Root water potential explains logarithmic variations of soil matric potential

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4. Root water potential explains logarithmic variations of soil matric potential

Changes in soil matric suction (or matric potential; y_s) due to plant transpiration affect shallow soil stability. Understanding water transport within the soil-plant-atmosphere continuum (SPAC) is the key to quantify the transpiration-induced changes in y_s, but this is often challenging due to the difficulties in measuring water potential in all components of the SPAC. Handheld tools are readily available to measure leaf water potential (y_l), but they only partially explain variations in y_s. Although root water potential (y_r) is known to be much more closely associated with y_s, data on y_r is very scarce. This study presents findings obtained from soil columns cultivated with vetiver grass (Chrysopogon zizanoides L.). The vegetated columns were subjected to a drought period typical to a tropical climate region, during which various water potential terms, including y_s and y_r, as well as relevant root traits, were measured to understand water transport in this SPAC. Our findings showed a logarithmic increase in the gradient between y_s and y_r. Specific leaf area significantly decreased with y_r, indicating hydraulic continuity between roots and leaves. We propose a new power-law correlation between root diameter and y_r to facilitate a trait-based understanding of root water uptake.

3rd International Workshop on Soil-Vegetation-Atmosphere Interaction (RootS2025)

1a. Experimental characterisation of thermo-hydraulic properties of the rooted soils