Exploration and modeling of the transport of mobile organic substances in the topsoil-subsoil-aquifer continuum

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Mobile organic particulate substances (MOPS), which comprise among others organic (ma-cro)molecules, plant residues, organo-mineral aggregates, and (micro)organisms are the neglected component of the soil carbon cycle not only in agricultural soils. Once generated in the topsoil, MOPS transport into deeper zones may not only fuel the subsoil foodwebs but also contribute to their diversity. Results of the first phase suggest that MOPS release is trig-gered by singular events, while transport is governed by preferential flow with particular im-portance of biopores. Our main foci are the mechanistic understanding and numeric model-ling of the release and transport of MOPS and the elucidation of their role for the carbon-flow in the topsoil-subsoil-aquifer-continuum of agricultural soils. Our objectives are (i) to charac-terize the MOPS spectrum including (micro) organisms along the vertical flowpath, (ii) to quantitatively asses water and MOPS dynamics as a function of external forcings and hy-draulic conditions, (iii) to investigate the role of biopores, the hydraulic conditions and their interplay with climatic/anthropogenic factors, and (iv) to model water and MOPS dynamics, thereby contributing to a “unified foodweb” model. Central to the lab and field experimental approach is the exploration of the water and MOPS dynamics in response to external forcing (climate, orbital, anthropogenic) and as a function of the input of carbon via MOPS by crop type, fallow times, and tillage operation. With our research, we will contribute to an improved quantitative understanding of the role of MOPS for carbon flow and diversity in subsoil food-webs.