Retention of atmospherically-derived nitrogen in subcatchments of the Bjerkreim River in southwestern Norway

During the period 1993-1995 an extensive study on N inputs and losses to streamwater was carried out in 19 subcatchments of the Bjerkreim river$(685\ {\rm km}^{2})$in southwestern Norway. Total N fluxes in the main river outlet were 8.1-10.7 (mean: 9.8) kg ha-1yr-1. Of this total, about 70% was esti...

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Bibliographic Details
Published in:Ambio 1997-08, Vol.26 (5), p.296-303
Main Authors: Kaste, Oe, Henriksen, A, Hindar, A. (Norsk Inst. for Vannforskning, Oslo (Norway))
Format: Article
Language:English
Subjects:
AIR POLLUTION
Atmospherics
AZOTE
BASSIN VERSANT
BOSQUES
COURS D'EAU
CUENCAS HIDROGRAFICAS
CURSOS DE AGUA
Forest soils
Forested watersheds
FORESTS
FORET
Freshwater
Heathlands
Lakes
LANDE
LEACHING
LESSIVAGE DU SOL
LIXIVIACION
MOORS
Mountain soils
NITROGEN
NITROGENO
NORUEGA
NORVEGE
NORWAY
PARAMOS
POLLUTION ATMOSPHERIQUE
POLUCION DEL AIRE
RIVERS
Subwatersheds
WATERSHEDS
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Summary:During the period 1993-1995 an extensive study on N inputs and losses to streamwater was carried out in 19 subcatchments of the Bjerkreim river$(685\ {\rm km}^{2})$in southwestern Norway. Total N fluxes in the main river outlet were 8.1-10.7 (mean: 9.8) kg ha-1yr-1. Of this total, about 70% was estimated to be of atmospheric origin. Average N fluxes for forested catchments, heathlands, and mountainous catchments were 2.3-4.2; 4.2-5.0; and 6.3-8.7 kg N ha-1yr-1, respectively. Average retention of total N (calculated as$1\text{-}({\rm N}_{\text{out}}/{\rm N}_{\text{in}})$) was 0.75-0.90 in forested catchments, 0.65-0.70 in heathlands, and 0.55-0.70 in mountainous areas. Possible hypotheses for the relatively high N leaching, especially from the mountainous areas in the Bjerkreim catchment, may be: (i) low N-uptake capacity due to shallow soils, sparse vegetation and short growing season; (ii) N loss during hydrologic events; and (iii) limitation of vegetation growth by other factors than N (e.g. P). In southern Norway, which is dominated by nonforested and mountainous areas, leaching of NO3 -is probably a widespread phenomenon leading to increased acidification and altered nutrient balance in the aquatic environment.
ISSN:0044-7447
1654-7209