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.
2006
Authors
Tiina Kuusela Johanna Witzell Annika NordinAbstract
No abstract has been registered
Authors
L.H. Pardo P.H. Templer C.L. Goodale S. Duke P.M. Groffman M.B. Adams P. Boeckx J. Boggs J. Campbell B. Colman J. Compton Bridget A. Emmett Per Gundersen O. Janne Kjønaas G. Lovett M. Mack A. Magill M. Mbila M.J. Mitchell G. McGee S. McNulty Knute J. Nadelhoffer S. Ollinger D. Ross H. Rueth L. Rustad P. Schaberg S. Schiff Patrick Schleppi J. Spoelstra W. WesselAbstract
N saturation induced by atmospheric N deposition can have serious consequences for forest health in many regions. In order to evaluate whether foliar d15N may be a robust, regional-scale measure of the onset of N saturation in forest ecosystems, we assembled a large dataset on atmospheric N deposition, foliar and root d15N and N concentration, soil C:N, mineralization and nitrification. The dataset included sites in northeastern North America, Colorado, Alaska, southern Chile and Europe. Local drivers of N cycling (net nitrification and mineralization, and forest floor and soil C:N) were more closely coupled with foliar d15N than the regional driver of N deposition. Foliar d15N increased non-linearly with nitrification:mineralization ratio and decreased with forest floor C:N. Foliar d15N was more strongly related to nitrification rates than was foliar N concentration, but concentration was more strongly correlated with N deposition. Root d15N was more tightly coupled to forest floor properties than was foliar d15N. We observed a pattern of decreasing foliar d15N values across the following species: American beech>yellow birch>sugar maple. Other factors that affected foliar d15N included species composition and climate. Relationships between foliar d15N and soil variables were stronger when analyzed on a species by species basis than when many species were lumped. European sites showed distinct patterns of lower foliar d15N, due to the importance of ammonium deposition in this region. Our results suggest that examining d15N values of foliage may improve understanding of how forests respond to the cascading effects of N deposition. Introduction Nitrogen saturation is the process by which chronically elevated N inputs alter forest ecosystems, ultimately resulting in increases in ecosystem N loss (Aber et al. 1989; 1998). N saturation can result in detrimental plant responses and have serious consequences for forest health (Nihlgard 1985; Aber et al. 1989; Schaberg et al. 2002) and may impact forests in many regions (Dise et al. 1998; Aber et al. 2003). Therefore, developing indicators useful for determining whether a forest is at N saturation and for predicting when a forest is nearing N saturation is valuable. Such indicators would facilitate both forest management and understanding of N cycling in forest ecosystems.
Authors
Anders BrynAbstract
No abstract has been registered
Authors
Filip Moldan O. Janne Kjønaas Arne Olav Stuanes Richard Frederic WrightAbstract
Beginning in 1991, we have added nitrogen (N) to the 0.5-ha, N-poor, coniferous-forested catchment G2 NITREX at Gårdsjön, Sweden, to investigate the consequences of chronic elevated N deposition. We have added 40 kg N ha−1 yr−1 in fortnightly doses of NH4NO3 to the ambient 15 kg N ha−1 yr−1 by means of a sprinkling system. NO3 concentrations in runoff increased during 13 years from < 1 to 70 μeq L−1, and in 2004 comprised about 10% of N input. Inhibition of NO3 immobilisation due to increased availability of NH4 might explain the increased leaching of NO3. C and N pools in the forest floor increased but C/N ratio has not changed. The increase in NO3 leaching thus occurred independently of change in C/N ratio. The results from Gårdsjön demonstrate that increased leaching of inorganic N and decrease in C/N ratio respond to increased N deposition at greatly different time scales. NO3 concentrations increased in runoff although the C/N ratio of forest floor has not changed.
Authors
Torstein KvammeAbstract
No abstract has been registered
Authors
Andreas TreuAbstract
No abstract has been registered
Abstract
When using chitosan as an antifungal agent in wood it is important to understand which factors contribute to a higher fixation ratio to optimize the utilization of chitosan, the active component. Small pine samples were impregnated with chitosan solutions varying in molecular weight, concentration, pH, polymerization agent, acid and degree of deacetylation. Different post-treatments such as time, temperature, moisture content and the effect of present air were applied to the samples to evaluate the effect on the relative retention. After impregnation, the samples, with a volume of 1.5 cm3, were leached in separate test-tubes according to EN-84. The samples were prepared in a paired design where both samples were impregnated, but only one was leached. Both leached and unleached samples were analysed for their chitosan content, and the relative ratio was used as a measure for the relative retention of chitosan during leaching. The results from these trials show that pH in the range of 5.1-5.9 is favourable. The molecular weight should be as high as possible yet able to penetrate the wood structure, and the use of acetic acid gives far better fixation than the use of hydrochloric acid.
Authors
Erik LarnøyAbstract
No abstract has been registered
Authors
Toril Drabløs EldhusetAbstract
No abstract has been registered
Abstract
Dissolved aluminium was fractionated in the field and the laboratory using a cation exchange method. Although absolute differences between results obtained from field and laboratory fractionations were generally small, relative differences, expressed as the ratio between labile aluminium determined after laboratory fractionation (Alll) and that obtained after field fractionation (Allf), could be large. The differences found were not statistically significant, although this may simply reflect the spread in the results. Alll/Allf had no apparent relationship with the temperature difference between the field and the lab. Although some significant correlations were found between Alll/Allf and H+, no significant correlations were found with the equivalent relative difference in {H+} between the lab and the field. Neither was any significant correlation found with dissolved organic carbon.