Soil organic matter stabilization and turnover in agricultural post-fen soils

• Applicant: Professorin Dr. Jutta Zeitz, since 4/2018
• Subject Area: Soil Sciences
• Term: from 2016 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 321751246

Peatland soils store huge amounts of soil organic matter (SOM) and are often drained for agricultural use. This leads to peat decomposition and substantial depletion of SOM. Shallow fen peat soils might develop into post-fen soils (PFS), which are in between mineral and organic soils. PFS still contain considerable amounts of SOM after long-term agricultural use, which consists of old, peat-derived compounds as well as of new SOM, incorporated through harvest residues. It is not clear, how SOM is protected in PFS and how the old and more recalcitrant compounds influence stabilization and turnover of SOM. The aim of the research is to identify and to quantify processes of SOM stabilization in PFS and to study the influence of old SOM on mean residence time and turnover in bulk soils and functional SOM pools. Therefore, SOM dynamics in adjacent mineral soils, PFS and organic soils will be studied. All studied soils are under the same agricultural use but differ in their hydrological conditions and pedogenesis. Through SOM fractionation into free, occluded and mineral-associated organic matter, SOM pools with different stability and turnover will be quantified. The influence of old SOM will be studied by determination of mean residence times in pools and bulk soils using radiocarbon dating. In addition, SOM turnover of the studied soils will be determined after a vegetation change from grassland (C3) to maize (C4) by stable isotope measurements. This methodical approach provides detailed information on SOM dynamics in agricultural PFS for the first time and serves as a base for modelling turnover of SOM with respect to possible losses of C and N. The results give novel insights into mechanisms of SOM stabilization and turnover as well as they contribute to a better and general understanding of processes and controls of C cycling in agricultural soils.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Christian Heller, until 4/2018