This data publication is supplementary to a study on the climatic controls on leaf wax hydrogen isotopes, by Gaviria-Lugo et al. (2023). The dataset contains hydrogen isotope ratios from leaf wax n-alkanes (δ2Hwax) taken from soils, river sediments and marine surface sediments along a climatic gradient from hyperarid to humid in Chile. In addition, for each sampling site the hydrogen isotope ratios from precipitation (δ2Hpre) from the grids produced by the Online Isotopes in Precipitation Calculator (OIPC) (Bowen and Revenaugh, 2003). Furthermore, for each sampling site we report mean annual data of precipitation, actual evapotranspiration, relative humidity, and soil moisture, all derived from TerraClimate (Abatzoglou et al., 2018). Also provide data of mean annual temperature and the annual average of maximum daily temperature derived from WorldClim (Fick and Hijmans, 2017). As a final climatic parameter, we also derived data of aridity index from the Consultative Group of the International Agricultural Research Consortium for Spatial Information (CGIARCSI) (Trabucco and Zomer, 2022). In addition to climatic variables, for each site we include land cover fractions of trees, shrubs, grasses, crops, and barren land. These land cover fractions were obtained from Collection 2 of the Copernicus Global Land Cover layers (Buchhorn et al., 2020) via Google Earth Engine.
For further comparison here we provide δ2Hwax compiled from 26 publications (see references) that reported both the n-C29 and n-C31 n-alkanes homologues from soils and lake sediments. For each sampling site of the global compilation, we provide δ2Hpre and the same climatic and land cover parameters as for the Chilean data (i.e., precipitation, actual evapotranspiration, relative humidity, soil moisture, aridity index, temperature, fraction of trees, fraction of grasses, etc.), using the same sources.
The data is provided here as one single .xlsx file containing 9 data sheets, but also as 9 individual .csv files, to be accessed using the file format of preference. Additionally, 5 supplementary figures that accompany the publication Gaviria-Lugo et al. (2023) are provided in one single .pdf file. The samples taken for this study were assigned International Geo Sample Numbers (IGSNs), which are included in the provided tables S4, S5 and S6.
Roots are currently discussed to store considerable amounts of carbon in the subsoil. Although it is well known that roots can penetrate the subsoil and deep subsoil (greater than 2 m) several meters deep, it remains unclear, how much carbon they contribute, if they lead to net carbon sequestration in the long-term and under which conditions they lead to carbon accumulation. Rhizoliths and biopores are root-related features that frequently occur in soil and underlying soil parent material. Recent studies in unconsolidated sediments show that they enable investigating the long-term effects of root penetration even after the lifetime of the source plant and thus the assessment of sustainable impacts of roots on subsoil organic matter (OM). While other research groups deal with the subsoil less than 2 m, (eg German Research Foundation (DFG) Research Group SUBSOM the current project focuses on the deep subsoil (greater than 2 m), where a significant overprint of OM is expected. In fact, this part of the subsurface is usually not regarded by soil scientists, but of large interest for paleoenvironmental researchers as valid e.g. for loess-paleosol sequences. So far, the effect of roots on subsoil OM was only studied on a single site in SW Germany during a precursor project, DFG (WI2810/10). Based on that project, the current proposal aims at the investigation of the transferability of the results to other sedimentary settings and ecological contexts. At several sites along a NE-SW transect across Europe (from The Netherlands across Germany, Switzerland, Austria, Hungary towards Serbia), unconsolidated material like dune and fluvial sands, as well as loess-paleosol sequences will be investigated with respect to OM quantity and quality as influenced by root penetration. Preliminary investigations of six potential sites in Germany, Hungary and Serbia showed that biopores and other root-related features can reach similar abundances in different settings. Nevertheless, consequences for OM sequestration and turnover may be different, depending not only on the respective source vegetation but also sedimentary properties. The target of the current project is to identify carbon losses or sequestration related to root penetration, which will be assessed by bulk organic and inorganic carbon contents as well as a variety of lipid biomarkers including alkanes, fatty acids, alcohols, glycerol dialkyl glycerol tetraethers and suberin markers. The combination of these biomarkers enables the assessment of root-related overprint, if transects from root features to surrounding material free of them are investigated. The data will be fed into the VERHIB model for source apportionment of sedimentary and root-related OM. (abridged text)