Hydraulic lift (HL) is the passive movement of water through the roots from deep wet to dry shallow soil layers when stomata are closed. HL has been shown in different ecosystems and species, and it depends on plant physiology and soil properties. In this study we explored HL patterns in several arid land shrubs, and developed a simple model to simulate the temporal evolution and magnitude of HL during a soil drying cycle under relatively stable climatic conditions. This model was then used to evaluate the influence of soil texture on the quantity of water lifted by shrubs in different soil types. We conducted transpiration suppression experiments during spring 2005 in Chile and spring 2008 in Spain on five shrub species that performed HL, Flourensia thurifera, Senna cumingii and Pleocarphus revolutus (Chile), Retama sphaerocarpa and Artemisia barrelieri (Spain). Shrubs were covered with a black, opaque plastic fabric for a period of 48-72 h, and soil water potential was recorded at different depths under the shrubs. While the shrubs remained covered, water potential continuously increased in shallow soil layers until the cover was removed. The model output indicated that the amount of water lifted by shrubs is heavily dependent on soil texture, as shrubs growing in loamy soils redistributed up to 3.6 times more water than shrubs growing on sandy soils. This could be an important consideration for species growing in soils with different textures, as their ability to perform HL would be context dependent.
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Acknowledgments We would like to thank Albert Solé for his help with the soil moisture release curve and Cristina Armas, Michele Faisey, Francisco M. Padilla, and two anonymous reviewers for helpful comments on the manuscript. This work was supported by FONDECYT (1071012), Compañía Minera del Pacífico (CMP), Chilean Millenium Iniciative (ICM P02-051) and CONICYT (PFB-23) grants in Chile, and the Spanish Ministry of Science and Innovation (grants CGL2004-0355-E and CGL2007-63718) in Spain. The experiments described here comply with the current laws of the countries in which they were performed.