Concentration of Nitrogen in a Forested Headwater Stream in Japan

The balance between nitrogen loading and runoff in the forested headwater streams of the Kanna River was estimated to elucidate the current status of nitrogen saturation in a forested watershed. NO3-N concentration in the study area was far higher than the average value in Japan. Estimated nitrogen runoff accounted for 55–57% of nitrogen loading; suggesting that the forest’s nitrogen retention capacity is most likely in decline. Since the 1970s, Japan’s forestry industry has been declining due to the decrease in lumber demand and increase in cheap imported materials. Thus, this decline will contribute significantly to further reducing nitrogen saturation in forest ecosystems. Keywords—Dissolved inorganic nitrogen species, Forest management, Nitrogen Saturation, Watershed.