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Molecular insight into soil carbon turnover
Author(s) -
Gleixner Gerd,
Bol Roland,
Balesdent Jérôme
Publication year - 1999
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(19990715)13:13<1278::aid-rcm649>3.0.co;2-n
Subject(s) - chemistry , pyrolysis , lignin , isotopes of carbon , levoglucosan , soil water , mass spectrometry , pyrolysis–gas chromatography–mass spectrometry , phenols , organic chemistry , environmental chemistry , chromatography , total organic carbon , environmental science , aerosol , soil science , biomass burning
Curie‐point pyrolysis‐gas chromatography coupled on‐line to mass spectrometry (Py‐GC/MS) and isotope ratio mass spectrometry (Py‐GC/IRMS) were used to determine the individual turnover rate of specific carbohydrates, lignin, lipids and N‐containing compounds from French arable soils. The analysed soils were cultivated, either continuously with a C3 plant (wheat δ 13 C‐value = −25.2‰), or transferred to a C4 plant (maize δ 13 C‐value = −11.4‰) cropping 23 years ago. Most pyrolysis products identified were related to carbohydrates (furans), lipids (hydrocarbons and derivatives of benzene), proteins (nitriles and pyrrole) and lignins (phenols). The relative yield of all individual pyrolysis products was similar in the samples from the maize and control wheat soil. The isotopic enrichment between identical pyrolysis products from the two soils varied from 1 to 12 delta (δ) units, indicating that after 23 years of cultivation 7 to 90% of their C was derived from maize. This suggests a slow mean turnover time varying from 9 to 220 years. Based on the differences in isotopic enrichment of chemical structures after vegetation change the pyrolysis products could be divided into three groups: (i) pyrolysis products with a nearly complete C4 signal, e. g. phenol, derived from lignin degradation products, (ii) pyrolysis products with an intermediate isotopic enrichment of 6–8‰, most likely to be a composite of remaining (possibly physically protected) fragments derived from both maize and native wheat, and (iii) pyrolysis products showing only low enrichments in 13 C of 1–3‰. Most of their precursors were found to be proteinaceaous materials. This indicates that proteins or peptides are indeed preserved during decomposition and humification processes occurring in the soil. Our study highlights the potential of Py‐GC/MS‐C‐IRMS to further novel insights into the dynamics of soil organic constituents. Copyright © 1999 John Wiley & Sons, Ltd.