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.
1995
Authors
B. Långstrøm Claes Hellqvist Halvor Solheim Rolf Gref François LieutierAbstract
No abstract has been registered
Authors
Dan AamlidAbstract
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Authors
Bjørn ØklandAbstract
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Bjørn ØklandAbstract
No abstract has been registered
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Bjørn ØklandAbstract
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Authors
Arne Olav Stuanes O. Janne Kjønaas Helga van MiegroetAbstract
Nitrogen has been added to a forested 0.52 ha headwater catchment at Gårdsjön on the southwest coast of Sweden to study the ecosystem response to elevated nitrogen deposition. The catchment is dominated by naturally generated, mixed-age conifers, mainly Norway spruce, with Scots pine in dry areas. After a pre-treatment period of about 1 year, nitrogen was added to the whole catchment as ammonium nitrate by means of sprinklers at an intensity of 3 mm h-1 (average concentration 230 mmol N1-1). Total nitrogen input as throughfall to the catchment increased from the ambient 12.5 kg N ha-1 year-1 in the pre-treatment year to a total of 47.3 kg N ha-1 year-1 in the treatment years. Soil solutions were collected using tension lysimeters at four locations covering a moisture gradient from the dry upper to the wet lower parts of the watershed. Results from these locations were compared with soil solution composition at two locations in a nearby control catchment. After 2 years of nitrogen addition, the volume-weighted average nitrate concentrations in the treated catchment were higher than the pretreatment values, especially in the upper soil. Concentrations showed a progressive increase over time. The lack of the same increasing trend in the control catchment precludes natural variations in climatic conditions as the main cause for this increase. Relative to inputs, nitrate concentrations in soil solution were low and showed large variations between the drier and wetter locations. Differences in nitrate concentrations between pre-treatment and treatment periods declined with soil depth, indicating that most of the added nitrogen was consumed in the upper soil. The results from soil solution do not indicate increased nitrogen leaching below the rooting zone in the treated catchment and thus based on these results alone there is as yet no indication of nitrogen saturation.
Authors
Albert Tietema Richard Frederic Wright Kai Blanck M. Bredemeier Bridget A. Emmett Per Gundersen H. Hultberg O. Janne Kjønaas Filip Moldan J.G.M. Roelofs Patrick Schleppi Arne Olav Stuanes N. van BreemenAbstract
In large regions of Europe and eastern North America atmospheric deposition of inorganic nitrogen (N) compounds has greatly increased the natural external supply to forest ecosystems. This leads to N saturation, in which availability of inorganic N is in excess of biological demand and the ecosystem is unable to retain all incoming N. The large-scale experiments of the NITREX project (NITRogen saturation EXperiments) are designed to provide information regarding the patterns and rates of responses of coniferous forest ecosystems to increases in N deposition and the reversibility and recovery of impacted ecosystems following reductions in N deposition.The timing of ecosystem response generally followed a hypothesized cascade of response. In all sites N outputs have responded markedly but to very different degrees within the first three years of treatment. Within this time significant effects on soil processes and on vegetation have only been detected at two sites. This delayed response is explained by the large capacity of the soil system to buffer the increased N supply by microbial immobilization and adsorption. We believe that this concept provides a framework for the evaluation and prediction of the ecosystem response to environmental change.
Authors
Richard Frederic Wright J.G.M. Roelofs M. Bredemeier Kai Blanck Andries W. Boxman Bridget A. Emmett Per Gundersen H. Hultberg O. Janne Kjønaas Filip Moldan Albert Tietema N. van Breemen H.F.G. van DijkAbstract
In large regions of Europe and eastern North America atmospheric deposition of inorganic nitrogen compounds has greatly increased the natural external supply to forest ecosystems. This leads to nitrogen saturation, in which availability of inorganic nitrogen is in excess of biological demand and the ecosystem is unable to retain all incoming nitrogen. The large-scale experiments of the NITREX project (nitrogen saturation experiments) are designed to provide information regarding the patterns and rates of responses of coniferous forest ecosystems to increases in N deposition and the reversibility and recovery of impacted ecosystems following reductions in N deposition. The nitrogen input-output data from the NITREX sites are consistent with the general pattern of nitrogen fluxes from forest ecosystems in Europe. At annual inputs of less than about 10 kg ha-1 year-1, nearly all the nitrogen is retained and outputs are very small. At inputs above about 25 kg ha-1 year-1 outputs are substantial. In the range 10-25 kg ha-1 year-1 these forest ecosystems undergo a transition to nitrogen saturation. The 10 kg ha-1 year-1 apparently represents the minimum threshold for nitrogen saturation.The NITREX experiments indicate that nitrogen outputs respond markedly across the 10-25 kg ha-1 year-1 range of inputs. In contrast, the nutrient concentrations in foliage, a measure of tree response, is delayed by several years. Nitrogen saturation can apparently be induced or reversed within only a few years, at least with respect to the commonly used diagnostic of nitrogen saturation-nitrogen output in leachate or runoff.
Authors
Valentina P. Vetrova Galina G. Polyakova Rida M. Matrenina Natali V. Pashenova Vladimir I. OsipovAbstract
No abstract has been registered