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
Tore VikAbstract
No abstract has been registered
Authors
Harald Kvaalen Halvor SolheimAbstract
No abstract has been registered
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
Bjørn ØklandAbstract
A short survey shows a lack of continuity in research on the dipteran family Milichiidae in Norway. One common species has several records from the last century, while little else is found before recent time and the new material presented in this article. The number of Norwegian species in Milichiidae is hereby raised to five, and in addition one possible new species. Comparisons with species numbers in neighbouring countries give an indication that still new species for Norway may be found. Rearing habitats for Neophyllomyza acyglossa (Villeneuve, 1920) and the possible new species Leptometopa sp. are presented for the first time.
Authors
Knut Rydgren Rune Halvorsen Økland Tonje ØklandAbstract
No abstract has been registered
Authors
Lars Sandved DalenAbstract
No abstract has been registered
Abstract
Concentrations of pigments in needles of yellowish Norway spruce (Picea abies (L.) Karst.) trees suffering from either N, Mg or K deficiency in field sites in southeast Norway are reported. The yellowish trees had a considerably lower (roughly 50%) pigment concentration, as well as a lower chlorophyll/carotenoid ratio, compared to the green trees within the same sites. Yellowing was interpreted as a general bleaching of colour, as well as a slight turn from the green (chlorophylls) towards yellow (lutein). Concentrations of pigments were highly intercorrelated. N deficiency was especially associated with low a-carotene concentrations. This was interpreted as a-carotene being the most sensitive pigment to stress. However, this pigment might be specifically sensitive to N deficiency. Carbohydrate concentrations were slightly higher in yellowish trees.
Authors
Arne Olav Stuanes Magne Huse O. Janne Kjønaas Per Holm NygaardAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
D. Berggren Jan Mulder R. WesterhofAbstract
No abstract has been registered