13C signature of CO2 evolved from incubated maize residues and maize-derived sheep faeces
13C signature of CO2 evolved from incubated maize residues and maize-derived sheep faeces
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DOI：
10.1016/j.soilbio.2003.07.002
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发表时间：
2004-01-01
影响因子：
9.7
通讯作者：
Christensen, BT
中科院分区：
文献类型：
--
作者：
Kristiansen, SM;Brandt, M;Christensen, BT
C-13自然丰度的时空变化分析经常被用来研究植物残留物的转化和土壤有机质周转，在长期持续的C-3型光合作用途径被C-4型植被取代(反之亦然)的地点。与这种分析相关的一个有争议的问题是，在复杂底物中碳的微生物周转过程中，同位素分馏的意义。为了评估这一问题，用玉米残渣和绵羊粪便对C-3土壤和石英砂进行了改良，完全以玉米青贮料为饲料。样品在15摄氏度下孵化117天(玉米残渣)或224天(绵羊粪便)。在孵化过程中释放的二氧化碳被捕获在氢氧化钠中，并分析了碳同位素含量。在培养结束时，63%和50%的玉米C在土壤和沙子中分别以CO2的形式释放出来，而与土壤和沙子培养的粪便C中有32%被回收为CO2。玉米和粪便的分解模式相似，但玉米的分解速度是粪便的两倍。粪便的Delta(13)C比玉米残体的Delta(13)C低0.3‰，而用于培养的C-3土壤的Delta(13)C为-31.6‰，从未改良的C-3土壤中回收的CO2的Delta(13)C值与C(3-)土壤本身相似或略低(最高可达-1.5‰)，除了最初的C-13富集CO2外。来自沙基培养的二氧化碳的增量(13)C值通常在-15ppm到-17ppm之间，即大约比玉米和粪便测量的增量(13C)低-3ppm。我们的研究清楚地表明，复杂底物的分解与同位素分馏有关，导致演化出的二氧化碳相对于底物在C-13中被耗尽。因此，保留在土壤中的微生物产品必须在C-13中得到丰富。(C)2003爱思唯尔有限公司。所有比赛已预留。
Analyses of the spatial and temporal variations in the natural abundance of C-13 are frequently employed to study transformations of plant residues and soil organic matter turnover on sites where long continued vegetation with the C-3-type photosynthesis pathway has been replaced with a C-4-type vegetation (or vice versa). One controversial issue associated with such analyses is the significance of isotopic fractionation during the microbial turnovers of C in complex substrates. To evaluate this issue, C-3-soil and quartz sand were amended with maize residues and with faeces from sheep feed exclusively on maize silage. The samples were incubated at 15 degreesC for 117 days (maize residues) or 224 days (sheep faeces). CO2 evolved during incubation was trapped in NaOH and analysed for C isotopic contents. At the end of incubation, 63 and 50% of the maize C was evolved as CO2 in the soil and sand, respectively, while 32% of the faeces C incubated with soil and with sand was recovered as CO2. Maize and faeces showed a similar decomposition pattern but maize decomposed twice as fast as faeces. The delta(13)C of faeces was 0.3parts per thousand lower than that of the maize residue (delta(13)C - 13.4parts per thousand), while the delta(13)C of the C-3-soil used for incubation was - 31.6parts per thousand, The delta(13)C value of the CO2 recovered from unamended C-3-soil was similar or slightly lower (up to - 1.5parts per thousand) than that of the C(3-)soil itself except for an initial flush of C-13 enriched CO2. The delta(13)C values of the CO2 from sand-based incubations typically ranged - 15parts per thousand to - 17parts per thousand, i.e. around - 3parts per thousand lower than the delta(13)C measured for maize and faeces. Our study clearly demonstrates that the decomposition of complex substrates is associated with isotopic fractionation, causing evolved CO2 to be depleted in C-13 relative to substrates. Consequently the microbial products retained in the soil must be enriched in C-13. (C) 2003 Elsevier Ltd. All fights reserved.