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.
1998
Authors
Per Gundersen Bridget A. Emmett O. Janne Kjønaas Chris J. Koopmans Albert TietemaAbstract
Impact of nitrogen (N) deposition was studied by comparing N fluxes, N concentrations and N pool sizes in vegetation and soil in five coniferous forest stands at the NITREX sites: Grdsjn (GD), Sweden, Klosterhede (KH), Denmark, Aber (AB), Wales, UK, Speuld (SP), the Netherlands, and Ysselsteyn (YS), the Netherlands. The sites span a N- deposition gradient from 13 to 59 kg N ha-1 yr-1. Measurements of soil N transformation rates by laboratory and field incubations were part of the site comparison. Further, results from 4-5 yr of NH4NO3 addition (35 kg N ha-1 yr-1) at low deposition sites (GD, KH, AB) and 6 yr of N removal (roofs) at high deposition sites (SP, YS) were included in the analysis. Significant correlations were found between a range of variables including N concentrations in foliage and litter, soil N transformation rates and forest floor characteristics. Using the methods from principal component analysis (PCA) these variables were summarized to an index of site N status that assigned the lowest N status to GD and the highest to YS. Site N status increased with N deposition with the exception that AB was naturally rich in N. Nitrate leaching was significantly correlated with N status but not correlated with N deposition.Forest floor mass and root biomass decreased with increased N status. Characteristics of the mineral soil were not correlated with vegetation and forest floor variables. High C/N ratios in the mineral soil at the high-N deposition sites (SP, YS) suggest that the mineral soil pool changes slowly and need not change for N saturation to occur. Nitrogen transformation rates measured in laboratory incubations did not agree well with rates measured in the field except for a good correlation between gross mineralization in the laboratory and net mineralization in the field. The changes in N concentrations and fluxes after manipulation of N input followed the direction expected from the site comparison: increases at N addition and decreases at N removal sites. Nitrate leaching responded within the first year of treatment at all sites, whereas responses in vegetation and soil were delayed. Changes in N status by the manipulation treatments were small compared to the differences between sites. Changes in nitrate leaching were small at the low-N status sites and substantial at the high-N status sites. Nitrogen-limited and N-saturated forest ecosystems could be characterized quantitatively.
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Svein Ole BorgenAbstract
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M.J. Latkowska Harald Kvaalen M. AppelgrenAbstract
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M.J. Latkowska Harald Kvaalen M. AppelgrenAbstract
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Bengt Ehnström Erkki Annila Øystein Austarå Susanne Harding Jon Gunnar OttossonAbstract
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Authors
Åshild Ergon Sonja Klemsdal Anne Marte TronsmoAbstract
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