Estimating Effects of Microbial Functional Diversity on Marsh Ecosystem Carbon Balance

Microbial processes are known to substantially influence carbon dynamics in soil, which can be altered by changes in community structure. However, the explicit representation of soil microbial diversity in ecosystem models is still in need of improvement. Model-based estimates are crucial to quantify links between functional diversity of soil microbes and ecosystem functioning, in particular soil carbon turnover and storage.

Incorporating functional diversity is well established in vegetation models and is the methodological basis for the presented approach. Trait-based modelling is used here to directly connect community structure to corresponding carbon fluxes and thereby enable implications for the marsh soils of the Elbe estuary, which represent an important carbon sink. Modelled microbial diversity is based on multiple functional types that vary in key traits related to carbon cycling. The simulated microbial community develops population dynamics based on the environmental conditions, leading to selection of certain functional types. This allows predictions of the abundances and potential shifts in the community structure resulting in altered soil carbon dynamics. Parameter values for the microbial model are derived from empirical data and a specifically developed experimental approach that investigates microbial growth and uptake kinetics. We assess the impact of functional diversity on carbon dynamics in marsh soils by comparing soil carbon fluxes in the model with and without explicitly modelled microbial functional diversity. The findings of the study are expected to enhance projections of soil organic carbon storage in wetland ecosystems as well as emphasizing the role of microbial functional diversity for ecosystem carbon dynamics.