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Doctoral thesis, 2002

Nitrogen Turnover in Swedish Spruce Forest Ecosystems : Effects of nitrogen deposition

Andersson, Pål


Nitrate leaching from growing forests is not yet a widespread problem in Sweden, but nitrogen (N) deposition and high N retention in the soil during recent decades might have changed forest ecosystems towards N saturation. In this thesis net N mineralisation (measured with in situ incubations) was tested as an index of N status. It was shown that historic land use and N deposition, natural or simulated in fertilisation experiments, had caused great differences in this index (4-104 kg N ha -1 yr -1 ) and that N leaching occurred at sites with high N status (net N mineralisation > 60 kg N ha -1 yr -1 ). The net N mineralisation was well correlated to C/N ratio, which could also be used as a N status index. The amount of nitrate lost was not dependent on N status or current N deposition, but rather to the total N flux density (deposition + net mineralisation). The relatively fast change (30 years) from a highly N limited ecosystem to a system apparently approaching the first stage of N saturation upon moderate N fertilisation (35 kg N ha -1 yr -1 ) motivates continued concern about N saturation in Sweden. Predicting future response to N deposition and forest management necessitates a thorough understanding of all important N fluxes, but the importance of organic N uptake in Swedish spruce forest ecosystems is still unclear. Budget calculations indicated that uptake of organic N is of great importance (80%) in low input areas. In high N-input plots the relative importance appeared lower (35%). However, soil solution samples from the forest floor contained low concentrations of both amino acids and inorganic N, and the lack of a clear dominance of amino acids might be explained by a tight circulation of amino acids, never releasing the amino acids into the soil solution fraction sampled with tension lysimeters


boreal; ecosystem recovery; fine root longevity; forest soil; mycorhiza; PnET-CN

Published in

Acta Universitatis Agriculturae Sueciae. Agraria
2002, number: 342
ISBN: 91-576-6194-4
Publisher: Swedish University of Agricultural Sciences

Authors' information

Andersson, Pål
Swedish University of Agricultural Sciences, Department of Soil Sciences

UKÄ Subject classification

Soil Science
Forest Science

URI (permanent link to this page)