Water uptake and hydraulic redistribution under a seasonal climate: long-term study in a rainfed olive orchard

Hydraulic redistribution plays a relevant role in the water relations of trees in climates with alternation between warm/dry and cold/wet periods. We aim to illustrate the ability of Mediterranean deep-rooted rainfed olive trees to maintain transpiration during the hot dry season and to redistribute soil water through roots, tending to temporarily homogenize soil moisture vertically. Sap flow was monitored by the heat field deformation method for 25years in the stem, lignotuber, medium and shallow roots of an olive tree tracing the long-term variations in the patterns of transpiration, water uptake and hydraulic redistribution. During the same period, soil water content and meteorological data were measured and related to sap flow. Results show that hydraulic redistribution within the rhizosphere buffers the seasonal and long-term water deficits. Under high evaporative demand during the dry summer, the deeper roots connected to stem through the lignotuber uptake water supporting transpiration needs and reducing the intensive drying of the upper soil layers. Copyright (c) 2014 John Wiley & Sons, Ltd.