Molecular marker records of land use change



Fisher, E, Oldfield, F, Wake, R, Boyle, J ORCID: 0000-0002-1172-1079, Appleby, P ORCID: 0000-0002-6945-1841 and Wolff, GA ORCID: 0000-0002-9380-1039
(2003) Molecular marker records of land use change. ORGANIC GEOCHEMISTRY, 34 (1). pp. 105-119.

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Abstract

Evidence of a changing environment in the catchment area of a small lake (Gormire, Yorkshire, UK) over the past 3000 years is provided by the mean carbon number of n-alkanes and the ratio of lignin thermochemolysis products, together with pollen analysis and bulk organic geochemistry. Periods of deforestation, which commenced at ∼600 BC and AD 1200, display a significant decrease in organic carbon contents of the lake sediments, which probably reflects dilution by enhanced influx of clastic material. The mean carbon number of waxy (C27-C31) n-alkanes closely corresponds with the percentage of pollen derived from grass in the sediments. A higher-plant derived triterpenoid, tentatively identified from its mass spectrum as 28-carboxyursen-12-enol, appears exclusively in samples where tree and shrub-derived pollen is dominant. Thermochemolysis of lignin confirms that there was a significant change in the nature of material deposited in the lake sediments from woody to grass dominated. Changes in both the sedimentary C/N ratios and yields of lignin-derived phenols suggest that deforestation events led to enhanced aquatic productivity, initially through the development of reed-swamp vegetation. © 2002 Elsevier Science Ltd. All rights reserved.

Item Type: Article
Additional Information: Evidence of a changing environment in the catchment area of a small lake (Gormire, Yorkshire, UK) over the past 3000 years is provided by the mean carbon number of n-alkanes and the ratio of lignin thermochemolysis products, together with pollen analysis and bulk organic geochemistry. Periods of deforestation, which commenced at similar to600 BC and AD 1200, display a significant decrease in organic carbon contents of the lake sediments, which probably reflects dilution by enhanced influx of clastic material. The mean carbon number of waxy (C-27-C-31) n-alkanes closely corresponds with the percentage of pollen derived from grass in the sediments. A higher-plant derived triterpenoid, tentatively identified from its mass spectrum as 28-carboxyursen-12-enol, appears exclusively in samples where tree and shrub-derived pollen is dominant. Thermochemolysis of lignin confirms that there was a significant change in the nature of material deposited in the lake sediments from woody to grass dominated. Changes in both the sedimentary C/N ratios and yields of lignin-derived phenols suggest that deforestation events led to enhanced aquatic productivity, initially through the development of reed-swamp vegetation. (C) 2002 Elsevier Science Ltd. All rights reserved. ## TULIP Type: Articles/Papers (Journal) ## issn: ISI:000180824400008
Uncontrolled Keywords: tetramethylammonium hydroxide tmah, contemporary marine-, sediments, organic-matter, lacustrine sediments, surface, sediments, early diagenesis, lake-sediments, fatty-acids, geochemistry, hydrocarbons
Subjects: ?? GA ??
?? GE ??
?? QD ??
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 12 Oct 2010 15:36
Last Modified: 16 Dec 2022 12:17
DOI: 10.1016/S0146-6380(02)00145-6
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/1196