Micromechanics of root growth and physical habitat properties in the rhizosphere

根际形成了一个自组织系统，具有众多的物理，生物和化学相互作用。由于这种相互作用，出现了增加植物对干旱或机械土壤阻抗等限制性环境条件的适应性的特性。在根际，微观力学性质发挥了重要作用，但尚未深入研究与土壤植物相互作用（如。粘液渗出）。这些特性对土壤结构的时空发展至关重要，从而与生物过程相结合，影响土壤功能和植物发育，进而改变土壤结构。在第一阶段工作的基础上，我们现在正在研究在现场和受控实验室条件下机械性能的发展，重点是与根系发育和土壤结构形成有关的机械过程，包括孔隙尺度微生物栖息地的物理特性。为此，我们将采集未受干扰的土壤样本，并进行现场测量。在实验室中，我们将仔细研究渗透阻力及其对根系形成的影响。另一方面，我们将调查的是根分解过程中的孔隙空间的发展和相关的变化聚集特性。为了表征微生物栖息地，我们将研究氧化还原电位和局部氧浓度的动态，以及使用成像和机械技术研究聚集体。土壤力学性质的测定将采用新研制的土壤固结仪、实验室叶片探针、材料试验机和野外微型土工试验仪。结果将纳入项目伙伴的建模方法（与FZ Jülich合作）。此外，我们将与UFZ Halle合作，将这些数据与根长密度和半径联系起来。作为成像技术，我们将应用X射线计算机断层扫描和定量图像分析与ToolIP。O2-浓度和氧化还原电位将用微传感器原位测量。收集的数据用于验证有效扩散系数模型（与埃尔兰根纽伦堡大学合作）。对于我们的骨料稳定性测量，我们将使用湿筛分方法和最近开发的干粉碎方法。在与Thünen研究所的合作中，我们将研究土壤团聚体的微观结构和稳定性，并描述物理栖息地条件及其与微生物多样性的关系。

The rhizosphere forms a self-organised system with a multitude of physical, biological, and chemical interactions. Resulting from this interplay, properties emerge that increase the resilience of plant against limiting environmental conditions such as drought or mechanical soil impedence. In the rhizosphere, micro-mechanical properties play an important role but have not been intensely studied in connection with soil plant-interactions (eg. mucilage exsudation). These properties are crucial for the temporal and spatial development of soil structure, thus affecting – combined with biological processes – soil functions and plant development, which in turn alter soil structure. Building on the work of phase I we are now investigating the development of mechanical properties in the field and under controlled laboratory conditions with a focus on mechanical processes in relation to root development and soil structure formation including the physical characterisation of pore scale microbial habitats. To this end, we will take undisturbed soil samples and perform in-situ measurements. In the laboratory, we will take a close look at penetration resistance and its effect on the formation of the root system. Another aspect we will investigate is the pore space development during root decomposition and related changes in aggregate characteristics. To characterize the microbial habitat, we will examine the dynamics of redox potentials and local oxygen concentrations, as well as investigate aggregates using imaging and mechanical techniques. Soil mechanical properties will be measured oedometers, a laboratory vane probe, a material testing machine and a field micro penetrometer which will be newly developed. Results will be incorporated into the modelling approaches of project partners (cooperation with FZ Jülich). Furthermore, we will relate these data to root length densities and radii in cooperation with the UFZ Halle. As imaging techniques, we will apply X-ray computed tomography and quantitative image analysis with ToolIP. O2-concentrations and redox potentials will be measured in-situ with microsensors. The data collected are used to validate a model for effective diffusion coefficients (cooperation with the University of Erlangen Nuremberg). For our aggregate stability measurements, we will use a wet sieving approach and a recently developed dry-crushing method. In a cooperation with the Thünen-Institute we will investigate microstructure and stability of soil aggregates and characterize the physical habitat conditions and their relation to microbial diversity.