On a better understanding of hydraulic lift: A numerical study

Abstract

Hydraulic lift is the transport of water from moist into drier soil layers through plant root systems: Plant roots sometimes do not only take up water but also release water if the soil is dry. Hydraulic lift has been shown for a relatively small number of species, but it is believed to be a more general phenomenon: We model numerically water uptake and two-dimensional water transport through the soil and through the root system as coupled processes. Both water uptake and transport through the root system are considered to be hydraulic processes; osmotic effects are neglected. The model is capable of tracing hydraulic lift; the simulated amount of shifted water is consistent with experimental data. This supports the theory that hydraulic lift is a pure hydraulic process without an osmotic component. Furthermore, we discuss how far hydraulic lift could be an optimized strategy for the plant.