Carbon source of humic substances in some Japanese volcanic ash soils determined by carbon stable isotopic ratio, δ13C
Carbon source of humic substances in some Japanese volcanic ash soils determined by carbon stable isotopic ratio, δ13C
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DOI：
10.1016/s0016-7061(03)00257-x
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发表时间：
2004-03
期刊：
影响因子：
6.1
通讯作者：
S. Hiradate;T. Nakadai;H. Shindo;T. Yoneyama
中科院分区：
文献类型：
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作者：
S. Hiradate;T. Nakadai;H. Shindo;T. Yoneyama
众所周知，火山灰土壤（包括安迪土）会在其厚厚的地表中积累极大量的腐殖酸，其积累机制令人感兴趣。提出了两种机制：（1）风化火山物质中的铝和铁等活性金属通过络合反应稳定腐殖酸； (2)栽培的芒草(Miscanthus sinensis A.)及其烧焦物是腐殖酸的主要碳源。在本研究中，通过测量潘帕斯草（C4植物）的碳稳定同位素比（δ13C）来确定腐植酸碳的贡献率。在日本火山灰土壤中，腐殖酸来源于C3和C4植物，C4植物（主要是蒲苇）的贡献比例为18%至52%。尽管大部分碳来自于C3植物，但高度腐殖化（深色）的腐植酸在火山灰土壤中往往表现出较高的C4植物贡献率。还阐明了原始土壤样品的 δ13C 值与腐殖酸和黄腐酸的 δ13C 值具有良好的相关性。因此，文献中报道的原始土壤样品的 δ13C 值将有助于估计土壤腐殖质的碳源。对原始土壤样品δ13C值的文献调查也表明，腐殖质中的大部分碳来源于C3植物而不是C4植物，这表明活性金属（如Al和Fe）对火山灰土壤中腐殖酸的形成和积累的重要性。
Volcanic ash soils (including Andisols) have been known to accumulate extremely large amounts of humic acids in their thick surface horizons, and their accumulation mechanism is of interest. Two mechanisms have been proposed: (1) active metals like Al and Fe, supplied from weathered volcanic materials, stabilize humic acids through complexation reactions; (2) cultivated Japanese pampas grasses (Miscanthus sinensis A.) and its charred materials are the major carbon source of humic acids. In the present study, contribution ratio of the pampas grass (C4-plant) on the carbons of the humic acids was determined by measuring their stable isotopic ratio of carbon (δ13C). In Japanese volcanic ash soils, humic acids were originated from both C3- and C4-plants, and the contribution ratio of C4-plants (mostly pampas grass) ranged from 18% to 52%. Highly humified (dark-colored) humic acids tended to show higher contribution ratio of C4-plants among volcanic ash soils, although the major part of the carbon had originated from C3-plants. It was also clarified that the δ13C values of crude soil samples correlated well with those of humic and fulvic acids. Therefore, reported δ13C values of crude soil samples in the literature would be useful for estimating the carbon source of soil humic substances. Literature survey of the δ13C values of crude soil samples also indicated that a large part of the carbon in humic substances has originated from C3-plants rather than C4-plants, implying the importance of the active metals (such as Al and Fe) on the formation and accumulation of the humic acids in volcanic ash soils.