield and quality of the cured leaf (Sims et al., 1984). Poultry litter utilized as a nutrient source is an inexpensive alternative to this dilemma due to its relatively neutral or alkaline composition. However, due the amount of chloride present in poultry litter, the University of Kentucky advises that application be limited to a maximum of 9 Mg ha"1 (Wells, 1996). Environmental concerns such as nitrate contamination of groundwater, P runoff into surface water, and accumulation of heavy metals in the soil are often related to excessive application of poultry litter. Studies were conducted at Western Kentucky University's Agricultural Research and Education Complex in Bowling Green, Kentucky and a farm in Owensboro, Kentucky to evaluate the influence of poultry litter on dark tobacco growth and soil nutrient concentrations. Results from these studies indicate that when applied at recommended rates, poultry litter in most cases can alleviate soil acidification often associated with the use of inorganic fertilizer sources. In general, poultry litter amendments increased soil pH, while inorganic fertilizers had the opposite effect. Data from the Rate Study suggests that rate of inorganic fertilizer and soil pH are negatively correlated. Due to the high nutrient content of poultry litter, its utilization could possibly lead to an accumulation of P2O5 and certain heavy metals, such as Cu and Zn. Data from the Bowling Green Timing Study indicated that poultry litter amendments increased postharvest soil P availability compared to inorganic fertilizer amendments. At the Owensboro location there were no differences in soil P availability among treatments. Results from the Rate Study suggest that soil P availability and poultry litter rate were positively correlated. Data from all studies indicate that in some cases, soil Cu availability was greater in poultry litter treated plots than in plots treated with inorganic fertilizers. With one exception, plots receiving poultry litter were higher in soil Zn availability than inorganic fertilizer plots at the Bowling Green Timing Study. Data from the Rate Study suggests that increasing the poultry litter rate increased soil Zn availability in poultry litter plots receiving a sidedress application. Data from the Owensboro Timing Study indicated that regardless of application timing, cured lamina tissue chloride concentration in poultry litter amended plots were greater than the tobacco industry standard of 1%. Chloride concentrations in the lamina and stem were higher in plots receiving poultry litter than plots treated with inorganic fertilizers. Despite these concentrations there were no noticeable differences in curing and USDA quality rating. Data from the Timing Studies indicated that total yields were equivalent in poultry litter and inorganic fertilizer treated plots, however yields of certain grades did vary. Plots receiving a source of fertilizer had higher total yields than the untreated control. Results from the Rate Study showed that total yields were quite variable, which may be attributed to poor water drainage from the study area. In the Rate Study, a general trend emerged in which increasing the rate of poultry litter in combination with a sidedress application increased trash, lug, and total yield, but decreased tip yield.
25
Stock, Svenja [Verfasser]. "Plant nutrient mobilization and acquisition strategies: adaptation to water and nutrient availability / Svenja Stock." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2021. http://d-nb.info/1230138099/34.
Full text
26
Araya, Yoseph Negusse. "Influence of soil water regime on nitrogen availability and plant competition in wet meadows." Thesis, Open University, 2005. http://oro.open.ac.uk/54860/.
Full textAbstract:
Identified ecological drivers controlling the equilibrium of species coexistence in wet meadows include site hydrology, soil nutrient availability and grazing. Of these, depth and annual variation of the water table has been considered as a primary factor and been frequently used in management decisions. A mechanistic understanding of how water regime influences species coexistence is thus vital for guiding conservation practices. In this context, this thesis explores the involvement of nitrogen availability, an often limiting resource which may be dependent on soil water regime. Laboratory and mesocosm experiments alongside field observations were undertaken to explore the interrelationships between water regime, nitrogen availability and plant competition. Three coexisting meadow species: meadow fescue, <i>Festuca pratensis</i>, common sedge, <i>Carex nigra</i> and greater burnet, <i>Sanguisorba officinalis</i>, were used to study the consequences in plant competition. Study of soil nitrogen mineralization revealed a depression in mineralized nitrogen asmatric potential approached zero. This depression coincided with soil air-filled porespace of less than 10%. The changes in water tension were accompanied by changes in soil microbial community composition as indicated by their phospholipid fatty acid signatures. Mesocosm study of <i>F. pratensis</i> and <i>C. nigra</i> grown on a gradient of constant water regime showed Significant differences in biomass production and tissue nitrogen concentration. Individually and in competition the species responded by modifying resource allocation to reproductive/vegetative as well as shoot/root tissues. Nitrogen fertilization removed the influence of water regime on biomass production and tissue nitrogen concentration of <i>C. nigra</i> and <i>S. officinalis</i>. However, it did not significantly negate the influence of water regime on plant competitive response. Direct field observation in a species-rich meadow confirmed species richness, biomass production and tissue nitrogen concentration were correlated to both soil water regime and nitrogen availability. A multivariate ordination of all recorded species along measured gradients of soil water regime, nitrogen availability and plant tissue nutrient concentrations indicated evidence of niche separation between species.
27
Rappaport, Bruce D. "Availability and distribution of heavy metals from sewage sludge in the plant-soil continuum." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/71177.
Full textAbstract:
An investigation was conducted using in situ lysimeters (1.5 m x 2.3 m) to determine Cd, Cu, Ni, and Zn availabilities for barley (Hordeum vulgare L.) and corn (Zea mays L.) grown on four sludge-amended soils. These lysimeters were constructed in Acredale silt loam (Typic Ochraqualf), Bojac loamy sand (Typic Hapludult), Davidson clay loam (Rhodie Paleudult), and Groseclose silt loam (Typic Hapludult) soils. An aerobically digested sewage sludge from a sewage system with major industrial inputs was applied at rates of 0, 42, and 84 dry Mg ha-t to the lysimeters in the poorly-drained Acredale soil. Rates of 0, 42, 84, 126, 168, and 210 dry Mg ha-1 were applied to the lysimeters in the well-drained Bojac, Davidson, and Groseclose soils.
Tissue metal concentrations were determined in 1984 and 1985 for a three crop rotation, which consisted of corn, barley, and corn on the Acredale soil. Increases in sludge-borne Ni and Zn led to increases in Ni and Zn concentrations in corn earleaf, corn grain, and barley silage. Copper concentration was increased in barley silage but not in corn grain and stover. On this poorly-drained soil, metal movement did not occur below the Ap horizon even when Cu was applied in excess of USEPA guidelines. Although there were increases in metal levels, all four metals were within the range considered normal for corn and barley growth.
Soil, corn, and barley plants were sampled in 1984 and 1985 to determine Cd, Cr, Cu, Ni, and Zn availabilities for crops grown on the sludge-amended Bojac, Davidson, and Groseclose soils. Levels of DTPA-extractable Cd, Cu, Ni, and Zn in the Ap horizon of these soils increased linearly with sludge rate. Corn grain and stover yields were not decreased on the Bojac, Davidson, and Groseclose soils when 4.5, 5105, 760, 43.0, 135, and 620 kg ha-1 of Cd, Cr, Cu, Ni, Pb, and Zn were added as a sludge-amendment. Copper and Zn applied in excess of 480 and 60 kg ha- 1 of USEPA guidelines, respectively on the Bojac, Davidson, and Groseclose soils were not phytotoxic to corn plants in 1984. Corn and barley tissue sampled for three consecutive seasons had Cr concentrations <2.8 mg kg-1.<br>Ph. D.
28
Piippo, S. (Sari). "Grazing tolerance of biennial meadow plants in relation to resource availability." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514262111.
Full textAbstract:
Abstract
In this thesis I studied responses of three biennial, monocarpic plants Erysimum strictum, Gentianella amarella, and G. campestris, to various aspects in resource availability (i.e. competition, mineral nutrition, neighbor removal) and environmental stress (early frost) at adult or rosette stages and how these effects are related to grazing tolerance. I also studied how manipulations in resource availability affected arbuscular mycorrhizal colonization of the roots.
All three species were relatively tolerant to simulated grazing and in most cases plants were able to compensate quite well for minor biomass losses. According to the compensatory continuum hypothesis, tolerance is most pronounced in resource-rich conditions, but this was not always the case in the present experiments. Erysimum strictum compensated for defoliation at the rosette stage but the reproductive output of adult plants was reduced markedly in the next year. This reduction was strongest among fertilized plants. Moreover, apex removal at the adult stage resulted in overcompensation (i.e. clipped plants were more productive) but only in the absence of fertilization and in the presence of competition, which is against the compensatory continuum hypothesis. In E. strictum a potential cost of compensation appeared as delayed flowering and fruit maturation among clipped plants. However, in spite of early frost treatment clipped plants were still able to overcompensate. In Gentianella amarella and G. campestris, apex removal reduced growth and reproductive performance in most cases. Effects on root fungal parameters were positive or neutral. This pattern suggests that simulated above-ground herbivory tends to increase carbon limitation, and therefore regrowing shoots and the fungal symbionts may appear as alternative, competing sinks for the limited carbon reserves of the host plant.
Both shoot architecture and resource availability modify the responses of the study plants to apical damage at both rosette and adult stages. In addition, different environmental stress factors affect success in compensatory growth.
29
Tariq, Mohammad. "Effect of boron supply on the availability of nutrients in soil and uptake by radish (Raphanus sativus L.)." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363708.
Full text
30
Kakkar, Avneet. "Nitrogen Availability and Use Efficiency in Corn Treated with Contrasting Nitrogen Sources." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6886.
Full textAbstract:
The plant-soil nitrogen cycle plays a significant role in allocation of available N to plants, and improved understanding of N cycling helps sustainably increase fertilizer use efficiency. There are various processes (nitrogen mineralization and nitrification) involved in the availability and mobility of nitrogen in the soil. The primary objective of this study was to determine the NUE under contrasting nitrogen treatments over a period of five years. Additionally, we examined the effect of different N treatments on N mineralization and nitrification in conventional and organic farming systems.
This project was funded by Agriculture and Food Research Initiative Competitive Grants Program Grant no. 2011-67019-30178 from the USDA National Institute of Food and Agriculture and by the Utah Agricultural Experiment Station. We established silage corn field plots in northern Utah, and silage corn was grown using ammonium fertilizers or manure composts over five years. Nitrogen use efficiency was found to be higher in ammonium sulfate fertilizer treatments as compared to compost treated soils. Nitrogen mineralization and nitrification rates were examined for soils from the silage corn field plots and also for additional soils from certified organic field plots receiving steer compost, steer manure and crop rotations. There was a significant overall nitrogen treatment effect for both conventional and organic rotational plots. Carbon mineralization rates were found to be higher in compost under conventional plots and manure under organic rotational plots as compared to control. There was no significant treatment effect found in gross mineralization and nitrification rates in 2015 and 2016. Gross nitrification rates were found to be the higher in AS200 treatment versus compost and control in 2016.
Improved knowledge of the timing and rates of nitrogen supply is vital for improving NUE and for reducing excessive use of fertilizers while maintaining an acceptable yield. The optimization of fertilizer rates according to crop demand at different stages of growth will be helpful in the efficient management of available N especially for composts and manures.
31
Semon, Mande 1957. "Interplot and intraplot border effects on maize genotypes under two levels of moisture availability." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276817.
Full textAbstract:
The performance of three maize (Zea mays L.) hybrids, grown under two irrigation levels, was used to investigate the effects of soil moisture competition between adjacent plots, the transmission of these effects into multi-row adjacent plots and types of multi-row plots and plot borders most effective in shielding from these interplot competition effects. On the basis of grain yield, competition effects intended to the second rows of five-row plots necessitating more than five-row plots to accurately evaluate the full transmission of interplot competition effects into adjacent plots. Evaluation of genotypes in one-row plots all with the same common border row genotype to make them three-row plots would be more suitable for evaluation of relative competitiveness for soil moisture under soil moisture stress conditions compared to no border rows or border rows of the same genotype being evaluated.
32
Olivas, Paulo C. "Arctic Ecosystem Responses to Changes in Water Availability and Warming: Short and Long-Term Responses." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/333.
Full textAbstract:
Arctic soils store close to 14% of the global soil carbon. Most of arctic carbon is stored below ground in the permafrost. With climate warming the decomposition of the soil carbon could represent a significant positive feedback to global greenhouse warming. Recent evidence has shown that the temperature of the Arctic is already increasing, and this change is associated mostly with anthropogenic activities. Warmer soils will contribute to permafrost degradation and accelerate organic matter decay and thus increase the flux of carbon dioxide and methane into the atmosphere. Temperature and water availability are also important drivers of ecosystem performance, but effects can be complex and in opposition. Temperature and moisture changes can affect ecosystem respiration (ER) and gross primary productivity (GPP) independently; an increase in the net ecosystem exchange can be a result of either a decrease in ER or an increase in GPP. Therefore, understanding the effects of changes in ecosystem water and temperature on the carbon flux components becomes key to predicting the responses of the Arctic to climate change. The overall goal of this work was to determine the response of arctic systems to simulated climate change scenarios with simultaneous changes in temperature and moisture. A temperature and hydrological manipulation in a naturally-drained lakebed was used to assess the short-term effect of changes in water and temperature on the carbon cycle. Also, as part of International Tundra Experiment Network (ITEX), I determined the long-term effect of warming on the carbon cycle in a natural hydrological gradient established in the mid 90’s. I found that the carbon balance is highly sensitive to short-term changes in water table and warming. However, over longer time periods, hydrological and temperature changed soil biophysical properties, nutrient cycles, and other ecosystem structural and functional components that down regulated GPP and ER, especially in wet areas.
33
Aikio, S. (Sami). "Plant adaptive strategies in relation to variable resource availability, soil microbial processes and ecosystem development." Doctoral thesis, Oulun yliopisto, 2000. http://urn.fi/urn:isbn:9514256824.
Full textAbstract:
Abstract
Plants have evolved various adaptive strategies for balancing the benefits and costs of having a high affinity for resources, plasticity of growth allocation and mycorrhizal symbiosis. The relative growth rates of mycorrhizal and non-mycorrhizal plants were modelled for stable and variable nutrient availability. Mycorrhizal plants had higher growth rates at low and non-mycorrhizal plants at high nutrient availability. Variation in nutrient availability reduced the growth rate of mycorrhizal plants due to a high affinity for nutrients. However, mycorrhizal plants may be able to buffer against external fluctuations and therefore experience less environmental variation than non-mycorrhizal plants. Non-mycorrhizal plants may even benefit from variation.
The optimal allocation of growth between shoot and roots depends on the availability of energy and nutrients. The optimisation model predicted that the requirement for phenotypic plasticity of shoot/root allocation is greatest in environments with low resource availability. Plants with a high affinity for resources required more plasticity in order to tolerate variation than plants with a low affinity. The model predicted a trade-off between the ability to deplete resources and the ability to tolerate resource fluctuations.
Changes in the availability and ratio of resources lead to changes in the structure and composition of vegetation during primary succession. The field study of the forested phases of the land uplift island Hailuoto showed a successional change in the vegetation from the dominance of bryophytes and deciduous dwarf shrubs to dominance by lichens and evergreen dwarf shrubs. The humus layer became thinner and the availability of nutrients declined, while the C/N ratio of soil organic matter increased during succession indicating a decline in the quality of organic matter. The increased soil respiration rate indicates a successional increase in the energetic costs of decomposing organic matter.
Nutrients mediate both direct and indirect trophic interactions. Indirect interactions of nutrient cycling are not explicit in continuous time models. A transformation to a discrete time model was shown to make the indirect interactions explicit as transition probabilities and allowed their dynamic contribution to be evaluated with an elasticity analysis. The importance of indirect interactions was greater in tundra than temperate forest and increased with the rate of nutrient cycling.
34
Evans, Tracie Marie. "Effects of the availability of floral resources on plant-pollinator interactions and the implications for the long-term survival of plant populations." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33045.
Full textAbstract:
1. Insect pollinators have been shown to alter their foraging patterns in response to habitat and landscape composition, particularly in relation to changes in the availability of floral resources which provide essential pollen and nectar provisions. Changes to pollinator behaviour and community composition, may alter the distance, directness and frequency of pollen movement and thus, the compatibility and genetic relatedness of pollen transferred between plants. We still lack good understanding of how variation in the spatial and temporal availability of floral resources drives pollinator responses and in turn, affects the fitness of outcrossing plants. Knowledge in this area could contribute to improved management interventions to enhance pollination services for plant conservation. 2. Through a combination of habitat and landscape scale field experiments, I explored how the availability of floral resources at different spatial scales affected plant-pollinator interactions, pollen transfer and mating success in plant populations, particularly those isolated from conspecifics. This involved introducing different species of plants in experimental arrays across a range of study systems that varied in structure and floral availability. Over the course of the thesis, I measured the community composition and behaviour of pollinators visiting experimental arrays; focusing on traits considered important for pollen transfer (e.g. Inter-tegular ('IT') span). Pollen movement was quantified within and between populations (5-150m) and the resulting plant outcrossing rates were measured using different methods including paternity analysis and the use of a dominance inheritance system. In addition, the implications of variations in pollinator foraging and pollination services can be attributed to pollen and gene flow and subsequently the reproduction and fitness of plants were assessed as a means of predicting the impacts on longer-term plant survival. 3. Findings from this thesis demonstrate reductions in the activity density (the abundance of actively foraging pollinators) and richness of pollinators and thus, the potential for plant visitation in response to a high abundance of floral resources within a habitat. This led to disruptions in pollen transfer, illustrated through a lower incidence of intra and inter-population pollen movement, and ultimately, reduced plant outcrossing rates. In parallel, plant seed set and germination rates were also reduced in habitats with high resource availability. Changes to pollinator communities and pollination services varied with the spatial scale at which floral resources were measured. Pollinator communities (activity density, richness and IT span) were most affected by floral resource abundance at a local scale (1-50m), particularly within a 20m radius of a plant population. Intra-population pollen movement was similarly affected by floral resources at a local spatial scale (within a 1m radius of a plant population). In contrast, no effect was observed on pollinator communities, intra-population pollen movement or plant reproduction when floral resources were measured at a landscape scale (within a 100-1500m radius of a plant population). However, findings were variable across different experiments at the same scale of measurement. For instance, the availability of floral resources at a local scale did not always elicit an effect on plant reproduction. This reflects differences in plant species identity and the effects of breeding system and floral traits, illustrated through variations in visitation rates between plant species. Inconsistencies were further observed with pollinator activity density and richness, which were not related to floral resources at a habitat scale in one chapter. 4. This thesis highlights the importance of the availability of floral resources at a local scale on plant-pollinator interactions and pollination services to plants. Co-flowering plants within florally rich habitats compete for pollinators and subsequently, visitation and pollen transfer between individuals of low density plant populations is diluted rather than facilitated. This suggests that although pollinator abundance and diversity may be enhanced through florally rich habitats (e.g. habitats implemented under the agri-environment scheme), pollination services are not automatically improved for plants which are present at low frequency in the landscape. This needs to be considered when designing and implementing management for threatened or isolated plants where plants may instead benefit from focused interventions. For instance, pollination services may be increased by efforts to maximise the facilitative effect of surrounding habitats, while increasing the ability of threatened or isolated plants to withstand competition from co-flowering plants.
35
Jordaan, G. "Renewable energy and the availability of water in a future South Africa." Interim : Interdisciplinary Journal, Vol 13, Issue 2: Central University of Technology Free State Bloemfontein, 2013. http://hdl.handle.net/11462/306.
Full textAbstract:
Published Article<br>The world is increasingly being misused by its inhabitants by the wasteful manner that its resources are utilized and the amount of pollution that is generated in the environment. This practice is unsustainable and it is incumbent on the present generation of decision-makers to rectify this phenomenon if our descendants are to have an opportunity to live life in the same manner as we do.
Special emphasis should be placed on a reduction in the amount of air pollution that is created by electrical power generating plants, as well as the manner in which potable water is utilized and wasted.
In this article the local situation with respect to the generation and use of electrical energy and water is discussed. It is encouraging to see that the National Government is taking strong steps to address these problems. Yet, it might not have the required ability to finance these efforts fully.
36
Noronha, Sannervik Angela. "Modelling productivity of willow stands in Sweden : evaluation of concepts for radiation use efficiency and soil water and nitrogen availability /." Uppsala : Dept. of Short Rotation Forestry, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s286-ab.html.
Full text
37
Spiers, James Davis. "The effects of nutrient availability on the host plant resistance of gerbera to western flower thrips." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2525.
Full text
38
Romanyà, i. Socoró Joan. "Phosphorus cycling in fast growing forest plantations: availability, plant uptake and the role of forest floor." Doctoral thesis, Universitat de Barcelona, 1993. http://hdl.handle.net/10803/957.
Full textAbstract:
The research reported in this thesis focuses on studying the effects of naturally occurring mycorrhiza and the role of forest floor in the cycling of P in fast growing forest plantations. In order to study the effects of mycorrhizae on forest soils fertility and the subsequent seedling growth response, radiata pine (Pinus radiata D. Don) seedlings were grown in pots using the soil collected from a mature (23 year old) radiata pine plantation. The experiment was arranged in a two factor design. The treatments comprised of sterilized and unsterilized soil, either fertilized with superphosphate (100 KgP/ha) or remained non-fertilized. In an attempt to explore nutrient uptake mechanisms under contrasted soil fertility and under mycorrhizal and non-mycorrhizal conditions, Barber-Cushman nutrient uptake model was used to simulate nutrient uptake in these treatments.<br/><br/>Mycorrhiza suppressed treatments showed low mineral NO3-N concentration and high autoclave N in soil. NH,-N concentration was not affected by any treatment. Water and bicarbonate soluble reactive P (SRP) and soluble non-reactive P (NRP) were not changed by mycorrhiza. Phosphatase activity greatly decreased in mycorrhiza suppressed treatments. Despite superphosphate addition increased all forms of P, acid phosphatase activity did not change by this factor.<br/><br/>Mycorrhiza suppression decreased seedling growth but not root length or surface. Non-mycorrhizal seedlings showed a much large proportion of roots thinner than 0.5 mm diameter. While in 7 month old seedling needle development was delayed in nonmycorrhizal pots, 4 months later all needles had the same size. At this stage of growth, plant adapted to nutritional shortages by loosing needles. Except in non-mycorrhizal-unfertilized seedlings, where growth was limited by P, in the other treatments growth was N and Mg limited. Mycorrhizal associations increased the specific uptake rate (mmol cm(-1) root) for N, P, K, S, Mg, Ca and Al. While under natural P availability conditions, P uptake was largely reduced after mycorrhiza suppression, under high P availability it was hardly increased by mycorrhiza. Barber-Cushman model was able to predict the relative variations in P and Mg uptake only in non-mycorrhizal treatments. While P uptake appeared to be controlled by root surface, Mg uptake was mostly regulated by root length.<br/><br/>To study the role of the forest floor in the cycling of nutrients, nutrient leaching through litter layers was monitored in a mature radiata pine plantation (18 year old) using 20 zerotension lysimeters installed underneath the Oa horizon.<br/><br/>Both P and N concentrations in the litter leachates showed large seasonal changes. Organic P compounds were more readily retained at the forest floor than organic N compounds. A large proportion of nutrients leached throughout the year (51% and 61% of total P and N exported respectively) took place during short periods of time. Most N transferred from the forest floor to the mineral soil was in organic form. In contrast, P was mostly transferred as inorganic P (SRP). The total amount of nutrient exported to the mineral soil were of the same order of magnitude than the yearly nutrient increases in aboveground biomass. There were evidences suggesting that a major content part of this nutrient flow originated in the forest canopy.<br/><br/>Using a new proposed anion resin fractionation technique, P forms in litter leachates and soil solution were compared. This technique showed that Murphy and Riley method to determine P concentration in solution was not able to distinguish clearly between inorganic and organic P in solution. One limitation of the fractionation technique was that it was not a clean separation of organic and inorganic P forms. However, it does appear to be useful for documenting relative changes in P forms when samples are contrasted.<br/><br/>In a mixed Eucalyptus forest in SE Australia, the effect of slash burning on surface soil P forms and on sorption and desortption of P were studied. According to fire intensity, three different microsites were selected: unburnt , burnt and intensely burnt.<br/><br/>The effects of fire on soil P were greatest in the surface soil horizons and depended upon fire intensity. After fire labile inorganic P (Bray I) increased from <1 mg kg(-1) to 5-13 mg kg(-1) in the ash bed. The increase in labile organic P (NaHCO2) contrasted with a decrease in total organic P (H2SO4) and less labile organic P (NaOH) in ashbed soils. The ashbed soil showed an increase insorption capacity in the 0-5 cm layer, but the sorbed P was generally less tightly bound to the solid phase.
39
Shand, Ishbel. "The biogeochemical origins and plant-availability of potentially toxic elements in sediment from the Thames Estuary." Thesis, Cranfield University, 2005. http://hdl.handle.net/1826/998.
Full textAbstract:
In this thesis I investigate the biogeochemical origins and plant availability of potentially toxic elements (PTEs) in sediments dredged from the Thames Estuary. The sediments were pumped from the Thames into silt lagoons on the Rainham Marshes between 1961 and the late 1970s. They are fine-textured and rich in organic matter.
The results show that PTE concentrations in the sediments are strongly positively correlated with nitrogen concentrations, and are highly inter-correlated. It is known that this distribution pattern is restricted to ancient and modern sediments from near coastal environments, and hence a link with estuarine processes is suggested. Subsequent investigation showed that the dredgings came from the Thames maximum turbidity zone, and that the lagoons represent a chronological record of changes in sediment quality during a period when dissolved oxygen in the water column rapidly increased. Analysis of one 5 m core from a lagoon showed that there were concurrent substantial changes in the relative proportions of clay, silt and sand in the sediment
A novel mechanism is proposed, whereby the textural changes and PTE/organic matter correlation result from mineral dissolution and re-precipitation within flocs in the water column of the maximum turbidity zone. This is mediated by microbial consortia, and is driven by the requirement for Fe(III) as a terminal electron acceptor by dissimilatory iron-reducing bacteria. Potentially toxic elements released from mineral carrier phases are subsequently complexed by various components of the organic fraction or incorporated into secondary minerals and evenly distributed throughout the sediment by tidal action. Published data from historical, geological, hydrological and microbiological science are presented in support of this hypothesis. Foliar concentrations of PTEs in plants grown in the sediments were lower than those predicted by current models, probably because of strong sorption of these elements on sediment solids.
40
Xiao, Qiying. "PLANT RESPONSE TO MAGNESIUM AVAILABILITY: ROOT MORPHOLOGY ADAPTATION AND INVESTIGATION OF A ROLE FOR THE CLOCK." Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/252836.
Full textAbstract:
Understanding the dynamical bases of the interaction between the plant mineral nutrition and the circadian clock could contribute to improve crop yield and resistance to adverse conditions, such as mineral element deficiencies. Magnesium is an essential element that catalyzes more than six hundred enzymatic reactions and occupies the center of the chlorophyll structure in plants. Physiological targets of magnesium deficiency are generally better described in aerial than in belowground organs. In this thesis, we first characterized the root morphology of the model species Arabidopsis thaliana (Columbia-0) in response to magnesium supply during in vitro culture. The length of primary root and the number and length of lateral roots decreased during magnesium depletion. A local magnesium-rich source does not enhance the root foraging capacity, unlike some other major nutrients. Auxin and abscisic acid emerged as two hormones shaping root morphology in response to magnesium deficiency. Second, we investigated the natural variation of the root morphology response to magnesium supply in Arabidopsis. Thirty-six accessions were screened in vitro. Compared to the reference Columbia-0, some accessions had higher number and length of lateral roots at low magnesium supply. Root or shoot magnesium concentrations did not implicitly correlate with the root morphological traits. However, shoot calcium and root phosphorus concentrations correlated positively with the lateral root number and length, while root iron negatively with the length of primary root. Third, we focused on the interaction between the plant magnesium nutrition and the circadian clock circuit. We tested for a possible involvement of PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1) - a clock-associated gene that is down-regulated during magnesium depletion - in morphological and physiological responses, and for a circadian connection of PIL1 in the context of magnesium deficiency. The phenotypes of loss-of-function and overexpression lines did not reveal a major role of PIL1 in the magnesium deficiency symptom manifestation but rather in the plant mineral profile. The expression of PIL1 was apparently not under any circadian control. However, PIL1 seemed to regulate the expressions of some core clock genes (CCA1, LHY and PRR9), which were also targets during magnesium deficiency. In conclusion, PIL1 has a link with the circadian rhythm machinery but it does not emerge as a pivotal regulator of magnesium stress responses.<br>Doctorat en Sciences<br>info:eu-repo/semantics/nonPublished
41
Weigelt, Alexandra. "Plant competition on inland dunes : influence of water availability, nitrogen supply and the role belowground processes /." [S.l. : s.n.], 2001. http://www.gbv.de/dms/bs/toc/33300020X.pdf.
Full text
42
Scott, James D. "Availability and distribution of nitrogen and phosphorus from sewage sludge in the plant-soil-water continuum." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/43892.
Full textAbstract:
Research was conducted in 1984 and 1985 to determine N and P availabilities for barley (Hordeum vulgare L.) and com ( Zea mays L.) grown on four sludge-amended soils. Tests were conducted on the Acredale silt loam (Typic Ochraquall), Bojac loamy sand (Typic Hapludult), Davidson clay loam (Rhodic Paleudult), and Groseclose silt loam (Typic Hapludult) soils. An aerobically·digested sewage sludge from a sewage treatment plant with major industrial irrputs was applied at rates of 0, 42, and 84 dry Mg ha' 1 on the poorly-drained Acredale soil. Rates of 0, 42, 84, 126, 168, and 210 dry Mg ha'1 were applied on the well-drained Bojac, Davidson, and Groseclose soils. The 210 dry Mg haâ 1 sludge rate supplied 3300 and 6600 kg of N and P haâ 1, respectively. A 14-day anaerobic N incubation study indicated that mirreralization varied from approximately nine to four percent of sludge N from the 42 to 210 Mg haâ 1 application rates, respectively. Sludge application increased N uptake (rz = 0.98** to 0.99**) by the 1984 com grown on the three well-drained soils. Nitrogen balance data indicated that quantities of unrecovered N ranged from six to 21 percent where sludge was applied.<br>Master of Science
43
Jackson, Brian Eugene. "Chemical, Physical, and Biological Factors Influencing Nutrient Availability and Plant Growth in a Pine Tree Substrate." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29491.
Full textAbstract:
Pine tree substrate (PTS) produced from freshly harvested loblolly pine (Pinus taeda L.) trees has potential for replacing or reducing the use of aged pine bark (PB) and peat moss as container substrates for horticulture crop production. The objective of this work was to determine the factors influencing nutrient availability in PTS compared to PB or peat substrates. Chapter two reports data on the response of japanese holly and azalea to fertilizer rate when grown in PTS and PB. This study demonstrated that an additional 2.4 kgâ m-3 of Osmocote Plus (15N-3.9P-10K) controlled release fertilizer is required for both species when grown in PTS compared to PB. Data are reported in chapter three on the effects of fertilizer rate, substrate particle size, and peat amendment on growth and floral quality, and on post-production time-to-wilting of poinsettias. Data from this work show that PTS requires an additional 100 mgâ L-1 N to grow poinsettias comparable to plants grown in peat unless the particle size of PTS was decreased or 25% peat was added, in which case no additional fertilizer was needed. Results also indicated that PTS shrinkage was similar to that of peat, and that post-production time-to-wilting in PTS plants was similar as plants grown in peat. Data in chapter four compares nitrogen (N) immobilization rates, substrate carbon dioxide (CO2) efflux levels, and nutrient leaching in peat, PB, and PTS over time. Data from these studies indicated that more N immobilization occurs in PTS than in PB or peat and that the substrate CO2 efflux levels (estimate of microbial activity) corresponds to N immobilization in all substrates. Nutrient availability, changes in physical and chemical properties, substrate shrinkage, and microbial activity in PTS compared to PB during long-term nursery production are reported in chapter five. Results showed that substrate nutrient levels remain lower in PTS and that pH levels of PTS decrease considerably over two growing seasons compared to PB. Results also indicate that PTS does decompose over time in containers, but substrate shrinkage of PTS is similar to that of PL and PB during crop production.<br>Ph. D.
44
Brennan, Aoife. "Biochar for assisted phytomanagement of contaminated soils : short term effects on contaminant availability and plant growth." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24880.
Full textAbstract:
There has been much interest in using biochar as a low cost sorbent amendment to reduce the risk posed by contaminated sites but an understanding of biochar interactions with plants in a contaminated soil context is still in its early stages. This thesis is based on the overall hypothesis that biochar amendment would improve soil health and plant growth in addition to reducing the availability of organic and inorganic contaminants. Biochars from three different feedstocks (maize stover, olive tree pruning and pine woodchip) and coal-derived activated carbon were used in experimental studies designed to test the thesis hypothesis. Soils contaminated with copper and arsenic (Chapters 2 and 4), mercury (Chapter 3), and polycyclic aromatic hydrocarbons (Chapters 4 and 5) were used in experiments designed to investigate the different effects biochar amendment had on specific contaminant behaviour and mobility in soils. Innovative passive sampling techniques were used to monitor changes in freely dissolved concentrations of the contaminants studied. Rhizon samplers extracted porewater from soil for selected inorganic contaminant analysis while polyoxymethylene (POM) samplers were used in laboratory equilibrium tests to determine freely dissolved concentrations of organic contaminants in soil. Biochars consistently reduced plant uptake (in plant species maize and Italian ryegrass) for both organic and inorganic contaminants. Biochars had a generally beneficial effect on plant growth. Freely dissolved concentrations were reduced for inorganic contaminants copper and arsenic (with the exception of arsenic with olive tree pruning in Chapter 2). Limited to no effects on porewater concentrations were observed for mercury (Chapter 3) and organic contaminants. Activated carbon was more effective at removing organic contaminants from porewater than biochar. By defining the conditions in which sorbent amended soils successfully reduced contaminant bioavailability and improved plant growth, this thesis demonstrates how biochar may prove a valuable tool in the phytomanagement of contaminated soils.
45
Bravo, Katherine <1983>. "Organic fertilization of peach trees: implication on nitrogen availability, root growth and carbon distribution within plant." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3980/1/Bravo_Romero_Katherine_Cecilia_tesi.pdf.
Full textAbstract:
In the last years, sustainable horticulture has been increasing; however, to be successful this practice needs an efficient soil fertility management to maintain a high productivity and fruit quality standards. For this purpose composted organic materials from agri-food industry and municipal solid waste has been used as a source to replace chemical fertilizers and increase soil organic matter. To better understand the influence of compost application on soil fertility and plant growth, we carried out a study comparing organic and mineral nitrogen (N) fertilization in micro propagated plants, potted trees and commercial peach orchard with these aims: 1. evaluation of tree development, CO2 fixation and carbon partition to the different organs of two-years-old potted peach trees. 2. Determination of soil N concentration and nitrate-N effect on plant growth and root oxidative stress of micro propagated plant after increasing rates of N applications. 3. Assessment of soil chemical and biological fertility, tree growth and yield and fruit quality in a commercial orchard. The addition of compost at high rate was effective in increasing CO2 fixation, promoting root growth, shoot and fruit biomass. Furthermore, organic fertilizers influenced C partitioning, favoring C accumulation in roots, wood and fruits. The higher CO2 fixation was the result of a larger tree leaf area, rather than an increase in leaf photosynthetic efficiency, showing a stimulation of plant growth by application of compost. High concentrations of compost increased total soil N concentration, but were not effective in increasing nitrate-N soil concentration; in contrast mineral-N applications increased linearly soil nitrate-N, even at the lowest rate tested. Soil nitrate-N concentration influenced positively plant growth at low rate (60- 80 mg kg-1), whereas at high concentrations showed negative effects. In this trial, the decrease of root growth, as a response to excessive nitrate-N soil concentration, was not anticipated by root oxidative stress. Continuous annual applications of compost for 10 years enhanced soil organic matter content and total soil N concentration. Additionally, high rate of compost application (10 t ha-1 year-1) enhanced microbial biomass. On the other hand, different fertilizers management did not modify tree yield, but influenced fruit size and precocity index. The present data support the idea that organic fertilizers can be used successfully as a substitute of mineral fertilizers in fruit tree nutrient management, since they promote an increase of soil chemical and biological fertility, prevent excessive nitrate-N soil concentration, promote plant growth and potentially C sequestration into the soil.
46
Bravo, Katherine <1983>. "Organic fertilization of peach trees: implication on nitrogen availability, root growth and carbon distribution within plant." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3980/.
Full textAbstract:
In the last years, sustainable horticulture has been increasing; however, to be successful this practice needs an efficient soil fertility management to maintain a high productivity and fruit quality standards. For this purpose composted organic materials from agri-food industry and municipal solid waste has been used as a source to replace chemical fertilizers and increase soil organic matter. To better understand the influence of compost application on soil fertility and plant growth, we carried out a study comparing organic and mineral nitrogen (N) fertilization in micro propagated plants, potted trees and commercial peach orchard with these aims: 1. evaluation of tree development, CO2 fixation and carbon partition to the different organs of two-years-old potted peach trees. 2. Determination of soil N concentration and nitrate-N effect on plant growth and root oxidative stress of micro propagated plant after increasing rates of N applications. 3. Assessment of soil chemical and biological fertility, tree growth and yield and fruit quality in a commercial orchard. The addition of compost at high rate was effective in increasing CO2 fixation, promoting root growth, shoot and fruit biomass. Furthermore, organic fertilizers influenced C partitioning, favoring C accumulation in roots, wood and fruits. The higher CO2 fixation was the result of a larger tree leaf area, rather than an increase in leaf photosynthetic efficiency, showing a stimulation of plant growth by application of compost. High concentrations of compost increased total soil N concentration, but were not effective in increasing nitrate-N soil concentration; in contrast mineral-N applications increased linearly soil nitrate-N, even at the lowest rate tested. Soil nitrate-N concentration influenced positively plant growth at low rate (60- 80 mg kg-1), whereas at high concentrations showed negative effects. In this trial, the decrease of root growth, as a response to excessive nitrate-N soil concentration, was not anticipated by root oxidative stress. Continuous annual applications of compost for 10 years enhanced soil organic matter content and total soil N concentration. Additionally, high rate of compost application (10 t ha-1 year-1) enhanced microbial biomass. On the other hand, different fertilizers management did not modify tree yield, but influenced fruit size and precocity index. The present data support the idea that organic fertilizers can be used successfully as a substitute of mineral fertilizers in fruit tree nutrient management, since they promote an increase of soil chemical and biological fertility, prevent excessive nitrate-N soil concentration, promote plant growth and potentially C sequestration into the soil.
47
Giani, Monardo. "A cost-based optimization of a fiberboard pressing plant using Monte-Carlo simulation (a reliability program)." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/30417/1/Monardo_Giani_Thesis.pdf.
Full textAbstract:
In this research the reliability and availability of fiberboard pressing plant is assessed and a cost-based optimization of the system using the Monte- Carlo simulation method is performed. The woodchip and pulp or engineered wood industry in Australia and around the world is a lucrative industry. One such industry is hardboard. The pressing system is the main system, as it converts the wet pulp to fiberboard. The assessment identified the pressing system has the highest downtime throughout the plant plus it represents the bottleneck in the process. A survey in the late nineties revealed there are over one thousand plants around the world, with the pressing system being a common system among these plants. No work has been done to assess or estimate the reliability of such a pressing system; therefore this assessment can be used for assessing any plant of this type.
48
Cook, Joni L. "Following Darwin's footsteps using 'the most wonderful plants in the world' : the ecophysiological responses of the carnivorous plant Drosera rotundifolia to nitrogen availability." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17778.
Full textAbstract:
Nitrogen (N) is an essential element to plants for growth, maintenance and reproduction, however most N does not exist in a form that is biologically available to plants. In order to maximise the acquisition and retention of N, plants have evolved a variety of morphological and physiological adaptations and life history strategies, as well as the ability to respond plastically to changes in resource availability in ecological time. Determining the ecophysiological responses of plants to changes in root N availability is crucial to further understanding of the mechanisms underlying competitive interactions between plants, and between plants and other organisms, that ultimately contribute to community structure and ecosystem functioning. Carnivorous plants are ideal systems for investigating ecophysiological responses to N availability as:- (i) they share a unique adaptation for obtaining supplemental N from captured prey, therefore ecological stoichiometry and energetic cost/benefit models may be explored; (ii) the trait of botanical carnivory is widely considered to have independently co-evolved as a response to N-deficient, sunny and wet environments, therefore resource allocation trade-offs between plant investment in N and carbon (C) acquisition may be observed, and (iii) they are extremely sensitive to changes in root N availability in ecological time. In this research, the carnivorous plant Drosera rotundifolia (round-leaved sundew) was used to address several unanswered ecophysiological and evolutionary questions relating to patterns and processes of prey capture and the N nutrition of carnivorous plants. Furthermore, the potential for reducing uncertainty in the calculation of plant reliance on carnivory using a δ15N natural abundance multi-level linear mixing model was explored. A combined approach of in-situ and ex-situ studies was employed, using co-occurring non-carnivorous plants or carnivorous plant species with differing evolutionary lineages or prey capture mechanisms respectively to provide context. Results show that the adaptations of carnivory, high reproductive investment and a relatively short life span enable Drosera rotundifolia to survive and thrive in an extreme, N deficient environment. Phenotypically plastic responses by the plant to light and root N availability provide evidence of resource allocation trade-offs between investment in carnivory for N acquisition and in photosynthesis for C acquisition. Plants invested less heavily in prey capture (measured as the stickiness of leaf mucilage) as N availability increased or light availability decreased. These results show that the energetic costs associated with carnivory are avoided by the plant when less costly sources of N are available for uptake and that the production of carbon-rich mucilage is only made under nutrient-limited and well-lit conditions. Results obtained from the comparison of captured insect prey with background invertebrates of potential prey indicate that Drosera rotundifolia is a dietary generalist, where the quantity of prey captured per plant is positively correlated with leaf stickiness and total leaf area. Plant reliance on prey-derived N decreased with increasing root N availability, providing evidence that carnivory is only of net benefit to the plant in N-deficient and well-lit environments, as the photosynthetic costs of investment in the trait are not exceeded by the energetic gain from prey N uptake in shady or dry habitats. A more accurate and precise method for calculating plant reliance on botanical carnivory is presented which incorporates the insect diet of the plant. This method has wider significance for reducing uncertainty in the calculation of relative source contributions to a mixture for most natural abundance applications using a multi-level linear mixing model. To conclude, results from this research further understanding of the ecophysiological mechanisms underlying plant responses to changes in resource availability and the selective pressures driving the evolution of plant adaptations. These results therefore assist with predicting how plants and plant communities may respond to sustained N deposition inputs and future environmental scenarios.
49
Goergen, Erin M. "The role of symbiotic nitrogen fixation in nitrogen availability, competition and plant invasion into the sagebrush steppe." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3355562.
Full text
50
Pisarczyk, Elizabeth W. "The effect of garlic mustard (Alliaria petiolata) density on soil nutrient availability and microbial enzyme activity in Northwest Ohio : a gradient analysis /." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1260236506.
Full textAbstract:
Thesis (M.S.)--University of Toledo, 2009.<br>Typescript. "Submitted as partial fulfillment of the requirements for The Master of Science Degree in Biology (Ecology-track)." "A thesis entitled"--at head of title. Bibliography: leaves 28-32.