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

尽管在过去的二十年中已经发表了大量关于表土微生物群落对植物生长和性能的作用的结果，但对底土系统中微生物在养分动员中的作用几乎一无所知。此外，目前还不清楚生活在土壤中40厘米以下的微生物是否会受到农业管理的影响。这两个问题都应在本项目的框架内加以解决。因此，在该项目的第一阶段，生活在不同生境的底土微生物群落的整体表征应具有高通量测序的特点。这些结果将首次深入了解生活在深层土壤中的微生物，并将为开发分子工具以测量参与田间氮和磷周转的微生物的丰度和多样性以及微观实验奠定基础。通过对田间试验样品的分析，可以明确底土中微生物群落及其活动的时空异质性。此外，热点（钻圈和根圈）在驱动微生物性能中的作用应予以澄清。主要是氮在底土中如何代谢的问题。通过用13C标记根分泌物以及粪便，应在中央微观实验中分析根际和底土钻际中不同碳量和质量在刺激微生物群落中的作用，通过遵循微生物区系中的13C标记。这种方法将有助于确定可能的主要因素，指导细菌，真菌和古菌在更深的土壤层。

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.