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.
2003
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Forfattere
Marianne BechmannSammendrag
The aim of a P index for Norway is to localize fields where measures should be implemented. In contrast to general implementation of measures this will affect only fields with a high risk of P loss and thus, do not put substantial restrictions on fields, which do only have marginal impact on water quality. The P index has been adapted to different geographic regions throughout the U.S.A. If properly constructed, the P index concept may be a valuable tool for managing P losses from agricultural landscapes in Norway. Analysis of existing data that describes the relationship between P loss and site-specific factors is needed for selection of appropriate factors, ratings and weightings for a geographically adapted P index. This review suggests that P-AL may be used as a factor for soil P content, though the relationship between P-AL and runoff of dissolved P needs further investigation. The special factors related to cold climate needs to be evaluated for the P application factor, e.g. release of soluble P from frozen plant residues. The P application factor also needs to be adapted to local methods of P application, including both incorporation of manure on arable land, surface application on pastures and grazed land. The Norwegian erosion risk mapping may form a basis for the erosion factor, though some additional estimates needs to be developed, e.g. the concentrated flow erosion and differences in erosion caused by aspect. A factor for runoff generation may consist of hydraulic conductivity and amount of precipitation. Tile draining creates a need for evaluation of the factor for P loss through subsurface drainage. The connectivity factor is most important for surface runoff, since subsurface water is usually connected to the stream by tiles. The water quality of a recipient in addition to diffuse agricultural pollution depends on the existence of agricultural point sources. Evaluation of the possibilities for using the P index concept in Norway includes an assessment of how many indices are needed to represent the differences in conditions of different areas. The development of P indices represents an easy means of identifying and rank the risk of areas within a catchment as to their vulnerability to P loss.
Sammendrag
Several biocells varying from 100 m3 to about 8000 tons have been established at waste treatment locations in Norway since 1998. We studied biocells by characterizing the waste material by degradation, gas and leachate emission and post-treatment potential, by taking several samples distributed in space and time. Field sample analyses were water content, leachate temperature, redox conditions, oxygen content, electrical conductivity and pH, and gas temperature, O2, CH4 and CO2 concentrations. Waste samples were drilled up by a 10-inch auger down to 6 m depth. The collected samples were analyzed and used for composting experiments. The temperature in the biocelles varied between 10 to 14 ºC in the period from august to December. The waste was characterised as completely or slightly completely degraded after 4 years of biocell storage/treatment, based on "Rotte-test" and respirometer analyses. Microbial analyses showed that the material was free from salmonella, but contained some thermotolerant colibacteria in the most degraded part. Samples from the slightly degraded waste were also free from thermotolerant colibacteria. None of the waste samples showed any inhibition against the germination of plants. The temperature in the most degraded material did not increase significantly during composting. This material can thus not be treated aerobically after removal from the biocell, ie. for reducing pathogens. The factors leachate strenght measured as electrical conductivity, BOD and C/N-ratio best explained the methane content of the biogas in each sampling point. A total production of 593 t landfill gas has been measured from the large biocell. The annual mean methane concentration increased from 28 to 56%, with an overall mean of 48%. This gives a 21% degradation of organic carbon in four years, based on certain assumptions on the incoming waste. The estimated degradation of organic matter is between 50% and 75% in four years.
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The rationale for stand growth modelling is often either grounded in a search for improved scientific understanding or in support for management decisions. The ultimate goal under the first task is seen in mechanistic models, i.e. models that represent the stand structure realistically and predict future growth as a function of the current status of the stand. Such mechanistic models tend to be over-parameterized with respect to the data actually available for a given stand. Calibration of these models may lead to non-unique representations and unreliable predictions. Empirical models, the second major line of growth modelling, typically match available data sets as well as do process-based models. They have less degrees of freedom, hence mitigate the problem of non-unique calibration results, but they employ often parameters without physiological or physical meaning. That is why empirical models cannot be extrapolated beyond the existing conditions of observations. Here we argue that this widespread dilemma can be overcome by using interactive models as an alternative approach to mechanistic (algorithmic) models. Interactive models can be used at two levels: a) the interactions among trees of a species or ecosystem and b) the interactions between forest management and a stand structure, e.g. in thinning trials. In such a model data from a range of sources (scientific, administrative, empirical) can be incorporated into consistent growth reconstructions. Interactive selection among such growth reconstructions may be theoretically more powerful than algorithmic automatic selection. We suggest a modelling approach in which this theoretical conjecture can be put to a practical test. To this end growth models need to be equipped with interactive visualization interfaces in order to be utilized as input devices for silvicultural expertise. Interactive models will not affect the difficulties of predicting forest growth, but may be at their best in documenting and disseminating silvicultural competence in forestry.
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Forfattere
Carl-Einar Amundsen Roar LinjordetSammendrag
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