Rhizosphere; Roots; Biomarkers; Deep subsoil; Compound-specific isotopes; Terrestrial archives; Radiocarbon dating
Wiesenberg Guido L.B., Gocke Martina I. (2017), Analysis of Lipids and Polycyclic Aromatic Hydrocarbons as Indicators of Past and Present (Micro)Biological Activity, Springer Nature, Berlin, Heidelberg, 61-91.
Gocke Martina I., Huguet Arnaud, Derenne Sylvie, Kolb Steffen, Dippold Michaela A., Wiesenberg Guido L.B. (2017), Disentangling interactions between microbial communities and roots in deep subsoil, in Science of The Total Environment
, 575, 135-145.
Gocke Martina I., Kessler Fabian, van Mourik Jan M., Jansen Boris, Wiesenberg Guido L.B. (2016), Paleosols can promote root growth of the recent vegetation – a case study from the sandy soilsediment sequence Rakt, Netherlands, in Soil
, 2, 537-549.
Újvári Gábor, Stevens Thomas, Svensson Anders, Klötzli Urs S., Manning Christina, Németh Tibor, Sweeney Mark R., Gocke Martina, Wiesenberg Guido L.B., Markovic Slobodan B., Zech Michael (2015), Two possible source regions for Central Greenald last glacial dust, in Geophysical Research Letters
, 42, 10399-10408.
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 (> 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 < 2 m, (e.g. German Research Foundation (DFG) Research Group SUBSOM the current project focuses on the deep subsoil (> 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. Furthermore, d2H and d13C will be determined for alkane biomarkers to estimate the hydrological and temperature differences of sedimentary and root related alkanes, i.e. under which conditions deposition takes place and how they changed towards times of root penetration. Finally, the compound-specific radiocarbon dating of alkanes enables the assessment of the timeframe of root penetration. The combination of several lipid fractions with compound-specific isotopes on root features in the deep subsoil will contribute to our understanding of carbon cycling in the deep subsoil on the one hand and on the other hand will enable improving the interpretation of paleoenvironmental parameters assessed via OM in a variety of unconsolidated subsoil material.