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
J.F.G. Lancho J.A.E. Rodriguez M.I.G. Hernandez C.Q. Gonzalo A.V. Esteban F.I. SanchezAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Dag FjeldAbstract
No abstract has been registered
Abstract
Changes in the ectomycorrhizal fungus flora were studied in connection with nitrogen addition and removal experiments in a Norway spruce forest at Gårdsjön, W Sweden during a 5-year period. The above-ground ectomycorrhizal fruit body production was recorded from permanent transect plots, and the below-ground mycorrhizal fine-roots density and morphotype differentiation were studied from soil core samples from the surface root layer. The experiments were performed by adding N-enriched and N-free water, respectively, by means of sprinkling systems. Ammonium nitrate (about 35 kg N ha−1 yr−1) was added to catchment G2 NITREX, whereas at adjacent catchment G1 ROOF ambient N deposition was removed by means of a roof. The addition of N led to a rapid and substantial decrease in species diversity and fruit body production of most species in the NITREX catchment, representing one of very few biological responses to the treatments at Gårdsjön. Stress-intolerant groups such as the initially-dominant genus Cortinarius were almost absent after 5 yr of N addition. Only one dominant species (Cantharellus tubaeformis) increased fruit body production after treatment. In the nitrogen removal (G1 ROOF) experiment, the fruit body production increased strongly the first years, but then declined. No response in the below-ground mycorrhiza and fine-root density and diversity was found. All fine roots had developed ectomycorrhiza. The difference in response above ground and below ground indicates that: (1) the fruit-body producing macrofungi play a minor role below ground, and that (2) there is probably a considerable time-lag in the mycorrhizal fine-root versus fruit body production response to enhanced N levels.
Authors
Bernt Olav Hoel Knut Asbjørn SolhaugAbstract
No abstract has been registered
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Authors
O. Janne Kjønaas Arne Olav Stuanes Magne HuseAbstract
In spite of nitrogen being a major limiting factor for forest growth in most parts of Scandinavia, increased nitrate levels in surface waters and soil water have been coupled to questions of increased inputs and decreasing immobilization of nitrogen in watersheds. To study an ecosystem response to elevated nitrogen deposition, NH4NO3 was added to a 0.52 ha forested headwater catchment in weekly portions by means of sprinklers below the canopy. Total nitrogen input as throughfall increased from the ambient 11 kg N ha-1 yr-1 to approximately 51 kg ha-1 yr-1 in the treatment years. The catchment, situated in Grdsjn, Sweden, is dominated by naturally generated Norway spruce with Scots pine in drier areas. The mean age of the forest is 104 yr. N concentrations in foliage, weight and N concentrations in litterfall, in situ net N mineralization and nitrate transformation (resin core technique), and leaching of N below the organic LFH horizon were studied on a catchment (NITREX) or plot (NITREX, CONTROL) level. This was coupled with input-output budgets to estimate fluxes and cycling of N during the pre-treatment year and the third year of treatment. There was a significant increase in net N mineralization in the NITREX plots the 3rd year of treatment, and a significant interaction between plot and year indicating a response to N addition for both net mineralization and nitrate transformation. The increased flux of nitrate from incubated soil cores, as well as the increased concentration in soil water and runoff indicated that the increased nitrification was possibly coupled with a preferential uptake of NH4---N by the microflora. The spatial variability of the nitrogen transformation rates was generally large and increased with treatment. The N concentration in needle litter showed an increase the 5th year of treatment, but no effect of nitrogen addition was found on the total weight of litterfall or on the N concentration of foliage. The key processes that determine the ecosystem response to increased inputs of nitrogen seem to be net mineralization and nitrogen transformation rates, together with the mechanism and capacity of N assimilation into the soil pool. The major sink for both externally added and internally produced inorganic N was calculated to be the soil organic pool. N assimilation into the upper organic LF horizon dominated, and this assimilation is the first of three suggested ways for coniferous ecosystems to respond to increased chronic N input.Over time, the system is hypothesized to change towards a system with a reduced assimilation capacity, a possible decreased decomposition rate, and an increased export of nitrate through leaching. The time-span of these changes is still uncertain.
Authors
Lars Sandved DalenAbstract
No abstract has been registered
Authors
Tore VikAbstract
No abstract has been registered
Authors
Peter Botterveg Rodney Leek Eirik Romstad Arild VatnAbstract
It is generally accepted that changes in agricultural management during the last decades have had negative effects in the forms of increased erosion and nutrient losses. In our analysis farmers are assumed to maximize expected profits. Economic incentives or direct regulations of agronomic practices may be used to change the farmers' management into a direction that will reduce the losses of nutrients and erosion. In an interdisciplinary research project with economists and ecologists, the effect of different policy measureson erosion and nutrient losses has been analysed. Policy measures analysed were, among others, catch crop requirements and subsidies for spring ploughing instead of autumn ploughing. First, an economic decision making model was ran for farms for a period of 20 years. The model decides the agronomic practice for each year on the different fields for a set of model farms. With the newly developed erosion model, the European soil erosion model (EUROSEM), the effect of the different agricultural practices were analysednot only at the level of single model farms, but also at the landscape level by use of a terrain model. The paper discusses