Amino acids and amino sugars as molecular indicators of the origins and alterations of organic matter in buried tephra layers
Amino acids and amino sugars as molecular indicators of the origins and alterations of organic matter in buried tephra layers
复制标题
氨基酸和氨基糖作为埋藏火山灰层中有机质起源和变化的分子指标
DOI：
10.1016/j.geoderma.2020.114449
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发表时间：
2020
期刊：
影响因子：
6.1
通讯作者：
R.
中科院分区：
文献类型：
--
作者：
Hobara;S.;Ogawa;H.;Benner;R.
深层土壤有机碳含量高于表层土壤，深层有机碳平均停留时间较长。相对而言，人们对深层土壤中有机质的退化知之甚少，尤其是在千年的时间尺度上。火山灰沉积有时会掩埋表层土壤，形成富含有机质的深层土壤。为了研究日本北海道地区深层土壤中埋藏有机质的变化和动态，我们对北海道地区数千年时间尺度上沉积的麻风层中常见的生物化学物质——组合氨基酸和氨基糖进行了研究。化学分析表明，特定氨基酸（如亮氨酸和苯丙氨酸）和氨基糖（如葡萄糖胺和半乳糖胺）的相对丰度随着土壤年龄的变化而变化，表明微生物在千年时间尺度上发生了变化。观察到的化学成分变化比凋落物分解过程中通常观察到的变化要慢得多。随着风化作用的发展，泥层的吸附特征逐渐形成，并在泥层深层沉积了大量的有机碳，如Ta-c（沉积1640 yr BP）和Ta-d（沉积8940 yr BP）。这些观察结果表明，在凋落物分解的早期阶段，微生物迅速降解和改变，随后在掩埋之后，当吸附和遮挡等物理化学过程以及环境条件的变化影响有机物的积累和组成时，降解速度要慢得多。因此，有机质分解过程中的微生物过程和有机质成岩过程中的物理化学过程决定了埋藏土壤有机质的化学特征、反应性和年龄。
Deep soils contain more organic carbon than surface soils, and deep organic carbon has a longer carbon mean residence time. Relatively little is known about the degradation of organic matter in deep soils, especially over millennial time scales. Tephra (volcanic ash) deposition occasionally buries surface soils and forms deep soils rich in organic matter. In order to investigate the alteration and dynamics of buried organic matter in deep soils, we characterized common biochemicals, combined amino acids and amino sugars, in tephra layers deposited over millennial timescales in Hokkaido, Japan. Chemical analyses indicated relative abundances of specific amino acids (e.g. leucine and phenylalanine) and amino sugars, (e.g. glucosamine and galactosamine) changed with tephra soil age, indicating microbial alterations over millennial time scales. The observed changes in chemical composition were much slower than those typically observed during litter decomposition. Adsorption characteristics of the tephras developed with weathering and contributed to substantial organic carbon accumulation in the deep, aged tephra layers, such as Ta-c (deposited 1640 yr BP) and Ta-d (deposited 8940 yr BP). These observations indicate rapid microbial degradation and alteration during early stages of litter decomposition followed by much slower degradation following burial, when physicochemical processes such as sorption and occlusion and changes in environmental conditions influence organic matter accumulation and composition. Thus, microbial processes during organic matter decomposition and physicochemical processes during tephra diagenesis shape the chemical characteristics, reactivity and age of organic matter in buried tephra soils.