Sökning: "niche"
Visar resultat 21 - 25 av 286 avhandlingar innehållade ordet niche.
21. Economic Aspects of Fuel Cell-Based Stationary Energy Systems
Sammanfattning : It is evident that human activity has an important impact on climate. Constantly increasing energy demand is one of the biggest causes of climate change. The fifth assessment report of the Inter-governmental panel on climate change states that decarbonisation of electricity generation is a key component of climate change mitigation. LÄS MER
22. Dynamics of omnivorous crayfish in freshwater ecosystems
Sammanfattning : In this thesis I examine the dynamics of crayfish in streams and lakes. I have studied the influence of abiotic and biotic factors on abundance, growth, trophic position, niche breadth, and recruitment of crayfish, by conducting field studies, an outdoor channel experiment and timeseries analysis. LÄS MER
23. Rarity in boreal stream: patterns, causes and consequences
Sammanfattning : Patterns of site occupancy among boreal stream insects were studied in central Sweden with focus on sparsely distributed species and the role of dispersal and niche limitations.In the study of dispersal limitation, I found that effects of an extraordinarily harsh winter in small to medium-sized streams were strongest in sites located in small streams and far from lake outlets. LÄS MER
24. Ecology of parasitoids and their hosts in oilseed rape fields
Sammanfattning : Oilseed rape fields are a very common crop in the agricultural landscape of southern Sweden, and they can harbour surprisingly many insect species. Some of them are herbivores that feed on various parts of the oilseed rape plant, others are natural enemies of the herbivores, and even more species are tourists from the surrounding landscape. LÄS MER
25. Systematics, phylogeography and polyploid evolution in the Dactylorhiza maculata complex (Orchidaceae)
Sammanfattning : The aim of this thesis was to investigate and describe different aspects of variation in the Dactylorhiza maculata complex and to relate the variation patterns to underlying biological processes such as Quaternary migration history, hybridization and polyploid evolution. The variation patterns were analysed at various geographic levels using molecular markers (plastid DNA and ITS of nrDNA), cytological data, morphometry and ecological data. LÄS MER