Soil microorganisms and plants are key players in the production and breakdown of organic matter, and together control global biogeochemical cycles of carbon, nitrogen and phosphorus. TER, the Division of Terrestrial Ecosystem Research, aims to advance our fundamental understanding of how plants and soil microorganisms respond to, and in turn shape, their abiotic and biotic environment, and to determine the consequences for the functioning of Earth’s ecosystems.
Research Mission
Primarily dedicated to basic research, TER addresses pressing environmental issues, such as the impact of climate and land-use change on ecosystem functioning and the role of soils in the global carbon cycle and in food security. In doing so, we work on scales from µm (i.e. the scale at which microbes operate) to the biosphere (i.e. where plant and microbial processes become evident), and in ecosystems spanning the Arctic tundra to tropical rainforests. We integrate this scale of thinking with state-of-the-art methods, including stable isotope tracing and biomarker fingerprinting, and are developing novel approaches to estimate gross environmental processes with isotope pool dilution techniques.
We are strongly committed to conduct world-leading research in a motivating and intellectually stimulating environment, and to train our students to become independent and internationally competitive scientists who enjoy research and contribute to society as conscientious citizens.
Research Projects
Modeling emergent phenomena of complex microbial communities
Microbial soil organic matter transformations are traditionally investigated from a bird’s eye view, that means at scales that are considerably larger than those relevant to soil microbes, in both empirical and modeling studies. This approach constrains our understanding of the underlying mechanisms, and consequently hampers the prediction of decomposition rates under changing environmental conditions.
The microbial decomposer system, which is characterized by nonlinear interactions between individual microbes in a spatially structured and chemically heterogenous environment is argueable a complex dynamic system. It is well known that in complex dynamic systems, interactions among individuals at the microscale can lead to an ‘emergent’ system behavior at the macroscale, which cannot be derived directly from the traits of the individual agents. Such an emergent behavior, however, can have a crucial influence on mechanisms of microbial soil organic matter decomposition.
Aiming to capture the complex and dynamic nature of the soil’s decomposer system, I developed an individual-based microbial C and N turnover model, which simulates competitive and synergistic interactions between functionally different microbes in a spatially structured micro-scale environment. Based on this ‘bottom-up’ approach, our model allows to explore possible emergent behaviors of the decomposer system based on individual microbial traits.
Results from this modelling work have led to interesting insights into mechanisms that may drive soil C and N cycling: It showed, for instance, that functional diversity of microbes can alleviate stoichiometric constraints during litter decomposition (Kaiser et al., Ecology Letters, 2014) and that social interactions among microbes can lead to N retention and organic matter build-up in soils (Kaiser et al, Nature communications, 2015). We also found that the well-known Birch effect (i.e. the sudden release of a large amount of CO2 after rewetting of dry soil) can be explained by a combination of relieving diffusion limitations of labile substrates after rain and physiological responses of microbes to drought (Evans et al, Soil Biology and Biochemistry, 2016).
Taken together, our modeling results show that the soil has a large potential for self-regulation and that the response of the soil system to environmental change may not be as predictable from first-order rate decay equations as is often assumed. We currently apply the model to investigate how microbial physiological traits influence C and N storage at the soil’s steady state, and the underlying mechanisms of the Priming effect. We are aiming on developing experimental approaches that allow us to test hypotheses generated by the model.
