Organic matter stabilization processes in subsoils: Impact of small-scale physical heterogeneity of soil particle interfaces

底土中的有机物稳定过程：土壤颗粒界面小尺度物理异质性的影响

• 批准号: 233430855
• 负责人: Professor Dr. Jörg Bachmann
• 金额: --
• 依托单位: Institut für Bodenkunde (IFBK)
• 依托单位国家: 德国
• 项目类别: Research Units
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/233430855?language=en
• 关键词: Organic; matter; stabilization; processes; subsoils

The spatial separation between degraders and substrate is considered as a major factor controlling subsoil organic carbon variability, stability and dynamics. Processes in soils take place at solid particle surfaces, emphasizing the relevance of interfacial properties for physical, chemical and biological processes due to large solid-surface to mass ratios. However, mostly ignored is at present the importance of the solid interfaces that may enhance spatial and temporal heterogeneity in soils. Accordingly, it still needs to be answered which soil-specific factors are governing the carbon budget in subsoils and what the respective scales for capturing stabilizing mechanisms are.One innovative element of subproject P4 is the development of a flow cell soil sampling technique to assess small-scale soil properties and processes and to reduce 3-dimensional transport processes to quasi 2-d which allows a direct link between soil heterogeneity and processes of interest. Flow cell sampling provide the option to sample within one frame (i.e. 8 x 12 cm) simultaneously up to 5 undisturbed soil slices as a sandwich. Due to the small thickness of a single sandwich layer (5 to 10 mm), undisturbed samples can be used as quasi-replicates. Two approaches will be made to link interfacial properties with chemical and biological processes in order to identify biological hot spots. Using a cascade of flow cells of different depths, a virtual soil profile will be simulated by connected cells and depth-dependent breakthrough behavior of infiltrating DO13C solution can be analyzed. Using single flow cells, physical, chemical, and biological properties can be mapped on the undisturbed soil particle interfaces. Two central questions are addressed: (i) whether and how are hotspots of microorganisms activity related to either physical or physicochemical properties of the spore space and (ii) what are the specific physical and interfacial interactions between soil and roots with special focus on root stage (root density, morphology) and rhizosphere wettability. To answer these questions, mapping of various parameters will be done in close cooperation with partner projects. Physicochemical behavior of the interfaces is assessed by wettability measurements (sessile drop contact angle determination, ESEM condensation experiments), whereas soil organic matter content and quality, i.e. hydrophobicity index derived by DRIFT-mapping,is assessed by calibrated MIR spectroscopy. Biological parameters (respiration, exo-enzyme activity, decay of 14C labeled glucose) will be measured to relate interfacial properties with respective biological responses. Flow cells will be sampled on 3 sites with different parent material in close cooperation with other projects. Overall, this study aims to offer new insights on the assessment and the relevance of small-scale structural and interfacial heterogeneity for SOM stabilization processes in less structured forest subsoils.

降解物和底物之间的空间分离被认为是控制底土有机碳变异性、稳定性和动态性的主要因素。土壤中的过程发生在固体颗粒表面，强调由于较大的固体表面与质量比，界面性质与物理、化学和生物过程的相关性。然而，目前最被忽视的是固体界面的重要性，它可以增强土壤的空间和时间异质性。因此，仍然需要回答哪些特定于土壤的因素在控制底层土壤的碳收支，以及捕捉稳定机制的相应尺度是什么。P4子项目的一个创新要素是开发流动细胞土壤采样技术，以评估小尺度土壤属性和过程，并将三维传输过程减少到准二维，这允许土壤异质性和感兴趣的过程之间的直接联系。流动池采样提供了在一帧(即8 x 12厘米)内同时采样多达5片未受干扰的土片作为夹层的选项。由于单层夹心层的厚度很小(5-10 mm)，原样可以用作准复制。将采取两种方法将界面属性与化学和生物过程联系起来，以确定生物热点。利用不同深度的流动单元组成的叶栅，用连通单元模拟虚拟土壤剖面，分析渗透DO13C溶液随深度变化的穿透行为。使用单一流动单元，可以将物理、化学和生物特性绘制在未受干扰的土壤颗粒界面上。讨论了两个核心问题：(I)微生物活动的热点是否以及如何与孢子空间的物理或物理化学性质有关；(Ii)土壤与根之间的具体物理和界面相互作用是什么，特别是根部阶段(根密度、形态)和根际润湿性。为了回答这些问题，将与伙伴项目密切合作，绘制各种参数的地图。界面的物理化学行为通过润湿性测量(固着液滴接触角测定、环境扫描电子显微镜凝聚实验)来评估，而土壤有机质含量和质量，即通过漂移图得出的疏水性指数，则通过校准的MIR光谱来评估。将测量生物参数(呼吸作用、外酶活性、14C标记葡萄糖的衰变)，以将界面属性与各自的生物响应联系起来。将与其他项目密切合作，在3个不同母质的地点对流动单元进行采样。总体而言，这项研究旨在为结构性较差的森林底土中SOM稳定过程的小尺度结构和界面异质性的评估和相关性提供新的见解。