The influence of agricultural management practices on microbial functions and networks in biological soil crusts

由于世界人口不断增加，估计到2050年粮食产量必须翻一番。因此，需要通过可持续的管理系统来提高作物产量。耕地的多样性及其连带特征很高。在德国，耕地评估等级(Ackerzahl)显示的值从100(高肥力)到不到30(极低肥力)。特别是阿克扎尔含量较低的土壤，由于质地不佳，容易受到侵蚀。在这些土壤中，在无植被时期形成生物土壤结皮(BSC)对作物生长是有利的。这是由于BSC的关键功能，即固定和周转氮和碳以及排泄EPS，从而增加了其直接附近的土壤养分含量和土壤稳定性。由于平衡计分卡对土壤性质的积极影响，有必要了解土地利用管理对低肥力农田平衡计分卡建立和运作的影响。因此，本项目的目的是从一项最初评估评级很低(25-30分)的农田试验中分析BSC中的微生物组成和功能。在多因素设计中，将分析氮肥、有机肥和耕作制度对微生物EPS产量的影响，微生物EPS产量与有机肥的C输入和微生物氮素周转密切相关，而微生物氮周转又受添加矿物肥的数量的影响。此外，分析将侧重于细菌、古生菌和真菌的关键角色和网络。例如，真菌和细菌之间的良好合作可能会改善细菌通过真菌高速公路向地下地区的运输。为了评估来自不同处理的细菌、古菌和真菌的总体丰度和网络组成的变化，来自不同处理的BSC样本将通过实时定量聚合酶链式反应进行量化，并使用MiSeq技术进行表征。为了描述所涉及的微生物关键角色的功能，将采用元基因组学方法，特别关注氮和胞外多糖(EPS)的周转。获得的分子数据将与土壤化学分析和EPS的组成相关联。

As the world population is continuously increasing, it is estimated that food production must be doubled by the year 2050. Therefore, an increase in crop yield connected with a sustainable management system is needed. The diversity of arable land and their connected characteristics is high. In Germany the arable assessment rating (Ackerzahl) revealed values from 100 (highly fertile) to less than 30 (very low fertility). Especially soils with a low Ackerzahl are prone to erosion due to their unfavourable texture. In those soils the establishment of biological soil crusts (BSC) during the vegetation free period displays an advantage for crop growth. This is due to the key functions of BSC, which are the fixation and turnover of nitrogen and carbon and the excretion of EPS, which increase soil nutrient content and soil stability in their direct vicinity. Due to those positive effects of BSC on soil properties, there is a need to understand the impact of land use management on the establishment and functioning of BSC in low fertility agricultural fields. Therefore, it is the aim of this project to analyse the microbial composition and function in BSC from an arable field trial with an initially very low assessment rating (25-30). In a multifactorial design the influence of nitrogen fertilization, organic fertilization and tillage regime will be analysed with respect to the microbial EPS production, which is strongly connected to C input by organic fertilization and microbial nitrogen turnover, which in turn is affected by the amount of added mineral fertilizer. Furthermore, the analyses will focus on bacterial, archaeal and fungal key players and networks. As for example a good collaboration between fungi and bacteria might improve the transport of bacteria to subsoil areas via fungal highways. To assess changes in the overall bacterial, archaeal and fungal abundance and network composition BSC samples from the different treatments will be quantified by quantitative real-time PCR and characterised by using the MiSeq technology. To characterise the functions of the involved microbial key players a metagenomic approach will be applied with a special focus on nitrogen and exopolysaccharide (EPS) turnover. The obtained molecular data will be connected with soil chemical analyses and the composition of EPS.