We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where (13)C-depleted leaf litter was incubated on a (13)C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three (13)C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., delta(13)C(vsPDB) approximately -43 per thousand), differing in their degradability, were incubated on a C4 soil (delta(13)C(vsPDB) approximately -18 per thousand) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2omega6,9) was found to be very depleted in (13)C (delta(13)C(vsPDB) approximately from -38 to -42 per thousand) compared to all other PLFAs (delta(13)C(vsPDB) approximately from -14 to -35 per thousand). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27-C31) n-alkanes were the only to have a depleted delta(13)C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in (13)C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition.

中文翻译：

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微生物证据表明微生物分解过程中微生物介导的直接碳输入来自三个不同凋落物的土壤化合物。

我们在实验室实验中显示了将不同化合物特异性同位素分析耦合在一起的潜力，其中（13）C贫乏的枯枝落叶在（13）C富集的土壤上孵育。我们研究的目的是确定保留了来自三种不同凋落物物种的碳的土壤化合物。将三（13）C枯竭的凋落物（Liquidambar styraciflua L.，Cercis canadensis L.和Pinus taeda L.，δ（13）C（vsPDB）大约每千-43个）降解，将它们降解于C4在实验室控制的条件下土壤（delta（13）C（vsPDB）大约为千分之-18）8个月。在收获时，对不同类别的土壤化合物（即磷脂脂肪酸（PLFA），正构烷烃和土壤热解产物）进行了化合物特异性同位素分析。亚油酸（PLFA 18：2omega6，9）被发现与所有其他PLFA（delta（13）C（vsPDB）大约为-14）相比，（13）C（delta（13）C（vsPDB）大约从每千个-38至-42）非常耗尽到-35 /千）。因此，真菌被确定为微生物中第一个使用枯枝落叶作为C来源的微生物。在正构烷烃中，长链（C27-C31）正构烷烃是唯一具有耗尽的delta（13）C的物质。这表明并非土壤中所有来自凋落物的碳都被微生物转化。（13）C中的耗竭也存在于不同类别的热解产物中，这表明即使在分解8个月后，源自凋落物的C也会掺入化学稳定性较低或较低的化合物中。