Analysis of molecular proxies of a peat core by thermally assisted hydrolysis and methylation-gas chromatography combined with multivariate analysis

•Analyses of a peat core by THM of soil organic matters.•Analyses of molecular marker compounds, lignin, fatty acids and carbohydrates.•Principal component analysis shows clearly three main clusters corresponding to the three well known ecological layers in a peat core: acrotelm, mesotelm and catotelm.

We applied principal component analysis on a data set of 55 compounds obtained with thermochemolysis with tetramethylammonium hydroxide as chemical agent from samples (24 different depths) along a one-meter length peat core. Principal component analysis allows to reduce the dimensionality of a data set that retains most of the variation present in the original variables (here F1 + F2 = 54.57%). Compounds are from four biochemical classes (lignin, carbohydrates and fatty and ω-hydroxy acids). Results show that samples are grouped in three clusters in the F1-F2 plot. Biomarkers of microbial and especially bacterial activity (terminally branched fatty acids) and of Sphagnum mosses (p-hydroxyphenyl compounds, fucose) are concentrated in the surface layers: the acrotelm (from 0 to −20 cm) and the mesotelm (from −20 to −50 cm). Biomarkers of higher plant contribution (C20+ fatty acids, C22 and C24 ω-hydroxy fatty acids, xylose and lignin compounds) are concentrated in the deeper layers of the peat core: the catotelm (from −50 to −100 cm).