Large fluxes of solar energy conserved in organic matter pass through soil as conduit from primary production to mineralisation. Soil organisms are channelling the flux, are fuelled by the energy, and contribute by their bio- and necromass. Previous research targeted either biogeochemical turnover processes or the microbiome but rarely linked both. Microbial biomass and its necromass were identified as major constituents of soil organic matter (SOM) and highly counterintuitive results were found on the relation of the microbiome to the systems boundary conditions provided by water, oxygen, nutrients, and minerals etc. A major deficit is that soils are currently not considered as energy driven open systems. Energy is the `fuel´ of all animate systems including soils in which microbial biomass consume the organic matter and energy input. With the necromass plus other SOM it constitutes carbon and energy containing intermediates.

The general aim of SoilSystems is to link energy and matter turnover and fluxes in soils to functional and structural biodiversity. SoilSystems proposes a systems ecology concept for linking balances of changes of Gibbs energy and heat production to organic matter turnover and the microbiome. This concept will be applied in model experiments with various bulk soils and isotope labelled substrates with defined energy supply and molecular structures in order to evaluate losses, efficiencies, and the modes of energy and matter retention.

This presentation gives an overview on the recently started research priority program SoilSystems, funded by the German Research Foundation. The planned research will be outlined that is aimed to elucidate microbial processes driving organic matter along energy use channels, thereby converting easily degradable detritus molecules to microbial biomass and finally long-term stabilised necromass. Thermodynamic principles are generally valid for the Earth system and thus also for soils; however, only few studies exist regarding energy use and maintenance (energy budgets) of microbiomes related to carbon use and ecosystems in soil.

SoilSystems aims to answer the key-question: What drives the interrelated energy and matter fluxes in soil systems exemplified by carbon turnover and storage? The microbiome, energy input, mineral and boundary conditions, and how do they interact?