PhD project: How elevated carbon dioxide affects soil carbon turnover and nutrient mobilization by modifying interactions between plants and soil organisms
International Max Planck Research School for Global Biogeochemical Cycles
In cooperation with the Friedrich Schiller University Jena, the Max Planck Institute for Biogeochemistry houses a unique and flexible research program that grants German and foreign students a broad selection of learning opportunities while still maintaining a research focus.
The IMPRS-gBGC offers a PhD program specializing in global biogeochemistry and related Earth System sciences.
Climate: Past, Present & Future (CL)
Soil System Sciences (SSS)
by Marion Schrumpf , Beate Michalzik , Sönke Zaehle
Elevated carbon dioxide increases photosynthesis rates of plants but allows them only to produce more biomass, if an equivalent amount of nutrients can be taken up from the soil. Availability of nutrients like nitrogen, in many soils also phosphorus, is dependent on their release during the mineralization of soil organic matter. Plants are able to increase nutrient uptake by investing into a larger root biomass, into associations with mycorrhizal fungi or by stimulating the activity of the decomposing microbiome via root exudates or direct exudation of extracellular enzymes. As a consequence, increased turnover of soil organic matter and native soil carbon losses (priming effect) were anticipated and sometimes measured under elevated carbon dioxide. The environmental and plant-specific controls of this response are however still unresolved.
We use tree mesocosms to study how elevated carbon dioxide changes carbon assimilation and allocation to different plant tissues, mycorrhizal fungi and soils. By continuously labelling plant-derived carbon with 13C, or by pulse labelling we are able to study the fate of recently assimilated carbon in plants and the soil as well as to distinguish between plant and soil derived carbon in respired carbon dioxide. The return of investment in terms of organic matter derived nitrogen uptake can be quantified by adding 15N-labelled litter.
Guiding questions of the PhD could be:
- Does increased plant demand for nutrients drive belowground carbon allocation of plants and rhizosphere priming under elevated carbon dioxide?
- Do different tree species and mycorrhizal fungi respond similarly?
- Which microbial and biogeochemical processes are modified by rhizodeposits under elevated carbon dioxide and how do they affect soil carbon stability?
- How are these modified by drought or rising temperatures?
We are looking for a highly motivated and team-oriented student interested in a scientific career. The successful candidate should have a broad interest in how global change is affecting ecosystem carbon fluxes and interactions between carbon and nutrient cycles. This requires an integrated approach, where responses at the plant, microbial and soil/geochemical level have to be considered. Accordingly, a background in all these disciplines, proven by a master in geoecology, environmental sciences, biology, forestry or something related is desirable.
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.
The Max Planck Institute for Biogeochemistry in Jena offers an exceptional dynamic, international and multidisciplinary working. The successful applicants will join a creative, international team led by Marion Schrumpf and Sönke Zaehle, encompassing experimental and theoretical work on the role of the biogeochemical cycles of carbon, nutrients and water at all spatial scales. The project will profit strongly from collaborations with the highly interdisciplinary Soil Science Department of the Friedrich Schiller University in Jena, led by Prof. Beate Michalzik. 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.