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Dans un contexte de limitation de l'utilisation des pesticides, une voie de recherche prometteuse porte sur le déterminisme environnemental actionnant les mécanismes de défense de la plante, entre autres, la production de métabolites secondaires. L'objectif de mon travail de thèse a été d'étudier le compromis entre croissance et défense (métabolisme primaire vs. secondaire) dans les tissus de la plante saine ou attaquée par différents bioagresseurs, sous différentes conditions de disponibilité en ressources. Pour cela, nous avons mesuré différents paramètres de croissance, les ratios C/N des tissus, les concentrations en principaux métabolites primaires (glucides simples, amidon) et en composés de défense (acide chlorogénique, rutine, kaempferol-rutinoside et tomatine) dans différents organes de tomate en culture hydroponique en serre ou phytotron. Nous avons observé que les variations des ratios C/N total et de ressources sont positivement corrélées à celles de nombreux composés de défense quelle que soit leur composition en N et C. De plus, nous avons montré qu'en présence d'un bioagresseur, les concentrations des composés primaires et secondaires ne suivent pas la même évolution selon leur nature. La synthèse de caffeoyl putrescine est fortement induite lors de l'attaque par P. syringae alors que la concentration en acide chlorogénique est diminuée. L'inoculation de P. syringae réduit les concentrations en glucose et fructose alors que P. corrugata stimule leur synthèse. Enfin, nous avons observé qu'une faible disponibilité en azote altère le développement de P. syringae, P. corrugata et Tuta absoluta mais favorise le développement de Botrytis cinerea. Nos résultats ont montré que le ratio C/N est un indicateur fiable du compromis croissance/défense dans le cas d'une plante saine. Dans le cas d'une plante attaquée, la répartition des ressources entre les différents métabolites varie en fonction du bioagresseur. Et chaque bioagresseur réagit de façon différente aux variations de disponibilité en azote de la plante. La maîtrise des conditions de culture apparaît comme un levier agronomique pertinent pour raisonner la lutte contre les bioagresseurs même s'il est difficile d'appliquer des règles générales sur l'interaction plante/environnement/bioagresseurs / Nowadays, limiting the use of pesticides is mandatory. A promising way for research deals with the environmental determinism of plant defence mechanisms, among others, production of secondary metabolites. The aim of my PhD work was to study the trade-off between growth and defence (primary vs. secondary metabolism) in healthy plant tissues or attacked by different pests, under different conditions of resources availabilities. We measured different growth parameters, C:N ratios of tissue, concentrations of main primary metabolites (simple carbohydrates, starch) and defence metabolites (chlorogenic acid, rutin, kaempferol-rutinoside and tomatine) on healthy or attacked tomato plant grown in hydroponic culture in greenhouse or phytotron. We observed that variations of total and resources C:N ratios were positively correlated to that of several defence compounds whatever their composition in carbon and nitrogen. Moreover, we showed that, during pests attack, concentrations of primary and secondary metabolites did not follow the same evolution, depending on their nature. Caffeoyl putrescine synthesis was strongly induced by P. syringae inoculation whereas chlorogenic acid concentration decreased. Inoculation of P. syringae induced a strong decrease of concentration of glucose and fructose whereas inoculation of P. corrugata enhanced their synthesis. We observed that a low N availability alters the development of P. syringae, P. corrugata and Tuta absoluta but promotes the development of B. cinerea. Our results showed that C:N ratio is a reliable indicator of the trade-off between growth and defence in the case of healthy plant. In attacked plant, the resources allocation between different metabolites varies with pests. And each pests reacts specifically to changes of N availability for the plant. Control of culture conditions appears to be a relevant agronomic tool to monitor the control of pests even if it is difficult to apply general rules to the interaction plant/environment/pests

Tato diplomová práce stručně popisuje proces anaerobní fermentace, rozdělení bioplynových stanic a vybrané parametry, které byly sledovány v praktické části. V praktické části byly při laboratorním testování anaerobní fermentace v Celorepublikové referenční laboratoři bioplynových transformací na Mendelově univerzitě v Brně sledovány následující parametry: složení a množství vznikajícího bioplynu, konduktivita, oxidačně redukční potenciál, pH, obsah sušiny, celkového organického uhlíku, celkový obsah dusíku v sušině a poměr C:N ve zpracovávaném materiálu. Výsledky analyzovaných parametrů byly vyhodnoceny, interpretovány a na jejich podkladě byly navrženy možnosti jejich použití pro screeningovou diagnostiku provozních stavů bioplynových stanic.

Increasing atmospheric CO2 and other greenhouse gasses coupled to the accelerated rate of global warming puts plants and ecosystems under the strain of a rapidly changing abiotic environment. Understanding the impacts of changing global climate is a strong focus of plant science and the establishment of more resilient crop variants is an important goal for breeding programs. Our understanding of plant responses and acclimation to abiotic conditions has improved substantially over the last decades but the combination of a complex abiotic environment and high biological diversity, both on molecular as well as on species level, leaves us still with a lot of uncertainties. The aim of this doctoral thesis was to establish a link between plant thermal responses and the carbon-nitrogen balance of plants. The work in this thesis focused on ecologically significant species of the boreal region: Picea abies, Pinus sylvestris and Betula pendula; and Betula utilis, which is one of the prominent tree species in the high altitudes of the Himalayas. The results presented demonstrate that sub-optimal temperatures combined with other abiotic factors can have additive effects that are not easily deducible from the effect of the two factors separately. Low nitrogen availability enhanced the negative effect of low temperature, while elevated CO2 enhanced plant growth under moderate increases in temperatures but under a more extreme temperature increase it exacerbated the negative effect of heat. I also show evidence that species, despite being grouped into the same functional group or inhabiting the same biome can have different thresholds to temperature and to shifts in the C/N balance of their environment and that these differences can, to some extent, be explained by their differential growth strategies. Furthermore, I demonstrate results supporting the hypothesis that the C-N fluxes between mycorrhizal fungi and tree are strongly dependent on the C and N in the environment, highlighting the significance of the tree-mycorrhiza associations in the C sequestration capacity of the boreal region. In this thesis I also present a generalised empirically based mathematical model that can describe the respiration-temperature response of plant functional types or biomes with high precision, giving a more accurate estimate of NPP when implemented in global climate models, and has the potential to incorporate the thermal acclimation of respiration, further increasing the precision of estimating carbon fluxes under future warming temperatures. My results provide novel insights into the interactive temperature-carbon-nitrogen responses of plants, taking a step towards better understanding the response of plants and forests to future climates. / Ökande atmosfäriskt CO2 och andra växthusgaser kopplade till den accelererande globala uppvärmningen utsätter växter och ekosystem för stressen av en snabbt förändrande abiotisk miljö. Att förstå påverkan av ett globalt klimat i förändring står i fokus inom växtforskning och utvecklandet av mer motståndskraftiga grödor är ett viktigt mål inom programmen för växtförädling. Vår förståelse av växters responser och acklimatisering till abiotiska förhållanden har förbättrats avsevärt under de senaste decennierna, men på grund av kombinationen av en komplex abiotisk miljö och stor biologisk mångfald, både på molekylär nivå såväl som på art-nivå, kvarstår en del frågetecken. Syftet med denna avhandling var att upprätta ett samband mellan växters responser på temperaturförändringar och kol-kvävebalansen hos växter. Arbetet i denna avhandling inriktades på ekologiskt betydande arter i den boreala regionen, Picea abies, Pinus sylvestris and Betula pendula; samt Betula utilis som är en av de framträdande trädarterna på höga höjder i Himalaya. Resultaten som presenteras visar att suboptimala temperaturer i kombination med andra abiotiska faktorer kan ha additiva effekter som inte enkelt kan härledas från effekten av de två faktorerna var för sig. Låg kvävetillgänglighet ökade den negativa effekten av låg temperatur, medan förhöjd CO2-halt förbättrade planttillväxt under måttliga temperaturökningar, men under en mer extrem temperaturökning förvärrades dock den negativa effekten av värme. Jag framför även bevis på att arter, trots att de grupperas i samma funktionella grupp eller finns inom samma biom, kan ha olika tröskelvärden beträffande temperatur och förskjutningar i C/N-balansen i sin miljö och att dessa skillnader, i viss utsträckning, kan förklaras av deras olika tillväxtstrategier. Vidare visar jag resultat som stöder hypotesen att C-N - flöden mellan mykorrhiza och träd är starkt beroende av C och N i miljön. Detta belyser i sin tur betydelsen av samarbetet mellan träd och mykorrhiza gällande kolbindningskapaciteten i den boreala regionen. I denna avhandling presenterar jag även en generaliserad empiriskt baserad matematisk modell som med hög precision kan beskriva respiration-temperatur svar av växtfunktionella typer eller biom, vilken ger en mer exakt uppskattning av NPP i globala klimatmodeller. Mina resultat åstadkommer nya insikter i de interaktiva temperatur-kol-kväve-responserna hos växter, och tar ett steg mot bättre förståelse för växters och skogars reaktion på framtida klimat.

Soil organic matter is important as storage for carbon and nutrients, supporting soil structure, and as a filter for pollutants entering the soil ecosystem. The recovery of soil organic matter in depleted soils can take decades, or even hundreds of years. It has been assumed that in non-eroding pasture, soil carbon levels either increase or not change over time. However, some recent studies have suggested that fertiliser addition to pasture soils may contribute to decreases in soil carbon content. My hypotheses were: 1. As P fertiliser loadings increase the soil carbon content and C:N ratio will decrease. 2. Changes in C pools will be greater in the more active pool (readily available carbon, and microbial biomass carbon) within the soil total carbon The study was undertaken at a long term fertiliser trial, established in 1980, at the Whatawhata Hill Country Research Station west of Hamilton, New Zealand. The fertiliser trial has P fertiliser application rates maintained since 1984. Olsen P, total C, total N, labile carbon, respirable carbon, specific respiration rate, microbial biomass C, microbial quotient, mineralised N, microbial biomass N, microbial N quotient, and mineralised N per microbial biomass nitrogen, C:N ratio, and soil pH were measured on soil samples collected from 12 paddocks with six P fertiliser loading (0, 10, 20, 30, 50, 100 kg P ha-1 yr-1). As expected, the available P (Olsen P) increased significantly (P less than 0.001) with increasing P fertiliser application rate. Total carbon, labile carbon, and total nitrogen all decreased significantly (P less than 0.05) with increasing P fertiliser application. No significant relationships were found between P fertiliser and respirable carbon, microbial carbon, microbial (C) quotient, microbial specific respiration, microbial nitrogen, microbial (N) quotient, mineralised N, or C:N ratio. The first hypothesis was rejected as the C:N ratio did not change with increased P fertiliser application. However, both C and N decreased with increased P fertiliser application. The second hypothesis was, therefore, accepted in part because there was a decrease in labile carbon (readily available carbon) and total carbon, with P fertiliser application, but no relationship was evident for the respirable carbon and microbial biomass.

Mysid shrimps (Mysidacea, Crustacea) are efficient zooplanktivores in both marine and freshwater systems as well as lipid rich prey for many species of fish.  Although some efforts have been made to study the role of mysids in the Baltic Sea, very few studies have been carried out in recent time and there are still knowledge gaps regarding various aspects of mysid ecology. This thesis aims to explore some of these gaps by covering a mixture of topics. Using multifrequency hydroacoustics we explored the possibility to separate mysids from fish echoes and successfully established a promising and effective method for obtaining mysid abundance/biomass estimates (paper I). An investigation of the current mysid community in a coastal area of the northern Baltic proper (paper II) demonstrated that the formerly dominant, pelagic mysid Mysis mixta had decreased substantially (~50%) in favor for phytoplanktivorous, juvenile Neomysis integer and Mysis relicta sp. By examining different aspects of mysid behavior, we studied the vertical size distribution of mysids in the field and found that size increased with depth/declining light, irrespective of temperature; indicating that their vertical size distribution primarily is a response to predation (paper II). In paper III, a combination of ecological and genetic markers was used to investigate intraspecific differences in migratory tendency. Both marker types indicated that some part of the Mysis salemaai population is sedentary on the bottom and that this strategy is a phenotypically plastic but persistent trait, analogous to the partial migrations seen in many birds and fishes. In paper IV a temperature and weight specific respiration model was developed for the littoral Praunus flexuosus. Routine respiration was moreover elevated by post-prandial effects (specific dynamic action) for longer times than previously suggested. Consequently, ignoring such effects could significantly bias respiration measurements. / At the time of doctoral defence the following papers were unpublished and had a status as follows: Paper  2: Accepted; Paper 3: Submitted; Paper  4: Accepted

Background: Wetlands store significant amounts of carbon through plant respiration and anaerobic peat formation, however, there is little knowledge on which factors affect the carbon storage distribution within wetlands. Aims: To determine how much carbon and nitrogen wetlands can store over time and whether there are patterns of high and low carbon and nitrogen storage within wetlands. Methods: Peat samples of a defined volume, cut out from three constructed wetlands were dried, weighed and analysed for their carbon and nitrogen content. To determine whether there are any patterns in carbon and nitrogen storage distribution or differences between sampling points, their values as well as their ratios were statistically analysed using ANOVA and Kruskal-Wallis. Results: On average 48.94 t C ha-1is stored at the constructed wetland facility which equates 3.06 t C ha-1 storage per year. There is no patterns in carbon storage within wetlands, however, the C:N mass ratio is lower at the inlet suggesting that high N concentrations in inflowing water increases N content. Conclusions: The carbon storage found is significantly lower than storage at natural inland and coastal wetlands, however, similar to anthropogenically affected wetlands. Standardisation across studies through using same sampling depths, vegetation cover measurement and climate classification may help to uncover patterns in carbon storage in the future. Focus should be placed on protecting wetlands rather than restoring them as the latter often fails to restore full functionality. This is especially important for cold climate wetlands which store significantly more carbon through slower plant respiration and subsequently slower re-uptake of carbon.

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Exotic species alter the streamside plant community by changing the resources available to the stream food web, causing cascading changes throughout the entire aquatic ecosystem. To better understand the impacts of exotic litter species on stream communities, investigations were made at global and local levels. A meta-analysis was performed to understand which environmental and litter quality factors impact native and exotic litter decay rates on the global scale. It was found that exotic species are likely to decay faster than native species at larger mesh sizes, and in warm temperature environments because high quality exotic leaves have a lower C:N ratio than native leaves. An urban litter decay experiment in Victoria, B.C. streams contrasting Alnus rubra, Salix sitchensis, Hedera sp., Rubus armeniacus and plastic trash found that trash decays more slowly than leaf litter, but leaf species all decay at the same rate, and stream invertebrates colonize all litter types equally. Significant differences in litter decay rates and invertebrate community alpha and Shannon diversities were also observed across the four different streams. The more that is learned about the impacts of exotic leaf litter, the better we are able to respond to keep streams as healthy and as biodiverse as possible. / Graduate / 2017-08-10 / 0329 / 0793 / kimkenn@uvic.ca

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