Water as medium for nutrient distribution: Monitoring water distribution between subsoil and topsoil considering roles of biopores and plants, by MRT and pressure probes (WatMed)

用于CeMiX的微型土芯（200 mm Ø）上的磁共振断层扫描（MRT），包括自然堆积的底土至700 mm，加上CeFiT的表土，将在横向部分打开的Split 1.5 T磁铁上实施，最终平面内空间分辨率为200 μm。三维生物孔分布及其在岩心内形成的动态将被非侵入性地确定，并与SP 2的补充CT分析进行比较。一个主要目标是基于核磁共振弛豫参数，将生物孔非侵入性地分化为由蚯蚓和根系产生的孔，以及目前由空气、水、根和蚯蚓填充的孔。此外，还将尝试根据其亲水性对生物孔的不同壁涂层进行分类。从CeFiT （SP 3）的初始值开始，将以5毫米的平面内分辨率记录微观世界核心及其生物孔结构内的水分布动态，同时测量根系生长动态以计算生物量和根表面积。将特别强调植物根系在不同土层之间重新分配水/D2O（和溶质）的作用。最后，我们将尝试从微观世界的核心中收集mrt控制的样本，与我们在SPs 4-8的研究单位合作伙伴一起，反复访问微创获取的营养和微生物分布数据，以及非侵入性收集的水和根分布数据，作为SP 10中水和溶质循环动态建模的基础。除了微型核心外，SP 3中使用的扁平根管将用于测量根和茎的静水压力曲线，以及MRT测量。通过这种方式，水的分布以及相应的驱动力和生长动态将以一种微创的方式进行测量。

Magnetic resonance tomography (MRT) on microcosm soil cores (200 mm Ø) used for CeMiX, comprising naturally stacked subsoil down to 700 mm plus topsoil from CeFiT, will be implemented at a laterally partially open Split 1.5 T magnet, with intended final in-plane spatial resolution of 200 μm. Three-dimensional biopore distributions and dynamics of their formation within the cores will be determined non-invasively and compared to complementing CT analyses of SP 2. One major aim is a non-invasive differentiation of the biopores into earthworm- and root system-originating ones and currently air-, water-, root- and earthwormfilled ones, based on NMR relaxation parameters. Attempts will additionally be made to classify different wall coatings of the biopores with regard to their water affinity. Dynamics of water distribution within the microcosm core and its biopore structures, starting from initial values taken from CeFiT (SP 3), will be documented with an in-plane resolution of 5 mm, in parallel to measurements of root growth dynamics for calculation of biomass and root surface area. Special emphasis will be put on the role of the plant root system for a re-distribution of water/D2O (and solutes) between different soil layers. Finally we will attempt MRT-controlled sample collection from the microcosm cores, to get – together with our research unit partners of SPs 4-8 – repeated access to minimally invasively acquired data on nutrient and microorganism distributions in concert with non-invasively collected water and root distribution data as a basis for dynamic modelling of water and solute circuits in SP 10. Beside the microcosm cores, flat rhizotrons as used in SP 3 will be employed to enable measurements of root and shoot hydrostatic pressure profiles with pressure probes, in addition to MRT measurements. In this way water distributions and corresponding driving forces and growth dynamics will be measured altogether in a minimally invasive manner.