『Abstract
　Nitrogen (N) biogeochemistry of a mature Scots pine (Pinus sylvestris L.) stand subjected to an average total atmospheric N deposition of 48 kg ha^-1 year^-1 was studied during the period 1992-2007. The annual amount of dissolved inorganic nitrogen (DIN) in throughfall (TF) averaged 34 kg ha^-1 year^-1 over the 16-year monitoring period. The throughfall fluxes contained also considerable amounts of dissolved organic nitrogen (DON) (5-8.5 kg N ha^-1 year^-1), which should be incorporated in the estimate of N flux using throughfall collectors. Throughfall DIN fluxes declined at a rate of -0.9 kg N ha^-1 year^-1, mainly due to the decreasing TF fluxes of ammonium (NH4), which accounted for 70％ to TF DIN. The decrease in TF DIN was accompanied by a decrease in DIN leaching in the seepage water (-1.6 kg N ha^-1 year^-1), which occurred exclusively as nitrate (NO3^-). Nitrate losses in the leachate of the forest floor (LFH) equalled the TF NO3^- delivered to the LFH-layer. On the contrary, about half of the TF NH4⁺ was retained within the LFH-layer. Approximately 60％ of the TF DIN fluxes were leached indicating that N inputs were far in excess of the N requirements of the forest. For DON, losses were only substantial from the LFH-layer, but no DON was leached in the seepage water. Despite the high N losses through nitrate leaching and NOx emission, the forest was still accumulating N, especially in the aggrading LFH-layer. The forest stand, on the contrary, was found to be a poor N sink.

Keywords: Ammonium; Dry deposition; Dissolved organic nitrogen; Forest floor; Nitrogen retention; Nitrogen cycling; Nitrate leaching; Throughfall』

Introduction
Material and methods
　Site description
　Nitrogen fluxes and pools
　　Air
　　Water
　　Soil
　　Plant biomass
　Calculations and statistical analysis
Results
　Atmospheric nitrogen deposition: total deposition versus throughfall
　Trends of DIN in throughfall, forest floor leachate and soil seepage 1992-2007
　Seasonality of total dissolved N in throughfall, forest floor leachate and soil seepage
　Above-canopy losses of NOx 1996-2007
　Nitrogen pools and change in N storage
　Nitrogen fluxes involved in net primary production and returned via litterfall
Discussion
　Total nitrogen deposition versus throughfall nitrogen: impact of canopy processes
　Drivers of inorganic nitrogen leaching
　Features of inorganic nitrogen retention: role of N form and season
　NOx emissions
　Forest response to declining inorganic nitrogen depositions
　Nitrogen pools and sinks in the ecosystem
Conclusions
Acknowledgments
References