Understanding the seasonal and regional patterns of nitrogen (N) components in the headwaters of forested watersheds is important for forests management. Here, we investigated the NO 3 -N concentration and its seasonal variations in the baseflow headwaters in Japanese coniferous forests with different N saturation status in five regions (i.e., Nagano, Tokyo, Aichi, Kochi and Mie). We found that the ratios of NO 3 -N to DON were significantly higher in the N-saturated regions including Nagano (14.1±2.2) and Tokyo (16.5±4.1), compared with the regions, which didn't experience N saturation including Aichi (1.4±0.2), Kochi (5.1±1.8), and Mie (2.2±0.5). In comparison with the regions without experiencing N saturation, the relatively higher NO 3 -N concentration, as well as its contrastive variation between growing season and dormant season, was also characteristic of the seasonal NO 3 -N concentration in the N-saturated regions. Our findings have indicated that NO 3 -N concentration, its seasonal variations, and the ratio of NO 3 -N to DON, are the better and applicable indicators for evaluating N saturation status in Japanese coniferous forests.