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

本项目的研究是在原1320研究单元的基础上进行的，研究了不同前茬作物和作物序列对底土生物矿化系统发育及其功能性质的影响。利用X射线计算机显微断层扫描和图像分析对孔隙网络结构进行了非侵入性的量化。这些结果强调了通过支持更深的生根，生物孔对供水和空气供应的重要性。研究发现，蚯蚓和根生生物孔在微观尺度上有明显的不同，尤其是在生物孔与土壤之间的界面(孔壁)。以前堵塞的毛孔例如恢复了连续性，而在其他毛孔中，蚯蚓浇注了衬里和/或堵塞了毛孔或截断了先前由次生根形成的横向通道。孔壁的性质在多大程度上影响了土壤和根际土壤之间的空气、水分和营养物质的迁移，目前尚不清楚。首先，微尺度气体扩散测量表明，由于有大量的侧向通道，根诱导的气孔比蠕虫诱导的气孔更适合空气传输。另一方面，蠕虫诱导的气孔可能会导致疏水孔壁，因为衬里有根和/或蠕虫分泌物，这将导致更稳定的结构，但也会减少侧向水分传输。在本项目中，设想采用组合方法(StrucDyn/Kassel和RhizPhy/Kiel)对孔壁特性进行详细分析，包括生物孔网络结构和微形态(StrucDyn)以及孔壁的物理化学、物理和化学方面(RhizPhy)。StrucDyn将非侵入性地研究单个生物孔的结构，包括孔壁和根际孔隙空间的形态，这取决于孔的来源/定植(蠕虫或根)以及由于生物孔老化造成的。将利用形态图像分析和数字图像相关来检测孔洞修饰。完整的孔壁、根和蠕虫分泌物以及生物模型物质上的实际疏水性(排斥性)、水的传递性(吸水性、微渗透)和空气的传递性(氧扩散、氧化还原电位)以及微观机械性能(微渗透、流变性)将由RhizPhy决定。从StrucDyn和RhizPhy获得的数据将被用来参数化和进一步发展根生长模型(RootMod)，以研究根际微结构和水力/力学特性对根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.