Microbial community structure and function in different habitats of subsoils and their role in nutrient mobilization and plant growth (MicroSub)

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Whereas a lot of results about the role of microbial communities from topsoils for plant growth and – performance have been published in the last two decades, almost nothing is known about the role of microbes in nutrient mobilization in subsoil systems. Furthermore it is unclear if microbes living below 40 cm in soil can be influenced by agricultural management. Both questions should be addressed in the frame of this project. Therefore in the first phase of the project an overall characterization of microbial communities living in different habitats of subsoils should be characterized by high throughput sequencing. These results will give a first insight into microbes living in deeper soil layers and will form the basis for the development of molecular tools to measure abundance and diversity of microbes involved in nitrogen and phosphorus turnover in the field – as well as in the microcosm experiments. Analyzing samples from the field experiment should clarify temporal and spatial heterogeneity of microbial communities and their activities in subsoils. Furthermore the role of hotspots (drilosphere and rhizosphere) in driving microbial performance should be clarified. Mainly the question how nitrogen is metabolized in subsoils will be addressed. By labeling root exudates as well as earthworm excrements with 13C the role of different carbon amounts and quality in the rhizosphere and drilosphere of subsoils in stimulating microbial communities should be analyzed in the central microcosm experiment, by following the 13C label in the microflora. This approach will help to identify possible major factors steering bacteria fungi and archaea in deeper soil layers.