Disentangling the role of microbial residues in plant-soil systems
Following the experiments carried out during the first phase of the SPP, four experiments were designed to distinguish EPS (extracellular polymeric substances) from microbial necromass in agricultural soils, based on the following central hypotheses: (1) amino sugars (AS) are markers for microbial residues, i.e., EPS and necromass (cell remains) in soils; (2) coupling AS measurements with other indicators (e.g. ester-linked fatty acid methyl esters) can differentiate EPS from necromass dynamics and (3) plant and microbial EPS production is different but interrelated. In the first experiment, the amino sugar composition of biomass C and the residual fraction (EPS and necromass) will be investigated over time in bacterial and fungal cultures, grown in different mineral matrixes. In this experiment, heat productions will be additionally monitored using microcalorimetry. In the second experiment, increasing the gradient of complexity of our proposal, the amino sugar composition of microbial biomass carbon and the residual fraction will be measured again over time, but now in agricultural soils. In the third experiment, as part of the ‘SOM battery’ joint SPP experiment, the contribution of microbial residues to SOM’s potential in storing net carbon and energy will be investigated. Lastly, in the fourth experiment, the composition of ‘rhizo-EPS’ will be investigated and a profile of plant-derived and microbial-derived EPS will be created. In all experiments, samples (i.e. microbial biomass, soil, EPS) will be analysed for their concentration of amino sugars, combined with their compound-specific δ13C analysis (when applicable). EPS samples will be additionally checked for total organic 13C, total carbohydrates and total proteins. In the soil, soil organic 13C, microbial biomass 13C will further be measured. Finally, in the soil atmosphere, the evolution of total CO2 and 13CO2 will be measured.
Link to English scientific abstract
Link to German scientific abstract
Link to project in the 1st phase
Research Team
Project Leader
joerge@uni-kassel.de
Project Leader
jdyckma@gwdg.de
Project Leader
b.ludwig@uni-kassel.de
PhD Student
rebeca.oliva@uni-kassel.de
University of Kassel
Soil Biology and Plant Nutrition
Environmental Chemistry
Georg-August-Universität Göttingen
Centre for Stable Isotope Research and Analysis