Differentiating the roles of organic nuclei and mineral surfaces in the formation of soil microaggregates by exploring their elemental and isotopic label composition

通过分析土壤微团聚体的微空间元素/同位素组成以及土壤有机和矿物成分在亚微米分辨率下的三维组合，我们旨在阐明土壤微团聚体形成的控制过程和机制。我们认为，进入土壤的不同形式的有机物质为微团聚体的形成提供了重要的核，从而导致了团聚体的分区结构。因此，在一项新的培养实验中，我们将测试作为有机核的不同有机物输入所引发的微团聚体形成的不同机制，即溶解有机物、植物颗粒残留物或微生物坏死体。我们还打算通过将我们的分析方法应用于研究单元的黄土土壤序列和有机质耗竭野外试验中的自然土壤材料，来揭示土壤微团聚体的形成。我们将特别关注NanoSIMS的分析能力，以共同定位有机质和矿物的封存/累积，并量化它如何影响非均质土壤微结构。这些空间上清晰的数据将得到大量测量的补充，如13C-核磁共振光谱分析，以表征有机物的化学成分。收集到的数据将使我们能够识别和量化颗粒表面的不同部分对土壤结合有机碳的功能、其水储存和运输功能以及作为微生物栖息地的贡献。已确定的机械关系将构成研究单位建立的定量模型的组成部分。

With this proposal we aim to elucidate governing processes and mechanisms for the formation of soil microaggregates by analyzing the microspatial elemental/isotopic composition and the three-dimensional association of organic and mineral soil components at submicron resolution. We suggest that the different forms of organic matter that enter soils provide important nuclei for the formation of microaggregates leading to a compartmentalized architecture of aggregates. In a new incubation experiment we will therefore test the different mechanisms for microaggregate formation as initiated by different organic matter inputs that serve as organic nuclei, i.e. dissolved organic matter, particulate plant residues, or microbial necromass. We also intend to reveal soil microaggregate formation by applying our analytical approach to the natural soil materials from the loess pedosequence and the organic matter depletion field trial of the research unit. We will specifically focus on the analytical power of NanoSIMS to co-localize the sequestration/accrual of organic matter and minerals and quantify how it influences the heterogeneous soil microarchitecture. These spatially explicit data will be supplemented by bulk scale measurements, such as 13C-NMR spectroscopy to characterize the chemical composition of organic matter. The data collected will enable us to identify and quantify the contribution of distinct parts of the particle surfaces for the functions of soils for binding organic carbon, their water storage and transport function and as habitats for microorganisms. The developed identified mechanistic relationships will form an integral part of the quantitative model developed in the research unit.