Affecting factors on the concentration and amount of forest run-off waterchemicals.

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1. Vertical distribution of waterchemicals in a forest ecosystem.Precipitation, forest throughfall, a litter layer, 5, 10, 20, 30, 50, 70 cm soil layers, and stream run-off water were collected vertically 2-4 times per month, and the waterchemicals therein were studied. Plastic pipes with an inside diameter of 19.5cm were inserted vertically into each soil layer to collect the water samples. The concentration of each mineral in the precipitation increased in the throughfall. While infiltrating through each soil layer, the concentration of NH_4-N, organic-N, P, K, Cl, So_4 decreased. On the other hand, NO_3-N, Ca, and Mg increased in each soil layer and reached a maximum at around 70cm in depth.2. Seasonal change of waterchemicals in precipitation and stream run-off water.Na and Cl in precipitation increased in the winter due to sea salt which wascarried by the north-west monsonn. The increase of Cl affected the concentration in stream water. NO_3-N in stream water incresed from April with the increase of biochemical activity in the soil, reaching a maximum late in the autumn. After the decrease in winter, it was flushed again during the snow melting season. SO_4, Ca, Mg in stream water tended to decrease in the summer when run-off water increased. Seasonal change was not detected in pH, SiO_2, NH_4-N, org-N, or Na.3. Change of the concentration of waterchemicals in floodwater.NO_3-N concentration in stream water increased with the increase in run-off water and reached a maximum when run-off water reached a maximum, and decreased with the decrease in water. Na, Mg, and SO_4 tended to decrease with the increase in water. The change of Cl depended on the season of floods, and those of Ca and K depended on the watersheds.