Humic fingerprinting of soil organic matter as a proxy for palaeo-reconstruction
Vancampenhout, K.; Wouters, K.; Caus, A.; De Vos, B.; Gullentops, F.; Dudal, R.; Swennen, R.; Deckers, J.
Communications in Agricultural and Applied Biological Sciences 70(2): 263-267
2005
ISSN/ISBN: 1379-1176 PMID: 16366322 Document Number: 586034
The composition of soil organic matter is evaluated as a proxy for environmental change in soil memory records using analytic pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Thirty-four soil samples of Ah horizons of different ecosystems at different locations in West Siberia, Poland, Belgium, Nebraska (USA), Tanzania and Peru were analysed using py-GC/MS. Data obtained were analysed using multivariate factor analysis and indicator species analysis, which showed general relationships between humic composition and vegetation type. Within temperate biomes, a difference in soil organic matter of sites with different soil texture was most prominent. The Rocourt soil in the Vandersanden Quarry in Veldwezelt (Belgian Pleistocene loess belt) was selected as a case study on the use of humic fingerprinting. The humiferous complex of Remicourt (HCR) was analysed by py-GC/MS. The dark band at the base of the HCR clearly differed in humic composition compared to the lighter band on top. It had the highest levels of levoglucosan and contained mainly strongly decomposed components. This suggests a soil layer that was at the surface for a long period of time. This layer also had higher levels of C and N, and a higher C/N than overlying layers. Samples higher in the profile contain less levoglucosan and humic compounds become less degraded. A stable soil surface was overlaid by a horizon formed under colder and more arid conditions. A remarkable humic fingerprint was obtained from a sample just below the top of the HCR which contains large amounts of stable aromatic compounds and poly-aromatic compounds known as charcoal derivatives. The Veldwezelt case study yielded valuable indications about former climate and vegetation, although the link with soil organic matter components of current ecosystems was not established.