PhD project offered by the IMPRS-gBGC in July 2022

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Microbial trait-based ecology to link soil communities to carbon cycling

Gerd Gleixner , Erika Kothe , Ashish Malik

Project description

Soils harbour an immense diversity of microorganisms that are critical to ecosystem functioning. Microbial communities in soil are significant drivers of soil carbon cycling – they control the fate of recent plant carbon inputs and determine the stability of assimilated carbon. Our work has shown that higher microbial growth yield, with a greater proportion of substrate allocated to biosynthesis, increases the ability of communities to store carbon in soils through necromass-mineral interactions.
We know that land use intensity impacts soil abiotic factors such as moisture levels and resource availability which can affect microbial growth yield and hence carbon sequestration. Under resource limitation and reduced moisture, typical of intensive land use soils, microbial investment in growth could be lower, because resources are allocated towards substrate acquisition and stress tolerance. These trade-offs, with lower biomass production resulting in lower organo-mineral stabilisation, reduce soil carbon accrual. The project will test the hypothesis that increasing plant-derived resource inputs (thereby reducing resource limitation) and by improving microhabitat conditions (thereby reducing stress) increases microbial growth yield in degraded soils leading to greater carbon stabilisation.
Microbial traits will be linked to carbon cycling processes in soils using a combination of field assessment and targeted mesocosm experiments. We have access to a well-replicated site, Jena Biodiversity Experiment, with local multiple treatments of decreasing land use intensity: continuous arable, meadow with and without plant inputs and unimproved grassland. Soils with contrasting land use in close proximity are ideal to limit climatic and edaphic variability and will be used to isolate the effects of land use intensification.
First, the differences in fungal and bacterial density, diversity and function across land use intensity gradients will be assessed using a combination of phospholipid fatty acid analyses and whole genome shotgun sequencing. PhD student will then perform a mesocosm experiment using artificially created gradients of resources and moisture availability (a simple cross-factorial design reducing the complexity of land use gradients) to test the novel hypothesis. 13C-labelled plant organic matter will be used as a substrate in mesocosm experiments to monitor decomposition and stabilization rates. Such a combination of genomic sequencing, analytical chemistry and stable isotopic approaches in field and lab experiments will allow the student gain a range of unique technical skills.

Requirements

Applications to the IMPRS-gBGC are open to well-motivated and highly-qualified students from all countries. Prerequisites for this PhD project are:
  • A Master’s degree in Biogeochemistry, (Geo)Ecology, (Micro)Biology, Chemistry, Environmental sciences or other related sciences
  • Lab skills: microbiology methods, molecular techniques (PCR, qPCR, RNA/DNA extraction, …)
  • Experience in phospholipid fatty acid analyses, genome shotgun sequencing, or stable isotope measurements (desirable)
  • Computational skills: processing and analyzing large data sets, statistics
  • Excellent oral and written communication skills in English, knowledge of German is an asset

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.


>> more information about the IMPRS-gBGC + application