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

本研究旨在通过亚微米分辨率的土壤元素/同位素组成和土壤有机和矿质组分的三维关联分析，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质为微团聚体的形成提供了重要的核，导致团聚体的区隔结构。因此，在一项新的孵化实验中，我们将测试不同的微聚集体形成机制，这些微聚集体是由作为有机核的不同有机物输入（即溶解的有机物、颗粒植物残留物或微生物坏死块）引发的。我们还打算利用我们的分析方法来揭示土壤微团聚体的形成，从黄土壤层的天然土壤材料和研究单位的有机质枯竭田间试验。我们将特别关注NanoSIMS的分析能力，以共同定位有机物质和矿物质的封存/积累，并量化它如何影响异质土壤微结构。这些空间上明确的数据将通过大规模测量来补充，例如13C-NMR光谱来表征有机物的化学成分。收集到的数据将使我们能够确定和量化颗粒表面不同部分对土壤结合有机碳、水储存和运输功能以及微生物栖息地的作用。开发确定的机制关系将形成在研究单元中开发的定量模型的一个组成部分。

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.