Increased nitrogen in runoff and soil following 13 years of experimentally increased nitrogen deposition to a coniferous-forested catchment at Gårdsjön, Sweden.
Beginning in 1991, we have added nitrogen (N) to the 0.5-ha, N-poor, coniferous-forested catchment G2 NITREX at Gårdsjön, 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 microeq 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 Gårdsjön demonstrate that increased leaching of inorganic N and decrease in C/N ratio respond to increased N deposition at greatly different time scales.
Moldan
F
F
IVL Swedish Environmental Research Institute, Box 5302, SE-400 14 Gothenburg, Sweden. filip.moldan@ivl.se
Kjønaas
O J
OJ
Stuanes
A O
AO
Wright
R F
RF
D000327:Adsorption; D004787:Environmental Pollution / Q000009:adverse effects*; D016468:Forestry; D009573:Nitrites / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D028223:Pinus / Q000502:physiology*; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012987:Soil / Q000032:analysis; D012989:Soil Pollutants / Q000032:analysis*; D013548:Sweden; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D012987:Soil; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; D009584:Nitrogen