Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2000
Authors
Åke LindelöwAbstract
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Authors
Torbjørn OkstadAbstract
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Abstract
Nitrogen is among the most important plant nutrients, and the effects on forest trees of changes in the concentrations and fluxes of both inorganic and organic nitrogen need to be known. In Norway, much of the nitrogen present in natural waters is organic (Mulder et al., 2000), therefore this fraction can not be neglected. Work using glycine has shown that forest plants can take up some forms of organic nitrogen directly, without preliminary mineralisation (Nsholm et al., 1998).Amino acids and amino sugars appear to be the most important organic sources of nitrogen for plants, including Norway spruce (Picea abies (L.) Karst.) (Johnsson et al., 1999). Organic nitrogen occurs in different forms. In soils, the most important are heterocyclic compounds and amino acids (35 % and 40 % respectively, Schulten and Schnitzer, 1998). In soil waters, amino sugars may also be important (Michalzik and Matzner, 1999).At present, organic nitrogen is normally determined as the difference between total nitrogen and the sum of nitrogen in nitrate and ammonium. This is not entirely satisfactory, as there will be a certain amount of uncertainty in each of the three determinations required. The total uncertainty involved in the determination of organic nitrogen may then be quite large compared to the actual concentration, especially when most nitrogen is present as inorganic nitrogen.A method for the direct determination of organic nitrogen is therefore desirable. Because organic nitrogen generally has a higher molecular weight than inorganic nitrogen, it might be possible to separate organic from inorganic nitrogen using size fractionation methods. In 1998, we worked on the setting up of methods for the determination of amino acids and amino sugars in soil waters, and on the direct determination of organic nitrogen using equilibrium dialysis.
Authors
V.R. Nsolomo Halvor Solheim Kåre Olav VennAbstract
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Authors
Erik Christiansen Alan A. Berryman Vincent R. Franceschi Trygve Krekling Paal Krokene Nina Elisabeth Nagy Halvor SolheimAbstract
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Staffan Jacobson Mikko Kukkola E. Mälkönen Bjørn TveiteAbstract
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Authors
Oddvar SkreAbstract
Forsøk viser at mørkerespirasjonen i veksande skot av norsk gran (Picea abies (L.)Karst.) har samanheng med den daglege veksten. Liknande samanhengar er funne i bladskiver av bjørk (Betula pubescens Ehrh.) og alm (Ulmus glabra var. scabra Huds.). Årleg akkumulert respirasjon viser korrelasjon med utbreiingsgrensene til desse treslaga. Det er venta at klimaendringa på langt sikt vil føra til at tregrensene for dei undersøkte treslaga vil stiga med 400 m. Forsøk med bjørk viser at dette treslaget har eit stort potensial for temperaturtilpassing ved ulike kompensasjonsmekanismar.
Abstract
Measurement data on air, precipitation and canopy throughfall chemistry from a network of sites have been combined to study scavenging and deposition processes, with particular emphasis on the oxidised nitrogen species.High deposition rates of oxidised nitrogen occur in coastal areas of SW Norway. These are partly caused by high precipitation rates, partly also because a large fraction of the oxidised nitrogen is present as nitrate in large particles, which are rapidly removed by both wet and dry deposition processes.High wind speeds near the coast result in high concentrations of sea-salt particles in the air and high deposition rates of both nitrate and sea-salt particles, particularly in coniferous forest stands. HNO3 contributes on average only about 10-20% to the sum of aerosol nitrate and HNO3 (sNO(3)). Still, the combined dry deposition velocity of sNO(3) to these forest stands may be between 4 and 6 cm s(-1) on average.