Elemental budgets of forest watershed during snow melting periods from end of March to end of June were determined in a cold snowy region in northern Hokkaido.
The total stream water discharge was 712 mm with a discharge ratio (discharge/precipitation) of 0.78. During the early stage of snow melting Na+, Cl-, Ca2+, Mg2+ and SO42- concentrations in stream water increase remarkably, most likely due to the elements accumulated within the snowpack and surface soil, and decrease with the decrease of stream discharge. On the contrary, bicarbonate concentration decreases, at the beginning of snow melting, due to the dilution effect of the melting water, and gradually increases with the decrease of stream discharge. A Cl/Na ratio, similar to that of seawater suggests a marine origin of Na and Cl. The results from the analysis of element budgets, during the whole snow-melting season, show that: i) inputs of Na+ and Cl- are similar and mostly released from the watershed; ii) inputs of Ca2+, Mg2+ and HCO3- are dramatically smaller than their outputs, indicating that these ions are discharged from the watershed and that the dissociation of the bicarbonate is the major proton source during the melting period. The reaction of mineral weathering and/or ionic exchange of Ca2+ and Mg2+ are major proton sinks with a net leaching of 16 molc ha-1 d-1, as acidification rate of the forest watershed. These findings clearly indicate that the elemental dynamic of forest watershed in cold snowy regions is quite different between the early and late stage of the snow melting process. Moreover, the net fluxes of elemental outputs are closely related to the bicarbonate dynamics within the forest watershed.