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.
2001
Sammendrag
The coffee leaf miner Leucoptera coffeella (Lepidoptera: Lyonetiidae) is one of the most important coffee pests in Lathin America. Larvae of L. coffeella were collected at 10 different locations in a coffee growing region in Nicaragua to study the natural occurrence of insect pathogenic hyphomycetous fungi. The study reveals that Beauveria bassiana (Deuteromycotina: Hyphomycetes) might be a natural mortality factor for L. coffeella larvae, and a B. bassiana infection level up to 22.1 % was observed. To our knowledge, this is the first study estimating the B. bassiana infection level in L. coffeella, and also one of the first reports on B. bassiana associated with this insect. Significant and positive correlations with B. bassiana infection level in L. coffeella larvae were observed for factors related to high L. coffeella densities, and the coffee variety "Catrenic" showed a significant higher L. coffeella density as well as a higher B. bassiana infection level than the other coffee varieties. A tendency towards higher B. bassiana infection level with increasing shading was also observed. Copper was applied as a fungicide at some of the locations, but did not seem to negatively affect the B. bassiana infection level as much as other fungicides. In this study coffee leaves were also examined for endophytic B. bassiana, but no such association was found.
Forfattere
Rolf D. Vogt E.T. Gjessing Dag Olav Andersen Nicholas Clarke T.C. Gadmar K. Bishop U.S. Lundström Michael StarrSammendrag
In the Total Organic Carbon (TOC) intercalibration sub-project a set of 10 synthetic and natural samples as well as non-labile reverse osmosis isolates were sent to 25 laboratories for the analysis of TOC and dissolved Organic Carbon (DOC).The outcome of the statistical treatment of the results from this intercalibration and the information regarding the participants instruments and standard operational procedures is that:Synthetic samples provide apparent better precision than natural samples. This fact, together with the good experience from the use of non-labile Reverse Osmosis (RO) and freeze dried isolates of dissolved organic carbon (DOM) in the intercalibration, lead us to recommend the use of RO isolates as material for the preparation of house standards and for determination of methods merits.The intra laboratory precision (relative standard deviation) varied from 5 to 16%.The fractionation of the DOC by 0.45um membrane filtering causes in some cases a contamination of carbon to the sample.A specific construction in a brand of the TOC analysers give poor results in samples with high TOC concentrations and that are of refractory material. The five selected sampling sites have proven, on the basis of their soil and water chemistry, to be well suited for studying the effect of climate and S-deposition on the characteristics of DOM. 163 water samples from two seasons (fall and spring) and 20 soil samples are collected and analysed.Most water samples are determined for all major charge contributing species, DOM fractions, and several other parameters. The DOM in the surface waters have been isolated both using reverse osmosis and hydrophobic resin (XAD8). The original surface water, reconstructed water by RO isolates as well as the XAD8 fractionated DOM have been characterized by a number of methods ranging from optical properties to pH and metal titration.The RO isolates have been provided to 14 scientific research groups in Europe and North America that are in the process of using their analytical technique to characterize the DOM.The soils have been determined for key explanatory variables as pH, cation exchange capacity and C/N ratio. The main findings from the characterisation of DOM is that:Generally the hydrophobic acid fraction (HPO-A) was the main DOM fractions in all water compartments and sites.Seasonal variation in the DOM fractionation is found to be greater than the variation between the sites and water compartments. The DOM fractionation is therefore not a fingerprint of the site.According to a batch titration experiment the aluminium complexing ability of the HPO-A and hydrophilics (HPI) DOM fractions (fractionated using only the XAD8 resin) was indistinguishable.The HPI fraction has generally a higher site density of weak acids (WA).The reverse osmosis (RO) isolates represent the total DOM in the original sample.NMR spectres of the RO isolates show that the main difference between the sites lie in the amounts of carbohydrates and aromatic compounds.The RO isolates produce reconstructed water with DOM that have similar optical properties.PCA analysis suggest that as the S-deposition is decreasing we should expect relatively more hydrophobic character of the DOM.The spring sample from Svartberget differs from the rest of the samples in that there was a small rainstorm causing a hydrologic episode during the sampling. This led to the lowest pH, highest TOC and organic charge (A-) among the surface water samples. In terms of DOM characteristics this temporal variation in flow regime led to the highest HPO-N DOM fractions, lowest intensity of the NMR spectre and low ash content and lower density of WA then expected. This expresses the importance of temporal variation during hydrologic episodes.
Forfattere
Rolf D. Vogt K. Bishop Nicholas Clarke T.C. Gadmar E.T. Gjessing Jan Mulder Michael Starr Dag Olav AndersenSammendrag
The main tasks of the NOMiNiC project (Natural Organic Matter in the Nordic countries; see http://www.kjemi.uio.no/envir/nominic/) is to study the physiochemical characteristics of dissolved organic matter (DOM) and provide reverse osmosis (RO) spring and fall isolates of surface water natural organic matter (NOM) from 5 Nordic forested sites that differ mainly in atmospheric S-loading and climate. Hydrophobic and hydrophilic fractions are hypothesized to be more easily defined and have distinct different chemical characteristics than the total sample. A XAD-8 fractionation may then be used as a simple proxy for the physico-chemical properties of NOM. Both XAD-8 fractions and the total DOM sample have been base and metal titrated. Enhanced understanding of the significance of the numerous operationally defined parameters describing NOM will be achieved through a common multi-dimensional characterisation of the same set of isolates, that span a large spectre of the variation found in DOM. 7 institutes are already collaborating in characterizing the RO isolates using a large range of techniques and new participants are invited. In this presentation the 5 sampling sites are described and some results of the characterisation of the RO isolates are presented.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Per Holm Nygaard Roald BreanSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor J. JohansenSammendrag
Populations of carrot flies (Psila rosae Fabr.) may build up in areas where carrots are grown year after year. High numbers of flies normally result in larval damage and unmarketable carrot roots. An integrated strategy for controlling the "one generation" carrot flies in Northern Norway includes non-chemical methods like crop rotation, selecting suitable growing sites (isolated, wind exposed) and crop covers. Adjusting sowing and harvest times is seldom an option, as the carrots need the relatively short and cool growing season to complete growth. The carrot growers often have to apply insecticides to achieve a sufficient reduction in larval damage. In Norway, like many other countries, insecticides are applied when trap catches of adult flies exceed a certain threshold. The current insecticides are normally applied as drenches and are targeted against the young larval stages feeding on the carrot roots. Recently, high insecticide residues in carrots sprayed with fenthion were found and diazinon is now the only approved insecticide against carrot flies in Norway. To minimise the risk for residues, the pyrethroid lambdacyhalothrin is now being tested in field trials after promising results in laboratory tests. In addition to a well known "knock down" effect when the spray hits the flies directly, chemical residues on the carrot foliage may kill adult flies up to two weeks after spraying (cage tests). In our field trials, with small spraying plots, lambdacyhalothrin proved to be effective when the spray was applied soon after the first flies appeared. Application after the onset of egglaying, failed to prevent damage. This year (2000), we are performing experiments including treatment of whole fields with pyrethroids. The results from these trials will give a more realistic test of a possible new strategy in carrot fly control; killing adult flies instead of larvae.
Forfattere
Svein Ole BorgenSammendrag
The purpose of this working paper is to review the new theories on cost management, particularly addressed by the so-called “Relevance Lost”-perspective. This perspective is developed by the two American professors of accounting, Robert S. Kaplan and H. Thomas Johnson. Their point of departure is that in the current climate of rapid technological change, vigorous global and domestic competition and the enormous expansion of information-processing capabilities, current management accounting systems are inadequate and outdated. Their contribution has triggered a fresh and welcomed debate on new management accounting systems. However, the debate is not easily accessible, and the ambition of this working paper is to critically review some of the novel perspectives. Focus is on conceptual issues rather than operational questions, implementation or empirical evidence. The purpose is to discuss strengths and weaknesses of the different models, and explore the conditions under which they seem to be most adequate.
Forfattere
Mekjell MelandSammendrag
Det er ikke registrert sammendrag
Forfattere
Gustav FystroSammendrag
Ein del viktige prosessar knytt til nitrogen i eng er diskutert. Avlingskurver og utnytting av tilført nitrogen er sentralt. Opptak av nitrogen og fraksjonering i planter og jord er drøfta ut frå forsøksresultat med bruk av isotopen 15N. Problem knytt til gjødslingsplanlegging er drøfta, der mineralisering av nitrogen er ei stor utfordring. Utvikling av røter i eng er omtala. Artikkelen diskuterer også konflikter mellom miljøverknader og økonomisk resultat i engproduksjon.