Abstract
Dissolved matter concentrations of bulk precipitation, throughfall, stem flow, soil water, and stream water were investigated in two small forested watersheds consisting of sugi (Cryptomeria japonica) and hinoki (Chamaecyparis obtusa) trees, in Gunma Prefecture, 100km northwest of Tokyo. Processes of the changes in water chemistry were examined. Concentrations of nearly all kinds of dissolved matter in surface soil water apparently were affected by soil moisture, mineralization and nitrification, anion exchange capacity, throughfall chemistry and so on. Concentrations of Na+, HCO3-, and SiO2 and pH in subsurface soil water appeared to be affected by chemical weathering following an increase in CO2 from soil respiration. Soil respiration apparently also affected on concentrations of K+ and HCO3- in stream water. NO3- concentrations in stream water were affected by NO3- concentrations in subsurface soil water besides stream discharge. Concentrations of nearly all kinds of dissolved matter, except for NH4+ and H+, increases from bulk precipitation to stream water through the forest ecosystems. These increases in concentrations apparently were affected by the processes of evapotranspiration, leaching from trees, mineralization and nitrification, chemical weathering by soil respiration and so on.
