Mineralization, stabilization, and re-mobilization of organic substances in microhabitats - the role of microorganisms in carbon and energy flows (MicroHabits)

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The importance of soil microorganisms for carbon mineralization and stabilization is increasingly recognized and described through the concept of the microbial C pump. However, the underlying mechanisms and controls within this framework are to date poorly understood and most studies in the past have focused only on specific aspects of C dynamics. We plan to fill this gap by linking the concept of the microbial C pump to three important microhabitats to understand the carbon flow during phases of C mineralization (detritusphere), C stabilization (mineral surfaces), and C re-mobilization (earthworm casts). The new challenge for the current proposal is to improve our conceptual understanding by linking C and microbial dynamics to energy fluxes and thermodynamic principles. We will address this challenge in a series of microcosm experiments in which we will follow 13C and energy flow from cellulose and maize litter into different pools combining isotopic (full mass balances including 13Cmic, 13C PLFA,13C amino-sugars,13Corg,13C-EOC) with calorimetric (heat production) and molecular biological (qPCR, Illumina PCR amplicon sequencing, DNA-SIP) methods. Analyses of nematodes will demonstrate C and energy flow into higher trophic levels. One part of our proposal is one of three complementary core experiments, which together cover the entire potential data space of soils, substrates, and boundary conditions proposed in the SPP. The data obtained in these core experiments will be available to the whole SPP. In conclusion, our project will underline the importance of specific microhabitats for the microbial role of C stabilization in soil.