Monitoring the chemistry of rainwater and streamwater from a small forested watershed: Results in the Kamabuchi experimental watershed, Yamagata prefecture, Tohoku district, Japan between 2000 and 2014

Abstract

The Kamabuchi experimental watershed, which is located alongside the sea of Japan in the Tohoku district, northern Japan, receives considerable amount of snowfall in winter. We reported the mean annual solute concentrations of the rainwater and streamwater obtained between 2000 and 2014 in a small, forested watershed of this experimental watershed. The area of this watershed was 3.06 ha, and the vegetation was a mixed forest of deciduous and evergreen species. The mean annual NO₃⁻ and SO₄²⁻ concentrations in rainwater showed no trend. The mean annual dissolved inorganic nitrogen input through rainwater was 12.4 kg ha⁻¹ yr⁻¹, about 60% of which was in the form of NO₃⁻-N. SO₄²⁻ input was 63.0 kg ha⁻¹ yr⁻¹, and about two third of that was the non-sea salt SO₄²⁻ input. Annual NO₃⁻-N and SO₄²⁻ input had a positive correlation with the annual precipitation, suggesting that the loads of these inputs were mostly dependent on the amount of precipitation rather than the concentrations. There was a fluctuation in the mean annual NO₃⁻ concentration in streamwater, but an obvious annual change was not recognized. A change was not observed in the mean annual SO₄²⁻ concentrations in streamwater.