Assoc.-Prof. Dr. Christina Kaiser

Soil Microbial turnover of soil organic matter is responsible for the largest flux of C from land to the atmosphere. Its underlying mechanisms, however, are not fully understood, making it difficult to predict its response to environmental change. Microbial decomposition of organic matter requires the concerted action of functionally different microbes. In soil, a huge number of individual soil microbes and fauna interact with each other at the microscale within a dynamic system of pores and aggregates, feeding back on their community structure and physical environment. This makes soil a prime example for a complex system. From complex systems science, it is known that interactions among individuals at the microscale can lead to an ‘emergent’ system behavior at the macroscale. Such an emergent behavior, or self-organization, adds a new quality to the system which cannot be derived from the traits of the interacting individuals. Soil organic matter turnover is often investigated or modelled from an ‘aggregated’ view, measuring soil pools and processes in larger, homogenized soil samples, or using models based on aggregated, computable C pools. While this approach gives valuable information on the system’s state and behavior, it cannot easily reveal intrinsic mechanisms leading to emergent system behavior. Exploring the soil from the perspective of complex systems science opens up new possibilities to understand basic mechanisms within the soil microbial decomposer system, which complements other approaches. (picture on the right: soil bacteria colonising a root surface, made within the ROMY project at CIUS/University of Vienna)

In my group, we aim at developing tools, both theoretical and experimental, for investigating the soil system from the point of view of a “soil systems ecology”. Our approach recognizes the need to understand the interactions between individual agents in order to be able to predict the behaviour of the system, following the directive “the whole is something else than the sum of its parts” (Solé and Bascompte, “Self-Organization in complex ecosystems”, 2006). Our aim is to understand if and how mechanisms of microbial C and N cycling in the soil may depend on emergent properties driven by spatiotemporal dynamics of microbial communities and their substrates based on microbial microscale interactions.