Experimental investigation of the microscopic interaction mechanism between sand and tall fescue roots by using X-ray microtomography

This study aimed to enhance the understanding of root–soil interaction at a microscale level and its implications for practical land management, ecosystem restoration, and engineered solutions on vegetated slopes. Specifically, the interaction between tall fescue roots and sand was investigated using four-dimensional (4D) CT scanning. The growth process of tall fescue roots in sand was tracked on the 2nd, 4th, 6th, and 8th days after seed transplantation. To accurately segment root–soil CT images and overcome challenges such as the partial volume effect (PVE) and the similarity of root water grayscale in CT images, a semiautomatic segmentation process was employed. The analysis focused on examining the evolution of three-dimensional root parameters throughout the growth process. The findings highlighted the significant influence of initial porosity on tall fescue root development, the global decrease in saturation with root growth, and the predominant impact of pore distribution on local saturation distribution. The study revealed that the root system's influence on saturation, on the eighth day after transplantation, extended up to 800 pixels (8 mm) from the root surface. These results have practical implications for optimizing planting density and providing effective planting strategies for vegetated slope design in engineering applications.