Evaluating the applicability of the VERHIB model to a 2600-year peat sequence from Central Germany

Abstract

Plant-derived biomarkers have been used extensively for source identification of organic matter in soil, peat, and sediments. These are chemical components, primarily of leaf waxes, that are naturally more resistant to degradation than most organic molecules and can be preserved in depositional archives for hundreds to thousands of years. However, using biomarkers for vegetation reconstruction can be complicated because individual compounds or compound classes do not necessarily indicate specific plant sources. The composition across multiple compounds must be holistically evaluated to develop accurate reconstructions. The VERHIB model was developed to enable a range of n-alkane and n-alkanol data to be evaluated simultaneously and estimate past vegetation development using the biomarker signature of leaves and roots from present-day specimens of the plant species of interest compared to the preserved, mixed signature of a soil or peat core. In this study, we have applied the VERHIB model to data gathered from the Beerberg peatland in Central Germany. A previous study characterized plant macrofossils, pollen, n-alkane, n-alkanol, and n-fatty acid composition in the Beerberg peat. We have collected modern plant samples from the peatland and measured their biomarker composition to use as input for the model. Despite many overlapping biomarker signatures across plant species and parts, our results show that the model could recreate a reasonable vegetation development pattern for most of the peat core if n-fatty acid data were included alongside n-alkane data. The model had difficulty recreating the transition from poor fen vegetation to Sphagnum bog, which was evident in the plant macrofossil records, so further calibration is needed. This was the first attempt at considering n-fatty acid data in a reconstruction using the VERHIB model; previous reconstructions only included n-alkanes or a combination of n-alkanes and n-alkanols. Our study shows that n-fatty acids are a valuable compound class to add to the VERHIB model and provides recommendations for future development.