酸性降下物に対する土壌緩衝能の実態と評価(<シンポジウム特集>酸性雨と森林衰退,研究の現場から)

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The effects of acid rain on forest ecosystem could be analyzed in relation to forest structure and nutrient cycling. Canopy and trunk show some buffer capacities to acid rain before rain water arrive to soil surface. Soil chemically, clay and soil organic matter have strong buffer capacities. By experimental analysis using soil column and artificial acid rain, soil show having four steps of buffer reaction; i. e. carbonate at pH 6, volcanic ash or salt adsorption at pH 6, cation exchange at pH 5, and aluminum at pH 4. To estimate soil buffer capacity, anion exchange capapcity are to be added with cation exchange capapcity. Volcanic ash soils which contain plenty of allophane have strong buffer capapcity. Once cations become deficient to anion in soil solution, aluminum start elution and decreasing pH. As in soil solution, concentrations of cation and anion are strictly balanced. Although surface soils are thought to have strong capacity, these are weaker than deeper ones in the most of forest soils. Acidic soils which widely distributed in Japanese forests can be calculated very weak against acid rain. In evaluation of effects of acid rain to soil ecosystem, other factors of acidification should be considered. pH of through fall always higher and plenty of nutrients are contained than in rain water. Carbon dioxide and organic acid which are produced by microbial decomposition are not negligible in forest soils. Mycorrhyzae formation and nutrient absorption by root accelerate acidification. Nitrification after ammonification show clear fell in soil pH. Maturing of plantation forest means surface soil acidification. And most tree species are strongly resistant to aluminum and low pH. Further ecological analysis and long term monitoring are necessary for the accurate evaluation.
森林立地学会の論文
1992-06-30

酸性降下物に対する土壌緩衝能の実態と評価(<シンポジウム特集>酸性雨と森林衰退,研究の現場から)

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