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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

BIOMECHANICAL EFFECTS OF TREES AND SOIL THICKNESS IN THE CUMBERLAND PLATEAU

Shouse, Michael 01 January 2014 (has links)
Previous research in the Ouachita Mountains, Arkansas suggests that, on relatively thin soils overlying bedrock, individual trees locally thicken the regolith by root penetration into bedrock. However, that work was conducted mainly in areas of strongly dipping and contorted rock, where joints and bedding planes susceptible to root penetration are more common and accessible. This project extended this concept to the Cumberland Plateau, Kentucky, with flat, level-bedded sedimentary rocks. Spatial variability of soil thickness was quantified at three nested spatial scales, and statistical relationships with other potential influences of thickness were examined. In addition, soil depth beneath trees was compared to that of non-tree sites by measuring depth to bedrock of stumps and immediately adjacent sites. While soil thickness beneath stumps was greater in the Ouachita Mountains compared to the Kentucky sites, there were no statistically significant differences in the difference between stump and adjacent sites between the two regions. In both regions, however, soils beneath stumps are significantly deeper than adjacent soils. This suggests the local deepening effects of trees occur in flat-bedded as well as steeply dipping lithologies. Regression results at the Cumberland Plateau sites showed no statistically significant relationship between soil depth and geomorphic or stand-level ecological variables, consistent with a major role for individual tree effects. Nested analysis of variance between 10 ha stands, 1.0 ha plots, and 0.1 ha subplots indicates that about 67 percent of total depth variance occurs at, or below, the subplot level of organization. This highly localized variability is consistent with, and most plausibly explained by, individual tree effects. The effects of biomechanical weathering by trees are not limited to areas with strongly dipping and contorted bedrock. Variability of soil depth in the Cumberland Plateau is likely influenced by positive feedbacks from tree root growth, that these interactions occur over multiple generations of growth, and that the effects of trees are the dominant control of local soil thickness. Since lateral lithological variation was minimal, this study also provides evidence that the positive feedback from biomechanical weathering by trees leads to divergent development of soil thickness.
12

The Effects of Spatial Resolution on Digital Soil Attribute Mapping

Shaffer, Jared M. 19 September 2013 (has links)
No description available.
13

Produção e mortalidade de raízes finas em plantações de Eucalyptus grandis cultivados em Latossolos (Itatinga-SP) / Fine root turnover and lifespan in the Eucalyptus grandis plantations established in Oxisol (Itatinga-SP)

Lambais, George Rodrigues 24 November 2015 (has links)
As plantações brasileiras de eucaliptos apresentam um dos maiores valores da produção primária bruta (PPB) entre os diversos ecossistemas do mundo. Nos ecossistemas florestais, o fluxo total de carbono no solo é constituído em grande parte pela produção e mortalidade das raízes finas (diâmetro <= 2 mm), podendo representar 20-60% da PPB. Esse estudo teve como objetivo principal avaliar a dinâmica e o prazo de vida (PV) das raízes finas, através do método não-destrutivo de minirhizotrons (MR), em plantio de E. grandis (2-4 anos de idade) cultivados em latossolos. Os objetivos específicos foram divididos em três capítulos: i-) avaliar a influência da textura (20 e 40% de argila) na dinâmica das raízes finas, em camadas superficiais do solo (0-30 cm); ii-) estudar a dinâmica das raízes no solo arenoso até 6 m de profundidade; iii-) investigar as associações simbióticas das raízes finas de eucaliptos (2 anos do plantio) com fungos micorrízicos arbusculares (FMA) na superfície de solos com texturas contrastantes, e fungos ectomicorrízicos (ECM) em camadas profundas do solo arenoso (4 anos do plantio). As imagens da interface solo-MR foram produzidas quinzenalmente, através de um scanner portátil no interior dos tubos MR em um período de dois anos. O software WinRHIZO Tron foi utilizado para medir o comprimento e diâmetro das raízes finas que apareceram durante o estudo. O conteúdo de água no solo foi monitorado, até 10 m de profundidade com auxilio de sensores CS615 (Campbell), continuamente durante todo o período de estudo. As avaliações de FMA e ECM foram realizadas através de amostragens destrutivas do solo. Os resultados observados com os MR mostraram que a textura do solo teve influência direta no comprimento radicular na camada de 0-30 cm, onde o solo arenoso apresentou valores superiores em relação ao solo argiloso durante todo o estudo. Ao final de dois anos, o solo arenoso teve o dobro de comprimento total acumulado em relação ao solo argiloso, com 30 m m-2 imagem. Na mesma profundidade, as raízes finas provenientes do solo arenoso tiveram uma maior colonização por FMA em relação ao solo argiloso, com médias de 38,5 e 10,5%, respectivamente. Uma fraca correlação entre umidade do solo e a dinâmica de raízes para textura e profundidade do solo foi observada. As médias de elongação diária das raízes finas foram de 0,10 e 0,22 cm dia-1 na camada de 0-2 e 2-6 m de profundidade, respectivamente. A elongação diária máxima no perfil do solo foi de 3,5 cm dia-1 na camada de 5-6 m. Através de análises moleculares, foi identificada uma espécie de ECM (Pisolithus) na profundidade de 2-3 m. No geral, o PV e a taxa de ciclagem das raízes finas de eucaliptos foram em torno de 500 dias e 0,70 ano-1, respectivamente, não sofrendo influência significativa da textura e profundidade do solo. Quando as raízes finas foram analisadas por classe de diâmetro (< 0,03, 0,3-0,5 e 0,5-2,0 mm) e micorrização, observou-se uma diferença significativa na sua longevidade. As árvores de eucaliptos apresentaram uma alta capacidade de exploração do solo / Brazilian eucalyptus plantations are among the forest ecosystems in the world with the highest gross primary productivity (GPP). The total belowground carbon allocation, with mainly production and mortality of fine roots (diameter <= 2 mm), can account for 20-60% of GPP in forest ecosystems. This study aimed to evaluate the dynamic and lifespan of fine roots in E. grandis plantations (2-4 years old) established in Oxisol soils, using the non-destructive method of minirhizotrons (MR). The specific objectives of this study were divided into three chapters: i-) to evaluate the influence of soil texture (20 and 40% clay) in the dynamics of fine roots in the topsoil (0-30 cm); ii-) to study the dynamics of the fine roots in a sandy soil up to 6 m deep; iii-) to investigate the symbiotic associations of Eucalyptus fine roots (2 years old after planting) with arbuscular mycorrhizal fungi (AMF) in the upper soil layers for two contrasting soil textures, and ectomycorrhizal fungi (ECM) in deep layers of a sandy soil (4 years old after planting). Images at the interface soil-MR were taken fortnightly through a portable scanner within the MR tube over a period of two years. The WinRhizo Tron software was used to measure the length and diameter of the fine roots that appeared throughout the study period. Soil water contents were continuously monitored down to a depth of 10 m using CS615 sensors (Campbell). AMF and ECM were studied sampling soil cores. The MR technique showed that the soil texture direct influenced fine root growth in the 0-30 cm layer, with higher values in the sandy soil than in the clayey soil throughout the study period. After two years, the sandy soil reached a total cumulative length of 30 m m-2 image, which was twice as high as the clayey soil. At the same depth, fine roots had a greater colonization by AMF in the sandy soil compared to the clayey soil, with means of 38,5 and 10,5%, respectively. A weak correlation between relative extractable water and dynamics of fine roots was observed, whatever the soil texture and depth. The means of daily elongation of fine roots were 0,10 cm day-1 in the 0-2 m soil layers and 0,22 cm day-1 in the 2-6 m soil layer. The maximum daily root elongation throughout the soil profiles reached 3,5 cm day-1 at a depth of 5-6 m. A specie of ECM (Pisolithus) was identified through molecular analyzes at a depth 2-3 m. In general, the lifespan and the turnover rates of Eucalyptus fine roots were about 500 days and 0.70 yr-1, respectively, and the influences of soil texture and soil depth were not significant. The fine root longevity was significantly affected by the diameter class (< 0,3, 0,3-0,5 and 0,5-2,0 mm) and the mycorrhizal status, there was a significant difference in their longevity. The Eucalyptus trees exhibited a remarkably high capacity of soil exploration in the Oxisol studied
14

Produção e mortalidade de raízes finas em plantações de Eucalyptus grandis cultivados em Latossolos (Itatinga-SP) / Fine root turnover and lifespan in the Eucalyptus grandis plantations established in Oxisol (Itatinga-SP)

George Rodrigues Lambais 24 November 2015 (has links)
As plantações brasileiras de eucaliptos apresentam um dos maiores valores da produção primária bruta (PPB) entre os diversos ecossistemas do mundo. Nos ecossistemas florestais, o fluxo total de carbono no solo é constituído em grande parte pela produção e mortalidade das raízes finas (diâmetro <= 2 mm), podendo representar 20-60% da PPB. Esse estudo teve como objetivo principal avaliar a dinâmica e o prazo de vida (PV) das raízes finas, através do método não-destrutivo de minirhizotrons (MR), em plantio de E. grandis (2-4 anos de idade) cultivados em latossolos. Os objetivos específicos foram divididos em três capítulos: i-) avaliar a influência da textura (20 e 40% de argila) na dinâmica das raízes finas, em camadas superficiais do solo (0-30 cm); ii-) estudar a dinâmica das raízes no solo arenoso até 6 m de profundidade; iii-) investigar as associações simbióticas das raízes finas de eucaliptos (2 anos do plantio) com fungos micorrízicos arbusculares (FMA) na superfície de solos com texturas contrastantes, e fungos ectomicorrízicos (ECM) em camadas profundas do solo arenoso (4 anos do plantio). As imagens da interface solo-MR foram produzidas quinzenalmente, através de um scanner portátil no interior dos tubos MR em um período de dois anos. O software WinRHIZO Tron foi utilizado para medir o comprimento e diâmetro das raízes finas que apareceram durante o estudo. O conteúdo de água no solo foi monitorado, até 10 m de profundidade com auxilio de sensores CS615 (Campbell), continuamente durante todo o período de estudo. As avaliações de FMA e ECM foram realizadas através de amostragens destrutivas do solo. Os resultados observados com os MR mostraram que a textura do solo teve influência direta no comprimento radicular na camada de 0-30 cm, onde o solo arenoso apresentou valores superiores em relação ao solo argiloso durante todo o estudo. Ao final de dois anos, o solo arenoso teve o dobro de comprimento total acumulado em relação ao solo argiloso, com 30 m m-2 imagem. Na mesma profundidade, as raízes finas provenientes do solo arenoso tiveram uma maior colonização por FMA em relação ao solo argiloso, com médias de 38,5 e 10,5%, respectivamente. Uma fraca correlação entre umidade do solo e a dinâmica de raízes para textura e profundidade do solo foi observada. As médias de elongação diária das raízes finas foram de 0,10 e 0,22 cm dia-1 na camada de 0-2 e 2-6 m de profundidade, respectivamente. A elongação diária máxima no perfil do solo foi de 3,5 cm dia-1 na camada de 5-6 m. Através de análises moleculares, foi identificada uma espécie de ECM (Pisolithus) na profundidade de 2-3 m. No geral, o PV e a taxa de ciclagem das raízes finas de eucaliptos foram em torno de 500 dias e 0,70 ano-1, respectivamente, não sofrendo influência significativa da textura e profundidade do solo. Quando as raízes finas foram analisadas por classe de diâmetro (< 0,03, 0,3-0,5 e 0,5-2,0 mm) e micorrização, observou-se uma diferença significativa na sua longevidade. As árvores de eucaliptos apresentaram uma alta capacidade de exploração do solo / Brazilian eucalyptus plantations are among the forest ecosystems in the world with the highest gross primary productivity (GPP). The total belowground carbon allocation, with mainly production and mortality of fine roots (diameter <= 2 mm), can account for 20-60% of GPP in forest ecosystems. This study aimed to evaluate the dynamic and lifespan of fine roots in E. grandis plantations (2-4 years old) established in Oxisol soils, using the non-destructive method of minirhizotrons (MR). The specific objectives of this study were divided into three chapters: i-) to evaluate the influence of soil texture (20 and 40% clay) in the dynamics of fine roots in the topsoil (0-30 cm); ii-) to study the dynamics of the fine roots in a sandy soil up to 6 m deep; iii-) to investigate the symbiotic associations of Eucalyptus fine roots (2 years old after planting) with arbuscular mycorrhizal fungi (AMF) in the upper soil layers for two contrasting soil textures, and ectomycorrhizal fungi (ECM) in deep layers of a sandy soil (4 years old after planting). Images at the interface soil-MR were taken fortnightly through a portable scanner within the MR tube over a period of two years. The WinRhizo Tron software was used to measure the length and diameter of the fine roots that appeared throughout the study period. Soil water contents were continuously monitored down to a depth of 10 m using CS615 sensors (Campbell). AMF and ECM were studied sampling soil cores. The MR technique showed that the soil texture direct influenced fine root growth in the 0-30 cm layer, with higher values in the sandy soil than in the clayey soil throughout the study period. After two years, the sandy soil reached a total cumulative length of 30 m m-2 image, which was twice as high as the clayey soil. At the same depth, fine roots had a greater colonization by AMF in the sandy soil compared to the clayey soil, with means of 38,5 and 10,5%, respectively. A weak correlation between relative extractable water and dynamics of fine roots was observed, whatever the soil texture and depth. The means of daily elongation of fine roots were 0,10 cm day-1 in the 0-2 m soil layers and 0,22 cm day-1 in the 2-6 m soil layer. The maximum daily root elongation throughout the soil profiles reached 3,5 cm day-1 at a depth of 5-6 m. A specie of ECM (Pisolithus) was identified through molecular analyzes at a depth 2-3 m. In general, the lifespan and the turnover rates of Eucalyptus fine roots were about 500 days and 0.70 yr-1, respectively, and the influences of soil texture and soil depth were not significant. The fine root longevity was significantly affected by the diameter class (< 0,3, 0,3-0,5 and 0,5-2,0 mm) and the mycorrhizal status, there was a significant difference in their longevity. The Eucalyptus trees exhibited a remarkably high capacity of soil exploration in the Oxisol studied
15

Distributed Hydrological Modeling Using Soil Depth Estimated from Landscape Variable Derived with Enhanced Terrain Analysis

Tesfa, Teklu K. 01 May 2010 (has links)
The spatial patterns of land surface and subsurface characteristics determine the spatial heterogeneity of hydrological processes. Soil depth is one of these characteristics and an important input parameter required by distributed hydrological models that explicitly represent spatial heterogeneity. Soil is related to topography and land cover due to the role played by topography and vegetation in affecting soil-forming processes. The research described in this dissertation addressed the development of statistical models that predict the soil depth pattern over the landscape; derivation of new topographic variables evaluated using both serial and parallel algorithms; and evaluation of the impacts of detailed soil depth representation on simulations of stream flow and soil moisture. The dissertation is comprised of three papers. In paper 1, statistical models were developed to predict soil depth pattern over the watershed based on topographic and land cover variables. Soil depth was surveyed at locations selected to represent the topographic and land cover variation at the Dry Creek Experimental Watershed, near Boise, Idaho. Explanatory variables were derived from a digital elevation model and remote sensing imagery for regression to the field data. Generalized Additive and Random Forests models were developed to predict soil depth over the watershed. The models were able to explain about 50% of the soil depth spatial variation, which is an important improvement over the soil depth extracted from the SSURGO national soil database. In paper 2, definitions of the new topographic variables derived in the effort to model soil depth, and serial and Message Passing Interface parallel implementations of the algorithms for their evaluation are presented. The parallel algorithms enhanced the processing speed of large digital elevation models as compared to the serial recursive algorithms initially developed. In paper 3, the impact of spatially explicit soil depth information on simulations of stream flow and soil moisture as compared to soil depth derived from the SSURGO soil database has been evaluated. The Distributed Hydrology Vegetation Soil Model was applied using automated parameter optimization technique with all input parameters the same except soil depth. Stream flow was less impacted by the detailed soil depth information, while simulation of soil moisture was slightly improved due to the detailed representation of soil depth.
16

Above- and belowground competition in Savanna systems.

Payne, Michelle Jennifer. January 2008 (has links)
The structure and composition of savanna vegetation is influenced by resource availability and disturbance. Grasses, a major component of savannas, influence this resource availability by competing directly with trees for light, water and soil nutrient resources. The direct causes of bush encroachment are not always apparent, but are commonly ascribed to overgrazing and consequent decreased grass competition. The interaction, both above and belowground, between tree and grass seedlings and the surrounding grass sward is dependant on many factors, such as soil depth, seedling species and sward composition. These factors, as well as the presence or absence of defoliation, in the form of grazing or fire dictate whether the system will remain in a transition state as savanna or move towards a stable woodland state. The major competitive effects experienced by the tree seedlings were dependant on grass species and nutrient level. A. nilotica was affected by aboveground competition while A. karroo was affected by belowground competition. E. capensis caused the greatest decrease in A. karroo plant biomass. Both E. capensis and H. hirta had large competitive effects on the aboveground biomass of A. nilotica, while S. africanus had the greatest effect on belowground biomass. Increasing nutrient availability resulted in an increase in the competitive effect exerted on A. karroo, while little to no change was seen in the competitive effect exerted on A. nilotica. Soil depth constrained plant size in both tree species. The intensity of belowground interactions on tree biomass was unaffected by soil depth, while aboveground competition had a significant effect on shallow soils. Belowground competition was also of greater importance than aboveground competition in dictating tree seedling height. Grass seedlings growing on all three soil depths differed in mean mass, with E. racemosa having the least mass and T. triandra having the greatest. Simulated grazing by cutting the surrounding sward resulted in biomass increases in all three grass species. Changes in savanna composition and structure are thus likely to be influenced by initial species composition and soil depth and soil nutrient composition. While grazing creates niches for grass seedling establishment, heavy grazing has been observed to increase grass seedling mortality. Encroachment is thus more likely to occur on intensively grazed shallow and deep soils than on medium depth soils. This highlights the importance of ensuring the grass sward remains vigorous by resting and monitoring stocking rates to ensure veld is not over-utilized. It is then possible to maintain some form of tree-grass coexistence at a level where available grazing is not compromised. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
17

Risker och åtgärder för saltvatteninträngning i dricksvattenbrunnar i ett nutids- och framtidsperspektiv / Risks and preventive measures of saltwater intrusion in drinking water wells in a present and future perspective

Bizet, Alicia January 2022 (has links)
Drygt en miljon invånare i Sverige är beroende av enskild dricksvattenförsörjning från grundvatten. För låga grundvattennivåer i grundvattenmagasin, kan bland annat leda till saltvatteninträngning i dricksvattenbrunnar. Syftet med studien var att fastställa om topografi, avstånd till hav, brunnsdjup, jorddjup och jordart är kopplat till kloridhalter i dricksvatten, att undersöka om och vad det finns för risker för saltvatteninträngning i ett framtida förändrat klimat, av klimatförändringar, samt om det finns några åtgärder mot saltvatteninträngning.  Korrelationstestet Kendall’s tau användes för att undersöka om det fanns en signifikant korrelation mellan kloridhalter och topografi, avstånd till hav, brunnsdjup och jorddjup och Wilcoxon rank sum test användes för att undersöka om det fanns någon signifikant skillnad mellan de olika jordarterna. I denna studie fastställdes negativ korrelation mellan kloridhalter och avstånd till hav (p=0,000341), samt kloridhalter och topografi (p=0,0124). Studien visade på att det inte fanns någon signifikant korrelation mellan kloridhalter och resterande parametrar, vilket tidigare forskning dock indikerar. Vad gäller brunnsdjup, fanns en signifikant korrelation mellan topografi och brunnsdjup, vilket kan tyda på att brunnar generellt är borrade grundare i låglänta områden. Gällande jorddjupet kopplat till kloridhalter, antogs det vara för tunt (cirka en meter) för att kunna se något tydligt resultat av korrelationstestet, då ett för tunt jordlager inte påverkar grundvattenbildningen i tillräckligt stor utsträckning. Detta bidrog även till att det inte fanns någon signifikant skillnad mellan jordarterna.  För den andra delen av studien utformades en modell i Matlab, för att undersöka om och hur klimat- förändringar kommer påverka grundvattennivåförändring och därmed även saltvatteninträngning. Referensperioden var 2004-2020 och framtidsscenariona var RCP4.5 och RCP8.5, vilka delades upp i två olika perioder: 2021-2060 och 2061-2099. Modellen visade på att grundvattennivåer blir lägre i ett framtida påverkat klimat, vilket kan tyda på att det är en större risk för saltvatteninträngning. Dock fanns det många osäkerheter och modellen skulle kunna göras mer nyanserad.  För den tredje delen av studien gjordes en litteraturstudie där sju olika åtgärder undersöktes: kontrollering av grundvattenuttag, vattensnåla åtgärder i hemmet, att borra grundare brunnar i riskområden, anslutning till kommunalt vatten, omvänd osmos, ADR (abstraction, desalination, recharge) och SWT (subsurface water technologies). Dessa jämfördes därefter mot varandra genom att ställa upp för- och nackdelar för alla åtgärder. Överlag är förebyggande åtgärder att föredra, dock tycks SWT eller ADR vara bättre än omvänd osmos för redan kontaminerat vatten. / Just over one million inhabitants in Sweden are dependent on individual drinking water supply from groundwater. When the groundwater levels are too low in a groundwater reservoir, it can lead to saltwater intrusion in drinking water wells. The purpose of this study was to establish whether topography, distance to sea, well depth, soil depth and type of soil correlated with chloride in drinking water, to investigate whether there is a risk for saltwater intrusion in a future changed climate, due to climate change, and to investigate if there are any measures to minimize saltwater intrusion.  Kendall’s tau was used to investigate if there were any significant correlations between chloride and topography, distance to sea, well depth and soil depth. Wilcoxon rank sum test was used to investigate if there was a significant difference between the soil types. In this study the results only showed a significant correlation between chloride and distance to sea (p=0,000341) and between chloride and topography (p=0,0124). There was no significant correlation between chloride and the rest of the parameters. However, earlier research has shown that there is a correlation between chloride and all previous mentioned parameters. There was a significant correlation between topography and well depth, which can imply that the wells are drilled shallower in lowland areas. Regarding the soil depth connected to chloride, it is assumed that the soil depth is too thin (about one meter) to see any clear results, since a shallow soil depth won’t affect the groundwater recharge enough. This could also contribute to no significant difference between chloride and soil types.  For the second part of the study a model was built in Matlab, to investigate if and how climate change will affect changes in groundwater levels and therefore if it will influence saltwater intrusion. The reference period was 2004-2020 and the future scenarios were RCP4.5 and RCP8.5, which were divided into two periods: 2021-2060 and 2061-2099. The model showed lower groundwater levels in the future, which can imply there is a greater risk of saltwater intrusion. Although there are multiple limitations and the model could be made more nuanced.  For the third part of this study, a literature study was made, where seven different measures where investigated: to control groundwater abstraction, to install waterefficient techniques in households, to drill shallower wells in risk areas, reversed osmosis, ADR (abstraction, desalination, recharge) and SWT (subsurface water technologies). These were compared to each other, where advantages and disadvantages were balanced against each other. Overall, preventative measures are preferable, although SWT and ADR are better than reversed osmosis for already contaminated water.
18

Attitudinal, Economic and Technological Approaches to Wastewater Management in Rural Ohio

Vedachalam, Sridhar 25 July 2011 (has links)
No description available.
19

Small but powerful

Scharroba, Anika 19 May 2017 (has links)
In der vorliegenden Arbeit wurden die Einflüsse der landwirtschaftlichen Nutzung auf die Struktur und Biomasse von Nematoden entlang eines Tiefengradientens und innerhalb zweier Vegetationsperioden an einem Ackerstandort untersucht. Die Freilandanalyse der Nematodengemeinschaft wies auf ein mit Nährstoffen angereichertes und gestörtes Ökosystem, mit einer geringen Diversität, hin. Entlang des Tiefengradienten bildeten die Nematoden Metacommunities, welche Umweltgegebenheiten wie Nahrungsquellen und abiotischen Faktoren widerspiegeln. Signifikant höhere Biomassen wurden unter Weizen im Vergleich zu Mais als Ackerfrucht beobachtet. Die Streuapplikation induzierte einen „bottom-up“ Effekt mit größeren Biomassen in den niedrigen als in den höheren trophischen Stufen. Die Nematoden Biomassen sowie die faunistischen Indizes (Channel Index, Enrichment Index) zeigten, dass der Kohlenstofffluss im Bakterienkanal des Bodens dominierte. Allerdings deckte das 13C Pulse-Labelling Experiment im Feld auf, dass der Kohlenstofffluss durch die Pilzgemeinschaft sowie die pilzfressenden Nematoden wesentlich höhere Umsatzraten aufweist. In einem 14C-Laborexperiment wurde ein vollständiges Budget des Flusses von wurzelbürtigem Kohlenstoff in das Nahrungsnetz der Nematoden bestimmt. Hierbei wiesen die pflanzenparasitären Nematoden die höchsten 14C-Gehalte innerhalb weniger Tage auf, da sie direkt an den Wurzeln fressen und über die Herbivorenkette den Nährstoffzyklus im Boden eröffnen. / The present research considered the effects of agricultural management practice on the nematode community structure and biomass in three different depths and two successive vegetation periods at an arable field site. The resource quality was manipulated by crop plant and organic amendment, to investigate the major soil carbon pathways based on roots, bacteria and fungi. The nematode community analysis pointed to a highly enriched and disturbed ecosystem with low biodiversity. Along the depth gradient the nematodes formed distinct metacommunities, reflecting resource availability and abiotic environmental factors. Wheat supported significantly greater nematode biomass than maize. The litter amendment induced bottom-up effects, with greater biomass allocation at lower than at higher trophic levels. The biomass of nematode families as well as faunal indices (Channel Index, Enrichment Index) revealed a predominance of the bacterial carbon channel in the arable soil. A 13C pulse-labelling experiment investigating the flux of root- derived C into the soil food web revealed high turnover rates in the fungal carbon pathway. This was evident for soil fungi as well as for fungal-feeding nematodes and contradicts general assumptions of a more active bacterial pathway in arable soils. A laboratory experiment with 14C isotope was used to compile a complete budget for the root-derived carbon in the nematode food web. Here plant-feeding nematodes, which feed on living plant roots, thereby opening the root C cycling into the food web, showed highest amounts of 14C allocation within a few days.
20

Investigating Rainwater Harvesting as a Stormwater Best Management Practice and as a Function of Irrigation Water Use

Shannak, Sa'D Abdel-Halim 2010 December 1900 (has links)
Stormwater runoff has negative impacts on water resources, human health and environment. In this research the effectiveness of Rain Water Harvesting (RWH) systems is examined as a stormwater Best Management Practice (BMP). Time-based, evapotranspiration-based, and soil moisture-based irrigation scheduling methods in conjunction with RWH and a control site without RWH were simulated to determine the effect of RWH as a BMP on a single-family residence scale. The effects of each irrigation scheduling method on minimizing water runoff leaving the plots and potable water input for irrigation were compared. The scenario that reflects urban development was simulated and compared to other RWH-irrigation scheduling systems by a control treatment without a RWH component. Four soil types (sand, sandy loam, loamy sand, silty clay) and four cistern sizes (208L, 416L, 624L, 833L) were evaluated in the urban development scenario. To achieve the purpose of this study; a model was developed to simulate daily water balance for the three treatments. Irrigation volumes and water runoff were compared for four soil types and four cistern sizes. Comparisons between total volumes of water runoff were estimated by utilizing different soil types, while comparisons between total potable water used for irrigation were estimated by utilizing different irrigation scheduling methods. This research showed that both Curve Number method and Mass-Balance method resulted in the greatest volumes of water runoff predicted for Silty Clay soil and the least volumes of water runoff predicted for Sand soil. Moreover, increasing cistern sizes resulted in reducing total water runoff and potable water used for irrigation, although not at a statistically significant level. Control treatment that does not utilize a cistern had the greatest volumes of predicted supplemental water among all soil types utilized, while Soil Moisture-based treatment on average had the least volume of predicted supplemental water.

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