Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2004
Sammendrag
Sampling the catchment outlet generally is assumed to be a convenient way to infer information about a variety of biogeochemical processes at the catchment scale as it provides a spatial and temporal integral of the predominating catchment output fluxes for a number of chemical compounds of interest.Moreover, the short-term dynamics and long-term trends of the hydrograph and of solute concentrations in the catchment runoff can provide information about the predominating processes at the catchment scale and can be used to refine conceptual and mathematical models.Additional measurements inside the catchment, e.g., of soil solution, groundwater, and stream water at different sites, are used to relate the findings to within-catchment processes and thus to further constrain hypotheses and models.
Forfattere
Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Forfattere
Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Sammendrag
The sun is an abundant energy source, and increasing efforts are made to find more efficient ways to exploit it, than commonly used today. Hydrogen is considered to be the energy carrier of the future, and the potential for a sustainable system where hydrogen is obtained directly from solar energy, has been studied extensively. One alternative is the process of biophotolysis. Sulfur starvation of the green algae Chlamydomonas reinhardtii is known to cause hydrogen production under illumination, by biophotolysis where solar energy is used to produce significant amounts of hydrogen involving parts of the photosynthetic process. So far, little is known about this process in other species, and in this work we have investigated different species of green algae with respect to hydrogen production under sulfur starvation. A number of algae cultures were screened with respect to physiological response to sulfur deprivation in small-scale laboratory cultures under controlled conditions. Test parameters included hydrogen production, reduction of oxygen production, changes in morphology and other aspects of physiology. Investigations of oxygen sensitivity of hydrogenases were also performed. It was shown that other species than C. reinhardtii are able to produce hydrogen under sulfur deprivation.
Sammendrag
Using Singular System Analysis (SSA), we extract a collection of significant long-term components (with dominant periods of at least 3 years) for a large number of river runoff records.At first glance, these long-term modes are a distinct feature of this variable, not contained in precipitation and temperature, and not easily correlated to commonly known long-term indices (NAO, SOI, NHT, SUN, etc.). However, low-pass filtered versions of these time series exhibit strikingly similar behavior, like common maxima, within a region (such as Southern Germany), pointing to a common origin.Although not an unequivocal example for synchronization, we quantify the degree of synchronization as a function of the regional extent of the data and propose a mechanism, stochastic resonance, discussed in climate dynamics, which is able to produce this collective behavior despite the lack of deterministic drivers. We also comment on air pressure-induced teleconnections between the different large scale oscillations in the climate system.
Forfattere
Atle HaugeSammendrag
Denne rapporten er skrevet som en delrapport til prosjektene Vegetative buffersoner i nord, finansiert av fylkesmannen i Nordland, Møre og Romsdal, Nord-Trøndelag og Interregprosjektet NOLIMP, med NIVA som prosjektleder. Miljøkanaler er enkle hydrotekniske tiltak med multiple funksjoner: (1) Vann ledes ut av areal (2) vannkvaliteten bedres ved at vannet utsettes for naturlige renseprosesser (3) estetikken og det biologiske mangfoldet bedres lokalt. Miljøkanaler er en videreutvikling av vanlige hydrotekniske vannveier og har likheter med miniatyr fangdammer. Anleggene er tilpasset lokale forhold, tar liten plass, hindrer erosjon i vannveiene og er rimelige å anlegge. Nærhet til forurensningene gir trolig bedre renseresultat fordi rent vann fra utmark ofte kan ledes utenom. Av den grunn kan rensetiltak lages mindre enn vanlige fangdammer. Rapporten gjennomgår utforming og komponentene miljøkanalen kan lages av, slik som sedimentasjonskammer, terskler, engeridrepere og våtmarksfilter. Det gis forslag til måter å anlegge miljøkanaler, gode råd og løsninger på problem som kan oppstå. Mange av forslagene er framstilt med skisser.
Sammendrag
Ecosystems as objects of natural sciences are often difficult to understand, as an object of traditional management they are sometimes easy to utilize. Computer-based modeling offers new tools to study this apparent paradox.We propose an interactive framework from which the traditional approach based on dynamic system theory can be challenged for living systems: Models derived on the basis of the state concept have not (yet?) allowed predictions that derive novel management competence relevant for the altered boundary conditions of ecosystems. Here a concept of interaction as currently used in information sciences serves as starting point for deriving models more appropriate for ecosystems.An application and test of this concept consists in a search for signatures of interaction in environmental and ecological time series. Confronted with the notorious lack of detailed process understanding, it is plausible to rely on time series analysis techniques. The intricate nature of typical multivariate data sets from ecosystems immediately suggests a preference for nonlinear techniques, and among them temporally local methods, able to detect even subtle changes in the underlying dynamics.We shortly introduce a couple of these methods, which have been demonstrated to be appropriate for time series exceeding minimal length requirements. This is exemplified by recurrence quantification analysis. In addition we present methods to quantify the memory content (Hurst analysis) and complexity of data sets (defined in an informationtheoretic context).Time series analysis of extended environmental and ecological data sets can give detailed structural insights, monitors subtle changes undetectable otherwise, forms the basis for further inferences and provides rigorous model testing on all scales. The success of dynamic system theory when applied to non-living environmental data is strikingly contrasted by the difficulties of the same method when dealing with ecological data We conjecture that this difference reflects the extent to which interaction has been disregarded for ecosystems.
Forfattere
Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Forfattere
Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Sammendrag
Most energy carriers that are in common use today originate from solar energy. Hydrogen is considered to be the energy carrier of the future, and the potential for a sustainable system where hydrogen is obtained directly from solar energy, has been studied by several researchers over the years. Several groups of microorganisms have shown the ability to produce hydrogen by natural biological processes using solar energy. Efforts have been made to understand the mechanisms involved in photobiological hydrogen production from these organisms, and to optimise the process. This work has recently resulted in a significant breakthrough. It has been discovered that some species of green algae have the ability to produce significant amounts of hydrogen during sulphur starvation, which allows hydrogen to be produced in light. However, very little is known about how this process varies between species. We have chosen to investigate green algae, with the intention to examine a variety of species for hydrogen production during sulphur starvation. A number of algae cultures were screened with respect to physiological response to sulphur deprivation in small-scale laboratory cultures under controlled conditions. Results from both marine and fresh water algae will be presented.