New concepts for assessing soil structure turnover by structure labeling and analyses of biochemical gradients

通过结构标记和生化梯度分析评估土壤结构周转的新概念

• 批准号: 416883305
• 负责人: Professorin Dr. Eva Lehndorff
• 金额: --
• 依托单位: Professur für Bodenkunde und Bodenschutz
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/416883305?language=en
• 关键词: New; concepts; assessing; soil; structure

Soil structure is the manifestation of the interactions of many biotic and abiotic agents in soil and controls many soil functions such as matter turnover, water retention, and the production of biomass. Soil structure has been identified to govern long-term carbon sequestration in soil via physical protection of soil organic matter against decay, therewith possessing a central role in the global carbon cycle. Soil structure is often considered static but actually changes due to bioturbation, wetting/drying, freezing/thawing and tillage activities. Yet, conceptual approaches to link soil structure turnover to organic matter decomposition are still in their infancy, mainly due to methodological shortcomings that impair meaningful estimates of soil structure turnover rates. The main objective of this project is to establish novel conceptual approaches to measure soil structure turnover under natural conditions. The first is based on structure labeling where soil aggregates are coated with small inert garnet particles and their fate is studied using X-ray microtomography (µCT). The speed at which randomization with respect to particle‒pore distances is achieved will be interpreted as turnover rate. The second is based on the detection of microscopic biochemical gradients. They are expected to form when soil structure turnover is slow, whereas fast soil structure turnover continuously changes diffusion pathways and redistributes constituents, thus preventing the formation of biogeochemical gradients. In this project we focus on imaging methods that provide a comprehensive in-situ view to undisturbed soil structure. Two-dimensional microscopic and microspectroscopic data (XPS, SEM-EDS, LA-IRMS) are merged with three-dimensional physical structure (µCT) through 2D-3D image registration in order to truly link 3D diffusion pathways to spatial gradients in element ratios, carbon oxidation states, and carbon isotope ratios. The proposed approaches will be tested in laboratory and field experiments to identify abiotic (wetting, freezing) and biotic (microbial activity, bioturbation) drivers of soil structure turnover. Long-term vegetation change experiments with known carbon turnover rates are revisited to estimate soil structure turnover from the magnitude of biochemical gradients. With this project we expect novel insights into the mechanisms of soil structure formation under natural conditions and how altered pore size domains and biochemical gradients are linked to the cycling of soil organic matter.

土壤结构是土壤中多种生物和非生物物质相互作用的表现形式，它控制着土壤的许多功能，如物质周转、保水和生物量的生产。土壤结构通过对土壤有机质的物理保护防止土壤腐烂，从而在全球碳循环中具有核心作用，从而控制土壤中的长期碳固定。土壤结构通常被认为是静态的，但实际上由于生物扰动、湿/干、冻结/融化和耕作活动而发生变化。然而，将土壤结构周转与有机质分解联系起来的概念性方法仍处于初级阶段，主要是由于方法上的缺陷，这损害了对土壤结构周转速率的有意义的估计。该项目的主要目标是建立新的概念性方法来测量自然条件下的土壤结构周转。第一种是基于结构标记法，在土壤团聚体上覆盖一层小的惰性石榴石颗粒，并用X射线显微断层摄影术(µCT)研究它们的命运。关于颗粒-孔隙距离实现随机化的速度将被解释为周转率。第二种是基于微观生化梯度的检测。它们预计在土壤结构周转缓慢时形成，而快速土壤结构周转不断改变扩散路径并重新分配组分，从而防止生物地球化学梯度的形成。在这个项目中，我们专注于提供对未受干扰的土壤结构进行全面原位观察的成像方法。通过2D-3D图像配准，将二维显微和显微光谱数据(XPS、SEM-EDS、LA-IRMS)与三维物理结构(µCT)合并，以便真正将3D扩散路径与元素比率、碳氧化态和碳同位素比率的空间梯度联系起来。建议的方法将在实验室和田间试验中进行测试，以确定土壤结构周转的非生物(湿润、冻结)和生物(微生物活动、生物扰动)驱动因素。已知碳周转率的长期植被变化实验被重新考察，以从生化梯度的大小来估计土壤结构周转率。通过这个项目，我们期待着对自然条件下土壤结构形成的机制以及改变的孔隙大小区域和生化梯度如何与土壤有机质的循环有关的新见解。