What drives water movement between lateral roots?
Hydraulic redistribution in any form requires that a root system span soil layers (or compartments/patches) of different water potential. Our simple survey of soil moisture contents on different sides of a single tree demonstrated that considerable variability in water contents (and by inference soil water potentials) of the upper soil layers is possible, and this variability was in agreement with the direction of hydraulic redistribution observed here. The reasons for soil moisture variability around single trees remain unclear, but may include rain shadows, patches of non-wetting soil, or varying soil textures. Soils in this region typically exhibit strong texture contrasts from the A to B horizon and variable subsurface relief (Tennant et al., 1992) can alter at what depth a wetting front encounters heavy subsoils. During excavations, pockets of extremely dry soil were often encountered even after months of heavy winter rain. In addition to soil variability, lateral rooting depth ma
