Peat humification analysis has been used widely over the last three decades to reconstruct bog surface wetness (BSW) for use as a palaeoclimate proxy. The technique has the advantage that it is quick and relatively inexpensive to perform, allowing for high resolution and contiguous sampling of peat archives. However, some concerns have been raised over the quality of the resultant proxy-climate records because changes in the plant species composition of peat may contribute a ‘species signal’ to records, potentially confusing the relationship between bog water table position and the apparent degree of peat humification. This paper uses the k-values of fresh plant material (sensu Overbeck, 1947 – i.e. the absorption value of the alkali extracts of fresh plant material) to explore the impact of changing plant colouration in a Holocene peat humification-based palaeoclimate archive from Newfoundland. We calculate k-scores for peat samples, using plant macrofossil data and the k-values of individual species to provide a down-core visualisation of the plant species signal. Although, overall, the humification data are validated, comparison of the original humification data with a k-adjusted version shows that the species signal is sometimes sufficient to change the timing and number of decadal to centennial-scale events recorded in the data as well as millennial to multi-millennial-scale trends.
The authors acknowledge the Natural Environment Research Council (NERC) for funding support under Grant NER/B/S2001/00885 and the NERC PRECIP project NE/G019851/1. Further funding for peat humification analyses and four radiocarbon dates was provided by European Commission Contract No. EVK2-CT-2002-00166 (ACCROTELM). We also acknowledge the support of the NERC Radiocarbon Steering Committee. The University of Southampton Cartographic
Unit assisted with the preparation of Fig. 1. The 6.56-m peat humification data series was generated by Annie Wojatschke and Dr. John Daniell. Dr. Phil Toms conducted the dating analyses on short-lived isotopes. We would also like to thank two referees for their comments on a previous version of this paper.