Variations in microbial isotopic fractionation during soil organic matter decomposition
Variations in microbial isotopic fractionation during soil organic matter decomposition
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DOI：
10.1007/s10533-010-9432-7
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发表时间：
2011-10-01
期刊：
影响因子：
4
通讯作者：
Mariotti, A.
中科院分区：
文献类型：
--
作者：
Lerch, T. Z.;Nunan, N.;Mariotti, A.
土壤微生物量(SMB)参与土壤有机质(SOM)分解等关键过程。然而，它对SOM的同位素组成的贡献尚不清楚。通过对未改良的耕地土壤进行6个月的培养，研究了SMB和SOM组分(矿化、水溶性和不可提取)的C-13和N-15自然丰度的变化。利用脂肪酸甲酯特定同位素分析对微生物群落进行了研究。在整个培养过程中，相对于其他组分，SMB显著地富含C-13和N-15。然而，由于相对富含C-13的水溶性化合物的快速消耗，也观察到显著的同位素随时间的变化。SMB组分和水溶性N-15组分的差异随着水溶性C/N比的降低而增大，表明在培养过程中从N的同化转变为N的异化。这些变化也引起了微生物群落结构的改变。一旦系统达到稳定状态(1个月后)，同位素趋势似乎证实了在野外长期实验中获得的结果，因为长期存在持续的微生物同位素分馏，导致土壤有机质中C-13和N-15的浓缩。这项工作还表明，在解释短期培养研究时必须谨慎，因为与实验设置相关的扰动可能对C和N动态、C-13和N-15的微生物分馏以及微生物群落结构产生重要影响。
The soil microbial biomass (SMB) is known to participate in key soil processes such as the decomposition of soil organic matter (SOM). However, its contribution to the isotopic composition of the SOM is not clear yet. Shifts in the C-13 and N-15 natural abundances of the SMB and SOM fractions (mineralised, water soluble and non-extractable) were investigated by incubating an unamended arable soil for 6 months. Microbial communities were also studied using Fatty Acid Methyl Ester specific isotope analysis. The SMB was significantly C-13 and N-15-enriched relative to other fractions throughout the incubation. However, significant isotopic variations with time were also observed due to the rapid consumption of relatively C-13-enriched water soluble compounds. The increase in the difference in SMB and water soluble N-15 compositions as the water soluble C/N ratio decreased, indicated a shift from N assimilation to N dissimilation during the incubation. These changes also induced modifications of the microbial community structure. Once the system reached a steady-state (after 1 month), the isotopic trends appeared to corroborate those obtained in long term experiments in the field in that there was a constant microbial isotopic fractionation leading to a C-13 and N-15 enrichment of the SOM over the long-term. This work also suggests that caution must be exercised when interpreting short term incubation studies since perturbations associated with experimental set-up can have an important effect on C and N dynamics, microbial fractionation of C-13 and N-15 and microbial community structure.