Stable hydrogen and carbon isotope ratios of methoxyl groups during plant litter degradation

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

Abstract

Stable hydrogen and carbon isotope ratios of methoxyl groups (δ2Hmethoxyl and δ13Cmethoxyl values, respectively) in plant material have been shown to possess characteristic signatures. These isotopic signatures can be used for a variety of applications such as constraining the geographical origin and authenticity of biomaterials. Recently, it has also been suggested that δ2Hmethoxyl values of sedimentary organic matter of geological archives might serve as a palaeoclimate/-hydrology proxy. However, deposited organic matter is subject to both biotic and abiotic degradation processes, and therefore an evaluation of their potential impact on the δ2Hmethoxyl and δ13Cmethoxyl values would allow more reliable interpretations of both isotopic signatures. Here, we investigated this potential influence by exposing foliar litter of five different tree species (Sycamore maple, Mountain ash, European beech, Norway spruce and Scots pine) to natural degradation. The foliar litter was sampled at nine intervals over a 27-month period, and the bulk methoxyl content as well as the δ2Hmethoxyl and δ13Cmethoxyl values were measured. At the end of the experiment, a loss of the bulk methoxyl in the range of ∼40–70 % was measured. Linear regression analysis showed no dependence of δ2Hmethoxyl values with methoxyl content for four out of five foliar litter samples studied (R2 in the range of 0.03 and 0.36, p >.05). On the contrary, the δ13Cmethoxyl values showed significant linear correlations for the great majority of the foliar litter samples (R2 in the range of 0.51 and 0.73, p <.05). The litter species with the greatest methoxyl loss (Mountain ash, Scots pine and Norway spruce) showed the strongest 13C enrichment, by up to ∼5 ‰. Since δ2Hmethoxyl shows no systematic overall change during the course of degradation, we propose that there is considerable potential for its use as a palaeoclimate proxy for a wide range of geological archives containing, for instance, fossil wood or sedimentary organic matter. Care would need to be taken if δ13Cmethoxyl values of degraded organic matter are used for palaeoclimate/-environmental investigations.

Details

Original languageEnglish
Pages (from-to)143-154
Number of pages12
JournalIsotopes in environmental and health studies
Volume51
Issue number1
Publication statusPublished - 2 Jan 2015
Peer-reviewedYes

External IDs

PubMed 25706484

Keywords

Keywords

  • biogeochemistry, carbon-13, decomposition, geological archives, hydrogen-2, isotope ecology, lignin, palaeoclimate proxy, pectin