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 (484KB)
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46,396,000Yen (FY1998; 15,252,000 Yen)
To develop methods for evaluating the effects of environmental acidic substances on forest ecosystems in east Asia, we investigated following subjects. 1) to observation of acid precipitation and forest conditions in China and Korea, and to compare elements budgets between forested catchments of Japan and Korea. 3) to investigate growth characteristics of Asian forest tree species on artificially acidifying soils conditions. 4) to determine nitrification rates of various types of soil and forest, and also to determine the effect of organic acids on soil acid buffering capacity.
Monitoring study on input and output budget of acidic substances in a small catchment under red pine forest has been carried out in Hachioji of Japan from July of 1996 to October of 1998 and in Chunchon of Korea from May to December of 1997 and from April to October of 1998. "Acid precipitation" and the accumulation of acidic substances were found in the Hachioji catchment. Although acid precipitation was not found in the Chunchon catchment, large amount of output of bases through the stream from soils and the accumulation of acidic substances were shown, resulting in the acidification of the whole catchment.
For tree growth on acidic soil, it is concluded that (1) Al dissolved into soil solution is an important limiting factor for growth and nutrient status of red pine and masson pine seedlings grown in acidic soil, (2) the (Ca+Mg+K)/AI molar ratio in soil solution is a useful indicator to evaluate and predict the effects of soil acidification due to acid deposition on Asian forest tree species at the present time and in the future, and (3) red pine is relatively sensitive to a reduction in the (Ca+Mg+K)/AI molar ratio in soil solution compared with masson pine and European tree species such as Norway spruce (Picea abies L.).
Soil nitrogen mineralization rates varied among soil and forest conditions. Although Sugi (Cryptomeria japonica) stands usually showed higher nitrification rates than Hinoki (Chamaecyparis obtusa) stands, controlling factor for determining nitrification rate is mainly determined by soil chemical properties like exchangeable cations. Oxalic acid also affects soil acidity such that Al became soluble even though soil pH did not decrease. It is necessary to consider these acidic sources for developing a critical load model.
Nutrient balances, Tree sensitivity for acidic soil, Nitrification, Korea, China