Can root systems redistribute soil water to mitigate the effects of drought?

Plants adapt both morphologically and physiologically in response to drought. This work considers another potential mechanism of plant drought resistance. Namely, the capacity of root systems to modify the hydraulic properties of surrounding soil, and extend the post-precipitation lifetime of water in the rooted zone. In studies of plant drought resistance, the effect of root-oriented preferential soil water transport is seldom considered, despite experimental evidence that it occurs. We developed a model for water transport through soil that incorporates preferential flow induced by a root system. Bayesian optimisation was employed to calibrate the model against experimental data, and the finite element method was used to obtain model simulations for the influence of different root architectures on post-precipitation water lifetime. When increasing preferential flow strength, simulations indicated a trade-off between evaporation and deep percolation losses. It was also observed that the soil surrounding root systems with a reduced gravitropic response, retained the most water following precipitation. This work provides new insight into the role of root system traits in plant drought resistance, and identifies potential crop phenotypes for improved water use efficiency.