Qualitative near infrared spectroscopy, a new tool to recognize past vegetation signature in soil organic matter

• NIRS is a powerful method to discriminate soils according to their vegetation cover.
• There is little influence of the lipidic content on the NIR spectra of SOM.
• Vegetation changes can be detected by NIRS.
• NIRS needs further development to be used as a vegetation cover proxy.

Previous studies (Ertlen et al., 2010) have shown that near infrared (NIR) spectroscopy of soil organic matter (SOM) can be used successfully to discriminate between SOM from topsoils under forest vs. grassland following establishment of a referential. We have now extended this referential of topsoils, and the derived model was used to characterize SOM within three soil profiles in order to test if vegetation changes throughout these profiles can be detected using NIR spectra from buried soil organic matter. Comparison between the results from this new proxy based on NIR measurements and other historical and pedoanthracological data documenting soil occupation shows no major contradiction in terms of vegetation cover and its evolution with time. These promising results will need further development in order to provide a new palaeoenvironmental tool that is far less time consuming and easier to handle than other methods like pedoanthracology or soil lipid analysis.