都城盆地の累積性黒ボク土における炭素・窒素安定同位体自然存在比の変遷　　植物珪酸体による植生変遷との対応

DOI Web Site 被引用文献11件 参考文献48件

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タイトル別名
  • Variations in Natural Abundance of Stable Carbon and Nitrogen Isotopes in a Cumulative Andisol in Miyakonojo Basin, Southern Kyushu, with Reference to Vegetation Changes from Phytolith.
  • ミヤコノジョウ ボンチ ノ ルイセキセイ クロ ボクド ニ オケル タンソ チッソ アンテイ ドウイタイ シゼン ソンザイヒ ノ ヘンセン ショクブツ ケイサンタイ ニ ヨル ショクセイ ヘンセン ト ノ タイオウ
  • 植物珪酸体による植生変遷との対応

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The stable carbon and nitrogen isotopes were investigated in successive samples of a cumulative Andisol in Miyakonojo basin. The biggest difference of δ13C values among the group of horizons was 2.6‰ in the Mi-ike tephra (horizon 3C; Sample No. 26-24), followed by 1.6‰ in Kuroniga (buried humic horizon 2A; No. 16-10) above the Mi-ike tephra and 1.6‰ in horizon 8B2 (No. 64-59) of the lower part of the brown loam layer. The δ13C values showed a tendency to become lower in horizons with high organic carbon content, from humic horizon 8A1 existing with the Satsuma tephra up to the surface horizon (1Ap).<br>The percentages of C3 and C4 plant-derived carbon in soil organic matter estimated from δ13C values had a relation with those estimated from phytoliths of gramineous plants, although differences in the percentages were observed. Highly positive correlations were observed between the content of C3 plant-derived carbon and the yield of C3 plant (Pleioblastus sect.) estimated from phytolith analysis in horizon 5-4 (R2=0.917) above the Akahoya tephra (ca. 6.5ka) and in horizon 3-2, Kuroniga 4A and 2A (R2=0.806) above the Mi-ike tephra layer (ca. 4.2ka). Consequently, it was inferred that soil organic matter in Kuroniga (4A and 2A) was mainly composed of Pleioblastus sect. (Medake and Nezasa), C3 plants. As higher percentages of C4 plant carbon were recognized in the horizons above the thickly deposited Mi-ike and Akahoya tephra layers, it was inferred that Miscanthus, a pioneer C4 plant, first invaded under conditions of devastation of vegetation. It was also suggested that C4 vegetation, mainly composed of Miscanthus, had been gradually replaced by C3 vegetation mainly composed of Pleioblastus sect. (Medake and Nezasa).<br>Since the δ15N values in the cumulative Andisol, except for some horizons, tend to become high in dry periods and low in wet periods with reference to other proxies, it may be concluded that the δ15N values partly respond to the soil moisture condition due to climatic change. The low δ15N value (minimum; 2.9‰) of sample No. 41, humus horizon 7A/C1 including pumice of the Sueyoshi tephra, suggested the possibility that the accumulation of nitrogen was caused by atmospheric nitrogen fixation.

収録刊行物

  • 第四紀研究

    第四紀研究 40 (4), 307-318, 2001

    日本第四紀学会

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