黒色土および褐色森林土腐植の炭素安定同位体分析による給源植物の推定 -八甲田山南山麓における事例- [in Japanese] Contribution of Past C_4 Plants Estimated from δ^<13>C Values of Soil Organic Matter to the Black Soil Genesis in Hakkoda Mountain, Northeast Japan [in Japanese]
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There has been controversy over the pedogenic process of Black soils and Brown forest soils that developed on Quaternary tephras. Stable carbon isotopic technology can provide direct evidence of the process of humus accumulation on these contrasting types of soils.<br>We measured δ<sup>13</sup>C (<sup>13</sup>C/<sup>12</sup>C) humus values of a Black soil and a Brown forest soil, which were thought to have the same parent material, located near Hakkoda, in the northern part of the Tohoku district, Japan. In this region, two marker-tephras are interstratified in the soil profile and make it easy to study the pedogenic process. Soil pollen analysis clarified that non-arboreal pollen mainly consisting of Gramineae was dominant in A and buried A horizons of Black soil. On the other hand, almost all of the pollen detected in the horizons of the Brown forest soil was arboreal. The results implied that the soil organic matter is derived from the degraded remains of these plants.<br>The δ<sup>13</sup>C value was -20∼-18‰ in Black soil and -25∼-22‰ in Brown forest soil. This result suggested that 45∼53% of the organic matter of Black soil derives from C<sub>4</sub> plants, such as <i>Miscanthus sinensis</i> and <i>Imperata cylindrica</i>. This is direct evidence that the grassland vegetation composed of <i>Miscanthus sinensis</i> was an important source of organic matter and continuously provided soil organic matter at least during the past 4, 000 years on Black soil. On the other hands, in Brown forest soil most of the soil organic carbon was derived from C<sub>3</sub> plants, such as <i>Fagus, Pinus</i>, and <i>Quercus</i>.
- The Quat. Res.
The Quat. Res. 38(2), 85-92, 1999-04-01
Japan Association for Quaternary Research