Small scaled and dynamic analysis of microstructural rhizo- and drilosphere properties: porosity,physicochemistry and their role for root growth, nutrient storage and transport/support

该项目的研究是基于以前的研究单位FOR 1320，其中不同的前茬作物和作物序列对特征生物孔系统的发展及其在底土中的功能特性的影响进行了调查。利用x射线计算机微断层扫描和图像分析对孔隙网络结构进行无创量化。这些结果强调了生物孔通过支持更深的生根对水和空气供应的重要性。结果表明，蚯蚓和根产生的生物孔在微观尺度上存在明显差异，特别是在生物孔与土体的界面（孔壁）上。先前堵塞的孔隙例如恢复了连续性，而在其他孔隙中蚯蚓浇铸成内衬和/或堵塞了先前由次生根形成的孔隙或截短的侧向通道。孔壁特性在多大程度上影响土壤和孔之间通过根际圈的空气和水以及营养物质的转移仍然是未知的。首先对微尺度气体扩散进行了测量，结果表明，由于存在大量的横向通道，根诱导孔比蠕虫诱导孔更适合空气输送。另一方面，蠕虫诱导的孔隙可能会导致疏水孔壁，因为有根和/或蠕虫渗出物内衬，这将导致更稳定的水结构，但也减少了侧向水输送。在这个项目中，设想用一种组合方法（StrucDyn/Kassel和RhizPhy/Kiel）对孔壁特性进行详细分析，包括生物孔网络的结构和微观形态（StrucDyn）以及孔壁的物理化学、物理和化学方面（RhizPhy）。StrucDyn将研究单个生物孔的非侵入性结构，包括孔壁和根际孔空间的形态，这取决于孔的起源/定植（蠕虫或根）以及由于生物孔的老化。形态学图像分析和数字图像相关将用于检测孔隙修饰。孔壁特性，如实际疏水性（驱避性）、水的可转移性（吸附性、微渗透）和空气的可转移性（氧扩散、氧化还原电位）以及微力学特性（微渗透、流变学）将由RhizPhy在完整孔壁、根和蠕虫渗出物以及生物模型物质上确定。StrucDyn和RhizPhy获得的数据将用于参数化和进一步开发根系生长模型（RootMod），以研究根际微结构和水力/力学特性对根系发育和水分和养分吸收的影响。

The research of this project is based on the former research unit FOR 1320 where the effect of different preceding crops and crop sequences on the development of characteristic biopore systems and their functional properties in the subsoil was investigated. Pore network architectures were quantified non-invasively using X-ray computed microtomography and image analysis. The results underline the importance of biopores for water and air supply by supporting deeper rooting. It was found that earthworm and root generated biopores were distinctly different at the microscale, especially at the interface between biopore and bulk soil (pore wall). Previously blocked pores e. g. regained continuity, whereas in other pores earthworm cast lined and/or blocked the pores or truncated lateral channels previously formed by secondary roots. To what extent the pore wall properties influence the transfer of air and water as well as nutrients between bulk soil and the pore through the rhizodrilosphere is still unknown. First measurements on microscale gas diffusion revealed that root-induced pores are more suitable for air transport than worm-induced pores due the large amount of lateral channels. On the other hand, worm-induced pores might result in hydrophobic pore walls due to the lining with root and/or worm exudates that will lead to more water-stable structures but also reduce lateral water transport. In this project a detailed analysis of the pore wall properties is envisaged in a combined approach (StrucDyn/Kassel, and RhizPhy/Kiel) including both the structure and micromorphology of the biopore network (StrucDyn) and the physicochemical, physical and chemical aspects of the pore wall (RhizPhy). StrucDyn will investigate non-invasively the architecture of single biopores including the morphologies of the pore wall and rhizodrilosphere pore space depending on the pore origin/colonization (worm or root) as well as due to biopore aging. Morphological image analysis and digital image correlation will be utilized to detected pore modifications. Pore wall properties such as actual hydrophobicity (repellency), the transferability of water (sorptivity, microinfiltration) and air (oxygen diffusion, redox potential) as well as micromechanical properties (micropenetration, rheomtry) will be determined by RhizPhy on both intact pore walls and root and worm exudates as well as biological model substances. The obtained data from StrucDyn and RhizPhy will be used to parameterize and further develop a root growth model (RootMod) in order to investigate the effect of microstructural and hydraulic/mechanical properties of the rhizodrilosphere on root development and water and nutrient uptake.