Increased nitrogen in runoff and soil following 13 years of experimentally increased nitrogen deposition to a coniferous-forested catchment at Gardsjon, Sweden

摘要

Beginning in 1991, we have added nitrogen (N) to the 0.5-ha, N-poor, coniferous-forested catchment G2 NITREX at G (a) over circle rdson, Sweden, to investigate the consequences of chronic elevated N deposition. We have added 40 kg N ha(-1) yr(-1) in fortnightly doses of NH4NO3 to the ambient 15 kg N ha(-1) yr(-1) by means of a sprinkling system. NO3 concentrations in runoff increased during 13 years from < 1 to 70 mu eq L-1, and in 2004 comprised about 10% of N input. Inhibition of NO3 immobilisation due to increased availability of NH4 might explain the increased leaching of NO3. C and N pools in the forest floor increased but C/N ratio has not changed. The increase in NO3 leaching thus occurred independently of change in C/N ratio. The results from G (a) over circle rdsjon demonstrate that increased leaching of inorganic N and decrease in C/N ratio respond to increased N deposition at greatly different time scales. (c) 2006 Elsevier Ltd. All rights reserved.