Yahel Eliyahu-Yakir

This paper investigates the development of azimuthal root asymmetry in riparian plant cuttings as a response to hydrodynamic forces, a novel tropism response that we refer to as “dynamotropism.” Laboratory experiments were performed within an experimental flume using Salix fragilis cuttings growing in rhizoboxes filled with quartz sand and undergoing different treatment conditions. These aimed to isolate and differentiate the effects that hydrodynamic forces acting on the stem exert on the root vertical biomass development from that of hyporheic flow. Results reveal that in response to an applied external (drag) force acting on the stem, root biomass increases significantly in the upstream direction, opposite the drag force, resulting in approximately 30% greater total biomass upstream than downstream. This suggests a structural adaptation of the below‐ground biomass to resist mechanical loading of the aboveground part of the cutting. While the effect of force seems to influence overall root production, the effect of hyporheic flow does not affect the total biomass in either directions. Hyporheic flow, in particular, tends to enhance root growth toward the downstream side at higher depth than in the top soil layers. Hence, flow and force appear to promote opposing patterns of root development along the sediment depth, whose evidence is maximized when both stimuli are applied simultaneously. When acting together, the relative magnitudes of such stimuli become crucial in determining the final root architecture where mechanical force dominated over flow stimulus. The results of this work path the way to novel plant nursing strategies for bioengineering applications.

In this work, we present a sequential procedure to analyze non-destructive neutron scattering imaging, which allows to improve the signal-to-noise ratio and maximize the identification of root structure architecture of plant cuttings grown in rhizoboxes containing humid sand sediment.Plant cuttings play a pivotal role in water bioengineering applications, contributing significantly to enhancing waterway ecohydraulic processes, ecomorphodynamic mechanisms, flood protection strategies, and river restoration techniques. Despite their crucial role, various dynamics related to in-channel and bank vegetation responses to hydromechanical forces remain insufficiently understood. In this study, we conducted flume experiments to systematically examine the impact of hydrodynamic forces and subsurface flow on the root structure development of riparian plant cuttings (Salix species). Specifically, we addressed to role of such actions on triggering dynamotropism and hydropatterning mechanisms, which both lead to (upstream) asymmetrical plant root growth and spatially-variable soil reinforcement. The plant cuttings were cultivated in rhizoboxes filled with sand, which did undergo four different treatments aiming at single out which one better controls dynamotropism and hydropatterning. After a 6-week growth period, we employed a Neutron scanner to scan the boxes and detect the intricate root structures non-destructively. Analysis of the scans revealed significant challenges in distinguishing roots from the background due to factors such as the remaining water content at the pore level, sand texture, and variations in root dimensions. The high spatial variability of these parameters significantly influenced the accuracy of root detection. To address these challenges, we have developed a process utilizing advanced tools to enhance the probability of successfully detecting roots within the sand matrix. The automatization of such a procedure will allow to non-destructively analyse a large number of samples for statistically significant correlation analyses.

Miscible multiphase flow in porous media is a key phenomenon in various industrial and natural processes, such as hydrogen storage and geological carbon sequestration. However, the parameters controlling the patterns of displacement and mixing in these flows are not completely resolved. This study delves into the effects of heterogeneity and inlet pressure on mixing and displacement patterns of low-viscosity miscible phase invasion into a high-viscosity resident phase, that is saturating a porous medium. The findings highlight the substantial influence of inlet pressures and heterogeneity levels in transitioning from uniform to fingering patterns at the pore scale. These phenomena are detectable at the Darcy scale, and their transition from a uniform front to finger formation is effectively marked through a modified Sherwood number. This modified Sherwood number links microscale patterns to physical properties such as velocity distribution, diffusion, and viscosity contrasts. Additionally, the study employs breakthrough curve (BTC) analysis to illustrate the role of higher heterogeneity and inlet pressure in broadening the fluid velocity distribution, leading to the fingering pattern. These research insights provide a nondimensional approach that scales the BTCs, and can serve future models of miscible phase flow in porous media, linking pore-scale dynamics with macroscale Darcy-scale observations.