Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
1998
Forfattere
Rolf NestbySammendrag
Det er ikke registrert sammendrag
Forfattere
Leiv MortensenSammendrag
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Forfattere
Leiv Mortensen T. FjeldSammendrag
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Forfattere
Hugh RileySammendrag
A tillage trial was performed on morainic loam soil in south-east Norway over the years 1985-97. Two times of moulboar
Forfattere
Leiv MortensenSammendrag
Det er ikke registrert sammendrag
Forfattere
Trygve S. Aamlid D. ArntsenSammendrag
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Sammendrag
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Sammendrag
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Forfattere
O. Janne Kjønaas Arne Olav Stuanes Magne HuseSammendrag
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.
Sammendrag
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