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
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.
Sammendrag
The process of model building in the environmental sciences and when dealing with ecosystems is discussed. Two types of modeling approaches need to be distinguished: An algorithmic one, which has been used traditionally in physics, meteorology, and other branches where biological degrees of freedom are either absent or neglectable; and an interactive one, which is a new framework in computer science and seems to be most suitable in cases where organisms (including humans) as agents in ecosystems are to be taken into account. The first modeling approach is exemplified by state models in dynamic systems theory and expresses the correspondence imposed by Natural Law between inferential entailment in a formal system and causal entailment in natural systems. Modeling is to be separated from simulation. Simulation is a less restrictive type of modeling in which the description of non-interactive behaviour is the purpose and no constraints on the correspondence to internal states are imposed. The second (new) modeling approach is exemplified by interactive simulation models. It is able to express the correspondence in behaviour imposed by engineering standards (or cultural norms in general) between documentation, training and application in interactive choice situations such as games or ecosystem management. It generalises the notion of simulation for interactive problems. In an idealised situation the strictest correspondence between behaviour in a natural and a virtual system is expressed as bisimulation. The principles for model building are shortly demonstrated with examples.
Forfattere
Petter Snilsberg Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Sammendrag
The forest stand growth simulator TRAGIC (tree response to acidification in groundwater in C) which has been developed to serve as a decision support system and a visualisation tool for scientists and forestry practitioners is introduced. TRAGIC places an emphasis upon visualisation techniques while at the same time providing detailed information on tree physiology and related parameters. The model is calibrated numerically to growth history data from two different European sites.Next, due to the importance of the visual component of the model, its ability to reproduce forest stand spatial structure is investigated, using an application of the theory of marked point processes. This analysis is applied to different experimental data sets for stands of different age, revealing information on planting schemes and the extent of significant spatial correlations.The spatial structure of the two model calibrations is then explored with the same methods. The point process analysis turns out to be a powerful diagnostic for model quality assessments, since spatial distribution is an indirect result of competition between trees for light.
Sammendrag
Målsetting med prosjektet har vært å 1) klarlegge vegetasjonssoners effekt på tilbakeholdelse av partikkelbundne pesticider ved overflateavrenning fra jordbruksarealer, 2) bestemme potensialet for nedbrytning av partikkelbundne pesticider i jordprøver fra vegetasjonssona og 3) validere modeller som beskriver effekten av vegetasjonssoner på avrenning av pesticider som bindes til partikulært materiale. Ugrasmiddelet glyfosat og soppmidlene fenpropimorf og propikonazol er brukt i prosjektet. Resultatene viser at gjennomsnittlig renseeffekt gjennom en 5 bred vegetasjonssone var høy; 51-62 % for partikler, 39-48 % for glyfosat, 34-71 % for fenpropimorf og 63-85 % for propikonazol. Glyfosat har sterk binding til jord, noe som kan forklare godt samsvar mellom renseeffekt for partikler og glyfosat/AMPA, mens fenpropimorf og propikonazol har moderat binding til jord. Forskjellen i Kd-verdi innenfor et begrenset område er imidlertid stor, og viser at stedsspesifikke data er nødvendig. Over 80 % av total overflateavrening oppsto i løpet av vinterhalvåret, mens vinternedbøren var 28 % av totalnedbøren. Det var ingen signifikant forskjell i renseeffekt (%) for noen av parametrene mellom sommer og vinter, men total renseeffekt (i g) var større om vinteren pga høyere avrenning. Dette er sannsynligvis pga løsrivelse av grovere aggregater om vinteren, som sedimenterer lettere i vegetasjonssona. Løst og lett tilgjengelig glyfosat blir raskt nedbrutt, mens sterkt bundet glyfosat som er lite tilgjengelig, blir sakte nedbrutt. Halveringstiden for alle stoffene er lang og bindingsgraden stor slik at spredningen vil være dominert av partikkelbundet materiale. Vegetasjonssoner kan derfor være en effektiv måte å redusere forurensning av elver og sjøer. Simulering med GLEAMS modellen overestimerer overflateavrenning av glyfosat og fenpropimorf, mens total avrenning av propikonazol ligger innenfor et akseptabelt nivå. Modellen er svært sensitiv for avrenning i perioder nær frysing og tining, særlig senhøstes. Simuleringene har vist at problemstillingen frysing/tining ikke er tilfredsstillende løst og det er derfor nødvendig å se nærmere på den nye versjonen GLEAMS 3.0.
Forfattere
N. Syversen Roar Linjordet Ole Martin Eklo Christian ThorstensenSammendrag
Det er ikke registrert sammendrag
Sammendrag
The notion of an ecological damage has so far neither been given a proper theoretical nor a pragmatic or operational foundation. Yet one of the most widespread motivations for the scientific study of ecosystems is a “protectional” one by which an improved scientific understanding is sought in order to be able to prevent future ecological damages. We review the possibilities of valuating changes in the environment, in health or in ecosystems as a damage. The conceptual separation of potential from actual behaviour/structure is a prerequisite to any of them. The critical point here is the formal and empirical basis for the knowledge about these potentials. We contrast the dynamic systems theory approach derived in physics with an interactive computing approach recently developed in computer science. The former requires to distinguish facts and values and leads to notorious difficulties when applied at the ecosystem level. The latter and novel approach opens the possibility for a consistent definition of a damage at the ecosystem level whenever a tradition of (sustainable) utilization of such systems is available. The documentation, actualisation and dissemination of the tacit (expert) knowledge can be improved by the use of interactive simulations in which a virtual standard can defined by the respective experts themselves.