『Abstract
　Seasonal and diurnal variations of in-stream NO3-N concentration oscillations were studied through high-frequency measurements of stream-water's physical, chemical parameters (in-stream NO3-N concentration, water temperature, dissolved oxygen, pH) and hydrometeorological variables (stream discharge, solar radiation) under hydrologically stable conditions. The study was carried out in 2006, within the 42 km² forested Padez（ｚの頭にv） stream watershed in the southwestern part of Slovenia, which is characterized by distinctive hydrogeological settings (flysch) and climate conditions (transitional area between the Mediterranean and continental climate). Fine temporal data resolution (15-min interval) enabled identification of the factors responsible for seasonal variability in the diurnal pattern of the streamwater NO3-N concentrations versus seasonal and diurnal behavior of meteorological and other water chemistry constituents. The observed seasonal variability of in-stream NO3-N daily oscillations indicates the important role of primary production uptake, particularly during seasons when deciduous vegetation is dormant and light levels in the stream are high. Highest daily NO3-N concentration amplitudes (0.3 mg/l-N) and daily changes in the NO3-N flux (0.4-0.5 g/s-N) were observed in spring; the NO3-N concentration oscillations in summer showed a considerably smaller effect of the in-stream uptake (maximum NO3-N daily concentration amplitude 0.1 mg/l-N; daily change in the NO3-N flux 0.02 g/s-N). Seasonal shifts in the timing of daily maximum (up to 6 h) and minimum NO3-N concentrations (between 1 and 3 h) provided some additional indications of seasonal changes in the in-stream primary production uptake and its relation to the terrestrial component of the forested watershed.

Keywords: Diurnal oscillations; Forested watersheds; High-frequency measurements; Seasonality; Slovenia; In-stream nitrate』

Introduction
Study area
Methods
　Data acquisition
　Time series analysis
Results
　Spatial variations in the streamwater NO3-N concentrations
　Time series of the streamwater chemistry and meteorological conditions
Discussion
　Seasonal pattern of the in-stream NO3-N concentration and implications of N status of the watershed
　Seasonal changes in amplitude of in-stream NO3-N concentration diurnal oscillations
　Seasonal shifts in the timing of daily minimum and maximum streamwater NO3-N concentration
　Terrestrial versus in-stream processing of NO3-N
Conclusions
Acknowledgments
References