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
Bridget A. Emmett O. Janne Kjønaas Per Gundersen Chris J. Koopmans Albert Tietema D. SleepSammendrag
Det er ikke registrert sammendrag
Forfattere
Bridget A. Emmett O. Janne Kjønaas Per Gundersen Chris J. Koopmans Albert Tietema D. SleepSammendrag
Chronic atmospheric nitrogen deposition can alter the rate of internal nitrogen cycling and increase the magnitude of N leaching losses in forested ecosystems. As fractionation of nitrogen in favour of the lighter 14N occurs during various transformations associated with N-enrichment and nitrogen loss, it has been proposed that the 15N signal of vegetation may provide a useful tool in evaluating the past and current N status of forested ecosystems. A series of coniferous forests across a European nitrogen deposition gradient within the NITREX project provided an opportunity to test the relationships between nitrogen supply from atmospheric deposition and the relative 15N-enrichment of vegetation to soil, across a large geographical area. Most 15N values for above- and below-ground tree components, soil at four depths, bulk precipitation and/or throughfall water and soil solution or outflow water values were within those observed elsewhere except for a few notable exceptions.There was a significant positive relationship between the 15N enrichment of the tree foliage relative to the soil horizons (or the enrichment factor), and nitrogen flux in the throughfall if Aber forest, N. Wales, was excluded from the regression analysis. An unusually high enrichment factor at the Aber site indicated that a the high rate of N cycling at the site was in excess of that predicted from current N deposition. This was attributed to the effect of ploughing and tree planting on the relatively N- and clay-rich mineral horizons at Aber compared to other sites. Highly significant relationships (P 0.01) between enrichment factors and parameters describing internal rates of N cycling, such as litterfall N flux and nitrification rates in upper soil horizons, supported this conclusion. There appears to be a strong link between the rate of N cycling and the 15N enrichment factor, rather than N deposition or nitrate leaching per se. These results confirm the potential use of the 15N enrichment factor to identify sites influenced by nitrogen deposition. However, consideration should be taken of other site characteristics and land management practises which also influence soil N dynamics and N cycling.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
O. Janne Kjønaas Richard Frederic WrightSammendrag
Chronic deposition of inorganic nitrogen (N) compounds from the atmosphere to forested ecosystems can alter the status of a forest ecosystem from N-limited towards N-rich, which may cause, among other things, increased leaching of inorganic N below the rooting zone. To assess the time aspects of excess N leaching, a process-oriented dynamic model, MERLIN (Model of Ecosystem Retention and Loss of Inorganic Nitrogen), was tested on an N-manipulated catchment at Grdsjn, Sweden (NITREX project). Naturally generated mature Norway spruce dominates the catchment with Scots pine in drier areas. Since 1991, ammonium nitrate (NH4NO3) solution at a rate of about 35 kg N ha-1 yr-1 (250 mmol m-2 yr-1) has been sprinkled weekly, to simulate increased atmospheric N deposition. MERLIN describes C and N cycles, where rates of uptake and cycling between pools are governed by the C/N ratios of plant and soil pools. The model is calibrated through a hindcast period and then used to predict future trends. A major source of uncertainty in model calibration and prediction is the paucity of good historical information on the specific site and stand history over the hindcast period 1930 to 1990. The model is constrained poorly in an N-limited system. The final calibration, therefore, made use of the results from the 6-year N addition experiment. No independent data set was available to provide a test for the model calibration. The model suggests that most N deposition goes to the labile (LOM) and refractory (ROM) organic matter pools. Significant leaching is predicted to start as the C/N ratio in LOM is reduced from the 1990 value of 35 to 28. At ambient deposition levels, the system is capable of retaining virtually all incoming N over the next 50 years. Increased decomposition rates, however, could simulate nitrate leaching losses. The rate and capacity of N assimilation as well as the change in carbon dynamics are keys to ecosystem changes. Because the knowledge of these parameters is currently inadequate, the model has a limited ability to predict N leaching from currently N-limited coniferous forest ecosystems in Scandinavia. The model is a useful tool for bookkeeping of N pools and fluxes, and it is an important contribution to further development of qualitative understanding of forest N cycles.
Forfattere
G. GuttormsenSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Rolf NestbySammendrag
Gjødsling av jordbær med nitrogen i vekstsesongen med gjødsel i dryppvatn gav økte avlinger og større sukkerinnhold i fruktene.
Forfattere
Gustav FystroSammendrag
Det er ikke registrert sammendrag
Forfattere
D Eide Liv OstremSammendrag
Forsøksringane i Sogn og Fjordane gjennomførte i 1997 ein forsøksserie (10 felt) med bruk av ulik mengde nitrogen (0-25 kg N/daa) til gamal eng. Målet med serien var å få betre kjennskap til avlingsnivået i gamal eng, for lettare å kunne gje råd i samband med gjødsling
Forfattere
D Eide Liv OstremSammendrag
Forsøksringane i Sogn og Fjordane gjennomførte i 1997 ein forsøksserie (10 felt) med bruk av ulik mengde nitrogen (0-25 kg N/daa) til gamal eng. Artikkelen omtalar forkvalitet både når det gjeld innhald av energi, protein og mineral