Carbon and energy flow in the soil microbiome – functional groups, activity and interactions in trophic networks

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Soil ecosystems are driven by carbon (C), nutrient and energy flows, which are essential for biogeochemical cycles. In particular, the organisms in the soil microbiome are channeling these fluxes. However, only few attempts were made to link microbial traits and functional groups of faunal grazers to heat and CO2 production (i.e. thermodynamics). The major goal of the SPP “SoilSystems” is to integrate energy-based descriptions with biotic interactions to gain a systemic concept for turnover processes in soil. Within this framework the proposed project will assess C and energy flux in the soil microbiome with the focus on trophic networks. The structure and function of the micro-food web will be assigned using nematodes as model group. Their metabolic footprints serve as trait based measurement for production and grazing activity of higher trophic levels. With their high abundance as well as species and trophic diversity nematodes form a key group in microbial-faunal interactions. Three major questions will be addressed by the project: (1) What is the impact of different functional groups of grazers as well as their interactions (e.g. resource competition, intraguild predation) on the C and energy flux in the bacterial and fungal channel? (2) How does the soil environment (i.e. soil type, soil organic matter content, substrate, moisture, temperature) affect grazer diversity and activity, and the C flux to higher trophic levels? (3) What role play microorganisms in the gut of faunal grazers for C allocation from resources and do they form a “hidden” C channel? Together with collaborating projects, a combination of PLFA-, DNA- and Protein-SIP (Stable Isotope Probing) as well as metagenomics will be performed, providing an exceptional level of detail on the identities, succession and functional niche partitioning of key microbiome members in the detritusphere. Overall, the proposed project will deliver a systemic view on the processes in the micro-food web, relating C turnover (pathways) and changes in energy (heat production) and to the microbiome (activity, functional groups, trophic interactions).