Hydraulic lift among native plant species in the Mojave Desert

Hydraulic lift was investigated among native plants in the Mojave Desert us ing in situ thermocouple psychrometers. Night lighting and day shading expe riments were used to verify the phenomenon. Hydraulic lift was detected for all species examined: five shrub species with different rooting depths and leaf phenologies and one perennial grass species. This study was the first to document hydraulic lift for a CAM species, Yucca schidigera. The patter n of diel flux in soil water potential for the CAM species was temporally o pposite to that of C-3 species: for the CAM plant, soil water potential inc reased in shallow soils during the day when the plant was not transpiring a nd decreased at night when transpiration began. Because CAM plants transpor t water to shallow soils during the day when surrounding C-3 and C-4 plants transpire, CAM species that hydraulically lift water may influence water r elations of surrounding species to a greater extent than hydraulically lift ing C-3 or C-4 species. A strong, negative relationship between the percent sand in the study site soils at the 0.35 m soil depth and the frequency th at hydraulic lift was observed at that depth suggests that the occurrence o f hydraulic lift is negatively influenced by coarse-textured soils, perhaps due to less root-soil contact in sandy soils relative to finer-textured so ils. Differences in soil texture among study sites may explain, in part, di fferences in the frequency that hydraulic lift was detected among these spe cies. Further investigations are needed to elucidate species versus soil te xture effects on hydraulic lift.