PhD project offered by the IMPRS-gBGC in July 2021


Modelling the partitioning of bulk soil carbon into particulate and mineral associated pools along soil profiles: understanding causes and consequences for soil carbon sequestration

Marion Schrumpf , Sönke Zaehle


Enhanced soil organic carbon (SOC) sequestration is considered as a potential carbon-dioxide removal technique for climate change mitigation, but the prediction of potential soil carbon gains or losses with land-use, land management or climate change relies on an appropriate representation of the underlying mechanisms for carbon stabilisation and mineralisation in models. The last decade has seen dramatic evolution in the way that carbon stabilization is represented in soil models, moving away from predefined turnover of carbon based on its quality, towards vertically resolved models where decomposition is dependent on microbial substrate availability: The latter can, for example, be limited by sorption to minerals. The partitioning of total soil carbon between mineral association and presumably unprotected carbon is expected to determine its sensitivity to disturbances and influences the soils potential for carbon sequestration. Understanding and predicting how and where carbon accumulates along soil profiles from the litter layer to the subsoil and consequences for carbon stability are therefore pivotal for projecting future soil carbon changes.

Goals and tasks

The work will be based on the application and further enhancement of a soil carbon profile model recently developed at MPI-BGC (JSM), where decomposition is not only modified by temperature and moisture but also the size of the microbial biomass pool, and where the availability of OM is limited by sorption to mineral surfaces up to a maximum sorption capacity. Using perturbed parameter and model structural ensembles, model predictions will be compared with new global datasets on the magnitude and partitioning of SOC between mineral associated and particulate organic carbon. Microbial properties and carbon isotopes (13C, 14C) will be used as additional constraints for carbon turnover in pools and fractions along soil profiles, where available. This will help to elucidate the importance of variables and processes in the model that determine carbon stabilisation (e.g. carbon and nutrient limitation and the maximum sorption capacity) and provide guidance to further model development to improve the representation of important processes as for example (1) soil mixing and carbon transport along the soil profile have to be improved and (2) additional constrains to microbial activity like soil pH, OM quality indicators and resulting shifts in microbial community functions have to be considered. Finally, consequences for predicted changes in soil carbon following planned carbon sequestration measures under scenarios of future climate change and altered disturbance regimes will be evaluated.
The work will involve:
  • model parameterization, sensitivity analyses, and model-data comparison to better understand how the combination of nutrient availability and maximum sorption capacity drive soil OC partitioning
  • model development and enhancement to better understand the roles of (1) OC transport along soil profiles (2) soil pH and organic carbon quality
  • running different global or land use change scenarios
Details and focus will be further substantiated depending also on the candidate’s interest.


We are looking for a highly motivated and team-oriented PhD student interested in a scientific career. The successful candidate should have a broad interest in the drivers of soil carbon storage and turnover, and how those are linked to microbial composition, activity and mineralogy. The project requires a strong background in either or both environmental modelling and/or soil biogeochemical processes, which should be proven by respective courses and a master in geoecology, biogeosciences, environmental sciences, forestry, physical geography, biology or something related. Experience in programming is preferred and motivation to learn Julia useful. Finally, very good oral and written communication skills in English are required.

Working environment

The Max Planck Institute for Biogeochemistry in Jena offers an exceptional dynamic, creative, international and multidisciplinary working environment. The successful applicant will join the Soil Biogeochemistry group, which is encompassing experimental and theoretical work on the persistence and sensitivity of organic carbon in soils, and interactions between biogeochemical cycles of carbon, nutrients and water at all spatial scales. The project will be conducted in collaboration with Sönke Zaehle from the Department Biogeochemical Signals.

Living in Jena

The city of Jena is not only famous for its high-tech industry, internationally renowned research institutions and a modern university, but also for its beautiful natural setting in the Saale valley with its steep limestone slopes. The climate is mild, and a large variety of plants grow in the close surroundings, including wine grapes and wild orchids. The city of Jena has a large active student scene supporting a diverse cultural life.

The Max Planck Society seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply. The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.

For further information, please contact Marion Schrumpf (

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