Spatial patterns of organic matter formation in subsoil: Hierarchical preferential flow pathways

底土中有机质形成的空间模式：分层优先流路径

• 批准号: 452510514
• 负责人: Professor Dr. Jörg Bachmann
• 金额: --
• 依托单位: Geographisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/452510514?language=en
• 关键词: Spatial; patterns; organic; matter; formation

Previous results of the Research Unit suggest that decoupling of biological and physical processes by spatial separation of organic matter (OM), microorganisms and extracellular enzyme activity is apparently one of the most important mechanisms leading to the protection and stabilization of litter- and topsoil-derived dissolved organic carbon (DOC) in deeper subsoil layers. The occurrence of preferential flow (PF) paths is supposed to be a major driver for the formation of hot spots of microbial activity and OM transformation and stabilization in subsoil. Consequently, employing the globally unique subsoil observatories at Grinderwald, our new research initiative aims at investigating the spatial patterns of OM formation in subsoil. The following aspects will be covered in the complementary research activity:- Hierarchical preferential flow pathways - Microbial carbon retention and turnover - Nutritional control of microbial hot spot formation and dynamics - Formation of mineral-associated organic matter Our project is the attempt of a multi-scale approach to capture active and less active transport zones in soil. Experimental evidence already confirmed a stable network of PF pathways on the cm to dm scale over years. We assume that this meso-scaled flow heterogeneity can be captured with fluorescent dye irrigation experiments in the field. Subsequent dye-guided sampling will identify locations with systematic differences regarding active or less active flow domains. The newly developed technique to extract undisturbed flow cells (FC) allows a comprehensive analysis of the in situ state by highly resolved measurements and imaging of important physicochemical and microbiological surface properties (e.g. wettability, functional groups, exoenzyme activity on the mm- to cm-scale). Corresponding sampling strategy will allow to quantify nested PF structures. To assess DOC transport and transformation we will simulate flow processes using 13C-labeled DOC. The percolation experiments will be conducted with two undisturbed serial FC under realistic in situ moisture, DOC concentration, flow rate and temperature conditions, simulating the average flux rate at the sampling site during the winter drainage season. The microbial status of soils sampled from active vs. less active transport domains will be compared to investigate differences in microbial community patterns (in cooperation with Kandeler et al.). Here, we aim to achieve a complete 13C mass balance recovery by quantifying 13C (i) adsorbed to the solid phase, (ii) incorporated into microbial biomass, (iii) released as CO2, and (iv) transported as DOC. This approach (in cooperation with all projects) will finally allow to evaluate the importance of micro-PF patterns versus field scale PF pathways to elucidate the mechanisms triggering the spatial pattern of microbial hot spots.

研究小组先前的结果表明，通过有机物（OM）、微生物和细胞外酶活性的空间分离来解耦生物和物理过程显然是导致来自枯落物和表土的保护和稳定的最重要机制之一较深层土层中的溶解有机碳（DOC）。优先流（PF）路径的出现被认为是微生物活动热点形成以及底土中有机质转化和稳定的主要驱动因素。因此，我们的新研究计划利用格林德瓦尔德全球独一无二的地下观测站，旨在研究地下 OM 形成的空间模式。补充研究活动将涵盖以下方面： - 分层优先流动路径 - 微生物碳保留和周转 - 微生物热点形成和动态的营养控制 - 矿物相关有机质的形成 我们的项目是多方面的尝试捕获土壤中活跃和不太活跃的运输区域的尺度方法。实验证据已经证实了多年来从 cm 到 dm 尺度的 PF 通路的稳定网络。我们假设这种细观尺度的流动异质性可以通过现场荧光染料灌溉实验来捕获。随后的染料引导采样将识别在活跃或不太活跃的流域方面具有系统差异的位置。新开发的提取原状流动细胞（FC）的技术可以通过高分辨率测量和重要物理化学和微生物表面特性（例如润湿性、官能团、mm-到cm-上的外酶活性）的成像来全面分析原位状态。规模）。相应的采样策略将允许量化嵌套的 PF 结构。为了评估 DOC 传输和转化，我们将使用 13C 标记的 DOC 模拟流动过程。渗滤实验将在真实的原位湿度、DOC浓度、流量和温度条件下使用两个原状串联FC进行，模拟冬季排水季节采样点的平均通量率。将比较从活跃运输域和不太活跃运输域采样的土壤的微生物状态，以研究微生物群落模式的差异（与 Kandeler 等人合作）。在这里，我们的目标是通过量化 13C (i) 吸附到固相、(ii) 纳入微生物生物质、(iii) 作为 CO2 释放和 (iv) 作为 DOC 运输来实现完整的 13C 质量平衡回收。这种方法（与所有项目合作）最终将能够评估微 PF 模式与现场规模 PF 路径的重要性，以阐明触发微生物热点空间模式的机制。