Mineral surfaces as hotspots for microbes and element cycling in the Biodiversity Exploratories

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The stabilization of organic matter (OM) and nutrient retention in soils is determined by their interactions with minerals surfaces. On minerals, reactive surfaces meet with microbial life to form the so-called mineralosphere, which is characterized by intense and complex biotic and abiotic interactions. The interplay of microbial colonization, and sorption and release of organic matter and nutrients cause continuous changes and transformations within the mineralosphere, with immediate consequences for carbon and nutrient storage and availability in soil. The trajectories of these developments in response to environmental and ecosystem conditions are hardly understood. The proposed project will take the unique opportunity of studying pristine mineral samples (illite, a clay mineral, and goethite, an iron oxide) being exposed to ambient soil conditions at all experimental plots of the Biodiversity Exploratories since 2015. We aim at exploring the co-occurrence of mineral-associated microbial communities, organic matter, and nutrients as driven by land use and biodiversity in a coordinated, interdisciplinary approach. After an exposure time of five years we will sample mineral cyclinders as well as surrounding soils. These will be analyzed with a suite of complementary, carefully selected state-of-the-art surface-sensitive, biogeochemical, isotopic, mineralogical, and microbiological methods. We hypothesize that type and intensity of land use and biodiversity affect: (1) the accumulation and quality of mineral-associated organic matter, (2) the contribution of plant and microbial sources to mineral-associated organic matter, (3) the patterns of microbial communities emerging in the mineralosphere, (4) the preservation mechanisms of mineral-associated organic matter, (5) the nutrient accumulation in the mineralosphere, and (6) the soil depth-related differences in mineralosphere. This collaborative approach will allow for the first time in-depth insight into developing mineralospheres under natural environmental conditions.