Pedological and Plant Nutritional Aspects of Acid Sulfate Soil, and Physiological Responses and Tolerant Screening of Tree Species to Strong Soil Acidity

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In this study, we have clarified the distribution of acid sulfate soils generated not only from Quaternary sediments but also from sedimentary rocks of the Tertiary in Japan. We also found Tertiary rocks containing pyrite (FeS_2), which generates sulfuric acid by oxidation, in East Kalimantan, Indonesia and Narathiwat, Thailand. Acid sulfate soil will be generated from the the pyrite-containing rocks by land development in tropic countries where now only the problem of acid sulfate soils generated from Quaternary sediments is pointed out. Elution of manganese from acid sulfate soils and disorder of planted trees by manganese toxicity were appeared by construction of high way in Ibaraki Prefecture, Japan. In order to plant trees on such acid sulfate soils, the trees is necessary to have tolerant ability to excessive manganese as well as to low pH.In the case of birch tree, which adapts on acidic soils, photosynthetic machinery was damaged by excess manganese. We showed that the tropical leguminous trees, Acacia mangium and Acacia auriculiformis, are adaptable to high manganese and low pH conditions. It suggests that the acacia trees are candidates for reforestation materials of degraded land with strong acidity. We have established the tissue culture system of Acacia mangium and Acacia auriculiformis for tolerant breeding. Using cell culture system of Acacia mangium, we clarified the response of the cells to low pH and excess manganese. Tolerant cell lines have been obtained by continuous culture under low pH and high manganese conditions. We are aiming to clarify the mechanism of tolerance to those stresses and to add tolerant ability to trees for reforestation of degraded land.