Lignin oxidation products in soil, dripwater and speleothems from four different sites in New Zealand

Heidke, Inken, Hartland, Adam, Scholz, Denis, Pearson, Andrew, Hellstrom, John, Breitenbach, Sebastian and Hoffmann, Thorsten (2021) Lignin oxidation products in soil, dripwater and speleothems from four different sites in New Zealand. Biogeosciences, 18 (7). pp. 2289-2300. ISSN 1726-4189

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Official URL: https://doi.org/10.5194/bg-18-2289-2021

Abstract

Lignin oxidation products (LOPs) are widely used as vegetation proxies in climate archives, such as sediment and peat cores. The total LOP concentration, Σ8, provides information on the abundance of vegetation, while the ratios C/V and S/V of the different LOP groups also provide information on the type of vegetation. Recently, LOP analysis has been successfully applied to speleothem archives. However, there are many open questions concerning the transport and microbial degradation of LOPs on their way from the soil into the cave system. These processes could potentially alter the original source-dependent LOP signals, in particular the C/V and S/V ratios, and thus complicate their interpretation in terms of past vegetation changes. We analyzed LOPs in leaf litter and different soil horizons as well as dripwater and flowstone samples from four different cave sites from different vegetation zones in New Zealand using ultrahigh-performance liquid chromatography coupled to high-resolution mass spectrometry. We test whether the original source-dependent LOP signal of the overlying vegetation is preserved and can be recovered from flowstone samples and investigate how the signal is altered by the transport from the soil to the cave. The LOP concentrations range from mg g−1 in the soil to ng g−1 in the flowstones. Our results demonstrate that, from the soil to the flowstone, the C/V and S/V ratios both increase, while the total lignin content, Σ8, strongly decreases. This shows that the LOP signal is strongly influenced by both transport and degradation processes. Nevertheless, the relative LOP signal from the overlying soil at the different cave sites is preserved in the flowstone. We emphasize that for the interpretation of C/V and S/V ratios in terms of past vegetation changes, it is important to compare only samples of the same type (e.g., speleothem, dripwater or soil) and to evaluate only relative variations.

Item Type: Article
Additional Information: Funding information: Denis Scholz received funding from the German Research Foundation (grant nos. SCHO 1274/9-1 and SCHO 1274/11-1). This study received funding through a Marie Skłodowska-Curie grant (agreement no. 691037) from the European Union’s Horizon 2020 Research and Innovation program, a Marsden Fund grant (no. UOW1403), and a Rutherford Discovery Fellowship (no. RDF-UOW1601) to Adam Hartland. This open-access publication was funded by Johannes Gutenberg University Mainz.
Subjects: F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Elena Carlaw
Date Deposited: 16 Apr 2021 08:22
Last Modified: 16 Apr 2021 08:30
URI: http://nrl.northumbria.ac.uk/id/eprint/45934

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