Abstract
The hydrochemistry of the Tsukuba experimental forest (67.5ha) has been observed since 1985, including rainfall, throughfall, stemflow, soilwater, groundwater and streamwater. The annual water input by rainfall and output by streamwater averaged during 7-year water cycles were estimated to be 1656mm and 849.7mm, which gives the rainwater runoff rate to be 51.3%.
As to the streamsolute, the nitrate concentration tended to be raised with increasing streamwater discharge and temperature in summer season every year, and such coincidence in the rise of concentration and discharge produces a large amount of runoff loading in summer. Contrary to this, the dissolved silicate of streamwater reduced the concentration in summer. The difference between both streamsolute behaviors is reasoned to be driven by the runoff of soilwater, which keeps the nitrate. concentration higher and the silicate lower near surface due to the element cycle in the forest ecosystem.
