PhD project offered by the IMPRS-gBGC in January 2022

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Coupled soil and vegetation dynamics under climate change: a model-data integration project with mature forest CO2 experiments

Katrin Fleischer , Sönke Zaehle , Lin Yu , Alberto Quesada , Belinda Medlyn

Project description

Global forests are responsible for a large fraction of the terrestrial carbon sink, currently partially offsetting anthropogenic CO2 emissions and thereby slowing the atmospheric CO2 growth rate. However, future forest functioning and resilience in a changing climate is uncertain, due to adverse effects of higher temperatures, drier air and changes in precipitation. Elevated atmospheric CO2 has ameliorating effects on forest productivity, but the extent to which these may buffer adverse climate impacts is moderated by the availability of soil nutrients. However, the underlying belowground processes are not yet fully understood and quantified. The land carbon feedback to elevated CO2 thus remains a key scientific question to be solved for reliably projecting future climate.
Ecosystem-scale manipulation experiments with CO2 treatments offer a unique possibility to integrate process-based knowledge in models and constrain their predictions (Medlyn et al., 2015). In collaboration with partners in Australia and Brazil, this PhD project aims to integrate experimental observations from the new generation of mature forest FACE experiments into a state-of-the-art process-based model (QUINCY-JSM) to improve representations of coupled carbon and nutrient dynamics (Thum et al., 2019; Yu et al., 2020).
Specifically, the project will deal with how carbon allocation of plant assimilates belowground can affect ecosystem nutrition, carbon storage, and forest resilience to climate variability. An increased flux of carbon belowground would have the potential to change the soils’ carbon balance under eCO2, either leading to enhanced soil respiration from microorganisms or to stabilization of soil carbon. Thereby, plant carbon exudation in turn may potentially stimulate or decrease the availability of soil nutrients to plants and thereby plant growth. Plant-soil-microbial interactions are poorly represented in global models, to date, but may lead to unforeseen non-linear feedbacks of the land carbon cycle to climate change. The project will develop model representations of plant exudation effects constrained by plant-soil-microbial observations from FACE experiments, to be applied in global models in order to improve projections of climate change.

Working group

The PhD candidate will be based in the Terrestrial Biosphere Modelling group in the MPI-BGC Signals department (Dr. Sönke Zaehle and Dr. Katrin Fleischer), and will closely work with collaborators in Sweden (Dr. Lin Yu, soil modelling), Australia (Prof. Belinda Medlyn, EucFACE), and Brazil (Dr. Alberto Quesada, AmazonFACE), where ecosystem-scale CO2 enrichment experiments are being conducted in mature forests.

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 ecology / plant science / Earth system science / environmental science or engineering, physics or a computational science, or similar,
  • Experiences with dynamic numerical modelling,
  • Knowledge on global change ecology, ecosystem manipulation experiments, and field observations is an asset,
  • Good programming skills in a modern script language (e.g. Python, R, Julia), or programming language (e.g. FORTRAN, C++), and
  • Good English written and communication skills.
The Max Planck Society (MPS) strives for gender equality and diversity. The MPS seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply. The MPS is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.

View of EucFACE experiment, Sydney, Australia © Katrin Fleischer (left), View of central tower AmazonFACE plot 1, Manaus, Brazil © <a href="https://amazonface.inpa.gov.br/en/index.php">AmazonFACE</a> (right)
View of EucFACE experiment, Sydney, Australia © Katrin Fleischer (left), View of central tower AmazonFACE plot 1, Manaus, Brazil © AmazonFACE (right)


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