Driver of microbial nutrient turnover in mineral soil, rhizosphere and forest floors

森林地表是矿质土壤与大气的分界线，对养分从地表向矿质土壤的输送起着重要作用。FF特性影响养分浓度和质量以及氧气和水的可用性。微生物对营养物质的周转受生态系统营养物质化学计量水平和单个微生物遗传操纵子结构的调节，这些微生物追求不同的策略来调节营养物质的有效利用。因此，养分供应和群落组成是密切相关的。因此，营养物质的可用性和栖息地结构的变化，因为增加温度反馈微生物群落的分类和功能组成以及营养相互作用。我们的项目的目的是了解在不同的P和温度制度下，非生物FF特性与微生物群落组成的相互作用。我们假设，土壤有机质和根系分泌物的质量和数量，以及营养化学计量（C，N，P，阳离子）驱动微生物转化氮和磷的潜力，并确定与其他生物区系（真菌，动物和树木）的营养相互作用。此外，细菌和营养热点的N和P的空间相关性是可能的。为了验证这些总体假设，我们将使用实验和分析方法相结合。我们将首先确定微生物N和P周转的关键参与者和过程。因此，我们将采取样品在不同的FF层和矿物土壤从12个山毛榉为主的网站显示梯度的P浓度和T和山毛榉，枫树和云杉的根际从三个网站与对比P的有效性。 为了确定微生物群落对FF特性和树种的长期适应性，我们将联合收割机宏基因组学方法用于确定关键过程和参与者，随后将qPCR用于量化不同设置下的主要关键参与者。此外，我们将调查根的定植微生物参与磷周转FF和矿质土壤中使用CARD-FISH。 第二，我们将使用不同的实验方法：（i）确定土壤矿物的作用，为P的有效性和微生物P的收购策略的框架中的垃圾/OF袋实验，额外的初级和次级矿物将被添加到垃圾或OF材料。(ii)在动物排除实验的框架内，解开FF动物和微生物的相互作用。除了开发的定量工具，我们还将分离细菌参与溶解矿物质结合P的垃圾/OF袋实验，以重建P基因的操纵子结构。基于不同的方法，我们将能够确定微生物群落组成的主要驱动因素和在不断变化的环境条件下对FF营业额重要的衍生服务。

The forest floor (FF) is the boundary between mineral soil and the atmosphere and is thus important for nutrient transport from the surface to the mineral soil. FF properties influence nutrient concentrations and quality as well as oxygen and water availability. The turnover of nutrients by microorganisms is regulated on the level of nutrient stoichiometry of ecosystems and genetic operon structure of single microorganisms who pursue different strategies to regulate efficient nutrient use. Thus, nutrient availability and community composition are closely interlinked. Consequently, changes in nutrient availability and habitat structure because of increasing temperature feedback on microbial communities in terms of their taxonomic and functional composition as well as trophic interactions. The aim of our project is to understand the interplay of abiotic FF properties with the microbial community composition under different P and temperature regimes. We hypothesize that the quality and quantity of soil organic matter and root exudates as well as nutrient stoichiometry (C, N, P, cations) drives the microbial potential to transform nitrogen and phosphorus and determines trophic interaction with other biota (fungi, fauna and trees). Moreover, spatial correlation of bacteria and nutrient hotspots of N and P are likely. To test these overarching hypotheses we will use a combination of experimental and analytical approaches. We will first identify key players and processes of microbial N and P turnover. Therefore, we will take samples in different FF layers and the mineral soil from 12 beech dominated sites displaying gradients of P concentrations and T and in the rhizosphere of beech, maple and spruce from three sites with contrasting P availability. To identify the long-term adaptation of microbial communities to FF properties and tree species we will combine metagenomics approaches for the identification of key processes and players and subsequent qPCR for the quantification of dominant key players under different settings. Moreover, we will investigate the colonization of roots by microbes involved in P turnover in FF and mineral soil by using CARD-FISH. Second, we will use different experimental approaches: (i) To identify the role of soil minerals for P availability and microbial P acquisition strategies in frame of a litter/OF bag experiment where additional primary and secondary minerals will be added to litter or OF material. (ii) To disentangle the interplay of FF fauna and microorganisms in frame of a fauna exclusion experiment. In addition to the developed quantification tools, we will also isolate bacteria involved in the solubilisation of mineral bound P of the litter/OF bag experiment to reconstruct operon structures of P genes. Based on the different approaches we will be able to identify major drivers of microbial community composition and derived services important for FF turnover under changing environmental conditions.