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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.
1

Carbon flow in belowground food webs assessed by isotope tracers

Scheunemann, Nicole 20 March 2015 (has links)
No description available.
2

Spatial distribution of soil nematodes in the sub-arctic environment of Churchill, Manitoba

Lumactud, Rhea Amor 07 April 2010 (has links)
The tundra ecosystem, with its frost-molded landscape and large peat reserves, is vulnerable to climate change. Thus, any increase in temperature due to global warming will cause changes in above-and belowground biota. Understanding the linkage between these biotas will help make prediction of the biodiversity and ecosystem functioning when global change phenomena occur, and consequently aid in making management strategies. The role of nematodes in nutrient cycling and decomposition, among many other attributes, make them useful organisms to study soil processes. Associations between plant and nematode communities, from six sites (Berm Face, Berm Crest, Tundra Heath, Polygon, Hummock and Forest) and from within a young, visually homogeneous tundra heath field site, were examined in the subarctic environment of Churchill, Manitoba. The study also provided nematofaunal information, which is very limited in this region. Multivariate analyses of nematode taxa abundance revealed four distinct groupings: Berm Face, Berm Crest, heaths (Tundra Heath, Polygon and Hummock) and Forest. The result showed a parallel relationship between nematode and vegetation assemblages, and thus, a seeming interdependency between above-ground and below-ground biota. Conversely, association between nematode and plant assemblages within a visually homogeneous tundra site was not as obvious. At this fine scale, the heterogeneous nature of edaphic factors and not plant assemblages is hypothesized to influence within-site nematode communities. The thesis also provided results to improve nematofaunal analysis to enhance their utility as bioindicators of soil food webs.
3

Spatial distribution of soil nematodes in the sub-arctic environment of Churchill, Manitoba

Lumactud, Rhea Amor 07 April 2010 (has links)
The tundra ecosystem, with its frost-molded landscape and large peat reserves, is vulnerable to climate change. Thus, any increase in temperature due to global warming will cause changes in above-and belowground biota. Understanding the linkage between these biotas will help make prediction of the biodiversity and ecosystem functioning when global change phenomena occur, and consequently aid in making management strategies. The role of nematodes in nutrient cycling and decomposition, among many other attributes, make them useful organisms to study soil processes. Associations between plant and nematode communities, from six sites (Berm Face, Berm Crest, Tundra Heath, Polygon, Hummock and Forest) and from within a young, visually homogeneous tundra heath field site, were examined in the subarctic environment of Churchill, Manitoba. The study also provided nematofaunal information, which is very limited in this region. Multivariate analyses of nematode taxa abundance revealed four distinct groupings: Berm Face, Berm Crest, heaths (Tundra Heath, Polygon and Hummock) and Forest. The result showed a parallel relationship between nematode and vegetation assemblages, and thus, a seeming interdependency between above-ground and below-ground biota. Conversely, association between nematode and plant assemblages within a visually homogeneous tundra site was not as obvious. At this fine scale, the heterogeneous nature of edaphic factors and not plant assemblages is hypothesized to influence within-site nematode communities. The thesis also provided results to improve nematofaunal analysis to enhance their utility as bioindicators of soil food webs.
4

The Role of Soil Biology and Plant Health – Brandywine Tomatoes Grown with Different Microbial Additions / Jordbiologins roll för jord- och växthälsa – Brandywinetomater kultiverade med olika mikrobiella tillskott

Eriksson, Mikael January 2020 (has links)
The microbial life in the soil is essential for providing a functioning habitat for plants to grow. A literature study was conducted to investigate the knowledge and science behind soil biology. The purpose of this study was to define what is soil health and how it is influenced by the soil microbial communities. The literature study concluded that the ability of soil biology to benefit plants includes a variety of aspects. Nutrient availability, soil structure and pest resistance are all greatly influenced by soil microbes.  To practically examine these theories, an experiment was conducted where Brandywine tomatoes where grown in three different scenarios. A commercial potting soil, Hasselfors ekojord, was used as substrate in all groups. In the control group (C) the plants were grown only in the substrate. In the second group (R), the seeds where treated with a microbial inoculum and then planted in the substrate. In the third group (RE), the same treatment as in R was done to the seeds and here, compost extract were also added to the RE group. The plants were grown in separate pots in a greenhouse and the growth rate was observed and documented as well as the total harvest. In the end of the growing season a chemical and biological analysis was done to the soil as well as a sap analysis on the leaves. The plant growth where similar among the groups although R and RE showed slightly higher growth rates in the later stages of the growing season. The harvested fruit was highest in C but not significantly. The microbial contents were high in all soils though more fungi communities in the RE and bacterial communities in C. The chemical analysis showed high nitrate concentrations in the leaves in C. In R and especially RE the nitrate conversion into amino acids and proteins where higher wish indicates that these groups are more resilient to pests like aphids. / Det mikrobiella livet i jorden är avgörande för att skapa en fungerande livsmiljö för växter. En litteraturstudie genomfördes för att undersöka nuvarande kunskap och vetenskap bakom markbiologi. Syftet med denna studie var att definiera markhälsa och hur den påverkas av det mikrobiella livet i jorden. Slutsatsen från denna litteraturstudie var att jordbiologins förmåga att gynna växter innefattar en rad olika aspekter. Näringstillgänglighet, markstruktur och skadedjursbeständighet påverkas starkt av jordmikrober.  För att praktiskt granska dessa teorier genomfördes ett experiment där Brandywine-tomater odlades i tre olika scenarier. En kommersiell plantjord, Hasselfors ekojord, användes som huvudsubstrat i alla grupper. I kontrollgruppen (C) odlades växterna endast i substratet. I den andra gruppen (R) behandlades frön med en mikrobiell ympning innan de såddes i substratet.I den tredje gruppen (RE) utfördes samma fröbehandling som i R och kompostextrakt tillsattes också till RE-gruppen. Växterna odlades i separata krukor i ett växthus och tillväxthastigheten observerades och dokumenterades liksom den totala skörden. I slutet av växtsäsongen gjordes en kemisk och biologisk analys av jorden samt en savanalys på bladen. Tillväxten var likartad bland grupperna även om R och RE visade något högre tillväxttakt i de senare stadierna av växtsäsongen. Skördad frukt per planta var högst i C, dock intesignifikant. Den mikrobiella koncentrationen var hög i alla jordar men mer svamporienterat i RE och bakterieorienterat i C. Den kemiska analysen visade högt nitratinnehåll i bladen i C. I R och särskilt i RE var nitratomvandlingen till aminosyror och proteiner högre vilket indikerar att dessa grupper är mer motståndskraftiga mot skadedjur så som bladlöss.
5

Assessment of heavy metal contamination and restoration of soil food web structural complexity in urban vacant lots in two post-industrial cities

Sharma, Kuhuk 04 November 2014 (has links)
No description available.
6

The soil food web of temperate deciduous forests: litter and root resources as driving factors, and soil fauna effects on ecosystem processes

Grubert, Diana 04 April 2016 (has links)
No description available.
7

Molecular Analysis of Centipede Predation

Eitzinger, Bernhard 19 July 2013 (has links)
No description available.
8

Soil animal food webs in temperate forests: effects of forest management on trophic structure as indicated by molecular gut content, stable isotope and fatty acid analyses

Ferlian, Olga 20 June 2014 (has links)
No description available.
9

Influence de l’utilisation de plantes de services sur les communautés de nématodes et les fonctions du sols dans un agroécosystème bananier en phase d’interculture / Influence of cover-crops on nematode communities and soil functions in a banana agroecosystem in fallow stage

Chauvin, Camille 10 December 2015 (has links)
L’introduction de biodiversité végétale dans les agroécosystèmes peut modifier la structure des réseaux trophiques du sol et les fonctions écosystémiques qu’ils assurent. Cette thèse fixe les bases d’une démarche expérimentale pour sélectionner des espèces végétales à partir de différents traits fonctionnels et pour évaluer leurs effets sur les réseaux trophiques et le fonctionnement des sols. Nous avons plus particulièrement cherché à sélectionner des plantes de services pouvant induire la régulation des nématodes parasites du bananier Radopholus similis et Pratylenchus coffeae et favoriser la décomposition des matières organiques durant l’interculture dans les bananeraies antillaises. C'est-à-dire la période entre la destruction de la bananeraie et l'implantation d'une nouvelle. Au cours de ce travail, les réseaux trophiques du sol ont été appréhendés par une analyse fonctionnelle des communautés de nématodes. Une étude bibliographique nous a permis de montrer que les traits fonctionnels « statut d’hôtes » vis-à-vis des nématodes phytoparasites, « composition biochimique des litières » et « productivité primaire des espèces végétales » contribuent aux effets des plantes sur les réseaux trophiques du sol et sur les deux services écosystémiques étudiés. Nous avons donc effectué une typologie des plantes de services à partir de ces traits. Puis pour étudier les effets d’apports de litières de composition biochimique contrastée sur les communautés de nématodes du sol, nous avons sélectionné les espèces végétales Paspalum notatum, Crotalaria zanzibarica et Acacia auriculiformis dont les litières présentaient des teneurs variables en hémicellulose, cellulose, azote, et lignine. Une étude en microcosmes a montré que la composition biochimique des litières détermine les successions écologiques au sein des communautés de nématodes et stimule de manière contrastée les voies de décomposition de la matière organique dans les sols. Nous avons discuté des mécanismes de régulation des nématodes parasites du bananier induits par ces apports de litières. Nous avons également montré que la culture de ces trois espèces induit une diminution des populations de R. similis dans les sols. Enfin, nous avons évalué les effets au champ de couverts de P. notatum, de C. zanzibarica et d’un couvert associant ces deux espèces. Pour cela, nous avons cultivé ces couverts durant neuf mois avant de les détruire et de restituer leurs litières à la surface des sols. Nos résultats montrent que ces couverts végétaux influencent différemment l’abondance en nématodes phytoparasites et le potentiel infectieux du sol. Ils induisent également des régulations bottum-up et top down dans leurs communautés. Après la restitution des litières, nous avons observé de fortes abondances de nématodes liées à la décomposition des litières dans la couche de surface du sol. Celle-ci fournit les couches sous-jacentes du sol en azote minéral et favorise le développement des nématodes omnivores et prédateurs. Il en résulte la formation de communautés de nématodes structurées et diversifiées concomitantes à la réduction des populations de R. similis et P. coffeae. Ces résultats étaient plus marqués pour les couverts monospécifiques de C. zanzibarica et les couverts mixtes. Nos travaux confirment que les traits fonctionnels « statut d’hôte », « production primaire », « composition biochimique des litières » sont déterminant pour sélectionner des plantes de services pour l’interculture en bananeraies. / Increased plant diversity may alter soil food web structure and soil function in agroecosystems. This thesis sets the basis for an experimental approach in order to select some plant species in regard to several functional traits and to assess their effect on soil food web and soil functioning. We focused on cover-crops able to induce regulation of the banana parasitic nematodes Radopholus similis and Pratylenchus coffeae and to promote decomposition of organic matter during the fallow period in banana plantations in the French West Indies (FWI). We used functional analysis of nematode communities as a soil food web bio-indicator. Bibliography studies show us that “plant host status” with respect to plant-parasitic nematodes, “biochemical characteristics of litters” and “primary productivity of plants” are functional traits involved in plant species effects on soil food web and on the ecosystemics service we targeted. We therefore use those traits to perform a typology of cover-plants. Furthermore, to study the effects of litter inputs with contrasted biochemical characteristics we pick out the plant species Paspalum notatum, Crotalaria zanzibarica and Acacia auriculiformis which show differential hemicellulose, cellulose, lignin and nitrogen content. A microcosm assay shows that biochemical characteristics of litter determine ecological successions in nematode communities and promote, in a contrasted manner, the decomposition pathway of organic matter. We discussed the mechanisms of plant parasitic nematodes suppression involved by those litter inputs. We also confirm that the culture of those three plant species can diminish the population of R.similis in soils. We also assessed the effects of plant covers composed of P. notatum and C. zanzibarica and a mix of those two plant species on nematodes communities during a field trial. In order to do so, we cultivated those cover-plants during a nine months period and then destroyed them to restitute plant litter in soils surface. Our results showed that cover-plant alters differentially plant-parasitic nematodes and the infectious potential of soils. Cover-crop cultivation also induced bottom-up and top-down regulations in plant parasitic nematode communities. After litter restitution, we observed high abundance of nematodes involved in litter decomposition within the soil surface layer. The latter provides underlying soil layers with mineral nitrogen and improves omnivore and predator nematode abundances. It results in the formation of a structured and diversified nematode community concomitantly with R. similis and P. coffeae regulation in soils. We observed greater effects with the cover-crop composed of C. zanzibarica and the mix of C. zanzibarica and P. coffeae. This study confirms that the functional traits of “host status”, “biochemical composition of litter” and “primary production” of plant species are decisive in the selection of cover-crop for the fallow period in banana plantation.
10

Fine root traits, belowground interactions and competition effects on the rhizosphere of <i>Fagus sylvatica</i> and <i>Fraxinus excelsior</i> saplings

Beyer, Friderike 05 December 2012 (has links)
No description available.

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