『Abstract
　This study evaluated the sources, sinks, and factors controlling net export of nitrogen (N) from watersheds on the west coast of the US. We calculated input of new N to 22 watersheds for 1992 and 2002. 1992 inputs ranged from 541 to 11,644 kg N km^-2 year^-1, with an overall area-weighted average of 1,870 kg N km^-2 year^-1. In 2002, the range of inputs was 490-10,875 kg N km^-2 year^-1, averaging 2,158 kg N km^-2 year^-1. Fertilizer was the most important source of new N, averaging 956 (1992) and 1,073 kg N km^-2 year^-1 (2002). Atmospheric deposition was the next most important input, averaging 833 (1992) and 717 kg N km^-2 year^-1 (2002), followed by biological N fixation in agricultural lands. Riverine N export, calculated based on measurements taken at the furthest downstream USGS water quality monitoring station, averaged 165 (1992) and 196 kg N km^-2 year^-1 (2002), although data were available for only 7 watersheds at the latter time point. Downstream riverine N export was correlated with variations in streamflow (export = 0.94×streamflow−5.65, R² = 0.66), with N inputs explaining an additional 16％ of the variance (export = 1.06×streamflow＋0.06×input−227.78, R² = 0.82). The percentage of N input that is exported averaged 12％. Percent export was also related to streamflow (％export = 0.05×streamflow−2.61, R² = 0.60). The correlations with streamflow are likely a result of its large dynamic range in these systems. However, the processes that control watershed N export are not yet completely understood.

Keywords: Nitrogen budgets; Nutrient inputs; Riverine export; Watersheds; West coast』

Introduction
Methods
　Atmospheric deposition
　Fertilizer
　Net food and feed import
　Biological N fixation
　Other sources and sinks of N
　Total N inputs
　Riverine N export
　Relationship between export and input
Results
　Watershed characteristics
　Inputs
　Export
　Relationship between input and export
Discussion
Acknowledgments
References