A novel pathway of soil organic matter formation by selective preservation of resistant straight-chain biopolymers: chemical and isotope evidence

Lichtfouse, Éric; Chenu, Claire; Baudin, François; Leblond, Claudette; Silva, Martine Da; Béhar, F.; Derenne, Sylvie; Largeau, Claude; Wehrung, Patrick; Albrecht, Pierre

doi:10.1016/s0146-6380(98)00005-9

Cited by 157 publications

(105 citation statements)

References 21 publications

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“…However, the molecular structure of humic substances being poorly known and still a matter of debate (14,15), other processes may explain how humification takes place. Indeed, several studies suggest that a substantial part of humin is made of lipidic components (8,11,(15)(16)(17). Here, we report the identification of n-alkanes, steroids, isoprenoid, hopanoids, and aliphatic biopolymers trapped in soil humin.…”

Section: Introductionmentioning

confidence: 74%

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Occurrence of Biomarkers and Straight-Chain Biopolymers in Humin: Implication for the Origin of Soil Organic Matter

Lichtfouse

Leblond

Silva

et al. 1998

Naturwissenschaften

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Soil organic matter is a very complex mixture of compounds derived from the decay of living organisms such as plants, fungi and bacteria. The mechanisms that control the preservation of soil organic matter are poorly known. This is notably due to our scarce knowledge of the molecular structure of humin, the insoluble part of soil organic matter. Three major hypotheses have been proposed to explain the formation of soil organic matter: the plant alteration hypothesis, the microbial synthesis hypothesis and the chemical polymerisation hypothesis. Here we used a "biomarker" approach, developped mainly in sedimentary geochemistry, to gain some insight on the mechanims of preservation of soil organic matter. We analysed the compounds occurring in soil humin. We isolated humin from a maize crop soil by solvent extraction to remove free lipids, then by NaOH extraction to remove humic and fulvic acids, then by HF/HCl treatment to remove minerals. The humin residue was then pyrolysed at 600°C. The pyrolysate was fractionated into alkane/alkene and aromatic fractions by silica gel column chromatography. The fractions were analysed by gas chromatography coupled to mass spectrometry (GC-MS). We identified n-alkanes, n-alkenes, prist-1-ene, sterenes, hopenes and aromatic steroids in the humin pyrolysate. The results show that the stabilisation of soil humic substances may be achieved by selective preservation of lipids, involving three processes: encapsulation of small apolar molecules, chemical bonding of functionalized biomarkers, and preservation of straight-chain microbial polymers.

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Section: Introductionmentioning

confidence: 74%

“…Numbers refer to carbon numbers of n-alkanes and n-alkenes. Detailed procedures are reported elsewhere (16,17,24). A sample of maize crop soil (290 g) was thoroughly extracted with CHCl 3 -MeOH 3/1 v/v to remove free lipids, then with NaOH 0.1 M to remove fulvic and humic acids.…”

Section: Linear Alkanesmentioning

confidence: 99%

Occurrence of Biomarkers and Straight-Chain Biopolymers in Humin: Implication for the Origin of Soil Organic Matter

Lichtfouse

Leblond

Silva

et al. 1998

Naturwissenschaften

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“…This was confirmed for an agricultural soil by Quenea et al (2006), who observed old-forest-and fungi-derived odd long-chain alkanes based on compound-specific isotope analysis and lipid distribution patterns. Possible pathways of in situ genesis of n-alkanes in soils are the reduction of nalkenes and n-alcohols, the decarboxylation of bacterial nfatty acids, and the degradation of biopolymers containing aliphatic side chains (Lichtfouse et al, 1998a). Nevertheless, based on the large number of studies in which typical higherplant-derived patterns of lipids are reported and used in soils (Table 1), including indicative ACL and CPI values, microbial input of longer chain length straight-chain lipids generally does not seem to be a major factor compared to directplant-derived input in the topsoil Bai et al, 2009).…”

Section: Microbial Inputmentioning

confidence: 99%

Opportunities and limitations related to the application of plant-derived lipid molecular proxies in soil science

Jansen

Wiesenberg

2017

SOIL

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Abstract. The application of lipids in soils as molecular proxies, also often referred to as biomarkers, has dramatically increased in the last decades. Applications range from inferring changes in past vegetation composition, climate, and/or human presence to unraveling the input and turnover of soil organic matter (SOM). The molecules used are extractable and non-extractable lipids, including ester-bound lipids. In addition, the carbon or hydrogen isotopic composition of such molecules is used. While holding great promise, the application of soil lipids as molecular proxies comes with several constraining factors, the most important of which are (i) variability in the molecular composition of plant-derived organic matter both internally and between individual plants, (ii) variability in (the relative contribution of) input pathways into the soil, and (iii) the transformation and/or (selective) degradation of (some of) the molecules once present in the soil. Unfortunately, the information about such constraining factors and their impact on the applicability of molecular proxies is fragmented and scattered. The purpose of this study is to provide a critical review of the current state of knowledge with respect to the applicability of molecular proxies in soil science, specifically focusing on the factors constraining such applicability. Variability in genetic, ontogenetic, and environmental factors influences plant n-alkane patterns in such a way that no unique compounds or specific molecular proxies pointing to, for example, plant community differences or environmental influences, exist. Other components, such as n-alcohols, n-fatty acids, and cutin-and suberin-derived monomers, have received far less attention in this respect. Furthermore, there is a high diversity of input pathways offering both opportunities and limitations for the use of molecular proxies at the same time. New modeling approaches might offer a possibility to unravel such mixed input signals. Finally, the transformation and turnover of SOM offer opportunities when tracing such processes is the purpose of applying a molecular proxy while imposing limitations when they obliterate the molecular proxy signals linked to other phenomena. For n-alkanes several modeling approaches have recently been developed to compensate for (selective) degradation. Still, such techniques are in their infancy and information about their applicability to classes of components other than n-alkanes is lacking. All constraining factors considered can have a significant influence on the applicability of molecular proxies in soil science. The degree of influence strongly depends on the type of molecular proxy and the environmental context in which it is applied. However, the potential impact of the constraining factors should always explicitly be addressed whenever molecular proxies are applied in a soil scientific context. More importantly, there is still a serious lack of available information, in particular for compound classes other than the n-alkanes. Therefore, we...

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“…3), also indicated that the patterns of polysaccharide C (C-O bonds at 1035 cm . It should be kept in mind, however, that the nature of the clay-bound organic matter may vary with clay surface chemistry (Greenland 1965;Jardine et al 1989;Golchin et al 1995;Lichtfouse et al 1998;Kahle et al 2003;Zimmerman et al 2004). We were not successful in exploring other clay minerals or amorphous oxides that may have a very strong control on C stabilization through surface interactions (Mikutta et al 2006).…”

Section: ¡1mentioning

confidence: 99%

Organic matter stabilization in soil microaggregates: implications from spatial heterogeneity of organic carbon contents and carbon forms

2007

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This study investigates the spatial distribution of organic carbon (C) in free stable microaggregates (20-250 m; not encapsulated within macroaggregates) from one Inceptisol and two Oxisols in relation to current theories of the mechanisms of their formation. Two-dimensional micro-and nano-scale observations using synchrotron-based Fourier-transform infrared (FTIR) and near-edge X-ray absorption Wne structure (NEXAFS) spectroscopy yielded maps of the distribution of C amounts and chemical forms. Carbon deposits were unevenly distributed within microaggregates and did not show any discernable gradients between interior and exterior of aggregates. Rather, C deposits appeared to be patchy within the microaggregates. In contrast to the random location of C, there were micronscale patterns in the spatial distribution of aliphatic C-H (2922 cm ). Aliphatic C forms and the ratio of aliphatic C/ aromatic C were positively correlated (r 2 of 0.66-0.75 and 0.27-0.59, respectively) to the amount of O-H on kaolinite surfaces (3695 cm ¡1 ), pointing at a strong role for organomineral interactions in C stabilization within microaggregates and at a possible role for molecules containing aliphatic C-H groups in such interactions. This empirical relationship was supported by nanometer-scale observations using NEXAFS which showed that the organic matter in coatings on mineral surfaces had more aliphatic and carboxylic C with spectral characteristics resembling microbial metabolites than the organic matter of the entire microaggregate. Our observations thus support models of C stabilization in which the initially dominant process is adsorption of organics on mineral surfaces rather than occlusion of organic debris by adhering clay particles.

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A novel pathway of soil organic matter formation by selective preservation of resistant straight-chain biopolymers: chemical and isotope evidence

Cited by 157 publications

References 21 publications

Occurrence of Biomarkers and Straight-Chain Biopolymers in Humin: Implication for the Origin of Soil Organic Matter

Occurrence of Biomarkers and Straight-Chain Biopolymers in Humin: Implication for the Origin of Soil Organic Matter

Opportunities and limitations related to the application of plant-derived lipid molecular proxies in soil science

Organic matter stabilization in soil microaggregates: implications from spatial heterogeneity of organic carbon contents and carbon forms

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