Incorporation of hydrogen from ambient water into the C-bonded H pool during litter decomposition
Incorporation of hydrogen from ambient water into the C-bonded H pool during litter decomposition
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DOI：
10.1016/j.soilbio.2021.108407
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发表时间：
2021-11
影响因子：
9.7
通讯作者：
A. Kessler;K. Kreis;S. Merseburger;W. Wilcke;Y. Oelmann
中科院分区：
文献类型：
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作者：
A. Kessler;K. Kreis;S. Merseburger;W. Wilcke;Y. Oelmann
据观察，干旱会影响地上植物有机质的碳键稳定 H 同位素比率（δ2Hn 值），但不会影响相关土壤有机质 (SOM) 的 δ2Hn 值。相反，SOM 的 δ2Hn 值与当地降雨量的长期平均 δ2H 值在空间上相关。为了解释这种差异，我们研究了在实验室微观世界中的落叶分解过程中，C-键合的 H 是否以及在多大程度上被环境水-H 取代。在用两种 H 同位素标记水（δ2Hiw：+50‰、+250‰）对落叶（Fagus sylvatical.-山毛榉、Acerseudoplatanusl.-枫树）进行为期 4 周的孵化时，我们发现了少量同位素标记的 H 的掺入。进入山毛榉垃圾中的碳键氢库（<总碳键氢的5%）。对于浸出的、更具反应性的溶液中总有机物 (TOM)，我们估计 8-9% 的碳键 H 在孵化过程中被同位素标记取代。我们认为，环境水中 H 的少量掺入可归因于微生物过程。然而，微生物处理过程中环境水中 H 的少量掺入不足以覆盖植物有机质中存在的干旱信号，并使 SOM 的 δ2Hn 值向长期降雨的方向移动。这支持了这样的观点，即 SOM 起源于地下来源，包括根和微生物，其固有地表现出与长期降雨相关的 δ2Hn 值。
Aridity was observed to affect the C-bonded stable H isotope ratios (δ2Hnvalues) of aboveground plant organic matter but not δ2Hnvalues of associated soil organic matter (SOM). Instead, δ2Hnvalues of SOM correlated spatially with long-term mean δ2H values of local rainfall. To explain this discrepancy, we investigated if and to which degree C-bonded H was replaced by ambient water-H during leaf litter decomposition in laboratory microcosms.In a four-week incubation of leaf litter (Fagus sylvatical. -beech,Acer pseudoplatanusl. -maple) with two H-isotopically labeled waters (δ2Hiw: +50‰, +250‰), we found a small incorporation of isotopically labeled H into the C-bonded H pool (<5% of total C-bonded H) in beech litter. For the leached, more reactive total organic matter in solution (TOM), we estimated that 8–9% of C-bonded H was replaced by the isotope label during incubation. We suggest that the small incorporation of H from ambient water can be attributed to microbial processes.However, the small incorporation of H from ambient water during microbial processing would not be sufficient to overprint the aridity signal present in plant organic matter and shift δ2Hnvalues of SOM towards those of long-term rainfall. This supports the suggestion, that SOM originates from belowground sources including roots and microorganisms, which inherently show δ2Hnvalues related with those of long-term rainfall.