In this session we would like to explore the current progress in understanding the role of soil microorganisms in SOM dynamics, and the consideration that SOM supply is a result of dynamic interactions between living and dead organic matter. Do soil microorganisms control the balance between both the formation of SOM and its mineralisation? It is widely accepted that the decomposition of soil organic matter (SOM) is driven by microbially-mediated biogeochemical processes which control soil C losses through CO2 release to the atmosphere. However, the abiotic controls on decomposition are rarely explored. Similarly, the idea that the stabilisation of SOM is also driven by microbial activity through the formation of humified substances is a matter of intense debate as physicochemical processes are now favoured which are not usually linked with microbial activity.
This session will focus on new methodological and modelling approaches for identifying and quantifying SOM formation and decomposition and the consequences for C dynamics from the rhizosphere to soil profile scale. Studies tracing C pathways in soil and evaluating their dependence on biotic or abiotic processes are appreciated. Contributions revealing the role of microbial re-utilization of plant-derived C in soil C sequestration are particularly encouraged, especially within the context of climate and land-use change effects on plant C dynamics in natural and agricultural ecosystems.