『Abstract
　To clarify nitrogen (N) sources, the overall N budget in a forested watershed in Kanagawa Prefecture, Central Japan was estimated by measuring dissolved inorganic N (DIN; NH4⁺ + NO3^- + NO2^-) from Nov 2004 through Oct 2005. The estimated N budget (-1.43 kg N ha^-1 year^-1) showed that the N output rate (stream water N) was higher than the N input rate (bulk deposition N) in the watershed. The annual NO2^-) and NO3^- input rates were 0.02 and 1.99 kg N ha^-1 year^-1, respectively. NH4⁺ was the predominant source in this forested watershed, accounting for 71％ (4.99 kg N ha^-1 year^-1) of DIN input rate. In addition, this study estimated rainfall pH, air temperature, and wind direction, which were considered as controlling factors related to the atmospheric deposition rate of NH4⁺. This study showed that the rainfall NH4⁺ was inversely proportional to the initial pH of the rainfall, which was calculated by adding the amount of H⁺ consumed by the dissociation process of NH3(aq) to the measured rainfall pH. This result implies that acid rain can elevate the solubility of NH3(g) and the dissociation capacity of NH4⁺ throughout the process of precipitation. Also, this study provides strong evidence that the high NH4⁺ deposition rate is mainly derived from NH3(g) emitted from livestock wastes under the NH3 transport condition of warm summer and favorable wind direction.

Keywords: Acid rain; Atmospheric N deposition; Livestock; N sources; Forested watershed; Central Japan』

1. Introduction
2. Materials and methods
　2.1. Site description
　2.2. Experimental design
　2.3. Calculation of nitrogen budget and initial rainfall pH
　2.4. Statistical analyses
3. Results and discussion
　3.1. N budget in the forested watershed
　3.2. NH4⁺ contribution to nitrogen deposition
　3.3. Seasonal variation of NH4⁺ deposition
　3.4. Effect of acid rain on the bulk NH4⁺ deposition
4. Conclusions
Acknowledgments
References