Modelling stream and soil water nitrate dynamics during experimentally increased nitrogen deposition in a coniferous forest catchment at Gårdsjön, Sweden

摘要

Increased atmospheric deposition of inorganic nitrogen (N) may lead to increased leaching ofnnitrate (NO2n3 ) to surface waters. The mechanisms responsible for, and controls on, this leachingnare matters of debate. An experimental N addition has been conducted at Ga ˚ rdsjo ¨ n, Sweden tondetermine the magnitude and identify the mechanisms of N leaching from forested catchmentsnwithin the EU funded project NITREX. The ability of INCA-N, a simple process-based model ofncatchment N dynamics, to simulate catchment-scale inorganic N dynamics in soil and streamnwater during the course of the experimental addition is evaluated. Simulations were performednfor 1990–2002. Experimental N addition began in 1991. INCA-N was able to successfullynreproduce stream and soil water dynamics before and during the experiment. While INCA-N didnnot correctly simulate the lag between the start of N addition and NO2n3 breakthrough, the modelnwas able to simulate the state change resulting from increased N deposition. Sensitivity analysisnshowed that model behaviour was controlled primarily by parameters related to hydrology andnvegetation dynamics and secondarily by in-soil processes.