Characterization and chemo-taxonomic evaluation of plant leaf waxes (long chain n-alkanoic acids, n-alkanes and n-alkanols) as a vegetation biomarker from species of the South American temperate forest (STF)

Abstract

Plant leaf waxes are used as vegetation biomarkers in several archives (i.e. soils, lake and marine sediments), study of these compounds in modern plants is needed to makes their application and interpretation more robust. However, in the South American Temperate Forest (STF), few species have been studied. The main goal of this research was to characterize twelve dominant modern species of the STF using three classes of leaf wax compounds, n-alkanoic acids, n-alkanes and n-alkanols. In addition, we evaluate the potential of leaf waxes as a vegetation and chemotaxonomic biomarker in the region, considering species that were found in different sampling sites and therefore environmental conditions. Clear differences among leaf wax abundance (μg/g) and ACL (average chain length) within and among the twelve species were found. Only the ACL of n-alkanoic acids and n-alkanols allows differentiation between leaf habit species (i.e. evergreen vs. deciduous), with high values associated with evergreen and low values with deciduous plants. This study differentiates the five species found in more than one site (i.e. different environmental condition) using different combinations of leaf waxes and in addition using only n-alkanes. It was not possible to differentiate among all sites with any combination of leaf waxes. The differences in the distribution of leaf waxes among species is an expected pattern in the study area, and it seems reliable to use the ACL as a vegetation biomarker differentiating between evergreen and deciduous species. The clear chemotaxonomic differences among the five species exposed to different and natural environmental conditions and the high preservation potential of the study area allow us to suggest that leaf waxes are likely a reliable tool to be incorporated in quantitative models to track vegetation and may be useful as a chemotaxonomic biomarker at the species level.